The high-entropy carbides (HECs) are reviewed in terms of the crystal structure, powder synthesis, densification, and mechanisms in this article. The inter-diffusion rate of binary carbide is mainly analyzed and predicted based on lattice parameters. During the solid solution formation progress, the densification methods usually adopted were hot pressing and spark plasma sintering. It was found that the distribution of metal atoms was more uniform in high-entropy powders derived from binary carbide raw materials. HECs displayed higher hardness, elastic modulus, and oxidation resistance, and meanwhile exhibited lower thermal conductivity compared to binary carbides. HECs are expected to be used as high-speed atmospheric re-entry vehicles.

A high-entropy layered hydroxide (HELH), in which Mg²⁺, Al³⁺, Co²⁺, Ni²⁺, Zn²⁺ were homogeneously distributed on two dimensions sheets, was synthesized for the first time. The HELH shows moderate thermal stability and hydroxide ion conductivity up to 10⁻³ S cm⁻¹. This finding presents tremendous opportunities for emerging new two-dimensional high-entropy materials.

The indentation test using a sharp diamond indenter, such as a Vickers indenter, has been long employed for comparing mechanical properties among various glass compositions, because of its simple procedure and easy operation. However, mechanisms of permanent deformation and crack nucleation in glass are far from simple. This has made it difficult to understand what controls the threshold load for cracking in a certain glass during indentation. In this review, the author’s works on indentation-induced deformation and cracking in glass are introduced, and relevant issues on the indentation technique are discussed. Especially, it is pointed out that permanent densification of glass under the indenter is a key phenomenon which controls the following cracking event. Further, it is also shown that the micro-photoelastic observation system, by which the indentation-induced stress field can be visualized, and the indentation microscope, which enables one to measure the contact area between glass and the indenter, are powerful tools to stimulate new and fresh ideas for improving mechanical properties of glass.

Glasses can be systematically designed according to their composition, and their potential to release ions can also be manipulated by tailoring their structures. Notably, phosphate invert glasses (PIG) can contain various elements that are comparable with silicate glasses due to their acidity. In this review article, novel PIGs containing therapeutic ions for bone regeneration, and anisotropic scaffolds for reconstructing bone quality were reviewed. PIGs have been structurally designed to utilize intermediate oxides, such as TiO₂, Nb₂O₅, ZnO, and MgO. As a result, PIGs with excellent chemical durability are expected to sustain their ion-relesability for bone regeneration and exhibit antibacterial activities. In contrast, PIGs have been designed with improved ion-releasing rates, with some releasing 20 times more ions compared to conventional PIGs. This was accomplished by manipulating the glass structure to contain only orthophosphates and orthosilicates. In other words, these glasses have no long-chain structures. Therefore, such glasses can be carriers of therapeutic ions for composite biomaterials, and are expected to enhance bone regeneration. Fibrous anisotropic scaffolds containing the designed glass have also been developed for the simultaneous reconstruction of bone quantity and quality. These scaffolds were enhanced to encourage bone formation by releasing ions from the glass, which controlled bone quality by direction of the calcified tissue in a single direction. Therefore, PIGs are expected to expand into various biomedical fields, as they can be tailored to have different properties according to their glass network structure.

The effect of cellulose nanofibrils (CNFs) on the mechanical properties of substrate of metal ceramic heater and electrical properties of electrically conductive layer were studied experimentally in a tube furnace at 1600 °C under reduced atmosphere. The alumina ceramics with 96 wt % of alumina and 4 wt % of sintering additives, namely SiO₂ and MgO were applied as the substrate. There was a noticeable rise in fracture toughness of alumina ceramics. The addition of 3 wt % of CNFs in ceramic had a significant effect on the improvement of fracture toughness. A K_IC of 6.52 MPa·m^1/2 was achieved through the addition of 3 wt % CNFs. A considerable decrease in K_IC was observed with addition beyond 3 wt % of CNFs. On the other hand, the relative density and bending strength had been steadily dropping with addition of CNFs. The bending strength was 296 MPa with no addition of CNFs. The bending strength of only 158 MPa was achieved with the addition of 5 wt % of CNFs. The sample with 1 wt % CNFs was selected as the substrate. The SiO₂ in the ceramic was reduced by pyrolysis of CNFs and formed W–Si solid solution. The temperature coefficient of resistance was decreased by the solution of Si into W.

Agglomerates of faceted single crystal grains of titanium nitride (TiN) with a size of 1–100 µm were synthesized by heating TiO₂, FeTiO₃, or TiO and Na in a boron nitride (BN) crucible at 1000–1100 °C under an argon atmosphere. Water soluble sodium borates were also produced as a melt phase during the heating. The yield of TiN prepared from TiO₂ at 1100 °C was 77%. Wavelength-dispersive X-ray analysis of the TiN single crystal grains revealed that the composition was almost stoichiometric, and the oxygen content was less than 1.2 at %. The TiN formation could be regarded as a sort of metathesis reaction, in which the oxygen of TiO₂ and the nitrogen of BN were exchanged.

