煅烧条件对纳米TiO2/膨胀珍珠岩复合材料性能的影响

以膨胀珍珠岩为载体,TiOSO4为钛源,采用均匀沉淀法制备了纳米TiO2/膨胀珍珠岩复合材料,通过XRD、SEM和FT-IR对复合材料的TiO2晶体结构、表面性质和形貌进行分析表征.研究了煅烧温度和煅烧时间对复合材料中TiO2结晶和光催化性能的影响.结果显示在550℃下煅烧2h时,复合材料的光催化性能最高,此时TiO2为锐钛矿,晶粒尺寸为11.93 nm,对罗丹明溶液的降解率达到95;以上.复合材料具有良好的再生重复使用性能,经5次回收再利用后仍表现较高的光催化性能.     

均匀沉淀法制备纳米TiO2/膨胀珍珠岩复合材料

以膨胀珍珠岩为载体,TiOSO4为钛源,采用均匀沉淀法制备了纳米TiO2/膨胀珍珠岩复合材料,通过SEM、TEM、XRD和BET比表面积法进行了分析表征,并以罗丹明B溶液为降解对象研究其光催化性能.结果表明随着TiOSO4加入量的增加,复合材料的TiO2负载量和比表面积越来越大,而光催化性能先升高后降低.当TiO2负载量为15.27;时光催化性能最好,此时纳米TiO2颗粒在膨胀珍珠岩表面均匀致密分布成一层薄膜,TiO2晶粒尺寸为11.93nm,经300 W高压汞灯照射60 min时对罗丹明B溶液的降解率超过95;,达到了与P25相同的降解效果.     

硅藻土/TiO2/氧化石墨烯复合材料的制备及其光催化性能研究

本文以硅藻土为载体,硫酸氧钛为前驱体,在硅藻土表面原位水解形成二氧化钛纳米颗粒,后经氧化石墨烯修饰改性,得到硅藻土/TiO2/氧化石墨烯三元复合光催化材料.通过SEM、XRD、XPS、IR对样品的晶体结构、形貌及元素形态等进行了表征,研究了复合催化剂对罗丹明B溶液的光催化降解性能.结果表明,硅藻土/TiO2/氧化石墨烯三元复合材料在2 h的光降解率高达99;,比同时间的硅藻土/TiO2二元复合材料高出10;,比硅藻土高出73;,硅藻土作为载体有效的避免了二氧化钛颗粒的团聚,同时氧化石墨烯的高导电性能有效分离光生载流子,从而提高TiO2的光催化活性和反应效率.     

α-Fe2O3/TiO2光催化剂的制备及可见光催化降解罗丹明B的研究

采用浸渍法制备不同掺杂量的负载型光催化剂 α-Fe2O3/TiO2,通过XRD、SEM-EDX、XPS和N2-sorption等手段对其进行表征,并研究其在可见光照射下对罗丹明B的降解性能.考察了不同掺杂量的复合纳米粒子、不同浓度的H2O2溶液、不同pH等条件对可见光降解罗丹明B的影响.结果表明,复合α-Fe2O3/TiO2催化剂的光催化活性均高于单一的α-Fe2O3或TiO2,其中α-Fe2O3掺杂量为6.0wt;的α-Fe2O3/TiO2的光催化活性和光降解稳定性最好.     

TiO2/α-Fe2O3和TiO2/叶FeOOH纳米复合材料的制备与表征

以TiCl4为前驱体,α- Fe2O3、α-FeOOH为载体,采用水解沉淀法制备TiO2/α-Fe2O3和TiO2/α-FeOOH两种纳米复合光催化材料.采用X射线衍射分析(XRD)和透射电子显微镜(TEM)等对样品的晶相组成、形貌和微结构进行表征.结果表明,TiO2/α-Fe2O3复合材料由赤铁矿和金红石相TiO2组成;TiO2/α-FeOOH复合材料由水合氧化铁和金红石相TiO2组成.TiO2/α-Fe2O3复合材料中颗粒状TiO2能包覆在粒状氧化铁红表面,形成厚度范围在5～20 nm左右的薄层;TiO2/α-FeOOH复合材料是一种核壳结构,厚度范围在100～150 nm的针状TiO2聚集体为壳,能完整的包覆核层氧化铁黄.采用UV-vis光谱和甲基橙降解对其光催化活性进行评价,结果表明纳米TiO2与α-Fe2O3、α-FeOOH分别构成复合材料后,两者之间存在协同效应.     

