热处理工艺对TiO2纳米管阵列结构及其光电性能的影响

通过阳极氧化法在钛箔上制备了TiO2纳米管阵列,在不同热处理工艺下使其晶化.利用扫描电子显微镜(SEM)和X射线衍射(XRD)对TiO2纳米管阵列的形貌和结构进行了表征.结果表明,阳极氧化法制备的TiO2纳米管经450~750℃热处理后为纳米晶结构,平均晶粒尺寸随退火温度升高而增大,相同温度下氮气气氛中热处理的TiO2平均晶粒尺寸小于空气气氛中热处理的TiO2.氮气气氛下退火可拓宽TiO2由锐钛矿型(Anatase)向金红石型(Rutile)结构转变的热处理温度范围,650℃以上退火处理后,TiO2纳米管中掺杂有少量的氮.光照开路电位测试和稳态极化曲线测试结果表明,在氮气气氛中、经650℃退火处理2 h制备的TiO2纳米管阵列电极光电响应性能最佳,此时TiO2为锐钛矿型和金红石型的混晶结构.     

多弧离子镀镀制掺氮二氧化钛薄膜及其光吸收特性的研究

利用多弧离子镀在玻璃衬底上制备了TiO2薄膜和氮掺杂的TiO2薄膜样品，并对样品进行了220～500℃温度的热处理，通过X射线衍射（XRD）以及UV—Vis分光光度计等测试手段对热处理前后的样品的结构、光吸收特性进行了分析。结果表明：制备出的薄膜为非晶态结构，热处理后向锐钛矿、金红石相转变。理想工艺下镀制的掺氮TiO2薄膜经400℃热后，TiO2薄膜的光吸收限可由385nm红移至500nm。     

纳米TiO2光催化剂的电化学法制备及其表征

采用有机电解-溶胶-凝胶法制备了纳米TiO2光催化剂,通过XRD、TEM、TG-DTA、激光粒度分析法等对纳米TiO2的结构相变、表面形貌、颗粒大小等进行了表征.实验表明:当热处理温度低于350℃时,TiO2的晶相结构均为锐钛型,颗粒大小在25nm以下,样品的比表面积大于65m2*g-1;热处理温度为400℃时,TiO2的晶相结构出现锐钛型和金红石型混合相,颗粒大小在35nm以下,样品比表面积为46.43m2*g-1,实验制备的粉体样品属于纳米级水平;实验测试了各焙烧温度下粉体样品的光催化活性.     

溶胶-凝胶制备SnO2/TiO2复合材料及其性能研究

采用溶胶-凝胶工艺制备了SnO2/TiO2复合光催化剂.以钛酸丁脂(Ti(C4H9O)4)为前驱体,冰醋酸为螯合剂,通过水解缩聚反应制备纳米TiO2,掺杂不同比例(n(SnO2)/n(TiO2)分别为1%、2.5%、5%)的SnO2对纳米TiO2进行改性,并对1%掺杂的粉体样品进行了不同温度(350～550℃)的焙烧处理.采用浸渍提拉法制备了1%(n(SnO2)/n(TiO2))掺杂的纳米SnO2/TiO2膜.运用X射线衍射(XRD)、透射电镜(TEM)、X射线光电子能谱(XPS)、原子力显微镜(AFM)及光吸收等手段,研究了不同掺杂量、热处理温度及光照时间对TiO2相变和光催化活性的影响.研究结果表明,350℃焙烧时,1%(n(SnO2)/n(TiO2))掺杂的粉体样品出现了合适比例的锐钛矿型和金红石型的混晶结构,具有较高的光催化效率,可达96.55%.而1%(n(SnO2)/n(TiO2))掺杂的纳米SnO2/TiO2光催化膜晶粒尺寸在20～30nm左右,光催化效率为79.6%,低于相同掺杂含量的纳米SnO2/TiO2掺杂光催化剂粉体.     

