Oxide Ceramics Research Articles

Way to a Library of Ti-Series Oxide Nanofiber Sponges that are Highly Stretchable, Compressible, and Bendable.

Ti-series oxide ceramics in the form of aerogels, such as TiO2, SrTiO3, BaTiO3, and CaCu3Ti4O12, hold tremendous potential as functional materials owing to their excellent optical, dielectric, and catalytic properties. Unfortunately, these inorganic aerogels are usually brittle and prone to pulverization owing to weak inter-particulate interactions, resulting in restricted application performance and serious health risks. Herein, a novel strategy is reported to synthesize an elastic form of an aerogel-like, highly porous structure, in which activity-switchable Ti-series oxide sols transform from the metastable state to the active state during electrospinning, resulting in condensation and solidification at the whipping stage to obtain curled nanofibers. These curled nanofibers are further entangled when flying in the air to form a physically interlocked, elastic network mimicking the microstructure of high-elasticity hydrogels. This strategy provides a library of Ti-series oxide nanofiber sponges with unprecedented stretchability, compressibility, and bendability, possessing extensive opportunities for greener, safer, and broader applications as integrated or wearable functional devices. As a proof-of-concept demonstration, a new, elastic form of TiO2, composed of both "white" and "black" TiO2 nanofiber sponges, is constructed as spontaneous air-conditioning textiles in smart clothing, buildings, and vehicles, with unique bidirectional regulation of radiative cooling in summer and solar heating in winter.

Enhanced Performance of Solid Polymer Electrolyte Separator Lithium Battery with Cellulose Acetate From Empty Palm Fruit Bunch Coated Al2O3-Polyacrylic Acid

As lithium battery technology improves, it becomes more important to have solid polymer electrolyte dividers that work better. The objective of this study is to enhance the efficiency of solid polymer electrolyte separators in lithium batteries. This research aims to expand the limits of innovation in hybrid separator development by utilizing empty palm fruit bunches (OPFEB) as a plentiful source of cellulose acetate. This approach enhances ion transfer by increasing the number of pores in the separator. However, there are challenges to achieving the desired levels of optimal ionic conductivity. In order to address these constraints, this study presents a novel Al2O3-PAA inert ceramic oxide coating treatment that is applied to the separator by a spin coating technique. An electron microscope was utilized to observe the pore structure of the separator. Additionally, the separator underwent physical, mechanical, thermal, and cyclic voltammetry tests. The findings of this research indicate a significant increase in the physical properties, particularly the porosity and mechanical strength. The thermal shrinkage of the Al2O3-PAA coated separator is below 10% when exposed to a temperature of 140 oC for 30 minutes. The Cyclic Voltammetry test results demonstrate a pronounced loop curve, indicating an improvement in the ionic conductivity of the Al2O3-PAA coated separator. The findings of this study provide a method to enhance the efficiency of separator performance at high temperatures while maintaining safety and long battery life.

Comparison of Dental Zirconium Oxide Ceramics Produced Using Additive and Removal Technology for Prosthodontics and Restorative Dentistry-Strength and Surface Tests: An In Vitro Study.

The aim of this in vitro study was to determine the mechanical and functional properties of zirconium oxide ceramics made using 3D printing technology and ceramics produced using conventional dental milling machines. Forty zirconia samples were prepared for this study: the control group consisted of 20 samples made using milling technology, and the test group consisted of 20 samples made using 3D printing technology. Their surface parameters were measured, and then their mechanical parameters were checked and compared. Density, hardness, flexural strength and compressive strength were tested by performing appropriate in vitro tests. After the strength tests, a comparative analysis of the geometric structure of the surfaces of both materials was performed again. Student's t-test was used to evaluate the results (p < 0.01). Both ceramics show comparable values of mechanical parameters, and the differences are not statistically significant. The geometric structure of the sample surfaces looks very similar. Only minor changes in the structure near the crack were observed in the AM group. Ceramics made using additive technology have similar mechanical and surface parameters to milled zirconium oxide, which is one of the arguments for the introduction of this material into clinical practice. This in vitro study has shown that this ceramic can compete with zirconium made using CAD/CAM (Computer-Aided Design and Computer-Aided Manufacturing) methods.

