densityfunctionaltheorystudyofcocatalyticoxidationonpt111andpt3ni111surfaces

CO and O adsorption and co-adsorption and CO oxidation oil Pt(111) and Pt3Ni(111) surfaces were studied systematically by density functional theory calculations. Compared with CO and O adsorption oil the Pt(111) surface, adsorption on the Pt3Ni(111) surface is slightly destabilized for CO but stabilized significantly for O. Both surfaces have similar reactivity for CO oxidation. The presence of surface Ni atoms stabilizes oxygen not only at the initial state but also at the transition state on the Pt3Ni(111) surface

2000—2006年中国天山山区积雪时空分布特征研究

以中国境内天山山区为研究区,基于2000—2006年的遥感积雪产品积雪分布时间序列趋势和空间分布特征,对积雪分布的年际变化趋势、积雪分布随海拔的变化趋势、积雪频率以及积雪雪线高度的年变化进行了分析.结果表明:1)积雪经历从秋季开始累积到春季开始消融的过程,1—2月积雪面积达到最大,7—8月面积最小.冬季积雪所占比例最大,超过50%;2)2000—2006年积雪面积年际变化略呈上升趋势,冬季上升趋势较明显,春、秋和夏季变化趋势不明显.冬季积雪面积在海拔<4000m呈上升趋势,≥4000m呈下降趋势.在海拔2000m积雪的上升趋势达到最高点;3)从积雪频率来看,存在5个高值区,覆盖频率高达70%左右.从空间分布来看,天山中段积雪最多,东段次之,西段最少.在海拔3000m以下积雪次数较少,海拔3000m以上积雪次数显著增加.月积雪次数随海拔的变化表现为:海拔4000m以上各月的积雪次数都很多,12月至翌年2月在各高程带的积雪次数都较大;10—11月和3—4月积雪以海拔2500m为界,之下次数较少,以上次数增加显著;5—9月的积雪次数在海拔3000m以下非常少,在海拔3000m以上次数逐渐增加;4)以覆盖率≥40%相对应的海拔作为各个月份的雪线高度,天山山区平均雪线海拔在2875m.夏季雪线海拔在4000m以上;冬季雪线海拔在1500m

densityfunctionaltheorystudyofcocatalyticoxidationonpt111andpt3ni111surfaces

CO and O adsorption and co-adsorption and CO oxidation oil Pt(111) and Pt3Ni(111) surfaces were studied systematically by density functional theory calculations. Compared with CO and O adsorption oil the Pt(111) surface, adsorption on the Pt3Ni(111) surface is slightly destabilized for CO but stabilized significantly for O. Both surfaces have similar reactivity for CO oxidation. The presence of surface Ni atoms stabilizes oxygen not only at the initial state but also at the transition state on the Pt3Ni(111) surface

Preparation of Silver Coated Magnetic Polymethylmethacrylate Micro Beads

采用化学镀法制得了表面包覆银层的导电磁性聚甲基丙烯酸甲酯(PMMA)微球。对粗糙度不同的微球进行镀银,研究了银在微球上的沉积机理。表面改性使磁性PMMA微球功能化,具有和银强烈结合的能力,从而得到包覆均匀的导电磁性微球。研究了硝酸银和磁性微球的含量对包覆效果及导电性能的影响,并通过SEM和EdS对镀银磁性微球的表面形貌及组成进行了分析。Silver coated magnetic polymethylmethacrylate(PMMA) micro beads were prepared by chemical reduction.The mechanism of the deposition of silver particles was investigated.The experiment shows that surface roughness of the micro core bead can enhance the deposition or coating coverage and treatment of surface of the micro core bead can enhance interaction between the the micro core bead and silver atoms,leading to an uniform deposition or coating.The effects of the introduced weights of AgNO3 and the core beads in the reaction solution on the deposition or coating effectiveness or the conductivity of the silver coated beads were also studied.The surface morphology and composition of the coated beads were examined by SEM and EDS respectively.福建省科技项目重大专项(2005HZ1019);厦门市科技计划重点项目(3502Z20055010);国家重点基础研究发展计划(973)项目(2007CB936603);国家科技计划国际科技合作与交流专项(2008DFA51230);国家自然科学基金资助项目(60776007