SiO2-Na2O-CaO-P2O5-Fe2O3铁磁微晶玻璃的制备与性能研究

铁磁性微晶玻璃由于具有磁性和生物活性,可以用作磁感应热疗的热种子材料.采用SiO2-Na2O-CaO-P2O5-Fe2O3五元系统,通过共沉淀-熔融法和熔融法两种不同的方法制备铁磁性微晶玻璃,利用XRD确定其晶相并计算晶体的晶格常数和晶粒尺寸,并通过VSM表征样品的磁性能.结果表明,玻璃液在自然冷却的过程中就形成了大量的磁铁矿,不经过热处理过程即可制得具有磁铁矿唯一晶相的铁磁性微晶玻璃并具有生物活性.共沉淀-熔融法制备的样品磁性更强.     

不同炭化温度制备的C/0.5Al2O3-0.5P2O5-100SiO2凝胶玻璃的光学性质

通过醇盐不完全水解制备了含有有机基团(O-C₂H₅)的0.5Al₂O₃-0.5P₂O₅-100SiO₂凝胶,在氮气中加热到300～700℃使其中的有机基团炭化,得到镶嵌在凝胶玻璃中不同尺寸的碳纳米颗粒.利用高分辨电镜、X射线衍射和喇曼光谱研究了碳纳米颗粒的结构,发现凝胶玻璃中的碳颗粒为非晶碳纳米颗粒.测试了它们的吸收光谱,发现了由于量子限域效应引起的吸收边的移动.在532um Nd:YAG激光的激发下镶嵌有碳纳米颗粒的凝胶玻璃有一强的室温发光,发光峰在586um左右.发光峰几乎不随碳纳米颗粒尺寸的变化而变化.这种发光产生于碳纳米颗粒的表面或碳颗粒和凝胶网络的界面.     

中空纤维担载Al_2O_3-SiO_2复合膜的研制

采用溶胶-凝胶法在α-Al2O3中空纤维载体上制备了Al2O3-SiO2复合膜,并对复合膜的制备条件及稳定性进行了研究.利用SEM和EDS对复合膜的微观形貌及化学组成进行了分析.结果表明,所制备的担载复合膜表面完整、无缺陷.气体渗透实验进一步说明,复合膜具有一定的气体选择性,在0.1 MPa下对H2/N2的分离因子为3.03,表明气体通过膜的扩散以Knuen扩散传质为主.用等温氮气吸附实验测定了非担载膜的孔径大小和分布,其比表面积为294.85 m2/g,总孔容为0.28 mL/g,最可几孔径小于3 nm.     

中空纤维担载Al2O3-SiO2复合膜的研制

采用溶胶-凝胶法在α-Al2O3中空纤维载体上制备了Al2O3-SiO2复合膜,并对复合膜的制备条件及稳定性进行了研究.利用SEM和EDS对复合膜的微观形貌及化学组成进行了分析.结果表明,所制备的担载复合膜表面完整、无缺陷.气体渗透实验进一步说明,复合膜具有一定的气体选择性,在0.1 MPa下对H2/N2的分离因子为3.03,表明气体通过膜的扩散以Knuen扩散传质为主.用等温氮气吸附实验测定了非担载膜的孔径大小和分布,其比表面积为294.85 m2/g,总孔容为0.28 mL/g,最可几孔径小于3 nm.     

Preparation and magnetic properties of SiO2-CaONa2O-P2O5-FeO-Fe2O3glass-ceramics prepared by gel-melt method

The SiO2-CaO-Na2O-P205-FeO-Fe2O3 precursors were prepared by the sol-gel method.And then two different ways were used to obtain the ferrimagnetjc glass-ceramics,j.e.,one is compression-sintering method.and the other is melt-quenching-heat treatment.The crystalline type and size of the magnetite were analyzed by XRD patterns.and the magnetism of samples were characterized by VSM.This kind of glass-ceramics shows a bioactive behavior after soaked in the Simufated body fluid test for two weeks.     