Fe-N-C Catalysts Synthesized on Conductive Non-Carbon Support Materials for Improved PEMFC Durability

Global energy demand will be continuously rising in the foreseeable future. To mitigate the results of climate change it is necessary to reduce the emittance of green house gasses. One very promising approach is to switch to hydrogen as energy carrier and use proton membrane fuel cells (PEMFCs) as the primary energy generation technology. Here, hydrogen and oxygen/air are used to directly generate electrical energy with only water as byproduct. Both reactions need to happen efficiently at the same time. The oxygen reduction reaction (ORR), however, is a very sluggish four-electron-reaction and needs efficient catalysts.The state-of-the-art catalyst is platinum but that is a very scarce and expensive metal. Hence, it is important to switch to precious-metal-group (PGM) free catalysts. In recent years, bio inspired iron-based Fe-N-C catalysts have been shown to approach ORR activities that are competitive with those of platinum, even though they need a higher catalyst loading than Pt to reach the desired current densities.1-3 Those catalysts feature single Fe atoms surrounded by four N atoms in graphitic carbon. The drawback of those materials is their lower stability compared to PGM materials. In a nutshell, the carbon matrix oxidizes during operation in PEMFCs, changing the morphology of the catalytic center and rendering it less active, or inactive, depending on the carbon oxidation extent. Demetallation phenomena are also possible, leaving a N4 cavity without metal cation center. It was shown recently by Wu et al.4 that it is possible to raise durability by adding an additional carbon layer on the catalyst. One alternative approach to reduce those degradations is to interface Fe-N4 sites with a carbon-free support. The targeted support material must be immune to corrosion in acid and withstand the typical ORR electrochemical potentials. It also has to be electrically conductive to facilitate electron transfers, both locally and on long scale.In this work, conductive ceramic metal oxide materials were investigated as possible alternative catalyst supports. Those materials are resistant to acid and can withstand prolonged potentials at operating conditions in PEMFCs. The conductivity is usually raised by doping, since many of those ceramics are semi-conductors. However, during the synthesis of the Fe-N-C catalysts, high temperatures are generally applied. Such treatments can be detrimental to the conductivity of the ceramics due to metal aggregation (in case of doped materials) and may also lead to morphological changes. A robust method to synthesize Fe-N-C catalysts is by mixing the separate Fe, N and C precursors and using optimized thermal treatment at high temperatures. They can be further pyrolyzed with ammonia to introduce defects and basicity into the structure, which leads to higher catalytic activity but even lower stability in acid medium. In this study, the effect of the pyrolysis conditions on conductive oxide materials was investigated with various characterization methods, e.g. x-ray diffraction, scanning electron microscopy and N2 sorption isotherms. This gives insights into the changes that happen during the thermal treatment and can be used to find optimal synthetic conditions to keep most desired parameters of the ceramics preserved or only minimally lowered. Several different approaches were used to combine Fe-N-C catalysts with conductive ceramic metal oxide materials. The resulting materials were characterized and tested with rotating disc electrode techniques and in PEM fuel cells for their ORR-activity and durability.(1) F. Jaouen et al., Nature Catalysis, 2022, 5, 311–323(2) H. A. Gasteiger et al., Science, 2009, 324, 48−49(3) L. Elbaz et al., ACS Applied Energy Materials 2022, 5 (7), 7997-8003(4) G. Wu et al., Nature Energy, 2022, 7, 652–663

Which Interfaces Matter Most? Variability in Grain Boundary Defect Chemistry and Conductivity in a Concentrated Solid Electrolyte

