Cr原子链的几何结构与电子性质研究

基于第一性原理方法研究Cr原子链可能形成的几何结构与电子性质.计算表明:Cr原子链可形成线性型、二聚化型、平面之字型和梯型等一维原子链.梯型结构的原子链结合能最大,稳定性最好,二聚化型结构次之,然后是大角度的之字型结构、小角度的之字型结构,线性结构的结合能最小.其中二聚化结构原子链的能带表现出间接带隙的特征,大角度之字型结构原子链为半金属性,小角度之字型结构原子链的能带则表现为较强的金属性.同时还讨论了这些结构的相对稳定性以及各链式结构的电子能带、电荷密度等性质.

基于Cr原子光刻技术的nm光栅间距比对测量定值方法研究

建立了一种基于Cr原子光刻技术的nm光栅间距比对测量定值方法。以国家自溯源光栅标准物质来建立标准样板校准溯源体系的可行性为基础,保障测量仪器更高精度、可溯源性;设计并制备了节距长度有序递增的多周期电子束直写光栅样板,满足可适配于不同分辨率的nm测量仪器的需求,名义节距值分别为200、400、600、800、1 000 nm。经国家自溯源光栅标准物质比对后的AFM完成对nm栅格标准样板的测量与表征,实验表明:电子束直写制备的光栅标准样板均匀性水平1 nm,相对不确定度低于2%,光栅均具有良好的均匀性、准确性以及稳定性,验证了研制的光栅标准样板能作为一种理想的实物标准运用于nm几何量量值溯源体系。

直流电弧中若干缓冲剂对Cu及Cr原子(离子)停留时间的影响

光谱缓冲剂对激发过程的影响是多方面的,诸如,温度、电弧中的化学反应、试样蒸发速度,倍背比的影响等等,而它对原子（离子）在直流电弧中停留时间的影响是其主要影响因素之一。这一课题的研究对全面了解光谱缓冲剂的作用是有意义的。本文通过实验得到了一些初步的结论,合理的解释了某些第一电离电势较低的缓冲剂出现反常现象。 关于金属原子在直流电弧中停留时间的测定已有一些报导[1]。本实验测定了Cu、Cr氧化物在KCI、CuF2、Li2CO3、Sr（NO3）2、BaCO3,、PbCl2等缓冲剂中的停留时间。

椭圆型激光驻波场作用下Cr原子的汇聚特性研究

利用近共振激光驻波场操纵中性原子实现纳米级条纹沉积技术是一种新型的研制纳米结构长度标准传递的方法.分析了Cr原子在椭圆型激光驻波场作用下的沉积特性,分别对不同椭圆激光驻波场功率下Cr原子的沉积条纹及不同y平面上沉积条纹特性进行了模拟和分析.同时针对椭圆激光驻波场作用下Cr原子发散角对沉积条纹特性的影响进行了模拟计算,比较了不同发散角条件下沉积条纹的对比度和半高宽.

Cr、Mn原子在Fe(100)表面的反常偏聚行为研究

采用第一性原理计算研究了合金原子Cr、Mn在Fe(100)表面的反常偏聚现象。将偏聚能分解为力学能、化学能和主格原子移除能3个部分。结果表明:力学能对偏聚的贡献较小,偏聚能的反常趋势是化学能与主格原子移除能竞争的结果。

Microscopic phase-field simulation of Cr atom substitution character during formation of L1_2 and DO_22 phases in Ni-Cr-Al alloy

The simulations of Cr atom substitution character during the formation of L12 and DO22 phases in Ni-Cr-Al alloy were performed at 873 K based on microscopic phase-field model. It is found that the substitution of Cr is affected by Cr and Al contents and limits of occupation probabilities of Cr atom in L12 phase are present. The precipitate is single L12 phase when the component is less than the limit, Cr atoms substitute the Al sublattices in Ll2 phase, and both of atoms Al and Cr occupy the β-sites and complex phases Ni3（Al1-xCrx） are formed; Cr atoms enter Ni sites when Al and Cr contents exceed the limit, and substitute β-sites or both of α- and β-sites. The DO22 phase is formed at the boundary of Ll2 phase.

