Proceedings of the 3rd Pan American Materials Congress

An absorbable suture clip (MU9102934-1) for surgical applications was designed based on the bite mechanism of ant Atta laevigata. In order to emulate the behavior of the ant mandible, the clip was designed to naturally fall after some time, relieving the inconvenience of the clip removal process. The structure consists of a metallic handle and an absorbable polymeric tip. This study aims to optimize its geometry and select the best biomaterials to the handle structure, by analyzing its mechanical performance using the finite element method (FEM). The biomaterials selected for the simulations of the handle were AISI 316L and AISI 420 stainless steels. FEM analysis was performed using ANSYS FE software. The stress and strain distributions for each material and geometry changes were analyzed. From the analysis performed, the clip was optimized in order to be applied in a less traumatic form.

Bioactive glasses (BG) are a group of inorganic materials widely used in Bone Tissue Engineering (BTE). These biomaterials react with body fluids resulting in the formation of bone like apatite layer. In this study, sol-gel derived bioactive glass was synthesized in the SiO₂-CaO-P₂O₅ system according to augmented constrained mixture experimental design, with percentage restrictions for each oxide as follows: 58 ≤ SiO₂ ≤ 70; 6 ≤ P₂O₅ ≤ 9 and 24 ≤ CaO ≤ 34. BG were conformed into short-bulk cylinders and immersed in Simulated Body Fluid (SBF) solution for 7 and 14 days in order to carry out bioactivity tests. Apatite layer formation was confirmed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Analysis (EDX). The results showed apatite layer formation depended on BG chemical composition proved with p-values from ANOVA analysis below 0.05 indicating factors significance over the response. The formed apatite layer presented a Ca/P ratio similar to bone apatite, this result is appropriate for biomaterials used in BTE.

This paper investigates the effects of Dialium guineense based zinc nanoparticle material on the inhibition of microbes inducing microbiologically influenced corrosion (MIC) in metals. Extract of leaf from the natural plant were used as precursor for zinc nanoparticle material, which was characterized by scanning electron microscopy and energy dispersive spectroscopy (SEM + EDS) instrument. Sensitivity of the developed zinc bio-nanoparticle material from this on different strains of microbes that are known to induce microbiologically influenced corrosion, in metallic materials, was then studied and compared with that obtained from a commercial antibiotic employed as control. Results showed that the biomaterial capped nanoparticle exhibited inhibited growth of the studied different MIC inducing microbes. Zones of inhibition, the sensitivity measure of the biosynthesized material against the microbial strains either surpassed or compared well with the zones of inhibition from the commercial antibiotic (control). These results engender implication on the prospects of the zinc bio-nanoparticle usages in corrosion inhibition and protection system for metals in microbial corrosion influencing environment.

The first injectable bone substitutes were introduced for orthopedic trauma applications since more than a decade, and over recent years the number of commercial products has dramatically increased. These substitutes can be injected into a fracture space for augmentation as an alternative to bone graft, or around a screw for augmentation if the bone is weak, so the injectability of the substitute must be optimum with a good behavior within and our of syringe. The aim of this work was to study the injectability of substitutes based on carrageenan CG with 1, 1.5, 2.5 and 60 wt% hydroxyapatite HA nanorods. Initially carrageenan and hydroxyapatite were characterized and then injectability tests were performed with the syringe between the compression plates of a testing machine. The material also was characterized by scanning electron microscopy. The results revealed that none of the samples had phases separation and they did not exceed 300 N of force (97.08, 107.84 and 149 N to each material), that the injectability was 95.71, 93.69 and 90.63% and the CG was a good vehicle for HA nanorods. Therefore, the substitutes are adequate for manual handling.

Ni_0.5Zn_0.5Fe₂O₄@mesoporousSiO₂ (NZF@mSiO₂) core shell nanocarrier was synthesized by sol–gel method using tetraethyl orthosilicate (TEOS) and cetyltrimethylammonium bromide (CTAB) and characterized for different physicochemical properties. The structural and morphological properties were studied by X-ray powder diffraction (XRD), transmission electron microscope (TEM), and field emission scanning electron microscope (FESEM) techniques. XRD pattern and TEM micrographs confirm the coexistence of Ni_0.5Zn_0.5Fe₂O₄ and SiO₂ phases in the nanocomposites. Average crystallite size of Ni_0.5Zn_0.5Fe₂O₄ NPs was found to be around ~21 nm. Particles size of NZF@mSiO₂ measured by TEM and FESEM are found to be ~200–400 nm. High-resolution transmission electron microscopy (HRTEM) results confirm successful formation of NZF@mSiO₂ core shell nanocomposites having well symmetric structure and ellipsoidal shape. HRTEM analysis confirmed the presence of pores (5–10 nm) on the surface of SiO₂ nanosphere. Magnetic properties of NZF@mSiO₂ nanocarriers were studied by vibrating sample magnetometer (VSM) technique. NZF@mSiO₂ nanocarriers were found to be super-paramagnetic in nature with negligible coercivity and remanent magnetization. The M_s value for NZF@mSiO₂ was found to be 9.5 emu/gm.

Amorphous hydrogenated carbon (DLC) coatings have a high hardness depending on the relative amount of sp3/sp2 bondings. They also exhibit an extremely low friction coefficient and are chemically inert. However, these coatings have some disadvantages which limit their applications. For instance, adhesion is poor when they are deposited on metallic substrates and they are also unstable at high temperatures, degrading into graphite and loosing hardness. In this work, DLC coatings were deposited on precipitation hardening stainless steel (PH Corrax) which was plasma nitrided before the coating deposition. The samples were submitted to annealing treatments for an hour at different temperatures from 200 to 600 °C, together with a control group, which was only coated but not nitrided. After each annealing cycle, Raman Spectroscopy, nanoindentation and microscopy were used to check film properties. It was demonstrated that the nitriding pre treatment improved not only adhesion but also the thermal stability of the DLC, slowing degradation and preventing delamination.

Synthetic fibers have been used for many years to attend the demands required by the most technological fields, but their use have been questioned due to the impact of them on the environment. In this way, the natural fibers have received considerable attention because of some their characteristics, besides low cost, they are flexible, viable, renewable and considered abundant substitutes. Thus, this paper is about curaua fibers, which belong to the family Bromeliaceae and it intends to compare the mechanical strength between epoxy composite reinforced with random short curaua fibers and aligned long curaua fibers. The results show that aligned long curaua has higher mechanical strength.

Micro-ultrasonic machining (micro-USM) is used to fabricate complex micro-features in brittle and hard materials. In micro-USM, both dimensional and form accuracy of machined component depend mainly on the shape of the tool. However, tool wear is an unavoidable phenomenon of this process, which affect the accuracy of micro-feature. The tool suffers by three types of wear (longitudinal, lateral and edge wear) in micro-USM. Accumulation of micro-chips and abrasives in the machining gap (between tool and workpiece) are the main reasons responsible for severe tool wear in micro-USM. This article reports on a new method named as rotary tool micro-USM to reduce tool wear. The rotary tool micro-USM involves abrasive slurry with providing simultaneous rotation and vibration to the tool. Rotation of the tool helped abrasives to replenish from the machining gap easily. Micro-channels were fabricated and characterized by using stereo microscope. From the results, it was found that rotary tool micro-USM resulted in very less tool wear and as a result of that micro-channels of better dimensional and form accuracy were developed.

To support the lightweighting aim in the automotive industry, High-Velocity Impact WeldingWelding (HVIW) can be used to join dissimilar metals. The manufacturing industry often relies on numerical simulations to reduce the number of trial-and-error iterations required during the process development to reduce costs. However, this can be difficult in high strain rate manufacturing processes where extremely high plastic strain regions develop. Thus, a traditional Lagrangian analysis is not able to accurately model the process due to excessive element distortion. In order to further understand the science behind HVIW processes and benefits of various numerical simulation methodologies, two methods were utilized to simulate Al/Fe bimetallic system which is of interest for the automotive industry. First, a Smoothed Particle Hydrodynamics (SPH) Smoothed Particle Hydrodynamics (SPH) model of two impacting plates was created. Using SPH method, metal jet emission was investigated which previously was impossible. The results then were compared with an Arbitrary Lagrangian-Eulerian (ALE) Arbitrary Lagrangian- Eulerian (ALE) method. Finally, the numerical results were compared with experimental tests using a Vaporizing Foil Actuator Welding process.