Inorganic solid electrolytes with fast ionic conductivity are critical components of fuel/electrolysis cells, all-solid-state batteries, membrane and separation reactors, sensors and other electrochemical devices. For example, solid oxygen ion (O2-) conductors are used in solid oxide fuel/electrolysis cells (SOFCs/SOECs) for high-efficiency conversion between chemical and electrical energy and chemical production from CO2. One major challenge in engineering such materials is the diminished grain boundary (GB) conductivity in polycrystalline oxide ceramics. This phenomenon, which was initially accredited to highly resistive silica-based glassy impurity phases, is attributed to the formation of intrinsic space charge layers (SCLs) directly adjacent to GB cores. The positive potential at the GB core (due to large concentrations of oxygen vacancies) results in a depletion of oxygen vacancies in the space charge layer as well as the segregation of charge-compensating acceptor solutes from grain interiors which ultimately reduces GB conductivity. Several strategies have been explored to improve GB conductivity by understanding and mitigating the SCL effects. While the standard Poisson–Boltzmann approach models the near-grain boundary defect behavior in dilute solid solutions and recent models by Mebane et al [1] and Virkant et al [2] incorporate the effects of defect-defect interactions (in concentrated solid solutions) and chemomechanical stress, respectively, there is yet to be a model developed that can predict individual GB conductivities in concentrated solid solutions based on direct experimental measurements of near-GB defect chemistry.Here, we present an experimental-computational framework that predicts which GBs in a polycrystalline electrolyte likely facilitate ionic conductivity. We developed a thermodynamic phase-field modeling framework and applied it to a model oxygen electrolyte Gd0.25Ce0.75O2-δ, wherein the GB-to-GB variability in defect concentrations (Gd3+ solutes, electrons localized at Ce3+, and oxygen vacancies) was measured microscopically using scanning transmission electron microscopy electron energy-loss spectroscopy (STEM EELS). These data were used to predict the GB-to-GB variability in cross-GB ionic conduction using a unique model, which prioritizes reproducing microscopically observed GB defect concentrations and considers defect-defect interactions in highly concentrated solid solutions, making the framework applicable to other technologically relevant solid electrolytes. Across the GBs studied, we revealed a non-monotonic relationship between depletion and GB conductivity, with the highest conductivity predicted for intermediate depletion amounts. This work lays the foundation for future experimental-computational research and advanced data-driven design of solid electrolytes needed for functional and energy storage/conversion devices.[1] D. S. Mebane, R. A. D. Souza, Energy & Environmental Science, 2015.[2] K. S. N. Vikrant, R. Edwin García, Energy & Environmental Science, 2018.[3] H. Vahidi, W.J. Bowman (Submitted). Acknowledgments HV and WJB acknowledge primary support from the UCI new faculty startup funding. This research was partially supported by the National Science Foundation Materials Research Science and Engineering Center program through the UC Irvine Center for Complex and Active Materials (DMR-2011967). We acknowledge the use of facilities and instrumentation at the UC Irvine Materials Research Institute (IMRI) supported in part by the same NSF MRSEC (DMR-2011967). AM, DM, and AC acknowledge funding from the NSF [WB1] [hv2] and the WVU MAE research department for the use of the Thorny Flat HPC Cluster for the numerical modeling work and computational resources.

High-pressure low-temperature densification of NASICON-based LATP electrolytes for solid-state lithium batteries

Ceramic oxides are promising solid electrolytes for Lithium metal solid-state batteries (SSBs) because of their high ionic conductivity and stability under ambient conditions. Nonetheless, the need for high-temperature densification approaches challenges their processability towards upscaling and their implementation into practical SSB devices. Here, we investigate a High-Pressure Low-Temperature (HPLT) processing technique for the densification of NASICON-based Li1+xAlxTi2-x(PO4)3 (LATP) solid electrolyte, providing an understanding of several key parameters such as temperature, pressure and time. Our results show that nanometric LATP can be densified using the HPLT technique at 200°C within 2 min delivering an ionic conductivity of 6.15×10−5 Scm−1, which is the highest reported value at this temperature without the addition of solvents. On the other hand, by combining HPLT with a short post-heat treatment at 700 or 800 °C for 1 hour, highly dense pellets with an ionic conductivity of 10−4 Scm−1 can be obtained. This represents a reduction of the densification temperature of 400°C compared to conventional high-temperature sintering and shows the potential of HPLT to overcome current densification constraints derived from the use of very high temperatures.

