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The controllable α/β ratio of Si 3 N 4 powder was synthesized using tetraethyl orthosilicate (TEOS), glucose, MgCl 2 and YCl 3 ·6H 2 O by sol-gel assisted carbothermal reduction and nitridation (CRN). This study aimed to investigate the impact of various parameters, including a H 2 O/TEOS mol ratio of the sol, a C/Si mol ratio, sintering aids, and the temperature of CRN on the phase transformation of α-Si 3 N 4. The results demonstrated that the H 2 O/TEOS ratio significantly influenced the relative content of α and β phase in Si 3 N 4 by changing the morphological characteristics of SiO 2. When the H 2 O/TEOS ratio was 100, β-Si 3 N 4 powder with an approximate β content over 88 wt% was synthesized at 1500 °C. This remarkable phase transformation was likely facilitated by the eutectic liquid phase consisting of MgSiO 3 /Mg 2 SiO 4. The SEM image revealed rod-like whiskers with a length around 1.4 μm for the β-Si 3 N 4 grains. Due to the presence of liquid phase, the synthesis of spherical-like α-Si 3 N 4 nano-powder with an α-phase content of 91 wt% was achieved at a lower temperature of 1450 °C, with an H 2 O/TEOS ratio of 15 and a C/Si ratio of 4. The size of the particles was about 70 nm due to the reduced reaction temperature. Furthermore, without the addition of any sintering aids or Si 3 N 4 seeds, high purity α-Si 3 N 4 with an α phase content approaching 96 wt% could be synthesized at 1500 °C, using an H 2 O/TEOS ratio of 15 and a C/Si ratio of 4. The resulting α-Si 3 N 4 powder exhibited an extremely regular hexagonal prism shape with a length of approximately 2 μm. [Display omitted] [ABSTRACT FROM AUTHOR]

Silicon oxycarbide (SiOC) coatings were prepared through isothermal chemical vapor co-deposition by using two precursors of hexamethyldisilane (HMDS) and tetraethyl orthosilicate (TEOS). The microstructure, composition and the protectiveness on C/C composite against oxidation of the coatings prepared at temperatures ranging from 1423 K to 1563 K and pressures ranging from 500 Pa to 1200 Pa were investigated, respectively. After oxidation, cracks and defects were formed in the coatings of all conditions due to the volume shrinkage of amorphous SiO 2 crystallization and the mismatch of thermal expansion coefficient (CTE) between SiOC coatings and substrate. The most oxidation-resistant SiOC coating was obtained at 1563 K and 500 Pa, which exhibited the lowest weight loss rate of 4.87 % after 12 h of oxidation at 1673 K in air condition. [ABSTRACT FROM AUTHOR]

To overcome the drawback of carbon nanofibers (CNFs) such as the low energy density and low specific capacitance as electrode for supercapacitors, SiO 2 /PANI@CNFs composite was prepared by layer-by-layer (LbL) assembly technique, in which the SiO 2 served as a component for improving capacitive behavior. Polyaniline (PANI) is used as nucleation site for synthesizing SiO 2 particles as well as active material for improving capacitance. In this study, SiO 2 particles were synthesized using biosilicification process as a bioinspired, rapid, and facile synthetic route for SiO 2 particles at ambient temperature and pressure, etc. To elucidate effect of SiO 2 on the electrochemical properties, SiO 2 /PANI@CNFs samples were prepared by varying concentration ratio of tetraethyl orthosilicate (TEOS) to CNFs. It was observed that the specific surface area and the capacitance are highly dependent on the TEOS concentration. The capacitance of the composite prepared at the TEOS concentration of 0.19 mmol reaches 412 F g−1 at the current density of 1 A g−1. These results are attributed to increased specific surface area from interstitial voids between SiO 2 particles and hydrophilic nature of SiO 2 particles, which offers sufficient channels for rapid ion diffusion and leads easy accessibility to the active sites for the electrochemical reaction between electrode and aqueous electrolyte. Due to its excellent electrochemical and biocompatible properties, bioinspired SiO 2 inorganic material will promote the development of energy storage devices in biomedical and environmental electronics. [ABSTRACT FROM AUTHOR]

The 3C–SiC powder or the 3C–SiC/multilayer graphene composite powder was synthesized after 3 h carbothermal reduction reaction in flowing Ar at 1673 K using expanded graphite and Tetraethyl orthosilicate (TEOS) as raw materials and Ni(NO 3) 2 ·6H 2 O as catalyst precursor. Based on these findings, 3C–SiC/multilayer graphene composite ceramics were prepared using a one-step spark plasma sintering(SPS) method. The results showed that the reaction temperature could be reduced to 1673 K when adding 1 wt% Ni. Furthermore, the thickness of the multilayer graphene generated in situ was approximately 3.5 nm with C/SiO 2 molar ratio of 3.5:1. In addition, the water wettability of the 3C–SiC/multilayer graphene composite powders was significantly improved. Furthermore, the hardness of the 3C–SiC/multilayer graphene composite ceramic prepared by the addition of Ni catalyst was enhanced compared to the situation without any catalyst and there was no obvious agglomeration in the ceramic structure. The method of in situ ceramic phase dispersing graphene could solve the agglomeration and high costs of preparation and extended to develop a wide range of applications of graphene. [ABSTRACT FROM AUTHOR]

