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ZrSiO4 demonstrates applicability as the SiC/SiC interphase. Via a non-hydrolyzed sol-gel method, the pyrolysis product, synthesis condition, and the formation effectiveness of the ZrSiO4 coating on SiC fibers were investigated. Mini-SiC/SiC composites with two layers of ZrSiO4 interface coatings were oxidized to preliminarily verify their oxidation resistance effect.

Semiconductor-based photocatalysis represents a promising technology for removing antibiotic given its cost effectiveness and environmental compatibility. However, finding suitable photocatalysts and semiconductors for practical applications can be challenging. This work aims to investigate the photocatalytic performance of as-synthesized photocatalysts under broad-spectrum from visible (Vis) to near-infrared (NIR) sunlight. In this work, a step-scheme (S-scheme) heterojunction photocatalyst, i.e., CuS/S–C3N4, was prepared, employing a single-step hydrothermal route. The synthesized photocatalyst showed excellent crystallinity and high purity content. The CuS loading provided a better NIR light response-ability and improved photocatalytic activity for CuS/S–C3N4. The 2 wt% CuS/S–C3N4 produced the highest tetracycline (TC) photodegradation rate, up to about 95% efficiency under Vis + NIR light irradiation. The result also showed that the 2 wt% CuS/S–C3N4 sample had a first-order kinetic constant (k) that was 6.2-fold higher than the pure S–C3N4 sample under Vis + NIR light irradiation. However, too much CuS content led to the presence of inactive sites on S–C3N4, which hampered the light absorption ability, thus leading to inadequate photocatalytic activity. In addition, the 2 wt% CuS/S–C3N4 sample also showed high photocatalytic stability and insignificant change of the composite structure before and after the experiments. In short, we can enhance the CuS/S–C3N4 photocatalytic activity by increasing the light response range and the separation efficiency of light-induced electrons and holes. Consequently, we have developed a novel strategy and experimental basis for S-scheme heterojunction to be fully utilized under broad-spectrum sunlight.

Semiconductor-metal heterostructure, especially represented by various inorganic semiconductors-platinum (Pt) hybrids, is widely applied in converting solar power to chemical energy. Given the scarcity of Pt and the availability of coupling, the development of a non-Pt regimen and facile assembly strategy is critical. In this study, CdxZn1-xS/Ti3C2 ultrathin MXene composites were availably prepared with a facile electrostatic assembly strategy. The unique 0D/2D assembly demonstrated remarkably enhanced performance toward photocatalytic hydrogen production compared with bare CdxZn1-xS. Spectroscopic characterization analysis and band theory discussion substantiated the effects of electronic interaction and the Schottky barrier arising from intimate contact of CdxZn1-xS and Ti3C2 MXene on the swift separation of photoinduced electron-hole pairs. Successful application of electrostatic self-assembled CdxZn1-xS with ultrathin MXene opens a new area of utilizing electrical difference and band theory to prepare rational semiconductor/MXene Schottky structure towards various photocatalytic reactions.

In this work, different carbon sources, such as nano-sized carbon black (CB), carbon nanotubes (CNT), carbon fibers (CF) and graphene (GR), were reacted with titanium micro-powders, to synthesise titanium carbide (TiC) in the mixed molten salts of LiCl–KCl–KF at 1100 °C for 6 h. There experiments were performed to investigate the accuracy of “carbon-template-growth” mechanism for the formation of TiC, that was proposed previously using micro-sized titanium and submicro-sized CB powders. The products synthesised from the different carbon sources were observed and characterised by scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The results showed that the visual morphologies of the TiC products mainly retained the shapes of the as-received carbon sources, that is, they presented an equiaxed-shape with a grain size of 10–20 nm from CB, a shell layer along the outer surface of the CNTs and CF, and a flake-shape with the GR. These morphologies reveal that the formation of TiC is indeed controlled by the “carbon-template-growth” mechanism.

