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“Real time” imaging techniques have assisted materials science studies especially for non-ambient environments. These techniques have never been collectively featured in a single venue. The book is an assembly of materials studies utilizing cutting edge real time imaging techniques, emphasizing the significance and impact of those techniques.

### A Novel Method of Surface Tension Test for Melt Slags Based on Hot Thermocouple Technique

Currently, the sessile drop method and the maximum bubble method are widely used to measure the surface tension of melt slags. For the above methods, the slow heating rate of furnace decreases the test efficiency. The hot thermocouple technique is widely used in the measurement of the high-temperature performance of molten slags. The slag will form droplets on the thermocouple due to the capillarity, and based on the rapid heating-up and Young’s equation, this study used the Single Hot Thermocouple Technique (SHTT) for the test of CaO–SiO2–Al2O3 (CSA) and the CaO–SiO2–Al2O3–MgO (CSAM) slag systems. The results show that the interfacial tension between the CSA, CSAM slags and the thermocouple is 2117.76–2131.89 mN/m at 1500 °C. The surface tension of the CSA, CSAM slags can be obtained by Young’s equation. Compared with the surface tension measured by the standard test, the SHTT surface tension test error is within 5%.
Zhe Wang, Guanghua Wen, Ping Tang, Zibing Hou

### In Situ Observation on the Interactions of Nonmetallic Inclusions on the Surface of Liquid Steel

The behaviors of several types of inclusions on the surface of liquid steel were examined using a confocal laser scanning microscope, CLSM . While alumina inclusions are likely to attract each other, agglomerate, and grow fast by the agglomeration, the other types of inclusions such as spinel and calcium aluminate rarely interact with each other. The analysis on the observation result of the CLSM indicates that the attraction force and the agglomeration play a significant role in the growth of alumina inclusions. Moreover, the behaviors of liquid calcium aluminate inclusions, which were intentionally injected, could be carefully observed. Their agglomeration took place only when they occasionally collide under the existence of external force, in spite of relatively low collision probability.
Youngjo Kang, Piotr R. Scheller, Du Sichen, Kazuki Morita

### In Situ Structural Variations of Individual Particles of an Al2O3-Supported Cu/Fe Spinel Oxygen Carrier During High-Temperature Oxidation and Reduction

Physical and chemical degradation of the oxygen-carrier materials during high-temperature redox exposures may affect the overall efficiency of the chemical looping process. Therefore, studying real-time physical and chemical changes in these materials when exposed to repeated redox cycles is essential for further development of chemical looping technology. In this work, the National Energy Technology Laboratory’s Al2O3-supported Cu/Fe spinel oxygen carrier, in the form of a CuO · Fe2O3 solid solution, was examined in situ during 3-h exposures to either oxidizing or reducing environments at 800 °C using a controlled atmosphere heating chamber in conjunction with a confocal scanning laser microscope. A compilation of the physical changes of individual particles using a controlled atmosphere confocal microscope and the microstructural/chemical changes documented using a scanning electron microscope will be discussed.
W. H. Harrison Nealley, Anna Nakano, Jinichiro Nakano, James P. Bennett

### Surface Tension of High Temperature Liquids Evaluation with a Thermal Imaging Furnace

At high temperature, the reactivity of liquid metals, salts, oxides, etc. often requires a container-less approach for studying composition-sensitive thermodynamic properties, such as component activities and surface tension. This experimental challenge limits access to essential properties, and therefore our understanding of molten systems. Herein, a thermal imaging furnace (TIF) is investigated as a mean of container-less study of molten materials via the formation of pendant drops. In situ optical characterization of a liquid metal drop is proposed through the use of a conventional digital camera. We report one possible method for measuring surface tension of molten systems using this pendant drop technique in conjunction with an image analysis procedure. Liquid copper was used to evaluate the efficacy of this method. The surface tension of liquid copper was calculated to be 1.159 $$\pm \ 0.043$$ N$$\text {m}^{-1}$$ at $$1084\pm 20$$ $$^{\circ }\mathrm {C}$$, in agreement with published values.
Mindy Wu, Andrew H. Caldwell, Antoine Allanore

### New Laue Micro-diffraction Setup for Real-Time In Situ Microstructural Characterization of Materials Under External Stress

Laue X-ray diffraction (XRD) is a powerful probe to characterize pressure-/strain-induced microstructural changes in materials. The use of brilliant synchrotron radiation allows Laue XRD to be measured in a fast manner, leading to microstructural characterization, such as two-dimensional maps of single-crystals, their texture, and deformation, to be made in time-resolved mode with temporal resolution down to seconds. This technique can be very efficient in the studies of mechanisms of deformation, grain growth, recrystallization, and phase transitions. A progress has been obtained to extend application of Laue diffraction to high-pressure area. Recent case studies of α → β transition in Si and α → ω transitions in Zr are briefly reported. A new experimental setup specifically optimized for real-time in situ Laue measurements has been developed at the 16-BMB beamline at the Advanced Photon Source. Due to the large X-ray energy range, which is typically up to 70 keV, a polychromatic beam diffraction technique can be efficiently implemented despite some limits introduced to the scattering angle by strain generation devices. Currently, the X-ray beam is focused at the sample position down to ~2.2 × 2.2 μm2 at the full width at the half maximum. Precision sample translation stages provide fast data collection with step sizes down to 0.5 μm.
D. Popov, S. Sinogeikin, C. Park, E. Rod, J. Smith, R. Ferry, C. Kenney-Benson, N. Velisavljevic, G. Shen

