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This paper presents the development of certain abrasives based on selected industrial wastes and gives an idea of their postuse behavior. These abrasives are manufactured using two methods: pulverization and coating. For these purposes, we used cellulosic nonwoven fibers as reinforcement, three types of resin (polyurethane, acrylic, and polyester) as a matrix, and abrasive grains of silicon carbide (SiC) and silica to obtain the abrasive character. We report the wear of the developed materials by abrasion, the evaluation of their roughness, the influence of the type of the abrasive grains, and their sizes on the wear performances. Scanning electron microscopy was performed to show the morphology of abrasives. The weight loss of abrasives was measured by thermogravimetric analysis and its derivative. Fourier‐transform infrared spectroscopy allows the chemical characterization and identification of abrasive grains. Under the same test conditions, experimental results indicate that silica‐based abrasives exhibit higher surface roughness and abrasion wear rate than SiC‐based abrasives. [ABSTRACT FROM AUTHOR]

The effects of using different ratios of silica fume on the mechanical and microstructural properties of hardened cement paste and concrete were investigated in this study. Portland cement was replaced with 5%, 10%, 15%, and 20% silica fume (SF) by weight. Microstructural properties of obtained samples were investigated by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The XRD analysis showed that the ratio of calcium hydroxide (CH), which is produced by hydration, decreases depending on the concrete age and the amount of silica fume. The SEM analysis showed that the use of silica fume decreases gaps and calcium silicate hydrate (C-S-H) which is also a hydration production. Silica fume content of up to 15% improved the observed mechanical and microstructural properties of concrete. At the optimum value of 15%, improvement in the paste was observed due to the filler effect and the reaction between the silica fume and calcium hydroxide, leading to a reduction in calcium hydroxide in the concrete. [ABSTRACT FROM AUTHOR]

Statement of the Problem: Despite yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) high strength in dental restoration application, Zr- the framework has a low tendency to react chemically with cement which is the main reason of these restoration failures. Purpose: The aim of this in vitro study was to evaluate the effect of Y-TZP coating by nanocomposite of silica and aluminosilicate according to the sol-gel dip-coating technique on the bond strength of resin cement to Y-TZP. Materials and Method: In this experimental study, Y-TZP blocks (10×10×3 ) were prepared and sintered and assigned into 4 groups (n=10) for coating including control group without any further surface treatment, sandblasted using 110 μm alumina particles under 2.5 bar and tip distance of 10 mm, silica sol dip coating + calcination, aluminosilicate sol dip coating+ calcinations. To confirm chemical bonds of sol-gel covers, Fourier transforms infrared spectroscopy (FT-IR) technique was used. The surface of the sample was investigated by scanning electron microscopy (SEM), energy-dispersive spectroscopy detector (EDS) and x-ray diffraction (XRD) methods. Micro-shear bond strengths (μSBS) of zirconia-cement specimens were evaluated. Data were analyzed with a one-way ANOVA test in SPSS version 11.5 software with a confidence interval of 95%. Results: μSBS of sandblasting, nano-silica, and nano-aluminosilicate specimens were significantly higher than control. μSBS of nano-silica was higher than other groups but no significant difference was observed in μSBS of sandblasting nano-silica, and nano-aluminosilicate groups (p> 0.05). Conclusion: Covering the zirconia surface with non-invasive nano-silica and nanoaluminosilicate using the sol-gel technique leads to improved cement bond strength. [ABSTRACT FROM AUTHOR]

Due to the strict requirements of concrete materials for bridge engineering, however, the congenital defects of ordinary concrete materials include low tensile strength, poor impermeability, and small tensile strain values, which seriously affect the application of concrete materials under some restrictive conditions, making the characteristics of high compressive strength unable to reflect, therefore, it is of great significance to develop concrete materials with good strength and low permeability. The purpose of this paper is to study the compressive strength, splitting tensile strength and microstructure of reinforced concrete in bridges, and analyze the reasons for the increase in strength. This paper takes the compensation shrinkage concrete as the basis, mixed steel fiber and nano-SiO2 to product the shrinkage nano-SiO2 reinforced concrete. And carry out the microstructure experiment the strength characteristic experiment. Finally, use the scanning electron microscope to analyzed hydration products and interface transition zones of compensated shrinkage nano-SiO2 reinforced concrete. The results show that the hydrated products of compensated shrinkage nano-SiO2 reinforced concrete with low degree of orientation and dense growth, The incorporation of nano-SiO2 promotes cement hydration, reduces porosity, and improves the mechanical strength and durability of concrete. When nano-SiO2 is not added, there is a micro-crack with a width of 5.35um between the steel fiber and the aggregate. After the incorporation of nano-SiO2, the micro-cracks is filled with hydrate, and the durability of the concrete is significantly improved. [ABSTRACT FROM AUTHOR]