β-Sialon powder containing nanofibers was synthesized at 1300–1450 °C for 5 h in nitrogen by using transition metals (Fe, Co and Ni) as catalysts. Such synthesis conditions obviously reduced the nitriding temperature (~100 °C) of β-Sialon and increased the degree of nitridation. Observations from the weight gain rates of specimens relative to the content of catalysts suggest that the nitridation process was accelerated sharply via the addition of 0–2.5 wt% metallic catalysts. In addition, the amount of nanofibers of β-Sialon found in the specimens increased with the amount of transition metals, which was governed by the VLS formation mechanism with the help of transition metals. It could be concluded that transition metals not only greatly accelerated the nitridation of Si but also facilitated the formation of β-Sialon nanofibers in the specimens, as the formed metal-containing liquid greatly enhanced the amount of vapor generation.

In order to verify the “Al2O3-template-formation” mechanism of magnesium aluminate (MA) spinel proposed previously using Al2O3 and MgO micro-powders as raw materials, in this work, MA spinel was synthesized by nanograined, plate-like, and fibrous Al2O3 in LiCl molten salt at 1150 °C for 3 h, respectively. The products were characterized by XRD, SEM, TEM, and EDS techniques, and the grain size of the products and raw materials were analyzed. The results showed clearly that the MA spinel was initially nucleated and subsequently developed to octahedral crystal. When the reaction further took place, when using nanograined Al2O3, the newly formed MA spinel seeds initially moved and attached to the surface of the large octahedral MA spinel crystal, and they were subsequently engulfed by the large MA spinel crystal, which further grew via layer-by-layer to become micro-sized crystal. Using plate-like or fibrous Al2O3 raw material, MgO diffused continuously into the interior of Al2O3 to form MA spinel with a gradient growth from surface to depth. These revealed that whatever shape of Al2O3 was used, the synthesis of MA spinel was governed by “Al2O3-template formation mechanism”, i.e., by the reaction of MgO diffusion into the Al2O3 templet in the molten salt.

Graphitic carbon nitride (g-C 3 N 4 ) prepared by traditional methods has various disadvantages, e.g., small specific surface area, low band gap, high photo-generated carriers recombination and low exfoliation efficiency, which limits its practical application. In this study, folded nano-porous graphene-like g-C 3 N 4 (abbreviated as FNPGLCN) was prepared by a simple but quite effective method of calcining urea in water. The effects of calcination temperature on crystal structure, energy band and microstructure of g-C 3 N 4 were investigated. The photocatalytic activity for methylene blue (MB) degradation under visible-light was evaluated. The results revealed that the FNPGLCN had higher specific surface area (197 m 2 /g) and larger band gap (2.87 eV) than bulk g-C 3 N 4 . With calcination temperature rising from 450 to 500 °C, the pore size and specific surface area of FNPGLCN increased. However, the pore structure almost disappeared and the thickness of g-C 3 N 4 became thinner at 550 °C. Compared with bulk g-C 3 N 4 , the photocatalytic degradation rate of FNPGLCN for MB increased from 0.131 to 1.298 h −1 . The significant enhancement of visible photocatalytic activity was mainly attributed to folded nano-porous structure, which simultaneously improved visible-light absorption range and strength, and enlarged the band gap and specific surface area of g-C 3 N 4 .

Aluminum oxynitride (AlON) ceramic was fabricated by in-situ hot pressing sintering (HPS) from Al 2 O 3 and AlN doped with Y 2 O 3 and La 2 O 3 as well as without dopant for comparison. Dense AlON ceramic with a relative density of 99.7% was obtained by HPS doped with 0.4 wt% Y 2 O 3 and 0.1 wt% La 2 O 3 at 1700 °C for 4 h. The maximum fracture toughness of AlON ceramic with and without dopant was 3.74 MPa m 1/2 and 2.27 MPa m 1/2 , respectively. The maximum Vickers hardness of AlON ceramic with and without dopant was 18.3 GPa and 16.5 GPa, respectively. Compared with those of undoped AlON ceramic, the relative density and the fracture toughness of Y 2 O 3 -La 2 O 3 co-doped AlON ceramic were obviously improved. Overlarge grain size would reduce the Vickers hardness of AlON. The sintering activation energy of Y 2 O 3 -La 2 O 3 co-doped AlON was about 57% of that of undoped AlON. The sintering activity of AlON was highly improved by co-doping with Y 2 O 3 and La 2 O 3 .

