微波超声强化银掺杂TiO_2催化剂光催化活性的研究

在[Bmim]PF6离子液体介质中,用溶胶凝胶-微波干燥法制备银掺杂TiO_2光催化剂TiO_2-Ag.以甲基橙为有机污染物,用微波超声组合仪分别在微波(MW)、紫外(UV)、紫外-微波(UV-MW)和超声-紫外-微波(UT-UV-MW)4种条件下降解甲基橙溶液,考察银掺杂对催化剂降解甲基橙的影响,以提高催化剂光催化性能.分别用X射线衍射分析(XRD)、扫描电子显微镜(SEM)、能谱分析(EDS)、热重-差示扫描量热分析(TG-DSCDTG)、固体紫外可见分析(Uv-vis)和红外分析(IR)对TiO_2-Ag催化剂进行测试表征.结果表明,优化条件下制备TiO_2-Ag催化剂在UV、UV-MW和UT-UV-MW条件下降解甲基橙35 min后,甲基橙的降解率分别为88.05%、93.98%和99.84%;降解甲基橙55min后,甲基橙的降解率分别为98.79%、99.05%和99.90%.在UTUV-MW条件下降解25min后,降解率接近100%.表明TiO2-Ag催化剂具有较高的光催化降解活性,微波超声协同作用加快光催化降解反应进行.催化剂的结构分析表明,银掺杂抑制了二氧化钛晶相的转变,使相变温度升高,稳定性增强;同时,催化剂向可见光区扩宽了光响应范围,提高了量子效率,从而光催化性能得以提高.     

微波助离子液体中锌和氮共掺杂TiO2催化剂的制备及微波强化光催化氧化活性

在1-丁基-3-甲基咪唑六氟磷酸盐（[Bmim]PF6）离子液体介质中,采用微波干燥的方法制备了锌和氮共掺杂的TiO2催化剂TiO2-Zn-N,分别采用IR、XRD、SEM、BET对催化剂结构进行了测试和表征。室温条件下,以甲基橙和苯酚溶液为模拟污染物,在微波超声波组合催化合成仪中,分别利用微波辐射（MW）、紫外光照（UV）、微波辐射-紫外光照（MW-UV）和太阳光照射（SL）等降解方式,着重考察了制备条件对TiO2-Zn-N光催化活性的影响。结果表明,在离子液体用量为5.6 mL、Zn掺杂量n(Zn)/n(Ti)=0.015:1、N掺杂量n(N)/n(Ti)=4:1、微波干燥功率350 W、微波干燥时间20 min、煅烧温度700 ℃、煅烧时间2 h的条件下所制得的TiO2-Zn-N催化剂具有较高的光催化活性;在MW、UV、MW-UV和SL四种降解条件下,TiO2-Zn-N对甲基橙的降解率分别为29.6%、95.4%、99.2%和79.2%;并且在前三种降解条件下,甲基橙降解率始终是：MW-UV> UV> MW。这表明在紫外光照条件下,微波辅射具有强化催化剂降解甲基橙的作用。     

H_2O_2处理H_3PW_6Mo_6O_(40)/ZrO_2-SiO_2光催化降解甲基橙

采用浸渍法制备了H_3PW_6Mo_6O_(40)/ZrO_2-SiO_2催化剂,用H_2O_2进行敏化处理,并通过FT-IR、XRD对其进行了表征。探讨了该催化剂对甲基橙溶液的催化降解活性,较系统地研究了溶液的初始浓度、溶液的pH、催化剂用量对光催化降解甲基橙的影响。研究发现:H_3PW_6Mo_6O_(40)/ZrO_2-SiO_2对甲基橙有良好的降解效果。在甲基橙溶液初始浓度为10mg·L~(-1),溶液pH为2.5,催化剂用量为溶液总质量0.5%的条件下光照2.5h,甲基橙的降解率达到91.1%。H_3PW_6Mo_6O_(40)/ZrO_2-SiO_2催化剂光催化降解甲基橙溶液为一级动力学反应。     

