Fabrication and characterisation of neodymium-doped silica glass by sol-gel process

 Neodymium-doped silica glass possesses many properties ideal for high-power laser applications. These include low thermal expansion coefficient, high temperature stability, and low nonlinear index of refraction. For the first time, the sol-gel process has been successfully employed to prepare highly doped neodymia silica glass, up to 5wt% Nd for homogeneous dopant distribution. The optical characteristics of the silica glass and its in-process gel, including the UV/VIS absorption spectra, infrared absorption spectra, fluorescence emission spectrum and the fluorescence lifetime, are measured and analyzed. The structure of the sample is also characterized by means of XRD and SEM. A porous gel is observed to have formed when the heat treatment temperature reaches 300^oC. Wavelength shifts in the absorption peak corresponding to the ⁴I_9/2 to ⁴F_5/2 transition have been observed during the densification process and for different Nd weig ht contents. The FTIR spectra have shown that high temperature heat treatment can greatly reduce the amount of OH groups and organic residue in the silica. We have also shown that a high OH content contributes to weak fluorescence intensity and short fluorescence lifetimes. Received: 3 March 1997 / Accepted: 27 May 1997     

Temperature-driven local rearrangement in the Er environment of Er-doped silica glass films prepared by rf-cosputtering deposition

In this paper, an experimental study is presented on Er:SiO₂ films prepared by an rf-cosputtering deposition technique, and then annealed in the 100-1200 °C range. Samples were characterized by spectrally resolved cathodoluminescence, UV-VIS photoluminescence and Rutherford Backscattering Spectrometry (RBS). Strong optical modifications with temperature were observed, connecting the peculiar features of the Er luminescence activity to those of the silica matrix, namely, the density of nonbridging oxygen hole centers, oxygen-deficient sites and OH groups. In general, a complex phenomenology was observed, involving major local rearrangements of the Er environment. RBS data allowed to evidence migration phenomena, resulting in a compositional change of the films, thus indicating the progressive modification of the system as well as the possible formation of Er nanoclusters for high temperatures.     

Sol-gel silica thin films with copper selenide

The silica sol-gel films with copper selenide produced by the selenization of metallic copper nanoparticles were fabricated. The composition of the films was studied with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and optical absorption spectroscopy. Several copper selenide phases were detected with XRD and contribute into the complicated behavior of core levels (Cu2p, Se3d, and Si2p) and Auger levels (Cu) in the XPS analysis. The optical absorption features of the films in the visible and near-infra red range are presented. The consistent interpretation of experimental data is proposed based on assumption of copper multivalence in the system “particles-silica matrix”.     

溶胶凝胶法制备闪耀光栅及特性研究

采用一步催化法，制备ZrO2光敏溶胶，用提拉法形成了单层光敏凝胶膜。采用紫外光刻技术，将掩摸图形转移到光敏凝胶膜上，通过曝光角度的控制，实现具有一定倾角的闪耀光栅制备，以紫外分光光度计，红外分光光度计，原子力显微镜等方法对光敏凝胶膜及光栅图形进行了性能测试及表征。并用355nm激光系统进行衍射效率及激光损伤阈值测定。获得了周期为2μm，高度为60nm，闪耀角为3°的闪耀光栅。     

Control of optical properties of silica glass synthesized by VAD method for photonic components

High-purity silica glass (SiO₂) synthesized by vapor-phase methods has been extensively used as optical material for photolithography due to its high transmittance in the UV range. Furthermore, low birefringence is an essential property in order to attain distortion-free images of fine IC patterns. This research reports the development of low birefringence silica glass for photonic components that excludes the annealing requirement by controlling the processing parameters of the VAD (Vapor-phase Axial Deposition) method. Nanoparticles size radial homogeneity of silica soot boules was characterized by scanning electron microscopy (SEM). It was established a relationship with the birefringence of consolidated boules characterized through polarization spectrophotometry. As the most interesting results, low birefringence silica glass (? 2 nm/cm) was synthesized with reduced fabrication time and cost besides simple processing stages by controlling the silica boule bottom shape during deposition processing in correlation with the consolidation time.     

