Cr2AlC powders were synthesized using graphite, carbon black and biomass-derived coconut shell charcoal as carbon sources, and the regulatory effects of carbon source characteristics on phase evolution, microstructure and formation mechanism during Cr2AlC synthesis were investigated. The results reveal that the characteristics of the carbon sources dominate the reaction process, and Cr2AlC synthesis follows a common pathway involving the formation of Al-Cr alloy and carbide intermediates, intermediate transformation and subsequent nanolayered grain growth. Graphite exhibits low reactivity due to the high crystallinity, resulting in Cr2AlC purity of only 78.6 wt% at 1400 °C. Amorphous carbon black enables efficient synthesis of high-purity Cr2AlC (98.9 wt%) owing to nanoscale particle size and ultrahigh reactivity. Coconut shell charcoal is endowed with a unique porous structure that facilitates rapid atomic diffusion and mass transfer, yielding Cr2AlC with 96.8 wt% purity. The oxidation of Cr2AlC powder initiates with the formation of amorphous Al2O3 protective layer on the particle surface, which gradually evolves into complex structure consisting of an outer (Al0.9Cr0.1)2O3/Cr2O3 mixed layer, an intermediate Cr2O3 layer and an inner Cr7C3 layer. Coconut shell charcoal-derived Cr2AlC exhibits a balance combination of structural stability and oxidation resistance at moderate and high temperatures, providing a green and efficient strategy for synthesizing high-performance MAX phase powders.

TiC nanoparticles were controllably synthesized via a molten salt method, employing Ti powder as the titanium source and high-crystallinity graphite and biomass-derived coconut shell carbon as the carbon source. The influences of the carbon source on the phase evolution, microstructure and oxidation of the products were elucidated using XRD, SEM, EDS and thermogravimetric analysis. The results indicate that coconut shell charcoal exhibits superior reaction kinetics, attributed to the high reactivity of amorphous carbon and the high specific surface area of the porous structure. TiC nucleation initiates as low as 700 degrees C, and high-purity TiC nanoparticles are obtained at 900 degrees C, exhibiting a distinctive coral-like wrinkled morphology derived from the biomass template effect. In contrast, the low reactivity of graphite requires a higher temperature to achieve TiC conversion. Coconut shell charcoal-derived TiC displays remarkably higher oxidation onset and peak temperature compared to graphite-derived TiC powder. This study elucidates the influence of carbon source on the structure and oxidation of TiC, providing a technical pathway for fabricating TiC-based functional materials with controllable morphology and superior comprehensive performance.

Lithium titanate (Li₄Ti₅O₁₂, LTO) has emerged as an ideal candidate material for lithium-ion batteries, owing to its zero-strain characteristic and high-voltage plateau. However, the low lithium-ion diffusion coefficient and poor electrical conductivity of LTO restrict its charge-discharge rate capability. Herein, we propose a novel synergistic strategy to construct yttrium (Y3+) doped LTO/reduced graphene oxide (Y-LTO/rGO) by integrating yttrium (Y3+) doped nano-LTO (Y-LTO) with reduced graphene oxide (rGO) via heterointerface engineering. Y doping expands the lattice spacing of LTO, thus widening the transport channels for Li+. The heterointerface between Y-LTO and rGO induces a built-in electric field, which provides an extra driving force for Li+ migration. Y-LTO nanoparticles are uniformly dispersed on the rGO matrix, constructing a 3D continuous conductive network that enables rapid Li+ migration from the heterointerface to the lattice interior. The optimized Y-LTO/rGO anode exhibits high reversible capacity and excellent rate performance, delivering a specific capacity of 478.7 mAh·g−1 at 0.1 A g−1 and 153.6 mAh·g−1 at 20 A g−1. Moreover, it maintains a discharge capacity of 257.3 mAh·g−1 with a capacity retention rate of nearly 99% after 1500 cycles at 2 A g−1. This work provides new insights into the design of high-performance battery materials through the dual modification of lattice engineering and heterointerface engineering.