Hierarchical Hybrid Coatings with Drug-Eluting Capacity for Mg Alloy Biomaterials.

A hierarchical hybrid coating (HHC) comprising a ceramic oxide layer and two biodegradable polymeric (polycaprolactone, PCL) layers has been developed on Mg3Zn0.4Ca cast alloy in order to provide a controlled degradation rate and functionality by creating a favorable porous surface topography for cell adhesion. The inner, ceramic layer formed by plasma electrolytic oxidation (PEO) has been enriched in bioactive elements (Ca, P, Si). The intermediate PCL layer sealed the defect in the PEO layer and the outer microporous PCL layer loaded with the appropriate active molecule, thus providing drug-eluting capacity. Morphological, chemical, and biological characterizations of the manufactured coatings loaded with ciprofloxacin (CIP) and paracetamol (PAR) have been carried out. In vitro assays with cell lines relevant for cardiovascular implants and bone prosthesis (endothelial cells and premyoblasts) showed that the drug-loaded coating allows for cell proliferation and viability. The study of CIP and PAR cytotoxicity and release rate indicated that the porous PCL layer does not release concentrations detrimental to the cells. However, complete system assays revealed that corrosion behavior and increase of the pH negatively affects cell viability. H2 evolution during corrosion of Mg alloy substrate generates blisters in PCL layer that accelerate the corrosion locally in crevice microenvironment. A detailed mechanism of the system degradation is disclosed. The accelerated degradation of the developed system may present interest for its further adaptation to new cancer therapy strategies.

Effect of natural attapulgite mineral on microstructure, mechanical properties and tribological behaviors of in-situ TiB/Ti composite by SPS method

In this study, natural attapulgite (ATP) mineral powder was implanted into an in-situ synthesized TiB/Ti composite by the SPS method using Ti-Al-B-attapulgite raw powders to improve the tribological properties. The introduction of ATP improved the microstructure, mechanical properties, and tribological performance of the in-situ TiB-reinforced titanium matrix composite. The addition of 1 wt.% ATP powder has refined both the grain structure of the matrix and the size of the in-situ TiB, leading to the increase of 39.3% in matrix nanohardness and 31.4% in microhardness of the composite. During the friction process, dehydration reactions, group recombination, and tribochemical reactions occurred in the ATP minerals dispersed in the rubbing contact area of the composite, inducing the formation of a tribolayer with a smooth nanocrystalline film. The tribolayer is mainly composed of titanium oxides (TiO, TiO2, and Ti2O3), iron oxides (FeO, Fe2O3, and Fe3O4), ternary compounds (Al18B4O33 and Al2Ti7O15), oxide ceramics (Al2O3 and SiO2), solid lubricating phases (graphite and attapulgite), iron, and enstatite (MgSiO3). The nanocrystalline structure composed of FeO, Fe2O3, and TiO, as well as the strengthening effect of hard phases such as SiO2, MgSiO3, Al2O3, Al18B4O33, and Al2Ti7O15, endowed the tribolayer with a high hardness, good plasticity, and toughness. The exceptional mechanical properties and dispersed solid lubrication phases of the tribolayer resulted in the excellent tribological properties of the ATP-TiB/Ti composite.

Interatomic potentials for cubic zirconia and yttria-stabilized zirconia optimized by genetic algorithm

Yttria stabilized zirconia (YSZ) is an important engineering ceramic oxide used for various applications, including solid electrolytes in solid oxide fuel cells due to its high ionic conductivity. Accurate and computationally inexpensive interatomic potentials for cubic ZrO2 and YSZ are required to accommodate the large number of defect configurations originating from high concentrations of Y and oxygen vacancies and to statistically understand their properties in realistic time. In this study, a genetic algorithm has been used to optimize empirical interatomic potential parameters for cubic ZrO2 and 10Y2O3 mol% YSZ using energies, forces acting on atoms, and stresses generated by ab initio calculations as training data. The optimized potentials reproduce the structural, mechanical, and thermal properties as well as the ionic conduction properties more accurately than previously reported empirical interatomic potentials. The developed potentials will be useful for a statistical characterization of YSZ properties, combined with more accurate ab initio calculations.

