硅酸铝- 硅灰石复合粉体材料的制备及其在聚丙烯中的应用

以硅灰石为原料,以硫酸铝和水玻璃为包覆剂,采用化学沉淀法,制备了一种纳米硅酸铝- 硅灰石复合粉体材料;用氨基硅烷对该材料进行表面改性后填充聚丙烯制备了聚丙烯复合材料。采用 SEM、BET氮吸附比表面积仪、粒度仪、白度仪、XRD、EDX、FTIR等测试方法对复合及表面改性粉体材料进行了表征,并探讨了氨基硅烷改性复合粉体的机制。结果表明：硅灰石表面均匀地包覆了一层纳米硅酸铝,白度由90.5提高到92.5,比表面积由1.41m2/g提高到4.78m2/g,晶粒平均尺寸为54 nm;填充 PP质量分数40%的改性复合粉体可以使纯PP的拉伸强度由17.81 MPa 提高到 21.97 MPa,弯曲强度由23.72 MPa 提高到39.20 MPa,热变形温度由65.7℃ 提高到94.3℃。     

硅丙乳液包覆Mg(OH)2核壳结构纳米粒子的制备与表征

为有效提高Mg(OH)_2纳米粒子在硅丙乳液中的相容性与分散稳定性,在油酸修饰Mg(OH)_2纳米粒子的基础上,以甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸与乙烯基三乙氧基硅烷为共聚单体,通过乳液聚合法制备出具有核壳结构的硅丙乳液包覆Mg(OH)_2复合材料。利用傅里叶变换红外光谱仪(FTIR)、X射线衍射仪(XRD)、透射电子显微镜(TEM)等测试手段对样品结构、形貌进行了表征。通过燃烧实验,研究了硅丙乳液包覆Mg(OH)_2纳米粒子对水性防火涂料阻燃性能的影响。结果表明,油酸通过酯化作用修饰在Mg(OH)_2纳米粒子表面,借助油酸分子中双键结构,丙烯酸类混合单体在纳米Mg(OH)_2表面完成聚合过程,形成以Mg(OH)_2纳米粒子为核、硅丙乳液为壳的复合材料。XRD与热分析表明经硅丙乳液包覆的纳米Mg(OH)_2晶体结构与热稳定性能未受影响。此外,掺杂0.1%(质量分数)的硅丙乳液包覆Mg(OH)_2可使水性防火涂料阻燃时间延长至113 min,较未掺杂水性涂料阻燃时间(91min)提高约23%。     

锑掺杂氧化锡-硅灰石复合粉体的制备与表征

为了改善硅灰石的导电性,对硅灰石粉体的表面包覆改性进行研究;以硅灰石粉为原料,四氯化锡和三氯化锑为沉淀包覆剂,采用化学沉淀法制备锑掺杂氧化锡-硅灰石复合抗静电材料;研究不同工艺条件对该复合粉体体积电阻率的影响,采用透射电子显微镜、X射线能量色散谱、白度仪、粒度仪、比表面积仪等进行表征。结果表明,包覆后硅灰石白度由91.7%减小为90.5%,中位粒径由10.81μm增大为11.46μm,比表面积由1.406 8 m2/g增大为3.653 2 m2/g,体积电阻率由3.36×1010Ω·cm减小为0.85×105Ω·cm。     

液相沉积法制备氢氧化镁包覆碳微球复合阻燃材料

以碳微球(CMSs)、氢氧化钠和氯化镁为原料,采用液相沉积法制备了Mg(OH)_2/CMSs复合阻燃材料,通过场发射扫描电镜(SEM)和X射线衍射仪(XRD)分析了材料的微观形貌和结构;并结合Mg(OH)_2/CMSs复合阻燃材料与聚对苯二甲酸乙二醇酯(PET)共混制备Mg(OH)_2/CMSs/PET复合材料,通过数显氧指数测试仪分析其阻燃性能。结果表明,通过液相沉积法Mg(OH)_2包覆在CMSs表面,且包覆效果较好;Mg(OH)_2/CMSs复合阻燃材料燃烧时分解生成的氧化镁(MgO)、水和残余炭层,使得Mg(OH)_2/CMSs/PET复合材料的极限氧指数由PET的21.0%增加到27.5%,并具有优良的抑烟性和抗熔滴性,提高了PET材料的阻燃性能。     