Selective Laser Sintering (SLS) is an additive manufacturing technique that enables final products to be processed without additional machining. SLS permits the fabrication of implants and scaffolds with complex geometry for biomedical applications. In this study, composite scaffolds of polyamide (PA2200) filled with particles of hydroxyapatite (HA) were fabricated using SLS. The microstructure and mechanical properties were characterized. The effects of SLS processing parameters, including particle content and laser power, were investigated. Particle content and laser energy play a key role in the final density and mechanical properties of the sintered components. This study demonstrated that HA-reinforced PA can be successfully manufactured by SLS with controlled porosity features.

The current work initially investigated the manganeseManganese removal by sorptionSorption in a recycled spent zeoliteSpent zeolite (faujasite) used in the oil industry. Equilibrium adsorption was described by the Langmuir isotherm (r2 > 0.99) with a maximum loading of 10.9 mg/g-zeolite. The performance of the spent zeolite was compared with that of limestoneLimestone (a low cost sorbent). In this latter case, equilibrium sorption was also modelled using the Langmuir isotherms with 1.03 mg/g-limestone as maximum uptake. Fixed-bedFixed-bed sorption on both materials was also studied and solid loadings increased with the aqueous metal concentration. The Thomas model was selected to describe the breakthrough curves and showed good correlation with the experimental data for both samples and indicated a maximum solid uptake of 0.33 mg/g-solid in faujasite and 0.03 mg/g in limestone.

Advanced rechargeable lithium batteries with high energy density are required as power sources for electric or modern storage systems. Solid-state batteries with non-flammable inorganic solid electrolytes are one candidate to replace the currently-used liquid electrolyte. In recent years, a novel class of inorganic ceramic solid electrolyte with garnet structure Li₇La₃Zr₂O₁₂, known as LLZO, has been developed, which has several superior advantages, such as high Li-ion conductivity, high chemical and electrochemical stability in air. However, Li-ion conductivity for LLZO solid electrolyte is still too low to be applied in the industry. In order to obtain high Li-ion conductivity of LLZO, the priority is to stabilize its cubic phase, because the conductivity of tetragonal phase is two orders of magnitude lower than that of the cubic phase. Previous studies indicated that elemental doping was an effective means to stabilize the cubic phase as well as increase the density of ceramic samples, especially with Al3+. It can not only substitutes the corresponding element in the lattice but also helps expel pores through low melting-point phase formed at grain boundaries, which leads to a good connection between the cubic grains. In addition, Mo (normally Mo6+) substitution for Zr4+ may lead to more Li vacancies in LLZO, which is beneficial to the enhancement of ionic conductivity. In this study, Mo6+ doped Li_6.5La₃Zr_1.75Mo_0.25O₁₂ (LLZM) solid electrolytes are successfully prepared via field assisted sintering technology (FAST). The effect of sintering temperature on the microstructure and lithium ionic conductivity is mainly investigated. The results show that pure cubic phase LLZM can be obtained at the range of temperatures from 1050 to 1150 °C for no more than 10 min. For the sample sintered at 1150 °C, a maximum relative density of >95% with a total ionic conductivity as high as 1.3 × 10−4 S cm−1 are obtained at room temperature. The change of ionic conductivity is ascribed to the smaller ionic size of Mo6+ (0.62 Å) to Zr4+ (0.72 Å). The higher valence of Mo6+ to Zr4+ can reduce the Li+ concentration and stabilize the cubic phase.

At present, expensive semiconductor grade silicon (SEG-Si) is used for the manufacture of cells to convert solar energy into electricity. This results in a high cost for photovoltaic electricity compared to electricity derived from conventional sources. The processing of inexpensive metallurgical silicon, or ferrosilicon alloys, is a potentially economical refining route to produce photovoltaic silicon. With phosphorus being one of the most difficult impurities to remove by conventional techniques, this project investigated the use of electromagnetic levitation for dephosphorization of silicon–iron alloy droplets exposed to hydrogen–argon gas mixtures. The effects of time, temperature, hydrogen partial pressure, iron content in the alloy, and initial phosphorus concentration were evaluated.

Many of the corrosion inhibitors in current use are expensive and toxic so the current trend is to study compounds that are environmentally friendly and efficient. Inhibitors are easy to use and they have the additional advantage that can be applied in situ and without causing significant disruption in the process. In the present work we investigate the influence of the aqueous extract of yerba mate as corrosion inhibitor of copper and aluminum in 0.5 M NaCl and 1 M HCl solutions, using different electrochemical techniques. The following inhibition efficiencies: 56% for copper in 0.5 M NaCl with 25% concentration of extract, 17% for copper in 1 M HCl with 5% concentration of extract, and 99% for aluminum in 0.5 M NaCl for 1% concentration of extract were obtained by potentiodynamic polarization.

The trend in the industry is aimed at developing sustainable processes thus the search for alternative fuels such as biofuels can be the best alternative to replace fossil fuels but they are not yet economically competitive. This research shows a chemical route for the synthesis of tetraammineplatinum (II) chloride saltTetraammineplatinum (II) chloride salt which needs several stages. Each one production step was evaluated through platinum determination by atomic absorption and their products were characterized by XRD, IR and XRF analyses. Taking into account that the overall yield to tetraammineplatinum (II) chloride was of 61% a pilot plant was proposed and evaluated. This salt is used in the preparation of precursors compounds for getting catalysts supported on structured pore size allowing impregnation of catalytic species and promote the transfer of materials triglyceride molecules, as well as the evaluation of the scaling up of this process to industrial scale.

Currently, low traffic roads in most countries are made up of unpaved roads; therefore, to increase the bearing capacity and durability of soils, using stabilizers such as lime and portland cement is required. In this paper, the results obtained from the addition of alternative binderAlternative binder materials based on industrial by products such as alkali activated coal ashes that work as soil stabilizers with sustainability criteria and are assessed through Life Cycle Assessment (LCA); this process is approached from the preparation, packaging and storage of binder material, its activation and finally the application in test sections obtaining unconfined compressive strengths of the order of 2 MPa; which represented an increase in resistance above 300% for the same soil without stabilization.

This paper studies anticorrosion and adsorption mechanism of Rhizophora mangle L. leaf-extract on steel-reinforcement in concrete immersed in 3.5% NaCl test-environment. Open circuit potential, macrocell current and corrosion rate measurements were obtained from steel-reinforced concrete samples, into which different concentrations of the leaf-extract was admixed during casting, and which were immersed in the saline/marine simulating-environment. Corrosion noise resistance was modelled as the ratio of standard deviation of the corrosion potential to the standard deviation of the corrosion current. Analyses of these test-results showed that the corrosion rate from linear polarization resistance exhibited very good correlation with the noise resistance model for the leaf-extract concentrations studied. Further analyses identified Rhizophora mangle L. leaf-extract concentration with excellent corrosion inhibition efficiency performance on steel-reinforcement. Also data of anticorrosion performance followed the Langmuir adsorption isotherm model, which indicated physisorption as the prevalent corrosion-protection mechanism by the Rhizophora mangle L. leaf-extract on steel-rebar in concrete immersed in the 3.5% NaCl, simulating saline/marine environment.

This paper investigates Cassia fistula leaf-extract effects on the inhibition of stainless-steel corrosion in 0.5 M HCl. Measurements of corrosion rate were obtained through linear sweep voltammetry (LSV) technique, at the ambient temperature of 28 °C from stainless-steel specimens immersed in the acidic medium, containing different Cassia fistula leaf-extract concentrations. Results showed that inhibition effectiveness on stainless-steel corrosion increases with increasing concentration of the leaf-extract. The 10 g/L Cassia fistula leaf-extract, the highest concentration of the leaf-extract employed in the study, exhibited optimal inhibition efficiency η = 88.46% on the corrosion of the stainless-steel metal. Adsorption isotherm modelling shows that the experimental data followed the Flory-Huggins isotherm with excellent model efficiency, r2 = 90.27%, and the Langmuir model with very good model efficiency, r2 = 78.83%. Other isotherm parameters indicate favourable adsorption and suggest physisorption as the prevalent mechanism of corrosion protection by the leaf-extract on stainless-steel in the acidic chloride environment.

