共查询到20条相似文献,搜索用时 31 毫秒
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多孔材料具有孔隙率高、比表面积大、导热系数低、体积密度小及化学性质稳定等优点,在吸附与分离、催化剂载体、隔热材料、能量储存、传感器等领域拥有广阔的应用前景。基于孔直径的大小可将多孔材料分为三类:孔径大于50nm的大孔材料(Macroporous materials),孔径介于2~50nm的介孔材料(Mesoporous materials)和孔径小于2nm的微孔材料(Microporous materials)。但是,由于孔径的限制,这三类材料的应用均存在一定的局限性。多级孔材料兼具通透性好、孔隙结构发达、体积密度小、比表面积和孔体积大等优点,打破了传统单级孔材料孔结构单一的局限,因此越来越受到研究人员的关注。然而,多级孔材料在制备中仍存在较多问题。例如,其合成过程通常会涉及到两种及两种以上的方法,制备工艺复杂;现有的多级孔材料的制备成本高,孔结构难以控制。因此,研究者们主要从优化多级孔材料的制备工艺以及降低生产成本等方面入手,制备出孔径均一且可控的多级孔材料。多级孔材料主要有大孔-介孔材料(Macro-mesoporous materials)、微孔-介孔材料(Micro-mesoporous materials)以及含有两种或多种不同孔径的介孔-介孔材料(Meso-mesoporous materials)。大孔-介孔材料常见的制备方法有模板法、发泡法、溶胶-凝胶法及熔盐法等;微孔-介孔材料的主要制备方法有化学活化法、模板法和水热法等;介孔-介孔材料的制备方法主要有水热法、模板法、溶胶-凝胶法及自组装法等。本文综述了近年来多级孔材料的最新研究进展,分别对大孔-介孔、微孔-介孔及介孔-介孔材料的制备方法进行了介绍,并简要分析了未来本领域研究的发展趋势。 相似文献
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有机/纳米二氧化钛杂化材料的合成与表征 总被引:1,自引:0,他引:1
采用溶胶 -凝胶聚合法 ,制备了稳定的纳米二氧化钛 /有机聚合物改性的杂化材料。研究了不同的反应方法对该杂化材料的粒子形状、溶液稳定性和光折射率的影响。红外光谱和透射电镜分析表明 :该材料是由内部的Si -O -Ti键和表面有机聚合物组成的 ,并且有纳米尺寸的结构。该杂化材料在甲苯 /丁醇组成的混合溶剂中具有良好的稳定性 相似文献
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G.R. Liu 《Composite Structures》1997,40(3-4):313-322
A new method of rule-of-mixture is presented for predicting the mechanical properties of fiber- and particle-reinforced composite materials. The composite material is composed through a hypothetical process in which the matrix is reinforced one-by-one with reinforcing materials (fibers or particles). The mechanical properties of the composed material are obtained step-by-step using the cylinder model for fiber-reinforced materials and the sphere model for particle-reinforced materials. Results obtained by the present method are compared with those of other methods and experimental results. It is found that, for the longitudinal modulus, the present method gives equally good prediction as other methods. For the transverse modulus and shear modulus, the results obtained by the present method show better agreement with experimental results. 相似文献
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钛酸锂(Li4Ti5O12)是一种“零应变”材料,在充放电过程中不会形成锂枝晶,消除了过充电对电池的安全隐患。本文系统的介绍了钛酸锂的制备方法和结构改性。在钛酸锂的合成方面固相法相对较为简单,生产效率高,较为适合工业中大批量生产,溶胶凝胶法则较为复杂,但得到的钛酸锂材料相对来说纯度、结晶度也比较高。在钛酸锂材料改性方面,纳米化、球化、多孔化都是以增大材料表面积提高材料的比容量;金属及离子掺杂改性主要是为了提高材料的导电性,其中不同的金属离子对材料的比容量有不同的影响。材料的表面复合改性是一种综合改性手段,是在提高材料比容量的同时提高材料导电性的一种改性手段。 相似文献
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一种测定晶体取向及其分布的简便XRD方法 总被引:5,自引:0,他引:5
提出了旋转定向测试法,其原理是使试样的在粉末X射线衍射仪上进行θ扫描的同时绕其端面法线自转,增加了晶面法线通过衍射平面的机会。通过这种方法可直观地区分取向多晶,准单晶或者单晶体,评定研制过程中准单晶和择优取向材料的晶体品质,确定单晶,准单晶及择优取向等材料的晶面相对宏观端面的晶向偏离角和取向分散度,还可对单晶体材料进行三维晶面定向。旋转定向法测试晶体取向具有快速简便,一机多用,精度高等优点,在电子、光学、磁性,机械等材料研究领域具在广泛的应用。 相似文献
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对国内外层状二氧化锰的制备方法及相关锰氧化物的应用现状进行综述,详细总结层状二氧化锰主要的制备方法,如固相反应法、水热合成法、溶胶-凝胶法、液相氧化-还原法等,对层状二氧化锰在锂电池电极材料、阳离子交换材料、吸附材料及污染物处理材料等领域的应用进行概述,并对其未来的发展趋势进行展望。结果认为:层状二氧化锰的制备与使用仍是今后一段时间内重点发展对象。固相法是在实际生产和研究实验中应用最多的一种方法,而液相法则因低投入、低能耗、污染小,是值得大力发展和推广的制备工艺路线。制备技术的不断成熟将使层状二氧化锰具有更广阔的应用前景。 相似文献
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水泥基材料中氯离子的传输是一个非常复杂的过程。在介绍水泥基材料氯离子传输机理及常用试验方法的基础上,综述了碱激发材料氯离子传输性能测试方法及影响因素。碱激发材料氯离子传输性能受激发剂种类的影响,改变矿渣掺量、碱掺量和水玻璃模数能不同程度地改变体系的氯离子传输性能。快速氯离子渗透试验结果受孔溶液化学组成影响,碱激发材料孔溶液碱性高、化学组成更复杂,孔溶液影响更显著,所以该方法不适用于评价碱激发材料氯离子传输性能。自然扩散试验因时间长而不常用。非稳态电迁移试验是目前快速测试水泥基材料中氯离子传输性能最好的方法,但由于碱激发材料与普通水泥基材料的碱度不同,其变色边界氯离子浓度也会不同,将该方法用于评价碱激发材料时,还需进一步研究测试样品的准备和硝酸银变色边界氯离子浓度。 相似文献
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Mechanical fracture properties of specimens taken from refractory materials of different brittleness are described using the wedge splitting method according to Tschegg in uniaxial and biaxial load cases. Notch-tensile strength, fracture energy and the characteristic length were determined. Fracture energy under a uniaxial load is more or less the same for all materials; if a load becomes biaxial, values fall to approx. 70% in materials with reduced brittleness and to 40% in brittle materials, compared to uniaxial values. The sensitivity against crack propagation (lch) changes insignificantly under both uniaxial and biaxial loading of brittle and brittleness-reduced materials. 相似文献
