Mn掺杂浓度对Mn-N共掺ZnO电子结构及磁性的影响

采用第一性原理的超软赝势法,分别计算单掺杂Mn、Mn-N按1∶1和2∶1共掺杂ZnO掺杂体系的形成能、能带结构、态密度以及铁磁性。计算结果表明,单掺Mn并不能得到稳定的ZnO,Mn-N共掺会形成p型ZnO。相对Mn-N以1∶1共掺(Mn掺杂浓度6.25%),Mn-N以2∶1共掺(Mn掺杂浓度12.5%)具有更低的形成能,更高的化学稳定性。进一步对ZnO掺杂体系的磁性研究表明,单掺Mn及Mn-N共掺均使ZnO体系呈现铁磁性,其磁性主要来源于Mn3d态电子;在Mn-N以2∶1共掺ZnO体系中,由于Mn掺杂浓度提高,导致总磁矩增加,铁磁性增强明显。     

Zn_(1-x)O_(1-y)Mn_xN_y磁半导体的稳定性,电子结构和半金属性质的第一性原理研究(英文)

利用全势缀加平面波方法计算了Mn和N共掺杂的P型ZnO的8种不同的位置构型.基于总能最低原理我们发现在没有空穴载流子的情况下,第四种构型(N个Mn在同一个层内最近邻位置)是最为稳定的。计算表明,费米面在价带的顶端附近。这个共掺杂体系表现出来的是半金属特性,磁性的起源可以利用BMP理论做出解释。     

基于从头算法的TM金属共掺杂的ZnO基稀磁半导体的磁性研究(英文)

本文采用从头计算的方法研究了基于过渡性金属共掺杂Ⅱ-Ⅵ族稀释半导体的磁性和电子结构.并系统的研究了氧化锌基的稀释半导体铁磁态的稳定性和对其材料设计.在所有的共掺杂体系中,发现(Mn,Co),(Co,Ni)和(Mn,Ni)共掺杂体系是铁磁态的,而(Fe,Ni)共掺杂体系是自旋玻璃态.另一方面,Fe-,Co-和Ni掺杂ZnO基系统的稳态是铁磁态.同时,本文研究了ZnO基稀释半导体的载流子传导铁磁性,计算分析了电子态密度,铁磁态的稳定性.结合双交换和超交换理论解释共掺杂稀释半导体的磁性机理.     

闪锌矿Ga_(1-x)Cr_xN铁磁性的密度泛函理论(英文)

采用基于密度泛函的第一性原理方法计算了闪锌矿GaN掺Cr的电子结构和磁性.考虑不同掺杂浓度和位置,计算结果表明,Ga1-xCrxN呈现铁磁基态,Cr原子间是铁磁性耦合并团簇于N原子,Cr原子与最近邻N原子为反铁磁性耦合.我们采用双交换机制解释了磁性来源和机制.计算结果和最近闪锌矿GaN掺Cr的实验结果吻合.     

ZnO:Mn稀磁薄膜光学性质和铁磁行为分析

采用脉冲激光沉积技术在蓝宝石(α-Al2O3)衬底上制备了不同Mn掺杂浓度的ZnO薄膜.实验结果表明,合适浓度的Mn的掺人,有利于ZnOMn薄膜(002)生长而不形成Mn的氧化物,同时,所有的薄膜均呈现出了室温铁磁特性.随着Mn含量的增加,薄膜光学带隙红移,对应的Mn离子电荷转移跃迁吸收逐渐增强,磁化强度逐渐减小.实验结果支持薄膜的铁磁性起源于替位的Mn离子之间的长程铁磁相互作用,Mn离子增加导致平均磁矩减小,可归因于邻近的Mn离子密度的增加引起的反铁磁作用增强,相对应的sp-d交换作用逐渐增加.     

