Production mechanism of polytitanocarbosilane and its conversion of the polymer into inorganic materials

The reaction of polycarbosilane with tetra-alkyltitanate proceeded at 300° C in nitrogen atmosphere by the condensation of Si-H bonds in polycarbosilane and the substituent groups of the tetra-alkyltitanate accompanied by evolution of alkan gas, and then the formation of Si-O-Ti bonds occurred. In this condensation reaction using tetra-isopropyl titanate, tetra-n-butyl titanate and tetra-2-ethylhexyl titanate, activation energies of the initial rate of the increase in molecular weight were 17.04, 20.07 and 31.07 kcal mol^–1 respectively, and thus the more bulky the substituent group of tetra-alkyltitanate, the lower the reactivity became. Of these alkyltitanates, tetra-2-ethylhexyl titanate was found to be the most advantageous reactant for obtaining polytitanocarbosilane with a narrow molecular weight distribution, low gel fraction and high titanium concentration. Polytitanocarbosilane with high titanium concentration was converted into the densified amorphous inorganic material with high Si-C bonding energy in high yield. Titanium contained in the pyrolysed polytitanocarbosilane was furthermore found to have the effect of inhibiting crystalline grain growth of -type SiC up to high temperature.     

29Si MAS-NMR investigation of the conversion process of a polytitanocarbosilane into SiC-TiC ceramics

A polytitanocarbosilane has been prepared from polycarbosilane and titanium n-butoxide.²⁹Si MAS-NMR was used to characterize the various steps of the conversion process of the polymer into the final ceramic. The reaction of titanium butoxide with polycarbosilane introduces oxygen into the polymer that seems to play an important role in the pyrolysis process. In the first stage up to 1000 ° C, the study reveals the cleavage of Si-C bonds and the formation of SiC_4-xO_x units. In the second stage, above 1000 ° C, the number of Si-O bonds decreases, probably due to a carbothermal reduction process. At 1500 ° C, the product can be described as a mixture of crystalline SiC and TiC with no excess carbon.     

Synthesis of organic–inorganic hybrid composite and its thermal conversion to porous bioactive glass monolith

We report the synthesis and bioactivity studies of 3-dimensional macro-porous material produced by thermal treatment of organic–inorganic hybrid composite. This is prepared by sol–gel processing of co-poly(methylmethacrylate (MMA)-vinyltriethoxysilane (VTS)) with tetraethoxysilane (TEOS), calcium nitrate and zinc nitrate, ([CH₂C(CH₃)(CO₂CH₃)]_0.8n-[CH₂-CH(Si(OEt)₃]_0.2n-SiO₂-CaO-ZnO) (1). Thermal treatment of this polymer at 600 °C yielded macro-porous bioglass monolith, with pore size distribution between 1 and 5 μm and showed excellent bone bonding ability in simulated body fluid. The ratio of VTS:MMA in the organic polymer can easily be controlled. Since the VTS is the bonding agent, the amount of VTS in the co-polymer can be utilized to increase or decrease the porosity of the hybrid composite. This may be a convenient approach for preparation of bioglass scaffolds especially in tissue engineering of bone.     

Synthesis and electrorheological performance of nanosized composite with polar inorganic compounds

To obtain an economical and applicable electrorheological (ER) material, a novel nanocomposite composed of polar inorganic compounds, NH₄Al(OH)₂CO₃, AlO(OH) and (NH₄)₂SO₄, has been synthesized using low-toxic and economical and facile starting materials by a simple chemical reaction process. The experimental result shows that this material has better ER performance. The static yield stress (τ_y) of the suspension (50 wt%) of the material in silicone oil reached 22.8 kPa at a DC electric field of 4 kV/mm, and the relative yield stress (τ_r) (the ratio of the yield stresses with to without an electric field) is also higher (12.7-33.3 for different concentration suspensions). The composition, grain size, dielectric and surface properties of the material have been studied by the elemental analyses, X-ray diffraction (XRD), infrared spectroscopy (IR), transmission electron microscopy (TEM), dielectric spectroscopy and determinations of the surface area and surface energy of the material. The influences of the grain size, dielectric and surface properties on ER performance of the material have been discussed.     

