ZnS/TiO2聚砜纤维复合材料的制备及其光催化水制氢性能的研究

利用高压静电纺丝制备了具有良好耐光降解性能的羧基聚砜电纺纤维毡,利用其为载体用水热反应法制备了ZnS/TiO2聚砜复合光催化材料,得到了分布均匀的ZnS/TiO2聚砜纤维复合材料。通过X射线衍射、光电子能谱、紫外-可见漫反射光谱、热失重、耐紫外光降解实验对复合材料进行了表征。光催化分解水制氢实验表明:ZnS/TiO2含羧基聚砜纤维复合材料的催化效率高于同等条件下粉体ZnS/TiO2,并且具有很好的重复稳定性。     

两步水热法制备还原氧化石墨烯/纳米TiO_2复合材料及其光催化性能

为研究由还原氧化石墨烯(RGO)和具有高活性晶面的TiO_2组成的复合材料的制备方法及其光催化性能,首先采用两步水热法制备了RGO/纳米TiO_2复合材料:第1步为合成暴露高活性晶面的纳米TiO_2;第2步为将合成的纳米TiO_2与氧化石墨烯(GO)复合,形成RGO/纳米TiO_2复合材料。然后,利用XRD、SEM、X射线光电子能谱仪和紫外-可见漫反射光谱等手段对制备的暴露不同晶面的纳米TiO_2和RGO/纳米TiO_2复合材料进行了表征,评价了其光催化性能。结果表明:在水热法的第1步中,通过调节HF的浓度能可控制备出具有高活性的(001)和(101)晶面的纳米TiO_2,氟原子在纳米TiO_2中以物理吸附态和化学结合态这2种形态存在;在第2步后,GO与纳米TiO_2复合形成RGO/纳米TiO_2复合材料,同时在此过程中GO被转化成RGO。在紫外光照射下,两步水热法合成的RGO/纳米TiO_2复合材料具有很好的光催化性能,明显优于商用TiO_2(P25)和纳米TiO_2的。RGO/纳米TiO_2复合材料的光催化性能有明显的提高,RGO和TiO_2暴露的晶面对光催化活性有影响。     

TiO2/石墨烯复合材料的制备及其光催化性能

本文以氧化石墨烯和钛酸丁酯为原料,利用水热法一步制备了TiO2/石墨烯复合光催化材料,研究了氧化石墨烯用量、反应温度、反应时间对TiO2/石墨烯复合材料光催化活性的影响。采用XRD,SEM,TEM和氮气吸附-脱附实验(BET)对复合光催化材料的物相、颗粒粒径、形貌及比表面积进行了表征。结果表明,本实验最佳条件是:氧化石墨烯1mg,制备温度为180℃,反应时间为16 h。产物中的TiO2为锐钛矿晶型,其平均粒径约为18 nm。复合材料的比表面积为170m2/g,平均孔径为12.45 nm。在可见光照射(λ>420nm)下以TiO2/石墨烯为光催化剂对有机染料罗丹明B(Rhodamine B,RhB)进行光催化降解,其光催化活性明显高于相同条件下制备的TiO2。     

水热法制备N-TiO_2/RGO复合材料及光催化性能研究

采用一步水热法制备氮掺杂负载石墨烯(RGO)的二氧化钛(TiO_2)复合光催化材料(N-TiO_2/RGO),对样品进行XRD、SEM、UV-Vis等表征并以甲基橙为目标降解物进行可见光光催化活性测试。结果表明:N-TiO_2/RGO比同条件下制得的N-TiO_2和TiO_2/RGO具有更好的可见光光催化性能,可见光下照射5h,对甲基橙的降解率可达到95%。     

还原氧化石墨烯/SnS_2纳米复合物的制备与可见光光催化性能

以氧化石墨烯(GO)和SnCl_4·5H_2O为前驱体,通过水热法制备了SnS_2/还原氧化石墨烯(RGO)复合材料。用X射线衍射(XRD)、扫描电镜(SEM)、拉曼光谱和紫外-可见(UV-Vis)吸收光谱表征了所制备的样品。在可见光(λ≥420nm)光照下光催化降解甲基橙水溶液来检测SnS_2/RGO复合物的光催化活性。结果表明:所制备的SnS_2/RGO复合物表现出增强的可见光光催化活性,其中,含1%(wt,质量分数,下同)石墨烯的复合光催化剂活性最好。SnS_2/RGO复合物光催化活性的增强是由于石墨烯是优秀的电子受体和传输体,它减少了光生载流子的复合,从而提高了光催化活性。     