Ultrafine powders of pyrochlore-type La2Zr2O7 were synthesized via a simple molten salt mediated process using zirconium oxide and lanthanum oxide as raw materials, and sodium chloride, potassium chloride and sodium fluoride to form a reaction medium. The effects of reaction temperature, salt/reactant ratio and salt type on the La2Zr2O7 formation were investigated. Among the three attempted salt assemblies (KCl–LiCl, Na2CO3–K2CO3, and NaCl–KCl–NaF), NaCl–KCl–NaF showed the best accelerating effect on the La2Zr2O7 formation. At a given temperature, the La2Zr2O7 content in the final products increased with the increase in the salt amount. Phase pure submicron sized La2Zr2O7 ultrafine powders were obtained after 3 h firing at 1100 °C with the salt/reactant weight ratio of 5:1 or at 1200 °C with salt/reactant weight ratio of 3:1. The synthesis temperature (1100 °C) was much lower than that required by the conventional solid-state mixing method or a wet chemical method. The “dissolution–precipitation” mechanism had dominated the synthesis process.

Ultra-long SiC/SiO2 core–shell nanowires were successfully prepared on a graphite felt with Ni(NO3)2 coating by a straightforward molten-salt-mediated carbothermal reduction route using silica fume and phenolic resin as starting materials at 1400 °C. The as-synthesized nanowires, 150–500 nm in diameter and up to several hundred microns in length, comprised a crystalline 3C–SiC core with a thin amorphous SiO2 shell (about 30 nm). The growth mechanism of the as-synthesized nanowires was most likely controlled by the combination of vapor–liquid–solid and the vapor–solid mechanism. The photoluminescence spectrum of the ultra-long core–shell SiC/SiO2 nanowires exhibited a significant blue-shift, indicating a potential application in optoelectronic devices.

Ultra-long single crystalline β-SiC nanofibers were successfully prepared on a Ni(NO 3 ) 2 coated graphite felt by a facile molten-salt-mediated chemical vapor deposition route using silicon and phenolic resin as starting materials at 1350 °C. The as-synthesized SiC nanofibers were 100–300 nm in diameter and hundreds of microns up to millimeters in length. The nanofibers possessed a near-perfect crystal microstructure with tiny amounts of stacking faults. The growth process of the SiC nanofibers was determined by the combination of vapor–liquid–solid base-growth and vapor–solid tip-growth mechanism. The as-synthesized SiC nanofibers exhibited strong blue-green luminescent properties, making possible potential application in the LED and optoelectronic nanodevices.

Single crystalline silicon carbide nanowires (SiC NWs) were prepared through the carbothermal reduction route using silica fume and phenolic resin in a molten salt (NaCl and NaF) medium at 1450 °C. The presence of molten salts was found to have a noticeable effect on the complete conversion of SiO 2 to 3C–SiC with the temperature increasing from 1300 °C to 1450 °C, and NaF/NaCl ratios and molten salts/reactant ratios also played vital roles in the growth of SiC NWs. The as-achieved SiC NWs were 100–150 nm in diameter and 10 μm in length, which grew along the direction perpendicular to the (111) plane and contained stacking faults (SFs). The as-synthesized SiC NWs had a strong emission peak (422 nm) located in the violet–blue spectral range, suggesting potential applications in optoelectronic devices. All these discoveries suggest a cheap and feasible route for large scale growth of high quality SiC NWs at low temperature.

The catalytic effects of cobalt (Co) on the direct nitridation of silicon (Si) and morphologies of the nitridation products were investigated, and the relevant reaction mechanisms were proposed. The overall conversion of Si to silicon nitride (Si 3 N 4 ) was dramatically improved with increasing the nitridation temperature from 1300 to 1350 °C. Co played an important role in accelerating the Si nitridation as well as the in-situ growth of α-Si 3 N 4 nanorods, via the formation of Co Si liquid phase. At 1350 °C, the overall conversion in the reference sample without Co was only 54%, whereas it exceeded 90% in the sample containing 1.25 wt% Co. When the Co addition was more than 7.5 wt%, α-Si 3 N 4 nanorods of 80–120 nm in diameter and 800–1600 nm in length became the main product phase. The growth processes of the nanorods with and without nanoparticles (caps) at their tips were governed respectively by vapor–liquid–solid and vapor–vapor–solid mechanisms.