This work addresses the evaluation of different spinel-containing composition sagger material in thermo-mechanical properties and corrosion resistance contacting with cathode material. In order to improve the corrosion resistance, the efficient way is to prevent the Li⁺ diffusion into the sagger material, LiAlO₂ generated by the reaction between spinel and Li-ion battery cathode material wrapped on the surface as corrosion protective layer during the calcination, which prevent the physically contact and react with cathode materials, due to the LiAlO₂ obtained the low-activity to react with cathode material. Meanwhile, the thermo-mechanical properties of sagger material with different addition of spinel were characterized. The results indicated that the using of spinel lead to the better mechanical strength and thermal shock resistance of the sagger material due to introducing the second phase and mismatch of thermal expansion, respectively. Considering all the aspects, the optimal addition of spinel was 14 wt %.

This study has focused on the effect of Si-substitution with alio-valent boron and phosphorus on sodium-ion (Na⁺) conduction properties of the newly developed glass-ceramic Na₅FeSi₄O₁₂. The glass-ceramics with the Na⁺ conducting single phase were obtained with the compositions Na_5+xFeB_xSi_4−xO₁₂ and Na_5−yFeP_ySi_4−yO₁₂, although the solubility limits were restricted as x < 0.4 and y < 0.3. The conductivity of the mother Na₅FeSi₄O₁₂ glass-ceramics was enhanced on both Na_5+xFeB_xSi_4−xO₁₂ and Na_5−yFeP_ySi_4−yO₁₂, and the maximum conductivities were achieved on the compositions Na_5.2FeB_0.2Si_3.8O₁₂ (x = 0.2) and Na_4.9FeP_0.1Si_3.9O₁₂ (y = 0.1), as high as 3.1 × 10⁻³ and 4.2 × 10⁻³ S cm⁻¹ at 300 °C, respectively.

Tungsten trioxide (WO₃) undergoes an electrochromic (EC) color change upon ion exchange via electrochemical redox reactions. Thin films of WO₃ are often fabricated by physical processes based on magnetron sputtering, and lithium is typically used as the cationic species that causes the color change. In a preliminary study, we achieved a suitable EC performance by using potassium as the cation in wet-processed films manufactured by a spin-coating method using WO₃ nanoparticles. However, comparisons of the EC properties of the WO₃ thin films prepared by various techniques are insufficient, and the behavior of potassium in these systems remains unclear. In this study, we observed that it was difficult for potassium to be swept smoothly into films prepared by sputtering or ion plating. In contrast, a wet-processed thin film obtained by spin coating was found to exhibit a good EC performance. This appeared to be largely attributable to structural variations arising from the film preparation methods.

The foamed alumina ceramics with excellent sound absorption performance especially at low frequency were fabricated by gelcasting-foaming process which gelled at room temperature. This process was simpler and more environmental-friendly than conventional gelcasting process because only a very small amount of organics were used and then green bodies could be sintered directly without binder removal process. The effects of foaming agent on porosity, pore size, compressive strength and sound absorption characteristics of the porous ceramics with different air-gap depths were discussed. The results showed that with the increasing of foaming agent content from 0.10 to 0.25 wt %, the porous ceramics had higher porosity, larger pore size, smaller compressive strength and better sound absorption characteristics. But the foaming agent’s effect got less significant than before when it’s amount was more than 0.25 wt %. The sound absorption peak of foamed ceramics shifted towards higher frequency as increasing foaming agent content, but it shifted towards lower frequency as increasing the air-gap depth. And within the data range of this study, increasing porosity could improve the sound absorption characteristic of the ceramics with an air gap. The ceramic with foaming agent content of 0.25 wt % and air-gap depth of 80 mm had the best sound absorption whose maximum sound absorption coefficient and noise reduction coefficient is 0.99 at 400 Hz and 0.79 respectively, and its mean sound absorption coefficient at 50–1000 Hz is ∼0.6.

Due to the unique three-dimensional spatial network structure formed by SiO₂ nanoparticles and high surface aera, silica aerogel is a high-profile material in many fields. In the present study, by adopting the industrial water glass as the silicon source, silica aerogels had been prepared via the sol–gel approach followed by the ambient pressure drying process. The effects of different alkaline catalysts in terms of LiOH, NaOH, KOH, and NH₃·H₂O on the formation of silica aerogels were investigated. It was found that with the introduction of alkaline catalysts, the gel aging time dramatically decreased from 5840 to 31 min during the sol–gel process. Compared with the silica aerogels prepared without any catalyst, accordingly, the thermal stability was significantly improved, and the decomposition temperature increased from 375 to above 410 °C. Furthermore, the silica aerogels prepared with alkaline catalysts were featured in a distinctive double-pore structure. It was shown that the alkali metal ions might have an alkaline dissolution effect in the weakly acidic environment during the sol–gel process. Moreover, this effect might increase the contact area between different SiO₂ nanoparticles, which was benefit to maintain the three-dimensional spatial network structure and resulted in the silica aerogels with higher thermal stability. The alkaline dissolution effect had an influence on the pore size distribution of silica aerogels with a double pore structure at 1.7 and 32 nm as well as retained large pore volume at about 2.60–3.35 cm³/g.