Tantalum aluminum carbide (Ta2AlC) powders were obtained by pressureless sintering at 1450 degrees C using a nonstoichiometric ratio of TaC: Al: Ta = 1: 1.3: 1. The synthesis condition minimises the presence of impurity phases (TaC and Ta4AlC3), as confirmed by microstructural analysis, which also reveals that the synthesized Ta2AlC has a distinct layered structure. A mixed oxide layer comprising tantalum oxide (Ta2O5), tantalum aluminate (TaAlO4), and aluminium oxide (Al2O3) was rapidly formed on the surface of Ta2AlC particles, acting as a diffusion barrier and effectively preventing the diffusion of oxygen into the interior of the particles. The stability of the non-isothermal oxidation of Ta2AlC powders was studied by thermogravimetric-differential thermal analysis (TG-DTA), and three peaks corresponding to the oxidation reaction of Ta2AlC powders were identified, which could be distinguished by the kinetics of inverse pleat formation, and the activation energies of the oxidation peaks were subsequently calculated by the Kissinger-Akahira-Sunose (KAS) and the Friedman (FR) methods.

To solve the problems of high cost and high firing temperature of ZrO2 inserted rings of slide plates, the in-situ MgAl2O4 (MA) toughened MgO-ZrO2 new ring materials were prepared using lightly calcined MgO, m-ZrO2 and nanoscale Al2O3. The effects of MgO/ZrO2 ratio and the amount of nanoscale Al2O3 on properties of samples were investigated. The results showed that the sinterability and mechanical properties of MgO-ZrO2 composites improved significantly due to the MA formed in situ by reaction between MgO and Al2O3, which promoted reactive sintering and densification of the samples. The improved thermal shock resistance (TSR) in MA-toughened MgO-ZrO2 composites was attributed to microcracks developed due to thermal expansion mismatch, MA and ZrO2 also acted as bridging particles, improving the ability to prevent crack propagation of the composites. The optimum MgO/ZrO2 ratio and addition amount of nanoscale Al2O3 were 7/3 and 3 wt%, respectively.

Ti3AlC2 3 AlC 2 powder was prepared via an efficient solid-liquid reaction in flowing argon using coconut shell charcoal as novel carbon source, and phase evolution, microstructure and oxidation behavior of Ti3AlC2 3 AlC 2 powder were investigated. The results show that coconut shell charcoal is dominated by amorphous carbon after carbonization with some turbostratic graphite-like structure, and large specific surface area of coconut shell charcoal gives its excellent reactivity. Ti3AlC2 3 AlC 2 powder prepared at 1400 degrees C for 1.5 h exhibits good crystallinity and typical nanolayered structure. Ti3AlC2 3 AlC 2 powder remains thermally stable in air below 552 degrees C, while oxidizing occurs rapidly between 900 and 1100 degrees C. The isothermal oxidation curves show a parabolic-like, indicating that the oxidation process is primarily controlled by a diffusion mechanism. The good oxidation resistance of Ti3AlC2 3 AlC 2 powder is attributed to the oxidized products of TiO2 2 and Al2O3 2 O 3 grains formed a connected and dense protective layer on the particle surface at elevated temperatures.

The Al 2 O 3 - ZrO 2 - C material was prepared using tabular alumina aggregates and fines, zirconia-corundum, zirconia-mullite, flake graphite, B 4 C powder, Si powder and different nano-oxides (nano-ZrO 2 , nano-TiO 2 , and nano-Al 2 O 3 ) as raw materials, the effects of different nano-oxides on the corrosion resistance and microstructure evolution of Al 2 O 3 - ZrO 2 - C material were investigated. The results showed that the high reactivity nano-ZrO 2 , nano-TiO 2 , and nano-Al 2 O 3 particles reacted with CaO to generate high melting point phases of CaZrO 3 , CaTiO 3 , CaO center dot 6Al 2 O 3 (CA 6 ) at high temperature, which forms a protective layer at the interface between corroded media and samples, inhibiting CaO penetration into the material. Additionally, nano-oxides can fill the pores and increase the density of material, thereby contributing to improving the penetration resistance and corrosion resistance of material.