Production mechanism of polyzirconocarbo- silane using zirconium(IV)acetylacetonate and its conversion of the polymer into inorganic materials

The reaction of polycarbosilane with zirconium(IV)acetylacetonate proceeded at 573 K in nitrogen atmosphere by the condensation reaction of the Si–H bonds in polycarbosilane and the ligands of zirconium(IV)acetylacetonate accompanied by the evolution of acetylacetone, and then the molecular weight increased by the cross-linking reaction with a formation of Si–Zr bond. The obtained polyzirconocarbosilane showed higher ceramic yield than the polycarbosilane. Zirconium contained in the pyrolysed polyzirconocarbosilane was furthermore found to have the effect of inhibiting crystalline grain growth of -type SiC up to high temperature, so Si–Zr–C–O fibre, which was obtained by the use of polyzirconocarbosilane as precursor, showed high tensile strength up to high temperature.     

Gas-phase conversion of U,Sr, and Mo compounds into water-soluble forms in a nitrating atmosphere

Gas-phase conversion of uranyl molybdates UO₂MoO₄, UMo_1.7O_7.2, and UMo_0.4O_3.4, of strontium molybdate SrMoO₄, and of strontium uranate SrUO4 into water-soluble compounds in the NO_x–H₂O (vapor)–air or HNO₃ (vapor)–air atmosphere (hereinafter, nitrating atmosphere) was studied. The conversion of UO₂MoO₄, UMo_1.7O_7.2, and UMo_0.4O_3.4 in nitrating atmosphere results in formation of water-soluble uranium compounds and of the water-insoluble phase MoO₃·2H₂O. Rapid separation of the solution from the precipitate in reaction of UO₂MoO₄, UMo_1.7O_7.2, and UMo_0.4O_3.4 conversion products with water allows efficient transfer of U into the solution, with Mo remaining in the form of an insoluble precipitate. The conversion of SrMoO4 depends on the composition of the nitrating atmosphere. In the NO_x–H₂O (vapor)–air atmosphere, there is no SrMoO₄ conversion, whereas in the HNO₃ (vapor)–air atmosphere it is possible to reach ~85% conversion of SrMoO₄ into water-soluble Sr compounds. Complete conversion of SrUO₄ into water-soluble U and Sr compounds is reached when performing the gas-phase conversion at 130°С in both nitrating atmospheres. In the case of the HNO₃ (vapor)–air atmosphere, increasing the process temperature to 150°С leads to a decrease in the amount of water-soluble U(VI) phases.     

三氯环硼氮烷改性聚碳硅烷的合成及陶瓷转化

为研究三氯环硼氮烷(TCB)对聚碳硅烷(PCS)性能及陶瓷转化的影响,将一定量的TCB加入PCS中制备TCB改性PCS聚合物,分析了TCB与PCS的反应性及TCB用量对改性PCS结构、陶瓷收率、可加工性和SiC产物微结构的影响,并采用红外光谱、热重、X射线衍射等测试技术对相应产物进行表征.结果表明,PCS中的Si-H键可部分地与TCB中的-Cl反应生成HCl;随着TCB质量分数的增加,PCS中Si—H键相对于Si-CH3的浓度比呈下降趋势.TCB的加入可显著提高PCS的陶瓷收率,TCB质量分数大于8%时,陶瓷收率质量分数约增加10%.TCB质量分数为5%～8%时,可在提高PCS收率的同时使其保持较好的可加工性能,TCB质量分数大于8%时,可加工性能变差.B、N的引入对SiC的微结构有影响:在氩气保护下,经1000℃热处理时,TCB的加入促进SiC晶粒的生长;经1400℃热处理时,TCB的加入抑制SiC晶粒的长大.     

Synthesis and properties of graphene and its 2D inorganic analogues with potential applications

Discovery of the amazing properties of graphene has aroused great interest in other 2D materials. 2D inorganic analogues of graphene such as the transition metal dichalcogenides have been investigated widely and these materials, especially \({\hbox {MoS}_{2}}\), exhibit many properties of interest. In particular, they possess properties of direct use in energy devices. In this article we review the synthesis and properties of the 2D materials of relevant transistors, sensors, photodetectors, supercapacitors and batteries as well as in oxygen reduction and hydrogen evolution reactions.     

