TiO2纳米微粒的溶胶-凝胶法制备及XRD分析

本文采用溶胶 凝胶法制备二氧化钛纳米微粒。用XRD分析了二氧化钛胶体经不同温度热处理后的晶粒粒径。分析表明温度在 4 73K时TiO2 微粒呈锐钛矿结构 ,粒径约为 5 5nm。在 6 73K以上TiO2 粒径迅速增大 ,微粒出现锐钛相与金红石相混晶结构。 973K时TiO2 微粒完全转化为金红石相。用晶界结构弛豫的观点解释粒径随热处理温度变化关系     

TiO2纳米微粒的溶胶—凝胶法制备及XRD分析

本文采用溶胶-凝胶法制备二氧化钛纳米微粒。用XRD分析了二氧化钛胶体经不同温度热处理后的晶粒粒径。分析表明温度在437K时TiO2微粒呈锐钛矿结构，粒径约为5.5nm。在673K以上TiO2粒径迅速增大，微粒出现锐钛相与金红石相混昌结构。973K时TiO2微粒完全转化为金红石相。用晶界结构弛豫的观点解释粒径随热处理温度变化关系。     

不同晶型的TiO2膜表面光致亲水性的研究

采用Sol-gel法在石英玻璃表面制备了TiO2膜,并经过不同温度焙烧得到不同晶相结构的TiO2膜,同时对膜进行了XRD、UV-Vis紫外-可见吸收光谱、SEM、亲水性的表征和比较.结果表明,TiO2膜在450℃焙烧后转为锐钛矿相结构,而700℃焙烧后则完全转变为金红石相结构.在低强度的紫外光照射下,锐钛矿TiO2膜的亲水性优于金红石和无定型态的TiO2膜;但是当光照强度大于1.0 mW/cm2时,锐钛矿、金红石和无定型TiO2膜的亲水性区别不大,无定型TiO2膜在高强度紫外光照射下表现出良好的亲水性.     

一维TiO2纳米材料的微观形态与结构的控制

采用水热法在不同温度下制备了TiO2一维纳米材料,并对其进行了微观形态和晶体结构研究.结果表明,通过控制系统的温度和压力可以分别得到TiO2纳米微粒、纳米管和纳米带.纳米管和纳米带材料具有不同于金红石和锐钛矿型的锐钛矿和钛酸的混合结构;将产物在500℃下热处理后,纳米管/带完全转变为锐钛矿型结构.     

不同介质中水热合成纳米TiO2粉体及其光催化性能研究

以钛酸四丁酯为原料,采用水热法分别以蒸馏水、有机小分子化合物(正丁醇、丙二酸和乙二胺水溶液)和无机酸(HNO3、H2SO4和HCl)为介质合成了TiO2纳米粉体.通过XRD和TEM对所得TiO2粉体进行了表征,研究不同介质对所得TiO2粉体的晶相组成、颗粒尺寸及形貌的影响.结果表明:以蒸馏水为介质时所得锐钛矿TiO2的颗粒尺寸分布不均匀;有机化合物抑制锐钛矿型TiO2各向异性生长趋势的能力为:正丁醇＞丙二酸＞乙二胺;相同实验条件下,HCl、H2SO4及HNO3体系中分别获得金红石、锐钛矿及锐钛矿和金红石混晶TiO2.光催化降解甲基橙的研究表明,锐钛矿和金红石混晶TiO2的光催化活性要高于纯锐钛矿结构;纯金红石型TiO2的光催化活性最差.     