In this study, a hybrid filler comprising cellulose nanofiber (CNF) and boron nitride (BN) (CNF-BN) was fabricated through the ball milling exfoliation method by introducing oxalic acid to provide hydroxyl groups, leading to better compatibility between CNF and BN via hydrogen bonding. After functionalization and CNF grafting, the filler was dispersed sufficiently into the CNF matrix with tetraethyl orthosilicate for chemical crosslinking. The c–CNF–BN/CNF film was then fabricated by vacuum infiltration. The voids and defects of the film surface decreased due to the tangled cellulose nanofiber with the help of a crosslinking agent, facilitating the construction of an efficient heat pathway. As a result, the through-plane thermal conductivity increased from 0.5 W m − 1 K − 1 to 1.69 W m − 1 K − 1 with 37.5 vol% BN loading, showing a thermal conductivity enhancement of 238% compared to the raw CNF film. Additionally, the mechanical property was also enhanced. The tensile stress was 42.2 MPa and elongation at break was 36.8%. Thus, the c–CNF–BN/CNF film can be used as a composite for efficient thermal management in electronic devices. [ABSTRACT FROM AUTHOR]

The preparation and study of new bifunctional (Y 0.9 Ln 0.1 VO 4 /Fe 3 O 4)@SiO 2 and [(Y 0.9 Ln 0.1 VO 4 @SiO 2)/Fe 3 O 4 @SiO 2 ] samples with Ln = Nd or Tb is described in detail. The influence of Fe 3 O 4 content and silica coating on Y 0.9 Ln 0.1 VO 4 @SiO 2 samples is analyzed to decide on their potential utility. Materials of this type are currently of great interest in the biomedicine field based on their potential use as bifunctional materials. On the one hand, because they can be directed using an external magnetic field and, on the other, because they can allow the visualization of diseased cells after appropriate functionalization. Y 0.9 Ln 0.1 VO 4 samples with Ln = Nd or Tb were prepared by a hydrothermal process, while Fe 3 O 4 sample was prepared by the coprecipitation method. These samples and different mixtures of them were treated with tetraethyl orthosilicate (TEOS) to proceed with their silica coating. All diffraction maxima of Y 0.9 Ln 0.1 VO 4 samples were indexed on a tetragonal symmetry of space group I4 1 /amd, compatible with a zircon structure-type. In the case of Fe 3 O 4 sample, all reflections were indexed to a cubic symmetry of space group Fd 3 ‾ m, characteristic of an inverse spinel structure-type. These results also agreed well with the FTIR spectra of the investigated samples. For the first time, the experimental FTIR study of Y 0.9 Ln 0.1 VO 4 samples was complemented with a theoretical vibrational study based on the YVO 4 structure. To carry out this theoretical study, different density functional theory (DFT) methods and different basis sets were used. Silica presence in samples was clearly verified in both, the XRD profiles and the FTIR spectra. Elongated and spherical particles are found in TEM images of these samples. The study of PL emission and magnetic behavior showed that [(Y 0.9 Ln 0.1 VO 4 @SiO 2)/Fe 3 O 4 @SiO 2 ] samples are the most suitable for use as bifunctional materials. [ABSTRACT FROM AUTHOR]

We report three routes for the synthesis of CaO-MgO-SiO 2 (CMS) bioceramic powder using different Si sources and synthesis procedures. The ceramic powders were synthesized from Na 2 SiO 3 waste solution by the sol-gel process combined with co-precipitation (synthesis route I and synthesis route II), and from TEOS (tetraethyl orthosilicate) by conventional sol-gel (synthesis route III). Ceramic powders of the CMS multiphase system were obtained, including diopside, wollastonite, akermanite, monticellite and merwinite, which are suitable for application as biomaterial. These powders were sintered at 1200 °C for 2 h to obtain the CMS ceramics. The ceramics mostly contained diopside and wollastonite crystalline phases. Those ceramics when submitted to cytotoxicity tests revealed to be non-cytotoxic, according to ISO10993-5:2009. The ceramics were tested for in vitro bioactivity while soaked in simulated body fluid (SBF) solution. After 14 days, the presence of hydroxyapatite particles on the surface of ceramics was confirmed by Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM) micrographs. The surfaces were completely covered with hydroxyapatite, after 21 days. In summary, CaO-MgO-SiO 2 (CMS) ceramic powder derived from three routes of synthesis have potential application in the biomedical area. However, further in-vitro and in-vivo studies are needed. [ABSTRACT FROM AUTHOR]

The formation of micro-cracks in Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode particles is an extremely important factor affecting the electrochemical characteristics after long-term cycling. Generally, cracks can be divided into intergranular crack and intracrystalline crack according to their positions. Coating has been confirmed as a highly effective strategy to relieve intergranular cracks. However, the intracrystalline cracks of primary-like particles have rarely been studied. In this work, ethoxy functional polysiloxane (EPS) was directly coated on the surface of original NCM811 by tetraethyl orthosilicate (TEOS) hydrolytic polycondensation method without any additives. Then, the microstructure, micromorphology, surface state and electrochemical properties were investigated in detail by XRD, SEM, TEM, CV and EIS. The results displayed that the micro-cracks of primary-like particles were effectively suppressed under appropriate EPS coating. Accordingly, excellent capacity retention of 95.6% (100 cycles, 1C) and rate performance (144.6 mA h/g, 5C) were obtained. These improved mechanical and electrochemical properties are considered to be related to the EPS stress buffer layer, suppressed oxygen vacancies, inhibited phase transition and reduced volume change. [ABSTRACT FROM AUTHOR]

