首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5篇
  免费   2篇
  国内免费   3篇
化学   5篇
物理学   5篇
  2022年   1篇
  2020年   1篇
  2019年   1篇
  2013年   1篇
  2011年   3篇
  1996年   1篇
  1994年   1篇
  1985年   1篇
排序方式: 共有10条查询结果,搜索用时 15 毫秒
1
1.
许洪光  吴苗苗  张增光  孙强  郑卫军 《中国物理 B》2011,20(4):43102-043102
Anion ion photoelectron spectroscopy and density functional theory (DFT) are used to investigate the electronic and structural properties of ScSin- (n=2sim6) clusters and their neutrals. We find that the structures of ScSin- are similar to those of Sin+1-. The most stable isomers of ScSin- cluster anions and their neutrals are similar for n=2, 3 and 5 but different for n=4 and 6, indicating that the charge effect on geometry is size dependent for small scandium-silicon clusters. The low electron binding energy (EBE) tails observed in the spectra of ScSi4,6- can be explained by the existence of less stable isomers. A comparison between ScSin- and VSin- clusters shows the effects of metal size and electron configuration on cluster geometries.  相似文献   
2.
利用密度泛函理论(DFT)研究3d过渡金属掺杂硅团簇的几何结构和稳定性,计算了绝热电子亲和能和垂直电离能,内嵌双金属间距,自旋磁矩等.结果表明内嵌的Sc、Ti、V、Mn金属二聚体和十二面体硅笼构成了稳定的富勒烯结构,随着d电子数目的增加其内嵌的富勒烯构型有部分畸变,总体而言Si_(20)团簇掺杂双金属后稳定性得到了提高.  相似文献   
3.
在相同的反应条件下,基于配体(Hpypymba=4-((3-(吡嗪-2-基)-1H-吡唑-1-基)甲基)苯甲酸)和过渡金属离子(Co(Ⅱ)、Cd(Ⅱ))合成同构金属掺杂材料[CoxCd1-x(pypymba)2]n(0 ≤ x ≤ 1)(配合物1~5),运用粉末X射线衍射(PXRD)、紫外等分析手段对其结构与形貌进行表征。将得到的MOFs作为催化剂载体负载Ag离子进行4-硝基苯酚的还原反应。研究表明含Co2+的化合物1是良好的催化剂载体,随着配合物中Cd2+比例的增加,反应速率下降,甚至对反应有一定的抑制效果。该MOFs对于Ag的最大负载量为47%(w/w),Ag@compound 1经4次循环后依然有96%的催化效率。  相似文献   
4.
The effects of different concentrations of metals (Ni, Cu, Cd, Zn) on the reactivity of carbon towards air were studied by means of TG and DTA. It was observed that these metals are capable of decreasing the ignition temperature and increasing the mass loss. Activation energies calculated by Horowitz's method revealed that these metals promote the combustion of active carbon.  相似文献   
5.
纳米多孔碳气凝胶的储氢性能   总被引:1,自引:0,他引:1       下载免费PDF全文
 以间苯二酚和甲醛为原料,采用溶胶-凝胶工艺,结合高温碳化和溶剂替换常压干燥技术,制备了碳气凝胶。通过改变间苯二酚与碳酸钠的物质的量比和反应物间苯二酚与甲醛的质量分数,实现对碳气凝胶孔洞结构的控制。制备了钯掺杂碳气凝胶。以透射电镜、X射线衍射谱证实了钯元素以纳米单质颗粒形式存在于碳气凝胶的骨架结构中。对掺杂碳气凝胶进行了活化工艺的后处理,成功提高了比表面积有2倍之多,获得了比表面积为1 273 m2/g的钯掺杂碳气凝胶。氢吸附性能研究结果表明:最优活化工艺所得的碳气凝胶样品(3 212 m2/g)在92 K,3.5 MPa条件下的饱和储氢质量分数为3%,此样品在303 K,3.2 MPa时的储氢质量分数为0.84%。对钯掺杂碳气凝胶的常温(303 K)氢吸附测试表明,掺杂后碳气凝胶的总储氢质量分数下降了,但单位比表面积的储氢质量分数提高了。  相似文献   
6.
