高硅氧发光玻璃的制备及其荧光性能

石英玻璃具有低膨胀、耐热冲击、高机械强度和高化学隐定性等优点,是稀土和过渡金属发光离子掺杂的优选的基质材料。但发光离子在石英玻璃中容易自发形成团簇,产生浓度淬灭效应,介绍一种用二氧化硅质量分数超过95%的纳米微孔玻璃来抑制发光离子团簇的自发形成的新方法,以制备高发光强度的石英破璃和激光玻璃。该方法是将发光离子浸入微孔玻璃中并在适当气氛中烧结,目前已经制得多种颜色、量子效率接近于1的强发光玻璃,真空紫外光激发发光玻璃,高铒离子掺杂的高硅氧玻璃,还获得了新颖的低膨胀、耐高温的掺钕高硅氧激光玻璃和掺铋红外宽带发光玻璃用这种方法还容易进行多种发光活性离子掺杂,实现不同离子间的能量转换,提高发光强度和改变激发光的波长范围。这种新方法有望扩大石英发光玻璃的应用范围。     

A novel cost-effective and near-net-shape fabrication process for SiO2f/SiO2 composites

In this study, we present a novel preparation process named vacuum-assisted slurry infiltration (VASI) for obtaining the SiO_2 f/SiO₂ composites. This method displays remarkably improvement in manufacturing cycles since it allows adopt the ceramic slurries with high solid content as well as low viscosity. Through the porous matrix design of combining coarse particles with fine particles, a homogeneous porous matrix is achieved. The SiO_2 f/SiO₂ composites prepared by the VASI method exhibit the rivaling flexural and tensile strength at 48.8 and 16.4 MPa, respectively. Meanwhile, such porous matrix can enable cracks deflecting and dissipating crack energy by fiber pullout and fiber debonding mechanisms. In comparison, composites fabricated via silica sol infiltration show lower mechanical properties and brittle fracture behavior due to the formation of some defects in the matrix. This work make the prospect for meeting the requirements of low-cost, short preparation cycles, and near-net-shape manufacturing technology for SiO_2 f/SiO₂ composites becomes realizable.     

Synthesis,characterization, and evaluation of unsupported porous NiS submicrometer spheres as a cathode material for lithium batteries

Synthesis of a nanostructured pure phase nickel sulfide in a single step is a challenge. In this work, a new method for direct synthesis of uniform NiS–SiO₂ submicrospheres was developed by ultrasonic spray pyrolysis. Colloidal silica was used as a sacrificial template to create the porous structure. After silica removal, hollow, porous pure phase NiS nanospheres were obtained. The product was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, transmission electron microscopy, and N₂ adsorption/desorption isotherm. The results confirmed the formation of single phase millerite NiS porous nanospheres with a high surface area of 312 m² g^?1. The NiS spheres were tested as cathode for lithium batteries. A discharge capacity of 340 mAh g^?1 with good capacity retention during multiple cycles was obtained.     

Preparation of silica nanospheres and porous polymer membranes with controlled morphologies via nanophase separation

ABSTRACT: We successfully synthesized two different structures, silica nanospheres and porous polymer membranes, via nanophase separation between silica sol and polymer. Silica sol, which was in-situ polymerized from tetraorthosilicate, was used as a precursor. Subsequently, it was mixed with a polymer that was used as a matrix component. It was observed that nanophase separation occurred after the mixing of polymer with silica sol and subsequent evaporation of solvents, resulting in organizing various structures, from random network silica structures to silica spheres. In particular, silica nanospheres were produced by manipulating the mixing ratio of polymer to silica sol. The size of silica beads was gradually changed from micro- to nanoscale, depending on the polymer content. At the same time, porous polymer membranes were generated by removing the silica component with hydrofluoric acid. Furthermore, porous carbon membranes were produced by using carbon source polymer through the carbonization process.     

Cellulose acetate–silica fume membrane: characterization and application for separation of starch and maltose

Maltose is one of the starch derivatives. Maltose can be produced by starch hydrolysis using any kind of hydrolytic process. One of the methods to separate a mixture of both compounds is using porous membrane. In this research, a novel type of hybrid membrane was prepared from a mixture of cellulose acetate and silica fume. Silica fume is widely used in the domain of construction as cement material, whereas in this research silica fume was successfully used as membrane material. Various compositions of membrane dope solutions were prepared for obtaining the membranes used for separation of starch and maltose. Such synthesized membranes demonstrate a good performance in separation processes. The best performance is achieved when the composition of cellulose acetate in membrane dope solution is 15 % (w/w) in N,N-dimethylacetamide solvent and the mass ratio between cellulose acetate and silica fume is 4:1. For this composition, the rejection of membranes towards starch and maltose is 87 and 2 %, respectively, at working pressure of 3 bar and compaction time of 2 h. Infrared spectrum indicates no new peaks are found compared to raw materials’ spectral peaks. Thus, it can be concluded that the interaction between the cellulose acetate and silica fume is merely a physical type. From the observation of cross-sectional SEM images, we can remark that the morphology of such a membrane is porous. X-ray diffractogram indicates that the synthesized membranes are amorphous.     