A functional Fe 3 O 4 /SiO 2 core–shell abrasive was synthesized via hydrolysis of tetraethyl orthosilicate. A silica shell was successfully coated on a Fe 3 O 4 core, resulting in a core-shell particle with an average diameter of 140 nm. The prepared core–shell abrasives was utilized for ultrasound-assisted magneto-rheological polishing (UAMP) of sapphire substrate. The experimental results showed that the Fe 3 O 4 /SiO 2 core–shell abrasives exhibited a remarkable polishing performance for the sapphire material, resulting in smooth and detect-free surfaces with a high material removal rate (MRR) compared to mixed abrasives (Fe 3 O 4 and SiO 2) and pure Fe 3 O 4 particles. The application of ultrasonic vibration to the sapphire wafer further improved the MRR, which was approximately 3.4 times higher than that of traditional magneto-rheological polishing. The largest MRR (1.974 μm/h) and comparatively low surface roughness (0.442 nm) of the polished sapphire wafer were achieved by UAMP with the Fe 3 O 4 /SiO 2 core–shell abrasives. The polishing mechanism of the sapphire wafer is discussed in terms of chemical reactions and mechanical polishing. [ABSTRACT FROM AUTHOR]

We developed hollow mesoporous silica nanospheres by a sol-gel process utilizing pentablock copolymer templates poly(lactic acid- co -glycolic acid)- b -poly(ethylene oxide)- b -poly(propylene oxide)- b -poly(ethylene oxide)- b -poly(lactic acid- co -glycolic acid) (PLGA- b -PEO- b -PPO- b -PEO- b -PLGA) under acidic aqueous conditions. Four kinds of water-soluble pentablock copolymers were used as structure-tuning agents and tetraethyl orthosilicate (TEOS) was used as a silica precursor. Hollow mesoporous silica nanoparticles were prepared at room temperature without any additive salts, which is the main key issue compared with the other reports. The hollow structure was found when pentablock copolymer with longer chain length was used, while a bimodal pore structure was obtained using shorter copolymer templates. Moreover, hydrothermal stability for the hollow mesoporous silica samples was investigated inside distilled water at 100 °C for 28 d. It is noteworthy that pore structure and morphology were varied depending on the length scale of pentablock copolymer templates and the hollow mesopore structure was obtained from single- and partially bridged micelle templates at room temperature. [ABSTRACT FROM AUTHOR]

TiO 2 oxide was deposited on a microstructured α-Al 2 O 3 ceramic hollow fiber substrate by a simple one-step solution-immersion process with tetraethyl orthosilicate (TEOS) as a binder. The effects of the starting coating solution's composition on the photocatalytic properties of TiO 2 powders deposited on a substrate was determined by using TiO 2 -supported Al 2 O 3 ceramic hollow fiber substrates fabricated from coating solutions with different compositions and examining the substrates' effect on the methylene blue (MetB) degradation reaction under ultraviolet light. A strong correlation was observed between the initial coating solution compositions and the final photocatalytic characteristics of the TiO 2 -supported Al 2 O 3 ceramic hollow fiber substrates. Under optimal conditions, the MetB removal efficiency reached about 91% in a few minutes. To the best of our knowledge, this is the highest and most rapidly attained MetB removal efficiency reported for TiO 2 -supported Al 2 O 3 ceramic hollow fiber substrates. Furthermore, apart from attaining an extremely high photocatalytic activity within minutes, the fabricated TiO 2 -supported Al 2 O 3 ceramic hollow fiber substrates exhibited high photocatalytic stability even after several cycles. [ABSTRACT FROM AUTHOR]

A novel precursor of SiC prepared by mixing boron phenolic resin and hydrolytic solution of tetraethyl orthosilicate was employed to fabricate the ablation-resistant C/C–SiC composites. The pyrolysis behaviors of precursor and the ablation properties of prepared composites were discussed. Results show that during the pyrolyzation process of the precursor, the carbon phase was evenly surrounded by the silica phase, benefitting the occurrence of the carbothermal reaction. The precursor was totally transformed into SiC with the carbon left (7.77–8.11 wt%) after heating at 1600 °C. Due to the unique surrounded structure between the carbon and silica phases, part of the residual carbon was encircled by the generated SiC ceramics. During ablation, the carbon nucleus played a positive role in enhancing ablation resistance of composites by hindering the flow of molten silica. Compared with the composites employed polycarbosilane as precursor, this prepared C/C–SiC composites exhibited a decent anti-ablation performance. [ABSTRACT FROM AUTHOR]

In this study, core – shell-structured Fe 3 O 4 @SiO 2 nanoparticles were synthesized using sodium silicate (Na 2 SiO 3), which is more suitable for mass production than the conventional silane precursor tetraethyl orthosilicate (TEOS). In the particle-surface coating process to form a core–shell structure with Fe 3 O 4 , the Na 2 SiO 3 was neutralized with HCl(aq) to form silane groups, and the resulting silane groups combined with hydroxyl groups (OH − ) present on the surfaces of the Fe 3 O 4 nanoparticles. Because of the core–shell nanostructure of the single particles, the Fe 3 O 4 nanoparticles were accompanied by significant changes in their intrinsic physicochemical properties. In addition, it was confirmed that there were differences in the thickness of the SiO 2 under different neutralized pH conditions for the coating-layer implementation with Na 2 SiO 3. The behavior of the Fe 3 O 4 nanoparticle characteristics with respect to the SiO 2 coating-layer thickness was primarily due to changes in the surface properties, associated with the degree of cathodic increase of the surface charge. An intensified negative surface charge enhanced the dispersibility of the particles in aqueous solution with enhanced electrostatic repulsion, which was even higher than that of the conventional TEOS-coated nanoparticles. In addition, the surface coating of SiO 2 caused a decrease in magnetization with an increase in the coating-layer thickness, which was comparable to the general tendency associated with increasing the weight per unit particle. However, it was somewhat superior to those of the conventional TEOS method because of the difference in morphology. [ABSTRACT FROM AUTHOR]

