超细CeO2的微波辅助加热合成及其抛光性能

引言铈基抛光粉因具有发削能力强,抛光时间短、抛光精度高、操作环境清洁、比其他抛光粉的使用效果佳等优点,被人们称为抛光粉之王".     

Preparation and photoluminescence property of a loose powder, Ca3Al2O6:Eu by calcination of a layered double hydroxide precursor

A novel red light-emitting material, Ca₃Al₂O₆:Eu³⁺, which is the first example found in the Ca₃Al₂O₆ host, was prepared by calcination of a layered double hydroxide precursor at 1350 °C. The precursor, [Ca_2.9−xAl₂Eu_x(OH)_9.8](NO₃)_2+x·2.5H₂O, was prepared by coprecipitation of metal nitrates with sodium hydroxide. The material is a loose powder composed of irregular particles formed from aggregation of particles of a few nanometers, as shown in scanning electron microscope (SEM) images. It was found that the photoluminescence intensity reached the maximum when the calcination temperature was 1350 °C and the concentration of Eu³⁺ was 1.0%. The material emits bright red emission at 614 nm under a radiation of λ=250 nm.     

Preparation and formation mechanism of three-dimensionally ordered macroporous (3DOM) MgO, MgSO4, CaCO3, and SrCO3, and photonic stop band properties of 3DOM CaCO3

Three-dimensionally ordered macroporous (3DOM) magnesium (Mg) oxide (MgO), MgSO₄, calcium (Ca) carbonate (CaCO₃), and strontium (Sr) carbonate (SrCO₃) were prepared using a colloidal crystal of polymer spheres as a template. Ethanol or ethanol-water solution of metal salts (acetate or nitrate) and citric acid was infiltrated into the void of the colloidal crystal template of a monodispersed poly(methyl methacrylate) (PMMA) sphere. Heating of this PMMA-metal salt-citric acid composite produced the desired well-ordered 3DOM materials with a high pore fraction, which was confirmed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet-visible (UV-vis) diffuse reflectance spectra. The presence of citric acid is crucial for production of the 3DOM structures. Reaction of citric acid with metal salt produces metal citrate solid in the void of PMMA spheres, which is necessary to maintain the 3DOM structure during the calcination process. 3DOM CaCO₃ shows opalescent colors because of it's photonic stop band properties.     

Solid-state Al and Si NMR characterization of hydrates formed in calcium aluminate-silica fume mixtures

Partially deuterated Ca₃Al₂(SiO₄)_y(OH)_12−4y-Al(OH)₃ mixtures, prepared by hydration of Ca₃Al₂O₆ (C₃A), Ca₁₂Al₁₄O₃₃ (C₁₂A₇) and CaAl₂O₄ (CA) phases in the presence of silica fume, have been characterized by ²⁹Si and ²⁷Al magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopies. NMR spectroscopy was used to characterize anhydrous and fully hydrated samples. In hydrated compounds, Ca₃Al₂(OH)₁₂ and Al(OH)₃ phases were detected. From the quantitative analysis of ²⁷Al NMR signals, the Al(OH)₃/Ca₃Al₂(OH)₁₂ ratio was deduced. The incorporation of Si into the katoite structure, Ca₃Al₂(SiO₄)_3−x(OH)_4x, was followed by ²⁷Al and ²⁹Si NMR spectroscopies. Si/OH ratios were determined from the quantitative analysis of ²⁷Al MAS-NMR components associated with Al(OH)₆ and Al(OSi)(OH)₅ environments. The ²⁹Si NMR spectroscopy was also used to quantify the unreacted silica and amorphous calcium aluminosilicate hydrates formed, C-S-H and C-A-S-H for short. From ²⁹Si NMR spectra, the amount of Si incorporated into different phases was estimated. Si and Al concentrations, deduced by NMR, transmission electron microscopy, energy dispersive spectrometry, and Rietveld analysis of both X-ray and neutron data, indicate that only a part of available Si is incorporated in katoite structures.     