In this paper, the influence of different microwave conditions on industrial waste residue was studied. It is hoped that the porous ceramic materials which can absorb SO₂ and NO_x in flue gas efficiently can be prepared by using these industrial waste residues. The results show that microwave treatment can effectively improve the activity of industrial waste residue and the adsorption capacity of flue gas. And the appropriate microwave sintering power and sintering time can improve the specific surface area and pore size of adsorbent, and enhance the adsorption capacity of flue gas. Under the experimental conditions, the best microwave sintering conditions are sintering power 1000 W and sintering time 1200 s. Under these conditions, the porous ceramic adsorbent has the best adsorption effect, with the desulfurization rate of 98.8% and the denitration rate of 91.9%.

Zirconia particles were prepared by thermal treatment of zirconium(IV) tetra-n-propoxide (ZNP) in C₂–C₆ glycols (Glycothermal method) at 300 °C and morphology and pore structures of the products were examined. X-ray diffraction results revealed that nanocrystals of tetragonal zirconia phase were mainly obtained in all cases. However, the morphology and pore structures of the products were quite different depending on the glycols used. The products prepared in 1,4-butanediol (1,4-BG) were spherical particles with ca. 5 µm size while aggregations of fine particles were observed for other glycols. The samples obtained in 1,4-BG had large surface areas and showed narrow pore-size distributions in the mesopore region. To investigate the formation process of the products having such a unique morphology and pore system, the mixtures of ZNP and glycols were heated at lower temperatures. It was found that the thermal reaction of ZNP in 1,4-BG at 200 °C afforded intermediates with layered structures, which subsequently changed into nanocrystalline ZrO₂ at elevated temperatures. These stepwise crystallization processes attribute to the unique morphology and pore system of the products obtained by the thermal treatment of ZNP in 1,4-BG.

In this study, the effects of atmosphere firing and pre-heating treatment on the characteristics of sodium titanates were investigated. The materials were successfully prepared from titanium tetraisopropoxide-sodium chloride (TTIP-NaCl) precursors assisted by organic templates (ethylene glycol and citric acid) via facile templating and hydrothermal methods. Sodium titanates were initially prepared by mixing a sodium precursor solution with a titanium precursor solution at a stoichiometric mole ratio of 1.6:1 under vigorous stirring. This was followed by pre-heating treatment via a hydrothermal method at 150 °C for 6 h and then calcination at 800 °C for 1 h in two different atmospheres including reduction and oxidation conditions. The same process was carried out in the synthesis of the other samples without the preheating treatment. The thermal behaviors of all the as-synthesized samples were evaluated. Meanwhile, the mineralogy and microstructures of all calcined samples were investigated. Both atmosphere firing and pre-heating treatment influenced the thermal behaviors of the as-synthesized sodium titanates, resulting in various sodium titanate types with different microstructures. To prepare the sodium titanates from TTIP-NaCl precursors, the pre-heating treatment and the reduction firing seemed to be the optimum conditions for the formation of sodium titanate, in order to produce Na₂Ti₆O₁₃-type sodium titanates with rod-like particles in nanometer sizes.

Manganese oxide particles were prepared by alkaline treatment of the manganese and silicon compound. Silicon was selectively dissolved by the alkaline treatment, forming an aggregate structure of plate-like particles. Consequently, owing to the high specific surface area and surface exposure of the manganese, the catalyst exhibited excellent behavior in the oxidative decomposition of benzene.

Potentiometric sensors aiming at detecting H₂ were examined. Yttria-stabilized zirconia (YSZ) based sensor elements, H₂, Pt/YSZ/Pt, air, responded to a ppm level of H₂ contamination in air with the value of electromotive force (ΔEMF) = 30 mV at 350 °C. Coating the Pt sensing electrode with a powder of hexagonal boron nitride (h-BN) increased the EMF response, and the sensor response further increased by the milling treatment of the h-BN powder in ethanol. However milling treatment over 24 h reversed the response to decreasing. The specific surface area of the h-BN powder monotonously increased by the ball-milling which induced exfoliation of the BN layer. While Fourier transform infrared spectroscopy analysis suggested that point defects existing in the BN plane react with ethanol or water by the milling for >48 h. It was concluded that the point defects in h-BN play a decisive role in the property of the h-BN auxiliary phase in sensor response to H₂.