The present study was aimed at determining kinetics of inhibition of bacterial growth by 52S4.6 Nano bioactive glass (Nbg) particles prepared via acid hydrolysis mediated sol-gel method using tetraethyl orthosilicate (TEOS), triethyl phosphate (TEP), calcium nitrate tetrahydrate (Ca(NO 3) 2 •4H 2 O), sodium nitrate (NaNO 3) as precursors. Synthesized Nbg powders exhibited a very narrow size distribution of about 1–2 nm primarily because of high zeta potential of about 39 mv with predominating amorphous phase as obtained from XRD data and SAED pattern. Minimum inhibitory concentration of Nbg was determined to be 15 mg/ml for Escherichia coli (E. coli) and 15–20 mg/ml for Staphylococcus aureus (S. aureus) respectively, after 72 h of incubation. The inhibition was primarily because of ions released that increased osmolarity, osmotic pressure and the pH of the culture media from 7.2 to 10.1 over the period of 168 h of incubation. [ABSTRACT FROM AUTHOR]

SiO 2 –C precursors with various surface areas were derived from tetraethyl orthosilicate and phenolic resin as Si and C sources, respectively, by a modified sol–gel process using the in situ precipitation of phenol resin in a prepared wet gel. The surface area of the SiO 2 –C precursors was varied from 20 to 175 m2/g by changing the C/Si molar ratio in the preform. β-SiC powders were synthesized using carbothermal reduction in vacuum at the temperature range of 1200–1600 °C. The effects of the temperature and heat treatment time as well as that of the surface area of the preform on the formation of β-SiC powders were studied. It was determined that the formation of β-SiC started at 1200 °C and was considerably promoted as the heat treatment temperature and time further increased during the carbothermal reduction of SiO 2 –C preforms with high surface area. When high surface area SiO 2 –C preforms were used, highly crystalline SiC powders were synthesized at 1600 °C in vacuum with a high yield of 85%. [ABSTRACT FROM AUTHOR]

This work presents the tailoring of distinct titania (titania oxide) (TiO 2) crystal structures inside the mesoporous silica and organosilica using several different block copolymer templates in acidic aqueous solution with different acidity. Different crystal structures of TiO 2 have been obtained as rutile and anatase phases, mainly depending on the chemical composition of block copolymer templates used in this study. A PEO-PLGA-PEO (EO 17 (L 28 G 7)EO 17 , LGE54) triblock copolymer, as well as typical Pluronic P123 (EO 20 PO 70 EO 20) and F127 (EO 106 PO 70 EO 106) triblock copolymers was employed as structure-directing templates for the sol-gel reaction of silane precursors. As silica and organosilica precursors, tetraethyl orthosilicate (TEOS), 1,2-bis(triethoxysilyl)ethane (BTEE), and 1,4-bis(triethoxysilyl)benzene (BTEB) were utilized with a titanium butoxide precursor. The crystal structure of TiO 2 and its corresponding band gap were investigated using X-ray diffraction (XRD) and ultraviolet–visible spectroscopy (UV–vis) measurements, respectively. Anatase crystalline phase of TiO 2 was found in the mesoporous sample prepared with Pluronic copolymer (i.e. P123 and F127) templates. On the other hand, the rutile phase was developed only in mesoporous samples prepared with an LGE54 PEO-PLGA-PEO triblock copolymer template. It was found the TiO 2 crystal structure is varied mainly depending on the polymer template under various strong acidic conditions. It seems that a thermodynamically more stable rutile phase can be formed using a more hydrophobic LGE54 template which supplies stronger micelle core as a platform. Further, it is known that the incorporation of TiO 2 in mesoporous silica and organosilica samples induces the conduction activity, especially toward the blue light region. Thus, this work can be applied to produce effective blue region semiconductor material with different crystallite structures by tuning the precursors and copolymer templates. Crystal structure and band gap of titania in mesoporous silica and organosilica particles was tuned mainly by block copolymer template during sol-gel reaction. Image 1 [ABSTRACT FROM AUTHOR]

Yttrium silicate powders were synthesised through acid catalysed sol-gel route using Y(NO 3) 3.6H 2 O and tetra ethyl ortho silicate (TEOS) as precursors. The crystallographic phases evolved from the prepared gel on calcination at 1100°C were correlated with the experimental parameters used for synthesis. The optimised experimental condition resulted in well defined and crystallised phases of Yttrium disilicate (YDS), yttrium monosilicate (YMS) and biphasic mixture (YDS + YMS) powders on calcinations to 1100°C to 1500°C for 2 h. Surface morphology and structure of the final powders were investigated by XRD, SEM, particle size analysis, FTIR and Raman spectroscopy. The powders show particle size in the range 0.8 μm to 10μm. The YDS, YMS and YDS + YMS powders were pelletised and sintered at 1400°C for 2 h leading to 83 ± 1% dense products. [ABSTRACT FROM AUTHOR]