Introduction: The aim of this study was to evaluate the effect of addition of nano-silica (SiO2) to mineral trioxide aggregate (MTA) on its setting time and porosity. Methods and Materials: The concentration 8% of nano-silica were prepared and added to the MTA powder. After mixing with water the setting time and porosity were evaluated and compared with pure MTA. Statistical analysis was performed using the t-test. The level of significance was set at 0.001. Results: The mean setting time of MTA+8% nano-silica (9.8±0.78) was significantly lower than MTA (23.3±2.16) (P<0.001). Also the mean porosity by imbibition method in MTA+8% nanosilica (23.49±0.48) was significantly higher than MTA (15.69±2.10) (P<0.001). There was no significant difference in mean porosity by scanning electron microscope (SEM) method in MTA+8% nano-silica (31.26±10.73) and MTA (32.74±5.26) (P>0.001). Conclusion: This in vitro study showed us an addition of 8% of nano-silica to MTA reduced the setting time. Although evaluation by imbibition test showed increasing of porosity in nano-silica MTA compared with pure MTA. [ABSTRACT FROM AUTHOR]

Abstract Saturation mechanisms are the cause considerable strength reduction and swelling enhancement in clayey soils. To overcome this phenomenon, stabilization of the weak layers could be useful when any chemical additives which are calcium based are added. In the presence of considerable amounts of sulfate ions, the conventional additive like lime leads to large heaving due to swelling. This paper presents the changes in the amount of California Bearing Ratio (CBR) of soaked samples and swelling index of Najmabad clayey soil after being stabilized with Colloidal Silica (CS). These tests were performed at different curing times of 3, 7, and 28 days. Moreover, CBR tests were performed after Freeze-Thaw (F-T) conditions under 1, 2, 4, 8, and 12 cycles in 3 selected samples which satisfied the required degree of improvement. In addition, free swelling in all the states was measured and controlled. The results revealed fulfilling CBR criterion of samples subjected to F-T cycles and significant reduction of swelling percent in samples with 1% Nano Silica (NS) particles after 28 days curing time and 2% NS particles after 7 days curing time. Also, Scanning Electron Microscopy (SEM) revealed structural changes and an integrated network for soil improved with CS. [ABSTRACT FROM AUTHOR]

Mesoporous silica particles and carbon black were selected as fillers for a resol-type phenolic resin, to be used as a matrix for ablative materials. Composites were processed with the modified polymer and carbon fibers were used as continuous reinforcement. The ablative properties of the materials obtained were studied by the oxyacetylene torch test and the ablated samples were observed by scanning electron microscopy. Composites with 30 wt. % of carbon black achieved the lowest linear erosion rate and the highest insulation index, denoting the ability of the char produced to protect the virgin material. Considering that such composite has 44% by volume of carbon fibers, it could be inferred that its properties could be improved by increasing the fiber content and maintaining the amount of carbon black. The composite with 20 wt. % of mesoporous silica particles exhibited the lowest mass erosion rate, indicating a better stabilization of the char. Regarding dynamic-mechanical properties, the addition of particles induced a decrease in the modulus and glass transition temperature of all the systems studied. [ABSTRACT FROM AUTHOR]

The blank of phase equilibrium relations, liquidus, and other information in the CaO-SiO 2 -La 2 O 3 basic slag system phase diagram limits the application of rare earth elements in the smelting, processing, and high temperature materials. In the current work, phase equilibrium relations in the CaO-SiO 2 -La 2 O 3 system at 1373 K–1873 K were studied experimentally by using thermodynamic equilibrium experiment followed by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy dispersive spectrometer (EDS). According to the experimental data, primary crystal field of SiO 2 , La 2 O 3 ·2SiO 2 , CaO·3SiO 2 ·2La 2 O 3 , and 2CaO·SiO 2 were identified respectively. The 1473 K–1873 K liquidus lines in SiO 2 primary crystal field and 1373 K–1873 K liquidus lines in CaO·3SiO 2 ·2La 2 O 3 primary crystal field were also determined. Sub-solidus phase fields in the ternary system were identified, and then the reaction type and temperature range of relevant invariant points were determined. Finally, the CaO-SiO 2 -La 2 O 3 ternary system phase diagram within specific region was obtained. [ABSTRACT FROM AUTHOR]

