TiO2-V2O5纳米复合薄膜的溶胶-凝胶制备及性能研究

采用溶胶-凝胶技术,以钛酸丁脂、V2O5粉末为原材料制备了纳米结构的TiO2-V2O5复合薄膜.使用XRD、FTIR、AFM、UV-VIS-NIR分光光度计等方法研究了复合薄膜的特性.实验结果表明:复合薄膜具有纳米孔洞结构;随V2O5含量的增加,TiO2晶相由锐钛矿向金红石的转变率大大提高,从500℃时纯TiO2的0.42%增加到含30%V2O5时的80.5%;复合薄膜在紫外区域的吸收显著增强,吸收边缘发生了红移.     

纳米TiO2改性丙烯酸涂层的抗紫外光作用

对两种不同晶型的纳米TiO2进行紫外可见光谱的测试,结果表明在波长300～330nm的范围内,金红石型结构的纳米TiO2对紫外光有强的吸收.利用十二烷基苯磺酸钠对纳米TiO2进行改性,提高其表面的亲油性,使之对有机基团有比较好的亲和性.在丙烯酸树脂中加入改性的纳米TiO2,并进行超声波分散和成膜,获得含不同比例纳米TiO2的丙烯酸树脂复合薄膜,对不同的纳米TiO2复合薄膜进行紫外可见吸收光谱分析.结果表明,在一定范围内,随着纳米TiO2含量的增加,纳米复合涂层对紫外光的吸收率呈上升趋势,抗紫外线性能增强.     

叠层式TiO2/SnO2复合纳米薄膜制备及其光电性能研究

采用溶胶-凝胶法在不同基体表面制备了叠层式TiO2/SnO2复合纳米薄膜.用扫描电子显微镜(SEM)、X射线衍射(XRD)对复合薄膜表面形貌和晶体结构进行表征.采用紫外-可见吸收光谱法和电化学方法来研究复合薄膜光学与光电化学性能特征.结果表明,所制备的叠层式TiO2/SnO2复合纳米薄膜表面连续、均匀、致密;XRD分析表明纳米TiO2为锐钛矿型结构,SnO2为金红石型结构;紫外-可见吸收光谱测试表明叠层式TiO2/SnO2复合纳米薄膜较纯TiO2薄膜的吸收范围拓宽;稳定电位随时间变化曲线(OCP-t)结果表明,叠层式TiO2/SnO2复合纳米薄膜光照下其光电化学性能高于纯TiO2薄膜;同时,光照后叠层式TiO2/SnO2复合纳米薄膜能有效储存TiO2先生电荷,延续对不锈钢基体的光生阴极保护性能.经比较,叠加3层SnO2的TiO2/3SnO2复合纳米薄膜改善光电性能最佳.     

耐高温Al2O3/TiO2纳米复合粉体的制备及表征

以TiCl4、Al2(SO4)3为原料,采用液相沉淀法制备了Al2O3/TiO2纳米复合粉体,同时对该纳米复合粉体的相变过程和晶粒生长过程进行了详细的研究,对紫外-可见光吸收进行了检测.结果表明:纳米TiO2粉体经Al2O3复合后,其耐温性能得到极大提高,复合粉体经950℃煅烧后锐钛矿相含量仍然在77%,晶体粒径在20nm左右;锐钛矿向金红石晶型的转变温度在950～1100℃的高温区.复合粉体在低温煅烧后,紫外-可见吸收强度较纯纳米TiO2有较大提高,高温煅烧后,复合晶的紫外光吸收红移.     

过渡金属离子掺杂对TiO2纳米尺寸及其相结构的影响

利用酸催化的溶胶-凝胶法合成了一系列不同掺杂量的Fe3 /TiO2、Cr3 /TiO2纳米复合微粒.用XRD和TEM研究了Fe3 、Cr3 的掺杂对TiO2纳米粒子尺寸和相结构的影响.结果表明:掺杂离子不同,对TiO2纳米粒子尺寸和相结构的影响不同.在所研究的掺杂量范围内(x:0.0000～0.1000),TiO2纳米粒子的粒径随Cr3 掺杂量的增加呈减小的趋势,但幅度不大;而Fe3 的掺杂则会引起TiO2粒子的团聚和晶粒的长大;由XRD分析可知:在掺杂量范围内,不会发生Fe2O3、Cr2O3等相的偏析,但Fe3 的掺杂引起了TiO2在低温条件下由锐钛矿向金红石的相转变.通过UV-Vis光谱的研究发现:Fe3 、Cr3 的加入,可以使TiO2对光的吸收拓展到可见区,同时随着掺杂量的增加,对可见光的吸收强度显著增强.     

