Convenient Procedures for Obtaining Pure C60 and C70 in Relatively Large Quantities

It is shown that by using appropriate mixtures of activated charcoal and silica gel as adsorbents, relatively large quantities of C₆₀ and C₇₀ can be prepared in pure form, by a simple filtration procedure.     

The effect of lamellar separation on the properties of a Ti–46Al–2Nb–2Cr intermetallic alloy

The relationships between the γ and ₂ lamellae apparent separation and hardnesses as well as the peak flow stresses estimated in hot compression tests obtained for specimens made of Ti–46Al–2Nb–2Cr alloy are presented. The lamellae separations were estimated using image analysis on the microstructure of the specimens. The procedure employing a fast Fourier transformation of secondary electron microstructural images for fully automatic lamellae separation measurements is described. It was found that the effect of the apparent lamellae separations of γ and ₂ on the peak flow stress is significant. For the microstructure with thick lamellae of γ and ₂ phases, the peak flow stress decreases. The hardness of the specimens decreases with an increase of the lamellae apparent separation as well.     

Al3+/Yb3+/P5+掺杂对石英玻璃紫外透过和紫外激发荧光的影响

采用溶胶-凝胶法结合高温真空烧结工艺制备了不同浓度的Al³⁺/Yb³⁺/P⁵⁺掺杂石英玻璃。研究了P⁵⁺和Al³⁺的引入对Yb³⁺掺杂石英玻璃紫外透过和紫外激发荧光光谱, 以及Yb4d电子结合能的影响, 并初步探索了其机理。研究结果表明, Al³⁺/Yb³⁺/P⁵⁺掺杂石英玻璃在190~300 nm波段的吸收主要来源于O^2-→Yb³⁺的电荷迁移吸收, 其谱带位置和Yb4d电子结合能随Yb³⁺的第二配位元素(Al、Si、P)电负性增大向高能方向移动。真空烧结条件下, 引入Al³⁺会引发石英玻璃中Yb³⁺还原为Yb²⁺, 其典型的吸收峰位于330 nm处; 然而, 在Al³⁺/Yb³⁺共掺的基础上再引入P⁵⁺, 且P⁵⁺/Al³⁺摩尔比大于1时, 可以有效抑制Yb²⁺的形成。紫外光激发引起的近红外发光(976 nm)是电子从电荷迁移态弛豫到Yb³⁺激发态向基态跃迁的结果, 可见发光(525 nm)归因于Yb²⁺的5d→4f跃迁。本文研究结果对通过优化工艺和调整组分制备出高性能的Yb³⁺掺杂光纤具有一定的指导意义。     

憎水二氧化硅膜的制备、表征及水热稳定性研究

用甲基三乙氧基硅烷(MTES)代替部分正硅酸乙酯(TEOS)作为前驱物,通过共水解缩聚反应可制得甲基修饰的二氧化硅膜.通过TGA、FTIR以及气体渗透等测试手段对甲基修饰的SiO₂膜进行研究,发现随着MTES/TEOS摩尔比例的增大,二氧化硅膜的憎水性能逐渐增强,当MTES/TEOS达到0.8时,二氧化硅膜的孔表面几乎不再吸附水气.氢气在MTES/TEOS为1的支撑体二氧化硅膜的输运受温度的控制,200℃时H₂的渗透率达到6.0×10^-7mol·m^-2.Pa^-1·s^-1,H₂/CO₂分离系数达到6.0,于200℃以及水蒸气压力为3564Pa的环境中陈化近110h后H2渗透率基本保持不变,H₂/CO₂分离系数有所增大,说明经过甲基修饰的二氧化硅膜比纯二氧化硅膜具有更好的水热稳定性.     

AlB2对高硅氧纤维/可瓷化酚醛树脂复合材料及其裂解产物力学性能的影响

以AlB₂和SiC颗粒填充酚醛树脂作为基体,高硅氧纤维作为增强体,制备了高硅氧纤维/可瓷化酚醛树脂复合材料。研究了不同添加量的AlB₂颗粒对高硅氧纤维/可瓷化酚醛树脂复合材料常温和1 200℃裂解产物性能的影响,并分析了AlB₂颗粒对其裂解产物的增强机制。结果表明:随着AlB₂颗粒的添加,高硅氧纤维/可瓷化酚醛树脂复合材料常温下的弯曲强度逐渐减小,但其1 200℃裂解产物的弯曲强度先增大后减小。当AlB₂颗粒与酚醛树脂的质量比为12%时,裂解产物的弯曲强度提高最为显著,相比未添加AlB₂颗粒的复合材料,其裂解产物的弯曲强度提高了16.4%。AlB₂颗粒在1 200℃有氧环境中反应生成由B₂O₃、Al₂O₃和Al₂₀B₄O₃₆组成的共熔体,填充了树脂基体裂解产生的孔隙,明显减少复合材料...     