纳米TiO2/蛋白土复合材料的制备与表征

为了解决纳米TiO2在使用过程中分散性差、难以回收等缺点,将纳米TiO2负载在酸浸蛋白土表面,提高光催化效率.以酸浸蛋白土为载体,TiCl4为前驱体,采用水解沉淀法制备了纳米TiO2/蛋白土复合材料.采用XRD、TEM等方法对复合材料性能进行了表征,并进行了复合材料的光催化降解甲醛实验研究.结果表明负载在蛋白土表面的Ti02晶型为锐钛型,晶粒粒度为5～20 nm.对甲醛降解实验研究结果表明,所制备的蛋白土负载纳米TiO2复合材料具有良好的光催化降解性能,其24h对甲醛的降解去除率可以达到90;以上.     

炭黑吸附水热法制备纳米TiO2粉体及其光催化降解甲基橙

利用炭黑吸附钛酸异丙酯水热法制得锐钛矿型TiO2纳米粉体.采用热重/差热分析(TG-DTA)、X-射线衍射(XRD)、扫描电镜(SEM)、比表面积吸附(BET)和紫外-可见光谱(Uv-vIS)等分析方法对不同煅烧机制下所得粉体的物相、颗粒度、分散性和光吸收性能进行表征.同时利用纳米TiO2粉体对甲基橙进行了光催化降解,研究了其光催化性能.结果表明,炭黑的吸附阻止了纳米TiO2超细颗粒的团聚和烧结,制得的颗粒分散均匀、具有单一锐钛矿晶型结构的TiO2纳米粉体.经500℃煅烧获得的TiO2粉体粒径约为15 nm,比表面积为76.31 g/m2.在紫外灯照射下,由于炭黑的吸附和纳米TiO2的光催化形成协同效应,甲基橙的光催化降解率在6min达到99;.     

Ag3PO4/TiO2复合催化剂的制备及光催化性能研究

为提高纳米TiO2的光催化降解性能和稳定性,采用两步水热法制备具有高催化性能的Ag3PO4/TiO2复合催化剂,采用XRD、SEM、EDS、XPS、TEM等仪器对其表面微观形貌和形态大小、表面元素组成、物相结构等进行表征,并研究了TiO2的比表面积和Ag3PO4颗粒尺寸大小对Ag3PO4/TiO2光催化性能的影响.以亚甲基蓝(MB)和苯酚为目标降解物来考察复合光催化剂的光催化性能.结果表明:1h后Ag3PO4、TiO2、Ag3PO4/TiO2对亚甲基蓝的降解率为25;、42;、92;;复合光催化剂Ag3PO4/TiO2经过5次光催化降解实验后,对亚甲基蓝的降解率仍可达78;.     

低温下制备具有高光催化降解罗丹明B活性的CuS/TiO2复合材料

采用元素直接反应法,以Cu粉和S粉作为前驱体,将在氯化胆碱与乙二醇的低共熔溶剂中低温(40℃)下生成的CuS原位浸渍到具有锐钛矿晶相的TiO2载体上,成功制备了CuS/TiO2复合型光催化剂.采用X射线衍射光谱(XRD)、扫描电镜(SEM)、紫外-可见漫反射光谱(UV-vis DRS)和X光电子能谱(XPS)等对CuS/TiO2的晶相结构、颗粒大小、CuS存在状态以及光学性质进行了表征.以染料罗丹明B的降解为探针反应,研究了CuS对TiO2光催化性能的影响.结果表明,CuS的复合没有影响TiO2的晶相结构和粒径,CuS的复合降低了TiO2带隙能,增加了TiO2对可见光的吸收.CuS/TiO2复合材料的光催化活性比CuS或TiO2的光催化活性都高,而且CuS的含量对CuS/TiO2催化剂的光催化活性有明显影响,0.1wt; CuS/TiO2光催化剂表现了最佳的光催化性能.     

