Homogeneous Distribution Of Components Research Articles

Thermally-induced diffusion and structural phase transitions in Pt/Mn and Pt/Mn/Pt thin films

We demonstrate the possibility of diffusion formation of the chemically ordered L1 0-MnPt phase through the vacuum annealing of Pt(24 nm)/Mn(20 nm) and Pt(12 nm)/Mn(20 nm)/Pt(12 nm) layered stacks at 400 °C for 30 min. For the bi-layered stack annealed at 400 °C, the effect of Pt atoms segregation at the film/substrate interface was detected, which remained after annealing even at higher temperatures (500 °C and 600 °C) and prevented the whole homogenization of the chemical composition through the film depth. By contrast, for the tri-layered stack annealed at 400 °C, the presence of the additional Pt bottom layer enabled to change the rate and mechanism of reactive diffusion, leading to homogeneous distribution of components and enhanced crystallinity of the ordered L1 0-MnPt phase compared to the bi-layered sample. An explanation of the obtained experimental data is provided based on the fundamentals of mass transfer theory and its quantitative parameters (e.g. activation energy and diffusion coefficients).

Product distribution and conversion mechanism of fossil-based biodegradable plastics during rapid pyrolysis

Fast pyrolysis has emerged as a promising technology for converting fossil-based biodegradable plastics (FBBPs) into clean energy and high-value products with rapid volume reduction and efficient utilisation. The degradation mechanism during pyrolysis is crucial, and different chemical structures and reaction processes directly affect the treatment efficiency and economic benefits. In this study, three typical FBBPs, including poly(butylene adipate-co-terephthalate) (PBAT), polybutylene succinate (PBS) and poly(epsilon-caprolactone) (PCL), have been analyzed in rapid pyrolysis experiments and corresponding products. Being pyrolyzed at 550℃, three kinds of FBBPs exhibited distinctly different decomposition behaviors and characteristics. These differences can be attributed to the bond-breaking ways and pyrolysis mechanisms, which enhance the value of products. Specifically, PBS exhibited the highest abundance of bio-oils and particulate matter (total 90.58%) compared to PBAT and PCL, mainly converted to ketones and acids with a homogeneous component distribution, which was likely to help facilitate further utilisation. In addition, the oxygen of PBS remained in the bio-oil fraction while showing high levels of CO in the bio-gas. Moreover, PCL had the highest amount of bio-gas (21.76%) among the three FBBPs, indicating that it was more likely to break into small molecule products. Notably, the broken chains or macro-molecules of PCL were primarily converted into esters, with di(but-2-en-1-yl) adipate accounting for 57.5% of bio-oils. This work elucidated the transformation pathways and mechanism of FBBP pyrolysis, providing guidance for the treatment and resource utilisation of FBBPs.

Structural, spectroscopi c and laser properties of transparent Tm:YScO3 ceramic based on gas-phase synthesized nanoparticles

Owing to the combination of good thermo-optical properties and inhomogeneously broadened fluorescence spectra suitable for ultrashort laser pulse generation, rare-earth doped solid solutions of sesquioxides (Y,Lu,Sc)2O3 have attracted considerable interest in recent years. In this study, compositionally disordered Tm3+-doped YScO3 transparent ceramic was fabricated using solid-state vacuum sintering of nanopowder produced using laser ablation of solid target in air flow. The as-synthesized powder consisted of weakly aggregated spherical particles having 20 nm diameter and a mostly monoclinic (space group C2/m) crystal structure, whose symmetry was transformed into cubic (space group Ia-3) by calcination at 1050 °C. From high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray analysis (EDX), we observed a homogeneous distribution of components both throughout individual nanoparticles and 100-nm-thick ceramic foil resulting in high structural and optical quality of the obtained samples. The sintered ceramic featured an optical transmission of 77% at 600 nm and above 81% near 2 μm, an average grain size of 24.2 μm and a content of scattering centers of 26.1 ppm. The absorption spectra at several temperatures, from 93 K to 293 K, were measured and the corresponding absorption coefficients were obtained by Lambert-Beer formula in the range from 600 nm to 900 nm and from 1400 nm to 2100 nm. In particular, the room temperature absorption cross section at 794 nm and 1634 nm were determined to be σabs = 4.25 × 10−21 cm2 and σabs = 5.01 × 10−21 cm2 respectively. Concerning the emission cross section it was calculated by Fuchtbauer-Ladenburg equation starting from the fluorescence spectrum acquired at the laser work temperature: at 1951 nm and 2106 nm corresponding to the main two emission peaks belonging the curve, it was found σem = 9.2 × 10−21 cm2 and σem = 4.9 × 10−21 cm2, respectively. Finally, it was tested the laser behavior of the ceramic: pumped at 793 nm in quasi-CW mode it delivered 1.27 W of output power with a slope efficiency of 10.33% at 2081 nm. The tunability curve spans from 1942 nm to 2110 nm (i.e. 168 nm).