Review: recent progress in aluminum matrix composites reinforced by in situ oxide ceramics

Review: recent progress in aluminum matrix composites reinforced by in situ oxide ceramics

Room‐Temperature Synthesis of a Compositionally Complex Rare‐Earth Carbonate Hydroxide and its Conversion into a Bixbyite‐Type High‐Entropy Sesquioxide

AbstractIn the present work, the solvent‐deficient synthesis of the high‐entropy rare‐earth carbonate hydroxide RE(CO3)(OH) (RE=La, Ce, Pr, Nd, Sm, and Gd) and its thermal conversion into bixbyite‐type sesquioxide RE2O3 are reported for the first time. The high‐entropy rare earth carbonate hydroxide was prepared via mechanochemical reaction of the corresponding metal nitrate hydrates with ammonium hydrogen carbonate followed by the removal of the NH4NO3 by‐product. Calcination of the carbonate hydroxide precursor in ambient atmosphere at temperatures in the range from 500 to 1000 °C led to the high‐entropy rare earth sesquioxide which exhibited a bixbyite‐type structure ( ) independent of the calcination temperature. Transmission electron microscopy (TEM) investigation revealed the homogeneous distribution of all six rare earth cations in the high‐entropy sesquioxide lattice, however, with some compositional variation between individual grains. The bixbyite‐type structure may be considered as the result of heavy doping of the fluorite‐type CeO2 lattice with the other rare earth cations, which leads to a high concentration of oxygen vacancies, as revealed by electron diffraction and Raman spectroscopy data. The solvent‐deficient synthesis method used in the present study is considered as a valuable, straightforward and easily up‐scalable method to synthesize compositionally complex oxide ceramics.

Revealing the Deposition Mechanism of the Powder Aerosol Deposition Method Using Ceramic Oxide Core-Shell Particles.

The powder aerosol deposition (PAD) method is a process to manufacture ceramic films completely at room temperature. Since the first reports by Akedo in the late 1990s, much research has been conducted to reveal the exact mechanism of the deposition process. However, it is still not fully understood. This work tackles this challenge using core-shell particles. Two coated oxides, Al2 O3 core with a SiO2 shell andLiNi0.6 Mn0.2 Co0.2 O2 core with a LiNbO3 shell, are investigated. Initially, the element ratios Al:Si and Ni:Nb of the powder are determined by energy-dispersive X-ray spectroscopy (EDX). In a second step, the change in the element ratios of Al:Si and Ni:Nb after deposition is investigated. The element ratios from powder to film strongly shift toward the shell elements, indicating that the particles fracture and only the outer parts of the particles are deposited. In the last step, this work investigates cross-sections of the deposited films with scanning transmission electron microscopy (STEM combined with EDX and an energy-selective back-scattered electron (EsB) detector to unveil the element distribution within the film itself. Therefore, the following overall picture emerges: particles impact on the substrate or on previously deposited particle, fracture, and only a small part of the impacting particles that originate from the outer part of the impacting particle gets deposited.

Constructing the cationic rattling effect to realize the adjustability of the temperature coefficient in Nd2-xSmxO3 microwave dielectric ceramics

In this work, a series of dense Nd2-xSmxO3 (x = 0.0 − 2.0) ceramics were synthesized using a solid-state reaction method at 1400 − 1575 °C. The ceramics were confirmed to be hexagonal at x < 0.5, and a monoclinic phase was observed in the ceramics when x ≥ 1.0. The microwave dielectric properties of Nd2-xSmxO3 (x = 0.0 − 2.0) are εr = 19.48 − 22.96, Q×f = 48,447 (x = 0.0) − 21,363 (x = 0.5) − 34,761GHz (x = 2.0), and τf = -43.0 − +34.1 ppm/℃. The bond valence theory calculation demonstrates that the change of τf value from negative to positive is mainly affected by the rattling of Sm3+. Moreover, the series of ceramics were exposed to the air for different days to study the problem of rare earth oxide ceramics quickly decomposing in the air and found that Nd0.5Sm1.5O3 ceramic shows stable structure and performance.