In this paper, C₅H₁₁NO₂S (Methionine) effect on reinforcing-steel corrosion in concrete immersed in 0.5 M H₂SO₄, simulating industrial/microbial environment, was studied by electrochemical techniques of open circuit potential and corrosion rate. The corrosion test-data were subjected to statistical distribution and tests of significance analyses prescribed by ASTM G16-95 R04. From this, analyzed results showed that the corrosion rate test-data followed the Weibull more than the Normal while the corrosion potential test-data followed both distributions. In spite of these, both the corrosion potential and the corrosion rate models still find agreements in corrosion criteria classification for the tested samples. Samples with C₅H₁₁NO₂S admixture exhibited corrosion rate reductions compared to the control samples. By this, 0.25% C₅H₁₁NO₂S admixture (i.e. wt% cement) exhibited optimal inhibition efficiency, η = 87.95 ± 7.64%, on steel-rebar corrosion in the 0.5 M H₂SO₄-immersed concrete. Experimental data fitted Flory-Huggins adsorption isotherm that indicated physisorption as the prevailing mechanism of C₅H₁₁NO₂S corrosion-protection on the reinforcing-steel in the industrial/microbial simulating-environment.

The use of electric arc furnace slag (EAFS)Electric arc furnace slag (EAFS), a by-product of the steelmaking industry, as an aggregate in concrete has been demonstrated to be a good practice in its manufacture. Furthermore, the incorporation of fibersFibers in concrete provides a more ductile behavior, increasing their tenacity and load capacity, improving the flexotraction strength and controlling shrinkage cracking. The purpose of this research was to study the performance improvement by reinforcingReinforced concrete steel-slag concrete with metallic or synthetic fibers added in different amounts. Some of the properties evaluated were: consistency of freshly mixed concrete by Abrams cone, compressive strength, flexotraction strength and indirect tensile strength. The results show a substantial improvement of the performance of the steel-slag concrete when it is reinforced with fibers. It also fulfils the requirements of “depth of water penetration under pressure” test, even in the worst environmental exposure case.

The proposition of this paper is to introduce a sorting platform aiming to increase quality on recycled aggregates by supplementary use of mineral processing techniques and more sorting. The difficulty of liberation is discussed and the methodology currently used in mineral processing is proposed. Jigs, hydrocyclones and sensor-based sorting are equipments considered as having good performances to sort adequately recycled aggregates. On the other hand, new perspectives of sorting and liberation for recycling aggregates are discussed. Based on current process in recycling platforms, the new process with supplementary sorting of the concrete recycled is presented. The gain in density and the reduction in water absorption were studied. The relation between the water content and the density of aggregates is analysed for three quality levels of recycled aggregates. Finally, the gain in density and the reduction in water absorption were linked with rates of replaced aggregates. In our study, replacing a lower quality aggregate by another with medium quality leads an expected gain in density about 4%. On the other hand, if replaced by superior quality, the expected gain will be 8.4%. As consequence, 34% on reduction in water absorption could be obtained too.

Electric arc furnace slag (EAFS)Electric arc furnace slag (EAFS) has for many years simply been dumped in landfill sites; over the past few decades many researchers have investigated its reuse in cement mortar and concrete. By doing so, a waste product may be converted into a useful material with added value as a substitute for natural resources, the consumption of which is also minimized. Hydraulic mixes manufactured with EAFS normally have similar or even better hardened properties than mixes manufactured with natural aggregates. One disadvantage in the use of EAFS has been the poorer workabilityWorkability of the mixes, due to its higher density, porosity and water absorption levels. In this research, different EAFS mixes are manufactured and their properties in the fresh and the hardened state are closely analyzed; the results were very promising. The aim of this research is to demonstrate that EAFS concrete can achieve an acceptable workability at the correct dosages.

In this research, the possibility of making a porous asphaltPorous asphalt mixture manufactured completely with recycled aggregates from carbon steel production was explored. Electric arc furnace slag (EAFS)Electric arc furnace slag (EAFS) was used as coarse aggregate and ladle furnace slag (LFS)Ladle furnace slag (LFS) as fine aggregate and filler. Initially, the properties of both slags and their suitability to be used in the manufacture of porous mixtures were analyzed. Then, a series of asphalt mixtures were developed incorporating these slags and they were compared with a reference mixture, made with conventional components. A series of tests were performed, including concepts such as mechanical behavior, durability, moisture susceptibility, rutting resistance, permeability or skid resistance. The results show that it is possible to make a suitable porous asphalt mixture with 100% of steel slag aggregates, complying with the standard requirements and obtaining a durable and environmentally sustainable mixture.

Offshore oil production is known to demand high performance materials used in equipments and machinery due to severe environmental conditions. Polyvinylidene fluoride (PVDF)Polyvinylidene fluoride (PVDF) has been used as the internal pressure sheath layer in unbonded flexible pipe for oil and gas exploitation when HT/HP conditions are found since it is resistance to most chemicals encountered in such operations, to moisture and high thermal resistant. An increase in the use of PVDF in such installations has been observed and hence an increase in the waste generated. A possible solution to this environmental issue would be the re-use of the recycled PVDF by reprocessing primary PVDF wastePVDF waste together with the neat one. Therefore, PVDF_neat/PVDF_waste blends loss and storage modulus were evaluated as well as the influence of aging time period and waste composition in these properties, before and after thermal agingThermal aging.

The controlled rolling of pipeline steels involves pancaking the austenite and then subjecting it to accelerated cooling. However, the formation of ferrite during rolling decreases the amount of austenite available for microstructure control. Here the formation of ferrite during rolling is simulated using a five-pass rolling schedule applied by means of torsion testing. The first and last pass temperatures were 920 and 860 °C with 15° of cooling between passes. All of the rolling was carried out above the Ae₃ temperature of 845 °C that applies to this steel. Interpass times of 10 and 30 s were employed, which corresponded to cooling rates of 1.5 and 0.5 °C/s, respectively. Samples were quenched before and after the first, third, and fifth passes in order to determine the amount of dynamic ferrite produced in a given pass. The amounts of dynamic ferrite formed and retained increased with pass number. The amounts of ferrite that retransformed increased with pass number. The simulations indicate that ferrite is unavoidably produced during plate rollingPlate rolling and that the microstructures present at the initiation of accelerated cooling do not consist solely of austenite.

We seek to explain the weld toe-crack failure in terms of crack nucleation and propagation based on the observed phases and their size. Three welded joins were studied, varying the heat inputs in order to modify the weld microstructure. We work with an API X70 PSL2 pipeline steel, varying the ferritic size phases. We performed Charpy impact and Vickers hardness tests; we also determined the chemical composition (especially the oxygen percentage). Based on the relationship between the test results and the microstructure, we achieve a modification of the welded join microstructure and toughness, observing the heat-input effect in the weld oxygen diffusion as well as its effect in the type and size of the phase observed.

The aim of this study is to evaluate the ability of three nondestructive techniques—ultrasoundUltrasound, thermographyThermography and eddy currentEddy current—for the detection of defects that can occur in metallic substrate with anticorrosive coating and compare the results regarding the advantages and disadvantages of each one of these inspection techniques. For this study, samples were made from a metallic substrate in which a composite anticorrosive coating and two types of defects were introduced: localized corrosion (defects of different geometries and depths inserted into the metallic substrate) and adhesion failure between the coating and the substrate. According to the results, all three techniques showed to be able to detect defects simulating localized corrosion on the substrate. However, the adhesion failure was only effectively detected by thermography and ultrasound and a high correlation between these two techniques was observed.

Duplex Steels have been used for different applications in the oil and gas industry due to their high strength and corrosion resistance. In this work, a Lean Duplex Steel (UNS S32304) has been investigated by High Temperature In-Situ X-Ray DiffractionIn-Situ X-ray diffraction, in order to address phases transformations occurring during high-temperature real time exposure and the formation of deleterious phases such as sigma phaseSigma phase. Samples were subjected to a temperature of 800 °C for different time intervals (30 and 60 min) inside a high temperature furnace attached to an x-ray diffractometer. Formation of sigma phase was observed, both in the ferrite grain boundaries and in the ferrite/austenite interface. The volume of sigma phase was measured by quantitative phase analysis using the Rietveld methodRietveld method and results varied from 2.80 to 15.92% in volume.

The acceptance standards given in API 1104 Section 9 are based on empirical criteria for workmanship and place primary importance on imperfection length. Such criteria have provided an excellent record of reliability in pipelinesPipelines service for many years. Alternative acceptance standards for girth welds are presented in Annex A. The use of fracture mechanics analysis and fitness for service criteria for determining acceptance criteria incorporates the evaluation of both imperfection height and imperfection length. This criteria usually provide more generous allowable imperfection length. This approach is applied to a new gas pipeline, API 5L X70 material, 24 inches diameter and 11.9 mm thickness. The applied methodology is presented to perform failureFailure assessment diagram (FAD) and a sensitivity analysis and safety margins or factors are determined.