超细空心微珠表面修饰碳酸钙的制备与表征

采用表面沉积法对超细空心微珠进行无机修饰,在空心微珠表面形成了均匀且不连续的CaCO3膜,采用SEM、EDX、XRD等方法对修饰前后可能修饰微珠进行了分析和表征。结果表明,修饰后空心微珠外观颜色由灰黑色变为灰白色;修饰前空心微珠粒径为1.8μm,修饰后空心微珠平均粒径为1.94μm;修饰后空心微珠的比表面积为2.4m2/g,增大幅度为26.3%;修饰后空心微珠密度增大,通过公式测算修饰后空心微珠的壁厚增加了30%;最后采用分散剂将空心微珠分散到500SN基础油中,发现修饰后空心微珠在基础油中的分散稳定性能明显优于原始空心微珠。     

纳米结构氧化镁空心球壳的制备及吸附镍离子性能研究

以Pickering乳液的液滴为模板制备纳米结构MgO空心球壳,用SEM、XRD、BET等对空心球壳进行了表征,探讨了其形成机理,并考察了纳米结构MgO空心球壳对水中Ni2+的吸附性能。结果表明,MgO空心球壳为方镁石结构,比表面积为28m2/g;其平均粒径为63μm,表面由平均宽度为65nm的纳米片层构成。Pickering乳液油水界面的部分MgO通过水化反应转变成Mg(OH)2,复合在未反应的MgO粒子上,形成MgO/Mg(OH)2空心球壳;MgO/Mg(OH)2空心球壳经焙烧后得到纳米结构MgO空心球壳。当纳米结构MgO空心球壳用量为0.4g/L时,溶液(初始浓度25mg/L)中Ni2+的去除率为98.3%。     

粉煤灰空心微珠的Co-Ni-P化学镀及镀层的吸波性能

为了实现吸波材料的薄型化及轻量化,采用化学镀工艺对粉煤灰空心微珠(5μm级)进行表面电磁改性,制备出"核-壳"结构新型轻质复合粉体吸波材料,探讨了Co-Ni-P化学镀工艺参数对吸波性能的影响.借助SEM,EDS和微波矢量网络分析仪研究了施镀工艺参数对镀层形貌、成分与吸波性能的影响.结果表明,空心微珠表面镀层由粒径0.5...     

空心微珠表面化学沉积Co—P合金研究

利用化学镀工艺在粉煤灰空心微珠表面均匀、完整地包覆磁性Co-P合金层,成功制备出新型轻质的复合导电粉体.使用XRD、EDS、SEM和镶嵌金相的方法对样品进行形貌观察和分析表征,并讨论了镀液温度、pH值和稳定剂浓度对沉积效率的影响.结果表明,空心微珠经过敏化-活化的表面预处理后,利用化学镀方法可以得到均匀、包覆完整的Co-P合金层,并且出现了新的晶化相α-Co单质.T=90℃、pH=10.2和加入适量的硫脲是使反应良好进行的最佳工艺参数.     

空心微珠铁氧体复合粉体的改性与吸波性能

研究了柠檬酸盐溶胶-凝胶方法制备空心微珠-钡、锶、钴镍钡铁氧体复合粉体的微观形貌, 采用化学添加剂改善铁氧体的包覆性能. SEM、EDS分析表明铁氧体在空心微珠表面的包覆状态与铁氧体种类无关; 在前驱体中加入乙二醇或聚乙二醇可以使铁氧体对空心微珠的包覆更加完整、牢固致密. 用网络分析仪测试了C波段5.0～6.5GHz、X波段8.2～12.4GHz、Ku波段12.5～18.0GHz内1.8mm厚铁氧体空心微珠复合粉体制备的吸波涂层的微波损耗. 试验表明：铁氧体空心微珠复合粉体具有良好的电磁吸波性能, 吸波涂层在5～18GHz内微波反射损失总体上大于单纯铁氧体涂层; 加入乙二醇或聚乙二醇有助于提高涂层的吸波效果.     

MgO/Mg（OH）2复合空心球壳的制备及缓释性能的研究

以Pickering乳液液滴为模板,通过液滴表面水合作用制备出MgO/Mg（OH）_2复合空心球壳,通过SEM、XRD等手段进行表征,讨论了空心球壳形成机理,并研究了MgO/Mg（OH）_2复合空心球壳对阿维菌素微胶囊的缓释作用,结果表明,MgO/Mg（OH）_2复合空心球壳形貌完整,粒径分布均匀,平均粒径为62μm。水合过程中部分MgO转变成Mg（OH）_2,并优先复合在未反应的MgO粒子上,形成MgO/Mg（OH）_2复合空心球壳。以MgO/Mg（OH）_2复合空心球壳为壁材的阿维菌素微胶囊具有良好的缓释性能。     

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)。