Nano/micro fluids have garnered the attention of material science and heat transfer fraternity across the world for the reported enhancement of their thermal properties and the amenability for a change of their rheological properties under external influence. Of the various nano/micro fluids that have been researched widely, micro-silica fluids comprise a predominant fraction. The alterations in the morphological characteristics of the micro-silica fluids brought about by mechanical treatment of the samples influence their chemical and rheological behaviours. The present work involves the study of milling parameters on the rheological behaviours of silica particles. The micron size silica is reduced to nano size by ball milling, done by 0-20 hours at 300 rpm in Fritsch P5 planetary ball mill. This milled powder will be characterized by XRD and SEM for it crystallite size and morphology. Thus prepared silica will be treated with ethylene glycol (EG) to enhance its dispersion in fluids. [ABSTRACT FROM AUTHOR]

A family of silicon (IV) compounds containingN,N'-symmetrically alkyl substituted 1,3-diketimine ligands as chemical vapor deposition (CVD) precursors for silicon-based films has been reported and characterized by1H,13C, and29Si NMR, EI-MS and elemental analysis where necessary. The compounds were synthesized by reaction of corresponding lithium salt of the diketimine ligands and SiMe3Cl according to a general procedure. Theoretical simulation was performed in order to understand their structures. Thermal stability, transport behavior and vapor pressures were evaluated by simultaneous thermal analyses (STA). Chemical vapor deposition was accomplished in a hot wall CVD reactor system to further demonstrate the ability of these compounds as CVD precursors. Characterization (SEM and XPS) of the as-grown films proved that the family indeed possesses the potential to fabricate silicon-based films with compact and uniform structure. [ABSTRACT FROM PUBLISHER]

Complex shaped nanoparticles featuring structural or surface chemical patchiness are of special interest in both fundamental and applied research areas. This study reports the preparation and optical properties of gold/silica 'mushroom' nanoparticles, where a gold particle is only partially covered by the silica cap. The synthetic approach allows precise control over the particle structure. The interfacial preparation method relies on partially embedding the gold particles in a polystyrene layer that masks the immersed part of the gold particle during silica shell growth from an aqueous solution. By adjusting sacrificial polystyrene film thickness and silica growth time, precise control over the coverage and cap thickness can be achieved. Correlative electron microscopy and single particle scattering spectroscopy measurements underline the high precision and reproducibility of the method. The good agreement between the measured and simulated single particle spectra supported by near-field calculations indicates that the observed changes in the dipolar plasmon resonance are influenced by the extent of coverage of the gold core by the silica cap. The straightforward methods readily available for gold and silica surface modification using range of different (bio)molecules make these well-defined nanoscale objects excellent candidates to study fundamental processes of programmed self-assembly or application as theranostic agents. [ABSTRACT FROM AUTHOR]

Puzzling aspects of the microporous structure of Stöber silica, including inconsistencies in the BET specific surface area and the long measurement time required for N2 adsorption, hinder further research on and potential applications of this material. In this work, Stöber silica samples prepared using systematic and detailed post-treatment methods were characterized by N2 adsorption, scanning electron microscopy, transmission electron microscopy, inductively coupled plasma optical emission spectrometry, elemental analysis, and Fourier transform infrared spectroscopy. We have found that the often overlooked sample preparation conditions may be the main causes that perplex the gas adsorption characterization results of Stöber silica samples. The pore-blocking processes associated with a variety of sample treatment methods are discussed in detail. Strong evidence for the particle growth model and pore-blocking mechanism involving ethoxyl groups, Si species, and condensation of silanols is provided. A remarkable result is that the measurement time is shortened from 1 month in our previous work to 2-3 days for samples with large specific surface areas. A suitable post-treatment condition is recommended to obtain microporous Stöber silica with a short measurement time, including water washing, low temperature drying without a vacuum, and a short storage time. [ABSTRACT FROM AUTHOR]