二氧化钛催化剂晶型调控技术的研究进展

综述二氧化钛由锐钛矿向金红石晶型转变调控技术的最新成果,分析温度、氧化物和以及离子掺杂对实现晶型转变的影响规律,重点研究氧化物和离子掺杂对晶型转变的影响。结果显示:复合金属氧化物熔点低于TiO2熔点时,可促进锐钛矿型TiO2向金红石型转变;而金属氧化物熔点高于TiO2熔点时,可阻碍晶型转变;掺杂离子的离子半径、化合价、离子大小对二氧化钛晶型转变及催化性能有明显的影响,当掺杂金属离子半径大于或小于Ti4+半径,使得锐钛矿型TiO2更稳定;当掺杂离子的半径与Ti4+半径相近时,有利于锐钛矿型向金红石型转变,而体积较小的低价阴离子有利于金红石型二氧化钛的的生成,体积较大的高价阴离子则有利于锐钛矿型二氧化钛的的生成;阴阳离子共掺杂可以有效地调控二氧化钛晶型转变,并且能够提高TiO2的光催化活性。探讨二氧化钛多晶之间的协同作用,并基于二氧化钛掺杂改性的计算模拟,指出今后的发展方向。     

热处理对片状TiO2微粒相变的影响

用化学处理法制备了片状TiO2微粒，并对片状TiO2微粒及其焙烧产物的形貌和物相进行了分析。结果发现：片状TiO2微粒为无定型结构，片状颗粒非常薄；当加热到300℃以上时，TiO2片收缩变厚并由无定型转变为锐钛矿型结构．当继续加热使片状TiO2微粒由锐钛矿转变为金红石型结构时，原来的片状TiO2部分转变为长棒状的金红石型晶柱结构，而原料TiO2无论在多高的温度下焙烧都未出现长棒状晶柱结构；片状TiO2微粒的A→R相变温度比原料低大约300℃。     

硬脂酸法制备纳米TiO2及微结构控制

采用硬脂酸法制备了不同掺杂量的TiO2纳米晶,通过FTIR,XRD和TEM等实验手段对所得纳米TiO2进行分析和表征,并对反庆历程进行了初步探讨,实验结果表明,利用硬脂酸法,金红石型TiO2能在500度获得,掺杂Na 和K＋后则得到锐钛矿型TiO2,且随着掺杂量的增加,TiO2的粒径减少。     

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。     

酸性条件下金红石型TiO2纳米单晶的直接合成

以TiCl4为主要原料,通过压力热晶法在300～400℃酸性条件下直接制备金红石型的TiO2纳米单晶,并通过TEM,XRD,HRTEM,FFT等技术手段对TiO2纳米晶的结构和形貌进行了表征.结果表明:高温和高压下有利于TiO2结晶成型.TEM显示:制备得到的TiO2纳米晶具有四方型结构外观,尺寸为十几到几百纳米,高温灼烧后纳米晶型不发生变化.XRD显示:制备得到的TiO2纳米晶是金红石型结构.     

熔盐电解法制备TiW合金

采用熔盐电解法直接由TiO2和WO3混合物电极制备了高W含量的TiW合金,并对电解中的电流变化、物相组成和组织演变进行了研究分析。在900℃和3.1 V的电解条件下,在熔融CaCl2熔盐中,以石墨为阳极、TiO2和WO3的混合物为阴极进行电解,采用SEM、EDS和XRD等方法对电解还原过程中的产物进行了分析。电解后可制得成分可控的钛钨合金,氧含量较低。     

Removal of heavy metals from kaolin using an upward electrokinetic soil remedial (UESR) technology

An upward electrokinetic soil remedial (UESR) technology was proposed to remove heavy metals from contaminated kaolin. Unlike conventional electrokinetic treatment that uses boreholes or trenches for horizontal migration of heavy metals, the UESR technology, applying vertical non-uniform electric fields, caused upward transportation of heavy metals to the top surface of the treated soil. The effects of current density, treatment duration, cell diameter, and different cathode chamber influent (distilled water or 0.01 M nitric acid) were studied. The removal efficiencies of heavy metals positively correlated to current density and treatment duration. Higher heavy metals removal efficiency was observed for the reactor cell with smaller diameter. A substantial amount of heavy metals was accumulated in the nearest to cathode 2 cm layer of kaolin when distilled water was continuously supplied to the cathode chamber. Heavy metals accumulated in this layer of kaolin can be easily excavated and disposed off. The main part of the removed heavy metals was dissolved in cathode chamber influent and moved away with cathode chamber effluent when 0.01 M nitric acid was used, instead of distilled water. Energy saving treatment by UESR technology with highest metal removal efficiencies was provided by two regimes: (1) by application of 0.01 M nitric acid as cathode chamber influent, cell diameter of 100 mm, duration of 18 days, and constant voltage of 3.5 V (19.7 k Wh/m(3) of kaolin) and (2) by application of 0.01 M nitric acid as cathode chamber influent, cell diameter of 100 cm, duration of 6 days, and constant current density of 0.191 mA/cm(2) (19.1 k Wh/m(3) of kaolin).     