The unfired Al–Si incorporated MgO–C slide plate materials were manufactured using magnesia aggregates and fines, SiC aggregates, Al, Si and B4C powders as the raw materials, trace nano-Al2O3 particles as additive, and phenolic resin as binder. The contributions of nano-Al2O3 in the properties, phase composition and microstructure of MgO–C materials were studied. The reseult indicates that nano-Al2O3 is beneficial to improve mechanical properties of the materials, which is attributed to the good filling and pinning effects of nanoparticles. Highly reactive nano-Al2O3 can promote the densification of MgO–C materials and in-situ formation of ceramic phases at high temperatures, and a large number of non-oxide whiskers contributes to the formation of a continuous interlocking networks, which improves the high-temperature strength and TSR of MgO–C materials. Moreover, nano-Al2O3 promotes the formation of fine-grained pinel and forsterite protective layer in the high-temperature oxidizing atmosphere and prevents the diffusion of oxygen into the interior of the material, thus improving the oxidation resistance of MgO–C refractories.

In this study, the effect of the alumina particle size on the formation of mullite using a silica gel powder and micro- and nano-scale Al2O3 powders as raw materials was investigated. The optimized Al2O3 source was then reacted with the silica gel to prepare porous mullite-based ceramics. The results revealed that the highly reactive nano-Al2O3 powder could form mullite at a relatively low firing temperature. Therefore, the nano-Al2O3 powder was used to prepare porous mullite-based ceramics by firing at 1600 degrees C, 1650 degrees C and 1700 degrees C. The pore size of the prepared porous mullite-based ceramics ranges from tens to hundreds of micrometres, with the apparent porosity being 42.8-58.0%. Further, the mullite content in the samples increased with increasing firing temperature, and a higher firing temperature promoted sintering, resulting in improved strength of the sample. After calcination at 1700 degrees C, the mullite content in the sample reached 81.8%, and the sample showed excellent thermal shock resistance. The strengths of the samples before and after thermal shock were found to be 23.6 and 15.58 MPa, with the residual strength ratio being 66%.

Using low-cost and highly reactive bamboo charcoal, Ti and Si elemental powders as starting materials, Ti3SiC2 powder was synthesized via a simple and cost-efficient pressureless sintering technique in argon atmosphere. The influences of synthesis temperature, holding time and Si content on the Ti3SiC2 content of the synthesized products were investigated, and the analysis indicated that the relative content of Ti3SiC2 reached 98.9 wt% with a molar ratio of 3Ti/1.2Si/2.2C at 1400 degrees C for 1.5 h. The Ti3SiC2 with good crystallinity and homogeneous nanolayered structure was synthesized at lower temperatures due to the high reactivity and high specific surface area of bamboo charcoal. The non-isothermal oxidation behavior showed that Ti3SiC2 powder was stable in air below 540 degrees C. With the temperature increasing up to 1300 degrees C, continuous and dense TiO2 and SiO2 oxidation layers were formed on the surface of Ti3SiC2 particles, which conferred good oxidation resistance to Ti3SiC2 powder.

Biochar was proposed as a novel carbon source for synthesizing Ti3SiC2 powder with high purity by a simple pressureless sintering at 1673 K, and Ti3SiC2 grains exhibited the typical nanolayered structure. The oxidation behavior of Ti3SiC2 powder showed the parabolic law during isothermal oxidation from 1273 K to 1473 K. Dense and continuous oxidation layer consisting of mixed TiO2 and SiO2 was formed rapidly on the surface of Ti3SiC2 particles as a diffusion barrier, which effectively retarded the inward diffusion of oxygen, conferring good oxidation resistance of the powder.