棒状PANI/TiO2纳米复合材料的制备及光催化性能研究

通过共混法和原位氧化聚合法成功制备了棒状聚苯胺/TiO2纳米复合材料,通过SEM、XRD、FT-IR、TGA、TEM、紫外-可见漫反射光谱等测试对其进行表征.并以罗丹明B溶液为模拟污染物,在可见光条件下,棒状PANI/TiO2纳米复合材料的催化降解效率与纯PANI和TiO2相比明显提高.另外,对两种不同方法合成的PANI/TiO2纳米复合材料的光催化性能进行对比,结果表明原位氧化聚合法制得的复合材料,由于TiO2在复合材料中的均匀分布及其与PANI的协同效应,光催化降解率可达91.11;.     

Ionic conduction in As2S3---Ag2S, GeS2---GeS---Ag2S and P2S5---Ag2S glasses

The glass-forming region in the system P---S---Ag was determined and density, thermal expansion, dc conductivity and the transport number of Ag ions were measured for P₂S₅---Ag₂S glasses found in the P---S---Ag system. The results for the transport number measurement show that P₂S₅---Ag₂S glasses are purely ionic conductors owing to the Ag ion migration, like most of the As₂S₃---Ag₂S and GeS₂---GeS---Ag₂S glasses reported previously. Glass structure and ionic conduction processes in As₂S₃---Ag₂S, GeS₂---GeS---Ag₂S and P₂S₅---Ag₂S glasses are discussed, based on their ionic conductivity and density data. The structural concept of -Ag₂S was applied to these glasses, which suggests that the Ag ions in the glasses are distributed in the available Ag ion sites in the non-conducting framework composed of both S anions and As, Ge or P cations. In each system the ionic conductivity increases linearly with increasing Ag⁺/total cation (%) in glass composition, the determining factor being the activation energy for ionic conduction alone. Thus, the activation energy in these glasses depends predominantly upon the molar ratio of Ag ions to total cation in the glass, irrespective of the kind of system. Small differences in the activation energy among the three systems can be interpreted as arising from differences in the field strength of As, Ge and P cations.     

Spectroscopic properties of Er-doped Na2O-Sb2O3-B2O3-SiO2 glasses

Spectroscopic properties of Er³⁺-doped Na₂O-Sb₂O₃-B₂O₃-SiO₂ glasses have been investigated for developing 1.5-μm broadband fiber amplifiers. An intense 1.5-μm near infrared emission with a broad full width at half maximum (FWHM) of 88 nm has been obtained for Er³⁺-doped 5Na₂O-20Sb₂O₃-35B₂O₃-40SiO₂ glass upon excitation with a 980 nm laser diode. The obtained emission cross-section of the ⁴I_13/2 → ⁴I_15/2 transition and the lifetime of the ⁴I_13/2 level of Er³⁺ ions are 6.8 × 10⁻²¹ cm² and 0.36 ms, respectively. It is noted that the product of the emission cross-section and the FWHM of the glass, σ_e × FWHM, is as great as 598.4 × 10⁻²¹ cm² nm, which is comparable or higher than that of Er³⁺-doped bismuth-based and tellurite-based glasses. These special optical properties encourage in identifying them as important materials for potential applications in high performance optics and optical communication networks.     

Growth of single crystals of NaH2PO4 (NaDP), NaH2PO4 · H2O (NaDP · H2O), and NaH2PO4 · 2H2O (NaDP · 2H2O) sodium dihydrogenphosphate based on the analysis of the Na2O-P2O5-H2O phase diagram

The crystallization conditions for the NaH₂PO₄, NaH₂PO₄ · H₂O, and NaH₂PO₄ · 2H₂O solid phases have been established from the analysis of the phase diagram of solubility of the ternary Na₂O-P₂O₅-H₂O system in the temperature range from 0 to 100°C. Based on these data, the methods for growing sodium dihydrogenphosphate single crystals of the above compositions are developed. The initial components for preparing mother solutions were H₃PO₄ and NaOH solutions taken in certain weight ratios. For the first time, NaDP, NaDP · H₂O, and NaDP · 2H₂O single crystals were grown on a seed by the method of temperature decrease. The habits of the NaDP and NaDP · H₂O single crystals are determined. __________ Translated from Kristallografiya, Vol. 47, No. 5, 2002, pp. 937–944. Original Russian Text Copyright ? 2002 by Soboleva, Voloshin.     

