Synthesis Of Ceramic Powders Research Articles

Synthesis of high-entropy Ti-Zr-Nb-Hf-Ta carbides and carbonitrides in high-speed arc discharge plasma jet

The interest in high-entropy materials has increased rapidly in recent decades due to their applications in various fields such as environmental barrier coatings, superhard and wear resistant coatings, nuclear energy, batteries, catalysts, thermoelectrics, supercapacitors, biocompatible structures, and microelectronics. In the present work, comprehensive theoretical and experimental studies are carried out to discover a new way to prepare high-entropy ceramic nanopowders of carbides and carbonitrides of IV-V transition metals. The possibility of (TiZrNbHfTa)CxNy formation is investigated using both ab initio and machine learning approaches. The chosen single-stage plasma dynamic technique allowed us to synthesize high-entropy carbide TiZrNbHfTaC5 and the corresponding carbonitrides (N up to 8 wt%) in the form of single-crystalline nanoparticles. By varying the experimental system conditions, we demonstrate not only the production of pure powders, but also the ability to apply different precursors, including pure metals and their oxides. The presented technique provides a simple and universal way to produce high-entropy nanomaterials and opens the door to the synthesis of many functional ceramic powders composed of other carbonitrides with selective nitrogen content.

Synthesis and Band Gap Characterization of High-Entropy Ceramic Powders

This manuscript presents a comprehensive exploration of the band gap structure of (CoCrFeNiMn)3O4 powders through a series of experimental investigations. The combined use of optical techniques and X-ray photoelectron spectroscopy in this study leads to a comprehensive characterization of the band gap structure in (CoCrFeNiMn)3O4 powders. The findings contribute to the understanding of this material’s electronic properties and pave the way for potential applications in electronic and optical 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.

Electrophysical Properties of PZT-Type Ceramics Obtained by Two Sintering Methods

This study demonstrates the impact of two sintering techniques on the fundamental properties of doped PZT-type ceramic materials (with Mn4+, Sb3+, Gd3+, and W6+), with the general chemical formula Pb(Zr0.49Ti0.51)0.94Mn0.021Sb0.016Gd0.012W0.012O3. The synthesis of ceramic powders was carried out through the calcination method. Two different methods were used in the final sintering process: (i) pressureless sintering (PS) and (ii) hot pressing (HP). The PZT-type ceramics were subjected to electrophysical measurements, encompassing various analyses such as X-ray diffraction (XRD), microstructure (scanning electron microscopy (SEM)), ferroelectric and dielectric properties, and DC electrical conductivity. The analysis of the crystal structure at room temperature showed that the material belongs to the perovskite structure from the tetragonal phase (P4mm space group) without foreign phases. Both sintering methods ensure obtaining the material with appropriate dielectric and ferroelectric parameters, and the tests carried out verified that the ceramic materials have a diverse range of parameters appropriate for use in micromechatronic and microelectronic applications. The obtained ceramic material has high permittivity values, low dielectric loss tangent values, and high resistance. At room temperature, the ceramic samples’ P-E hysteresis loops do not saturate at a field of 3.5 kV/mm (Pm maximum polarization is in the range from 12.24 to 13.47 μC/cm2). However, at higher temperatures, the P-E hysteresis loops become highly saturated, and, at 110 °C, the Pm maximum polarization values are in the range from 28.02 to 30.83 μC/cm2.

Pressureless sintering behaviour of Al2O3/ZrO2 amorphous/solid solution powder with ultra-fine ZrO2 nanoparticle precipitation