Photocrosslinking of EVA/inorganic filler blends and characteristics of related properties

The blends of EVA filled with talc, calcium carbonate, and glass ball (GB) have been photocrosslinked by UV irradiation in the presence of benzophenone (BP) as a photoinitiator and triallyl isocyanurate (TAIC) as a crosslinker. The various factors affecting the crosslinking process and the related properties have been studied by gel determination, heat extension test, mechanical and thermal aging test, UV spectroscopy, and scanning electron microscopy. The results show that the EVA/talc, EVA/CaCO₃, and EVA/GB samples of 1 mm thickness filled with 25 phr inorganic filler can be photocrosslinked to gel content of above 70 wt% by 5 sec UV‐irradiation under optimum conditions, which is sufficient for some applications of EVA blend materials. The crosslinking rate and final gel content level are in the order of EVA/GB > EVA/talc > EVA/CaCO₃. The data from mechanical and thermal aging tests give evidence that the photocrosslinked EVA/talc, EVA/CaCO₃, and EVA/GB samples are of much better tensile strength and thermal aging properties than those of the unphotocrosslinked ones. Copyright © 2009 John Wiley & Sons, Ltd.     

Anchoring calcium carbonate on graphene oxide reinforced with anticorrosive properties of composite epoxy coatings

Calcium carbonate nanoparticles (nano‐CaCO₃) anchored graphene oxide (GO) sheet nanohybrids (GO‐CaCO₃) are fabricated, and their structure can be measured by scanning electron microscope, transmission electron microscopy, X‐ray photoelectron spectroscopy, X‐ray diffraction and Fourier‐transform infrared spectroscopy analysis. Afterwards, composite epoxy coatings, filled with GO and GO‐CaCO₃ nanohybrids, are prepared via a curing process. The dispersion and anticorrosive properties of composite epoxy coatings are investigated. The results reveal that GO‐CaCO₃ nanohybrids achieve a homogeneous dispersion as well as reinforce corrosion resistance of epoxy coatings. Furthermore, the anticorrosive mechanisms are tentatively proposed for the GO‐CaCO₃/epoxy coatings. Copyright © 2016 John Wiley & Sons, Ltd.     

Study of Zircon-Dolomite Reactions Monitored by Neutron Thermodiffractometry

The reaction mechanism that takes place in ZrSiO₄-Mg Ca(CO₃)₂ mixtures was studied in air up to 1300°C by collecting neutron diffraction patterns during the heating ramp. Neutron diffraction intensities were used to monitor and establish the mechanism of reaction that occurs in successive stages. (a) MgCa(CO₃)₂ decomposition yielding MgO and CaCO₃; (b) CaCO₃ decomposition; (c) reactions between CaO, MgO, and ZrSiO₄ involving the formation of phases such as: tetragonal-ZrO₂, α-Ca₂SiO₄, and Ca₃MgSi₂O₈, some of them acting as transitory phases; and (d) formation of CaZrO₃. The results obtained by this technique agree with data obtained by differential thermal analysis and thermogravimetry. The final product has a porous structure, due to the release of CO₂, with a very narrow pore size distribution (≈1 μm). This open-porosity can be controlled by tailoring the reaction sintering process.     

Peanut-shaped aggregation of CaCO<Subscript>3</Subscript> crystallites in the presence of an amphiphilic derivative of carboxymethylchitosan

An amphiphilic derivative of carboxymethylchitosan (CMCS), (2-hydroxyl-3-butoxyl)propyl-CMCS (HBP-CMCS), was used as an organic additive in the precipitation process of calcium carbonate (CaCO₃). HBP-CMCS molecules can interact with calcium ions, the functional groups of which act as active sites for the nucleation and crystallization of CaCO₃. Simultaneously, HBP-CMCS molecule also functionalizes as a colloidal stabilizer to prohibit the sedimentation of the grown CaCO₃ crystals, depending upon the molar ratio of the initial Ca²⁺ ions to the repeat units of HBP-CMCS molecules. The combination investigations of scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy on the precipitated CaCO₃ crystals proved that concentrations of HBP-CMCS and Ca²⁺ exert great influence on the crystallization habit of CaCO₃, such as the nucleation, growth, morphology, crystal form, etc. The formation of the peanut-shaped CaCO₃ particles suggests the template effect of HBP-CMCS molecules on the aggregation behavior of CaCO₃ nanocrystals.     