氟铌酸钾的低温固相法合成及其对甲基橙的光催化降解性能

以草酸铌、草酸钾和氟化钾为原料,采用改进的固相法在较低温度(600℃)下合成了层状K2NbO3F;测定了其对甲基橙光催化降解的催化作用,并基于紫外-可见漫反射光谱分析和X射线衍射分析初步探讨了甲基橙在自然光照条件下的光催化反应过程及降解机理.结果表明,合成的K2NbO3F与微量H2O2作用后,在自然光照条件下几乎可以使甲基橙染料完全降解;当反应温度为45℃,催化剂投加量为1g/L,H2O2用量为0.33%(体积分数)时,2h内可将初始浓度为15mg/L的甲基橙溶液几乎完全降解.就甲基橙的光催化降解机理而言,·OH自由基在其降解过程中起重要作用.     

微波辅助离子液体中锌-铁共掺杂纳米TiO_2光催化剂的制备及其光催化活性

在[Bmim]PF_6离子液体介质中,用微波于燥的方法制备了锌-铁共掺杂纳米TiO_2(TiO_2-Zn-Fe)光催化剂;并以甲基橙为模拟污染物,紫外灯为光源,考察了离子液体加入量、锌-铁掺杂量、微波干燥功率、微波干燥时间、煅烧温度、煅烧时间等因素对TiO_2-Zn-Fe光催化活性的影响.结果表明,掺杂物质硝酸锌和硝酸铁与钛酸丁酯的物质的量比分别为n(Zn)/n(Ti)=0.25%和n(Fe)/n(Ti)=0.005%时,在家用微波炉中于210W功率下干燥17.5min,再在高温箱式电阻炉中于540℃下煅烧处理1.5h,得到的TiO_2-Zn-Fe光催化剂的活性明显优于单一掺杂的TiO_2-Zn或TiO_2-Fe以及未掺杂的纯TiO_2,在紫外光照60min及太阳光照3h条件下相应的甲基橙的降解率分别达99.8%和99.6%.     

微波助离子液体中纳米TiO2／PMMA复合材料的制备及光催化性能

微波加热法合成离子液体[Bmim]BF4,并以该离子液体为反应介质,在微波辐射条件下制备纳米TiO2/PMMA复合材料.用XRD,IR和TG对该复合材料进行测试和表征;并在高压汞灯下用甲基橙溶液对其进行光催化降解性能测试.结果表明,制备TiO2/PMMA复合材料的最佳条件是:离子液体1.7mL,钛酸丁酯与MMA的体积比为3.4∶1.0,微波辐射功率600W、反应温度70℃、反应时间35min.并且用[Bmim]BF4作为反应介质,能够显著提高TiO2/PMMA复合材料的光催化活性,所制备的TiO2/PMMA复合材料不需要经过高温煅烧,就表现出极高的光催化活性;TiO2负载PMMA后,复合材料的光催化活性得到了进一步的改善.该复合材料对甲基橙的降解率在1.5h就可达到98.4%,其活性明显优于未负载的纳米TiO2催化剂.     

亚硫酸盐协助中空Bi2WO6微球的光催化性能

本文利用亚硫酸盐与Bi2WO6协同作用,有效地提升其光催化活性。以甲基橙和抗生素环丙沙星(CIP)作为被降解物对该体系的光催化降解性能和机理进行了研究。结果表明:光催化活性增强主要原因为亚硫酸盐能与Bi2WO6的光生空穴及羟基自由基反应,不仅能生成新的活性物质亚硫酸自由基(SO3^2-),还能促进Bi2WO6光生电子—空穴对的分离。此外,还考察了催化剂的用量、和污染物的浓度对该体系光催化性能的影响。     