Comparative analysis of two methods for synthesis of fullerenes at different helium pressures

Abstract

The results of the effect of helium pressure in the chamber on the amount and composition of the produced fullerenes (C₆₀, C₇₀, etc.) synthesized in the arc plasma with graphite electrodes are presented. The findings obtained when the arc is powered by a direct (DC) and alternating (AC) currents of low frequency were compared in the same chamber with the electrodes located at the same angle to each other. These two methods are drastically different. The complete conversion of graphite into fullerene soot in AC occurs, but a part of the graphite is converted into a cathode deposit that does not contain fullerenes in DC, the relative amount of which increases when decreasing the helium pressure in the chamber. The highest fullerene content in fullerene soot of 10.2?wt.% is produced at a pressure of 127.5?kPa in AC arc, but in DC arc, the highest content of fullerenes in fullerene soot of 8.3?wt.% is produced at a pressure of 33.3?kPa.     

Structure and properties of Nb<Subscript>3</Subscript>Sn coatings produced by unsteady-current electrocodeposition of Nb and Sn

We have studied the effect of electric-current mode on the structure and characteristics of niobium stannide coatings produced by electrochemical coreduction of niobium and tin ions at the cathode in molten salts. The results demonstrate that single-phase Nb₃Sn coatings with a superconducting transition temperature T _c = 17.3–17.9 K can be obtained using unsteady-current deposition. The coatings produced in galvanostatic mode and by ac deposition at a frequency of 50 Hz have a columnar grain structure. Current-reversal deposition with pulse ratios above 7–9 results in a layered microstructure with layers parallel to the substrate surface, instead of the columnar microstructure, and ensures a considerably higher critical current.     

Detecting large biomolecules from high-salt solutions by fused-droplet electrospray ionization mass spectrometry

A novel fused-droplet electrospray ionization (FD-ESI) source was developed to generate peptide and protein ions. The sample solution was first ultrasonically nebulized to form fine aerosols. The aerosols were then purged into a glass reaction chamber via nitrogen. Charged methanol droplets were continuously generated through electrospraying the acidic methanol solution from a capillary, which was located at the center of the reaction chamber. As the sample aerosols entered the reaction chamber, they fused with the charged methanol droplets from which electrospray proceeded continuously. The mass spectra of peptide and protein that FD-ESI-MS produced were practically identical to those that conventional ESI-MS produced. However, FD-ESI-MS resulted in an extremely high salt tolerance. Cytochrome c ions were detected in the solutions that contained 10% (w/w; 1.709 M) NaCl or 2.5% (425 mM) NaH2PO4. As with those obtained from the solution that lacked NaCl and NaH2PO4, the width of cytochrome c ion peaks remained nearly unchanged.     

Simultaneous removal of organic contaminants and heavy metals from kaolin using an upward electrokinetic soil remediation process

Kaolins contaminated with heavy metals, Cu and Pb, and organic compounds, p-xylene and phenanthrene, were treated with an upward electrokinetic soil remediation (UESR) process. The effects of current density, cathode chamber flushing fluid, treatment duration, reactor size, and the type of contaminants under the vertical non-uniform electric field of UESR on the simultaneous removal of the heavy metals and organic contaminants were studied. The removal efficiencies of p-xylene and phenanthrene were higher in the experiments with cells of smaller diameter or larger height, and with distilled water flow in the cathode chamber. The removal efficiency of Cu and Pb were higher in the experiments with smaller diameter or shorter height cells and 0.01M HNO(3) solution as cathode chamber flow. In spite of different conditions for removal of heavy metals and organics, it is possible to use the upward electrokinetic soil remediation process for their simultaneous removal. Thus, in the experiments with duration of 6 days removal efficiencies of phenanthrene, p-xylene, Cu and Pb were 67%, 93%, 62% and 35%, respectively. The experiment demonstrated the feasibility of simultaneous removal of organic contaminants and heavy metals from kaolin using the upward electrokinetic soil remediation process.     