Preparation and reactivity of polyfunctional six- and eight-membered cyclic silicates

Six- and eight-membered cyclic silicates with reactive SiH or Si-vinyl functional groups have been prepared: hexakis(dimethylsiloxy)cyclotrisiloxane (I), hexakis(vinyldimethylsiloxy)cyclotrisiloxane (II), octakis(dimethylsiloxy)cyclotetrasiloxane (III) and octakis(vinyldimethylsiloxy)cyclotetrasiloxane (IV). Reaction of pseudo wollastonite (Ca₃Si₃O₉) with dimethylchlorosilane or vinyldimethylchlorosilane gives I and II, respectively. IV has been prepared similarly by reaction of octakis[chloro calcium oxy]cyclotetrasilicate [Ca₈Si₄O₁₂Cl₈] with vinyldimethylchlorosilane. On the other hand, acid catalyzed siloxane exchange between tetramethyldisiloxane and octakis(trimethylsiloxy)cyclotetrasiloxane (V) gave III. Cyclic silicates (I-VI) are surprisingly resistant to acid catalyzed ring opening polymerization. In addition, II, IV, V and hexakis(trimethylsiloxy)cyclotrisiloxanes (VI) are resistant to phosphazene P₄-t-Bu superbase catalyzed ring opening polymerization.     

Design and synthesis of optically transparent calcium‐incorporated polymer complexes

Transparent thin films of calcium‐ion‐incorporated polymer composites were synthesized with calcium carbonate (CaCO₃) and polymers such as poly(acrylic acid) (PAA), poly(ethylene glycol) (PEG), and methylcellulose. The homogeneous distribution of Ca²⁺ in the composite films was observed because of the high concentration of COO^? groups along the PAA backbone for the complexation of Ca²⁺ ions. The optical transparency of the composites depends on the weight percentages of the three polymers and the molar concentration of CaCO₃ in the composites. Maximum transparency was obtained for a composite film with a PAA/CaCO₃ ratio of 9:1. The results indicated that methylcellulose improved the film‐forming capabilities and that PEG improved the transparency of the composites. All polymer complexes were characterized with X‐ray diffraction, fourier transfer infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, dynamic mechanical analysis, and optical transparency measurements. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4459–4465, 2004     

Novel CaCO3/g-C3N4 composites with enhanced charge separation and photocatalytic activity

A novel CaCO₃/graphitic carbon nitride (g-C₃N₄) photocatalyst was synthesized for the first time via a facile calcination method using CaCO₃ and melamine as precursors. The as-prepared samples were characterized using various techniques, such as scanning and transmission electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller analysis, as well as Fourier-transform infrared, X-ray photoelectron, photoluminescence, and UV–vis diffuse reflectance spectroscopy. The results of the experiments confirm the successful coupling of CaCO₃ to g-C₃N₄. The photocatalytic activity of the synthesized CaCO₃/g-C₃N₄ composites was evaluated by assessing their performance in the photocatalytic degradation of crystal violet (CV) in water under visible light irradiation. The analysis shows that CaCO₃/g-C₃N₄ exhibits higher photocatalytic activity towards CV degradation (76.0%) than pristine g-C₃N₄ (21.6%) and CaCO₃ (23.2%). Radical trapping and electron spin resonance experiments show that hydroxyl radicals (OH) and holes (h⁺) are the key reactive species in the photocatalytic process. The enhanced photocatalytic activity of the composite is mainly attributed to the efficient separation rate of electron-hole pairs achieved through the incorporation of CaCO₃.     

