Experimental and numerical investigations on compressive properties of porous twisted wire materials

Wire diameter, sintering parameter, and porosity have great influences on porous structures and compressive properties of the stainless steel porous twisted wire materials with 30–92% porosities. Finer wires, higher sintering temperature, and longer sintering time will lead to narrower pore-size distributions, more compact porous structures, and stronger compressive yield strength. A random pore model and a twisted wire framework model are put forward to simulate the compressive process. The compressive deformation mechanism is a continuous densification process. The simulated and experimental stress-strain curves all exhibit elastic stage, plastic yield platform stage, and final densification stage.     

椰壳活性炭孔结构对Li-S电池性能的影响

以椰壳为原料,采用化学活化法制备不同比表面积和孔结构的活性炭,通过改变制备工艺参数来调节活性炭的比表面积和孔结构。将活性炭负载60%(质量分数)硫后,作为锂硫电池的正极材料,研究活性炭孔结构对锂硫电池性能的影响。结果表明:随着活性炭比表面积的增加,中孔比例增加,锂硫电池比容量逐步提高。其中,当活化剂与炭化料的质量比为4时,活性炭的比表面积达到2900m2/g,中孔率达到15.36%。在电流密度为200mA/g时,首次放电比容量高达1294.5mAh/g,循环100次后的可逆比容量仍然高达809.3mAh/g。     

介孔材料CO2吸附性能的研究进展

介孔材料以其适中的孔径、大的比表面积、较高的热稳定性和水热稳定性,在吸附、催化、分离等方面有着广阔的应用前景。综述了近年来介孔材料在CO2吸附领域的研究进展,重点介绍了介孔材料及改性介孔材料吸收CO2的方法;并指出以新材料特别是介孔材料为主体进行碳捕集是今后的主要研究方向。     

Fe_3O_4@MgO纳米复合材料的制备及其对Pb~(2+)的吸附性能

采用两步化学沉淀法制备了Fe_3O_4@MgO纳米复合材料,研究了纳米复合材料对Pb~(2+)的吸附性能。结果表明,所制备的复合材料具有较高的顺磁性和稳定性,其饱和磁化强度为58.07 emu/g,初始氧化增重温度为125℃,对Pb~(2+)有较好的吸附能力,在50 min内可以达到吸附平衡,最大吸附量为711.5 mg/g,其吸附过程符合准二级动力学模型和Langmuir等温吸附模型。     

液体苯系物等类油物质吸附材料综述

近年来,苯系物等类油物质泄漏事故频发。由于苯系物多数具有极强的毒性和挥发性,因此苯系物比原油等重油泄漏事故引发的危害更大。考虑到苯系物和油类物质理化性质的相似性,对苯系物泄漏事故的应急处置办法可以参考溢油事故的处置办法。通过对溢油事故中常用的无机类吸附材料、有机高分子吸附材料和天然高分子吸附材料的研究现状和应用前景进行了综述,希望能够为相关科研工作者解决苯系物泄漏的应急处置提供思路,促进该领域的快速发展。     

水分对分子筛结构及吸附性能的影响

分子筛是变压吸附制氧过程中最重要的组分,使用中该组分常出现吸水失效问题,极大地影响了氧产量及浓度.针对此问题,本文以HD-1型和PU-8型分子筛为原料,通过在不同温度(100、200、300、400℃)下活化得到不同含水量的分子筛,并通过对不同材料的结构形貌、热性能及吸附性能的表征分析了水分对分子筛结构及吸附性能的影响.研究结果表明:水分不会破坏分子筛的骨架结构,但会增大晶胞参数,并导致HD-1型分子筛中阳离子迁移;分子筛中的物理吸附水和化学结晶水会影响其吸附性能,其中物理吸附水的影响最大;活化有效提高了分子筛的吸附性能,且温度越高,含水量越少,吸附性能越好;在150~180℃下活化,将物理吸附水脱附后,分子筛的吸附能力可恢复70%,可在此温度下进行吸附器内低温活化;在400℃下活化,脱除化学结晶水,分子筛吸附性能可100%恢复,400℃为两种分子筛的最佳活化温度.     