以间苯二酚和甲醛为原料,采用溶胶-凝胶工艺,结合高温碳化和溶剂替换常压干燥技术,制备了碳气凝胶。通过改变间苯二酚与碳酸钠的物质的量比和反应物间苯二酚与甲醛的质量分数,实现对碳气凝胶孔洞结构的控制。制备了钯掺杂碳气凝胶。以透射电镜、X射线衍射谱证实了钯元素以纳米单质颗粒形式存在于碳气凝胶的骨架结构中。对掺杂碳气凝胶进行了活化工艺的后处理,成功提高了比表面积有2倍之多,获得了比表面积为1 273 m2/g的钯掺杂碳气凝胶。氢吸附性能研究结果表明:最优活化工艺所得的碳气凝胶样品(3 212 m2/g)在92 K,3.5 MPa条件下的饱和储氢质量分数为3%,此样品在303 K,3.2 MPa时的储氢质量分数为0.84%。对钯掺杂碳气凝胶的常温(303 K)氢吸附测试表明,掺杂后碳气凝胶的总储氢质量分数下降了,但单位比表面积的储氢质量分数提高了。  相似文献   
7.
Simultaneous plasma polymerization of halocarbons (CF4 and C2F3Cl) and sputtering of metals (Au and Al) or cosputtering [Au + polytetrafluoroethylene (PTFE, Teflon)] have been performed by means of an RF (20 MHz) glow discharge excited by a planar magnetron. The optical emission spectroscopy (OES) has been used for monitoring the deposition process of metal-doped polymer films. The light emission intensity ratios of the relevant species in the plasma volume are given in connection with the characteristics of the films prepared.  相似文献   
8.
A new parameter, ( v)–1 is proposed for evaluating the surface basicity of alkali metal-doped MgO from a positive correlation with acetone/propene ratio in the decomposition of 2-propanol.  相似文献   
9.
制备了Ni(Ⅱ)掺杂的分级多孔金属有机骨架材料(HP-Ni-Cu-BTC,H3BTC=均苯三甲酸),并将其作为吸附剂去除四环素(TC)。研究表明,Ni(Ⅱ)的掺杂和分级多孔结构显著提高了TC的吸附容量,是微孔Cu-BTC的3.28倍。吸附动力学和吸附等温线结果证明,化学吸附在吸附反应中占主导地位,TC在HP-Ni-Cu-BTC上的吸附是通过在非均质吸附剂表面的多层吸附进行的。此外,在循环实验中,重复使用4次后,HP-Ni-Cu-BTC仍然还有71.45% 的吸附效率,说明其有良好的可重复使用性。  相似文献   
10.
The electronic origin of the influence of the anomeric effect (negative hyperconjugative interaction, NHI) on the Fermi contact (FC) term of 1 J(C, H) couplings has been studied from a theoretical point of view at the DFT-B3LYP level. The HN=CH2, molecule was chosen as the primary model compound, in which both FC 1 J(C, H) couplings were decomposed into bond contributions with the natural J coupling dissection approach (NJC). Differences between the 1 J (C, H)FC couplings for C——H bonds in synperiplanar and antiperiplanar orientations with respect to the nitrogen non-bonding electron pair closely follow the experimental trend. They are made up chiefly of three NJC contributions: ‘bond’, ‘direct lone pair’ and the ‘carbon-core orbitals’. The NHI influence on these terms was studied by applying the natural bond orbital (NBO) deletion procedure to the charge transfer interaction into the antiperiplanar (C——H) antibond (n(N)→(C——H)?) prior to the NJC dissection calculation. The dielectric solvation effect on both the total FC terms and the respective NJC contributions was estimated by carrying out the calculations using the polarization continuum model. Inhibition of the anomeric effect is evident when the solvent polarity is increased. NHI saturates rapidly with increasing solvent dielectric. Specific solute-solvent interaction effects on 1 J(C, H) couplings were estimated by evaluating molecular complex models of the form CH2=HN…S (S = H2O and DMSO).  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号