Organosilicon-grafted silica nanoparticles for vat photopolymerization: Evolution from organic/inorganic hybrid materials to ceramics

Three-dimensional (3D) printing ceramics based on vat photopolymerization (VPP) have attracted increasing interest in recent years because of their intrinsic properties and a wide range of potential applications. To overcome the drawbacks of traditional printing slurries, such as weak interlayer bonding and high viscosity, a series of organosilicon-grafted silica nanoparticles with a core/shell structure were prepared. These grafted nanoparticles possess small size (around 20 nm), good dispersion in photoactive diluents, and excellent photoactivity. Based on them, organic/inorganic hybrid materials with uniform microstructure and excellent mechanical performance (compressive stress 235.4 ± 33.2 MPa) were obtained by the vat photopolymerization technique. Further, oxide ceramics and carbide/oxide ceramic composites (compressive stress around 15 MPa) were prepared by calcination in air and argon, respectively. This study demonstrates the synthesis of organic/inorganic hybrid silica nanoparticles with good photoactivity, and their promising application as 3D-printable raw materials.

Numerical Modeling of Residual Stresses and Fracture Strengths of Ba0.5Sr0.5Co0.8Fe0.2O3−δ in Reactive Air Brazed Joints

Reactive Air Brazing (RAB) enables the joining of vacuum-sensitive oxide ceramics, such as Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF), to metals in a one-step process. However, damage may form in ceramic or joint during RAB. In this work, experimental microstructure characterization, measurement, and prediction of local material properties using finite element analysis were combined to enlighten these damage mechanisms, which are currently not well understood. Micromechanical simulations were performed using representative volume elements. Cooling simulations indicate that small-sized CuO precipitations are most likely to cause crack initiation in BSCF during cooling. The ball-on-three-balls experiment with porous BSCF samples was analyzed numerically to determine the values of temperature-dependent BSCF fracture stresses. The inversely calibrated fracture stresses in the bulk BSCF phase are underestimated, and true values should be quite high, according to an extreme value analysis of pore diameters.

Thermal insulating and mechanical properties of high entropy pyrochlore oxide ceramic with hierarchical porous structures

High entropy pyrochlore oxide ceramics with hierarchical porous structures were prepared by coprecipitation, freeze-casting, and press-less sintering methods. In the fabrication process, a Ca2+-crosslinked alginate network was utilized to control the growth of ice crystals, resulting in uniformly dispersed micro-scale circular pores. The submicron pores were formed in the high entropy oxide ceramic during the press-less sintering method. The XRD was employed to explore the phase of the high entropy pyrochlore oxide ceramic. The porous structures of high-entropy ceramic were analyzed through the discussion of microstructure and pore size distribution. The tests show that the prepared series of ceramics with high porosity have optional compressive strength and thermal insulation properties. The high entropy oxide ceramic (La0.2Y0.2Gd0.2Sm0.2Nd0.2)2Zr2O7 with hierarchical porous structures possess moderate density (0.4 g/cm3) and low thermal conductivity (0.04 W m−1 K−1). The excellent comprehensive performance makes the porous high entropy oxide ceramic could be applied as a thermal insulating material.