Eine Thermovakuumkammer für die Weltraumsimulation

A thermic vacuum chamber is used for testing devices and components under space simulated conditions. We take a cryopump and a LN2 baffle for an oil free and vibration poor vacuum generation at pressures down to 3.10^?6 mbar. The surrounding temperature of the device under test can be varied between 83 K and 373 K by PC controlled shrouds. Temper areas simulate the influence of own and strange heatsources on the tested units. The actual behaviour of the device under test at different vacuum and temperature conditions can be observed via an optical window located at the chamber door. For these measurements there are two optical adjusting benches on both sides of the chamber door. The testing units are mounted in a clear room. A lot of optical and thermal measuring techniques as well as a mass spectrometer can be connected to the vacuum chamber. Because of different electrical and fluid feedthroughs at the chamber it can be used for a wide range of research task. The application of this thermic vacuum chamber is demonstrated at some examples.     

Removal of color from real dyeing wastewater by Electro-Fenton technology using a three-dimensional graphite cathode

This work investigates the removal of color from wastewater that contains low dyestuff concentrations by the Electro-Fenton process. The color was removed by in situ electrogenerated hydrogen peroxides at a three-dimensional graphite cathode with added ferrous sulfates. Experimental runs were conducted to evaluate the effect of the operating parameters, such as the oxygen contact mode, the oxygen sparging rate, the applied current density, the concentration of ferrous ions, the solution temperature and the pH among others, on the removal of color. The removal efficiency of the color in the cathodic chamber reached 70.6% under specified operation conditions in 150 min. The removal efficiency was controlled by the mass transfer when the oxygen-sparging rate was less than 0.3 dm(3)/min for the reactor configuration herein. The optimal applied current density was 68 A/m(2) when the energy consumption was considered. The highest removal efficiency was obtained by adding 20 mM Fe(II) to the solution. The optimal solution pH was 3 in this work. The temperature negatively affected color removal.     

铜纳米线阵列的模板组装

采用电解法溶解多孔阳极氧化铝(PAA)模板的阻挡层,用直流电沉积的方法在模板中组装了铜纳米线阵列.分别用扫描电镜和X射线衍射表征铜纳米线阵列的形貌和晶体结构,用电化学法表征了铜纳米线阵列的电催化性能.结果表明,PAA去阻挡层后,伏安图上出现一个阳极氧化峰.恒电位沉积的铜纳米线直径为22nm,沿(111)晶面择优取向.铜纳米线阵列电极能催化亚硝酸根的还原,其催化电流比本体铜电极上大2倍,峰电位正移80mV.纳米铜阵列电极可用于亚硝酸盐的电化学检测.     

Virtual anode as a source of low-frequency oscillations of a high-current electron beam

We have studied the transport of a relativistic electron beam with supercritical current in a cylindrical drift chamber in the presence of an ion flux. A theoretical analysis of the electron-ion flux dynamics was based on the coarse particle PIC method (code SOM). Simultaneous injection of a supercritical electron beam and a weak-current low-energy ion beam may result in the formation of a virtual anode in addition to the electron virtual cathode in a drift chamber. The virtual anode exhibits periodic pulsations. Numerical results obtained for hydrogen and nitrogen ions show that the ratio of the frequencies of these pulsations is inversely proportional to the square root of the ion mass ratio. These oscillations of the virtual anode lead to temporal modulation, at the same frequency, of both electron and ion currents at the drift chamber output.