硅基板上Fe掺杂TiO2氧敏薄膜的制备、结构与性能研究

采用溶胶-凝胶法,以Ti(OC4H9)4为前驱体,用提拉法在硅基板上制备了掺Fe的TiO2氧敏薄膜,对薄膜物相结构进行了X射线衍射(XRD)测定,利用扫描电镜(SEM)对薄膜微结构进行了观察.结果表明在硅基板上生长的TiO2薄膜中锐钛矿相为均匀小晶粒分布结构,金红石相以大尺度团聚结构形貌出现.Fe离子的掺杂对硅基板上制备的TiO2薄膜中金红石相的形成有很大的影响.Fe的掺入降低了金红石相的形成温度约100℃,Fe掺量在6mol%时,形成金红石相的量达到最大,即析晶能力最强.薄膜中形成晶相的晶格常数在＜6mol%的低Fe范围内,随较小的Fe离子取代较大的Ti离子,锐钛矿相和金红石相的晶格常数都随之减小;在＞6mol%的高Fe掺量范围内,随Fe掺量的增加,体系缺陷过量增加,晶格结构畸变严重,伴随着畸变能的释放,金红石相的晶格常数c轴逐渐增长,a轴略有下降(或基本不变).TiO2氧敏薄膜的氧敏性能受金红石相含量和氧空位浓度控制.当Fe离子掺杂浓度为6mol%时,金红石相及相应氧空位达到最大值,TiO2氧敏薄膜的氧敏性能也达到最大值,比刚形成金红石相的薄膜的氧敏性能增加近19倍.     

纳米TiO2和紫外线吸收剂对丙烯酸酯涂层抗光氧化性能的影响

讨论了锐钛矿型和金红石型纳米TiO2以及2．4-二羟基二苯甲酮和2-(2-二羟基-5-苯甲基)苯并三唑等有机紫外线吸收剂的光活性．并借助失重分析和SEM分析探讨它们对丙烯酸复合涂层抗光氧化性能的影响。UV分析表明：2，4-二羟基二苯甲酮、2-(2-二羟基-5-苯甲基)苯并三唑等有机紫外线吸收剂对400nm以下的紫外线有强烈的吸收作用；金红石和锐钛矿型纳米TiO2对紫外线也有较强烈的吸收和散射作用，紫外光透过率低。且有机紫外线吸收剂随着辐射时间的延长会分解失效，而纳米TiO2较稳定。失重分析和SEM分析结果显示：锐钛矿型纳米TiO2具有光催化性，加速丙烯酸酯聚合物的光降解，而金红石型纳米TiO2则是一种有效的遮光剂。同时添加金红石型纳米TiO2和有机紫外线吸收剂能更有效提高丙烯酸酯复合涂层的抗光氧化性能。     

混晶结构纳米TiO2粉的光催化活性

以钛酸四丁酯为钛源制备混晶结构纳米TiO2粉,研究了纳米TiO2的光催化活性与颗粒晶相结构之间的关系．结果表明,当金红石相的质量分数少于18．53％,光催化活性随着金红石相的增多而降低;当金红石相的质量分数为18．53％-28．2％时,随着金红石相的增多,光催化活性逐渐增强,在28．2％附近具有最高的光催化活性,与纯锐钛矿结构纳米TiO2粉的光催化活性相当;金红石相含量继续增加,则光催化活性逐渐降低．适量金红石相的存在有利于锐钛矿相中的电荷分离,使光催化活性提高．     

超细晶粒钛表面掺钽TiO2薄膜的微结构及血液相容性研究

采用直流反应磁控溅射法在超细晶粒钛表面沉积掺钽TiO2薄膜,研究了不同掺Ta量对超细晶粒钛表面TiO2薄膜结构、形貌和血液相容性的影响规律.结果表明,超细晶粒钛具有强烈的诱导金红石相形核效应,室温下可以获得超过90%含量的金红石型TiO2;Ta的掺入具有细化薄膜晶粒并抑制金红石相形成的作用;掺入少量Ta的TiO2薄膜具有较优的血液相客性;掺入过量Ta的TiO2薄膜为无定形结构,因抑制金红石相形成反而恶化TiO2薄膜的血液相容性.     

钒掺杂纳米TiO2薄膜的结构和光吸收性能

采用磁控溅射法制备了不同V含量的纳米TiO₂薄膜,利用SEM、XRD、Raman光谱和UV-vis吸收光谱对V掺杂TiO₂薄膜的表面形貌、结晶特性、晶格应力和光吸收性能进行了分析.结果表明,V掺杂可促进TiO₂薄膜晶粒的定向生长,得到尺寸分布较均匀的哑铃状晶粒,且可抑制薄膜的晶格膨胀和金红石型晶粒的生成.V掺杂TiO₂薄膜处于压应力状态,且应力随V含量增加而增大.V掺杂使导带底向带隙延伸,TiO₂薄膜光学带隙变窄,光响应范围从紫外区红移到可见光区域,提高了薄膜对可见光的吸收率.     

Preparation of ZrO2-CeO2 and HfO2-CeO2 nanopowders

We prepared weakly agglomerated powders of ZrO₂-CeO₂ and HfO₂-CeO₂ solid solutions 5–8 nm in particle size, consisting of monoclinic and tetragonal phases. After heat treatment at 1200°C, the crystallite size was 30 and 14 nm, respectively. We also examined the effect of precipitate freeze drying on the crystallization of hafnia-based solid solutions containing up to 20 mol % CeO₂.     