Dual composite architectonics: Behavior of ZrB2–SiC–TaB2 composites under abrasive conditions

The influence of abrasive impact on ZrB2–SiC–TaB2 ceramic composites with homogeneous distribution of components in ZrB2 matrix and with «dual composite » structure (ZrB2–SiC)-(TaB2–SiC) has been studied. It was shown that at the same content of components the abrasive wear of the ceramic with the «dual composite » structure is significantly less than that of the composite with homogeneous distribution of single-phase components in a single-phase matrix. On the surface of the studied composites there were no furrows and grooves typical for the abrasive action on the material. At abrasive impact on ceramic composite with homogeneous distribution of components there was a formation of subsurface cracks with the subsequent tearing off of material segments with the size exceeding the size of inclusions in the matrix. Abrasive wear of ceramics with the «dual composite » structure at a high content of composite inclusions occurs by "erosion" of the matrix at the interface with composite inclusions with subsequent removal of inclusions. Composites with «dual composite » structure had higher residual strength compared to ceramic with homogeneous distribution of components. It was found that the difference in the character of abrasive wear of composites is largely in relation to the distribution of residual stresses formed due to the difference in the thermal linear expansion coefficients of the components.

Design of Anti-blocking and Anti-seepage shield grouting materials and their performance enhancement mechanism analysis

To solve the current problems of long-distance pumping blockage and poor stability of shield grouting material in the construction of subway tunnels, we studied the effects of thickener and water reducing type, dosage, and water-to-binder (W/B) ratio on the workability and mechanical properties of shield grouting materials with high-volume crushed sand and ultrafine powder. The mechanism of thickeners' effects on improving mortar properties was analyzed using the cryo-scanning electron microscopy (Cryo-SEM). The results show that proper compatibility of components and proportion optimization make it possible to prepare high-performance shield grouting materials with excellent anti-blocking and anti-seepage properties. These materials exhibit high fluidity, low pressure bleeding rate, homogeneous distribution of components, and meet the engineering requirements regarding setting time and strength of grouting material. A comparison of the performance of three types of thickening agents reveals that although hydroxypropyl methylcellulose (HPMC) improves the pressure bleeding rate of mortar significantly compared to seaweed gum, it leads to a significant delay in the setting time and a decrease in mortar strength. Welan gum (WG) has a minor impact on grouting materials' setting time and strength, and its water retention performance is similar to that of HPMC. However, WG is expensive and causes significant fluidity loss of slurry over time. On the other hand, seaweed gum demonstrates comprehensive advantages in enhancing various aspects of shield grouting materials, exhibiting good anti-blocking and anti-seepage effects. For its calcium-induced gelation property, seaweed gum forms an orderly screen structure of an “egg-box” shape in the pore liquid, then fills the pores between the screens through the film effect of the gel. Finally, the gels form a “screen-printing-like” overall effect, so that seaweed gum has the three-dimensional space network effect as WG and the film forming effect as that of HPMC, which can significantly improve the stability of the grouting material. Therefore, seaweed gum has almost no adverse impact on the strength of shield grouting material but has a relatively lower price.