Biomass is a renewable energy resource with rich content in China.The products of the carbonization of biomass materials have been widely used in energy storage,adsorption materials,and other fields.Studying the carbonization process of biomass materials is crucial for the efficient use of biochar.This article summarizes the effects of biomass types and carbonization conditions(such as carbonization temperature and pretreatment)on the structure,morphology,and properties of carbon in carbonization products.The aim is to provide a theoretical foundation for the effective use of biomass carbonization products.Various biomass materials and biochar can be prepared after treatment.The contents of cellulose,hemicellulose,lignin,and ash in different types of biomass materials vary greatly,and the carbon content,carbon structure,morphology,and properties of the products after carbonization differ.Therefore,selecting appropriate biomass materials based on usage requirements is essential.The carbonization temperature of biomass materials plays an important role in the pyrolysis of biomass.As the carbonization temperature increases,cellulose,hemicellulose,and lignin gradually decompose into gases with small molecules.Furthermore,as the carbonization temperature continues to increase,the internal structure of biomass carbon continues to rearrange,forming a dense aromatic carbon network plane of macromolecules,which increases the graphitization degree of biomass carbon.Additionally,the temperature greatly affects the structure and amount of the products of biomass carbonization.The activation of biomass materials further enhances the specific surface area and adjusts the pore structure of biomass carbon.Chemical activators such as acids,alkalis,and salts are commonly used and have their own advantages and disadvantages.Appropriate activators should be selected by a comprehensive consideration of usage requirements to activate the biomass.This article summarizes the preparation of carbon nanotubes by the carbonization of biomass materials through the template and chemical vapor deposition methods under the action of a catalyst.Further,the influence of components such as lignin and cellulose in biomass materials on the preparation of carbon nanotubes is analyzed.Cellulose in biomass materials has a small molecular weight and is easy to pyrolyze,resulting in gases with smaller molecules.However,lignin has a large molecular weight,is difficult to decompose,and produces less amount of small molecular gas.Therefore,biomass materials with high cellulose content are found to facilitate the preparation of carbon nanotubes.On this basis,the application prospects of biomass materials in carbon-containing refractories have been considered and examined to provide ideas for the preparation of new carbon-containing refractories with low cost and good properties.

Polycrystalline SiC (3C-, 6H-, 24R-and 27H-) nanostructures are synthesized via a modified molten salt shielded synthesis method (m-MS3) in open air using Si and carbon black as the starting materials. The influences of salt species and their amount, and the sintering temperature, are discussed and optimized. Well crystalline SiC nanopowders composed of bountiful microstructures (nanoparticles, nanowires, nanosheets and nanoblocks) are successfully synthesized by m-MS3 at 1250 degrees C, with KCl and NaCl as the shielding salt. The polycrystalline SiC powders showed excellent photoluminescence property at an excitation wavelength of 330 nm and relatively small band gaps of 2.57-2.74 eV, which are quite attractive among reports for SiC-based materials. The investigation in this paper may provide a prototype strategy for protection-free synthesis of nanostructured SiC powders applicable for ultraviolet luminescence devices.

The effects of nano-ZrO2 powder on the evolution of phase composition and microstructure of Al2O3–C materials during firing have been investigated using tabular alumina, Si powder, Al powder, graphite and nano-ZrO2 powder as starting materials. The residual content of Al and Si gradually decreased with increasing temperature, and the added nano-ZrO2 facilitates the reactions involving Si and Al. The quantity of in-situ synthesized AlN and SiC whiskers exhibiting continuous interlocking networks increased gradually with temperature. Nano-ZrO2 facilitates more ceramic whiskers generated in samples, which play a strengthening and toughening role in the materials, thus improving the thermal shock resistance and high temperature strength of Al2O3–C materials. In addition, physical properties are improved due to the nano-ZrO2 filling the pores and increasing the density of materials.

To reduce the cost and firing temperature of traditional ZrO2 insert rings, the new ZrO2-SiCw-C (w-whisker) insert ring materials were successfully synthesized using ZrO2, Si, graphite powders as starting materials, and phenolic resin as binder. The effects of amount of Si powder addition (5, 8 and 11 wt%) and firing temperatures (1100 degrees C, 1200 degrees C and 1400 degrees C) on the phase composition, microstructure and properties of as-obtained products have been investigated. The results show that Si reacts with C or CO at high temperature to form SiCw, which in-tersperses in the ZrO2 material to develop an interlocking network structure, resulting in strengthening effect and leading to an increase in the strength of the composites. The composites have good oxidation resistance due to the formation of some glass film on the sample surface. The optimum firing temperature is 1200 degrees C, which is much lower than that of pure ZrO2 material (>1700 degrees C). The as-prepared ZrO2-SiCw-C materials possess good properties, making good prospects for fabricating insert rings of slide plates.