Sol-gel fabrication and photoluminescence properties of SiO2 @ Gd2O3:Eu3+ core-shell particles

A uniform nanolayer of europium-doped Gd2O3 was coated on the surface of preformed submicron silica spheres by a Pechini sol-gel process. The resulted SiO2 @ Gd2O3:Eu3+ core-shell structured phosphors were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), photoluminescence (PL) spectra as well as kinetic decays. The XRD results show that the Gd2O3:Eu3+ layers start to crystallize on the SiO2 spheres after annealing at 400 degrees C and the crystallinity increases with raising the annealing temperature. The core-shell phosphors possess perfect spherical shape with narrow size distribution (average size: 640 nm) and non-agglomeration. The thickness of the Gd2O3:Eu3+ shells on the SiO2 cores can be adjusted by changing the deposition cycles (70 nm for three deposition cycles). Under short UV excitation, the obtained SiO2@Gd2O3:Eu3+ particles show a strong red emission with 5D0-7F2 (610 nm) of Eu3+ as the most prominent group. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles.     

SiO2-Al2O3-MgO-K2O-(F,Cr2O3)玻璃陶瓷的析晶

为了研究形核剂氟化物、氧化铬及其复合作用对SiO2-Al2O3-MgO-K2O系玻璃陶瓷形核和析晶的影响,采用高温熔融法制备了不同氟化物和氧化铬含量的基础玻璃,并对该基础玻璃进行了差热分析、显微分析和X射线衍射分析.结果表明:在所研究的玻璃体系中,氟化物或氧化铬的加入,都不同程度地削弱了玻璃体的结构,降低了玻璃的转变温度;当基础玻璃只含有氟化物时,玻璃在表面析出云母晶体,内部发生分相现象,而玻璃中仅含有氧化铬时,玻璃中发生整体析晶;没有氟化物的存在,不能析出云母晶体;当同时加入两种元素的物质后,对玻璃体析晶的影响不是简单的加合,复合的作用更为突出,进一步降低了玻璃的转变温度和析晶温度,整体均匀析出云母晶体.     

氧化锡纳米粉的制备与发光性质的研究

利用溶胶凝胶法制备了粒径3.0～8.8nm的氧化锡纳米粉,并通过掺杂稀土离子铈研究了氧缺陷引起的氧化锡纳米粉的发光性质,发现当引入了掺杂离子后可以大大增强其发光强度,并对其发光机理进行了讨论.     

Microstructural and electrical characteristics of SiO2 doped ZnO-Bi2O3 varistors

Varistors in the new system ZnO-Bi₂O₃-SiO₂ were prepared through conventional ceramic processing route. The effect of sintering temperature and time (0·5 h to 2 h between 1000° and 1250°C) on the microstructure and current/voltage characteristics of the varistors of the new system were investigated and the results were compared with those of ZnO-Bi₂O₃ system varistors prepared. An increase in nonlinear coefficient (α) value was observed in the SiO₂ added varistors. The microstructure and the phase of the varistors were examined by means of SEM and XRD. The Zn₂SiO₄ spinel phase was found to be present in the intergranular region. The grain growth exponent was determined to be 2·5±0·2 and the activation energy for the ZnO grain growth was estimated to be 251±11 kJ/mol. These values were compared with those estimated for ZnO-Bi₂O₃ system varistors.     

纳米Al2O3与SiO2的制备及在陶瓷釉料中的应用

以普通无机盐为原料采用沉淀法制备了纳米Al2O3和SiO2.XRD分析表明样品为无定形结构,SEM分析表明得到的纳米Al2O3和SiO2均为球形颗粒,直径分别为90m和300nm.将合成的纳米材料添加至陶瓷面釉进行烧结测试,结果表明,添加纳米材料釉料的烧结温度比普通釉料的烧结温度降低了30℃,釉层性能明显得到改善,釉料良好的性能源于纳米材料较大的表面积及高的烧结活性.     