Ceramic nanofibers prepared via precursor sol-gel electrospinning and calcination are widely reported, but few reports address the possible formation of core-shell structured ceramic nanofibers. In this study, core-shell structured calcium silicate (CS) nanofibers were obtained by changing the compositions of the precursor sol-gel solutions and the calcination temperatures to determine the mechanism leading to the core-shell structure during preparation. The sol-gel solutions used to produce CS nanofibers were prepared from calcium nitrate and tetraethyl orthosilicate, and it was found that CS nanofibers prepared from sol-gel solutions with a Ca/Si molar ratio of less than 1:1 displayed a distinguishable core-shell structure with calcination temperatures higher than 1000 °C. The fiber shell was identified as mainly silica with sparse calcium, and the fiber core was composed predominantly of calcium silicate. A tubular morphology was clearly observed with preferential degradation of the fiber core. The fiber shell became thinner or it disappeared if the precursor sol-gel solutions had Ca/Si molar ratios higher than 1:1 or if the applied calcination temperature was less than 1000 °C. After doping the CS fibers with zinc, it was confirmed that the zinc was also predominantly located in the fiber core, similar to calcium. It was proposed that the formation of CS nanofibers with a surface silica layer resulted from the migration of Si-O-Si precursor gel particles toward the fiber surface with solvent evaporation during electrospinning and transformed into a silica shell during calcination. Thus, the calcium (or zinc) elements were enriched inside the fiber to obtain a type of heterogeneous CS nanofiber. These materials are expected to serve as good biomaterials for bone regeneration by providing sustained release of bioactive ions. Image 1 • Calcium silicate (CS) nanofibers are fabricated via precursor sol-gel electrospinning and calcination. • Core-shell structured CS nanofibers are obtained using specific Ca/Si molar ratios and calcination parameters. • The shell is composed mainly of silica, whereas ions such as Ca2+ and doped Zn2+ are predominantly located inside the core. • These CS nanofibers can supply sustained release of bioactive ions that target bone regeneration. [ABSTRACT FROM AUTHOR]

The development of flexible ceramic nanofibers has attracted much attention because they may be able to overcome the intrinsic brittleness of ceramics and thus be applied towards air/water filtration media. Yttria-stabilized zirconia/silica (YSZ/silica) nanofibers with excellent flexibility could be prepared through (1) sol-gel, (2) electrospinning, and (3) calcination processes. Our research focused on the effect of ceramic precursor concentrations [tetraethyl orthosilicate (TEOS) and zirconium (IV) propoxide (ZrP)] on improving the flexibility of YSZ/silica nanofibers. By adjusting the TEOS and ZrP concentrations, two major parameters (grain size and fiber diameter, respectively) can be controlled. It was consequently revealed that smaller grain size and larger fiber diameter could increase the flexibility of YSZ/silica nanofibers. In addition, flexible YSZ/silica nanofibers successfully performed as microfiltration (MF) membranes, while exhibiting high pure water permeability and a high rejection rate (%) for polymeric nanoparticles. [ABSTRACT FROM AUTHOR]

SiC/SiO 2 coated graphite was prepared via a combined sol-gel coating and catalytic conversion route, using graphite flake and tetraethyl orthosilicate as the starting materials, and Fe(NO 3) 3 ·9H 2 O as the catalyst precursor. X-ray diffraction analysis and microstructural examination revealed that a homogeneous coating comprising SiC and cristobalite (SiO 2) and covering the whole surface of graphite was formed. As prepared SiC/SiO 2 coated graphite exhibited better oxidation resistance and water wettability than its uncoated counterpart. Also, oxidation resistance and slag corrosion resistance of a model Al 2 O 3 –C castable using coated graphite as a carbon source were better than in the case of its counterpart using uncoated graphite. [ABSTRACT FROM AUTHOR]

We demonstrated metal-organic chemical vapor deposition of single-phase MgSiO 3 -orthopyroxene (-opx) and α-Mg 2 SiO 4 films, and α-Mg 2 SiO 4 –MgO composite films with self-oriented growth on a polycrystalline AlN substrate using Mg acetylacetonate and tetraethyl orthosilicate precursors. We obtained (020)-oriented MgSiO 3 -opx films, (002)-oriented α-Mg 2 SiO 4 films, and (021)-oriented α-Mg 2 SiO 4 –(200) MgO composite films at 22, 46, and 81 mol%MgO, respectively, at a deposition temperature of 1200 K and a total chamber pressure of 0.8 kPa. Maximum deposition rates of 42 and 131 μm h−1 were attained for the (020)-oriented MgSiO 3 -opx and (002)-oriented α-Mg 2 SiO 4 films, respectively. [ABSTRACT FROM AUTHOR]

Abstract In this work, we reported the synthesis of monophasic boron-containing mullite (MBM) fibers using basic aluminum acetate (BAA) and tetraethyl orthosilicate (TEOS) as starting materials and performed a comparative study between our newly synthesized MBM and commercial Nextel™ 312 fibers. The morphology and the tensile strength are investigated for the new MBM fibers. Continuous and uniform green fibers with a smooth surface were produced via hand drawing method. After the pyrolysis process, amorphous inorganic MBM fibers with a tensile strength of 1.18 ± 0.17 GPa were obtained. After various heat treatment processes (1000–1400 °C for 1.5 h), we found the mullite formation temperature is within the temperature range from 1050 to 1075 °C for both MBM and Nextel™ 312 fibers. However, the results show that the MBM fibers fabricated in this study have a better thermal stability than Nextel™ 312 fibers despite the fact both have the same chemical composition. The improved stability of our MBM fibers is owing to their higher Al 4 B 2 O 9 formation temperature and lower Al 18 B 4 O 33 decomposition rate in comparison to those of Nextel™ 312 fibers. Moreover, the newly synthesized MBM fibers have more stable microstructure and less loss in tensile strength at elevated temperatures. [ABSTRACT FROM AUTHOR]

Abstract In this work, we present a comparative study on the non-isothermal crystallization kinetics for electrospun 3AB2S nanofibers prepared using colloidal silica (CS) and tetraethyl orthosilicate (TEOS) as silica sources. As-spun nanofibers with subequal mean diameters were obtained. Compared with those synthesized through CS, 3AB2S nanofibers prepared using TEOS have higher element homogeneity as a result of the simultaneous hydrolysis of Al and Si. They also show lower crystallinity, smaller mean grain size, higher crystallization temperature and higher activation energy owing to the stronger hindrance effect of uniformly distributed amorphous SiO 2 on the reaction between Al 2 O 3 and B 2 O 3. Avrami constants values for Al 4 B 2 O 9 crystallization together with TEM observations reveal an interface-controlled growth mechanism with instantaneous nucleation for both silica sources. However, those results indicate a two-dimensional grain growth when CS was used and a three-dimensional grain growth in the case of TEOS. [ABSTRACT FROM AUTHOR]