In this paper, we present a novel Al2O3/ZrO2 amorphous/solid solution powder that exhibits a low pressureless sintering temperature and can precipitate numerous ultra-fine ZrO2 nanoparticles. The powder was prepared by combustion synthesis and bead milling. A series of characterizations were conducted to investigate the sintering behaviour and sintering activation energy of the as-synthesized powder. Commercial Al2O3 and ZrO2 powders with similar sizes were mixed and served as the referential sample. The experimental results and analysis indicated that the sintering activation energy and temperature of the Al2O3/ZrO2 amorphous/solid solution powder were much lower than that of the commercial powder due to its metastable state and lattice defects, its sintering activation energy and temperature were much lower than that of the commercial powder. As a result, its sintering temperature decreased to only 1400 °C, more than 100 °C lower than the commercial powder. Furthermore, we observed that the solid solution could decompose during sintering, forming a significant number of ultra-fine ZrO2 nanoparticles measuring 5 nm. These nanoparticles effectively enhanced the mechanical performance of the ceramic by shifting the fracture mode from intergranular to transgranular. Consequently, the fracture toughness and bending strength of the ceramic could reach up to 6.03 MPa m0.5 and 525 MPa, respectively, which is much higher than that of the ceramic sintered with commercial powder. The insights gained from this study may be of assistance to the synthesis of high sintering activity ceramic powders and nanocomposite ceramics.

Solid-state calcination and synthesis of homogeneous strontium zirconate by slip casting

Solid-state synthesis of strontium zirconate (SrZrO3) at 1200 °C by slip casting is proposed as an alternative to the traditional pellet pressing method to improve accessibility and efficiency in laboratory settings. Powders prepared through both methods were characterized for particle size, morphology, chemical purity, and sintering performance. It was found that the slip casting adaptation produced orthorhombic strontium zirconate with similar particle or microstructural characteristics to pellet pressing. Furthermore, production efficiency in a laboratory setting compared to traditional pellet method was significantly increased. The results reported here indicate that slip casting is a suitable alternative method for solid-state synthesis of ceramic powders, particularly in laboratory settings where access to industrial equipment is limited. Synthesis of SrZrO3 by slip casting allowed 70% reduction in person-hours compared to a pellet press approach in a manual laboratory setting.

NdB6 ceramic nanoparticles: First principles calculations, mechanochemical synthesis and strain engineering

Borides are usually hard and brittle materials; however, we report the synthesis of superplastic nanostructured NdB6 ceramic powders, counter to the conventional wisdom that borides are always brittle. We investigate that through strain engineering, NdB6 can be made extremely ductile if the lattice is compressively strained and highly defected, based on transmission electron microscopy (TEM) and density functional theory (DFT) calculations. In this study, the synthesis conditions were designed based on CALPHAD modelling, and the superplastic NdB6 powders were successfully obtained through mechanochemical synthesis (MCS) of Nd2O3, B2O3 and Mg initial materials in a high-energy ball mill. Following MCS, the powders were purified in a hydrochloric acid (HCl) containing aqueous solution in order to leach out MgO by-product. The purified powders were characterized using X-ray diffractometry (XRD), Helium (He) gas pycnometry, scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), particle size analysis (PSA) and magnetometry techniques, which demonstrated NdB6 nanoparticles with an average particle size of 118 nm belonging paramagnetic behavior at cryogenic temperatures. DFT calculations have been carried out through to investigate the structural, mechanical, electronic, optical, thermodynamic and magnetic properties of NdB6. The impact of various defects was examined, which revealed the significance of boron vacancies and compressive strains in the superplastic form of NdB6.

Synthesis and Characterization of High-Entropy Dawsonite-Type Structures.

High-entropy hydroxides are an emerging subcategory of high-entropy materials (HEMs), not only because they can serve as tailorable precursors to high-entropy oxides (HEOs) but also because they can have unique high-entropy properties themselves. Many hydroxide crystal structures that are important for various applications are yet to be studied within the context of high-entropy materials, and it is unknown if they can take a high-entropy form (typically five or more incorporated cations). One such material is the dawsonite-type structure, which is a material with applications in both catalysis and ceramics. This work focuses on the adaptation of a dawsonite-type structure (NH4M(OH)2CO3) into a high-entropy material. Through a coprecipitation synthesis method, dawsonite-type materials readily took a high-entropy form with five cations that were equimolar and homogeneously distributed. The specific chemistries investigated were Al, Cr, Fe, and Ga with a fifth cation that was varied with increasing ionic radius (In, Er, Ho, Y, Eu, Ce, La). High-entropy dawsonites also exhibit the ″memory effects″ of non-high-entropy dawsonites. This work extends the field of high-entropy materials to include a structure that can serve as a material platform for the synthesis of high-entropy catalytic materials and ceramic powders.