Fe-Ni 共掺杂 ZnO 的制备及其光催化降解甲基橙活性

 采用溶液法制备了 Fe-Ni 共掺杂 ZnO 光催化剂, 并运用 X 射线衍射、扫描电镜和原子发射光谱等对催化剂进行了表征. 以甲基橙 (MO) 为模型污染物, 评价了样品的光催化活性, 考察了甲基橙初始浓度及其 pH 值, 以及催化剂用量等对光催化反应性能的影响. 结果表明, Fe-Ni 共掺杂降低了 ZnO 的结晶度, 并促进了晶粒的长大. 光催化降解反应表明, Fe-Ni 共掺杂显著提高了 ZnO 光催化降解甲基橙的活性, 当催化剂用量为 0.6 g/L, 经 120 min 紫外光照射时, 可使甲基橙溶液 (10 mg/L) 降解率达到 93.5%. 关键词：铁; 镍; 共掺杂; 氧化锌; 光催化; 甲基橙; 降解     

活性炭负载纳米TiO2光催化降解性能研究

本文研究活性炭负载纳米TiO2的光催化降解性能和影响甲基橙废水处理的主要因素。结果表明:用溶胶-凝胶法制备的TiO2-活性炭催化剂具有比表面积大、分散性高、光催化降解性能好、可重复利用等优点;采用30W高硼紫外光灯,TiO2-活性炭光催化降解浓度为1500mg/L甲基橙废水的最优工艺条件是:催化剂活化温度为700℃、用量为1.0g/L、废水起始pH值为1、反应温度为45℃、光照时间为50m in。在此条件下,甲基橙和CODC r的去除率分别达99.8%和99.7%。     

AuNPs@POMs/rGO复合材料的制备及光催化性能

以Keggin型多金属氧酸盐(多酸,POMs)为光催化还原剂、稳定剂和包覆剂,在光照下一步合成AuNPs@POMs/rGO复合纳米材料。采用透射电镜(TEM)、X射线衍射(XRD)和紫外-可见吸收光谱(UV-vis)等对所制得的材料进行了结构表征和性能测试。以光催化降解甲基橙为模型反应研究了AuNPs@POMs/rGO纳米复合材料的光催化活性。透射电子镜结果显示Au纳米微粒均匀的负载在rGO薄层上,无聚集和团聚现象。实验探究了pH、温度、催化剂投放量以及甲基橙初始浓度对光催化降解过程的影响。光催化降解结果表明:当溶液处于室温,pH=8.0,催化剂投放量为0.15 g·L~(-1),甲基橙溶液初始浓度为25.0 mg·L~(-1)时,效果达到最佳,降解率为94.5%。     

Thermal imaging of microwave fields inside the surfatron and the microwave plasma torch

A new method is introduced for imaging microwave fields, such as those found in microwave-plasma support structures. The method relies upon the darkening that such fields cause in heat-sensitive paper, such as that used in some telefax printers. With this new method, the microwave-frequency electric fields inside two microwave-plasma support structures, the surfatron and the microwave plasma torch, have been measured and subsequently imaged in three dimensions. The images reveal that the surfatron and microwave plasma torch have different operational behavior. As expected, the electric field strength inside the surfatron exponentially falls off down the length of the quartz plasma tube. The field inside the microwave plasma torch initially diminishes, but then increases in strength towards the end of the tube. An aerosol was introduced into the surfatron to observe the effect of water vapor on the electric field strength and distribution. The exponential axial decay of the electric field in the ‘dry’ surfatron plasma, characteristic of a surface wave propagating down a quartz plasma tube, is extended further down the quartz tube in the ‘wet’ plasma. A drop in plasma conductivity is likely the origin of the elongated propagation of the surface wave.     

Predicting the suitability of microwave formulation using microwave differential thermal analysis (MWDTA)

Journal of Thermal Analysis and Calorimetry - Microwave-assisted formulation is becoming an established method of formulation in industry, providing a fast, economic and environmentally more...     