Abstract Silicon carbide (SiC) crystals were synthesized by microwave sintering using coal and tetraethoxysilane (TEOS) as raw materials. A sol-gel method was carried out to coat coal mineral particles with silicon dioxide (SiO 2). The mixed raw powders were pre-formed by uniaxial pressing into cylindrical pellets in dimension of ~ 30 × 3 mm2. The pre-forming pressure was selected at 0 MPa, 1 MPa, 2 MPa, 3 MPa, 4 MPa and 5 MPa respectively, which led to different apparent density of the green pellets. The influence of apparent density of green pellets on microwave heating behavior was investigated. Different microwave thermal effects were analyzed. Techniques of XRD、SEM were carried out to characterize samples. It was found that pre-forming pressure showed crucial influences on microwave thermal effects and electric field (E-field) intensification. No SiC crystal could be formed without pre-forming pressure. Pre-forming pressure might be the prerequisite for synthesis of SiC by microwave heating. Five consecutive and indispensable heating stages including accumulation of residual air, microwave plasma generation, complex chemical reactions, nucleation and grain growth of SiC crystallites could be distinguished for samples under pre-forming pressure. Different pre-forming pressure leads to changes in heating behavior as well as morphologies of SiC crystals. ~ 4 MPa might be the optimized pre-forming pressure for both microwave plasma effects and E-field intensification. [ABSTRACT FROM AUTHOR]

All-inorganic perovskite nanocrystals have held great promise as incredibly effective luminescent materials and also have been synthesized efficiently by room temperature approaches. Toluene, a high toxicity solvent, is often used as a valid antisolvent in ligand-assisted reprecipitation strategy, which badly restricts the commercial application of this convenient method. Here, aiming to address the toluene toxicity issue, the low toxic tetraethyl orthosilicate (TEOS) is employed as a new alternative antisolvent to achieve high uniform and composition dependent luminescent all-inorganic perovskite Cs 4 PbX 6 (X = I, Br, Cl) combined with CsPbX 3 (X = I, Br, Cl) nanocrystals with tunable emission large-span wavelengths (626–437 nm) and remarkably narrow full width at half-maximum (FWHM) monochromaticity (down to 19 nm). Meanwhile, the ratio of CsBr to PbBr 2 is proved to be a critical factor to control the crystalline phase of the resulting perovskite nanocrystals. Additionally, one monochromatic light-emitting diode (LED) lamp with brightly pure green emission is fabricated based on bromine-based perovskite nanocrystals. This newly developed low toxicity antisolvent synthesis (LTaS) is suitable candidate for commercial production in an environmentally-friendly way, and the as-obtained perovskite materials with superior optical merits will be brought to the forefront of lighting and displays. [ABSTRACT FROM AUTHOR]

This study reports on the preparation of diiron boride (Fe 2 B) powders via mechanochemical synthesis (MCS) followed by a purification step and on the embedment of pure Fe 2 B nanoparticles into silica (SiO 2 ) nanospheres. Fe 2 O 3 , B 2 O 3 and Mg powders used as starting materials were blended in stoichiometric amounts and mechanochemically synthesized up to 7 h in a high-energy ball mill. As-synthesized powders were purified from the undesired Mg-based by-products by HCl leaching. After that, pure Fe 2 B nanoparticles with sizes of smaller than 40 nm were embedded in SiO 2 nanospheres using a tetraethyl orthosilicate (TEOS) and ammonia (NH 3 ) containing solution. Characterization investigations of the as-synthesized, leached and SiO 2 -embedded powders were carried out using X-ray diffractometer (XRD), scanning electron microscope/energy dispersive spectrometer (SEM/EDS), particle size analyzer (PSA), transmission electron microscope (TEM), Fourier transform infrared spectrometer (FTIR) and vibrating sample magnetometer (VSM). The average particle size of the Fe 2 B incorporated SiO 2 nanospheres was measured as about 330 nm. Magnetic measurements revealed that pure Fe 2 B powders and their SiO 2 -embedded samples had soft ferromagnetic behaviour with coercivity of 125 and 168 Oe, respectively. [ABSTRACT FROM AUTHOR]

Hollow silica microspheres (HSMs) have been successfully synthesized in large quantities using colloidal carbon spheres (CCSs) as template, cetyltrimethylammonium bromide (CTAB) as modifying agent and tetraethylorthosilicate (TEOS) as silicon source. The CCSs are fabricated by a simple hydrothermal treatment of D -glucose, which exhibit well monodisperse and homogeneous in dimension. The CTAB effectively modifies the surface charge characteristics of CCSs, which provides a favorable circumstance for the deposition of TEOS hydrolysis products. The HSMs can be eventually obtained after CCSs and CTAB being removed by sintering. The as-prepared HSMs are nearly uniform in dimension with particle size of about 500 nm. Porous silica ceramics with a three-dimensional network structure is prepared using these HSMs as raw material. Such ceramics possesses low density and dielectric constant, which make it very potential in the application of lightweight or low dielectric materials. [ABSTRACT FROM AUTHOR]

In this work, pure aluminum oxide nanoparticle was obtained by the chemical method at low temperature. In this approach, alpha-alumina nanoparticle was prepared by aluminum nitrate nonahydrate and triethanolamine (TEA) as the Al 3+ and both gel agent, respectively. FESEM images show that TEA has better efficiency in controlling particle size and agglomeration as compared with citric acid as a chelating agent. Then, yttrium aluminum garnet (YAG) powder was prepared by yttrium nitrate, urea, and tetraethyl orthosilicate (TEOS) as a Y 3+ , precipitation agent, and flux agent, respectively. Furthermore, results show that by using TEOS, the YAG particles were obtained, while in the absence of this agent, the impurely YAG phase was achieved at the simillar annealing temperature. [ABSTRACT FROM AUTHOR]