Molten salt dynamic sealing synthesis of MAX phases (Ti3AlC2, Ti3SiC2 et al.) powder in air

Since the synthesis of non-oxidized ceramic and alloy powders requires both high temperature and oxygen insulation conditions, here we demonstrate a cost-efficient molten salt sealing/shielded synthesis method with dynamic gas tightness. Compared to conventional synthesis method, it can prevent the loss of reaction materials at high temperature, cut off the connection between reacting material and outside air, and does not require long-time ball milling mixing treatment or provision of applied pressing before or during heating. Only low-cost salts (e.g., NaCl, KCl), a few minutes of raw material mixing, and regular heating molds are required to obtain high-purity (>96 wt%), micron-sized Ti 3 AlC 2 and Ti 3 SiC 2 powders with narrow size distribution, which significantly decreased the complexity and production costs in the synthesis process. The effect of temperature and raw material content on the products were investigated. The mechanism of diffusion reaction between reactants in molten salt environment was analyzed. The new method developed here was also applicable to Ti 2 AlC, V 2 AlC and Cr 2 AlC MAX phases, as well as provided new ideas for the preparation of other MXenes precursors with certain stoichiometric ratios, air-sensitive materials and nanopowders.

Development and Characterizations of Novel Aqueous-Based Ceramic Inks for Inkjet Printing.

Stable rheological properties of ceramic ink are a key requirement for inkjet printing (IJP), which should be satisfied in terms of the Reynolds and Weber numbers. In this paper, the reverse microemulsion was introduced for the synthesis of monodispersed nanosized ceramic powders, and the average size was less than 100 nm. A comparison of two different dispersants, i.e., polyacrylic ammonium (PAANH4) and polyacrylic aid (PAA), revealed that the former exerted a good dispersion effect on the ceramic ink. The sedimentation ratio, zeta potential, surface tension, viscosity, and density of the inks were measured, and the Reynolds and Weber numbers, as well as Z value, were calculated. A stable, homogeneous, and high solid loading (20 wt%) ceramic ink could be achieved after aging for a period of 72 h. Finally, the ceramic inks showed the desired printable property in the inkjet printing process. Combining inkjet printing technology with a sintering process, Ni-Mn-O films have the potential to monitor temperature and humidity parameters for intelligent wearable devices.

Co-synthesis of zirconium boride/silicide/oxide composite powders by magnesiothermic reduction

This study uses a magnesiothermic reduction method to investigate the co-synthesis of zirconium boride, silicides, and oxide powder composites using ZrO2, B2O3, Si, and Mg initial powders. The synthesis of high-temperature ceramic powders is examined through milling durations, reduction temperatures, and excess magnesium addition. Thermochemical analysis of probable reaction products was conducted by the Factsage software. According to the results, the thermochemical predictions and resultant powder phases showed good coherency. High-energy milling has a significant effect on the formation of the zirconium boride phase after annealing. However, extended milling time and higher annealing temperature have no significant effects on the composition of the constituted composite powders according to the X-ray diffraction results. An annealing temperature of 600 ºC was enough to obtain ZrB2-based ceramic composite powders. In the final powder phases, the excess magnesium addition to the stoichiometric displays an important feature. After the milling, annealing, and leaching procedure, the stoichiometric powder composition comprises ZrB2, ZrSi, ZrSi2, ZrO2, and MgSiO2, and excess Mg added powders have the ZrB2, ZrSi, ZrSi2, ZrO2 phases in their structure. Scanning electron microscopy analysis was utilized to observe the morphologies of the powders throughout each step of the synthesis procedure and revealed the finely structured morphology of synthesized powders.