Modified BBFTO ceramic oxide with high dielectric constant and low loss-tangent for possible electronic applications

In this report, a complex barium titanate ceramic oxide of the form BaBi1.6Fe0.4TiO6 was prepared by the solid-state casting process. More Bi3+ percentage was selected to boost the dielectric and ferroelectric effects, while lowering the Fe3+ content could minimize the leakage current and consequently, the dielectric loss (tanδ). The X-ray diffraction (XRD) data suggests an establishment of monoclinic distortion (P21/c) of smaller mean crystallite size (∼40 nm) using the Debye-Scherrer formula. The compound exhibits dielectric values, such as ɛr ∼ 771, and relatively low loss, tanδ ∼ 0.017 at the ambient experimental conditions. Thus, the material can be incorporated into different electronic devices where higher dielectric constant and lower losses are essential, for example, multi-layered ceramic capacitors, transmission lines, and gate dielectrics. The AC-conductivity essence of the compound follows Jonscher’s power law as well as Arrhenius relation. The PE hysteresis loop was traced at different conditions with a function of the incident electric field in the ambient atmospheric conditions. The outcome of this study revealed that the material has remanent polarization hence suggesting a ferroelectric effect with less hysteresis loss; therefore, it could be useful in memory storage devices.

Mechanochemical synthesis of nanostructured and composite oxide ceramics: From mechanisms to tailored properties

AbstractMechanochemical synthesis is a technology formed in the 1950s. By applying mechanical energy, mechanochemical synthesis stimulates chemical reactions, causing structural and phase changes and enabling difficult or otherwise impossible reactions to occur. Mechanochemical reactions are relatively safe, clean and efficient. At present, the synthesis of oxide ceramic materials by mechanochemical methods has attracted widespread attention. In the production of oxide ceramic materials, the characteristics of ceramic powder have a certain influence on the molding, sintering, microstructure, and mechanical properties of subsequent ceramics. In this paper, the research progress of mechanical chemistry in the synthesis of nanostructures and composite oxide ceramic powders is reviewed. The effects of process parameters such as ball milling time, speed, atmosphere, grinding media, additives, and ball‐to‐powder ratio on reaction kinetics, phase formation, and powder properties are summarized. In addition, challenges and opportunities for ceramic powder synthesis are also discussed.

Efficient single-step Cool-SPS processing of Mn3O4 ceramics at 400 °C with persistent magnetodielectric coupling

Spinel type Mn3O4 oxide ceramics possess intriguing magnetodielectric properties, but traditional processing routes can be frustrated by limited high temperature phase stability. Using a low temperature (≤400 °C) electric field assisted processing route (Cool-SPS), a highly cohesive Mn3O4 ceramic is achieved. Reactive manganese oxide-hydroxide precursor powder is converted into the targeted Mn3O4 with a single step process under strategically selected conditions. Detailed X-ray diffraction studies, including variable temperature and atmosphere measurements, plus in-situ monitoring of processing parameters, have been combined to map and optimize SPS processing parameters. The microstructure evolution from precursor to ceramic was examined by electron microscopy, while extensive magnetic and dielectric measurements were performed to study the complex physical behavior of Mn3O4 at low temperature (<43 K). The efficacy of this Cool-SPS processing approach for Mn3O4 is demonstrated by the observed ceramic properties, including a hysteretic magnetic-field dependent dielectric response which supports the existence of a magnetoelectric coupling.

Preceramic Polymers for Additive Manufacturing of Silicate Ceramics.

The utilization of preceramic polymers (PCPs) to produce both oxide and non-oxide ceramics has caught significant interest, owing to their exceptional characteristics. Diverse types of polymer-derived ceramics (PDCs) synthesized by using various PCPs have demonstrated remarkable characteristics such as exceptional thermal stability, resistance to corrosion and oxidation at elevated temperatures, biocompatibility, and notable dielectric properties, among others. The application of additive manufacturing techniques to produce PDCs opens up new opportunities for manufacturing complex and unconventional ceramic structures with complex designs that might be challenging or impossible to achieve using traditional manufacturing methods. This is particularly advantageous in industries like aerospace, automotive, and electronics. In this review, various categories of preceramic polymers employed in the synthesis of polymer-derived ceramics are discussed, with a particular focus on the utilization of polysiloxane and polysilsesquioxanes to generate silicate ceramics. Further, diverse additive manufacturing techniques adopted for the fabrication of polymer-derived silicate ceramics are described.