Fe52T2(T=Cr,Mn,Co,Ni)合金bcc与fcc相结构的第一性原理研究

运用基于密度泛函理论的第一性原理方法研究稀释掺杂的Fe_(52)T_2(T=Cr, Mn, Co, Ni)合金铁磁bcc相和反铁磁fcc相结构的晶格参数、磁性和两相的相对稳定性。结果表明:晶格参数和体模量随掺杂元素d壳层电子个数的变化关系不能用简单的d能带填充图像解释,说明FeT合金中存在较强的磁-结构耦合效应。FeT合金的铁磁bcc相比反铁磁fcc相稳定。反铁磁相呈四方结构,晶格常数c/a比值约为1.07,此相结构可能是一个亚稳态。晶格结构的变化引起电子的重新分布,导致不同磁结构和局域原子磁矩。     

Na,N双受主共掺杂p型ZnO第一原理研究

采用基于密度泛函理论的第一原理平面波超软赝势法,对六方纤锌矿结构ZnO晶体,Na、N分别掺杂ZnO晶体,Na、N共掺杂ZnO晶体的几何结构进行了优化,其中Na、N共掺杂又分为Na、N相连和分开两种情况,以此为基础计算得到了这几种情况下ZnO晶体的能带结构,总态密度和分波态密度。结果表明,Na、N共掺得到的p型ZnO比单掺要好;两种共掺情况中Na、N分开会比Na、N相连p掺杂效果更好。     

N掺杂对Co-ZnO薄膜电学和磁学性能的影响

采用脉冲激光沉积(PLD)法通过电离活化方式在石英和Si(100)衬底上制备了Co-N共掺ZnO薄膜,研究了N掺杂对Co-ZnO薄膜电学和磁学性能的影响.实验观察到700℃、N2O压强为15Pa时生长的Co-N共掺ZnO薄膜显示室温磁滞回线.采用XRD、SEM、XPS、霍尔测试和SQUID等手段对样品进行了测试,结果表明,所得薄膜样品具有高度的c轴择优取向,XRD图谱中并没有发现Co、N的相关分相,Co、N原子分别以替代位形式CoZn、NO存在于薄膜中.霍尔测试和SQUID测试表明,Co-N共掺ZnO薄膜呈p型,具有室温磁滞效应.与Co掺杂ZnO薄膜相比,载流子浓度降低,同时,饱和磁化强度和矫顽力有很大提高,可见,N的掺入改变了Co掺杂ZnO稀磁半导体薄膜的导电类型,并增强了磁性。     

N-X共掺p型ZnO薄膜的研究进展

获得高质量稳定的p型ZnO薄膜是实现ZnO基光电器件化的关键.目前,国际上公认V族元素中的N替代O位(No)是实现p型ZnO较理想的掺杂途径.但p-ZnO:N薄膜的导电性能会随着时间、光照、温度条件发生变化,稳定性不足.大量的理论和实验研究表明N基二元共掺( N-X)可以提高N在ZnO薄膜中的固溶度,浅化N的受主能级,且在很大程度上能够改善p型ZnO的导电性能,有利于获得稳定的p型ZnO薄膜.为此,从N基施主受主共掺、双受主共掺以及其它共掺方面综述了N-X共掺p型ZnO薄膜的研究现状.     

ZnO∶Mn稀磁薄膜光学性质和铁磁行为分析

采用脉冲激光沉积技术在蓝宝石(α-Al2O3)衬底上制备了不同Mn掺杂浓度的ZnO薄膜。实验结果表明,合适浓度的Mn的掺入,有利于ZnO∶Mn薄膜(002)生长而不形成Mn的氧化物,同时,所有的薄膜均呈现出了室温铁磁特性。随着Mn含量的增加,薄膜光学带隙红移,对应的Mn离子电荷转移跃迁吸收逐渐增强,磁化强度逐渐减小。实验结果支持薄膜的铁磁性起源于替位的Mn离子之间的长程铁磁相互作用,Mn离子增加导致平均磁矩减小,可归因于邻近的Mn离子密度的增加引起的反铁磁作用增强,相对应的sp-d交换作用逐渐增加。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.     

新闻(英文)

正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to