改善喷射沉积多孔材料开裂行为工艺的研究

介绍了多孔金属材料的致密化过程及塑性变形,分析了其轧制开裂行为规律,研究了多孔金属材料在外框限制轧制中的轧制过程及避免多孔材料开裂的工艺措施.     

Synthesis of porous–acoustic absorbing systems by an evolutionary optimization method

Topology optimization is frequently used to design structures and acoustic systems in a large range of engineering applications. In this work, a method is proposed for maximizing the absorbing performance of acoustic panels by using a coupled finite element model and evolutionary strategies. The goal is to find the best distribution of porous material for sound absorbing panels. The absorbing performance of the porous material samples in a Kundt tube is simulated using a coupled porous–acoustic finite element model. The equivalent fluid model is used to represent the foam material. The porous material model is coupled to a wave guide using a modal superposition technique. A sensitivity number indicating the optimum locations for porous material to be removed is derived and used in a numerical hard kill scheme. The sensitivity number is used to form an evolutionary porous material optimization algorithm which is verified through examples.     

不对称多孔金属材料的研究进展

不对称多孔金属材料是一种性能优良的新型多孔材料,这种结构实现了现代多孔材料过滤行业的高精度、大流量生产要求,同时良好的力学性能使得不对称多孔金属材料的应用较陶瓷膜的应用更为广泛。本文综述了不对称多孔金属材料研究概况,并就不对称金属多孔材料的发展趋势作了相应预测。     

Selective Absorption of Hydrophobic Cations in Nanostructured Porous Materials from Crosslinked Hydrogen‐Bonded Columnar Liquid Crystals

A nanostructured porous material is obtained by crosslinking of a self‐assembled system consisting of columnar liquid crystals with polyamines and removal of the template. For this purpose, a columnar liquid crystal with liquid crystalline properties at room temperature is synthesized and fully characterized. The orthogonal self‐assembly of the columnar liquid crystal with polyamines (i.e., PPI dendrimers) results in the formation of nanosegregated structures. When crosslinked by photopolymerization a nanostructured crosslinked material is obtained. Partial removal of the polyamine template leads to a nanostructured porous material, which is characterized and the absorbent properties are investigated. The polarity of the porous material is probed and the porous material is used for the selective absorption of cationic dye molecules.     

The relationship between the elasticity tensor and the fabric tensor

An algebraic relationship between the fourth rank elasticity tensor of a porous, anisotropic, linear elastic material and the fabric tensor of the material is considered. The fabric tensor is a symmetric second rank tensor which characterizes the geometric arrangement of the porous material microstructure. In developing this result it is assumed that the matrix material of the porous elastic solid is isotropic and, thus, that the anisotropy of the porous elastic solid is determined by the fabric tensor. It is then shown that the material symmetries of orthotropy, transverse isotropy and isotropy correspond to the cases of three, two and one distinct eigenvalues of the fabric tensor, respectively.     

多孔材料的流体动力特性

多孔材料广泛应用于消声降噪、过滤等工业领域,笔者针对较高消声效果的PVF多孔消声材料喷注的外部流场特性进行了较为详细的实验研究, 对不同厚度的材料的外部流动速度、湍流量、声场和压力分布进行了细致的测量,得出多孔材料的出流是由不同方向的普通微射流和微射流的汇聚扩散组成的结论,证明流体经多孔材料出流后的噪声是由外部扩散流场的湍流所决定的。多孔材料的作用在于:(1) 总压的降低和出流面积的缩小;(2) 由于多孔材料的不同方向微射流的相互耦合作用、引起外部流动特性的改变。气动消声材的选择上要注重其对出流流场的改善,这是达到良好消声效果的根本所在。     

活化剂对焦煤基多孔碳制备的影响及其在锂硫电池中的应用

煤炭作为一种来源广泛的非金属矿物,是制备大量多孔碳的理想原料。本文以1/3焦煤为原料,NaOH和KOH为活化剂,制备了多孔碳,并研究了硫/多孔碳复合正极材料的电化学性能。结果表明:采用NaOH和KOH单独活化时制备的多孔碳比表面积很大,分别为1 649 m2/g和1 867 m2/g,而采用NaOH和KOH混合活化制备的多孔碳比表面积大幅度下降,当NaOH与KOH质量比为1:1活化时多孔碳的比表面积最小,为290 m2/g。电化学测试表明,NaOH与KOH质量比为1:1混合活化的硫/多孔碳正极材料的电性能优于NaOH和KOH单独活化的硫/多孔碳正极材料,0.2 C下首次放电比容量为790 mA·h/g,库仑效率为93.16%,100次循环后放电比容量为740 mA·h/g。还分析讨论了煤基多孔碳孔径分布对电化学性能的影响。      

包装用泡沫材料的多孔弹性模型

包装用泡沫材料是一种多孔隙的、呈现超弹性本构行为的橡胶类材料.引入了描述硅泡沫的多孔介质模型,针对泡沫材料弹性本构行为以及由于多孔隙的结构特征所导致的可压缩性,并考虑孔隙度对变形性能的影响,提出了解耦为等容部分和体积变形部分的应变能函数的具体形式,从而获得泡沫材料的本构方程.     