The aim of this work was to prove that preparation of Al-B₄C by hot compressionHot compression (HC) at 350 °C (HC) followed by sintering at 550 °C would improve mechanical propertiesMechanical properties with respect to manufacturing by cold compressionCold compression (CC) (CC) followed by sintering at the same temperature, the later experiments were carried out in a previous work. Samples with aluminum matrix adding 0, 3, 5 and 7% were prepared by powder metallurgy technique and tested. The mechanical properties were better using HC. Remarkably, resistance to compression was 3.5 times larger for HC. Vickers hardness, resistance to wearing and impact, as well as density were higher for HC. Scanning electron microscopy of CC specimens exhibit a cellular microstructure while HC ones display a smooth appearance. The better properties of the HC samples are explained due to an improved flow of material at higher temperatures of compression.

As part of ongoing research in the UK, TISICS have developed an improved 140 µm carbon coated silicon carbideSilicon carbidemonofilamentMonofilament for the reinforcement of metal matrix composites. The monofilament is fabricated in a single reactor using a high speed chemical vapor deposition process at a rate of 8 m/min (26 ft/min). Statistical analysis of monofilament properties over two years of production has demonstrated excellent reproducibility of the process. The monofilaments have an average tensile strength of 4.0 ± 0.2 GPa with a Weibull modulus of 50 ± 10. Composites incorporating the monofilaments show similar low variability in yield and tensile strength with the latter exhibiting a mean value above 90% of the maximum theoretical strength predicted by the rule of mixtures. By varying the volume fraction and orientation of the monofilament reinforcement, composite properties can be tailored to fit design requirements. Examples are given of demonstrator components made for the European aerospace sector.

LignocellulosicLignocellulosic fibers natural fibers exhibit high variation in mechanical properties values due to their heterogeneity. Recent studies have shown that the dispersion of these properties depends on the diameterDiameter of the fiber. A possible explanation for the tendency of low mechanical properties with large diameter is the high probability of defects into the fiber. However, no study has yet investigated the relation between the diameter and defects of natural fibers. Hence, in the present work the total porosityPorosity of coir fiberCoir fibers (Cocos Nucifera L.) was estimated. A statistical analysis was carried out on a batch of about 100 fibers and the geometric density was measured by using a stereomicroscope. The closed and open porosity as well as the density of the fiber were quantified by helium pycnometry method. The values obtained were correlated with the diameter of each analyzed fiber. Results made it possible a more detailed knowledge of the porous structure of the fiber.

A multilayer armoring system (MAS) is commonly formed by three layers. The initial layer is normally composed by a ceramic with high compressive strength, which absorbs most of the kinetic projectile energy. The subsequent composite layer was formed by epoxy matrix reinforced with natural malva fibers (Urena lobata, Linn), in the form of pure or hybrid fabric with jute fibers, in order to absorb part of the kinetic energy, and to retain ceramic and projectile shrapnel. A third layer formed by aluminum alloy, was included as a penetration restrictor for bullet and fragments by plastic deformation. The ballistic efficiency was evaluated by penetration of the 7.62 × 51 mm ammunition into a clay witness backing the armor. The results showed a great potential by epoxy composites reinforced with malva fabric as compared to other natural fibers and materials traditionally used in personal protection, such as Kevlar™ aramid.

Advanced ceramics have been extensively applied for ballistic protection, when high levels of protection and low weight are demanded. However, their spalling characteristics require the suitable backing materials to collect the fragments generated on the impact. Synthetic fiber laminates, as KevlarTM and DyneemaTM, are currently the most used solutions despite of their high cost and non-sustainable conditions. Therefore, several materials are being studied to replace the synthetic fiber laminates as second layer, including natural fiber composites, which are light, low cost and sustainable materials. Among these, Amazon curaua fiber composites are promising, due to its known high strength and high modulus. In the present work, novel curaua non-woven fabrics polymer composites have been investigated as part of the ceramic armor system. Ballistic tests were performed following NIJ 0101.06 armor standard. The results showed that these composites are promising alternatives to the synthetic fiber laminates as ceramic backing materials.

ForgingForging is a common method employed in the fabrication of automotive components. In this study, extruded AZ31B magnesium alloy was semi-close die forged at a temperature of 500 °C with a ram rate of 40 mm/s. Microstructural study indicated a bimodal grain structure with weaker textureTexture in the forged material compared to the as-extruded material. Uniaxial compressionCompression tests indicated a remarkable improvement of fracture strain from 36 to 61% with a reduction of ultimate compressive strength between 4 and 22% in the forged samples compared to the as-extruded samples. It is attributed to the modification of microstructureMicrostructure and texture decreases twinning and increases the slipping activity resulting the improvement of ductility and reduced strength at room temperature.

Lightweight materials are the best response to improving performance and efficiency of sport and transportation industrial products. Aluminum is one of the most attractive lightweight materials due to its low density and a high strength to weight ratio achievable through cold working and/or heat treatment. Age hardenable Al–Cu alloys are one of the strongest aluminium alloys available. Sc, though very expensive, is renowned for yielding the highest strength increase per atomic percent of any alloying addition in Al through grain refinement of hyper-eutectic Sc compositions and precipitation hardening. This paper studies the solidification of Al-4.5 wt% Cu with minor Sc additions (hypo-eutectic compositions) over a wide range of cooling rates. The objective is to determine the minimum Sc addition for a maximum strengthening effect while reducing typical processing steps. Based on the microstructures and mechanical properties analyses, a cost and time effective processing route is proposed for the 2000 series aluminum alloys.

The fique fibers are studied worldwide as an alternative of synthetic fibers in composites. This study evaluated the impact resistance of this type of composite. Specimens were made with up to 30% in volume of fique fabric in an Izod normalized mold. The fique fabric was embedded with polyester resin and cured at room temperature for 24 h. The specimens were tested in Izod impact pendulum and the fracture surfaces were examined by scanning electron microscopy (SEM). The impact resistance of composites increased linearly with the relative amount of fique fabric reinforcing the composite. This performance was associated with the difficulty of rupture imposed by the fique fabric as well as the type of cracks resulting from the interaction jute fiber/polyester matrix that corroborate the energy absorption at the impact test.

Jute fibers are among the lignocellulosic fibers with greater potential for use as fabric reinforcing polymer composites. This study evaluated the impact resistance of this type of composite. Specimens were made with up to 30% in volume of jute fabric in an Izod normalized mold. The jute fabric was embedded with polyester resin and cured at room temperature for 24 h. The specimens were tested in Izod impact pendulum and the fracture surfaces were examined by scanning electron microscopy (SEM). The impact resistance of composites increased linearly with the relative amount of jute fabric reinforcing the composite. This performance was associated with the difficulty of rupture imposed by the jute fabric as well as the type of cracks resulting from the interaction jute fiber/polyester matrix that corroborate the energy absorption at the impact test.

Titanium is one of the most important materials nowadays with promising lightweight demanding applications. However, despite its high strength-to-weight ratio, high temperature stability and high corrosion resistance, it has relatively low hardness. It is shown in this work that enhanced hardness values could be obtained for Ti-6Al-4V Alloy after heat treatment consisting of subzero quenching in a medium made up of dry ice and alcohol, followed by an aging treatment. The proposed heat treatment resulted an increase of 25% in the hardness of the alloy, compared to 5% reported in literature.

Syntactic foamsSyntactic foam comprised of glass microballoons have gained considerable attention over the past several years due to mechanical and thermal properties that are advantageous for use as a core material in naval and aerospace applications. Recently, advancements in the production of thermoplastic microballoon syntactic foams have allowed for an increase in microballoon volume fraction (up to 90 volume fraction), with corresponding lower densities but reduced mechanical properties. In this work, carbon nanofibersCarbon nanofiber and halloysite nanotubes were incorporated in thermoplastic microballoon-based syntactic foam to enhances its mechanical properties, and the effects of these two nanoscale reinforcementsNano-reinforcement are compared. X-Ray micro-computed tomography (MCT) was employed to analyze the microstructure of the materials produced, and scanning electron microscopy was used to assess the dispersion of nano-additives within the resin. Through characterization of the tensile and compressive strength properties of these materials, it was observed that dramatic mechanical property enhancements can be engineered through additions of either nano-additive at specific loading levels.