Synthesis and characterisation of novel single-phase HfCxN1-x ceramic powders

Hafnium carbonitride (HfCxN1-x) powders were successfully synthesised from a mixture of Hf, C, and HfN powders using the solid-reaction method at 2400 °C for 30 min in a nitrogen atmosphere. The basic properties of the as-prepared HfCxN1-x powders, including the particle size, phase composition, microstructure, morphology, chemical bond composition and crystal structure were analysed using X-Ray diffraction, scanning electron microscopy, X-Ray photoelectron spectroscopy, and transmission electron microscopy. The as-prepared HfCxN1-x powders had a singlecrystalline structure of metal carbonitride and simultaneously possessed high purity. The mean particle size of the as-prepared HfCxN1-x powders was approximately 2 μm, and the chemical composition ratios of Hf, C, and N in the as-prepared powder samples were close to the stoichiometric values. These elements were evenly distributed in the powder samples. The results confirmed that the powders consisted of Hf–C and Hf–N bonds with a Hf/(C + N) ratio of approximately 1. The HfCxN1-x (x = 0.7, 0.6, 0.5, 0.4, 0.3) powders had a cubic crystal structures.

Synthesis and densification of BaZrO3 ceramics by reactive cold sintering of Ba(OH)2⋅8H2O-Zr(OH)4 powders

Reactive cold sintering (RCS) is a combination of a low-temperature reaction and the cold sintering process, and it is used for the direct synthesis and simultaneous consolidation of ceramic powders. Here, we investigated RCS of BaZrO3 through the reaction between Ba(OH)2⋅8H2O and Zr(OH)4, and obtained pure BaZrO3 compacts with a relative density of ∼92% under the conditions of Zr(OH)4 ball-milling for 30 min, Ba/Zr ratio of 1.15, and holding a temperature of 350 °C for 60 min. The effects of processing parameters on the phase structure, relative density, microstructure evolution, and dielectric property of the BaZrO3 bulk were studied in detail. The results suggest that the synthesis and densification of BaZrO3 bulk in the RCS process involved the steps of dissolution, reaction, agglomeration, collapse, and densification. The present study extends the applicability of RCS to the preparation of high-density perovskite ceramics with nanograins.

High‐entropy transparent ceramics: Review of potential candidates and recently studied cases

AbstractHigh‐entropy ceramics have been widely explored and extensively studied since the first demonstration of the configuration entropy stabilized reversible transitions between multiple and single phases by Rost et al. in 2015. Most of the current research on high‐entropy ceramics has focused on properties like thermal conductivity, thermoelectricity, structures, and others. Some recent studies have extended the high‐entropy concept to the field of transparent ceramics. We reviewed these papers and proposed four potential ceramics groups for high‐entropy transparent ceramics including fluoride ceramics, fluorite‐deficient and/or ordered pyrochlore A2B2O7 ceramics, garnet ceramics, and sesquioxide ceramics. In this article, we review ceramic powder synthesis, the fabrication of transparent ceramics, high‐entropy ceramics, and limited cases of high‐entropy transparent ceramics for each category. High‐entropy transparent ceramics with diverse compositions and structures will provide more possibilities for functional transparent ceramics in the future.

Methods of synthesis of yttrium-aluminum granate powders for producing transparent ceramics

The work examines the latest research on the synthesis of ceramic powders based on yttrium-aluminum garnet. The advantages and disadvantages of various methods are given. The work highlights the achievements and results achieved by researchers in this field at the moment.

Synthesis of novel single-phase high-entropy metal carbonitride ceramic powders

Single-phase high-entropy metal carbonitride (HECN) powders, namely (HfZrTaNbTi)(C,N), were successfully synthesized via a facile high-energy ball milling assisted carbothermal reduction nitridation at the temperature above 1400 °C in a flowing N2 atmosphere for the first time. The as-prepared HECN powders had a single-crystalline structure of metal carbonitride and simultaneously possessed high compositional uniformity. The increasing temperature from 1400 °C to 1600 °C promoted the grain growth of HECN powders from 0.31 μm to 1.26 μm. The low oxygen content of 0.494 wt% was obtained for as-prepared HECN powders at 1600 °C. This work is the first report of preparing a high-entropy metal carbonitride powders using metal oxides and carbon as raw materials.