Role of Na-Montmorillonite on Microbially Induced Calcium Carbonate Precipitation

The use of additives has generated significant attention due to their extensive application in the microbially induced calcium carbonate precipitation (MICP) process. This study aims to discuss the effects of Na-montmorillonite (Na-MMT) on CaCO₃ crystallization and sandy soil consolidation through the MICP process. Compared with the traditional MICP method, a larger amount of CaCO₃ precipitate was obtained. Moreover, the reaction of Ca²⁺ ions was accelerated, and bacteria were absorbed by a small amount of Na-MMT. Meanwhile, an increase in the total cementing solution (TCS) was not conducive to the previous reaction. This problem was solved by conducting the reaction with Na-MMT. The polymorphs and morphologies of the CaCO₃ precipitates were tested by using X-ray diffraction and scanning electron microscopy. Further, when Na-MMT was used, the morphology of CaCO₃ changed from an individual precipitate to agglomerations of the precipitate. Compared to the experiments without Na-MMT in the MICP process, the addition of Na-MMT significantly reduced the hydraulic conductivity (HC) of sandy soil consolidated.     

镁热还原气相法白炭黑制备纳米硅及其电化学性能

以气相法白炭黑(FS)为Si前驱体,通过镁热还原工艺和对获得的NPs-Si进行SiOx和C复合包覆,制备出NPs-Si@SiOx@C纳米复合结构,将其用作锂电池负极进行电化学性能测试。研究结果表明:镁热还原过程分两步进行,即SiO_2与Mg先生成Mg2Si中间相,Mg2Si继续与SiO_2反应生成Si的反应路径;根据此规律镁热还原气相法白炭黑的Si转化率达87.9%。电化学性能测试中NPs-Si@SiOx@C负极在2.0 A·g-1的电流密度下有1 300 mAh·g-1的容量平台,1 000次循环后的放电比容量为964.2mAh·g-1,容量保持率达75%。     

Mid-infrared spectroscopic study of crystallization of cubic spinel phase from metakaolin

The structural changes during thermal conversion of metakaolinite into cubic spinel phase that was in literature considered as Al–Si spinel or γ-Al₂O₃ were investigated by mid-infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) using medium ordered kaolin with high content of kaolinite. Spectrum features were studied in the mid-infrared region from 4000 to 400 cm⁻¹ as function of fractional conversion that resulted from DSC experiments. The increasing contends of Al–O bonds in the octahedral position (AlO₆) was observed during thermal transformation. The high ratio of antisymmetric stretching of Si–O–Al and Si–O–Si bands and bands belonging to stretching of Al–O bonds in the (AlO₄) tetrahedra and (AlO₆) octahedra decreases exponentially with fractional conversion. The antisymmetric stretching band of Si–O–Si bond in the (SiO₄) tetrahedra becomes more expressive due to formation of amorphous SiO₂ phase.     

The synthesis mechanism of Ca3Al2O6 from soft mechanochemically activated precursors studied by time-resolved neutron diffraction up to 1000°C

The reaction pathway for the Ca₃Al₂O₆ formation up to 1300°C, from mechanochemically treated mixtures of amorphous aluminum hydroxide and CaCO₃, was studied in situ by differential thermal analysis, constant heating rate dilatometry and time-resolved neutron powder diffraction. The experiment was carried out, in an open system, on a sample with the nominal Ca₃Al₂O₆ stoichiometry. The results obtained by neutron diffractometry and thermal analysis were in good agreement with the data obtained by scanning electron microscopy and X-ray diffraction on heat-treated and-quenched samples. The synthesis path implied the formation of cryptocrystalline Al₂O₃, crystalline CaO, CaAl₂O₄ and Ca₁₂Al₁₄O₃₃ as transitory phases. Finally the nucleation and growth of the single phase Ca₃Al₂O₆ took place at 1300°C and exhibited porous structure due to CO₂ and H₂O release.     

Synthesis,characterization, and catalytic application of Fe3O4‐Si‐[CH2]3‐N=CH‐aryl for the efficient synthesis of novel poly‐substituted pyridines

Fe₃O₄ magnetic nanoparticles (MNPs) were functionalized by aminopropylsilane and reacted with aromatic aldehyde, and Fe₃O₄‐Si‐[CH₂]₃‐N=CH‐Aryl and Fe₃O₄‐Si‐(CH₂)₃‐NH‐CH₂‐Aryl MNPs were prepared as novel magnetic nanocatalysts. Fourier transform infrared (FT‐IR), X‐ray diffraction (XRD), and scanning and transmission electron microscopy (SEM and TEM) were used to identify the MNPs. The catalytic activity of the MNPs was evaluated in the one‐pot synthesis of some novel poly‐substituted pyridine derivatives.     