Crack-free silicon oxycarbide (SiOC) aerogel monolith was fabricated by pyrolysis of precursor aerogel prepared from triethoxyvinylsilane/tetraethoxysilane (VTES/TEOS) using sol-gel process and ambient drying. Effects of different precursors, the amount of base catalyst (NH 4 OH) and the heating rate during pyrolysis on the properties such as monolithicity, bulk density, surface area and pore size distribution of aerogels were investigated. The results show that the crack-free SiOC aerogel can be easily obtained from VTES/TEOS as compared to that of methyltriethoxysilanes/tetraethoxysilane (MTES/TEOS) and phenyltriethoxysilanes/tetraethoxysilane (PhTES/TEOS) precursors. The influence of heating rate during pyrolysis process on shrinkage rate, ceramic yield and surface area of the SiOC aerogels could be ignored, while the variation in the amount of NH 4 OH exerted a strong impact on the properties of SiOC aerogels. Increasing the amount of NH 4 OH resulted in the decrease of bulk density and surface area of SiOC aerogels from 0.335 g/cm 3 and 488 m 2 /g to 0.265 g/cm 3 and 365 m 2 /g. The resultant SiOC aerogels exhibit high compressive strength (1.45–3.17 MPa). 29 Si MAS NMR spectra revealed the retention of Si-C bond in the SiOC aerogels after pyrolysis at 1000 °C. The present work demonstrates VTES/TEOS is a promising co-precursors to easily and low cost synthesize large size SiOC aerogel monolith. [ABSTRACT FROM AUTHOR]

This research was aimed to develop a novel multifunctional SiO 2 –TiO 2 composite coating for application in the field of outdoor sandstone conservation. The SiO 2 –TiO 2 composite coating derived from the sol–gel reaction of tetraethoxysilan (TEOS) and tetrabutyl orthotitanate (TBOT). Hydroxyl-terminated polydimethylsiloxane (PDMS-OH) and poly(ethylene oxide)-poly(phenylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO, F127) surfactant were added to the SiO 2 –TiO 2 based materials. The contact angle analysis, scanning electron microscopy measurement, stain resistant test, salt crystallization test and outdoor exposure test were conducted to investigate the effectiveness and durability of this composite coating. Results showed that SiO 2 –TiO 2 composite materials created a hydrophobic, crack-free coating with self-cleaning and antibacterial properties on the decayed sandstone surface, allowing their use for practical outdoor sandstone conservation applications. [ABSTRACT FROM AUTHOR]

The structural order and stability of spherical SBA-15 silicas synthesized under acid conditions were evaluated as a function of surfactant Pluronic 123 (P123), tetraethyl orthosilicate (TEOS), and hydrochloric acid (HCl) concentrations in the initial gel composition. Also, the effect of temperature and reaction time was studied. Samples were characterized by small angle X-ray diffraction (SAXS), nitrogen adsorption–desorption analyses, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that synthesis conditions affect the structural order and stability of the SBA-15 silicas. These silicas exhibited an ordered pore structure and regular spherical morphology with size from 2 to 5 µm. [ABSTRACT FROM AUTHOR]

Thermal insulation material made by hollow glass microspheres (HGM) with different content of aluminum–chrome–phosphate solution (ACP) and tetraethyl orthosilicate (TEOS) as binders was formed, dried and sintered at 250 °C, 450 °C or 650 °C for 2 h. Properties such as density, compressive strength, thermal conductivity and microstructure of the specimens were determined. It is found that TEOS improved the distribution of ACP and increased the compressive strength of the specimens. HGM bonded by appropriate amount of ACP and TEOS achieved preferable value of density, compressive strength and thermal conductivity which were significant for thermal insulation materials. The compressive strength of specimens sintered at 450 °C and 650 °C was higher than that of the specimens sintered at 250 °C. [ABSTRACT FROM AUTHOR]

Tb 3 Al 5 O 12 (TAG) transparent ceramics were fabricated by solid state reaction and vacuum sintering using ethyl orthosilicate (TEOS) combined with different quantities of MgO as the sintering aids. All the samples showed high transparency and the XRD results presented no secondary phase. The experimental results showed that TEOS combined with MgO can improve the optical properties and the highest optical transmittance was above 80% in the region of 550–1500 nm. The optimal amount of MgO was 0.1 wt% and the corresponding sample exhibited nearly pore-free and uniform-grain-size microstructure. [ABSTRACT FROM AUTHOR]

Calcium silicates have proven to be potential candidates for biomedical applications because of their osteogenic properties. Sol–gel methods are typically used for the preparation of calcium silicate powders. However, in the sol–gel route, an acid or base and ethanol are used to catalyze the precursors. From the perspective of green chemistry, it is better to avoid the use of organic solvents. The objective of this study was to prepare calcium silicate powders using a green synthesis route (hydrothermal method) without organic solvents. The powders were also prepared via the sol–gel process using tetraethoxysilane (TEOS) and calcium nitrate as the raw materials for the purpose of comparison. The powders were sintered at temperatures ranging from 600 to 1000 °C after the application of both methods. To understand the feasibility of using the resulting materials in medical applications for bone repair, the powders were mixed with water to form cements. The results indicated that the powder composition was not significantly affected by the different techniques but was dependent on the Ca:Si ratio of the precursors and on the sintering temperature. The different techniques produced no differences in powder morphology. In addition, the setting times of the powder-derived cements were found to be independent of the sintering temperature and synthesis technique, but it was affected by the Ca:Si ratio of the precursors. The mechanical strength of the cements was similar. These encouraging results suggest that the hydrothermal method is a potentially beneficial alternative to the sol–gel route for the production of calcium silicate powders. [ABSTRACT FROM AUTHOR]

