玻璃固载TiO2/纳米纤维素复合薄膜的制备及其光催化性能

将微晶纤维素溶解于NaOH-尿素的低温溶液中形成纤维素溶液,在水浴中再生形成纳米纤维素溶液.然后将纳米纤维素溶液与TiO2(P25)混合,并添加少量的钛酸正丁酯作为交联剂形成复合溶液.将制备得到的复合溶液通过流延法固载到玻璃片表面形成玻璃固载的TiO2/纳米纤维素复合膜.通过SEM、XRD表征了复合膜的形貌与结构.将玻璃固载的TiO2/纳米纤维素复合膜在紫外光下进行光催化降解甲基橙(MO)以评估复合膜的光催化性能,研究了纳米TiO2含量对复合膜光催化性能的影响,复合膜的重复使用性能以及光降解的动力学过程.结果表明:复合膜对MO的光催化降解能力可达90％以上,与纯TiO2粉末相当,并重复使用3次光催化性能基本保持不变.复合膜对甲基橙的降解动力学符合一级动力学特征.当纳米TiO2相对于纤维素的质量分数为33.3％时,光催化活性最高,动力学速率常数为0.035min-1.     

纳米材料对阔叶纤维素包装膜性能影响的研究

采用NMMO法,以阔叶纤维素为原料制备纤维素膜,通过向铸膜液中添加经硅烷偶联剂KH-550改性的纳米SiO2,钛酸酯偶联剂改性的CaCO3以及载银TiO2材料制备纳米／纤维素复合膜。对制备纳米／纤维素复合膜微观结构采用原子力显微镜（AFM）和扫描电子显微镜（SEM）进行了表征,并结合力学性能和透氧性能测试分析了纳米材料结构和含量对膜综合性能的影响。结果表明：纳米材料的加入可以改善NMMO法纤维素膜的透氧性能,当改性纳米SiO2、改性纳米CaCO3和载银TiO2添加质量分数分别为2％、1％和1．5％时制备的纤维素纳米复合薄膜的综合性能达到最优。     

不同粒径分布的纳米二氧化钛在醋酸纤维素超滤膜中的分散性能研究

在醋酸纤维素(CA)基料中添加不同浓度经表面改性的不同粒径的纳米二氧化钛(TiO_2)粒子,其中包括平均粒径10、40nm以及这两种粒子的质量比2∶1的级配混合粒子,利用相分离法制备了无机-有机纳米复合CA超滤膜,通过测定膜的孔隙率、孔径分布、渗透性能以及膜表面的电镜扫描(SEM)表征进而研究不同粒径分布对纳米粒子在铸模液中分散性能.结果表明:在不引起纳米粒子团聚的前提下,在CA中添加的纳米粒子粒径越小,复合膜的性能越好;而级配粒子的添加量高于单一粒径粒子的添加量.当膜的渗透性能达到最佳值时,上述3种不同粒径分布的粒子添加量分别为4%、3%、5%(质量分数),而成膜后孔隙率均可达到70%以上,纯水的透水量可分别达到527、443、591L/(m~2·h).这说明颗粒级配分布促进了纳米粒子在铸模液中的分散性能.由于两种粒子混合均匀后存在粒径带双峰分布颗粒级配,在剪切条件下,纳米粒子不易因粒子表面作用引起团结,而团聚在一起的级配颗粒却容易受剪切剥离分散,从而起到促进纳米粒子在聚合物溶液中的分散作用.     

乙基纤维素/TiO2复合膜的制备及气体渗透性能

以乙基纤维素(EC)和正钛酸丁酯(TBT)为主要原料,通过溶胶-凝胶(Sol-Gel)法制备了EC/TiO2复合膜。研究了TiO2粒子在复合膜中分布形貌、复合膜的结构变化及对气体渗透和分离性能的影响。结果表明,TiO2质量分数达到25%时,微米级的TiO2粒子均匀分散在复合膜中,复合膜形成有机-无机三维网络结构,测试气体在膜中的渗透行为主要受动力学因素控制,其中H2、O2透气系数分别增大至纯EC膜的1.8倍和1.3倍,H2/N2及O2/N2分离性能略有提高。     

TiO_2/酚酞聚醚砜复合超滤膜的研究

采用浸没沉淀相转化法制备了TiO2/酚酞聚醚砜复合膜,系统地研究了溶剂种类、TiO2添加量等条件对TiO2/PES-C膜结构与性能的影响.结果表明:以DMAc为溶剂时液-液分层速度较慢,得到的超滤膜在添加TiO2前后透过性能均较好,截留率高.与不含纳米TiO2的PES-C膜相比,含TiO2的TiO2/PES-C复合膜的超滤性能、亲水性和抗蛋白污染性都有了显著的改善.当TiO2添加量小于3%时,膜表面Ti元素的含量随着TiO2添加量的增加而增加,其透过性能和抗污染性能也在提高,纳米TiO2/PES-C复合膜具有不对称的断面结构和致密的皮层,亚孔层具有更好的贯通性;当TiO2添加量超过5%时,表面明显分布有大量小孔,其断面结构则表现为皮层变厚,亚孔层消失,只存在指状大孔结构,同时膜的透过性能有所降低.在膜的抗污染试验中,通过牛血清白蛋白溶液连续运行和接触角测定实验表明,TiO2的加入有助于减缓膜在运行过程中通量的衰减,增强了膜的抗蛋白污染性和亲水性.当TiO2水溶液添加量为3%时,TiO2/PES-C复合膜的通量达到最大,亲水性最好,且具有较好的抗蛋白污染性.     