To evaluate the feasibility of the catalysts loaded onto the commercial cordierite monolith by a one-step loading method, the catalyst of V 2 O 5 -WO 3 /TiO 2 was loaded onto cordierite with the aid of acid pretreatment and silica sol addition. The results by SEM and N 2 adsorption showed that acid pretreatment of cordierite enlarged the BET surface area and pore volume of the catalysts significantly, enhancing both the SCR activity and mechanical stability. During the catalysts preparation, the introduction of silica sol demonstrated a significant improvement in the BET surface area and mechanical stability of the catalysts. The surface acidity of the catalysts increased with the increasing molar ratios of Si/Ti and decreased again, with the strongest surface acidity at Si/Ti molar ratio of 5/5. The XPS analysis showed that the incorporation of Si shifted the V valence from V 5 + to V 4 + and increased chemisorbed oxygen, which accelerated the SCR activity. The catalyst with cordierite acid pretreatment and Si/Ti molar ratio of 2/8 demonstrated to be an optimal catalyst, which showed a high NO conversion above 90% at 573–773 K, high mechanical stability, and resistance to sulfur and hydrothermal aging. [ABSTRACT FROM AUTHOR]

This study presents spatially controlled silica coating in poly(dimethylsiloxane) (PDMS) microchannels using the well-known sol-gel process. First, the corona discharge between two Pt electrodes inserted into the microchannels generated silanol groups at the desired location for further modifications. Next, the cross-linking of the silanol groups with silica sol produced a chemically bonded silica surface in the PDMS microchannels. After any remaining unreacted silica sol was removed from the channels with organic solvents, a spatially patterned glass-like surface was observed on the PDMS microchannels. The introduced hydrophilicity and chemical stability of the silica coated PDMS was characterized with various analytical techniques including contact angle analysis, charge-coupled device (CCD) imaging, scanning electron microscopy (SEM), electro-osmotic flow (EOF) mobility measurement, neutral dye BODIPY/organic solvents absorption test and capillary gel electrophoresis. The water contact angle of the silica coated PDMS decreased, and the absorption of BODIPY was substantially suppressed in the silica coated PDMS microchannels while the native ones exhibited an increased fluorescent background signal within 10 min after BODIPY injection. The EOF of the silica coated surface was one order of magnitude higher than the ones with the native PDMS surface for a wide range of pHs. Polyacrylamide gel was immobilized in the silica coated PDMS microchannels, and a DNA ladder was successfully separated in the microchannel. PDMS microfluidic devices with enhanced wettability and stability can be used in multistep chemical syntheses and in various bio- and medical technologies. [ABSTRACT FROM AUTHOR]

Materials based on tungstophosphoric acid supported on core-shell polystyrene-silica microspheres or hollow silica spheres were prepared, characterized and used as catalysts in the synthesis of trisubstituted imidazoles by a multicomponent reaction under solvent-free conditions. For the preparation of the two different silica-based structures, silica was synthesized using tetraethylorthosilicate (TEOS) as precursor in an ethanol-ammonium solution and polystyrene spheres as template or core. The formation and growth of the silica layer to obtain the core-shell microspheres were followed by 24 h. Then, the hollow spheres were obtained by calcination of the core-shell material at 500 °C for 3 h. Both supports were impregnated with tungstophosphoric acid (TPA) solutions. A smooth appearance of the spheres was observed by scanning electron microscopy (SEM). Mesoporous materials were obtained, without important microporosity, as determined from N 2 adsorption-desorption isotherms. The Fourier transform infrared (FT-IR) spectra confirmed that complete removal of the polystyrene core can directly be achieved by calcination at 500 °C, and also that Keggin undegraded TPA species are present in the impregnated solids. The acidic characteristics of the solids were evaluated by potentiometric titration, showing that they exhibit very strong acid sites. Moreover, peaks assigned to crystalline forms of TPA were observed by XRD. The yields obtained in the solvent-free synthesis of 2,4,5-triphenyl-1 H -imidazole and other eight trisubstituted imidazoles were high, without formation of by-products resulting from competitive reactions or decomposition products, so the prepared materials are highly selective catalysts. [ABSTRACT FROM AUTHOR]