Sialon–ZrN powders were synthesized from low-grade bauxite using a zirconite additive by carbothermal reduction nitridation (CRN). The as-synthesized Sialon–ZrN powders were subsequently used as SiC-based free-fired refractories. Their phase compositions and microstructures of the powders were determined using X-ray diffraction and scanning electron microscopy. The physical properties and blast furnace (BF) slag resistance of the SiC–Sialon–ZrN free-fired refractories were also studied. The results show that the low-grade bauxite and zirconite powders were transformed to β-Sialon and ZrN by the CRN process at 1600 °C. The phenolic resin provided a strongly bonded interface between the Sialon–ZrN matrix and SiC particles and thus enhanced their combined strength after drying at 150 °C. The strength increased as the temperature was elevated from 1000 °C to 1500 °C. As the ZrN content increased, the slag erosion rate of the SiC–Sialon–ZrN free-fired refractories initially decreased and then increased after being heated at 1500 °C. The presence of ZrO 2 in the slag (oxidized from ZrN) revealed that the ZrO 2 did not react with other oxides in the BF slag to form low melting point phases. This may play a crucial role in its BF slag erosion resistance. The corrosion mechanism of the BF slag towards the as-prepared SiC–Sialon–ZrN free-fired refractories was determined to be oxidation-erosion-dissolution-penetration.

Fabrication of densified 15R-β-U Sialon-polytypoid composite has been reported previously using a pressureless sintering (PLS) method at a relatively low temperature (1650 °C). The mechanical properties of this material are as good as those high temperature heat-pressed Sialon-polytypoids. In this study, the crack propagation characteristics were investigated to interpret the fracture behaviors of this material by transmission electron microscopy (TEM) technique. A schematic diagram was proposed according to the experimental results. The composite mainly fractures via a transgranular mode as indicated by the propagation routes of cracks. Subcrack branches can be induced by deflecting or shifting of cracks intergranularly or within a grain. The bonding strength of interface within grains is higher than the bonding force within the layer structure of 15R, contributing to the excellent mechanical properties of the pressureless sintered composite.

Self-strengthened mullite ceramics with interlocking columnar grains formed through enhanced anisotropic growth by adding La2O3 were prepared from coal gangue and g-Al2O3 within the temperature range 1400–1550 1C and holding time of 4 h. The effects of La2O3 on the bending strength, microstructural evolution, and phase composition were studied. The results showed that the bending strength of the as-prepared ceramics was significantly improved by the addition of La2O3. For samples sintered at 1550 1C, the bending strength increased from 64 MPa to 218 MPa as the La2O3 content increased from 0 mol% to 10 mol%. X-ray diffraction analysis suggested that the formation temperature of secondary mullite was lowered by about 50 1C by adding La2O3. Scanning electron micrographs revealed that the La2O3-added mullite mostly existed in long, columnar form, with aspect ratios of 3–6, forming an interlocking network structure. The interlocking mullite columns, together with the enhanced densification behaviour, contributed to the improved bending strength.

In this paper, SiC nanowires were successfully synthesized on Si substrate by the thermal evaporation method without the assistance of a metal catalyst. The phase composition, morphology and microstructure of the SiC–SiO 2 core–shell nanowires were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The SiC nanowires produced grew along the [111] direction and had diameters of 50–100 nm with lengths of several hundreds of microns. The SiC nanowire was composed of a single-crystalline SiC core with a thin amorphous SiO 2 shell. The growth mechanism of the nanowires can be explained by the vapor–solid (VS) process.

Single-crystallize phase Li-α-Sialon with equiaxial morphology has been successfully synthesized by solid state reaction at 1700 °C for 1 h under a N 2 atmosphere. The effects of additions SiO 2 and Al 2 O 3 , holding time at 1050 °C and packing powders, on the phase compositions and Li contents of products have been investigated by XRD, SEM, EDS and ICP-OES. The results showed that additions SiO 2 and Al 2 O 3 , holding time at 1050 °C and packing powders played an important role in retarding the vaporization of lithium and forming Li-α-Sialon, where the former two ways were by formation of more Li-containing liquid while the latter was by providing a source of Li-containing vapor and increasing partial pressure of Li in the surrounding gaseous environment resulting in preventing volatilization of Li from the sample. However, there were more or less AlN, AlSi 0.5 O 2.5 , β-Sialon present in the products when these factors were ignored.