Bi_2O_3/RGO的制备及其光催化还原CO_2性能的研究

利用氨沉淀法制备Bi_2O_3粉体,采用改进的Hummers法制备GO,将Bi_2O_3加入一定量的GO分散液中,采用紫外还原法制备Bi_2O_3/RGO复合光催化剂,通过XRD、SEM、EDS、BET等技术手段对催化剂进行表征,并考察其在紫外光下催化还原CO_2的性能。结果表明,GO在紫外照射过程中被有效地还原为RGO,与晶粒尺寸约为49nm的单斜晶系Bi_2O_3颗粒在紫外照射下共同搅拌,形成Bi_2O_3/RGO复合物,其Bi_2O_3的主要衍射峰发生轻微宽化,石墨烯碎片、絮状物质附着在Bi_2O_3表面;随着GO含量的增加,Bi_2O_3表面附着的石墨烯碎片、絮状物质增加,复合催化剂的比表面积增大;在紫外光照射下,Bi_2O_3/RGO复合催化剂的光催化效果明显高于Bi_2O_3,GO含量为2.0%(质量分数)的Bi_2O_3/RGO复合催化剂,在光照时间为8h时,生成CH_4的产量为1.012μmol/g,比Bi_2O_3提高了96.5%。     

石墨烯/Ni/TiO_2/CNTs复合物的制备及其光催化性能

首先通过溶剂热法,在石墨烯表面负载掺杂镍的纳米二氧化钛膜,制备石墨烯/Ni/TiO2复合材料;然后以掺杂的镍为催化剂,采用化学气相沉积法,原位生长碳纳米管(CNTs),得到石墨烯/Ni/TiO2/CNTs复合材料。通过XRD、SEM、TEM、拉曼等方法对制备样品的晶型、微观形貌等进行了表征,考察了样品在紫外光及可见光下对甲基橙的光催化降解性能。结果表明:石墨烯和CNTs的加入使得Ni/TiO2、石墨烯/Ni/TiO2、石墨烯/Ni/TiO2/CNTs复合物的光催化活性依次提高,并且石墨烯/Ni/TiO2/CNTs复合物中石墨烯含量越多时,所得复合物的光催化降解性能越好。石墨烯含量最大的石墨烯/Ni/TiO2/CNTs样品,在紫外光下对甲基橙的降解率达到98%,在可见光下的光催化降解效率比掺镍TiO2提高了3.5倍。     

热还原法制备氧化石墨烯/TiO_2复合材料及其光催化性能研究

采用Hummers法制得氧化石墨烯,以钛酸丁酯为钛源,采用原位溶胶-凝胶技术制备了氧化石墨烯/TiO2复合材料,进一步经过加热还原的方法,制备热还原氧化石墨烯/TiO2复合光催化剂,通过FT-IR、XRD、Raman、SEM、TEM和UV-Vis光谱等对产物进行了表征,并测试了该复合光催化剂在可见光下对甲基橙的光催化降解性能。结果表明,制备的复合光催化剂主晶相为锐钛矿型TiO2,热还原氧化石墨烯表面富集的颗粒尺寸15nm左右,颗粒分布均匀。热还原氧化石墨烯/TiO2复合光催化剂在可见光下具有优异的光催化性能。     

溶剂对钨酸铋/石墨烯形貌结构和光催化性能的影响

本工作采用溶剂热法通过乙二醇、乙二胺、水-乙二醇、水-乙二胺、水和水-乙酸不同溶剂制备可见光催化剂Bi2 WO6/RGO,并对其形貌结构和光催化性能进行表征.研究结果表明,溶剂对Bi2WO6/RGO的形貌和光催化性能有显著影响.在可见光(λ>420 nm)照射下,以水为溶剂制备的样品对罗丹明B(RhB)的光催化降解性能最佳,20 min内降解率达到98％,且经过五次循环降解后光催化效果基本保持不变.Bi2 WO6/RGO的光催化性能增强可归因于在水溶剂下形成的Bi2 WO6分级结构微球为光催化反应提供更多的反应活性位点,同时石墨烯的引入增大了材料的比表面积,进一步促进了电子-空穴对的有效分离.自由基捕获实验表明,复合材料光降解RhB过程中光生空穴(h+)起主要作用,·O2-和·OH起次要作用.     