含Si-O-P键的减反膜结构及性能影响因素研究

采用SiO₂水溶胶(ACS)为硅源, H₃PO₄为桥联剂, H₂O₂为活化剂在玻璃表面成功制备了一种性能优异的新型减反膜。利用FTIR、XRD、FESEM、TEM、AFM对薄膜结构、形成机理及性能进行了研究, 结果表明, 在成胶过程中, H₂O₂的导入有效修复了SiO₂胶粒的表面羟基, 提高了SiO₂的反应活性; 而在焙烧过程中, H₃PO₄通过其自身脱水形成的偏磷酸链状体分别与SiO₂胶粒及玻璃基底表面的Si-OH进行了脱羟基缩聚, 构架了坚固的Si-O-P网络交联, 最终形成了稳定的磷硅酸盐凝胶网络结构, 提高了成膜质量。当n(H₃PO₄) : n(H₂O₂) : n(EtOH) : n(SiO₂)= 0.49: 0.52: 30: 1时, 制备的SiO₂减反膜在可见光区平均透光率高达98%, 硬度可达6H。     

Influence of reduction temperature on coercivities, coercivity factors and rheological properties of γ-Fe2O3and silica coated γ-Fe2O3

The transformation of α-FeOOH into γ-Fe2O3via Fe3O4is studied in order to determine the influence of the reduction temperature on the magnetic and rheological properties of the final product. The study was carried out both on pure and on silica coated α-FeOOH. It was found that the reduction temperature at which a maximum of coercivity is obtained, varies with particle size, and it is much higher for silica coated samples which also show higher coercivity at the optimum reduction temperature. Coercivity factors (CF percent) and Mr/Ms values are also dependent on particle size. It is shown that coating with silica enables the reduction to be carried out at higher temperatures without significant collapse of the acicular shape.     

Photoluminescence characteristics of Ti2S3 nanoparticles embedded in sol–gel derived silica xerogel

Ti₂S₃ nanocrystallites embedded in sol–gel derived silica xerogel have been prepared. Their photoluminescence (PL) characteristics have been evaluated and compared with those of pure silica xerogel. UV–vis absorption spectra, transmission electron micrograph, excitation spectra and PL spectra of the doped and undoped samples have all been investigated. Two emission peaks have been observed from the doped samples, one at 440 nm (λ_ex=380 nm) while the other at 600 nm (λ_ex=550 nm). The latter has been assigned to the Ti₂S₃ nanocrystallites in the silica xerogel. Therefore, a novel luminescence property can be observed by introducing the semiconductor nanoparticles into the silica xerogel.     

Ultrahigh-throughput proteomics using fast RPLC separations with ESI-MS/MS

We describe approaches for proteomics analysis using electrospray ionization-tandem mass spectrometry coupled with fast reversed-phase liquid chromatography (RPLC) separations. The RPLC separations used 50-microm-i.d. fused-silica capillaries packed with submicrometer-sized C18-bonded porous silica particles and achieved peak capacities of 130-420 for analytes from proteome tryptic digests. When these separations were combined with linear ion trap tandem mass spectrometry measurements, approximately 1000 proteins could be identified in 50 min from approximately 4000 identified tryptic peptides; approximately 550 proteins in 20 min from approximately 1800 peptides; and approximately 250 proteins in 8 min from approximately 700 peptides for a S. oneidensis tryptic digest. The dynamic range for protein identification with the fast separations was determined to be approximately 3-4 orders of magnitude of relative protein abundance on the basis of known proteins in human blood plasma analyses. We found that 55% of the MS/MS spectra acquired during the entire analysis (and up to 100% of the MS/MS spectra acquired from the most data-rich zone) provided sufficient quality for identifying peptides. The results confirm that such analyses using very fast (minutes) RPLC separations based on columns packed with microsized porous particles are primarily limited by the MS/MS analysis speed.     

Overloading study of bases using polymeric RP-HPLC columns as an aid to rationalization of overloading on silica-ODS phases

The separation of ionized bases by reversed-phase liquid chromatography with alkyl silica columns often leads to severely tailed bands that are highly detrimental. Band shape and its dependence on sample mass are notably different when mobile-phase pH is changed, and this behavior has not been previously explained. Ionized silanols present in the stationary phase have been credited with a role in determining peak shape. In the present study, separations on two different polymer columns were compared with those previously obtained on alkyl silica phases. Because silanols are absent from polymer columns, this comparison enabled us to assess the role of silanols in separations on alkyl silica phases and to offer an explanation of why band shape changes with sample size and mobile-phase pH for both polymer and silica-based phases.     

