纳米低温保护剂玻璃化过程中热学性质的研究

本文利用差示扫描量热仪(DSC)对含有羟基磷灰石(HA)纳米颗粒的丙三醇溶液玻璃化过程中的主要热学性质进行了测定。其中包括玻璃化与反玻璃化温度的测定,玻璃化过程中比热的测定。结果表明加入HA纳米颗粒后的丙三醇溶液的反玻璃化温度(Td)表现出明显的上升趋势,当溶液浓度高于50%时玻璃化温度(Tg)也稍有升高;加入纳米颗粒后溶液在整个玻璃化过程中比热明显减小,并且减小程度与HA颗粒浓度及粒径大小均表现出一定的非线性关系。     

纳米微粒对低温保护剂比热容的影响

为了研究纳米微粒对低温保护剂热力学性质的影响,实验利用差示扫描量热仪(DSC)测量了加入羟基磷灰石(HA)纳米微粒的丙三醇低温保护剂溶液(浓度为50%)比热容的值。实验结果表明:当加入HA纳米微粒质量分数为0.1%时,其溶液的比热容的值有略微的下降。但是当加入的纳米微粒质量分数提高到0.5%时,溶液的比热容的值发生了比较明显的下降。因为比热容与热扩散系数成反比,所以小的比热容能提高降温速率。针对实验中的比热容的变化,作者尝试做出了一些理论解释。     

纳米ZnS:Cd的光致发光特性

研究了Cd^2 掺杂的ZnS纳米晶的光致发光特性,结果表明,当Cd的掺杂量较低时（≤5%,摩尔分数）,ZnS纳米晶试样的荧光强度显著提高,Cd的掺杂量为0.5%时,掺杂试样的相对荧光强度约为未掺杂试样的5倍,发射光谱明显宽化,随着Cd含量的提高,试样的激发光谱（350nm→488nm）和发射光谱（由蓝→绿→红）红移,当Cd含量≥5%时,其发射光谱与CdS纳米晶一致,但荧光强度比CdS纳米晶高。XRD分析显示,掺杂试样的晶格结构由Cd的掺杂量决定。     

改性纳米HA对PLA-PBAT共混体系结晶与流变性能的影响

采用熔融共混挤出法制备改性纳米羟基磷灰石（HA）/聚乳酸（PLA）-聚己二酸丁二酯-对苯二甲酸丁二酯（PBAT）复合降解材料,利用差示扫描量热仪（DSC）、流变仪、电子拉伸机、扫描电镜（SEM）等,对其结晶、流变行为、力学性能、冲击性能、表面结构等进行了研究。DSC结果表明：随着改性纳米HA添加量的增多,HA/PLA-PBAT共混体系的玻璃化转变温度先升高后下降;冷结晶温度逐渐下降,降低了13℃,结晶能力有所提高;结晶度由24.33%增加到33.47%。流变行为显示共混体系黏度随剪切速率的增大而减小,属非牛顿流体。此外,随着改性纳米HA的增多,HA/PLA-PBAT共混体系储存模量和损耗模量逐渐减小;屈服强度、缺口冲击强度、拉伸强度先增大后减小,当共混体系中改性纳米HA添加量为2%（80/20/2）时,达到最大值。SEM观察发现,少量改性纳米HA可以均匀分散在PLA-PBAT基体中并能显著提高其韧性。     

纳米SiC/低密度聚乙烯复合材料的空间电荷与电导特性

利用熔融共混法制得不同纳米SiC质量分数（0.5%、2.0%、3.0%）的纳米SiC/低密度聚乙烯（LDPE）复合材料,研究了添加纳米SiC颗粒对LDPE介电性能的影响。利用SEM观测了纳米SiC颗粒的分散特性,利用电声脉冲（PEA）法测得40 kV/mm场强作用下纳米SiC/LDPE复合材料的空间电荷分布特性。利用热刺激电流（TSC）进一步验证纳米SiC添加能够提高LDPE的陷阱浓度。结果表明:纳米SiC颗粒能够均匀地分散在LDPE中,未出现较大的团聚现象。纳米SiC质量分数为0.5%、2.0%和3.0%的纳米SiC/LDPE复合材料空间电荷注入量明显低于LDPE。短路600 s后的残留空间电荷密度远小于LDPE。纳米SiC/LDPE复合材料的空间电荷注入量与电导率均随着纳米SiC的增加而减少。纳米SiC质量分数为3.0%的纳米SiC/LDPE复合材料场强非线性系数为2.6,远小于LDPE的4.3。TSC曲线表明纳米SiC/LDPE复合材料内部制造了大量的陷阱,抑制了载流子在材料内部的输运,从而阻碍了空间电荷的迁移和积聚。      