Direct-writing of PbS nanoparticles inside transparent porous silica monoliths using pulsed femtosecond laser irradiation

Pulsed femtosecond laser irradiation at low repetition rate, without any annealing, has been used to localize the growth of PbS nanoparticles, for the first time, inside a transparent porous silica matrix prepared by a sol-gel route. Before the irradiation, the porous silica host has been soaked within a solution containing PbS precursors. The effect of the incident laser power on the particle size was studied. X-ray diffraction was used to identify the PbS crystallites inside the irradiated areas and to estimate the average particle size. The localized laser irradiation led to PbS crystallite size ranging between 4 and 8 nm, depending on the incident femtosecond laser power. The optical properties of the obtained PbS-silica nanocomposites have been investigated using absorption and photoluminescence spectroscopies. Finally, the stability of PbS nanoparticles embedded inside the host matrices has been followed as a function of time, and it has been shown that this stability depends on the nanoparticle mean size.     

三维有序孔道结构的壳聚糖/二氧化硅复合骨架材料的研究

利用胶体晶体模板法制备了具有三维有序孔道结构的壳聚糖/二氧化硅复合骨架材料(3 D-CS/Si).利用SEM、FT-IR、TGA、XRD等手段对其理化性质进行表征.难溶性药物尼莫地平(NMDP)作为代表药物被包载入骨架孔道之中.结果表明二氧化硅的添加能够有效支撑起壳聚糖的多孔聚合物骨架结构,两种组分间存在氢键作用力,壳聚糖比重为23.40%,呈现非晶态.壳聚糖/二氧化硅复合骨架材料作为药物载体有较高的载药量并促进药物的溶出.     

Preparation of porous material from talc by mechanochemical treatment and subsequent leaching

Synthesis of porous silica via mechanochemical treatment of talc and subsequent acid leaching was investigated by X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and N₂ adsorption techniques. Raw talc was ground for different times and then leached with 4 M hydrochloric acid (HCl) at 80 °C. Grinding for 6 h and subsequent leaching for 2 h of raw talc produced the porous silica with a specific surface area of 133 m²/g and total pore volume of 0.22 ml/g. The increase in specific surface area (S_BET) of the porous silica reflected the formation of micropores of 1.21.8 nm and mesopores of 4.05.5 nm in diameter inside the porous structure. The number of micropores decreased with prolonged leaching time, which can be attributed to a condensation reaction. The characteristic of hysteresis loop indicated mainly slit-shaped pores. The apparent activation energy for the leaching process was calculated to be about 21.6 kJ/mol, indicating that the kinetic process of talc leaching was the diffusion-controlled reaction. Mechanochemical treatment may promote the amorphization of talc, being greatly favorable to the subsequent leaching.     

Functionalization of Tailored Porous Carbon Monolith for Decontamination of Radioactive Substances

As the control over radioactive species becomes critical for the contemporary human life, the development of functional materials for decontamination of radioactive substances has also become important. In this work, a three-dimensional (3D) porous carbon monolith functionalized with Prussian blue particles was prepared through removal of colloidal silica particles from exfoliated graphene/silica composite precursors. The colloidal silica particles with a narrow size distribution were used to act a role of hard template and provide a sufficient surface area that could accommodate potentially hazardous radioactive substances by adsorption. The unique surface and pore structure of the functionalized porous carbon monolith was examined using electron microscopy and energy-dispersive X-ray analysis (EDS). The effective incorporation of PB nanoparticles was confirmed using diverse instrumentations such as X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). A nitrogen adsorption/desorption study showed that surface area and pore volume increased significantly compared with the starting precursor. Adsorption tests were performed with ¹³³Cs ions to examine adsorption isotherms using both Langmuir and Freundlich isotherms. In addition, adsorption kinetics were also investigated and parameters were calculated. The functionalized porous carbon monolith showed a relatively higher adsorption capacity than that of pristine porous carbon monolith and the bulk PB to most radioactive ions such as ¹³³Cs, ⁸⁵Rb, ¹³⁸Ba, ⁸⁸Sr, ¹⁴⁰Ce, and ²⁰⁵Tl. This material can be used for decontamination in expanded application fields.     