In the current work, Aluminum Alloy 2124-SiC/Graphene nanocomposite is fabricated via high energy milling followed by uniaxial cold compaction at 525 MPa, sintered at 450 °C, and followed by hot extrusion at 4:1 extrusion ratio. SiC nanoparticles (SiC_NP) powders the G-micron-clusters forming G-coated-SiC_NP (GCSiC_NP)G-coated-SiCNP (GCSiCNP) reinforcement filler, used for the reinforcement of AA2124 matrices via milling. The processed nanocomposite combines the properties suitable for dry wear resistant and self-lubricatingSelf-lubricating nanocomposites solids. It is anticipated that the formation of GCSiC_NP decreases the agglomeration of SiC_NP producing uniform dispersion of the GCSiC_NP reinforcement within the Aluminum matrices. Mechanical and wear resistanceWear resistance of the processed GCSiC_NP nanocomposites were characterized compared to the milled AA2124 and AA2124-SiC_NP nanocomposites processed under similar milling conditions. FESEM and XRD are used for the investigation of the milled powders crystallite size, lattice strain, and phases as well as powder morphology.

Recent developments in materials science have increased the interest towards the bulk (energeticEnergetic materials/energy) materials and the technologies for their production. The unique properties which are typical for the composites fabricated in Ti–Al–B–C systems make them very attractive for aerospace, power engineering, machine and chemical applications. In addition, aluminum matrix composites (AMCs) have great potential as structural materials due to their excellent physical, mechanical and tribological properties. Because of good combinations of thermal conductivity and dimensional stability AMCs are found to be also potential materials for electronic packaging/application. The methodology/technology for the fabrication of bulk materials from ultrafine-grained powders of Ti–Al–B–C system are described in this paper. It includes the results of theoretical and experimental investigation for selection of powder compositions, determination of thermodynamic conditions for blend preparation and optimal technological parameters for mechanical alloying and adiabatic compaction. For the consolidation of mixtures, the explosive compactionExplosive compaction technology was applied at room temperatures.

Natural fibersNatural fibers have been extensively investigated in the past decades, due to their good properties, lightweight, low cost and renewable nature. From the ananas erectifolius plant, high strength and high modulus curaua fibersCuraua fibers can be obtained. Their remarkable properties make them adequate to several high performance applications. In the present work, tensile and impact properties of two fiber configurations for curaua reinforced compositesComposites were investigated: a non-woven fiber fabric (NWFF) and high percentage continuous and aligned fiber (HPCAF) composites, using epoxy and polyester as polymeric matrix, respectively. The results showed that the fabric configuration does not effectively reinforce the polymer on tensile load, in spite of promoting significant improvement on the impact properties of the composite. The latter configuration results in both high strength and tough composites, however, its ability to resist to impacts depends on the direction of load.

PolymerPolymer-nanocompositesNanocomposites are being used for numerous applications, ranging from car bumpers to advanced optoelectronic devices. Understanding the impact of nano-fillers on the composite mechanical propertiesMechanical properties is critical to the success of all of these applications. This work focuses on the influence of inorganic spheres-particles such as Al₂O₃Al₂O₃ and platelets, such as Bentonite clay, on the thermo-mechanical properties of the acrylic polymer. The nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis, uniaxial tension, nanoindentation and scanning electron microscopy (SEM). Films drawn from the latex exhibited excellent optical transparency and no evidence of aggregation was detected by SEM and X-ray energy dispersive spectroscopy (EDS). The analysis of the thermal and mechanical properties in the presence of nanoparticles platelets (Bentonite), showed an increase in the glass transition temperature (T _g), decomposition temperatures (T _dec), the Young’s modulus and their hardness. On the other hand, in the presence of spherical nanoparticles (Al₂O₃), the thermal (T _g and T _dec ) and mechanical properties decrease, due to the morphology, dimension (e.g., aspect ratio) and degree of dispersion of the nanofillers in the polymer matrix.

Waterborne acrylateAcrylate hybrid nanocompositesNanocomposites containing 1 wt% nanoparticles were synthesized by in situ polymerization using SiO₂SiO₂ and Fe₂O₃Fe₂O₃ nanoparticles. The synthesized latex hybrids were characterized by thermogravimetric analysis, uniaxial tension, nano-indentation and scanning electron microscopy (SEM). Films drawn from the latex exhibited excellent optical transparency and no evidence of aggregation was detected by SEM and X-ray energy dispersive spectroscopy (EDS) analysis confirmed the presence of silica and iron throughout the films. The thermal properties showed a decrease of the glass transition temperature in the presence of Fe₂O₃ nanoparticles as demonstrated by the dynamic mechanical analysis. The nano-SiO₂ induced significantly higher thermal stability, as decomposition temperatures of the nanocomposites increases by as much as 40 °C relative to the neat acrylic. On the other hand, the Young’s modulus and hardness of the nanocomposites films decrease about 30 and 65%, denoting a modification of macromolecular dynamic by the SiO₂ and Fe₂O₃ nanoparticles, respectively.

The field of polymer/clay nanocompositesNanocomposites is a new route for preparing polymers with enhance properties like higher modulus, thermal stability, better barrier properties, chemical resistance and electrical conductivity. In this work, nanoclay montmorilloniteMontmorillonite (MMT) was incorporated as reinforcement to a copolymer matrix, containing 0, 5% and 10 wt% of nanoclay. Two different processes were used to prepare the nanocomposites: (a) via in-situ (MMT-IN) and the (b) solution mixing (MMT-B). These nanocomposites show an increase in their glass transition temperature, T_g, studied by differential scanning calorimetry (DSC), and also a rise by an order of magnitude in the Young’s modulusYoung’s modulus for both series. On the other hand, the study of thermogravimetric analysis (TGA) for the two series IN and B with addition of montmorillonite clay nanoparticles showed a decreasing behavior in thermal decomposition temperatures, T_dec, relative to the neat copolymer matrix.

Although conventional chemical or thermal recycling techniques are often the most appropriate means of recovering precious and rare metals, biological methods provide an attractive and eco-friendly alternative strategy in which microorganisms are applied to metal extraction. Recently, we have focused on metal ion-reducing microorganisms, Shewanella bacteria that are able to separate and concentrate platinum group metals and gold from solution into microbial cells. In a process, Shewanella bacteria can then be processed to generate metallic nanoparticles at room temperature, within 60 min. When processing the aqua regia leachate of waste LSI (large scale integration), Shewanella bacteria were able to rapidly and selectively collect gold ions from acidic solution. The biotechnological procedure also has the potential to allow the recovery of platinum group metals such as platinum, palladium, and rhodium from the leachate of spent automotive catalysts. We also found that Shewanella bacteria are able to absorb indium from dilute solution. This phenomenon can be applied to use microorganisms, an inexpensive biological material, as an adsorbent. We achieved selective adsorption of indium ions in Shewanella bacteria from the leachate of waste LCD (liquid crystal display) panels by adjusting its pH, because the pH range necessary for Shewanella bacteria to act as an effective adsorbent differs for different metal ions. Our proposed biological method enables the rapid and highly efficient recovery of precious and rare metals by using microbial reactions.

Biotechnological processes are important alternatives for water recycling both in hydrometallurgical and mineral processing operations and this paper is focused on two of such technologies: (i) manganese bioremediation and (ii) sulphate reduction. While highSulphate concentrations are related to hydrometallurgical operations or AMD generation, manganeseManganese is one of the most difficult metals to remove from wastewaters. It is demonstrated herein that a bacterial consortium enriched from a mine water was able to remove 99.7% Mn2+ from a solution containing 50 mg/L. Molecular studies revealed Stenotrophomonas, Bacillus and Lysinibacillus genera in the sample. Cell metabolism resulted in a pH increase and catalysed chemical Mn2+ oxidation. Subsequently, sulphate reduction by sulphate reducing bacteria (SRB) was addressed. A fluidized bed reactor (FBR), in which there was immobilized biomass along with fluidization enabled a high bacterial population (>109 cells/mL) in the bioreactor and thus a large sulphate reduction efficiency (97%) for a specific sulphate reducing rate of 0.186 ± 0.015 g SO₄−2/gVSS.d.

The thermodynamic model of the dissolution of smithsonite (ZnCO₃) in alkaline iminodiacetate aqueous solution (Ida2−–H₂O system) was constructed according to the thermodynamic equilibrium equations in the system. Thermodynamic results of total concentration of Zn2+, free concentration of Zn2+, free concentration of Ida2−Ida2−, free concentration of CO₃2−, species distribution of Zn2+ and species distribution of Ida2− changed with total concentration of Ida2−, and pH value were investigated respectively in the system at 298 K. The total concentration of Zn2+ increases with increasing total concentration of Ida2− at constant pH value. The optimal pH area for the dissolution of ZnCO₃ in Ida2−–H₂O system is pH 8–11. In this area, the total concentration of Zn2+ increases smoothly with increasing of pH, above 90% of Ida2− is used for the formation of Zn(Ida)₂2−, and above 99% of Zn2+ is formed as Zn(Ida)₂2−.