Thermo-optic properties of B2O3 doped Li2O-Al2O3-SiO2 glass-ceramics

Reduction in the temperature coefficient of the optical path length, dS/dT of Li₂O-Al₂O₃-SiO₂ glass-ceramics with near-zero thermal expansion coefficient was attempted using control of the temperature coefficient of electronic polarizability, ?, and the thermal expansion coefficient, α. The dS/dT value of 2.6 mol% B₂O₃-doped glass-ceramic was 12.5  × 10⁻⁶/°C, which was 0.9 ×  10⁻⁶/°C smaller than that of B₂O₃-free glass-ceramic. On the other hand, reduction in dS/dT through B₂O₃ doping was not confirmed in precursor glasses. Results showed that reduction in dS/dT of the glass-ceramic through B₂O₃ doping is caused by the reduction in ?. The reduction in ? from B₂O₃ doping was probably attributable to numerical reduction in non-bridging oxide ions with larger ? value by the concentration of boron ions in the residual glass phase. In addition, application of hydrostatic pressure during crystallization was effective to inhibit precipitation of β-spodumene solid solution, which thereby decreases dS/dT. The dS/dT value of B₂O₃-doped glass-ceramic crystallized under 196 MPa was 11.7 ×  10⁻⁶/°C. That value was slightly larger than that of silica glass. The α value of this glass-ceramic was smaller than that of silica glass.     

The effect of composition on UV-vis-NIR spectra of iron doped glasses in the systems Na2O/MgO/SiO2 and Na2O/MgO/Al2O3/SiO2

Glasses with the compositions xNa₂O · 10MgO · (90 − x)SiO₂, 10Na₂O · xMgO · (90 − x)SiO₂, 5Na₂O · 15MgO · xAl₂O₃ · (80 − x)SiO₂, xNa₂O · 10MgO · 10Al₂O₃ · (80 − x)SiO₂, 10Na₂O · 10MgO · xAl₂O₃ · (80 − x)SiO₂, 10Na₂O · 5MgO · 10Al₂O₃ · (80 − x)SiO₂ were melted and studied using UV-vis-NIR spectroscopy in the wavenumber range from 5000 to 30 000 cm⁻¹. At [Al₂O₃] > [Na₂O], the UV-cut off is strongly shifted to smaller wavenumbers and the NIR peak at around 10 000 cm⁻¹ attributed to Fe²⁺ in sixfold coordination gets narrower. Furthermore, the intensity of the NIR peak at 5500 cm⁻¹ increases. This is explained by the incorporation of iron in the respective glass structures.     

Electron diffraction RDF analysis of amorphous As2Se3,AAs2Se2Te,As2SeTe2 and As2Te3 films

The local order in amorphous films of As₂Se₃, As₂Se₂Te, As₂SeTe₂, and As₂Te₃ has been examined by scanning electron diffraction with direct recording of the intensity of the elastically scattered electrons. The radial distribution functions indicate that there is a systematic increase in mean nearest neighbor distance as the Te concentration is increased, butthe mean coordination number increases slightly around 2.4. Pair function calculation of models shows that the 3-aand 2-fold coordinations of arsenic and chalcogens are retained in these glasses and the interatomic distances are close to those predicted from the Pauling covalent atomic radii of the constituent atomic species. The short range order appears to be similar in amorphous and crystalline As₂Se₃, but different in the case of As₂Te₃ as found by previous workers on bulk materials.     

