Journal of Materials Science
Mn(3+x) Ga(1-x) N compounds with x = 0.0 and 0.1 were prepared by re-sintering Mn(2)N(0.86), Ga bulk and Mn powders. These compounds are deduced to be the N-deficiency ones. In Mn(3)GaN, a step-like magnetic transition, from frustrated antiferromagnetism to paramagnetism with increasing temperature, occurs at 370 K, while the same magnetic transition of Mn(3.1)Ga(0.9)N is far above 380 K. The enhanced magnetization of Mn(3)GaN at low temperatures is ascribed to the fast lowering of antiferromagnetism. The electrical resistivity of Mn(3)GaN exhibits a typically metallic conducting behavior with a positive magnetoresistance of 4-7%.
关键词:
perovskites;heat;manganese;mn3znn;phase
Journal of Physical Chemistry C
The highly unusual structural and electronic properties of the alpha-phase of (Si(1-x)C(x))(3)N(4) are determined by density functional theory (DFT) calculations using the Generalized Gradient Approximation (GGA). The electronic properties of alpha-(Si(1-x)C(x))(3)N(4) are found to be very close to those of alpha-C(3)N(4). The bandgap of alpha-(Si(1-x)C(x))(3)N(4) significantly decreases as C atoms are substituted by Si atoms (in 2 most cases, smaller than that of either alpha-Si(3)N(4) or alpha-C(3)N(4)) and attains a minimum when the ratio of C to Si is close to 2. On the other hand, the bulk modulus of alpha-(Si(1-x)C(x))(3)N(4) is found to be closer to that of alpha-Si(3)N(4) than of alpha-C(3)N(4). Plasma-assisted synthesis experiments of CN(x) and SiCN films are performed to verify the accuracy of the DFT calculations. TEM measurements confirm the calculated lattice constants, and FT-IR/XPS analysis confirms the formation and lengths of C-N and Si-N bonds. The results of DFT calculations are also in a remarkable agreement with the experiments of other authors.
关键词:
chemical-vapor-deposition;silicon-carbon nitride;thin-films;optical-properties;room-temperature;alpha-phase;growth;hard;photoluminescence;microstructure
Materials and Corrosion-Werkstoffe Und Korrosion
A CrN/Cr(1-x)Al(x)N coating comprised of an inner layer of CrN and an outer layer of Cr1(1-x)Al(x)N with a gradient distribution of Al was deposited on two different alloys by a reactive sputtering method. Oxidation and hot-corrosion tests of the gradient CrN/Cr1(1-x)Al(x)N coating were performed at different temperatures. The phase compositions and morphologies of the as-deposited coating and the corrosion products were investigated by using XRD and SEM/EDS. The results showed that the gradient CrN/Cr1(1-x)Al(x)N coating exhibited good oxidation resistance at temperatures above 1000 degrees C owing to the formation of an alpha-Al(2)O(3)-rich oxide scale. The coating possessed good hot-corrosion resistance in molten sulfate because the inner CrN layer could supply enough Cr to form a relatively protective Cr(2)O(3) after the Al(2)O(3)-enriched scale failed due to its dissolution in the molten sulfate.
关键词:
high-temperature oxidation;aluminide coatings;overlay coatings;nitride coatings;behavior;alloy;superalloy;k38g;cr
季振国
,
娄垚
,
毛启楠
无机材料学报
doi:10.3724/SP.J.1077.2010.00386
沉积参数对MOCVD法生长的Al_xGa_(1-x)N薄膜性能有很大的影响.利用高分辨XRD,紫外-可见透射光谱,原子力显微镜,扫描电子显微镜和荧光光谱研究了沉积温度对低压MOCVD沉积的高Al含量的Al_xGa_(1-x)N外延膜缺陷密度以及发光性能的影响.结果发现,随着沉积温度的升高,Al_xGa_(1-x)N薄膜中的螺型位错密度减少,但是刃型位错密度增加,因此简单地改变沉积温度并不能降低总的位错密度以及提高薄膜的发光性能.进一步地分析测试结果表明,随着沉积温度的升高,Al_xGa_(1-x)N薄膜内的Al含量增加,导致禁带宽度增大和发光波长的蓝移,因此适当提高沉积温度(1000～1050℃)是获得高Al含量Al_xGa_(1-x)N薄膜的一种有效手段,但是过高的沉积温度(>1100℃)不利于提高薄膜的发光强度.