Characterization and Cu（Ⅱ）adsorption property of rice-husk-char-based porous silica with large specific surface area

以热解稻壳炭为原料,H3PO4为酸化剂,聚乙二醇为模板剂,制得了多孔氧化硅;采用N2吸脱附、X射线荧光光谱、X射线能谱、X射线衍射等测试技术表征了制得的多孔氧化硅,采用批量吸附实验考察了它对水溶液中Cu（Ⅱ）的吸附特性。结果表明：以稻壳炭为原料,可以在10 h内制得比表面积达957 m²·g^-1、二氧化硅含量为99.26%的无定形多孔氧化硅;该氧化硅含有中孔与微孔,中孔率为38.6%相似文献   

Fabrication and characterization of composite sol-gel coatings on porous ceramic substrate

Highly porous ceramic materials were coated using a composite sol-gel method. Alumina powder is dispersed in a silica sol-gel solution and then dip-coated on the substrate. The resulting coatings present a composite microstructure in which crystalline alumina grains are linked to each other by an amorphous silica phase. In this work, we show that, by accurately controlling the sol-gel parameters (water, solvent and silica precursor (TEOS) ratio, pH and ageing time of the sol) and also the powder grain size distribution it is possible to obtain crack-free thick films (more than 20 μm in one step). These coatings present good adherence to the substrate, decrease the roughness and also close the surface porosity of the substrate. Coating mechanical properties have been evaluated thanks to micro-indentation measurements and linked to coating structural evolution with the thermal treatment temperature.     

A non-sintering fabrication method for porous Si3N4 ceramics via sol hydrothermal process

A non-sintering fabrication method for porous Si₃N₄ ceramics with high porosity and high mechanical strength was proposed. Strength of the porous ceramics can be obtained by silica sol mass transfer process in hydrothermal conditions rather than a traditionally controlled high temperature sintering process. Under hydrothermal circumstances, silica sol is continuously transferred to the necks of Si₄N₃ powder compact, depositing there and thus consolidating the ceramic skeleton. The key of the method to obtain homogeneous microstructure and mechanical strength is how to keep the silica sol from gelatin during hydrothermal procedure. The stabilization of silica sol and its affecting factors were studied. The results indicated that ultrasonic treatment makes alkali-catalyzed silica sol remain stable even in 200?℃ hydrothermal condition, which insures consecutive silica transportation. The effect of hydrothermal time on open porosity/mechanical strength of the porous Si₄N₃ ceramics were also thoroughly investigated. The porous Si₄N₃ ceramics with open porosity above 42% and flexural strength of 45?MPa were obtained without any high temperature sintering process. This method can be widely employed for the preparation of other porous ceramics as well.     

SYNTHESIS OF WELL-CRYSTALLIZED ZEOLITE BETA AT LARGE SCALE AND ITS INCORPORATION INTO POLYSULFONE MATRIX FOR GAS SEPARATION

Using a silica source with high specific surface area, aluminum zeolite beta was successfully synthesized in a very short crystallization period through the conventional hydrothermal route. The obtained materials were characterized by means of XRD, TEM, FESEM, EDS, TGA/DTG, and N₂ adsorption/desorption techniques. It is found that the well-crystallized zeolite beta can be rapidly synthesized at 170°C in 9 h and the highly porous silica source used could be completely converted into zeolite beta. No difference results from the silica source used. Moreover, through this synthesis route, it is also possible to conveniently obtain zeolite beta at high yield for manufacturing composite membranes for gas separations. The gas permeation tests show that the incorporation of porous zeolite beta into a polymer has modified the gas permeation properties significantly, indicating industrial application potential of this new type of composite material.     

Preparation of Mesostructured Materials from Tetramethoxysilane and Alkyltrimethylammonium Salts and Their Conversion to Porous Silica

A novel synthetic route for the preparation of the porous silica by a supramolecular templating mechanism is reported. By depositing the precursor solution containing tetramethoxysilane and hexadecyltrimethylammonium chloride on glass plates at an elevated temperature (60°C), mesostructured silica-hexadecyltrimethylammonium chloride composites with the size of a few mm to a cm have been prepared. The composition of the resulting products can be controlled by simply changing the composition of the starting mixtures. By the calcination of the as synthesized mesostructured materials, porous silica with large surface area was obtained. Due to the ease of operation, the present method is a simple way to prepare porous silica alternative to the procedures reported for the preparation of mesoporous silicas (MCM-41 and FSM-16).     