多孔泡沫金属磁流变液阻尼材料及其力学性能研究

基于多孔泡沫金属的结构性能,研制一种新型的磁流变液阻尼材料,并搭建测试系统,研究其力学性能。在该材料中,磁流变液由于毛细管力的作用储存在多孔泡沫金属里面,在磁场作用下被抽出到剪切间隙内并产生磁流变效应;利用搭建的测试系统,研究多孔泡沫金属的材料、外加电流、剪切间隙和剪切应变率等参数对多孔泡沫金属磁流变液阻尼材料力学性能的影响,结果表明,设计的多孔泡沫金属磁流变液阻尼材料可产生明显的磁流变效应,在相同情况下,采用多孔泡沫金属铜时,多孔泡沫金属磁流变液阻尼材料具有最大的剪切转矩。     

On the sensitivity of generic porous optical sensors

A porous material was considered as a platform for optical sensing. It was envisaged that the porous material was infiltrated by a fluid that contains an agent to be sensed. Changes in the optical properties of the infiltrated porous material provide the basis for detection of the agent to be sensed. Using a homogenization approach based on the Bruggeman formalism, wherein the infiltrated porous material was regarded as a homogenized composite material, the sensitivity of such a sensor was investigated. For the case of an isotropic dielectric porous material of relative permittivity ε(a) and an isotropic dielectric fluid of relative permittivity ε(b), it was found that the sensitivity was maximized when there was a large contrast between ε(a) and ε(b); the maximum sensitivity was achieved at midrange values of porosity. Especially high sensitivities may be achieved for ε(b) close to unity when ε(a)>1, for example. Furthermore, higher sensitivities may be achieved by incorporating pores that have elongated spheroidal shapes.     

Infrared ellipsometry characterization of porous silicon bragg reflectors

We investigate porous silicon Bragg reflectors in a nondestructive manner using variable angle-of-incidence infrared spectroscopic ellipsometry. In addition to the thickness, volume porosity, inhomogeneity, and optical anisotropy, properties of the solid content of the porous material are investigated in terms of dielectric function and surface chemistry. The material was found to have positive birefringence. The high sensitivity of the technique is employed to detect and identify infrared resonant absorptions related to different Si-H as well as Si-O-Si vibrational modes. The average electrical resistivity of the solid content of the porous material is determined to be 0.03 Omega cm, which is larger than the corresponding bulk value of 0.019 Omega cm. Furthermore the average carrier concentration in the porous material shows a decrease from 6.2 x 10(18) cm(-3) to 4 x 10(18) cm(-3).     

有机大分子在有序多孔材料制备中的应用

多孔性材料广泛用于阻隔材料、结构材料、催化剂材料、分离与吸附等领域。随着纳米技术的迅速发展，高度有序的多孔性材料由于其在光电子、新型催化荆、高效吸附荆和分离介质、电极材料、生物医学领域种种潜在的用途而倍受瞩目。如何快速、高效地制备有序多孔材料是一项艰巨的任务。文中主要介绍有机大分子在有序多孔材料制备中的应用。     

多孔吸声材料发展现状与展望

吸声降噪在人们日常生活、设备安全以及军事领域具有重要意义，多孔材料是一类重要的吸声材料。介绍了多孔材料的吸声原理、多孔吸声材料的种类及其特性、影响多孔吸声材料吸声性能的因素等。综述了多孔吸声材料的发展现状，并对吸声材料的发展趋势做了展望。     