Biocompatible as-cast and homogenized TiNbTaZrMoV high entropy alloys: mechanical properties, corrosion resistance and in vitro studies

Commercial 316L SS, CoCrMo, and Ti6Al4V alloys have been widely used as implant materials for biomedical applications. However, the inadequate wear resistance and the released metal ions could result in inflammation, cytotoxicity, and shorten the lifespan of surgical implants. To extend the service life and durability of metallic biomaterials, the TiNbTaZrMoV HEA was developed by integrating biocompatibility characteristics with the unique properties of high-entropy alloys (HEAs). Both as-cast TiNbTaZrMo and TiNbTaZrMoV HEAs consisted of dual BCC phases in the dendritic structure: the dendrite region was enriched with Ta, Mo, and Nb, while Zr, Ti, and V were concentrated in the interdendrite region. The homogenized TiNbTaZrMoV HEA possessed a single BCC phase with a homogeneous component distribution. Moreover, the wear resistance of the homogenized TiNbTaZrMoV HEA was superior to the as-cast TiNbTaZrMo and TiNbTaZrMoV HEAs. In terms of electrochemical behaviors, the homogenized TiNbTaZrMoV HEA exhibited superior corrosion resistance compared to the other commercial metallic biomaterials in phosphate-buffered saline solution at 37 °C. The in vitro biocompatibility evaluation revealed that the homogenized TiNbTaZrMoV HEA could support the attachment and proliferation of the MC3T3-E1 cells, presenting good biocompatibility comparable to the Ti6Al4V alloy. This study demonstrated the feasibility of the homogenized TiNbTaZrMoV HEA for orthopedic bioimplant applications.

Spatial inhomogeneity and molecular aggregation behavior in aqueous binary liquid mixtures

The component molecules in aqueous mixtures tend to aggregate with increasing concentration, and it has been conclusively reported that their spatial distribution is no longer uniform. Here, we attempt to measure the spatial inhomogeneity of constituent molecules in the cosolvent-water mixture by calculating the h value wherein the time-varying molecular configurations are obtained from molecular dynamics (MD) simulations conducted at various concentrations and temperatures. The results reveal that the miscible methanol solutions have a small h value, indicating the homogeneous distribution of components, while the immiscible dichloromethane-water mixtures have a relatively large h value, representing the localization of components due to the formation of two separated liquid phases. In the butanol-water mixture, the h value decreases significantly with increasing temperature, which reflects a temperature-dependent phase change from two liquid phases to a single phase, resulting in uniform distribution of molecular components at high temperatures. Meanwhile, in the graph theoretical analysis of cosolvent aggregates and water H-bond network, two prominent types of aggregation behavior are shown in the investigated binary liquid system, i.e., self-associated or spatially extended aggregates. The growth of self-associated cosolvent aggregates facilitates the liquid-liquid phase separation, resulting in a heterogeneous distribution of components with high h values. The development of a spatially extended network enables fully mixing with water H-bond network, bringing about the homogeneous distribution of constituent molecules and thus resulting in low h values. The concept of spatial inhomogeneity and bifurcating hypothesis on aggregation behavior is anticipated to contribute significantly to understanding the underlying issues, such as miscibility and liquid-liquid phase separation in aqueous mixtures.

Determining the influence of the microstructure and phase composition of glass-metal-ceramic coatings on their basic physical-technical properties

Given the development of new heat-resistant nickel alloys that operate at temperatures up to 1,250 °C, as well as the introduction of additive technologies for the production of various parts, it is a relevant task to devise new compositions of highly heat-resistant coatings. Determining the influence of the phase composition of glass-metal-ceramic coatings on its basic properties could improve the effectiveness of protecting those parts that operate under extreme conditions. Therefore, it is promising to conduct a study aimed at establishing the relationship between the microstructure and phase composition of glass-metal-ceramic coatings and the main physical-technical characteristics. This study's results have established that the most high-quality coatings were obtained on the basis of non-crystallizing glass. Such glass is characterized by a temperature coefficient of linear expansion of 92·10-7 degrees-1, a glass transition temperature of 625 °C, and surface tension of 260·10-3 N/m at 850 °C. These properties contribute to the formation of a defect-free coating, providing uniform spreading and high-quality adhesion to the substrate. The resulting optimal coating is characterized by the adhesion strength of 98 %, the thermal resistance (mode 950↔20 °C) of 50 cycles, and the high heat resistance (a weight gain after 100 h in the temperature range of 1,000‒1,050 °C) of 0.03 g/m2·h. Coatings with a minimum amount of glass bonding are distinguished by uniformity and high quality. The optimal ratio of phases "glass:metal-ceramic composition" is 10:90. The structure of the recommended coating is uniform, characterized by the homogeneous distribution of components, the absence of cracks, visible defects, and high quality. The phase composition of the coating after firing is represented by crystals of metallic nickel and silicon, as well as a small amount of residual glass phase.