微孔无机膜的制备与改性

较系统地介绍了溶胶－凝胶法在膜制备中的应用，对阳极氧化法、化学气相沉积法以及刚刚发展起来的沸石子筛膜、炭膜的制备工艺也做了简单介绍，并对膜的改性技术进行了回顾。     

Synthesis and characterisation of organic-modified inorganic nanorods

Gold and cadmium sulphide nanorods with aspect ratios ≈5 were synthesised in quantities of several hundred milligrams via surfactant-driven seed-mediated processes. Such nanorods then underwent surface-modification processes in which the surfactant coating was at least partially replaced with both commercially available alkanethiols and synthesised organic molecules with the intention of forming hybrid organic–inorganic nanorods capable of exhibiting liquid crystalline-like ordering. An increase in the localised alignment of functionalised nanorods was observed in transmission electron microscope images. Additional characterisation of these novel hybrid molecules has been performed using polarised optical microscopy, differential scanning calorimetry, energy dispersive X-ray spectroscopy, nuclear magnetic resonance and UV-Visible absorption spectroscopy.     

Adaptive conversion of a high-order mode beam into a near-diffraction-limited beam

We present a new method for efficiently transforming a high-order mode beam into a nearly Gaussian beam with much higher beam quality. The method is based on modulation of phases of different lobes by stochastic parallel gradient descent algorithm and coherent addition after phase flattening. We demonstrate the method by transforming an LP11 mode into a nearly Gaussian beam. The experimental results reveal that the power in the diffraction-limited bucket in the far field is increased by more than a factor of 1.5.     

无机层状化合物及其应用述评

无机层状化合物及其层间改性产物具有广阔的应用前景。本文综述了层状化合物的最新研究进展 ,以及利用层间嵌入反应制备纳米复合材料的方法和应用。     

Synthesis of sodium and potassium aluminogermanate inorganic polymers

Synthesis of aluminogermanate inorganic polymers containing sodium as the charge-balancing ion was attempted by reacting NaAlO₂ solution with GeO₂ in an adaption of a sol-gel synthesis for aluminosilicate inorganic polymers. XRD and ²⁷Al MAS NMR suggested that only a small degree of reaction had occurred, based on the presence of unreacted GeO₂ and a trace of Na₃HGe₇O₁₆·4H₂O, with only a small amount of the tetrahedral aluminium characteristic of a true inorganic polymer. The addition of KOH markedly enhanced the reaction, producing a (Na,K) product with properties characteristic of a true inorganic polymer (an amorphous X-ray powder pattern and predominantly tetrahedral aluminium). An attempt to synthesise the potassium end-member aluminogermanate compound by replacement of the NaAlO₂ in the above synthesis with KAlO₂ produced only crystalline K(AlGeO₄)H₂O and K₃HGe₇O₁₆·4H₂O containing solely tetrahedral aluminium. Attempts to extend these syntheses to the gallium analogues of these aluminogermanate compounds were unsuccessful, producing only the crystalline products K(GaGeO₄)₆·7H₂O and K₃HGe₇O₁₆·4H₂O. Thus, the most successful sol-gel synthesis of a germanate compound with the properties of an inorganic polymer was of an aluminogermanate containing Na⁺ and K⁺ as the exchangeable cations.     

High-surface area inorganic compounds prepared by nanocasting techniques

This paper is a survey of the nanocasting methods used for the synthesis of nanosized and nanostructured inorganic compounds. Special attention is paid to the use of porous materials such as mesostructured silica, silica gel, and carbonaceous materials as hard templates for the preparation of metallic oxides. General aspects concerning the applications of materials obtained by hard-templating procedures are also reviewed.     

三氟甲基化合物的合成

利用三氟甲基化试剂可有效地在各种化合物中引入三氟甲基,以此增强其生理活性和特殊性能,使三氟甲基化合物在农药、医药、材料、染料等领域的应用愈加广泛。综述了新型三氟甲基化试剂的研究动向与各种三氟甲基化的方法,探讨了三氟甲基化合物合成领域的发展方向。     

含氟芳香族化合物合成方法

介绍了含氟芳香羧酸的合成方法,并列举了一些重要医药中间体的合成路线。