Smithsonite, a typical zinc oxide mineral, has been developed for many years as an alternative source. However, restricted to inferior ability of floating, zinc oxide is one well-known refractory mineral with poor selectivity and high regent consumption. In this paper, ethylenediamine (NH₂CH₂CH₂NH₂) was selected to active flotation of smithsonite using dodecylamine as collector. The effect of ethylenediamine on flotation efficiency was conducted; the results showed that without addition of ethylenediamine, the recovery of smithsonite was only 32.85% when the usage of dodecylamine-hydrochloride as collector was 5 × 10−4 mol/L. The optimum dosage of ethylenediamineEthylenediamine was 6 × 10−3 mol/L and flotation recovery could be obviously improved to 92% under the same usage of collector. This finding may promote the recovery of refractory zinc oxide mineral resource in future.

The Mazowe Gold Mine is managed by Metallon Gold (Zimbabwe) and is situated in the west-central part of the Harare greenstone belt. Orebodies here generally comprise shear zones which are in-filled with gold-bearing sulphides and quartz. The mineralised zones are up to 1 m in width, have average grades of 4–5 g/t. Mazowe Mine is one of the oldest mines in Zimbabwe, and exploration and development in this region dates back to 1890, with over 1.4 million ounces of gold produced to date. Ore is processed in a single plant which consists of conventional crushing and milling and carbon-in-leach facility. Baldmin Projects was awarded the contract for the design, construction and commissioning of the 60,000 tonnes per month plant at Mazowe mine in 2014 for the processing of old tailings dump from previous operations at Mazowe mine. The average grade of the tailings is 1.1 g/t. This paper describes the test work, process design of a processing system at the Mazowe Mine that will improve the extraction efficiency from gold tailings material. The recovery is derived from the separation of the gold contained within the sulphides of the tailings material and a dedicated process stream to recover that gold. The sulphides are separated by means of flotation process and that resulting concentrate is subjected to regrind below 25 µm to enable a greater liberation of the gold. The fine material is then subjected to a dedicated leach process to recover the now exposed gold particles. The case study is an example of the challenges of using existing technology and methodology to a well-established process and there by attaining improved efficiencies and tangibles business benefits.

This paper presents a novel methodology to recover gold from waste solutions of printed circuit boards (PCBs) generated during the goldGoldelectro-platingPlating solutions. Studies have been carried out using two different sizes of hydrocyclone (357.00 and 381.87 mm height) at various parameters such as current, flow rate, electrolyte concentration, cathode materials, and anodic area to recover the gold. ~96% gold was recovered using short-cone type hydrocyclone (357.00 mm) at following conditions: applied current 51.3 A/m2, flow rate 7.7 m/s, using stainless steel as cathode material. However, approximately same amount of gold can be also recovered with long-cone type hydrocyclone (381.87 mm). But, the possibility for damage of long-cone type hydrocyclone might be higher than short cone type hydrocyclone because reaction occurs only at small reaction surface area during gold recovery. Therefore, short-cone type hydrocyclone has been considered for further study to recover gold.

Xinjiang gas coal, one of the Chinese low rank coking coalLow rank coking coals, was modified by high strength modifierHigh strength modifier. By measuring final contraction of coke residue index (x), it revealed that Xinjiang gas coal with high x about 38 mm has an adverse effect on coke quality. The coke quality was evaluated by 2 kg coke-oven coking experiment. The results suggested that the coke strength after reaction (CSR) of the coke increased by 21% and the coke reactivity index (CRI) decreased by 18% when 0.5 wt% high strength modifier was added into gas coal. The increase of the diameter of carbon network layerCarbon network layer and the decrease of the disordered and unsystematic inherent polycondensationInherent polycondensation in the Semicoke contraction stage may be responsible for the modified results. The modified mechanism was proposed based on thermo gravimetric (TG) and FTIR spectrometer characterizations of the modified coals, and X-ray diffraction (XRD) analysis of modified cokes.

Celestite is the main source of strontium containing chemicals and metallic strontium. Unlike other sulfate containing minerals, celestite is not soluble in water. Further processing of SrSO₄ requires conversion to water-soluble strontium sulfide (SrS). In this study, solubility of SrS in distilled water is investigated. SrS used in experimental study was obtained by roasting celestite at 1050 °C in a lab-scale rotary furnace. Experiments were carried out to determine the effects of time (90, 120, and 150 min), solid/liquid (S/L) ratio (1/5, 1/10, and 1/25 w/v) and temperature (25, 55, 75, and 95 °C). Stirring speed (500 rpm) was constant. XRD results of leach cakes showed that increasing temperature increases dissolution rate and efficiency. However, increasing S/L ratio decreases the leaching efficiency.

Calcification roasting-sulfuric acid leaching process was used to extract vanadium from converter slag. The kinetics of the extraction process based on both unmilled and ball milled slags in dilute sulfuric acid solution (pH = 2.5 ± 0.2) were investigated. The results showed that the extraction of vanadium was a rapid process with particularly a considerable proportion of vanadium rapidly dissolved in the first 10 min. The kinetics analysis showed that the diffusion through product layer was rate-determining step in the course of the dissolution of vanadium. The linear relationship between the rate constant and the inverse square of the particle diameter also illustrated this phenomenon. Mechanical activation can significantly accelerate the vanadium leaching efficiency, and decrease the corresponding apparent activation energy from 9.94 to 7.63 kJ/mol.

In this work, the effect of crushing, temperature, oxalic acid concentration and stirring speed on the leaching of spent Ni–Mo HDS catalyst was investigated. Spent Ni–Mo HDS catalyst was roasted at 500 °C under dynamic air atmosphere for 4 h prior to leaching experiments. It was found that roasted spent Ni–Mo HDS catalyst included mainly Al₂O₃, MoO₃, NiMoO₄ and AlPO₄. Leaching experiments were performed using 5 g of uncrushed roasted Ni–Mo HDS catalyst, 1 L of 0.25, 0.50, 0.75 and 1 M H₂C₂O₄ solutions, 25, 40, 55 and 70 °C temperatures and 200, 250 and 300 rpm stirring speeds. Leaching behavior of Mo, Al, P and Ni was determined. It is seen that H₂C₂O₄ can be used successfully for the leaching of roasted HDS catalyst. More than 90% of the molybdenum and 80% of Nickel is extracted from the experiments carried out using 300 rpm stirring speed, 1 M H₂C₂O₄ and 40 °C.

A novel adsorbent (FB-mZVIFB-mZVI) was prepared, using tailings from iron ore concentration plants, fly ash and bentonite, to remove crystal violet (CV)Crystal violet (CV) and methylene blue (MB)Methylene blue (MB) from polluted waterWater. The adsorbent was prepared as cylindrical-shape pellets to easily separate it from the water after the adsorption process. The statistical orthogonal method was used to evaluate the factors determining the synthesis of FB-mZVI. Batch experiments revealed that the optimum mass ratio of fly ash, bentonite, iron ore tailings and palm kernel shell was 2:2:1:1. And in the synthesis of FB-mZVI adsorbent, the optimum reaction temperature was 800 °C, the reaction time was 10 min and the heating rate was 10 °C/min. SEM Characterization revealed that the adsorbent was highly porous and constituted by Fe0 particles finely dispersed on an aluminosilicate matrix. The adsorbent showed to have a superior adsorption capacity for CV and MB when compared to other conventional adsorbents. The adsorption kinetics and isotherms of CV and MB on FB-mZVI adsorbents could be expressed by the pseudo-second-order model and Langmuir isotherm.

This work seeks to evaluate the effect of the sorting of calcium/magnesium carbonates (limestone ores) through the use of X-ray and CCD camera sensors. Collection of the 17 samples used for this study was performed after primary crushing at a size range between 76 and 152 mm (3–6″). This work seeks to evaluate the effect of the sorting of calcium/magnesium carbonates (limestone ores) through the use of X-ray and CCD camera sensors. Collection of the 17 samples used for this study was performed after primary crushing at a size range between 76 and 152 mm (3–6″). Sampling was intended to represent all of the possible variations of the ore and waste currently being extracted. For initial characterization, samples were washed and subjected to analysis by a handheld X-ray fluorescence spectrometer. Sensor based sorting tests were performed at the Federal University of Rio Grande do Sul (UFRGS) using a COMEX lab sorter. The lab sorter is comprised of a conveyor belt, mounted sensors, a data processing system, and a pneumatic flap system for the physical separation of the samples. Results of the X-ray separation showed that of the 12.2 kg of samples, 10.5 kg were sorted into product and only 1.7 kg were separated as waste. However, within the waste fraction, only 54.5% was considered waste, and likewise 7% of the product fraction was considered waste. When using the CCD camera, 100% of the ore fraction and 100% of the waste fractions were considered to be sorted correctly. While it is important to note that this is only a preliminary study analyzing the viability of implementation of the automatic sorting system, these preliminary results obtained with the use of both sensors were considered satisfactory.