不同形态SiO2改性钙硅硼系微晶玻璃结构与性能

分别研究了高硅氧玻璃(96wt%SiO2,非晶态)与二氧化硅(99wt%,石英相)的添加对CaO-SiO2-B2O3(CSB)微晶玻璃微观结构、烧结性能以及介电性能的影响.结果表明:不同形态SiO2的添加均可以有效地降低介电常数,同时高硅氧玻璃的引入增加了试样的介电损耗.添加15wt%SiO2、850℃低温烧结试样,在10MHz下,介电常数为6.01,介电损耗1.2 × 10-3,且在5～40MHz频率范围内,介电常数随频率的变化不大.烧结试样的主要晶相为Quartz、CaSiO3和CaB2O4.     

Nonvolatile memory characteristics of WSi2 nanocrystals embedded in SiO2 dielectrics

A nano-floating gate capacitor with WSi2 nanocrystals embedded in SiO2 dielectrics was fabricated. The WSi2 nanocrystals were created from ultrathin WSi2 film during rapid thermal annealing process and their average size and density were about 2.5 nm and 3.59 x 10(12) cm(-2), respectively. The flat-band voltage shift due to the carrier charging effect of WSi2 nanocrystals were measured up to 5.9 V when the gate voltage sweep in the range of +/- 9 V. The memory window was decreased from 3.7 V to 1.9 V after 1 h and remained about 3.7 V after 10(5) programming/erasing cycles. These results show that there is a possibility for the WSi2 nanocrystals to be applied to nonvolatile memory devices.     

Glass transition temperature of glasses in the SiO2-Na2O-CaO-P2O5-Al2O3-B2O3 system

A total of 24 glasses in or near the bioactive region in the system SiO₂-Na₂O-CaO-P₂O₅-Al₂O₃-B₂O₃ were studied. By differential thermal analysis their glass transition temperatures,T _g, were determined. On basis of an experimental plan for 16 glasses, two phenomenological equations describing the relationship betweenT _g and glass composition were developed. The equations describeT _g within the compositional ranges: SiO₂, 38.0–65.5 Na₂O, 15.0–30.0; CaO, 10.0–25.0; P₂O₅, 0–8.0; B₂O₃, 0–3.0; Al₂O₃, 0–3.0 wt%. The glass transition temperature shows a linear dependence of the Na₂O content. The higher the Na₂O content, the lower theT _g. Compositional alterations not including Na₂O influencesT _g little in comparison with changes in the Na₂O content.     

In vivo behaviour of glasses in the SiO2-Na2O-CaO-P2O5-Al2O3-B2O3 system

Sixteen glasses in the SiO₂-Na₂O-CaO-P₂O₅-Al₂O₃-B₂O₃ system were studied. The glasses were implanted in rabbit tibia. According to theirin vivo behaviour, they were divided into five groups. A phenomenological equation for thein vivo behaviour was developed. The solubility of the glasses was determinedin vitro as weight loss in Tris buffer solution. The tissue response is discussed in relation to the glass composition and the solubility. For bone-bonding glasses calcium phosphate formation takes place within a silica-gel at the glass surface. The gel must be sufficiently hydrated and flexible to allow calcium phosphate to build up. The results suggest that alumina can inhibit bone bonding by retarding the formation rate of a silica-rich layer, by stabilizing the silica structure enough to prevent calcium phosphate build-up within the layer, or by either disturbance of the bone mineralization or bone incompatibility of an alumina-containing calcium- and phosphorus-rich surface layer. The mechanism responsible for the lack of bone adherence is determined by the glass composition. Up to about 1.5 wt % Al₂O₃ can be included in the glass without destroying the bioactivity.     

V2O5含量对SiO2-MgO-Al2O3-K2O-V2O5-F系玻璃陶瓷析晶的影响

应用扫描电子显微镜(SEM)、X射线衍射(XRD)及电子探针(EPMA)等技术研究了V2O5含量对SiO2-MgO-Al2O3-K2O-V2O5-F玻璃陶瓷析晶的影响.结果表明,在所研究的玻璃体系中,V2O5的加入促进了莫来石晶体在较低温度下的析出,而且随着玻璃中V2O5含量的提高,莫来石和云母晶体的析晶温度区间逐渐向低温方向移动.EPMA结果显示在析出的晶体中没有钒元素的聚集,表明V2O5的加入没有参与晶体的直接形核,而是以网络外体的形式存在于玻璃体系中,削弱玻璃的结构,导致晶体析出温度降低.同时发现VO含量尽管对析出晶体的种类没有明显的影响,但是对晶体的形态、大小及数量的影响较为显著.     