### In Situ Study on the Transformation Behavior of Ti-Bearing Slags in the Oxidation Atmosphere

Rutile acts as a target phase for the titanium (Ti) recovery from Ti-bearing blast furnace slags (Ti-BFS) due to its special properties. In this study, using single hot thermocouple technique (SHTT), we investigated the crystallization behaviors of the Ti-BFS and the target rutile precipitation behaviors where both the holding temperature, the basicity (mass ratio of CaO to SiO2) and the P2O5 content were considered. We found that basicity has a vital influence on the crystallization behaviors and rod-like rutile only formed with lower basicity. As the basicity increased, the primary phase would transform from rutile to perovskite. As the basicity was 0.5, with the temperature increasing, the growth rate of rutile length initially increased, followed by a decrease with further increasing holding temperature. Thus, the growth rate of rutile had a maximum value of 7.74 µm/s at 1260 °C. Furthermore, the rutile growth followed a one-dimensional template, and the P2O5 content had an important impact. By increasing the content of P2O5, the incubation time of the rod-like rutile got decreased, suggesting that the rutile precipitation got much easier.
Yongqi Sun, Zuotai Zhang

### Dissolution of Sapphire and Alumina–Magnesia Particles in CaO–SiO2–Al2O3 Liquid Slags

Understanding the dissolution kinetics of non-metallic inclusions in liquid slag is key in optimization of slag composition for inclusion removal . In this study, the rate of dissolution of high-precision spheres of sapphire and alumina–magnesia particles in CaO–SiO2–Al2O3 liquid slags was measured in situ using a laser scanning confocal microscope at 1500 °C. It was found that the rate of dissolution of both sapphire and alumina–magnesia particles increased when the slag basicity is increased. A layer was observed around the dissolving sapphire. This layer may be a product layer and/or indicative of a mass transfer rate-controlling system. In the case of alumina–magnesia particle, the kinetics appeared more complex and depended on slag composition. No product layer or mass transfer layer was observed around the particle dissolving in slag with low basicity, whereas for the high basicity slag, a product or stagnant layer was observed, similar to that of the sapphire particle. Assuming a mass transfer-controlled system, measured diffusion coefficients for sapphire particles in slags tested in this study ranged from 10−11 to 10−10 m2 s−1 at 1500 °C.
Hamed Abdeyazdan, Neslihan Dogan, Raymond J. Longbottom, M. Akbar Rhamdhani, Michael W. Chapman, Brian J. Monaghan

### In Situ Characterization of Hot Cracking Using Dynamic X-Ray Radiography

We employ dynamic X-ray radiography (DXR) for in situ and real-time characterization of the hot cracking phenomenon for aluminum alloy 6061 under the processing conditions typical of laser powder bed fusion. The dynamics of processes such as a crack initiating from a bubble trapped subsurface are captured. We also directly observe the backfilling of liquid that heals an open crack. In addition, we demonstrate the feasibility of determining the point of origin for hot cracking with a temporal resolution of order 20 µs and spatial resolution of order 2 µm. This could shed light on the estimation of solid fraction at the initiation of hot cracking, which is a critical parameter upon which many models are based. We demonstrate the capability of DXR for generating new insights into verify or refine hot cracking models, and understand this problem fundamentally, which could ultimately lead to the optimization of process control for additive manufacturing .
Po-Ju Chiang, Runbo Jiang, Ross Cunningham, Niranjan Parab, Cang Zhao, Kamel Fezzaa, Tao Sun, Anthony D. Rollett

### High-Frequency Ultrasound Analysis in Both Experimental and Computation Level to Understand the Microstructural Change in Soft Tissues

High-frequency ultrasound has become a popular tool in characterizing small-scale soft materials. This method is particularly effective in pitch-catch mode. It has been used in tissue phantoms to evaluate the microstructure. This method has the potential to be used in determining the tissue pathology in cancer and other tissue degenerative diseases. Among different types of parameters of ultrasound, peak density has been found to be most sensitive to the microstructural and scatterer variations in soft materials. 25 MHz ultrasound wave is used in a pitch-catch mode to evaluate mm scale tissue phantoms with microscale scatterers on different thickness levels. FFT is used to convert the receiving signal to frequency domain, calibrate to remove the noise and analyze the peak density. Finite element simulation is used to model the wave propagation in the medium containing scatterers to find a systematic correlation with the scatterer density.
Leila Ladani, Koushik Paul, Jeremy Stromer