Crystallization processes of Li2O-Ga2O3-SiO2-NiO system glasses

Crystallization processes of Li₂O-Ga₂O₃-SiO₂-NiO system glasses have been studied by X-ray diffraction, differential calorimetry and optical absorption. Transparent glass-ceramic containing LiGa₅O₈:Ni²⁺ as the sole crystalline phase has been obtained from glass with the composition of 13Li₂O-23Ga₂O₃-64SiO₂-0.1NiO (in mol%) by the heat treatment in the temperature range from 923 to 953 K. It was revealed that the specific surface area of samples enhances crystallization of LiGaSi₂O₆ but obstructed that of LiGa₅O₈. LiGa₅O₈ grew to nano-sized crystallites dispersed in the glass matrices and did not affect the transparency seriously. In contrast, LiGaSi₂O₆ grew to crystallites with diameters more than 100 nm on the surface and made the glasses opaque. Optical absorption measurements revealed that doped Ni²⁺ occupied five-folded trigonal bipyramidal sites in the as-quenched glass matrices but six-folded octahedral sites of precipitated LiGa₅O₈ in the glass-ceramics. It was confirmed that transparent glass-ceramic containing Ni²⁺:LiGa₅O₈ was effectively obtained by the heat treatment at a temperature of 953 K for 10 h.     

Optical Properties of Bi2O3-TeO2-B2O3 Glasses

Glasses of the Bi₂O₃-TeO₂-B₂O₃ ternary system were developed and their linear and nonlinear optical properties were investigated. The absorption edges of these glasses were found to be 367-384 nm with a good transmittance in visible wavelength, although they exhibit the refractive indices as high as 1.98-2.12 at 633 nm. The absorption edges are quite steep and they are analyzed by the Urbach theory. The obtained Urbach energies of these glasses are 73-79 meV which are comparable to silica glasses. The high refractive index and its glass composition dependency are discussed according to the basics of the electronic polarizability and optical basicity. The high third order nonlinear susceptibility χ⁽³⁾ = 2.0 × 10^− 12 esu at 800 nm was also obtained in the 36Bi₂O₃-18TeO₂-46B₂O₃ glass.     

(Na1/2Bi1/2)TiO3-(Na1/2Bi1/2)(Zn1/3Nb2/3)O3无铅压电陶瓷的介电特性研究

采用固相合成法制备了(1-x)(Na1/2Bi1/2)TiO3-x(Na1/2Bi1/2)(Zn/23Nb2/3)O3(简写为(1-x)NBT-xNBZN)无铅压电陶瓷.研究了该体系陶瓷晶体结构、弥散相变特征与介电弛豫行为.X射线衍射分析表明,所研究的组成均能够形成纯钙钛矿(ABO3)型固溶体.当x≥0.5%摩尔分数时,该体系陶瓷具有三方、四方共存的晶体结构.材料的介电常数-温度曲线显示陶瓷具有两个介电反常峰Tf和Tm.修正的居里-外斯公式较好的描述了陶瓷弥散相变特征,弥散指数随x的增加而增加.x≤0.5%摩尔分数的陶瓷仅在低温介电反常峰Tf附近表现出明显的频率依赖性,随x的增加,陶瓷材料在室温和低温介电反常峰Tf之间都表现出明显的频率依赖性.根据有序-无序转变和宏畴.微畴转变理论探讨了该体系陶瓷介电弛豫特性的机理.     

Characterization of chemosynthetic Al2O3-2SiO2 geopolymers

Pure chemosynthetic Al₂O₃-2SiO₂ geoploymers displaying positive alkali-activated polymerization properties and high compressive strength at room temperature were effectively fabricated utilizing a sol-gel method. The molecular structure of the precursor powder and resulting geopolymers were investigated by X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) analysis. In addition, the mechanical and alkali-activated polymerization properties of these materials were also studied. NMR data revealed that the chemosynthetic powders began to contain 5-coordinated Al atoms when the calcination temperatures exceeded 200 °C. These calcined powders were capable of reacting with sodium silicate solutions at calcination temperatures exceeding 300 °C, which is, however, much lower than the temperature required to convert kaolin to Metakaolin.