Synthesis and thermal stability of novel high-entropy metal boron carbonitride ceramic powders

High-entropy metal boron carbonitride ceramic powders including (Ta0.2Nb0.2Zr0.2Hf0.2W0.2)BCN, (Ta0.2Nb0.2Zr0.2Hf0.2Ti0.2)BCN, and (Ta0.2Nb0.2Zr0.2Ti0.2W0.2)BCN, were successfully synthesized via mechanical alloying at room temperature. Results show that for the first step of 10 h milling, the amorphous BCN phases are observed. After 24 h of second step milling, the as-synthesized high-entropy ceramics exhibit a single face-centered cubic solid solution structure with high compositional uniformity from nano-scale to micron-scale. When heated to 1500 °C for 30min in flowing Ar, the as-prepared high-entropy ceramic powders still show relatively high thermal stability; however, some metals oxides like HfO2 and ZrO2 are detected due to the pre-existing oxides on sample surfaces. After heat treatment, some amorphous phases are still retained. This work suggests a new processing route on the synthesis of high-entropy metal boron carbonitride ceramics.

Zirconia nanopowder synthesis via detonation of trinitrotoluene

Zirconium (IV) oxide nanopowder was successfully synthesized through the detonation of a mixture composed of 2,4,6 trinitrotoluene (TNT, C7H5N3O6) and zirconium sulfate tetrahydrate (Zr(SO4)2·4H2O) as the energetic material and ceramic precursor, respectively. TNT, one of the most popular explosives, is a secondary energetic molecule and exhibits high stability and low sensitivity toward external stresses, making its handling safe. After detonation of the energetic material/ceramic precursor mixture and purification of the detonation soot, a crystallized zirconium oxide (ZrO2) powder composed of nanosized particles with a spherical morphology was produced and analysed by the usual characterization techniques (X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and nitrogen physisorption). The reaction mechanism, considering the thermochemical aspect of the explosive, is offered. This approach could provide promising opportunities for the synthesis of various nano-sized oxide ceramic powders.

Synthesis and sintering of nanocrystalline SiC ceramic powders

This paper reports a simple route to synthesize nanocrystalline silicon carbide (SiC) ceramic powders via the direct reaction of silicon powders with carbon black in a temperature-programmed muffle furnace. The mixing powders of silicon and carbon black were loaded in a alumina crucible, and then the crucible was sealed with some materials to prevent oxidization. The effect of reaction temperature on the phase of the product powders was investigated. FESEM and TEM images showed that the SiC nanopowders were spherical and had an average particle size of 48.56 nm. The sintering activities of the SiC nanopowders and commercial SiC fine powders were also investigated by hot-pressing sintering. SiC nanoceramic sintered at 1850 °C exhibited a high relative density (up to 99.2%) and a high flexural strength of 580 MPa, which exhibits better sintering activity of synthesized SiC nanopowders.

Luminescent properties of Li(Ga1-xCrx)5O8 (LGCO) phosphors

In this work, we investigate the synthesis of LiGa5O8 ceramic powders through a polyvinyl alcohol-based sol-gel technique and their optical properties when doped with high Cr3+ concentrations (5, 25 and 50 mol% with respect to the Ga3+ sites). The results indicate that the main crystalline phase, LiGa5O8, is obtained after calcining the samples at 1000 °C/2 h in a static air atmosphere. Via X-ray photoelectron spectroscopy, Cr is confirmed to exist in its trivalent oxidation state and the evaluation of the optical properties is performed via photoluminescence excited from visible to vacuum ultraviolet energy range and with X-ray excited optical luminescence, indicating the typical Cr3+ emission at the near-infrared energy range. The crystal field and Racah parameters are calculated and the influence of Cr3+ concentration in the host material indicates luminescence suppression/quenching and a redshift for a higher amount of these ions.