A modified sol–gel method is proposed for the preparation of silicon carbide ultrafine powders. In this method, tetraethoxysilane (TEOS) and saccharose are used for preparing a binary carbonaceous silicon xerogel, and ferric nitrate is employed in the sol–gel process as a catalyst. The influence of processing parameters such as temperature of reaction and mass ratio of C to Si ( C / S i =0.5, 0.7, 1) on the synthesis of SiC particles were studied. After purification, the SiC sample was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectrum, Fourier transform infrared spectroscopy, differential thermal analysis (DTA) and thermo- gravimetric analysis (TGA). The results show that the SiC ultrafine particles were fully formed at reaction temperature of 1450 °C by employing the mass ratio of C / S i =1. This is confirmed by the obtained pattern from XRD and the Si–C absorption bands of SiC in the FTIR. [ABSTRACT FROM AUTHOR]

Silica/titania (SiO2/TiO2) (Si/Ti=1:1) composite aerogels have been manufactured via ambient pressure drying using tetraethoxysilane (TEOS) and tetrabutyl titanate (TBT) as precursors. Changes in the structure and the surface properties of the aerogels during the heat treatment were investigated in detail by N2 adsorption-desorption techniques, SEM, TEM, XRD, FTIR, and UV-vis absorption spectra. The results showed that the as obtained aerogel with a porous structure possessed a surface area of 667m²/g, average pore size 3.4nm, and pore volume 0.68cm³/g. After calcination, the surface area decreased while the average pore size and the pore volume increased with the rise of heat treatment temperature. FTIR spectra showed the existence of Si-O-Ti in the aerogels and that after calcination at 800°C, anatase nanoparticle appeared as demonstrated in XRD pattern. The photocatalytic performance was evaluated by degradation of MB and the results demonstrated that the aerogels calcined at 800°C have a better photocatalytic activity than other samples. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we report the interaction of chitosan with tetraethyl orthosilicate on the formation of silica nanoparticles under different conditions of pH (5–9) and chitosan concentration (0–0.001379mM). The silica nanoparticles were characterized by means of N2-sorption, scanning electron microscopy and transmission electron microscopy. It was found that chitosan played two different roles on the formation of silica nanoparticles, depending on the pH values. At a low chitosan concentration, chitosan promoted the formation of larger silica nanoparticles in the pH range of 5–6, while it reduced the size of silica nanoparticles when the pH value was increased to the range of 6.5–8.5. However, based on the results of N2-sorption analysis, two different sizes of silica nanoparticles caused by the growth of silica at different phases were observed. At high chitosan concentration, the size of silica nanoparticles continuously increased in the pH range of 5–6, while only smaller size of silica nanoparticles was obtained in the pH range of 6.5–8.5. At pH 9, chitosan molecules were found to have no significant effect on the formation of silica nanoparticles even though a large amount of chitosan was employed. [Copyright &y& Elsevier]

Abstract: In this study, a method for preventing the reaction between ceramic mold and stainless steel that occurs during the metal casting process has been introduced. The ceramic molds are produced using zircon ceramic powder with binders which are prepared with two different compositions, ethyl silicate [C8H20O4Si] and ethyl silicate/aluminum tri-sec-butoxide [Al(OCH(CH3)C2H5)3] solution. Hardness, porosity, sintering shrinkage, bulk density, surface morphology and chemical composition of the phases are examined. Stainless steel is poured into the ceramic mold and the mold–metal reaction behavior was examined in the cast product. Accordingly, burn-on casting defects encountered in stainless steel casting have exclusively been eliminated. [Copyright &y& Elsevier]

Sr 2 SiO 4 :0.01Eu 2+ (S 2 S:Eu 2+ ) nanopowders were prepared by a hybrid process, and the effects of different silicon sources (tetraethyl orthosilicate and colloidal SiO 2 ) and flux on the structure and luminescence were investigated. The phase ratio of β- to α′-S 2 S (R β/α′ ), the phase purity, and the particle morphology were strongly affected by the silicon sources and the flux. The synthesized powders mainly consisted of needle-shaped particles whose size depended on the preparation conditions. The photoluminescence (PL) spectra exhibited two emission bands at around 485 and 535 nm, which dominantly originated from the Eu(I) and Eu(II) sites, respectively. The addition of flux dramatically enhanced the PL intensities of the S 2 S:Eu 2+ powders by about 340–400% with the exception of the powder synthesized using colloidal SiO 2 with a concentration of 1.1 M. The PL intensity was closely correlated with R β/α′ , which significantly increased when flux was used. [ABSTRACT FROM AUTHOR]

Porous silica films as low- k interlayer dielectric were prepared via a sol–gel method. Tetraethoxysilane (TEOS) was used as raw material and polyvinyl alcohol (PVA) with different degrees of polymerization as molecular template. The precursor was deposited on to coated platinum silicon substrates and annealed at different temperatures. The films were modified with trimethylchlodrosilane (TMCS) for hydrophobicity, which can make the porous films present a stable characteristic of low k . The effects of annealing temperature and polymerization degree of PVA on mechanical properties were investigated. Significant improvement occurred for the sample annealed at 700 °C, the hardness and the Young modulus of the silica film templated by HPVA are 0.91 GPa and 15.37 GPa, respectively. These values are comparable with that of MOCVD low k silica sample. [ABSTRACT FROM AUTHOR]