Characterization of sol-gel processing of calcium phosphate thin films on silicon substrate by FTIR spectroscopy

Calcium hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, CHAp) films were obtained on silicon substrates by a sol-gel method using a spin-coating technique. In the sol-gel process, ethylendiamintetraacetic acid and 1,2-ethandiol, triethanolamine and polyvinyl alcohol were used as complexing agents and gel network forming agents, respectively. The samples were annealed at 1000 °C for 5 h in air after each spinning procedure. Spin-coating and annealing procedures were repeated 5, 8 and 10 times. The coatings were characterized using X-ray diffraction (XRD), scanning electron microscopy- energy dispersive X-ray spectroscopy (SEM-EDX) and Fourier Transform infrared spectroscopy (FTIR). FTIR-spectroscopy allowed us to predict the formation of oxyhydroxyapatite Ca₁₀(PO₄)₆(OH)_2-2xO_x on the Si substrate. Moreover, according to the FTIR results, the side phase β-Ca₃(PO₄)₂ has been formed instead of α-Ca₃(PO₄)₂. In addition, the anhydrous dicalcium, phosphate phase CaHPO₄ was also detected spectroscopically.     

Purification of Biliary Protein and Its Effect on Calcium Carbonate Mineralization

The biliary protein (BP) was isolated from pig bile by gel filtration. The interaction between Ca²⁺ and protein was measured by fluorescence spectra. The result showed that there was a strong coordination between biliary protein and Ca²⁺. The CaCO₃ crystals obtained in systems with and without BP were characterized by scanning electron microscopy, Fourier transform infrared spectrography and powder X‐ray diffractometry. The possible formation mechanism of CaCO₃ in biliary protein solution was discussed.     

Effects of PAA additive and temperature on morphology of calcium carbonate particles

Calcium carbonate particles with various shapes were prepared by the reaction of sodium carbonate with calcium chloride in the absence and presence of a polyacrylic acid (PAA) at 25°C and 80°C, respectively. The as-prepared products were characterized with scanning electron microscopy and X-ray diffraction. The effects of pH, temperatures, aging time and concentration of PAA and CaCO₃ on the crystal form and morphologies of the as-prepared CaCO₃ were investigated. The results show that pH, temperatures, concentration of PAA and CaCO₃ are important parameters for the control of morphologies of CaCO₃. Various crystal morphologies of calcite, such as, plates, rhombohedras, rectangles, ellipsoids, cubes, etc. can be obtained depending on the experimental conditions. Especially, the monodispersed cubic calcite particles can be produced by PAA addition at 80°C. Moreover, higher temperature is beneficial to the formation of monodispersed cubic or rectangular calcite particles. This research may provide new insight into the control of morphologies of calcium carbonate and the biomimetic synthesis of novel inorganic materials.     

Synthesis and characterization of sulfonated polymethylsiloxane polymer as template for crystal growth of CaCO3

The objective of this work was to synthesize a sulfonated polymethylsiloxane (S-PMS) by hydrosilylation and sulfonation reactions and to investigate their effect on the growth of CaCO₃ crystals using a gas diffusion method as a function of concentration, pH, and time. The result of IR and NMR shows good agreement with all proposed structures. Scanning electron microscopy images of CaCO₃ showed small well-defined calcite-forming short piles (ca 5 μm) and elongated calcite (ca 20 μm) crystals. The morphology of the resultant CaCO₃ crystals reflects the electrostatic interaction of sulfonate moieties and Ca²⁺ modulated by S-PMS adsorbed onto the CaCO₃ surface. X-ray diffraction confirmed the crystalline calcite polymorph. Energy dispersive spectroscopy of CaCO₃ crystals determined the presence of Si atoms from S-PMS. The use of PMS chemistry as an organic additive for the production of CaCO₃ particles is a viable approach for studying the biomineralization and could be useful for the design of novel materials with desirable shape and properties.