Montasser DEWIDAR
,
H.Fouad MOHAMED
材料科学技术（英）
Titanium and its alloys are currently considered as one of the most important metallic materials used in the biomedical applications, due to their excellent mechanical properties and superior biocompatibility. In the present study, a new effective method for fabricating high porosity titanium alloy scaffolds was developed. Porous Ti-6Al-4V scaffolds are successfully fabricated with porosities ranging from 30% to 70% using space-holder and powder sintering technique. Based on its acceptable properties, spherical carbamide particles with different diameters (0.56, 0.8, and 1 mm) were used as the space-holder material in the present investigation. The Ti-6Al-4V scaffolds porosity is characterized by using scanning electron microscopy. The results show that the scaffolds spherical-shaped pores are depending on the shape, size and distribution of the space-holder particles. This investigation shows that the present new manufacturing technique is promising to fabricate a controlled high porosity and high purity Ti-6Al-4V scaffolds for hard tissue replacement.
关键词:
Ti-6Al-4V
,
null
,
null
,
null
Wei XIA
,
Puqing CHEN
,
Zhaoyao ZHOU
,
Weibin ZHAO
,
Yuanyuan LI
材料科学技术（英）
This paper establishes a mechanical model for sintered powder metal material and simulates the material behavior. Powder metal specimens were compacted, sintered and upset. Relative density and contour of the specimen were measured. The force displacement relationship during upsetting was recorded. The same upsetting process was simulated with 3-dimensional finite element method. In simulation, the cubic specimen was treated as a piece of metal embedded with pores. Its overall relative density was controlled via adjusting the concentration of the pores. In the virtual upsetting process, when the pores are compressed, material around the pores will be in touch with each other. This kind of self-contact effect was dealt with direct contact detecting method. Classical V.Mises principle and isotropic hardening rule were applied on the material. Simulation results agree with experimental.
关键词:
Metal powder
,
null
,
null
刘昌俊
,
李敏悦
,
王嘉琪
,
周昕瞳
,
郭秋婷
,
严金茂
,
李英芝
催化学报
doi:10.1016/S1872-2067(15)61020-8
催化在现代化工生产中正发挥非常重要的作用.在未来催化甚至会扮演更重要的角色.然而,现有的催化剂制备方法会对空气、水和土地造成污染.这些污染主要来源于催化剂制备过程中会用到的各种有害化学品.而且,现有催化剂制备过程耗时长、耗能高、用水量大.这些都不符合绿色化学原则.因此,开展催化剂绿色制备研究十分必要.这一研究的长远目标是避免或者消除催化剂制备过程每一环节产生的污染,降低每一环节的能耗和物耗,缩短制备时间,减少劳动强度.显然,这并不是一个容易达成的目标.因此,朝着上述长远目标的任何进展,无论是小进展还是大进展,都将有助于最终实现催化剂的绿色制备.我们总结了气体放电冷等离子体在催化剂绿色制备方面的最新进展,特别强调了非氢冷等离子体在催化剂制备中的应用.冷等离子体是一种能在室温附近操作的非平衡等离子体,是对气体施加一定电压(数百至上万伏特;具体电压值取决于气体压力)形成的.冷等离子体制备方法可以在少用或者不用有害化学品的基础上,有效减小催化剂粒径、增加催化剂分散度、提高催化剂和载体的相互作用等.这些改进同时能进一步提高催化剂的活性和稳定性.相对于常规热化学制备催化剂,冷等离子体制备的显著区别在于:冷等离子体在室温或者略高于室温条件下操作,可以有效避免热化学方法存在的缺点.冷等离子体方法利用其富含的高能物质(如电子)快速促进催化剂前驱体分解,从而实现催化剂快速成核.由于低温操作,其晶体生长速度受到限制,催化剂分散性得以提高.研究表明,以非氢等离子体作为电子源的室温电子还原能够有效还原贵金属离子.这个过程中既不需要有害化学还原剂也不需要氢还原.这为以热敏材料和化学不稳定物质作为基底的负载型催化剂制备创造了条件.这些热敏材料包括金属有机骨架材料(MOF)、共价有机骨架材料(COF)、高比表面积的碳、多肽、DNA和蛋白质等等.这个室温电子还原还被用于制备能在水面或其它溶液表面上漂浮的催化剂,对发展新型催化剂有很大帮助.此外,使用冷等离子体还可以进行低温模板脱除,以避免高温分解可能出现的烧结问题,在保证催化剂高比表面积的同时获得只有在高温分解才能得到的结构特征.研究表明,可以使用冷等离子体诱发微燃烧以除去炭模板,可以有效减少炭模板法制备氧化物结构材料所需要的化学品.冷等离子体方法在催化剂制备中的应用刚刚开始,尚有大量研究还有待于开展(如多金属氧化物制备等),存在大量研发机会.可以预期,冷等离子体在催化剂绿色制备与应用中将发挥更重要的作用.
关键词:
催化剂制备
,
等离子体
,
绿色化学
,
多孔材料
范登森
,
王立
,
俞豪杰
,
霍甲
材料科学与工程学报
多孔材料已经被广泛地应用于储氢研究。本文研究了Pd负载的高度交联聚苯乙烯（Pd—HCLPS）储氢材料的制备及储氢性能。在超声的辅助下，通过简便的置换反应成功制备了Pd—HCLPS。Pd颗粒以纳米尺度均匀分散在聚合物中。通过调节超声时间，制备了一系列不同Pd含量的Pd—HCLPS样品。发现Pd含量是影响氢溢流的一个重要因素。相比于HCLPS，Pd的负载使Pd—HCLPS样品的储氢量增强了1．1～1．7倍。在173K，3．1MPa下，最大储氢量为1．46wt9／6。
关键词:
储氢
,
Pd负载
,
多孔材料