溶胶-凝胶法制备锂铝硅微晶玻璃

Li2O-Al2O3-SiO2（LAS）系统微晶玻璃是微晶玻璃中的一个重要分支。这种微晶玻璃的主要性能是低膨胀，耐热冲击性，其应用非常广泛。从原料角度总结了制备锂铝硅微晶玻璃的溶胶-凝胶方法，并对各种方法的特点进行了简要的评述，提出了研究中存在的问题及其今后的发展方向。     

溶胶-凝胶法制备N-卤素共掺杂TiO_2可见光催化材料

为满足低温制备N掺杂TiO2可见光催化材料的需要,采用溶胶-凝胶法,以十六烷基三甲基氯(溴、碘)化铵为掺杂剂,在回流条件下与TiO2纳米晶溶胶直接反应,制备TiO2光催化材料T5100-C、T5100-B、T5100-I。通过XPS分析,只有样品T5100B成功地在TiO2晶格中掺入了N、Br。UV-Vis漫反射吸收光谱和亚甲基兰(MB)的可见光降解实验表明,样品T5100-B具有良好的可见光响应和光催化活性;而样品T5100-C和T5100-I没有明显的可见光响应和可见光催化活性。N的掺杂使得样品T5100-B具有明显的可见光吸收,而Br的掺杂可以阻止光生电子/空穴对的复合,二者共同提高可见光催化活性。     

Role of dopant cations in the gelation behaviour of silica sols

Gelation times of tetraethyl orthosilicate-derived sols containing selected di- to tetravalent cations as dopants were noted at different temperatures (15°–50°C). An analysis of these data, in conjunction with relevant published information, led to the tentative conclusions that (i) unhydrolyzed cations in bare form linked negatively charged silicate polymers in sols, thereby accelerating gelation and (ii) hydrolyzed cations retarded the process by offering molecular size-related hindrance and competition for the available water for hydrolysis.     

Fabrication of transparent silica glass by powder sintering

Transparent silica glasses were obtained by sintering a green compact (fabricated by slip-casting methods for high-purity silica glass powder) in diverse atmospheres. The relationships between sintering atmosphere and sintering temperature that result in transparent, sintered silica glass were shown. The results indicate that there are four forming phases for each sintering atmosphere and temperature: (1) nontransparent glass resulting from an overabundance of pores (2) crystal, such as cristobalite or β-quartz, (3) moganite, and (4) transparent glass. Optimum sintering temperature for fabricating transparent silica glass was above 1673 K in a high-vacuum (10⁻⁴ Pa: p(O₂)=10⁻¹⁴) atmosphere. We investigate the fabrication of transparent and hydroxyl-free silica glass by a powder-sintered method. After studying the effect of sintering schedule on residual [OH⁻] concentration for transparent, sintered silica glasses, we sintered a green compact prepared by silica powders with a mean particle size of 1.6 μm, first heating it to 1523 K for dehydration and then to 1873 K for densification. This typical fabricated condition resulted in a transparent, sintered silica glass with <1 ppm [OH⁻] concentration.     

Fabrication of transparent silica glass by powder sintering

Transparent silica glasses were obtained by sintering a green compact (fabricated by slip-casting methods for high-purity silica glass powder) in diverse atmospheres. The relationships between sintering atmosphere and sintering temperature that result in transparent, sintered silica glass were shown. The results indicate that there are four forming phases for each sintering atmosphere and temperature: (1) nontransparent glass resulting from an overabundance of pores (2) crystal, such as cristobalite or β-quartz, (3) moganite, and (4) transparent glass. Optimum sintering temperature for fabricating transparent silica glass was above 1673 K in a high-vacuum (10^–4 Pa: p(O₂) = 10^–14) atmosphere. We investigate the fabrication of transparent and hydroxyl-free silica glass by a powder-sintered method. After studying the effect of sintering schedule on residual [OH^–] concentration for transparent, sintered silica glasses, we sintered a green compact prepared by silica powders with a mean particle size of 1.6 µm, first heating it to 1523 K for dehydration and then to 1873 K for densification. This typical fabricated condition resulted in a transparent, sintered silica glass with <1 ppm [OH^–] concentration.     