基于冷冻干燥法的淀粉基多孔材料制备与性能

以淀粉为主要原料、剑麻纤维为增强体、水为发泡剂、辅以甘油增塑剂,运用冷冻干燥法制备一种可全降解的环保多孔材料。对致孔机理进行了探究,理清了加工工艺流程,并对样品进行红外光谱分析（FTIR）、扫描电镜（SEM）表征及膨胀率测试。结果表明：相对于挤出法、注塑法多孔材料,冷冻干燥法多孔材料样品的泡孔尺寸较小,孔壁较厚;甘油、水和剑麻纤维的用量对淀粉基多孔材料的膨胀率存在一定的影响,随着剑麻纤维用量的提高,膨胀率逐渐增加,随着甘油及水用量的增加,膨胀率则先增大后减小;当淀粉用量为500 g时,剑麻纤维用量为250 g、甘油为200 g、水为250 g,膨胀率分别达到极大值。运用冷冻干燥法制备淀粉基多孔材料,可有效避免淀粉难以热熔加工的问题,工艺简单、设备成本低,可为淀粉基多孔材料在泡沫、凝胶等制品的实际生产提供新思路。     

表面多孔球形LiFePO4/C的制备及其电化学性能

采用一步溶剂热法合成球形LiFePO4,并进一步在饱和葡萄糖溶液中浸泡包碳形成表面多孔球形LiFePO4/C.利用XRD、SEM、HRTEM、FTIR和BET对样品的纯度、成分、晶型、形貌和孔结构进行了表征.实验结果表明:表面多孔结构使表面多孔球形LiFePO4/C拥有更大的比表面积以及更多的活性位点,并极大缩短了锂离子在充放电过程中的迁移距离,降低锂离子在材料中扩散及脱嵌阻力;在保持较高振实密度(1.36 g·cm-3)的前提下进一步提高材料的利用率以及较大倍率下的充放电性能,使表面多孔球形LiFePO4/C拥有优良的电化学性能.     

某种多孔陶瓷的消声性能试验

调研了多孔陶瓷材料在声学领域的应用，阐述了其作为吸声材料、隔声材料及消声器使用时的声学原理。基于多孔陶瓷作为消声器使用的相关研究较少，为确定影响多孔陶瓷消声性能的主要因素，在两种试验工况下对不同规格的多孔陶瓷管进行排气试验。孔隙率是表征多孔陶瓷的基本参量，它与多项物理性能存在紧密联系，为排除它的影响，选择40 %孔隙率的多孔陶瓷进行试验，结果表明壁厚越厚，消声效果越好，孔径为20 μ的多孔陶瓷管消声效果最佳。随着温度的升高，多孔陶瓷管的消声频谱特性曲线向高频移动。     

Thermo-elastic-plastic porous material undergoing thermal loading

A model for predicting elastic–plastic stresses within a surface-heated porous structure has been developed. The relevant phenomena for the moisture, pressure, temperature and displacement fields in thermo-elastic-plastic porous material are analysed. Considering mass and energy transfer processes, a set of governing differential equations is presented. The solution of the problem has been obtained with a finite difference scheme. The results demonstrate the influence of the evaporation mechanism on pressure and thermal stresses within the porous material.     

植物纤维多孔材料泡孔分布影响因素

目的分析影响植物纤维多孔材料泡孔分布的各种因素,探究泡孔结构对性能的影响,为制备泡孔均匀分布、缓冲性能良好的多孔材料提供理论基础。方法归纳总结国内外植物纤维多孔材料泡孔结构的研究进展,探讨多孔材料的发泡机理,系统地阐述成型工艺、助剂种类、助剂含量等对植物纤维多孔材料泡孔结构的影响。结果通过分析得出各种影响因素的作用规律,为进一步完善植物纤维多孔材料的制备方案,开发泡孔分布均匀、性能稳定的植物纤维发泡材料提供依据。结论通过制定科学的实验方案,可以制备出泡孔分布均匀的多孔材料,其可作为缓冲材料,在包装领域中有巨大的市场需求。     

Porous materials prepared by heating derivatives from halloysite

Halloysite clay was subjected to serious treatment by trimethylsilylation and hydrochloric acid. The resulting derivatives were heated below 1473 Kin nitrogen or air to prepare thermally stable porous materials including larger pores than those in zeolite. The trimethylsilylated halloysite resulted in a thermally stable porous material, in an amorphous state, including extremely uniform pores of 1.7 nm. Another derivative also resulted in a thermally cable porous material but consisted of very heterogeneous pores. The thermal degradation behaviour of both derivatives is discussed in detail.     

硅基含能材料爆炸性能研究

采用电化学双槽腐蚀法在P型单晶硅片表面生长多孔硅膜。通过扫描电镜（SEM）、能量色谱（EDS）对多孔硅结构参数以及多孔硅含能材料性能进行了分析,同时进行了爆炸性能测试。结果表明：采用电化学腐蚀法可以制备出20nm左右孔径的多孔硅膜;通过原位装药技术形成的多孔硅含能材料在开放空间以及热能、机械撞击、电能、激光能量刺激下发生猛烈爆炸作用。