The microwave spectrum of tellurophene

The microwave spectrum of tellurophene, C₄H₄Te, has been recorded between 8 and 27 GHz. The rotational constants obtained from least-squares fitting of low-J lines are:

Figures in parentheses are uncertainties in last place of decimal (95% confidence limit). Corresponding inertial defects are 0.094 (7), 0.095 (6) and 0.097 (10) amu A² respectively, indicating the essential planarity of the molecule.Stark shift measurements correspond to a dipole moment of μ_a = 0.619 x 10^?30 C m (0.186 D).An approximate structure, based on bond lengths of CC and CH bonds adopted from related molecules, implies that r (Te - C) = 205.5 pm and ? C (5) TeC (2) = 82.53°.     

Cross-metathesis assisted by microwave irradiation

Microwave irradiation effectively accelerates cross-coupling metathesis reactions between deactivated olefins. Reactions have been carried out with the phosphine-free Hoveyda-Grubbs catalyst and the "second generation Grubbs' catalyst." While there have been reports that a "microwave effect" is observed in various transformations, the accelerations we observe are due to the efficient and rapid heating and increased pressure in the microwave apparatus.     

微波在高分子中的应用

作为一种新型高效的加热方式，微波技术为高分子合成及应用提供了一种新思路，它的应用可大大降低反应的时间与能耗，提高各种反应的速率、收率和选择性，正日渐成为人们关注的热点。本文综述了近年来微波技术在高分子材料，特别是功能高分子材料合成中的应用，以及微波固化与传统热固化的同异，指出微波固化高效均匀，可使固化反应加速，降低固化时间，产品的物理和机械性能优异，可在更广的范围内替代热固法。     

Methane dimerization via microwave plasmas

Methane can be converted to ethane and ethylene in a microwave plasma reactor at pressures from 10 to 100 mm Hg. The total methane conversion has a linear correlation with power ? (45 + pressure)/flow and can be as high as 90%. The conversion of methane to ethylene varies from 0 to 11%. It reaches a maximum at a value of Power ? (45 + Pressure)/Flow of 2200 W?mm Hg?s/mL. The energy efficiency of driving this thermodynamically unfavourable reaction is 2%.     

Dielectric spectroscopy at microwave frequencies

A method is described which is capable of measuring the dielectric properties of liquids as a continuous function of frequency over the range 10 MHz to 18 GHz; an evaluation is made of its performance over the frequency range up to 4.2 GHz. The method described has substantial advantages in ease of operation and evaluation of results over the conventional “spot” frequency and time-domain spectrometer techniques.     

Atomic-scale rectification at microwave frequency

Microwave of known amplitude and frequency, irradiating the junction of a low temperature scanning tunneling microscope, was found to induce a dc signal. This rectification current is spatially localized and exhibits chemical sensitivity at the atomic scale. Dependence of the rectification current on the sample bias voltage reveals spin splitting in the electronic state of a single Mn atom and vibrations of single MnCO molecule. These results demonstrate the feasibility of atomic scale nonlinear spectroscopy and the potential for the detection of resonance phenomena excited with a spatially extended electromagnetic wave.     

Two-dimensional chirped-pulse Fourier transform microwave spectroscopy

Two-dimensional (2D) correlation techniques are developed for chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy. The broadband nature of the spectrometer coupled with fast digital electronics permits the generation of arbitrary pulse sequences and simultaneous detection of the 8-18 GHz region of the microwave spectrum. This significantly increases the number of rotation transitions that can be simultaneously probed, as well as the bandwidth in both frequency dimensions. We theoretically and experimentally evaluate coherence transfer of three- and four-level systems to relate the method with previous studies. We then extend the principles of single-quantum and autocorrelation to incorporate broadband excitation and detection. Global connectivity of the rotational energy level structure is demonstrated through the transfer of multiple coherences in a single 2D experiment. Additionally, open-system effects are observed from irradiating many-level systems. Quadrature detection in the indirectly measured frequency dimension and phase cycling are also adapted for 2D CP-FTMW spectroscopy.