Sol-gel生物活性玻璃体外矿化沉积的动态/静态体外模拟系统对比研究

采用溶胶-凝胶法制备了CaO-P2O3-SiO2系统生物活性玻璃粉体,并通过成型烧结工艺制成多孔材料,对比研究了样品在动态和静态2种体外模拟实验系统中的材料矿化沉积,通过测量溶液pH值,Ca^2 浓度,及样品的XRD、SEM、FTIR测试,证明了动态体外模拟系统可以更好地模拟体内环境,生物活性玻璃材料在2种模拟系统中表面都有碳酸羟基磷灰石生成。     

Nanoparticles embedded into glass matrices: glass nanocomposites

Research on glass nanocomposites (GNCs) has been very active in the past decades. GNCs have attracted — and still do — great interest in the fields of optoelectronics, photonics, sensing, electrochemistry, catalysis, biomedicine, and art. In this review, the potential applications of GNCs in these fields are briefly described to show the reader the possibilities of these materials. The most important synthesis methods of GNCs (melt-quenching, sol-gel, ion implantation, ion-exchange, staining process, spark plasma sintering, radio frequency sputtering, spray pyrolysis, and chemical vapor deposition techniques) are extensively explained. The major aim of this review is to systematize our knowledge about the synthesis of GNCs and to explore the mechanisms of formation and growth of NPs within glass matrices. The size-controlled preparation of NPs within glass matrices, which remains a challenge, is essential for advanced applications. Therefore, a thorough understanding of GNC synthesis techniques is expected to facilitate the preparation of innovative GNCs.     

不同形态石英玻璃的析晶动力学研究

应用XRD技术对三种形态（块状,粉末和纤维）石英玻璃在1200－1500℃范围内内的等温析动力学过程进行了实验研究,实验结果表明,不同形态石英玻璃的析晶产物都是低温方石英,但形态不同的石英玻璃的析昌开始温度,同一温度下的析昌量及析晶量随温度的变化关系是不同的,三种形态石英玻璃析晶动力学可较好地用Avrami方程表示,其中块状,粉末和纤维的平均n值分别为1.65,1.68和1.92,活化能分klj o 495,445和430kJ/mol,析晶中的成核为表面成核机制,晶体生长受扩散和重排双重控制,随比表面和杂质含量的增大（块状→粉末→纤维）,控制因素中扩散的比例降代,而重排的比例上升,因而n值上升而活化能下降,析晶倾向增大。     

Temperature dependent microstructure of MTES modified hydrophobic silica aerogels

Hydrophobic silica aerogels were prepared using a single step sol-gel process followed by ethanol supercritical drying. Using tetraethoxysilane (TEOS) as a precursor and ammonium hydroxide as a catalyst the aerogel surface was chemically modified with methyltriethoxysilane (MTES). A MTES/TEOS molar ratio of 0.5 (M5) was used. The microstructure of the surface modified aerogels was evaluated as a function of heat treatment temperature over a range of 200-500 °C. The thermal stability was analyzed by simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC) and the microstructure was evaluated by physisorption analysis (BET) and scanning electron microscopy (SEM). The chemical composition and hydrophobicity/hydrophilicity of the aerogels were investigated by Fourier Transform-Infrared (FT-IR) spectroscopy. The M5 aerogels, which were initially hydrophobic, exhibited partial hydrophilicity at treatments above 244.5 °C and complete hydrophilicity above 429.9 °C. The surface area of the aerogels ranged from 776.65-850.20 m²/g. Pore size increased after heat treatment, ranging from 16.25 to 18.52 nm vs. an initial pore size of 14.71 nm. The maximum pore size of 18.52 nm was found at the lowest heat treatment temperature (~ 200 °C). Heat treatment had a mixed effect on the pore volume, as pore volumes decreased at lower treatments (~ 200-400 °C) and increased at higher heat treatments (~ 450-500 °C) relative to the untreated aerogels. With initial heat treatment the Si-CH₃ group began to oxidize to Si-OH. Aerogels heated above 429.9 °C exhibited hydroxyl polymerization leading to aerogels with large particles and a dense microstructure.     

溶胶-凝胶法制备纳米块状玻璃的防开裂研究进展

介绍了溶胶-凝胶法的基本原理、工艺流程以及溶胶-凝胶法的特点;探讨了水含量、水解反应温度、烧结温度、干燥控制化学添加剂(DCCA)、溶荆类型、加热方式以及热处理环境和催化剂等影响开裂的因素,并在充分考虑以上因素的前提下,制备出了块状的无开裂纳米CeO2掺杂的纳米玻璃,所制备的块状玻璃具有一定的尺寸,无开裂且均匀透明.最后对溶胶-凝胶法的未来发展进行了展望.     