关键词:
AlGaN
,
高铝含量
,
MOCVD
,
外延
,
沉积温度
Philosophical Magazine
The microstructure of ferroelectric [PbZr(x)Ti(1-x)O(3)/PbZr(y)Ti(1-y)O(3)](n) epitaxial multilayers (x/y 0.2/0.4, 0.4/0.6) deposited on SrRuO(3)-coated SrTiO(3) substrates by pulsed-laser deposition with different layer periodicity and layer thickness was characterized by means of transmission electron microscopy. Electron diffraction and contrast analysis revealed a very clear and well-separated layer sequence. The microstructures of PbZr(0.2)Ti(0.8)O(3)/PbZr(0.4)Ti(0.6)O(3) and PbZr(0.4)Ti(0.6)O(3)/PbZr(0.6)Ti(0.4)O(3) multilayers show a similar tendency in the dependence on the individual layer thickness. Whereas with thick individual layers, tetragonal a-domains are confined to specific layers of the two types of multilayers, below a certain critical thickness of the individual layers, a-domains extend over the whole film. This indicates a transition into a uniform tetragonal lattice and strain state of the whole multilayer. Increasing the layer periodicity further, the interfaces in PbZr(0.4)Ti(0.6)O(3)/PbZr(0.6)Ti(0.4)O(3) multilayers become rough, and complex a-domain configurations appear.
关键词:
ferroelectrics;transmission electron microscopy;microstructure;ferroelectric thin-films;misfit relaxation mechanisms;domain;configurations;heterostructures;polarization
梁旺胜
,
陶冶
,
刘红亮
物理测试
利用磁过滤阴极电弧镀在硬质合金上沉积厚度约2～3μm的TiA1N薄膜,并用MEVVA源离子对TiA1N薄膜注入金属离子V+和Nb+.应用北京同步辐射装置(BSRF)的同步辐射光源,采用掠入射X射线衍射(GIXRD)的方法对TiA1N薄膜表面离子注入层的微观结构进行分析研究.结果表明:未经过离子注入的TiA1N薄膜主要组成相是没有择优取向的Ti3AlN伴有少量A1N,而较小剂量(1×1017ions/cm2)的离子注入都可以使Ti3AlN产生(111)上的择优取向和细化晶粒,且A1N消失;当离子注入的剂量达到5×1017ions/cm2时,注入V+的Ti3AlN择优取向变为(210),并产生TiN相;注入Nb+的各个衍射峰完全消失,说明TiA1N薄膜表面离子注入层被非晶化,结合透射电镜的研究结果,观察到非晶层的厚度约为80～100 nm.
关键词:
同步辐射
,
掠入射
,
X射线衍射
,
离子注入
,
TiA1N薄膜
乌仁图雅
,
段旭来
,
赵凤岐
,
苏日古嘎
材料科学与工艺
采用Lee-Low-Pines（LLP）变分法研究纤锌矿量子阱材料中电子-声子相互作用有关问题,给出纤锌矿GaN/AlxGa1-xN和InxGa1-xN/GaN量子阱材料中极化子基态能量和第一激发态到基态的跃迁能量随量子阱宽度和材料组分的变化关系.研究中考虑了纤锌矿量子阱材料中光学声子模各向异性以及声子频率随波矢的变化关系.同时还对运用LLP变分方法计算极化子能量时所采用的几种不同处理方法进行了分析和讨论,并给出相应的数值计算结果.
关键词:
纤锌矿
,
量子阱
,
极化子
顾乐民
,
胡朗
,
姚爱华
,
王德平
功能材料
采用了N-乙酰-L-半胱氨酸为稳定剂,通过水热法制备了荧光发射峰可调、粒径均匀且结晶性能良好的ZnxCd1-xSe合金量子点,并采用紫外-可见光吸收光谱（UV-Vis）、荧光光谱（PL）、X射线衍射（XRD）、高分辨透射电镜（HRTEM）等对其结构和性能进行了表征。重点研究了Cd2＋/Zn2＋比值、初始溶液pH值、水热反应温度和时间等实验条件对ZnxCd1-xSe量子点荧光性能的影响。研究表明所制备的量子点荧光量子产率高（35%）,荧光发射谱半峰宽窄（FWHM〈50nm）,有望作为生物荧光标记物。
关键词:
CdSe荧光量子点
,
水热法
,
稳定剂