Comparison of the Electronic Structures of La2CuO4, Sr2CuO2Cl2, and Sr2CuO2F2

First-principles cluster calculations are reported of the local electronic structure of the three compounds: La₂CuO₄, Sr₂CuO₂Cl₂, and Sr₂CuO₂F₂. The copper ${\text{3d}}_{x^2 - y^2 } $ and the planar oxygen 2p _σ atomic orbitals exhibit a similar degree of covalency. The out-of-plane orbitals, however, are quite different with the ${\text{3}}d_{3z^2 - r^2 } $ atomic orbital lowered significantly in energy for chlorine and fluorine apical positions.     

Thermoelectric power of single-phase samples of Tl2CaBa2Cu2O y and Ba2CaSr2Cu2O y

Single-phase 2122 samples of thallium and bismuth superconductors were made by the precursor matrix method. The thermopower of these samples was measured in the temperature range 250 K-T _c . The thermopower was positive and decreased linearly with increasing temperature aboveT _c (onset). The exponential enhancement of thermopower seen in the undoped and doped YBCO was not observed in these samples. The linear variation of thermopower can be explained on the basis of either a two-band model or a narrow band model.     

VLE data for CO2-CF2Cl2, N2-CO2, N2-CF2Cl2 and N2-CO2-CF2Cl

Knowledge about vapour-liquid (VLE) is required as a basis of reliable calculations for separation processes. Correlations available for the prediction of T, p, x, y data are less accurate for mixtures at high pressures and mixtures containing supercritical components. The results of VLE experiments are reported and compared with data calculated with equations of state.     

Structure of Na2O·2TiO2 glass

X-ray radial distribution analysis and Raman spectroscopic measurement were carried out on Na₂O-2TiO₂ glass prepared by twin-roller quenching method. It is found that four-coordinated Ti⁴⁺ ions may be predominant over six-coordinated ones in the present glass. It is also found that the fraction of six-coordinated Ti⁴⁺ ions is larger in the present glass than in K₂O·2TiO₂ and Cs₂O·2TiO₂ glasses. Poorer glass-forming ability of the Na₂O-TiO₂ system compared with the K₂O-TiO₂ and Cs₂O-TiO₂ systems is ascribed to a larger fraction of TiO₆ octahedron for the former system.     

SiO2—TiO2—ZrO2系涂层的制备及其特性

用溶胶－凝胶法（sol-gel method）在不锈钢表面制备了SiO2-TiO2-ZrO2系无机氧化膜（STZ）。用DTA／TG、IR、XRD和SEM等手段研究了涂层制备时由凝胶向玻璃态的转变以及涂层薄膜的显微结构特点，考察了涂层对基体的保护效果。试验结果表明，在溶胶至凝胶最终转变为无机氧化物的过程中形成了无机网络，Si^4 和Zr^4 充当了网络骨架的形成离子。涂层为无定型玻璃态，其间混有石英、锐钛矿或金红石等微晶。     

Elastic and Electronic Properties of Superconducting CaPd 2 As 2 and SrPd 2 As 2 vs. Non-superconducting BaPd 2 As 2

The first-principles calculations were performed to predict the elastic and electronic properties of the superconducting ThCr₂Si₂-type phases CaPd₂As₂ and SrPd₂As₂ in comparison with the non-superconducting CeMg₂Si₂-type phase BaPd₂As₂. Besides, the same properties were compared for CeMg₂Si₂- and ThCr₂Si₂-type polymorphs of BaPd₂As₂. We found that all these phases are mechanically stable and belong to soft materials with low hardness. The near-Fermi region is formed by the valence states of the blocks [Pd₂As₂] with decisive contributions of Pd 4d states. The values of N(E _F) increase in the sequence: CaPd₂As₂ < SrPd₂As₂ < BaPd₂As₂, i.e. in the reverse sequence relative to the transition temperatures T _C. Thus, the change in T _C cannot be explained by the electronic factor, i.e. by the simple correlation T _C～N(E _F). Most likely the decrease in T _C in the sequence CaPd₂As₂ → SrPd₂As₂ and the absence of a superconducting transition in BaPd₂As₂ are related to the structural factors and the peculiarities of the electron–phonon coupling mechanism.     

Investigation of Instability of Lattice of Bi_2Sr_2CaCu_2O_x

Bi2Sr2CaCu2Ox superconductor was studied by differential scanning calorimetry (DSC) and thermogravimetry (TG) in different atmospheres. It is discovered that there is a thermal anomaly in the DSC curve, associated with a weight loss in the TG curve before the melting of the sample. Careful thermal analysis and high temperature X-ray diffraction reveal that the thermal anomaly and the weight loss show an instability of the crystalline Iattice. By annealing the sample in oxygen and argon, respectively and then by TC measurement and thermal analysis, the coincidence of transition temperature with the instability is found. The coincidence is further confirmed by Y-doped 2212 phase.     

Thermal conductivity of the system N2O4 ⇄ 2NO2 ⇄ 2NO + O2

Experimental data on the thermal conductivity of dissociating nitrogen tetroxide have been obtained by the hot-wire method in the temperature range from 290 to 870° K at pressures up to 10⁵ N/m².