Indian low grade iron ores mostly contain quartz, gibbsite, and clay as the major impurities. Depending upon the ore characteristics, in many instances froth flotation has to be used to recover the hematite and other iron oxides from the ground ores. In this context, the difference in silica and alumina content in low grade iron ores is brought to bear on the prospects of iron ore flotation. For this purpose, pure minerals like hematite, quartz, gibbsite, and clay have been used to prepare synthetic mixtures and analyzed to determine the difference in floatability. The results are compared against natural iron ores with variations in silica and alumina content. The flotation results with oleic acid and dodecylamine show better recovery of iron values in the hematite–quartz mixture as well as in the naturally occurring high silica ore compared to the hematite–clay mixture and the high alumina ore respectively. Similarly results on a variety of iron ores show that high silica content as quartz in the ore causes less hindrance in the flotation of iron ore, whereas the presence of silica as clay inhibits the flotation response of iron ore. The scanning electron microscopic (SEM) studies indicate that clay particles cover the surface of hematite, making it less selective for interaction with the collector. The surface potential studies of clay and quartz suggest that charge reversal takes place for quartz treated with dodecylamine (DDA), but for the DDA adsorption on clay, negative potential values are noted beyond a pH of 4.6. [ABSTRACT FROM AUTHOR]

Objective: To underline peculiar composition of kidney stones and to propose an epidemiologic study of urinary stones in West African countries, where epidemiologic studies are scarce. Only few data are available regarding stone composition in sub-Saharan countries. Recently, a set of 100 stones consecutively removed by surgery in the Department of Urology of the University Hospital of Ouagadougou in Burkina Faso were collected for physical analysis, which provided the opportunity to obtain an epidemiologic profile of stone composition in this country.Materials and Methods: A total of 100 stones from 64 men, 22 women, 10 boys, and four girls were analyzed by morphologic examination, infrared spectroscopy, and electron microscopy in our laboratory. The results were considered by sex and separately for adults and children.Results: Sixty-five percent of the 100 stones contained calcium oxalate as the main component. Interestingly, the second main component was opaline silica (18%). Furthermore, opaline silica was identified in any proportion in 48% of the stones. The prevalence was sex and age dependent. Opaline silica was detected as the main component in 42% of the nuclei, which underlines its role as one of the main components involved in the initiation of calculi in this country.Conclusion: For the first time, a dramatically high occurrence of a "scarce" urinary stone component, namely opaline silica, was reported in a series of consecutive calculi from a single country. We propose that a regular consumption of clay could be the origin of this phenomenon in these populations. [ABSTRACT FROM AUTHOR]

In the present work, an organic–inorganic hybrid composite (poly(allylamine)/silica) was facilely prepared through grafting poly(allylamine) onto the modified silica. Surface property, morphology, and texture parameters of the composite were characterized by infrared spectroscopy (FTIR), scanning electron microscopy, andN2adsorption/desorption measurements, respectively. Then, the adsorptive property of this composite for recovery of Ce(III) was investigated systematically. Batch tests were performed under a range of conditions to examine the effects of contact time, adsorbent amount, initial Ce(III) concentration, and solution pH. At optimal experimental conditions, the maximum adsorption capacity of Ce(III) was up to 111.8 mg g−1. Full kinetic and thermodynamic investigations as well as isotherm analysis were also undertaken. It was found that the adsorption kinetics could be well fitted by the pseudo-second-order model, whereas the Freundlich model provided the better description for the equilibrium data. The adsorption process was spontaneous and endothermic with an increase of randomness at the solid–solution interface during adsorption. Moreover, the reusability of poly(allylamine)/silica composite was evaluated, and the result showed that the composite could be well reused in several cycles without significant deterioration in its original performances. [ABSTRACT FROM AUTHOR]

LaF 3 :Ce,Tb@SiO 2 core-shell nanostructures were synthesized using a new one-pot reverse microemulsion strategy. One-pot method facilitates the synthetic process of this kind of core-shell nanostructures. The crystalline phase, size, morphology, pore structure and luminescence properties were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen physisorption isotherm, photoluminescence (PL) excitation and emission spectra. The results revealed that the core-shell nanostructures have an average diameter of about 27 nm and cores of about 3 nm, and that these nanostructures contain micropores with an average pore diameter of 0.43 nm. The characteristic emissions of Tb 3+ were observed under the excitation of Ce 3+ 4f–5d transition due to the energy transfer from Ce 3+ to Tb 3+ . LaF 3 :Ce,Tb@SiO 2 nanostructures can disperse well in water and the colloid can emit bright green light under ultraviolet (UV) irradiation. [ABSTRACT FROM AUTHOR]

