Advanced Ceramic and Metallic Coating and Thin Film Materials for Energy and Environmental Applications

Advanced ceramics have gradually become an important part as the new and key materials in developing modern technologies, affecting the advancement and progress in industries. A series of excellent properties in advanced ceramics, specifically fine structure, such as superior strength and hardness, wear-resisting, corrosion resistance, high temperature resistant, conductive, insulation, magnetic, pervious to light, piezoelectric, ferroelectric, acousto-optic, semiconductor and superconductor, and biological compatibility are widely used in national defense, chemical industry, metallurgy, electronics, machinery, aviation, spaceflight, biomedicine, etc. Also, the development of advanced ceramics is a new growth point of national economy, and its status—research, application, and development, embodies a country as an important symbol of comprehensive strength of national economy. At present, the worldwide advanced ceramic technology is rapidly progressing, its application area is expanding, and the stable growth trend in market is obvious.

Coatings and thin film materials are employed in many different industrial fields for decades, mainly for protective purposes. This large experience provokes that, currently, a wide variety of technologies for preparation and characterization of these materials are available. Particularly, focusing on energy and environmental applications, three main film types can be distinguished: (1) materials with catalytic activity for hydrogen production, (2) membranes for hydrogen separation or CO₂ capture, and (3) coatings for some specific fuel cell components. Membranes are especially relevant for hydrogen separation from other gases after the production unit or combining both production and separation steps in a unique equipment, the membrane reactor. The last case represents a significant advance in terms of process intensification, increasing the hydrogen production rate with a high purity and saving costs. In the last years, the relevance of these membrane materials has significantly increased, as can be denoted by the large number of published manuscripts in indexed scientific journals of high impact. In this context, this chapter summarizes the main advances in thin film membranes towards energy and environmental applications, including both preparation strategies and the most common characterization techniques. The production of all these thin films, independently of the particular application, can be carried out by different physical-chemical alternatives such as Sol–Gel methods, Electrodeposition, Electroless Plating, Physical Vapor Deposition, Chemical Vapor Deposition, Atomic Layer Deposition, or Molecular Beam Epitaxy, achieving thicknesses ranged from the nanometer scale to some microns. Each technique presents advantages and disadvantages that have to be taken into account for final applications. Moreover, the structure of the film should also be considered, being possible to distinguish amorphous or crystalline materials. All these films, independently of the composition, structure, or production technique, are usually prepared over a substrate material. Thus, the original coating surface properties can affect in a significant grade to the final properties of the film and many researchers focus their efforts on studying these effects and developing new strategies to improve the final quality of films in terms of homogeneity, thickness reduction, thermal and mechanical resistance, and adherence.

Metallic nanoparticle arrays which exhibit magnetic moments are a promising platform for the electrically and thermally conductive micro- and nanoscale structures. Real-world application fields include biomedical engineering, data storage, and nonlinear optics. In order to capitalize on major natural energy sources, such as solar and wind energies, efficient methods of energy storage must be developed. Recently, attention has been given to Latent Heat Storage (LHS) devices which utilize Phase Change Materials (PCMs) due to their low cost, low toxicity, and high engineering versatility, as candidates for efficient, cost-effective methods of thermal energy storage [1, 2]. One promising work to develop a LHS device utilizes parafin as a PCM and incorporates a matrix of magnetically susceptible, thermally conductive nanorod frameworks which are self-assembled under an externally applied magnetic field. The assembly process to create the matrix is well documented; however, the prohibitive cost of the magnetic pads, fabricated by lithography processes makes large-scale production impractical [3–6].

Thermoelectric energy-conversion technology based on oxide materials offers promising advantages over “traditional” non-oxide and intermetallics systems due to higher stability of oxides at elevated temperatures and in various redox conditions, high natural abundance and favourable environmental issues. Oxides also possess a unique defect chemistry, which can be precisely controlled by external redox conditions and redox-sensitive substitutions. Donor-substituted strontium titanate SrTiO₃ represents a family of promising n-type thermoelectric materials, with specific electronic structure tunable via introduction of structural defects, and prevailing lattice contribution to the thermal transport, enabling various lattice engineering approaches to suppress the thermal conductivity. Based on review of the recently published research results, this chapter aims to demonstrate how, through controlled defect chemistry engineering in SrTiO₃-based materials, one can tune the thermoelectric performance, breaking the coupling between thermal and electrical properties. The approach is based on compositional design in model systems, where prevailing defect types are shifted from extended oxygen-rich planes to oxygen vacancies, accompanied by presence of the A-site cationic deficiency. The contributions from various defects in the crystal lattice into electronic and thermal transport are demonstrated and discussed. The concept represents particular interest for thermoelectric films and superlattices based on strontium titanate, where introduction of specific defect types with potential impact on thermoelectric performance can be achieved in easier and/or more controllable manner.

Thin films solar cells (TFSCs) coated from different types of inks have yielded best efficiencies from 8 to ~13 %. This review depicts a specific group of non-vacuum methods for depositing kesterite Cu₂ZnSnS₄ (CZTS) solar cell absorber, which we characterized as direct ink coating (DIC) technique. The main objective of this chapter is to review the CZTS inks prepared by microwave process technique. A number of techniques including, hot injection method, solvo-thermal process, sonochemical and microwave-assisted route have been employed to synthesized CZTS ink. However, microwave is a rapid and single step process which has the potential to yield high-quality CZTS nanoparticle ink within minutes. CZTS films have been coated with different structures using such inks. Different properties of CZTS films such as, structural, compositional, optical, electrical and photovoltaic have also been reviewed. The properties of the TFSCs are discussed in the context of the processing techniques resulting in complete devices.

Solid oxide fuel cells (SOFCs) are promising power generation systems that electrochemically convert chemical energy into electrical energy with little or no emission of pollutants [1–3]. Moreover, a high-temperature fuel cell has many advantages such as a high efficiency and fuel flexibility in comparison with a low-temperature fuel cell. For these reasons, a considerable amount of attention has been paid to SOFCs in recent years for application to medium- to large-scale power generation and combined heat and power (CHP).

Solid-phase microextraction (SPME) is a non-exhaustive extraction and preconcentration technique based on the partitioning of the compounds present in a sample to a sorbent material. The sorbent material is immobilized onto the surface of a solid support, forming a SPME fiber of roughly 1 cm long and few micrometers of thickness. This microextraction approach is simple, solvent-free, fast, portable, it provides high preconcentration factors, and it can be automated easily. The main disadvantage of SPME is linked to the relatively low number of fibers commercially available, which limits the selectivity and applicability of this extraction method. In this sense, current trends are focused on the development of novel sorbent coatings for SPME. Among novel materials explored up-to-date, metal-based coatings have been successfully exploited in environmental analysis. They are characterized by high mechanical, chemical and thermal stability, ease of preparation and enhanced extraction performance.

This book chapter summarizes different approaches for modeling thin film solar cells. Particular attention will be given to kesterite solar cells as recently have emerged as promising candidates for replacing CdTe and CIGS technology. So far, only few theoretical works have been proposed to understand high V_oc deficit. However, most of these, consider transport mechanisms such as diffusion, radiative and non-radiative recombinations which are not able to explain experimental data reported for solar cells with the highest efficiencies. Currently, only two approaches have been able to reproduce experimental data accurately, one is by considering the effect of potential fluctuations (band-tailing) and the other is by means of tunneling mechanisms assisted by defects along with losses at kesterite/buffer interface. Advantages and disadvantages of each modeling method are presented and discussed.