Retraction Note to: Sintered Aluminum–Graphene Nano-Bio Composite Materials for the Medical Application

It is known that graphene is stronger than steel. It is characterized by extremely high values of the Young's modulus (up to 1 TPa), strength (~125 GPa) and thermal conductivity (~5000 W/(m · K)). Therefore, in this work it is used to obtain nano-bio composite materials aluminum–graphene using powder metallurgy methods, in particular high-energy ball grinding followed by vacuum sintering. Sintered composite materials were evaluated using modern methods of microstructure analysis, such as scanning electron microscopy with field emission (FE-SEM), energy dispersion spectroscopy (EDS), transmission electron microscopy (TEM) and Raman spectroscopy for qualitative and quantitative analysis of aluminum characteristics. According to the results of research, a homogeneous distribution of components is observed in the structure of the material over the given scan areas. The relative density of the composite after sintering is ≈97.5%. Data on the electrical conductivity of aluminum-graphene nano-structured bio-composite materials provide grounds for their use in bone engineering.

Characterization and Properties of CuZrAlTiNiSi High Entropy Alloy Coating Obtained By Mechanical Alloying and Vacuum Hot-Pressing Sintering

The CuZrAlTiNiSi high entropy alloy coating (HEAC) was synthesized on T10 substrate using mechanical alloying and vacuum hot-pressing sintering technique. The results show that the final product of as-milled powders is amorphous HEA phase with homogeneous component distribution. The sintered coating is composed of solid solutions and intermetallic compounds. No pores and defects appear in the HEAC surface, suggesting a good consolidation quality. In addition, the HEAC possesses a good interface bonding, mainly owing to the diffusion of Al atoms from coating to substrate. The average microhardness of the coating reaches 927 HV0.2, and is more than 3 times higher than the substrate (281 HV0.2). The high microhardness can be mainly explained by the second phase strengthening effect and solid-solution strengthening. Furthermore, compared with the substrate, the HEAC exhibits excellent wear resistance with lower friction coefficient, reduction of the wear groove depths and widths, fewer wear volumes, and minimum specific wear rate under the same conditions. Moreover, based on the wider passive region and uniform surface corrosion morphology, the HEAC presents a good pitting resistance in seawater solution.

Transport properties of ceramic composites based on bismuth and indium oxides

Solid solutions based on indium oxide In2-xZrxO3+0.5x (x = 0.005, 0.01, 0.015, 0.02, 0.025, 0.05, 0.075, 0.1) were synthesized and temperature dependences of their conductivity at 25-800 °C were investigated. It was found that In1.985Zr0.015O3.0075 solid solution possessed the highest conductivity of about 100 S/cm at 800 °C. Dense In1.985Zr0.015O3.0075 – 50 vol.% Bi2O3 ceramic composite was obtained and investigated, its microstructure was studied, and the formation of fine-grained structure with homogeneous distribution of components by volume was demonstrated. The total conductivity of composite was measured, and oxygen fluxes for composite 1.7 mm thick membrane at 750-800 °C was obtained. The oxygen flux was found to be 2.4 ×~ 10−7 mol⋅cm−2⋅s−1 at 800 °C when oxygen partial pressures on both sides of membrane was 0.21 atm/0.017 atm, while the oxygen selectivity was more than 20. This indicates thepromising of investigated composite to use as an intermediate-temperature (750800 °C) ion transport membrane for obtaining of pure oxygen from air.

Carbon Nanofiber/Polycaprolactone/Mineralized Hydroxyapatite Nanofibrous Scaffolds for Potential Orthopedic Applications.