Hybrid-silica materials containing octyl, phenyl and urea-propyl functional groups were reported. These functionalized silicas were prepared by a via one-pot synthesis method through co-condensation of tetraethyl ortosilicate with organosilanes co-precursors. The obtained materials were analyzed by a number of techniques including scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction pattern and nitrogen sorption measurement. The main elements: morphology and surface properties of the final products that are basically dependent on the type and the quantity of functional-containing groups were fully discussed. The adsorption properties of the modified silicas were investigated against bilirubin in aqueous solution at pH 7.4, the effect of time was studied as well. The modified silicas showed a greatly increasing of adsorption capacity for bilirubin compared to pure amorphous silica. The results indicate that the type of functional-containing groups and surface properties affect the adsorption behavior. These materials show a potential application as effective adsorbents for bilirubin removal. [ABSTRACT FROM AUTHOR]

Geopolymer is the refractory inorganic ps formed from both aluminum and silicon source. South Korean rice husk ash (RHA) has been investigated as an alternative silica source to replace fume silica currently used in geopolymer rdfdffdfdesearch. In order to acquire proper RHA from raw rice husk, the optimal calcination temperature, which produces the highest amount of amorphous silica, was studied. Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS) and X-ray diffraction (XRD) have been used to verify the contents of RHA. Previously many researchers have studied mixtures of RHA/fly ash (FA) or RHA/red mud (RM), resulting the ratio of SiO2/Al2O3 varied by the each mixture. However, in this paper, RHA is only replaced to a certain portion of fumed silica. Thus, the fundamental ratio of each ingredient in the geopolymer (M: SiO2 : AlO2 : H2O = 1 : 1 : 4 : 11) where M is Na, K or Cs was strictly kept. Five variations of RHA/Fumed silica mixture (0/100, 25/75, 50/50, 75/25, 100/0) have been studied. Each mixture was dissolved with potassium hydroxide (KOH) and deionized water for 24 hours on the stirring plate and then became water glass. Metakaolin was added to water glass and mixed properly. The geopolymer slurry was poured into the mold and cured at 50oC for 24 hours. After demolding, the RHA geopolymer samples were kept for a minimum of 3 days at the room temperature. The flexural stress of RHA geopolymer samples were investigated by 3-point bend tests at room temperature using the guidelines prescribed by ASTM C78/C78-M standard. The fracture surfaces from the bending tests were examined by using Scanning Electron Microscope (SEM). It was demonstrated that the RHA can clearly be the fumed-silica alternative. [ABSTRACT FROM AUTHOR]

Janus particles are objects with two distinct domains of different surface chemistries that give them an amphiphilic character. The coexistence of hydrophilic and hydrophobic domains makes them suitable models for biological objects (e.g., proteins) and enables their use as 'particle surfactants'. Since the time of their initial discovery, numerous strategies have been proposed for the realisation of Janus particles with variable and controlled size/functionality of the two surface domains. Owing to experimental limitations though, it has been rarely possible to ascertain and characterise the amphiphilic nature of the particles. We present here new results on the synthesis of spherical Janus microparticles with controlled surface chemistries and Janus ratios and on the measurement of their contact angle in situ at an oil-water interface, using freeze-fracture, shadow-casting cryo-scanning electron microscopy. [ABSTRACT FROM AUTHOR]

1,4-Bis(trimethoxysilyl)benzene and 1,4-bis((trimethoxysilyl)-phenyl)-dimethoxysilane were synthesized from their corresponding diarylbromides. These bis(trimethoxysilyl)arenes were used as organosilica precursors for the preparation of macro-/mesoporous silica monoliths, using poly(ethylen glycol) as a porogen to obtain a well-defined bicontinuous macroporosity and mesoporosity. The porosity of the prepared materials was characterized by nitrogen sorption measurements, mercury intrusion and scanning electron microscopy. The incorporation of silylarenes was studied by solid-state 13C NMR spectroscopy, IR spectroscopy and elemental analysis. [ABSTRACT FROM AUTHOR]