亲水性聚氨酯复合材料的制备与表征

选用湿态纳米羟基磷灰石（HA）与脂肪族聚氨酯（PU）为原料,采用溶液共混法和溶剂挥发法制备了亲水性羟基磷灰石/聚氨酯（HA/PU）纳米复合材料,并采用SEM、吸水实验和力学实验等方法对该复合材料的形貌和性能进行了研究。结果表明磷灰石晶体以纳米状态均匀地分布在PU基质中,过高含量的纳米HA易使纳米粒子团聚,不利于其在PU基体中的均匀分散;在制备PU的多元醇原料中引入亲水性较强的聚乙二醇,可提高PU表面和整体的亲水性;随着硬段含量的增加,复合材料的拉伸强度和弹性模量呈上升趋势,断裂伸长率下降;随着软段中聚乙二醇含量的升高,弹性模量大幅下降,拉伸强度和断裂伸长率先升高后下降;纳米HA的添加可同时提高复合材料的拉伸强度和断裂伸长率,当纳米HA的质量分数为30%时,复合材料的综合力学性能达到最佳。     

油酸修饰PbS纳米微粒的原位合成与抗磨性能研究

将纳米材料作为润滑添加剂已经成为当前摩擦学研究的热点.为了制备具有良好抗磨性和分散性的纳米添加剂,对油酸修饰PbS纳米微粒的合成方法与润滑性能进行了研究.在液体石蜡中原位合成了油酸修饰的PbS纳米微粒,将其在离心机中离心后可获得稳定的溶液.采用红外光谱、透射电子显微镜(TEM)对产物结构和形貌进行了表征,利用四球摩擦磨损试验机对其作为润滑油添加荆的抗磨性能进行了评价,并用扫描电子显微镜(SEM)对磨斑表面形貌进行了观察.在试验基础上,探讨了纳米微粒在溶液中的稳定机制.结果表明,原位合成的PbS微粒表面有油酸修饰层存在,从而使其在液体石蜡中具有良好的分散性能,粒度小于15nm,油酸修饰的PbS纳米微粒作为添加剂在液体石蜡中的添加量为0.3%(质量分数)时的磨斑直径最小,磨斑表面光滑平整.     

PVDF/FEP/ZnO复合涂层的制备及防垢性能研究

为了解决金属表面的结垢问题,以聚偏氟乙烯（PVDF）和聚全氟乙丙烯（FEP）为原料,通过添加不同含量的纳米ZnO制备了PVDF/FEP/ZnO复合涂层,研究了纳米ZnO添加量对复合涂层疏水性能和防垢性能的影响。通过接触角测量仪、扫描电子显微镜（SEM）和X射线粉末衍射仪（XRD）对涂层进行了表征。结果表明：纳米ZnO的添加量为5.0%（质量分数）时,PVDF/FEP/ZnO复合涂层的表面自由能为8.6 mJ/m²,水接触角为114.8°;PVDF/FEP/ZnO复合涂层在过饱和碳酸钙溶液中结垢336 h后,其表面的碳酸钙结垢量仅为环氧涂层的72%,且文石和球霰石的摩尔分数之和达到了91.4%,表明复合涂层具有优良的防垢性能,在防垢领域具有较好的应用前景。     

纳米低温保护剂导热系数研究

用瞬态热线法测量了SiO2纳米粉体加入到浓度为10%、20%、30%、40%、50%的丙三醇溶液中制备成的纳米低温保护剂在260K~290K下的导热系数,研究纳米低温保护剂导热系数与纳米颗粒含量、保护剂浓度以及温度的关系。结果表明：随着纳米颗粒的添加量增多（0.5g/L-1g/L),甘油溶液导热系数增大;甘油浓度从10%升高到50%时,纳米低温保护剂导热系数增加率也随之提高,从0.4%提高到6.8%;纳米低温保护剂导热系数随温度降低而减小,当温度低于260K后,纳米颗粒对保护剂导热系数几乎无影响。建议应用在解冻和复温过程中。     

“一步法”制备纳米相丝素蛋白/羟基磷灰石生物复合材料

系统分析了羟基磷灰石（HA）的制备方法和丝素蛋白纤维（SF）的溶解方法,提出一种制备纳米丝素蛋白/羟基磷灰石生物复合材料（SF/HA）的新型反应复合方法——“一步法”。并对由“一步法”制得的SF/HA分别进行了钙磷比测定、红外光谱测试、透射电镜观察和X射线衍射测试。结果表明：SF/HA中的钙磷比是1.6692,与标准HA中的钙磷比1.67一致;SF/HA中同时含有SF和HA中各自的官能团;SF/HA的晶粒横向尺度小于100 nm,SF/HA呈针状或柱状晶粒, SF和HA能够形成复合; SF/HA的晶型属于六方晶系, 当SF在SF/HA中所占质量分数为10%时,晶胞参数a=b=9.0319 A,c=7.0148 A,沿c轴方向平均晶粒尺寸是230.7645 A。“一步法”制备SF/HA具有合理性和可行性。     

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.     

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.     

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.     

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)。