Hydroxyapatite (Ca10 (PO4)6(OH)2, HAP), a multimineral substituted calcium phosphate is one of the most substantial bone mineral component that has been widely used as bone replacement materials because of its bioactive and biocompatible properties. However, the use of HAP as bone implants is restricted due to its brittle nature and poor mechanical properties. To overcome this defect and to generate suitable bone implant material, HAP is combined with biodegradable polymer (polycaprolactone, PCL). To enhance the mechanical property of the composite, carbon nanofibers (CNF) is incorporated to the composite, which has long been considered for hard and soft tissue implant due to its exceptional mechanical and structural properties. It is well-known that nanofibrous scaffold are the most-prominent material for the bone reconstruction. We have developed a new remarkable CNF/PCL/mineralized hydroxyapatite (M-HAP) nanofibrous scaffolds on titanium (Ti). The as-developed coatings were characterized by various techniques. The results indicate the formation and homogeneous distribution of components in the nanofibrous scaffolds. Incorporation of CNF into the PCL/M-HAP composite significantly improves the adhesion strength and elastic modulus of the scaffolds. Furthermore, the responses of human osteosarcoma (HOS MG63) cells cultured onto the scaffolds demonstrate that the viability of cells were considerably high for CNF-incorporated PCL/M-HAP than for PCL/M-HAP. In vivo analysis show the presence of soft fibrous tissue growth without any significant inflammatory signs, which suggests that incorporated CNF did not counteract the favorable biological roles of HAP. For load-bearing applications, research in various bone models is needed to substantiate the clinical availability. Thus, from the obtained results, we suggest that CNF/PCL/M-HAP nanofibrous scaffolds can be considered as potential candidates for orthopedic applications.

Thermobaric Sintering of Mechanocomposites of the System Fe-Ga

Alloys of the system Fe-Ga obtained by sintering under high pressure and temperature from mechanocomposites formed during MA (Mechanical activation) in different modes were investigated. Structural studies were carried out by means of X-ray diffraction, optical and scanning electron microscopy. It was demonstrated that the sintered materials inherit the phase composition of mechanocomposites. It was established that sintering at high pressure and temperature leads to further decrease in the size of α-Fe crystallites. The presence of the low-melting component in mechanochemically synthesized precursor after MA for a short time promotes the formation of microstructure according to the liquid-phase sintering mechanism. Sintering of mechanocomposites formed from the solid solution based on α-Fe proceeds according to the solid-phase mechanism with homogeneous distribution of components, and microhardness of these materials increases by a factor of 2.

Detailed Characteristic Comparison between PEN of Planar SOFC Prepared by APS and SPS

On the help of the atmosphere plasma spraying (APS) and suspension plasma spraying (SPS) conditions optimized previously, APS and SPS were both introduced to prepare the PEN (Positive- Electrolyte-Negative) of planar solid oxide fuel cells (SOFCs). Then the microstructure and material components of the PEN cells were analyzed. Experimental results show that the electrolyte layer fabricated by SPS represents higher densification, thinner thickness and more homogeneous component distribution than that manufactured by APS, and meets the microstructure and density requirements of SOFC. The porosities of cathode and anode layers by APS and SPS reached 25%-35%. Therefore, the SPS could be a better and suitable approach to fabricate PENs of SOFC stacks, and effectively improve the conductivity of electrodes.

Ternary sulfur/polyacrylonitrile/Mg0.6Ni0.4O composite cathodes for high performance lithium/sulfur batteries

Nanostructured magnesium nickel oxide (Mg0.6Ni0.4O) was synthesized by a self-propagating high temperature synthesis method followed by heat treatment. The particles of the resulting oxide were used as additives to prepare the sulfur/polyacrylonitrile/Mg0.6Ni0.4O (S/PAN/Mg0.6Ni0.4O) composite via wet ballmilling. The SEM observation revealed that the composite morphology was drastically changed by the addition of Mg0.6Ni0.4O, from smooth bulky particles of S/PAN to rough nanostructured agglomerates with two times the increase in the specific surface area, favouring the reactivity of the composite, and a homogeneous component distribution. Cyclic voltammetry, discharge–charge tests and ac impedance spectroscopy have shown improved conductivity and electrochemical properties of the composite by the addition of Mg0.6Ni0.4O, leading to high sulfur utilization and interfacial stabilization in a Li/S cell upon discharge–charge cycling. The cell demonstrated enhanced reversibility, resulting in a discharge capacity of about 1223 mA h g−1 at the second cycle and retained about 100% of this value over 100 cycles. Furthermore, the S/PAN/Mg0.6Ni0.4O composite cathode exhibited a good rate capability with discharge capacities of 887, 710 and 445 mA h g−1 at 0.5, 0.7 and 1 C, respectively.