溶胶-凝胶法制备聚醚砜/TiO2杂化膜

采用溶胶-凝胶法制备聚醚砜-二氧化钛杂化膜,用TEM对铸膜液中二氧化钛分散程度进行表征,并用SEM及接触角仪对膜材料的表面及断面形态、膜材料的亲水性能进行表征.结果表明,当TiO2凝胶添加量(质量分数)达到4%时,表面明显分布有大量分布均匀的TiO2纳米粒子,其断面结构则表现为皮层变厚,亚孔层消失,只存在指状大孔结构,表现为水通量随之增大,改善了聚醚砜材料的疏水性,提高了膜的抗污染性.随着二氧化钛纳米粒子浓度的提高,由于纳米粒子的团聚现象导致其在聚合物基上不能分散均匀,当膜受到外力作用时引起膜内部应力集中,使膜力学性能下降.     

TiO2改性静电纺复合超滤膜抗污染性能的研究

膜污染是制约超滤膜广泛使用的最重要因素之一,膜污染直接影响到膜的使用寿命及膜的分离性能.本文采用静电纺丝技术制备了PET/PVA纳米纤维复合超滤膜,通过溶剂浸泡处理复合膜,将PVA纳米纤维层溶胀并交联,形成具有抗污染性能的PVA表面致密层结构,所制备的复合纳米纤维超滤膜具有水通量损失率小、通量恢复率高的优点.通过在PVA中添加不同质量分数的TiO2进一步改善膜的亲水性和抗污染性能.使用死端过滤系统过滤10 mg/L腐殖酸溶液,测试结果表明:复合膜的分离性能和抗污染性能在一定范围内随着TiO2的增加而增大.亲水性TiO2的添加能够进一步增强PVA的亲水性,对复合膜抗污染性能的提高有重要作用.但是,TiO2的添加也会增大膜表面的粗糙度,不利于膜抗污染性能的提高,因此,TiO2有一个合宜的添加限度.     

纳米TiO2/醇酸复合涂层的耐腐蚀性能研究

采用盐雾试验和电化学交流阻抗技术,研究了纳米TiO2对钢板涂层耐腐蚀性能的影响,并通过扫描电镜观察了纳米TiO2复合涂层断面形貌.研究表明,纳米TiO2复合涂层的耐腐蚀性能均优于未添加纳米TiO2涂层,当纳米TiO2添加量为1.5%(质量分数)时,涂层耐盐雾时间由420h提高到710h,涂层阻抗值也由107Ω·cm2增加至109Ω·cm2.从涂层断面观察发现,纳米TiO2添加量为1.5%(质量分数)时,颗粒较均匀分散,粘接紧密,形成较为致密的纳米复合涂层.     

磺化聚芳醚酮砜/TiO2复合质子交换膜的制备与性能

为了满足高温燃料电池对质子交换膜的要求,通过溶胶共混法制备了掺有不同含量TiO2纳米粒子的磺化聚芳醚酮(SPAEKS)/TiO2复合膜。红外光谱证实TiO2被引入到SPAEKS共聚物中。扫描电镜(SEM)照片显示,纳米级的TiO2粒子能够均匀地分散在SPAEKS共聚物基体中。通过对复合膜的性能测试发现TiO2的引入,复合膜的热稳定性、吸水率、保水能力及阻醇性能都有所提高。而且SPAEKS/TiO2复合膜的质子传导率高于SPAEKS膜,并在高温时尤为明显,能够满足高温燃料电池的需要。     

超声法制备壳聚糖/β-CD／纳米TiO2三元复合膜及其性能研究

采用水解与均匀沉淀法相结合,制备了锐钛型纳米TiO2粉末,并用十二烷基硫酸钠(SDS)对其进行了改性.以壳聚糖、β-环状糊精(β-CD)、SDS改性的纳米TiO2为成膜材料,用超声法及流延法制得分散较均匀的纳米复合膜,用UV,XRD,SEM等表征其结构.试验结果表明,其透光率和溶胀率随TiO2质量分数的增大而逐渐下降.当纳米TiO2在复合膜中的质量分数为2%时,复合膜具有良好的抗张强度和抗茵性能.     

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)。