Increasing demands for copperCopper and copper sulphateCopper sulphate with diverse industrial applications has prompted the development of a low-cost and eco-friendly technique as a substitute for conventional ore treatments by reduction-roasting route, requiring high energy consumption. In this study, hydrometallurgical treatment of a Nigerian malachite through acid leachingLeaching and solvent extractionSolvent extraction was investigated. The effects of leachant concentration, reaction temperature and particle size were examined. The rate of ore dissolution increased with increasing H₂SO₄ concentration, temperature and decreasing particle size. At optimal leaching conditions, 96.2% of the ore reacted with 2.0 mol/L H₂SO₄ solution at 75 °C within 120 min. The calculated activation energy was 25.41 kJ/mol, supporting the proposed diffusion controlled mechanism for the dissolution process. The leach liquor at optimal conditions was further beneficiated to obtain high grade industrial copper sulphate using a combinations of solvent extraction and precipitation methods, leading to 98% process efficiency.

The quality of the iron ore, over the decades of exploitation lowered, due to the reduction of the rich ores found at the beginning of the exploration. It resulted in ores with lower grades and more mixed with the gangue. Iron ore is processed after comminution and grinding, to have appropriate particle size and release the stages of flotation, which is divided generally in Rougher steps, Cleaner, Scavenger and Re-Cleaner. Flotation is a process that uses an ore slurry with additions of flocculants, surfactants, and other products. These substances are fundamental to the operation. However, it compromises of the reuse of the water. The proposal presented in this paper introduces a pre-treatment process of the pre-flotation material, still in Rougher step, which will increase its efficiency in such way that only one Cleaner step would be sufficient to generate a concentrate ready to be considered flotation of the final product.

Celestite ore (SrSO₄) is used as raw material for the production of strontium compounds. The aim of this study is to develop a new and efficient strontianite (SrCO₃) production method. Strontianite was obtained from domestic celestite concentrate with direct conversion method in which celestite reacts with $$ {{\text{CO}}_{3}}^{2 - } $$ and $$ {{\text{NH}}_{4}}^{ + } $$ containing solution. Thus, the effect of particle size, time, ammonia concentration on the conversion was investigated. $$ ({\text{NH}}_{4} )_{2} {\text{CO}}_{3} $$ solution was used as carbonate agent. Because the solution is decomposed at 58 °C, experiments were performed low temperatures. Celestite ore was converted to strontianite between 3 and 6 h depending on ammonia concentration and celestite mass. Characterization of celestite ore, products and reaction residues were carried out by DSC, TG, XRD, and AAS analytical techniques.

The present work deals with the characterization of pure magnetite microfines (<5 μm) and its hydrogen reduction. The structural and morphological properties of magnetite powder were analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption analysis by five points isotherm BET method, and scanning electron microscopy along with energy dispersive X-ray spectroscopy (SEM-EDS). The hydrogen reduction of the magnetite powder was carried out in a thermogravimetric analyzer (TGA) under a steady flow of hydrogen or hydrogen-argon mixture (to produce different partial pressures of hydrogen). The variables studied were reduction temperature (973–1273 K), hydrogen partial pressure (0.25–1 atm) and sample bed height (0.184–0.68 cm). The apparent activation energy was obtained as 22 kJ mol−1. The rate equations developed for the reaction system under study were applied to determine the rate controlling step. The reduction was found to be rate controlled by diffusion through the stagnant gas film enclosed above the sample inside the crucible. The true activation energy was calculated to be 9 kJ mol−1.

After extracting rare earths minerals, iron minerals and fluorite from Bayan Obo ore, niobiumNiobium and scandiumScandium which are riched in the mineral processing tailingsMineral processing tailings coexist with the remaining rare earth. In order to recovery these valuable elements, the tailings was disposed with the method of activating roasting-acid leaching. The tailings was roasted with NaCl–Ca(OH)_{2NaCl-Ca(OH)2} under a temperature of 900 °C for 1.5 h. Weight percentages of NaCl-to-tailings and Ca(OH)₂-to-tailings are 10% and 20% respectively. Then the roasted ore experienced two leaching stages from “hydrochloric acid pre-leaching at 90 °C for 1.5 h” to “intensified sulfuric acid leaching at 300 °C for 1 h”. The results show that, the leaching ratesLeaching rates of niobium, scandium and rare earth in roasted ore could reach 86.80, 97.42 and 97.94% respectively under the conditions above. Moreover, the radioactivity per unit mass of leaching residue was reduced to 745 Bq/kg and environmentally friendly.

Thermal decomposition and oxidation characteristics of three typical iron ores were studied with differential thermal analysis and XRD techniques. The results displayed that DSC curve of limonite showed a significant endothermic arc in the range of 605–1150 °C. It was thought that the decomposition of crystal water in limonite increased the porosity and surface area of limonite, which improved the adsorption capacity of limonite. DSC curve of hematite showed a weak endothermic arc in the range of 312–652 °C. DSC curve of magnetite showed a significant exotherm arc in the range of 162–915 °C. It was thought that lots of heat released when Fe₃O₄ in magnetite was oxidized.

Gold is an important industry and strategic reserves of metal, but cyanide leaching process have adverse to the environment. In this paper, an absolutely non-cyanide bromide gold-leaching system was puts forward to leaching a kind of micro-disseminated gold concentrateGold concentrate leaching from China. The influence of different reagent concentration and temperature on the bromide leaching process were tested in this research, and various testing methods as X-ray diffraction (XRD), scanning electron microscopy, infrared spectroscopy, and laser particle size analysis were carried to characterize the leaching residue. Results show that the leaching rate of Au is increasing as the concentration of leaching agent and oxidant rising; temperature rise will accelerate the leaching reaction rate, gold-leaching efficiency after 8 h can reach 97.93%; XRD and infrared spectroscopy testing indicate that the mineral structure is destroyed completely, the desulfurization rate of S element can reach 96%.

The new facility for washing and leaching of 70,000 tpy of WOX (zinc waelzoxide) with a high content of chlorine and fluorine, was put into service at the end of March 2013. The process technology of removing chlorine and fluorine is made of two stages of continuous washing. The first step—is a counter-current washing of WOX at atmospheric pressure and the second stage is the high pressure washing. Second stage washing is carried out at the pressure of about 2 bar and temperature 120 °C, in an autoclave. The next step of the process is leaching of washed WOX with spent electrolyte coming as a feedback from existing Cell House. After separation and filtration the zinc sulphate solution is directed to the existing neutral leaching section. The final level of chlorine and fluorine are ClCl and F-Removal < 0.005%, and F < 0.01%.

Microstructural evolutions of AA1050 aluminium alloy, prepared by accumulative press bonding, have been investigated by means of sophisticated analytical tools, including STEM and EBSDElectron backscattered diffraction (EBSD). The results revealed that continuous dynamic recovery was dominant mechanism in grain refinement, and resulted in formation of nano/ultrafineNano/ultrafine structured materials grains with average diameter of 450 nm in pressing direction and 320 nm in transverse direction. By increasing strain during APB process, the mean misorientation angle and the fraction of high angle boundaries increased and reached a saturation value of ~35° and ~78%, respectively.

2 mm thick Al-7B04 alloy sheets under T4 and O tempers were subjected to friction stirFriction stir processing (FSP). The microstructure, Vickers hardness and tensile properties of the stir zone were characterized. The results show that FSP led to the formation of full recrystallized microstructure, the average grain size in the stir zone (SZ) was about 2 μm. Besides, the stir zone produced using the base metal under T4 temper was softened, while a significant strengthening was observed when the base metal temper was O. Furthermore, both the natural aging (NA) Natural aging (NA) and post-processed heat treatment (PPHT) Post-processed heat treatment (PPHT) were also conducted on FSP samples. And it indicates that NA was beneficial to strengthening the SZ regardless of the initial base metal temper. On the contrary, PPHT only contributed to the strengthening of SZ using the base metal under T4-temper.