形核密度对AlON粉体合成及其透明陶瓷制备的影响

以α-Al₂O₃为原料, 采用碳热还原氮化法合成AlON粉体, 利用活性炭和亚微米碳粉改变球磨后一次粉体(α-Al₂O₃和C混合粉体)的形核密度, 并研究形核密度对AlON粉体相组成、形貌及其透明陶瓷透光性的影响。结果表明, 形核密度不同的一次粉体在1750℃保温60 min均能合成纯相AlON粉体, 但是所合成的两种AlON粉体形貌和性能差异较大。高形核密度下(添加活性炭)合成的AlON粉体形貌不规则、结构疏松且晶粒较小, 并易于球磨获得细颗粒粉体(~0.93 μm); 而低形核密度下(添加亚微米碳粉)合成的AlON粉体整体形貌呈近球形, 晶粒发育较完整, 且尺寸较大, 该粉体球磨后颗粒尺寸较大(~2.13 μm)。因此, 形核密度是影响AlON粉体形貌、结构特征和破碎性的主要因素。研究结果表明, 高形核密度粉体合成的AlON粉体具有更好的烧结活性, 它在1880℃保温150 min获得的透明陶瓷最大红外透过率达76.5% (3 mm厚), 比低形核密度粉体制备的透明陶瓷提高48.3%。因此, 以α-Al₂O₃为原料时, 提高形核密度有利于制备颗粒较小的高活性AlON粉体, 该粉体适合制备高透过率AlON透明陶瓷。     

A (-)-menthyl bonded silica phase for chiral separations: synthesis and solid state NMR characterization

A new (-)-menthyl bonded silica phase has been prepared by hydrosilation of a hydride silica intermediate. The hydride silica intermediate was synthesized by the reaction of a monoalkoxysilane (CH(3))(2)SiH(OEt) with silica gel, yielding a relatively high surface coverage (4.4 μmol/m(2)) of SiH groups. This intermediate was then used successfully in the preparation of a monomeric (-)-menthyl bonded silica phase. The bonded phase produced has been used for the chromatographic separation of enantiomers in a reversed phase mode (chiral separations). Solid state (13)C and (29)Si CP-MAS NMR spectroscopy and DRIFT spectroscopy provides valuable information on the structure of the different surface species formed on silica after modification. The surface coverage of the hydride silica intermediate and of the final bonded silica phase produced are also determined. It is found that this modification procedure can exclusively produce a monomeric coverage of SiH groups on the silica surface and can further produce a final monomeric bonded organic silica phase for the separation of enantiomers.     

Removal of siloxanes in biogases

Methods for the removal of gaseous silicon compounds in biogases are presented. In laboratory studies, various solid adsorption materials and liquid absorption solutions were evaluated for their siloxane elimination efficiencies. Among the liquid sorbents studied, concentrated nitric acid and sulfuric acid were found to be especially potent siloxane removing agents at elevated temperature. Solid adsorbents tested include activated charcoal, carbopack B, Tenax TA, XAD II resins, molecular sieve 13X and silica gel. Apart from activated charcoal, silica gel showed especially high adsorption capacities of more than 100mg/g for siloxanes. Furthermore, excellent thermal regeneration of the loaded material was possible. The efficiency of silica gel in removing gaseous siloxanes was verified at a sewage treatment plant, where an adsorption bed with silica gel was used for biogas drying. Other gas pretreatment installations studied included refrigeration condensers and adsorbent beds of meadow ore for the catalytic removal of hydrogen sulfide. In contrast to biogas drying by refrigeration, which had a poor effect on siloxane content, the installation of meadow ore adsorption beds resulted in a significant siloxane reduction of 31-75%, depending on the site studied.     

Mechanical properties and microstructure of bioactive ORMOSILs containing silica particles

We synthesized organically modified silicate (ORMOSILs) gels with colloidal silica (CS) (AEROSIL®) starting from polydimethylsiloxane (PDMS), tetraethoxysilane (TEOS) and calcium nitrate (Ca(NO₃)₂·4H₂O) through sol–gel processing. Dynamic mechanical analysis indicated that relative height of the tanδ peak at about −100 °C increased with an increase in the relative content of the inorganic components. This peak growth was accounted for by the relative increase in PDMS–colloidal silica particle interactions. The colloidal silica could control the mechanical behavior of the hybrids. The gel of a specific composition could deposit apatite within 3 days of soaking in the simulated body fluid (SBF), since it included many calcium ions on the surface.     

Synthesis of AlN by reactive sputtering

We present a systematic study of the sub-band gap optical absorption coefficients (hν) in the range 1.2–6 eV vs. deposition-temperature (T_s from 27 to 450°C) films deposited on silica by 13.6 MHz magnetron sputtering of an Al target with 53 and 72% N₂ in the reactive mixture. X-ray diffraction, infrared absorption and Raman diffusion are also presented, mainly on films deposited on Si in the same run to help in the characterisation of the films. All signals are specific of AlN polycrystalline films, which are of better quality when deposited with 72% N₂. The lowest sub-band gap optical absorption around 5×10² cm⁻¹ is obtained for deposition on silica at T_s=300°C with 72% N₂ and is close to that of heteroepitaxial films deposited on sapphire.     