TiO2纳米管晶型对钛生物活性的影响

利用阳极氧化法在HF电解液体系中制备了高有序TiO2纳米管。样品分别在400和600℃下热处理后,得到锐钛矿和金红石两种晶型的TiO2纳米管。对样品进行了表征,将样品浸泡于模拟体液中,观察表面HA沉积情况,并进行体外细胞毒性实验以探讨样品的生物相容性。结果发现,400和600℃退火处理的纳米管样品生物活性高于未退火处理样品,400℃退火处理纳米管活性高于600℃退火处理纳米管。由于不同后处理条件下制备的纳米管形貌相似,仅为晶型不同,故推断出锐钛矿型TiO2生物活性最好,金红石型TiO2次之,无定型TiO2生物活性相对最差。     

真空热处理对纳米TiO2-x可见光催化的影响

本文以TiCl4水解法制备的锐钛矿型纳米TiO2为原料,采用真空热处理对其进行改性处理.利用XRD、XPS、紫外可见分光光度计等测试手段对真空热处理前后的纳米TiO2粉末进行了表征,并对结果进行了分析.结果表明,纳米TiO2经400℃×40min,真空度在1.0E-2Pa以下热处理后,在TiO2晶格中形成了氧空位缺陷,改变了TiO2的能带结构,得到了具有可见光催化活性的TiO2-x.其吸收阀值红移至550nm左右,实现了其对可见光的吸收.     

掺W纳米TiO2材料改性与光催化性能研究

溶胶-凝胶被广泛用来制备纳米氧化物材料。以钛酸丁酯为先驱体,冰醋酸为螯合剂,通过水解缩聚作用制备了纳米TiO2,掺杂钨元素对纳米TiO2进行改性,运用X射线衍射(XRD)和透射电镜(TEM)及光吸收等手段,研究了不同掺杂量对TiO2相变和光催化活性的影响,确定了最佳的掺杂量和热处理温度。     

碱热处理对钛表面生物活性的影响

利用碱热法处理钛表面,部分样品加热到450和700℃进行热处理,获得不同形貌和不同晶型的TiO2薄膜。实验得出,未经热处理的样品表面以非晶态钛凝胶层为主,450℃热处理样品主要以锐钛矿相TiO2存在,700℃热处理样品主要以金红石相TiO2出现。700℃热处理后的样品表面分布有大量50nm左右的纳米颗粒,这些纳米粒子的尺寸效应能较好地诱导HA在样品表面沉积形成,提高细胞的黏附和增殖,因此表现出较高的生物活性。450℃热处理后的样品表面相对于未处理样品有更多的HA沉积,是因为表面层的晶型起了主要作用,即锐钛矿TiO2晶体比无定型凝胶态TiO2更利于诱导HA沉积。但相对于未经任何处理的空白样品,仅用NaOH处理后的样品表面较利于HA沉积,可能是碱处理后钛表面羟基增加,进而提高了其诱导HA沉积的能力。     

铁掺杂TiO2光催化剂的制备及光催化性能

采用溶胶-凝胶法制备铁掺杂纳米TiO2光催化剂。通过XRD、FT-IR、UV-Vis、PL等对Fe-TiO2样品进行表征和分析,并以亚甲基蓝（MB）作为目标降解物,考察经不同热处理温度及不同掺铁量Fe-TiO2样品对MB的降解效果。结果表明所制备的Fe-TiO2样品的晶型为锐钛矿相与金红石相的混晶相,铁掺杂抑制了晶粒的生长和晶型的转变,样品的吸收阈值波长向可见光红移约68nm,提高了TiO2的光催化活性。在普通日光灯下,经500℃热处理、掺铁量与TiO2摩尔比为1∶200条件下制备的催化剂其光催化活性明显高于Degussa P25。     

聚苯胺改性纳米TiO_2的制备及其光催化性能

通过矿化接枝技术将溶胶-凝胶法制备的纳米TiO2负载在聚苯乙烯微珠裁体上,制成负载型纳米TiO2光催化剂.利用导电聚苯胺对负载型纳米TiO2光催化剂进行可见光改性,通过XRD、SEM等方法对改性纳米TiO2先催化剂进行表征,并用改性催化剂在太阳光照射下对3种工业含氰废水进行降解处理.结果表明,导电聚苯胺对负载型纳米TiO2光催化剂的涂膜改性,显著改善了负载型纳米TiO2光催化剂在可见光条件下的光催化性能,可有效降解废水中的大部分有毒氰根(CN-),使其含量远低于国家排放标准.     

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.