Porous silica supported Co2+-tetrachlorophthalocyanine (CoPcCl-APTES@SiO2): a novel and recyclable organic–inorganic hybrid catalyst for eco-friendly oxidation of secondary alcohols

A novel, selective and recyclable cobalt based catalyst has been synthesized by covalent grafting of Co²⁺-tetrachlorophthalocyanine (CoPcCl) onto porous silica functionalized with 3-aminopropyltriethoxysilane (APTES), and the resulting organic–inorganic hybrid porous material was found to be highly effective catalyst for peroxidative oxidation of secondary alcohols. The porous material was characterized by elemental analysis, diffuse reflectance UV–Visible spectroscopy, ¹³C CPMAS and ²⁹Si CPMAS NMR spectroscopy, X-ray diffraction (XRD), Scanning electron microscopy (SEM), BET surface area analysis, Energy dispersive X-ray fluorescence (ED-XRF), Fourier transform Infrared (FT-IR) and Atomic absorption spectroscopy (AAS) techniques. High turnover frequency, mild reaction conditions, high selectivity for ketones, and easy recovery and reusability of the catalyst renders the present protocol highly essential to address the industrial needs and environmental concerns.     

Co-gelation synthesis of porous graphitic carbons with high surface area and their applications

An easy co-gelation route has been developed to synthesize porous graphitic carbons with high surface areas by using teraethylorthosilicate (TEOS), furfuryl alcohol (FA), and metal nitrates as precursors. Using a one-pot co-gelation process, a polyfurfuryl alcohol–silica interpenetrating framework with metal ions uniformly dispersed was formed during the polymerization of FA and the hydrolysis of TEOS within an ethanol solution of the three precursors. This synthesis process is simple and time-saving in comparison with the conventional preparation methods. During the heat treatment, Fe₇Co₃ alloy nanoparticles were produced by carbothermal reduction and they then catalyzed the graphitization of the amorphous carbon. The graphitic carbons obtained have a high crystallinity as shown by X-ray diffraction, Raman spectroscopy, and high-resolution transmission electron microscopy analysis. The degree of graphitization can be controlled by the varying the loading amount of catalyst. The porous texture of the carbons combines miropores and bimodal mesopores, mainly originating from the silica template formed with different sizes and the loose packing of the graphite sheets. The carbons have large surface areas (up to 909 m²/g) and exhibit excellent electrochemical performance.     

Porous pyridine based polyimide–silica nanocomposites with low dielectric constant

Highly porous polymer–silica hybrid materials were prepared based on the organo-soluble polyimides of four various dianhydride and 2,5-diaminopyridine. 3-Aminopropyltriethoxysilane (APS) was used to increase the intrachain chemical bonding and interchain hydrogen bonding between the polyimide and silica moieties, respectively. The chemical interaction would significantly affect the morphologies and properties of the prepared films. The produced polyimide–silica composites were investigated by X-ray diffraction analysis, scanning electron microscope and thermal analysis tecniques. The effect of silica modified with functional group of 3-aminopropyltriethoxy silane on the porous structure and dielectric properties as well as the thermal stability of films were investigated. Capacitances were determined with a HP4294A at a frequency between 1 kHz and 1 MHz. The dielectric constant was significantly reduced with increasing silica modified with APS. The result indicates that the composite materials are potentially useful in low dielectric materials.     

钛掺杂硅胶块体吸附剂

以陶瓷纤维纸片为基材,顺次经水玻璃、酸性钛盐溶液浸渍共沉淀制得新型陶瓷基钛掺杂硅胶块体吸附剂.多孔介质表面分析显示:掺杂硅胶孔径在0.5～6 nm范围,以中孔为主.Fourier变换红外谱在波数954 cm 1处的特征吸收峰表明吸附剂中形成了Si-O-Ti键.根据掺杂前后固体魔角核磁共振硅谱中硅原子化学位移的变化(向高场方向移动)及X射线光电子能谱中各原子结合能的变化(Ti2p3/2的结合能随钛含量的增加而增加,而Si2p,O1s的结合能则呈相反趋势)进一步表明:钛原子替代硅原子进入硅胶网络.热重分析及烧结实验结果显示:钛掺杂吸附剂具有更好的热稳定性.新型吸附剂优异的吸附性能除了与其高的比表面积相关外,还与Ti-O键对水分子的亲合力紧密相关,其耐热性能增强与形成高热稳定性Ti-O Si键及材料表面导热性能提高有关.     

大孔二氧化硅膜上纳米碳纤维层结构化催化剂载体的制备

1 INTRODUCTION Fast gas-liquid phase reactions over solid cata- lysts easily cause concentration gradient in reactors and catalysts because of relatively slow diffusion as well as the frequent occurrence of low concentration when gasses are dissolved. Such concentration gradi- ent caused by the limitation of mass transfer influ- ences the reaction rate as well as selectivity. Conven- tional strategies for gas-liquid-solid phase catalytic reactions comprise slurry reactors and trickle bed r…