泡沫钢的制备及压缩吸能特性

为制备高强轻质泡沫钢吸能材料,本文以430L不锈钢粉为原料、CaCl₂为造孔剂,采用粉末冶金烧结-溶解法制备了孔隙率为64%~80%,孔径1~4 mm的泡沫钢.利用SEM和XRD对试样进行微观组织结构分析,并对试样进行轴向准静态压缩测试,分析讨论了孔隙率和孔形对泡沫钢压缩变形行为和吸能特性的影响,以及变形过程中孔结构变形和坍塌机理.研究表明：泡沫钢孔结构呈近球形且分布均匀,孔之间通过孔壁上的微孔形成有效连通.在压缩变形过程中,变形区首先发生在孔形不规则且孔壁较薄处,后诱发周围孔变形并形成多个变形带.泡沫钢试样压缩屈服平台应力随着孔隙率的增加而减小,当孔隙率为64.81%~78.82%时,其对应的屈服平台应力为59.37~17.04 MPa.在孔隙率相同的条件下,孔形为近球形的泡沫试样,其屈服平台应力远高于孔形不规则的试样.当应变量为40%时,孔隙率为64.81%~78.82%的泡沫钢,其单位体积的能量吸收值为23.92~7.32 MJ/m³,约为泡沫铝的5~7倍.4种不同孔隙率泡沫钢样品的理想吸能效率(I)均达0.85以上,表明泡沫钢可以作为一种理想的吸能材料.     

Surface energy-mediated fibronectin adsorption and osteoblast responses on nanostructured diamond

Nanostructured diamond have potential applications in many biomedical related fields and demonstrated extraordinary capacity to influence cellular responses. Studying the surface property of nanodiamond and its influence to protein adsorption and subsequent cellular responses along with the mechanism behind such capacity becomes more important. Here the role of surface energy associated with nanostructured diamond in modulating fibronectin and osteoblast(OB, bone forming cells) responses was investigated. Nanocrystalline diamond(NCD) and submicron crystalline diamond(SMCD) films with controllable surface energy were prepared by microwave-enhanced plasma chemical vapor deposition(MPCVD) techniques. Fibronectin adsorption on the diamond films with varied surface energy values was measured via the enzyme-linked immunosorbent assay(ELISA) and the relationship between the surface energy and fibronectin adsorption was studied. The result indicated that fibronectin adsorption on nanostructured surfaces was closely related to both surface energy and material microstructures. The spreading and migration of OB aggregates(each containing 30–50 cells) on the NCD with varied surface energy values were also studied. The result indicates a correlation between the cell spreading and migration on nanodiamond and the surface energy of nanostructured surface.     

Polymer solutions confined in slit-like pores with attractive walls: An off-lattice Monte Carlo study of static properties and chain dynamics

Summary Using a bead spring model of flexible polymer chains, the density profiles and chain configurational properties of polymer solutions confined between parallel plates were studied. A wide range of density , chain length N, and strength of a short-range attractive wall potential was investigated. Both a temperature T in the good solvent regime (T > , being the Theta temperature where a chain in unconfined bulk three-dimensional solution would behave ideally) and a temperature in the bad solvent regime (T < ) were considered. It is shown that phase separation in a polymer-rich and polymer-poor solution in the slit competes with polymer adsorption at the walls. A qualitative connection to the wetting behavior of semi-infinite polymer solutions is drawn. The acceptance rate for monomer motions was studied for various conditions, and profiles of monomer mobility across the slit were recorded. Also, average chain relaxation times were extracted from the time dependence of mean-square displacements. Although with increasing density the chain radii (at T > ) show a crossover from two-dimensional excluded volume behavior (R_g N² with = 3/4) to ideal random walk behavior ( = 1/2), the relaxation times show effective exponents Z_eff ( N^{Z eff}) that clearly deviate from the Rouse prediction in concentrated confined solutions.