Considering ongoing global deforestation and the increased demand for raw materials in all wood-processing sectors it is necessary to seek and employ alternative resources. Agricultural residues are potential sources of alternative lignocellulose-based raw materials. Research on substitute materials for wood panel production mainly focused on physical and mechanical properties of boards while much remains to be learned about machining. Therefore, studies were carried out to analyse the relationship between ash and silica content and their impact on tool wear. Ash and silica contents of agricultural residues were determined following ISO 3340. Particle morphology and elemental composition of selected materials were analysed using scanning electron microscopy and energy-dispersive X-ray analysis. Tool wear tests were carried out using particleboards made from wheat straw, canola straw and spruce. Analyses of various plant materials displayed no correlation between ash and silica content. Bio-mineralised silica structures in wheat and canola were different compared to coarse silica found in wood-based particleboard. Tool wear caused by these agricultural residues was just moderately increased compared to wood, despite the fact that their silica contents were many times higher. Furthermore, the impact of abrasive substances on wear behaviour was influenced by the density of the panels. [ABSTRACT FROM AUTHOR]

Background and objective China's Xuan Wei County in Yunnan Province have the world's highest incidence of lung cancer in nonsmoking women-20 times higher than the rest of China. Previous studies showed, this high lung cancer incidence may be associated with the silica particles embedded in the production combustion from the C1 coal. The aim of this study is to separate the silica particles from production combustion from the C1 bituminous coal in Xuan Wei County of Yunnan Province, and study in vitro toxicity of naturally occurring silica particles on BEAS-2B. Methods 1.Separating the silica particles from combustion products of C1 bituminous coal by physical method, observing the morphology by Scanning Electron Microscope, analysis elements by SEM-EDX, observed the single particle morphology by Transmission Electron Microscope, analyzed its particle size distribution by Laser particle size analyzer, the surface area of silica particles were determined by BET nitrogen adsorption analysis; 2. Cell viability of the experimental group(silica; naturally occurring), control group (silica; industrial produced and crystalline silica) was detected by assay used the3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method, and the reactive oxygen species (ROS),lactate dehydrogenase (LDH) were determined after 24 h-72 h exposed to these particles. Results 1. The physical method can separate silica particles from production combustion from the C1 bituminous coal, which have different size, and from 30 nm to 120 nm particles accounted for 86.8%, different morphology, irregular surface area and containing trace of aluminum, calcium and iron and other elements; 2.Under the same concentration, the experiment group have higher toxicity on BEAS-2B than control groups. Conclusion 1.Physical method can separate silica particles from production combustion from the C1 bituminous coal and not change the original morphology and containing trace; 2.Naturally occurring silica nanoparticles have irregular morphology, surface area, and containing complex trace elements may has greater toxicity than the silica nanoparticle of industrial produced and crystalline silica. [ABSTRACT FROM AUTHOR]

Mechanical properties of epoxy resin toughened with two different submicron particles of TiO at different weight fractions (1, 3, and 5%, respectively) were investigated. The first TiO particles are surface treated with AlO-SiO, and the second are surface treated with AlO-ZrO. The composites were characterized by tensile, flexural, pull off and abrasion tests, followed by X-ray photoelectron spectroscopy and scanning electron spectroscopy of the fracture surfaces. A small amount of TiO (~1%) submicron particles improves the flexural, abrasion and pull-off strengths, while amounts up to 5% significantly enhance tensile properties only. TiO particles surface treated with AlO-ZrO produce an epoxy composite with higher strength and weight loss but lower pull off strength and more brittle than that prepared with AlO-SiO particles. The TiO particles surface treated with AlO-SiO have a higher adherence to the epoxy composite matrix than the particles treated with AlO-ZrO as shown by scanning electron spectroscopy. [ABSTRACT FROM AUTHOR]