Cu nanoparticle preparation in a tube-in-tube microchannel reactor and encapsulation by silica

An approach to fabricate Cu@SiO₂ nanostructured materials was presented by using Cu nanoparticles (NPs) produced in a tube-in-tube microchannel reactor (TMR) as the core. Due to the excellent micromixing efficiency of the TMR, monodisperse Cu NPs of sub-5 nm were easily obtained. A combination of the direct silica-coating technique with the remarkable ability of the TMR for mass production of nanoparticles may open an economic pathway for producing core-shell nanomaterials.     

溶胶-凝胶生物活性玻璃超细粉体的制备与生物矿化性能研究

通过溶胶-凝胶和湿法研磨工艺制备了粒径分布在1μm以下的生物活性玻璃超细粉体. 采用XRD、FTIR、SEM测试方法对研磨前后粉体在模拟生理溶液(SBF)中的生物矿化性能进行了对比分析与表征, 结果表明: 在SBF中两种粉体表面都生成了碳酸羟基磷灰石(HCA), 并且经湿法研磨后的溶胶-凝胶生物活性玻璃超细粉体的生物矿化速度显著提高. 通过对不同浸泡时间SBF溶液的pH值测定可知, 在同样反应时间情况下, 超细粉体浸泡液的pH值低于研磨前颗粒. 浸泡液的ICP测试也表明研磨前后玻璃样品的离子溶出规律有所不同.     

纳米生物活性玻璃颗粒的制备及形态控制

采用溶胶-凝胶技术制备纳米生物活性玻璃颗粒, 通过在溶胶中加入柠檬酸来控制生物活性玻璃的形态结构。利用比表面积分析仪、 透射电子显微镜和扫描电子显微镜对纳米生物活性玻璃的结构和形成机制进行了表征。研究结果表明:采用柠檬酸作为水解催化剂可以方便地控制生物活性玻璃的纳米结构形态, 有利于制备较小粒径、 大比表面积和孔体积的生物活性玻璃。这种制备技术提供了一种简单、 低成本制备纳米生物活性玻璃并控制其纳米粒子形态的方法。      

Self-assembled natural rubber/silica nanocomposites: Its preparation and characterization

A novel natural rubber/silica (NR/SiO₂) nanocomposite is developed by combining self-assembly and latex-compounding techniques. The results show that the SiO₂ nanoparticles are homogenously distributed throughout NR matrix as nano-clusters with an average size ranged from 60 to 150 nm when the SiO₂ loading is less than 6.5 wt%. At low SiO₂ contents (4.0 wt%), the NR latex (NRL) and SiO₂ particles are assembled as a core-shell structure by employing poly (diallyldimethylammonium chloride) (PDDA) as an inter-medium, and only primary aggregations of SiO₂ are observed. When more SiO₂ is loaded, secondary aggregations of SiO₂ nanoparticles are gradually generated, and the size of SiO₂ cluster dramatically increases. The thermal/thermooxidative resistance and mechanical properties of NR/SiO₂ nanocomposites are compared to the NR host. The nanocomposites, particularly when the SiO₂ nanoparticles are uniformly dispersed, possess significantly enhanced thermal resistance and mechanical properties, which are strongly depended on the morphology of nanocomposites. The NR/SiO₂ has great potential to manufacture medical protective products with high performances.     

多功能单层二氧化硅增透膜的设计与制备

通过膜层设计软件(TFCalcTM)设计了在400~1 100nm波长范围内具有高透过率的单层增透膜。以正硅酸乙酯(TEOS)和甲基三乙氧基硅烷(MTES)为共混前驱体、盐酸为催化剂、十六烷基三甲基溴化铵(CTAB)为模板剂制得甲基修饰的二氧化硅溶胶,通过浸渍提拉法结合溶剂挥发自组装技术成功制备了所设计的多功能单层增透膜。结果表明,(1)增透膜在650nm的最大透过率可达到99.9%,在400~1 100 nm波长范围内的光伏透过率(TPV)高达98.7%,与软件设计结果一致;(2)TEOS与MTES共聚后,显著提高增透膜的疏水性,其对水的接触角从24°提高至85°;(3)单层二氧化硅增透膜具有较好的耐磨擦性。这种兼具高透过率、耐磨擦性和一定疏水性的多功能增透膜在太阳能电池领域具有应用价值。