石墨烯/纳米TiO_2复合材料的制备及光催化还原性能

为探索超声辅助下利用紫外光及耦合热还原工艺制备RGO/纳米TiO_2复合材料的方法,并对其在缺氧水体中的光催化还原特性进行研究,首先,以鳞片石墨为原料,采用改进的Hummers法制备了氧化石墨烯(GO),进而通过超声/紫外光还原工艺制备了还原氧化石墨烯(RGO);然后,以钛酸丁脂和RGO为前驱物,采用溶胶-凝胶法并在氮气保护下高温加热制备了RGO/纳米TiO_2复合光催化材料;接着,利用FTIR、XRD、BET及紫外-可见光谱等对RGO/纳米TiO_2复合材料进行了结构性能表征;最后,以2,4-二氯苯氧乙酸(2,4-D)为探针物,研究了RGO/纳米TiO_2在缺氧水体中的光催化特性与2,4-D降解机制。结果表明:采用低温氧化Hummers法制备的GO六碳环上生成的活性基团较少,采用超声/紫外光还原工艺及耦合高温热还原工艺可使环状结构得到良好的修复;所制备的RGO/纳米TiO_2复合材料具有良好的2,4-D降解能力,在缺氧状态下,2,4-D主要发生光催化还原反应,脱除苯环上的氯,产生氯酚、邻苯三酚及间苯三酚等中间产物,部分2,4-D被氧化降解生成CO_2和H_2O。制备的RGO/纳米TiO_2复合材料具有良好的光催化还原性能。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.     

空压机轴承箱蜗壳温度探头油封改造

由于空压机进气侧轴承箱蜗壳温度探头密封效果不好,使空压机及其后续管道受到油污染。后将温度探头的O形圈密封改为骨架油封,杜绝了轴承箱漏油问题。文章简介空压机的结构和技术参数,详细介绍了骨架油封的制作和优点。     

Characteristics of mechanical properties of materials in studies of conditions of attainment of marginal states

It is shown that conditions of attainment of marginal states in the material of structural components are formulated on the basis of analysis of force and deformation criteria of formation and development of destruction. The parameters of these criteria are data on types of structural materials, standard and special characteristics of their mechanical properties, structural forms of considered elements of the equipment, and their operating stress loading. In this case, the construction of a system of state equations for describing interrelation of current damage, external actions, and responses to them is based on the concept of calculating variations in properties of materials at all stages of the design life cycle.     

Determination of parameters of microstructural inhomogeneity of deformation of metals by the method of modeling

The article suggests a method of evaluating the microstructural inhomogeneity of deformation of metals by modeling. The method includes the measurement of deformations of metal according to meshes of a dividing grid with small base and the calculation of the distribution parameters of microdeformations in model representation. It is shown that the modeling method makes it possible objectively to evaluate the microinhomogeneity of deformation of metals independently of the chosen mesh size of the dividing grid. New structural characteristics are introduced: the base and wave of variation expressing the degree of crumbling or amalgamation of metal grains by inhomogeneity of deformation.Translated from Problemy Prochnosti, No. 7, pp. 40–44, July, 1991.     

水三相点复现的不确定度评定

水三相点是开尔文热力学温度的唯一基准点，也是ITS-90国际温标重要的定义固定点。因此，水三相点不确定度分析对整个温标的建立、温度量值传递起着至关重要的作用。近3年来，中国计量科学研究院研制出一系列高质量的水三相点容器，加强了水三相点的研究，为不确定度的分析提供了更为可靠的实验依据。同时，不确定度的分析也是客观评价新研制容器性能的一个重要指标。因此，根据实验结果对新研制容器所复现的水三相点进行了不确定度评定。评定结果表明，其扩展不确定度为0．16mK(k=2．69，P=0．99)。