### Study of Mold Flux Heat Transfer Property by Using Thermal Imaging Enhanced Inferred Emitter Technique

A thermal imaging enhanced inferred emitter technique was developed to investigate the heat transfer behavior of mold flux. Then, the phase transformation behavior, the heat transfer behavior, the temperature field evolution and the mold/slag interfacial thermal resistance evolution for a demonstration experiment of medium carbon mold flux slag disk were in situ recorded. The demonstration experiment results showed that the phase transformation behavior of mold flux significant affected the radiation heat transfer. And the phase transformation behavior also led to the change of temperature distribution on the slag. According to the in situ observation of slag temperature field, the crystallization behavior of mold flux made the high-temperature region move toward the crystalline layer. The variation of the mold/slag interfacial thermal resistance Rint also had been directly obtained with the help of thermal imager. Rint decreased with the increase of mold/slag interfacial temperature. In addition, mold/slag interfacial deformation and the decrease of interfacial temperature caused by the crystallization behavior led to an increase of Rint.
Kaixuan Zhang, Wanlin Wang, Haihui Zhang

### Sub-rapid Solidification Study by Using Droplet Solidification Technique

Droplet solidification technique is important with respect to the fundamental study of strip casting given the common conditions of direct contact between cooling mold and solidifying metal. In this study, an improved droplet solidification technique has been developed for the in situ observation of the sub-rapid solidification phenomena of metal droplets impinging onto the water-cooled copper substrate. The heat transfer rates were calculated by the inverse heat conduction program (IHCP) , according to the responding temperatures’ gradient inside the cooling mold. Meanwhile a charge coupled device (CCD) camera was placed beside the bell jar aimed to record the whole melting and solidification process of the steel sample, which also allowed the determination of the final wetting angel, during the dipping tests. Moreover, it was found that the heat transfer rate increased with decreasing final contact angle, which means better wetting condition between the liquid sample and the copper substrate.
Cheng Lu, Wanlin Wang, Chenyang Zhu

### Comparison of Dissolution Kinetics of Nonmetallic Inclusions in Steelmaking Slag

Nonmetallic oxide inclusions of Al2O3, Al2TiO5, and CaO · 2Al2O3 (CA2) types are responsible for clogging of ceramic nozzles during liquid steel processing. The dissolution of these inclusions in steelmaking slags alleviates the clogging phenomenon. The in situ dissolution behavior a single oxide particle is studied in a synthetic CaO–Al2O3–SiO2 type slag using a high-temperature confocal scanning laser microscope at 1550 °C. The rate determining step for Al2O3 and CA2 inclusions was confirmed to be mass transport control in slag. The rate determining step for dissolution of Al2TiO5 needs further investigation. The rate of dissolution varied in the order from slowest to fastest: Al2O3 < CA2 < Al2TiO5.
Mukesh Sharma, Neslihan Dogan

### Quantitative Thermal Analysis of Solidification in a High-Temperature Laser-Scanning Confocal Microscope

Under near-equilibrium conditions, the concentric solidification technique proved to be an excellent way of studying in situ, solidification phenomena, but under rapid cooling conditions, the solid/liquid interface undergoes dynamic thermal and solute distributions. The current project aims to evaluate temperature distribution under rapid cooling conditions. A number of thermocouples are attached to the specimen surface and measured the temperature over the solidification period. The temperature profile within the liquid phase is measured separately by thinner thermocouple wires which are fixed to the crucible so that the surface tension of the molten liquid keeps the thermocouple suspended in the liquid pool. The dynamically changing temperature profile over the radial axis of the specimen under rapid cooling conditions is determined, including the all-important temperature at the solid/liquid interface . The calculated interface temperatures are utilized in phase-field simulations, and the results are found to be in excellent agreement with experimental results.
Dasith Liyanage, Suk-Chun Moon, Madeleine Du Toit, Rian Dippenaar

### In Situ Investigation of Pt–Rh Thermocouple Degradation by P-Bearing Gases

Gases bearing elements such as As, S, and Si are known to degrade Pt and Pt–Rh alloys, leading to thermocouple sensor failure during industrial operations. While the corrosive impact of As, S, and Si gases have been discussed in the literature, the impact of P has not been well studied. P may originate from the carbon feedstock, ores, additives, and refractory bricks used in metallurgical and gasification processes. In this work, gaseous P interactions with Pt–Rh (Rh = 6 and 30 wt%) alloys were isothermally investigated at 1012° C in situ using a customized environmental white light/confocal scanning laser microscope. Changes in microstructure and P-diffusion into the Pt–Rh alloys are discussed based on real-time images recorded during the exposure tests and electron probe microscopy analysis from the quenched samples.
Anna Nakano, Jinichiro Nakano, James Bennett