Complex concretions in the Jurassic Morrison Formation in New Mexico, USA, were studied to elucidate their enigmatic origin. The concretions, mostly in the 0.1–2 m height range, are characterized by a microcrystalline quartz matrix and many tiny (4–8 mm diameter) cylindrical protrusions. A common architecture revealed by weathering is a vertical, cylindrical concentric casing around a homogenous core. Concretion morphologies include irregular bodies and larger horizontal cylinders with surficial protrusions. Sometimes cores and/or protrusions are absent. Micromorphological data and open grain packing indicate concretions formed in unconsolidated sediments. Light and scanning electron microscopy shows gradational contacts between the siliceous concretions and host sandstones. Point counts of concretions and host rock show more cement and intergranular volume in the concretions, but fewer grains and primary pores. Most concretions are cemented by microporous, microcrystalline quartz, chlorite, kaolinite, and illite-smectite. X-ray fluorescence and instrumental neutron activation analyses indicate that silica was added to form the concretions. Previous models for the concretions include burrows, termite nests and rhizocretion. However, these interpretations are challenged by geochemical, macromorphological and micromorphological data presented in this study. Infiltration, possibly due to hydrothermal activity, may have added silica, but explanations for several morphological details remain elusive. These data imply that inorganic diagenetic factors can be important in ichnological interpretations. • Silicification is a leading factor in the formation of complex concretions. • Major differences in chemical composition of concretions and host rocks • Gradational contacts of concretion margins suggest limited diffusion. • Concretions were formed in unconsolidated sediments. • Proposed biological proxies are problematic. [ABSTRACT FROM AUTHOR]

Cover Photograph: Novel micro‐spherical Si3N4 nanowire sponges are synthesized employing carbon‐doped silica sol foams with uniform pore distribution and ultrathin wall structure as the reverse templates. Top‐left: SEM image of micro‐spherical Si3N4 nanowire sponges. Top‐middle: SEM image of individual Si3N4 nanowire‐weaving microsphere. Top‐right: SEM image of the Si3N4 nanowires from the marked section in the single Si3N4 nanowire‐weaving microsphere. Bottom‐left: High‐magnification SEM image of the Si3N4 nanowires. Bottom‐middle: TEM image of several Si3N4 nanowires from the sponges. Bottom‐right: HRTEM image of the marked section in an individual Si3N4 nanowire. Image Credits: Xiaoyan Zhang, Wenlong Huo, Yugu Chen, and Ke Gan. DOI: 10.1111/jace.16167. Cover Photograph: Novel micro‐spherical Si3N4 nanowire sponges are synthesized employing carbon‐doped silica sol foams with uniform pore distribution and ultrathin wall structure as the reverse templates. Top‐left: SEM image of micro‐spherical Si3N4 nanowire sponges. Top‐middle: SEM image of individual Si3N4 nanowire‐weaving microsphere. Top‐right: SEM image of the Si3N4 nanowires from the marked section in the single Si3N4 nanowire‐weaving microsphere. Bottom‐left: High‐magnification SEM image of the Si3N4 nanowires. Bottom‐middle: TEM image of several Si3N4 nanowires from the sponges. Bottom‐right: HRTEM image of the marked section in an individual Si3N4 nanowire. Image Credits: Xiaoyan Zhang, Wenlong Huo, Yugu Chen, and Ke Gan. DOI: 10.1111/jace.16167. [ABSTRACT FROM AUTHOR]

Production of Portland cement requires a large volume of natural raw materials and releases huge amounts of CO2 to the atmosphere. Lower environmental impact alternatives focus on alkali-activated cements. In this paper, fluid catalytic cracking residue (FCC) was used to partially replace (0 wt %–50 wt %) ceramic sanitaryware (CSW) in alkali-activated systems. Samples were activated with NaOH and sodium silicate solutions and were cured at 65 °C for 7 days and at 20 °C for 28 and 90 days. In order to increase CSW/FCC binders’ sustainability, the influence of reducing the silica concentration (from 7.28 mol·kg−1 up to 2.91 mol·kg−1) was analyzed. The microstructure of the developed binders was investigated in pastes by X-ray diffraction, thermo tests and field emission scanning electron microscopy analyses. Compressive strength evolution was assessed in mortars. The results showed a synergetic effect of the CSW/FCC combinations so that, under the studied conditions, mechanical properties significantly improved when combining both waste materials (up to 70 MPa were achieved in the mortars containing 50 wt % FCC cured at room temperature for 90 days). Addition of FCC allowed CSW to be activated at room temperature, which significantly broadens the field of applications of alkali-activated CSW binders. [ABSTRACT FROM AUTHOR]