Influences of Organic Acids and Heavy Metals on Cr（VI） Photoreduction Catalyzed by TiO2 Suspension

Photocatalytic reduction of Cr（VI） by TiO2 suspension has been studied with the purpose of removing the toxic and carcinogenic Cr（VI） ions from water. The photocatalytic reduction was carried out in batch reactor, in which the influences of the presence ofmalonic and oxalic acids as well as of iron and lead ions on the degree of the reduction have been systematically evaluated. The results of the research indicated that the presence of malonic and oxalic acids with increasing concentration can improve the photoreduction. The increase in the Cr（V1） photoreduction is due to OH radical capturing by the organic acids so that it prevents the recombination of the OH radical and the free electron, and therefore can provide enough electron supply for Cr（VI） photoreduction. The effectiveness of Cr（VI） photoreduction is also enhanced by the addition of increasing concentration of both Fe（Ⅲ） and Pb（Ⅱ） ions through synergic effect. It is also found that the degree of the photopreduction is strongly influenced by solution acidity and the most effective Cr（VI） photoreduction is obtained at lower pH than 5, either in the absence or presence of the organic acids and the heavy metal ions.

First-principles study on electronic structure, magnetic and dielectric properties of Cr-doped Fe_3C

The first-principles calculations were performed to investigate the electronic structure, magnetic and dielectric properties of Cr-doped Fe_3C, in comparison to those of pure Fe_3C and Cr_3C. The obtained results show that the thermodynamic stability of Crdoped Fe_3C becomes weaker in terms of the larger formation enthalpy, on the contrary, the metallicity and covalency are found to strengthen to some extent. The magnetic moments of Fe_3C, Fe_(11)CrC_4(g), and Fe_(11)CrC_4(s) are respectively 21.36 μB/cell, 16.92 μB/cell, and 17.62 μB/cell, and in Fe_(11)CrC4(g) and Fe_(11)CrC_4(s), the Fe of Wyckoff positions of 8d and 4c is substituted by Cr. The local magnetic moment of Cr at 8d site is larger than that at 4c site in the doped structure, which is opposite to that of Fe. In low frequency band, the permittivity follows the ranking of Fe_(11)Cr C_4(s)>Cr_3C>Fe_(11)Cr C_4(g)>Fe_3C. Once exceeding a certain frequency, the sequence will be broken. Besides the electron transition, the polarization of atoms also makes a contribution to the dielectric properties.

Adsorption of Chromium （Ⅵ） from Aqueous Solution Using Zeolite/Chitosan Hybrid Composite

This study investigated the adsorption ability of ZCHC （zeolite/chitosan hybrid composite） as adsorbent for chromium （Cr（Ⅵ））, ZCHC was prepared with sol-gel method by mixing zeolite and chitosan. Adsorption experiment from aqueous solutions containing known amount of Cr（Ⅵ） using zeolite, chitosan and ZCHC was explored to evaluate the efficiency of ZCHC as adsorbent for Cr in a batch system. The amount of Cr（Ⅵ） adsorbed at different pH values, initial concentrations, adsorbent dosages, and contact times were determined by ICP-AES （inductively coupled plasma-atomic emission spectrometry） in order to determine the optimum conditions for Cr（Ⅵ） adsorption. Furthermore, the adsorption mechanism of Cr（Ⅵ） by zeolite, chitosan and ZCHC was investigated by applying Langmuir and Freundlich isotherm equations to the data obtained. In addition, the rates of adsorption were found to conform to pseudo-second order kinetics.

电弧离子镀CrTiN涂层的结构及耐腐蚀性能

采用电弧离子镀技术在模具钢H13表面沉积Cr_(x)Ti_(1-x)N涂层,系统研究了不同Cr/Ti原子比对CrTiN合金化涂层结构、力学性能以及耐腐蚀性能的影响。结果表明:通过改变分离靶弧流实现CrTiN涂层中Cr/Ti原子比的有效调控,所制备的CrTiN涂层主要由面心立方结构(Cr,Ti)N和CrN组成,随着Cr/Ti原子比从1.1增加至1.8,涂层相结构由随机取向向(111)晶面优先生长转变。CrTiN合金化涂层显微硬度较CrN涂层得到明显提升,并随着固溶引起的晶格畸变程度变化而具有一个极大值。通过电化学阻抗谱和动电位极化曲线分析,当Cr/Ti原子比为1.4时,致密的Cr_(0.59)Ti_(0.41)N涂层具有最佳的耐腐蚀性能。