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A. V. Stepanov D. A. Stepanov S. A. Nikitina T. D. Gogoleva M. G. Grigor’eva L. S. Bulyanitsa Yu. A. Panteleev M. V. Pen’kin E. V. Pevtsova V. D. Domkin 《Radiochemistry》2006,48(2):198-203
A spectrophotometric precision method with internal reference [1, 2] was applied to analysis of straight Pu solutions for certifying Pu reference materials and for studying the PuO2 solubility in the framework of developing methods for accounting and control of nuclear materials. In the context of the activities mainly concerned with certification of reference materials, a two-channel spectrophotomer and the corresponding technique were further improved in order to decrease the error of the method. This allowed the random component of the relative error of the method to be decreased from 0.1 to 0.04% at the confidence level p = 0.95 and the number of degrees of freedom f = 25. The fixed component of the error of the method was studied in relation to impurities of U, Np and corrosion products of structural materials. Also, the extent of Pu oxidation during sample preparation was studied as influenced by the fluoride ion. The revealed lack of such influence within the limits of the study indicates that the method is suitable for analysis of Pu in mixed solutions. 相似文献
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在物流管理中运输问题非常重要,物资要实现实体转移,都需要通过运输来实现;而要达到运输费用的最小,必须使物资的需求具有前瞻性.根据现代经济学中的预测方法,结合企业物资历年实际需求情况,运用时间序列的趋势移动平均法、自适应滤波预测法、灰色预测法,利用层次分析法确定相应的权重后对未来物资需求进行组合预测,并应用于物资运输管理中,使运输费用达到最小,从而使运输管理更具有现实性及可操作性. 相似文献
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氧化锌由于氧空位等本征缺陷的存在表现出n型半导体的性质,该性质使得氧化锌纳米颗粒可以用作导电材料。为了提高纳米氧化锌颗粒的电导率,通过简单、经济、新颖的液相反应法和喷雾热解技术对纳米氧化锌进行Al掺杂,并分析了掺杂工艺、电导测试方法对纳米氧化锌导电颗粒电阻率的影响。 相似文献
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In this work, the uniform design method was applied to arrange the experimental scheme for optimizing formulation of friction materials. The friction and wear of the friction materials based on the optimized formulation was carried out on a constant speed friction tester (JF150D-II), using pad-on-disc contact mode against gray cast iron disc. The worn surfaces of the friction materials were examined by scanning electron microscopy (JSM5310) and the friction mechanism was discussed. The results showed that the uniform design method was appropriate for finding the optimum formulation of the friction materials with better properties. Compared with two conventional friction materials, the friction materials based on the optimized formulation possessed higher and stable friction coefficient and higher wear resistance, even at the disc temperature of 350°C. The adhesion, strain fatigue and abrasive wear were the main wear mechanisms of the friction materials. Tribo-chemical phenomenon and plastic deformation existed on the worn surface layer. 相似文献
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Michelmore A Mierczynska A Poh Z Goreham RV Losic D Short RD Vasilev K 《Nanotechnology》2011,22(41):415601
Nanoporous alumina (PA) arrays produced by self-ordering growth, using electrochemical anodization, have been extensively explored for potential applications based upon the unique thermal, mechanical and structural properties, and high surface-to-volume ratio of these materials. However, the potential applications and functionality of these materials may be further extended by molecular-level engineering of the surface of the pore rims. In this paper we present a method for the generation of chemical gradients on the surface of PA arrays based upon plasma co-polymerization of two monomers. We further extend these chemical gradients, which are also gradients of surface charge, to those of bound ligands and number density gradients of nanoparticles. The latter represent a highly exotic new class of materials, comprising aligned PA, capped by gold nanoparticles around the rim of the pores. Gradients of chemistry, ligands and nanoparticles generated by our method retain the porous structure of the substrate, which is important in applications that take advantage of the inherent properties of these materials. This method can be readily extended to other porous materials. 相似文献