In this work it is reported the evolution of the microstructure of the as-cast and homogenized Zn–21Al–2Cu samples, after 2 and 6 passes in an equal channel angular pressing (ECAP) at room temperature. A homogenization treatment for 24 h at 350 °C was applied in the as-cast samples and then they were deformed. An annealing heat treatment was made in all samples after ECAP process. One of the main results is that the homogenized and deformed samples showed a uniform fine-grained microstructure after annealing, while as-cast samples without annealing presented only some regions with fine-grained microstructure. The micro segregation level was higher in the as-cast samples in contrast to the homogenized ones even after annealing. Vickers microhardness measurement on samples after deformation is smaller than the original material indicating a softening, however after the annealing treatment the microhardness increased, indicating that there was a slight hardening of the material.

The effect of titanium sulfide particlesParticles on the grain sizeGrain size characteristic of low carbon steelLow carbon steel was analyzed. Optical microscope (OM), scanning electron microscope (SEM) were used to characterize the grain sizeGrain size and particles. The result showed that grain size increased from 19.95 to 60.56 μm after heat treatmentHeat treatment. The particles were mainly titanium sulfide in the size range of 0.2–0.8 μm and the volume fraction decreased significantly from 0.0084 to 0.0023%. The thermodynamic calculation resulted that these particles were dissolved during heat treatment. The pinning force of grain boundary and the driving force of grain growth were calculated. Based on experimental results and theoretical calculations, titanium sulfide particles with diameter from 0.2 to 0.8 μm and volume fraction of 0.0084% would be sufficient to inhibit the ferrite grain growth.

A new model to predict the dislocation density evolution of 30Cr2Ni4MoV steel during hot deformation was proposed in this study. Hot compression of 30Cr2Ni4MoV steel was carried out on Gleeble 1500 at different temperatures and strain rates. A series of flow curves was obtained and the experimental dislocation densityDislocation density evolution was derived from the experimental flow curves. Based on the obtained flow curves, the dependences of yield stress, critical stress and strain of dynamic recrystallizationDynamic recrystallization (DRX) and the saturation stress on temperature and strain rate were determined. Two sets of dislocation density equation were derived from the experimental flow curves: (I) a dislocation density relation describing the grains in which dynamic recovery took place only; and (II) an average dislocation density expression pertaining to the recrystallized grains. All the parameters needed for the determination of the dislocation equations were calculated and expressed as a function of strain, temperature and strain rate. A physically realistic and practical kinetics modelKinetics model of dynamic recrystallization was determined with the aid of the above relations. Finally, the dependence of the dislocation density on strain, deformation temperature and strain rate was determined and the predicted results agreed well with the experimental results.

The work presents results of investigation on a new heating method for production of high-strength car body elements. It’s proposed to substitute the conventional heating of blanks in gas or electric furnaces through the rapid contact heating. The blank at this process is pressed between two heated plates during few seconds and subsequently quenched in water-cooled dies to obtain high-strength properties due to the martensitic transformation. The influence of heating temperature in the range between 800 and 1000 °C and dwell time from 4 to 16 s on the microstructure and mechanical properties of 1 mm thick sheet of a low alloyed manganese-boron steel was studied. Furthermore, press hardeningPress hardening including common heating in electric furnace at 950 °C during 360 s and quenching in water-cooled dies of the same sheet was performed to compare the resulted microstructure and mechanical properties with the rapid heated and press hardened material.

The new generation of value-added low carbon niobium (Nb) microalloyed beam, plate and rebar construction steels for both low and high yield strength and energy absorption applications are shifting designers to these new high performance lower cost materials. The civil engineering and end user community demand structural reinforcing bars, shapes, beams and plates with improved energy absorption and fatigue properties. The future market demands better fire and seismic resistance, yield-to-tensile ratio consistency, improved bendability and weldability. These attributes are difficult to obtain from steel producers today with their current higher carbon microalloyed steel approach. However, there is a global shift in motion to low C–Nb bearing construction steels displacing traditional materials. For example, in the construction beam sector and rebar sector improved properties result for 0.02–0.04%Nb in low carbon steel for S355 and S420 beams and for S500 and S600 low carbon reinforcing bars.

The kinetics of austenite decomposition during the continuous cooling of a low-carbon welding steel was determined by dilatometric analysis. Based on the measurements, the critical transformation temperatures of austenite decomposition were determined for both ferrite and pearlite. The cooling conditions were established from the Stelmor® controlled cooling process for the manufacturing of wire rod. It was observed that the critical temperatures decrease when the cooling time was reduced as a result of an increased cooling rate in the range of 600–900 °C. Using the decomposition temperatures, a continuous cooling transformation CCT diagram was created and it may be observed that austenite decomposition occurs in two steps. The kinetic parameters for each step were determined and compared with the Johnson-Mehl-Avrami-Kolmogorov diffusive model. The final microstructure was analyzed using an optical microscope and evaluated by nanoindentation to determine the effect of the cooling rate on the nanohardness of each phase.

Steel rods are hot-rolled at high strains and strain rates with a subsequent controlled cooling process to influence the microstructure. The microstructure and mechanical properties of the hot-rolled rods are controlled to produce high-strength fasteners in the cold heading process without subsequent heat treatment. In the present study, simulations of rod rollingRod rolling by torsional deformation and controlled time-temperature schedules were conducted to examine the effects of thermomechanical processing parameters and microalloyingMicroalloying additions on the microstructure evolution and mechanical properties of low-carbon steel rods. Transformation and precipitation behaviors during the thermomechanical process were investigated and related to the increased strength in the steel rods.

Ladle refining plays a key role in achieving the quality of the steel. Specifically the metal-slag mass exchange is studied through a scaled water physical modelPhysical model in which thymol, a solute, is added to the water (steel) and silicon oil (slag) picks up the thymol, while the ladle is agitated with the central gas injection and samples of water were taken to track the thymol concentration with time with a UV-visible spectrophotometer. Also, a mathematical modelMathematical model was developed and solved with the CFD code Fluent Ansys to represent the fluid flow and the mass transfer phenomena through the solution of the continuity, the turbulent momentum conservation and species mass conservation equations. A good agreement between the measured and the computed results regarding the thymol concentration evolution in water was found so the model was validated and it may be used to study metal-slag exchanges in the steel ladle.

The spring steel 55SiCrASpring steel 55SiCrA produced in a domestic steel factory is deoxidized by Si with “100 t EAF-LF-VD-CC”. The fluoric content (CaF₂ = 17.41–22.15%) and the binary basicity (R = 1.9–3.0) of applied LF refining slagLF refining slag are high. To avoid environmental pollution caused by fluorine, meanwhile guarantee the speed of melting slag and smelting effect on molten steel, the structure of refining slag was adjusted. A new fluorine-freeFluorine-free slag system was obtained by changing slagging process, adjusting adding amounts of slag-making materials, such as lime, calcium carbide, silicon carbide and so on. This new fluorine-free slag was applied in industrial tests. The results showed that this new fluorine-free slag could meet smelting demands well. The average mass fraction of oxygen content of spring steel 55SiCrA billets could decreased from 11 × 10−6 to 9 × 10−6 and the plasticity of inclusions also changed better. All compositions of observed inclusion in billets were within the 1400 °C liquidus in Al₂O₃-SiO₂-CaO-MgO-MnO phase diagram.

The tempering response of fully martensitic microstructures has been well characterized. However, bainitic microstructures may also be found in quenched industrial materials and the present study investigates the tempering response of fully martensitic and fully bainitic microstructures. Specific thermal cycles were developed to generate both microstructures in a boron added 0.17 wt pct carbon steel. The tempering response was assessed through dilatometry and microstructural characterization was conducted using scanning electron microscopy and Mössbauer spectroscopy. The dilatometric analysis of the tempering response of the martensitic microstructures provided information about retained austenite decomposition and cementite precipitation whereas bainitic microstructures showed a less sensitive dilatometric response during tempering likely due to the low amount of carbon in solution and absence of retained austenite as measured by Mössbauer spectroscopy.

Circulating kinetic energy has important influences on process of rapid decarburization rate in RH. A physical model of 300 t RH in 1:6 ratio is established to study the relationship between gas behaviors and circulating kinetic energy in this paper. The studies showed that the circulating kinetic energy of liquid steel has the exponential relationship with the bubble velocity and gas volume fraction (17–26%). However, the proportion that the circulating kinetic energy accounted for the total energy is less than 1%, when the void fraction in the up leg is lower than 22% or the bubble velocity less than 0.5 m/s. Therefore, in order to avoid appearing lowest energy value and take advantage of gas-driven energy, must satisfy threes below requests. Ensuring the void fraction is greater than 22%. The vacuum chamber bubble residence time is around 0.15 s. And the bubble rising velocity is not less than 0.5 m/s. Satisfying the above conditions can optimize flow effect of molten steel and improve the decarbonization rate.