Thermal Treatment on Tea Polysaccharide Conjugates Prepared from Green Tea by Extraction of Decoction and Complex Enzyme

Tea polysaccharide conjugates(TPC) named TPC-1 were prepared from low-grade green tea by extraction through complex enzymes method and purified by diethylaminoethyl(DEAE) cellulose(DE-52) column chromatography,while TPC-2 was prepared by extraction with boiling water and purified by Sephadex G-200 column chromatography.TPC-1 and TPC-2 were incubated respectively at 98 ℃ for 5.0 h.A single symmetrical peak corresponding to the main homogeneous component,TPC-1a in the chromatogram of high performance gel permeation chromatography(HPGPC) was split into two adjacent peaks representing two different components of TPC-1a-1 and TPC-1a-2.Circular dichroism(CD) spectra showed an additional positive Cotton effect for the peak at 216 nm along with the peak at 194 nm.HPGPC showed that incubation in water at 98 ℃ for 5.0 h has no effects on TPC-2 that contained two homogeneous components of TPC-2a and TPC-2b.The CD spectra of the treated sample revealed that the positive Cotton effects for peaks at 203 and 215 nm disappeared,while it retained for the one at 272 nm.The solution conformation and homogeneous component distribution of TPC-1 had been changed by heat treatment.But only solution conformation had been changed for TPC-2.

Profile of the refractive index distribution over the depth of (HfO2) x (Al2O3)1 − x films

Capabilities of the method of laser null ellipsometry for the study of optical parameters of thin films of multicomponent alloys are demonstrated. Films of alloys (HfO2) x (Al2O3)1 − x on single-crystal silicon are obtained by the chemical vapor deposition with the use of the following volatile compounds: hafnium dipivaloylmethanate (IV) and aluminum acetylacetonate (III). The selection of initial sets for their optical parameters is justified. The selected model is shown to correspond to experimental data. In films deposited from the mixture of precursors, the refractive index increases from a substrate to a film surface. Due to the separation of sources, films described by a single-layer model were deposited. This fact is indicative of the homogeneous distribution of components over the film thickness.

Nanostructured bulk YbxCo4Sb12 with high thermoelectric performance prepared by the rapid solidification method

High performance nanostructured bulk skutterudites YbxCo4Sb12 (x = 0.1, 0.2, 0.3) have been prepared by combining the melt spinning technique with spark plasma sintering (SPS). The effects of different linear speeds V of the spinning copper wheel on the microstructure and phase composition of ribbon samples and bulk materials are studied, and the influence of the nanostructure and Yb filling fraction on thermoelectric (TE) properties is investigated. The microstructure characterization results show that with increasing speed V, the ribbons possess finer nanostructure and a more homogeneous component distribution. As a result, the formation of the skutterudite phase during a brief SPS processing of the ribbons is very rapid. Moreover, the resulting bulk samples are single-phase, high density skutterudites with nano-scale size grains. The results of TE property measurements show that with the increasing linear speed V, i.e. with the formation of a finer nanostructure, the thermal conductivity of bulk samples decreases markedly without any significant effect on the electronic transport properties. In fact, we observe an enhancement in the Seebeck coefficient as the grain size decreases. The Yb0.3Co4Sb12 compound reaches its highest ZT of 1.22 at 800 K.

Influence of the Precursor Cross-Linking Route on the Thermal Stability of Si−B−C−O Ceramics

The specifics of the cross-linking route of tris(1-(dichloro(methyl)silyl)ethyl)borane to form a preceramic polymer suitable for the subsequent synthesis of Si−B−C−O ceramics has significant influence on the local phase composition and the microstructural features of the resulting samples after their ceramization and subsequent annealing. Cross-linking of tris(1-(dichloro(methyl)silyl)ethyl)borane via hydrolysis used for the preceramic polymer synthesis increases the amount of nanocrystalline SiC in the resulting Si−B−C−O ceramics up to 1400 °C, while cross-linking with polyvalent alcohols allows the homogeneous component distribution to be preserved and the formation of crystalline phases to be retarded. The different contents of bound oxygen in the preceramic polymers, depending on the cross-linking route, may explain the observed different stabilities of amorphous Si−B−C−O against phase separation and crystallization.

Fabrication of Fine Mullite Powders by Heterogeneous Nucleation and Growth Processing

Heterogeneous nucleation and growth was used to prepare composite particles with homogeneous component distribution. Composite particles consisting of α-Al2O3 cores with an outer amorphous homogeneous silica layer were prepared by heterogeneous nucleation and growth processing using an ethanol suspension containing ammonia, tetraethylorthosilicate, and α-Al2O3. Fine mullite powders of average particle size 0.53 μm were fabricated by calcinating the composite particles at 1500°C for 2 h.