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81.
《Surface and interface analysis : SIA》2003,35(6):544-547
We have developed multiple short‐period delta layers as a reference material for SIMS ultra‐shallow depth profiling. Boron nitride delta layers and silicon spacer layers were sputter‐deposited alternately, with a silicon spacer thickness of 1–5 nm. These delta‐doped layers were used to measure the sputtering rate change in the initial stage of oxygen ion bombardment. A significant variation of sputtering rate was observed in the initial 3 nm or less. The sputtering rate in the initial 3 nm was estimated to be about four times larger than the steady‐state value for 1000 eV oxygen ions. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
82.
γ-射线辐照对尼龙6纤维结构的影响 总被引:1,自引:0,他引:1
<正> 过去的大多数研究表明,高能射线辐照会引起聚乙烯及聚丙烯等稀烃类聚合物分子链交联及降解,而且会导致结晶度下降。张利华等人最近的研究表明,对于尼龙1010塑料,仅当辐照剂量高到一定程度后,辐照才会破坏结晶。此外,Stowe等人曾经研究过近紫外线对尼龙66纤维结构的影响,结果表明,在空气气氛中的近紫外辐照主要导致尼龙66纤维降解,并使纤维结晶度提高。有关高能射线辐照对高度取向的合成纤维结构及性能的影响的研究尚不多见。本工作将讨论γ-射线对于尼龙6纤维结构的影响。 相似文献
83.
84.
采用溶胶-凝胶法合成了一种V2O5/C复合材料.扫描电镜(SEM)和红外光谱(FTIR)分析表明,这是一种外层V2O5胶体包覆内层乙炔分子的多孔复合材料.以V2O5/C作正极,锌片为负极,Zn(ClO4)2溶液为电解质组成水相锌二次电池,采用循环伏安(CV)和电化学阻抗谱(EIS)等方法研究发现:V2O5:C质量比为1:1时电极具有最好的电化学性能,电池开路电压达1.64 V; Zn2+能分别在1.01 V和1.26 V处分步嵌入V2O5/C结构中A、B两种位置,其嵌入电流密度峰值最高可达70 mA•g-1,并且具有较好的循环充放电性能;在一定放电深度下,V2O5/C电极反应速率受Zn2+的扩散过程控制. 相似文献
85.
锂离子电池正极材料LiMn2O4的合成与晶体结构(英) 总被引:2,自引:0,他引:2
Spinel LiMn2O4 powders were prepared using two-step synthesis method consisting of solid-state reaction method and citrate modified sol-gel method. The effects of the calcination temperature and the Li/Mn ratio of raw materials were studied on the physicochemical and electrochemical properties of the spinel LiMn2O4 powders, such as crystallinity, lattice constant and density. The title compound was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Polycrystalline LiMn2O4 powers calcined at 750 ℃ were found to be composed of very uniformly-sized microcrystal with an average particle size of 300 nm. The improvement in electrochemical properties was mainly attributed to the process of re-grinding by absolute alcohol. 相似文献
86.
Polyethylene based composites are attractive materials for advanced circuit board applications because of their unique combination of properties: low dielectric constant and loss factor, light weight, high flexural modulus and low thermal expansion coefficient controlled in all spatial directions. This investigation describes a process to consolidate chopped fibers of ultra‐high molecular weight polyethylene concurrently with its bonding to a copper foil. Bonding is affected by a thin sheet of low‐density polyethylene, incorporating a crosslinking agent with a concentration gradient across the sheets thickness. In this single step process, the composite material is formed and bonded to the metal foil, achieving good adhesion without the use of extraneous glue. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
87.
88.
Various diblocks, triblocks and a graft copolymer of butadiene with 4-vinylpyridine short blocks have been prepared. They were complexed with ZnCl2 to give ionomer-like materials. For all copolymers, the Tg of the elastomeric block (?84°C to ?91°C) was unchanged by complexation. For all diblocks and triblocks with short blocks (DP n ~ 3) the storage modulus was only slightly increased by comparison with uncomplexed materials. For the graft copolymer even with short blocks the material is less sensitive to temperature after complexation. For triblocks, when the DP n of the vinylpyridine blocks was high enough (15 units), complexes were associated in multiplets of large size and the elastomeric properties were retained up to 200°C. 相似文献
89.
固相氯化法合成氯化聚乙烯的红外光谱研究 总被引:2,自引:0,他引:2
本文研究在不同条件固相氯化聚乙烯(CPE)的红外光谱,探讨了一步和两步氯化合成的CPE的结构差别,着重讨论了两步氯化的CPE结构特点。从观察表征结晶结构和—(CH_2)_n—链段氯分布的特征频率变化表明,低温固相氯化主要发生在无定形区,并且在CPE中形成高氯化和低氯化链段(或未氯化)的嵌段结构。在两步固相氯化时,晶区受到较大程度的破坏,氯化作用已不局限在无定形区,其结晶结构的破坏主要同第二步氯化程度有关,即使CPE氯含量相同,若前后两步氯化程度不同,结构有很大差异。 相似文献
90.
SYNTHESIS OF MESOPOROUS POLY(STYRENE-co-MALEIC ANHYDRIDE)/SILICA HYBRID MATERIALS VIA A NONSURFACTANT-TEMPLATED SOL-GEL PROCESS* 总被引:1,自引:0,他引:1
Jie-bin Pang Kun-yuan Qiu Yen Wei Department of Polymer Science Engineering College of Chemistry Molecular Engineering Peking University Beijing China. Department of Chemistry Drexel University Philadelphia Pennsylvania USA. 《高分子科学》2000,(5):469-472
Mesoporous poly (styrene-co-maleic anhydride)/silica hybrid materials have been prepared. The synthesis wasachieved by the HCl-catalyzed sol-gel reactions of tetraethyl orthosilicate (TEOS) and styrene-maleic anhydride copolymerin the presence of 3-aminopropyl triethoxysilane (APTES) as a coupling agent and citric acid as a nonsurfactant template orpore-forming agent, followed by ethanol extraction. Characterization results from nitrogen sorption isotherms and powder X-ray diffraction indicate that polymer-modified mesoporous materials with large specific surface areas (e.g. 900 m~2/g) andpore volumes (e.g. 0.6 cm~3/g) could be prepared. As the citric acid concentration is increased, the specific surface areas, porevolumes and pore diameters of the hybrid materials increase. 相似文献