中空SiO2微球的制备及其在缓/控释应用中的新进展

中空二氧化硅(SiO₂)微球具有特殊的内部空腔、吸附渗透性好、物质传递可控等优异性能, 可储存负载并缓慢释放药物、香精、染料、菌素等客体分子, 因此在药物缓释、医学成像、环境保护以及化妆品等领域有着广阔的应用前景。根据国内外研究进展, 本文归纳对比了中空SiO₂微球几种制备方法之间的优劣差异, 着重阐述了其作为缓控释载体表现出的持久性和高效性, 以及功能化的有机/无机杂化微球在响应性控释方面的优越性。并对中空SiO₂微球作为新型缓控释载体的发展前景进行了展望。     

Plate heights below 50 nm for protein electrochromatography using silica colloidal crystals

Silica colloidal crystals formed from 330 nm nonporous silica spheres inside of 75 μm i.d. fused silica capillaries were evaluated for the efficiency of capillary electrochromatography of proteins. Three proteins, ribonuclease A, cytochrome C, and lysozyme, each covalently labeled with fluorophor, were well separated over a distance of 1 cm by isocratic electromigration, using 40:60 acetonitrile/water with 0.1% formic acid. A van Deemter plot showed that the plate height for lysozyme, which was the purest of the three proteins, was diffusion-limited for electric fields ranging from 400 to 1400 V/cm. The plate height for lysozyme was below 50 nm at almost all of the migration velocities, and it approached 10 nm at the highest velocity. Eddy diffusion was negligible. Lysozyme migrated over a 12 mm separation length with more than 10(6) plates in 1.5 min. These results indicate that silica colloidal crystals are well suited for electrically driven separations of large, highly charged analytes such as proteins. The 10(6) plates observed for a separation length of barely more than a centimeter means they are potentially valuable for miniaturized separations in microchip and lab-on-a-chip devices.     

溶胶-凝胶法制备Al3+、Yb3+掺杂石英光纤纤芯的研究

以正硅酸乙酯、氯化铝和氯化镱为前驱体, 用溶胶-凝胶法制备了Al³⁺、Yb³⁺掺杂石英光纤纤芯。采用ICP-AES分析发现: 碱催化的掺杂硅凝胶上下层组分存在较大差异, 酸催化条件能够消除组分差异。将酸催化溶胶经凝胶化、热处理、玻璃化、光学加工, 获得了φ2.5 mm×50 mm的芯棒。测试2 mm厚芯棒玻璃的光谱和荧光寿命, 1020 nm的荧光寿命为896 μs, 羟基含量为0.4×10^-6, 并通过显微拉曼光谱分析玻璃结构。采用管棒法制备预制棒, 2000℃高温拉制了Al³⁺、Yb³⁺掺杂单包层石英光纤。用光纤折射率分布测试仪测得纤芯折射率波动Δn小于2×10^-4, 表明纤芯具有良好的光学均匀性。本研究结果提供了一种大模场掺镱石英光纤纤芯材料的制备方法, 并为溶胶-凝胶法制备均匀多组分材料的研究提供了理论参考。     

Synthesis of novel thiol-functionalized mesoporous silica nanorods and their sorbent properties on heavy metals

Novel thiol-functionalized mesoporous silica nanorods (MSNRs) were synthesized through a base co-condensation method, in which two organoalkoxysilanes, tetraethoxylsilane (TEOS) and bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT), were used as silica precursors simultaneously. TESPT was firstly used for both morphology control and inner surface functionalization of mesoporous silica hybrid materials. The microstructures as well as porous character of the MSNRs were characterized by means of SEM, XRD, TEM and N₂ sorption measurements. Infrared spectrum analysis and heavy metal ions (Ag⁺ and Cd²⁺) adsorption measurements were carried out to confirm the functionalized framework of MSNRs.     

载银纳米TiO2抗菌竹炭的制备

以工业TiOSO4为原料,分别通过水解法和胶溶法制备载银纳米TiO2抗菌竹炭.采用XRD和SEM对样品进行了表征,研究了不同载银量、煅烧温度、TiO2/C和竹炭粒径对抗菌率的影响.结果表明,水解法制备的抗菌竹炭的抗菌效果优于胶溶法制备的抗菌竹炭,控制载银量、煅烧温度、TiO2/C、竹炭粒径分别为2%、500℃、2%、200目时,水解法制备的抗菌竹炭抗菌率最佳;控制载银量、煅烧温度、TiO2/C、竹炭粒径分别为3%、500℃、3%、200目时,胶溶法制备的抗菌竹炭抗菌率最佳.