Preparation and characterization of DLC/SiO2/Al2O3 nanofiltration membrane

High quality ceramic thin films were fabricated by thin film deposition process in semiconductor field in order to fabricate high performance carbon/SiO ₂ /Al ₂ O₃ membrane. α-Al ₂ O ₃ substrate was used as a supporting material. A severe thermal stress and rough surface for active ceramic top layer such as zeolite were observed. To overcome thermal stress, intermediate layer of SiO₂ and diamond-like carbon (DLC) thin film were used. SiO ₂ and DLC thin films on porous alumina support were deposited using plasma-enhanced chemical vapour deposition (PECVD). Homogeneous and smooth surfaces and interfaces of DLC/SiO ₂ /Al ₂ O ₃ membrane were observed by FESEM. The phases of DLC and SiO ₂ thin films were identified by X-ray diffraction pattern. Gas permeabilities of the nanofiltration membrane with DLC/SiO ₂ /Al ₂ O ₃ were observed at various annealing temperatures. Mixed gas permeability of the membrane with 1 μm-thick SiO₂ and 2 μm-thick DLC thin film annealed at 200 °C was ～18 ccm at 1018 mb back pressure.     

The effect of additives on the crystallization and sintering of 2MgO-2Al2O3-5SiO2 glass-ceramics

Crystallization and sintering behaviour of three cordierite (2MgO-2Al₂O₃-5SiO₂) glasses containing different amount of additives were investigated and compared by using differential thermal analysis (DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), and the Archimedes method. The stoichiometric 2MgO-2Al₂O₃-5SiO₂ (MAS) glass and the 2MgO-2Al₂O₃-5SiO₂ glass containing 3 wt% of B₂O₃ and 3 wt% of P₂O₅ (MASBP) showed two exotherms (one for -cordierite formation from a glass and the other for -cordierite formation from the -cordierite phase), whereas the 2MgO-2Al₂O₃-5SiO₂ glass containing 2 wt % of B₂O₃, 2 wt% of P₂O₅, and 2 wt % of TiO₂ (MASBPT) showed only a single exotherm representing -cordierite formation. By using Kissinger, Augis-Bennett, Ozawa, and modified Kissinger methods, the activation energy values for -cordierite formation in the MASBP and MASBPT glasses were determined as 310±6 and 326±13 kJ mol^–1, respectively, whereas that in the MAS glass was determined as 868±5 kJ mol^–1. The MASBPT glass showed the lowest peak temperature value for -cordierite formation (980 °C) amongst the three glasses. Both the MASBP and MASBPT glasses showed excellent sintering behaviour (> 99.7% of theoretical density).     

Preparation and characterization of binary V2O5-Bi2O3 glasses

Characterization of the binary V₂O₅-Bi₂O₃ glasses prepared by rapidly quenching the melt has been made from the studies of X-ray diffraction, scanning electron microscopy, infrared absorption, differential thermal analysis, electron paramagnetic resonance, chemical analysis, density and electrical properties. Stable glasses are obtained for 95 to 75 mol % V₂O₅ by quenching on a stainless steel substrate, while quenching on a copper substrate extends the glass formation range from 95 to 70 mol % V₂O₅. The V-O bond vibration in the glasses occurs at 1020 cm^–1 and the V^5% ion exists in six-fold coordination as in crystalline V₂O₅. All the glasses appear to be in single phase. The spin concentration in the glasses is found to be independent of temperature. A second heat-treatment at 255° C develops crystalline phase in the glasses. Unlike infrared absorption, electron paramagnetic resonance, density and chemical compositions, the electrical and thermal (DTA) properties are found to be slightly sensitive to the thermal history of preparation of the glasses. The high-temperature (300 to 500 K) conduction in the glasses seems to be due to adiabatic hopping of polarons. The thermopower is observed to be independent of temperature and provides evidence for small polaron formation in the glasses.