beta-SiAlON powders were fabricated using Al, Si, alpha-Al2O3 and trace Y2O3 powders as starting materials in flowing nitrogen atmosphere. The effect of Y2O3 on oxidation behavior of the prepared beta-SiAlON powders has been investigated. The results show that the Y2O3 contributed to the generation of beta-SiAlON during the fabricated process. The weight gain ratio of beta-SiAlON in presence of Y2O3 is higher than that of without Y2O3 during non -isothermal oxidation up to 1723 K, which may be due to the Y2O3 dissolving into the lattice of beta-SiAlON resulting in lattice deformation. At the initial oxidation period, the incorporation of Y2O3 increases the oxidation rate and decreases the oxidation activation energy (Ea) of beta-SiAlON due to the lattice deformation increasing the reac-tivity of beta-SiAlON. However, at the final oxidation period, denser glass film formed on the surface of beta-SiAlON because of the incorporation of Y2O3, which reduces the opportunity for O2 contact with beta-SiAlON, thus decreasing the oxidation rate and increasing the Ea of beta-SiAlON.

This work proposes a green method for synthesizing SiC nanowires (NWs) via the chemical vapor deposition (CVD) technique using coconut shell and silicon as raw materials. Using coconut shell as carbon source decreases the synthesis temperature of SiC. A large number of core-shell SiC NWs were obtained after firing at 1200 degrees C, a thin SiO2 layer is distributed on the outer shell of SiC NWs. The synthesized SiC NWs grow along the [111] direction, up to dozens of micrometers in length and diameters of 10-75 nm. However, the chain-bead structure of SiC NWs is formed after firing at 1400 degrees C due to the SiO2 bead embedded in SiC NWs. The synthesized core -shell SiC NWs fired at 1200 degrees C emit strong violet-blue light, which has good application prospects in opto-electronic devices.

The oxidation kinetics of 13-SiAlON with and without impurities synthesized using a-Al2O3, Si, Al, Fe2O3 or TiO2 powders at 1573 K in microwave sintering furnace, were investigated. The initial oxidation temperature of 13-SiAlON with impurities was lower than that sample without impurities. In the initial oxidation stage at 1373-1473 K, the lattice deformation accelerated oxidation rate of 13-SiAlON with impurities. However, in the final oxidation stage, the oxidation rate of 13-SiAlON with impurities was much lower than that of reference sample, because impurities promote glass film formation on surface of 13-SiAlON particles, reducing the chance of 13-SiAlON reacting with O2.

MgO/nano MgAl 2 O 4 core-shell aggregates were prepared using nano-Al 2 O 3 suspension and MgO aggregates by vacuum impregnation method and then heat treated. The MgO/nano MgAl 2 O 4 core-shell aggregates possess excellent hydration resistance and thermal shock resistance (TSR), which are attributed to the in-situ formed MgAl 2 O 4 reducing the contacting area between MgO and water as well as the reduced pore and pore size. The pinning effect of nano-MgAl 2 O 4 and thermal mismatch between MgO and MgAl 2 O 4 contribute to improving TSR of aggregates. The TSR and hot modulus of ruputure were enhanced when the prepared MgO/nano MgAl 2 O 4 core-shell aggregates were introduced into MgO–C slide plate.

The effects of CaCO3addition on phase composition, microstructure, sintering and mechanical properties as well as thermal shock resistance (TSR) of MgO-ZrO2 composites were investigated.The results showed that appro-priate amount(1-3 wt%) of CaCO3addition could promote sintering and enhance the density and cold strength. However, excessiveCaCO3 addition (5 wt%) led to the increased CO2 derived from CaCO3 decomposition, which had slightly negative effect on sintering.The fracture toughness and residual strength ratio of the samples after thermal shock increased with CaCO3addition, indicating that adding CaCO3 could improve TSR of MgO-ZrO2 composites, and the optimum amount of CaCO3 addition was 3 wt%.The improved TSR of MgO-ZrO2 composites in presence of CaCO3was attributed to the micropores formed by CO2 discharging. Meanwhile, crack deflection and branching increased fracture energy and ZrO2 acted as the bridging particles improving the ability to prevent crack propagation of the composites.