NING Li-Na Zhi-Hong FENG Ying-Ming WANG Kai ZHANG Zhen FENG
材料科学技术（英文）
Two-inch semi-insulating SiC bulk crystals with resistivity higher than 1×106 Ωcm were achieved by vanadium
doping during sublimation. Secondary-ion-mass-spectrometry (SIMS) was employed to determine the concen-
tration of impurities in the crystals, such as B, Al, V and N. These results indicated that the concentration of
nitrogen and aluminum kept on decreasing and the concentration of B and V was almost constant during the
whole growth. An inner crucible was used to control the exhausting of vanadium, which made the uniformity
of the high resistivity (>1×106 Ωcm) in the wafer up to 80%. High-performance AlGaN/GaN high-electron-
mobility-transistor (HEMT) materials and devices were grown and fabricated on semi-insulating 6H-SiC sub-
strates. The two-dimensional electron gas (2DEG) mobility at room-temperature was 1795 cm2/V•s. The
charge carrier concentration of the substrate determined by capacitance-voltage (C-V) test was 7.3×1015 Ωcm−3.
The device with a gate width of 1 mm exhibits a maximum output power of 5.5 W at 8 GHz, which proves
the semi-insulating property of the substrates indirectly.
关键词:
Silicon Carbide
,
半绝缘
,
钒掺杂
,
AlGaN/GaN HEMT
Journal of Physics-Condensed Matter
Based on ab initio total energy calculations, Li, Na and Ag interstitials are found to be stable with at least a 1.56 eV energy barrier to transform to a zinc substitutional site in ZnO, whereas K interstitial has a relatively small energy barrier at 0.79 eV. The isolated dopant substitutional defects (LiZn, NaZn, KZn and AgZn) are found to be rather stable, with at least a 3.4 eV energy barrier to transform to an interstitial site. All of the dopant interstitials (Lii, Nai, Ki and Agi) are fast diffusers. The diffusion of Li interstitial is isotropic, whereas the diffusion of Na, K and Ag interstitials is highly anisotropic. Fundamental processes of the vacancy-assisted mechanisms are systematically investigated and specific values of the energy barriers are obtained.
关键词:
augmented-wave method
刘颖
腐蚀与防护
为了探讨在熔融碳酸盐中加入氯化物对不锈钢的腐蚀作用的影响,采用浸泡方法研究了304和310不锈钢在添加了氯化物的700℃熔融(Li,Na,K)2CO3中的腐蚀行为.结果表明,两种不锈钢都遭受了严重腐蚀,不锈钢的快速腐蚀与循环的氯化-氧化反应有关.
关键词:
不锈钢
,
(Li,Na,K)2CO3-(Na,K)Cl
,
熔盐腐蚀
,
氯化-氧化
胡标
,
尹明
,
王庆平
,
闵凡飞
,
杜勇
兵器材料科学与工程
基于文献报道的实验数据,采用相图计算(CALPHAD:CALculation of PHAse Diagrams)方法对V-M(M=Li,Na,K,Sc,Ag)5个二元系进行相图热力学研究.通过热力学优化计算获得了一套描述液相、(V)、(Li)、(Na)、(K)、(αSc)、(βSc)和(Ag)相的热力学参数.V-Li、V-Na和V-K体系中的气相视为由组元V、Li、Li2、Na、Na2、K和K2混合的理想气体.与实验相图数据对比表明,获得的热力学参数能够准确地描述实验相平衡数据.
关键词:
V-M(M=Li,Na,K,Sc,Ag)
,
CALPHAD方法
,
相图
,
热力学模型
梁兴华
,
王矜奉
,
郑立梅
功能材料与器件学报
doi:10.3969/j.issn.1007-4252.2007.02.014
采用传统的氧化物固溶工艺制备了(Na0.51K0.44Li0.05)Nb092Ta0.08O3和助烧剂Na5.4Cu13Sb10O29.对(Na0.51K044Li0.05)Nb0.92Ta0.08O3添加助烧剂Na5.4Cu1.3Sb10O29的研究表明,助烧剂能大幅度提高(Na0.51K0.44Li0.05)Nb0.92Ta0.08O3的压电和机电耦合性能.质量百分比为4%Na5.4Cu1.3Sb10O29掺杂的(Na051K0.44Li0.05)Nb092Ta0.08O3具有高的压电应变常数(d33=266pC/N),高的机电耦合系数kt(46.7%)、k33(63.7%),较低的损耗(tanδ=1.8%),和高的居里温度(391℃).这些参数表明,Na5.4Cu1.3Sb10O29掺杂的(Na0.51K0.44Li0.05)Nb0.92Ta0.08O3是替代锆钛酸铅且具有很好的应用前景的无铅压电陶瓷.
关键词:
无铅压电陶瓷
,
机电耦合系数
,
压电常数
,
介电常数
陈熙萌
,
吴翠娥
,
刘兆远
,
于得洋
,
祁中
,
王强
,
杨治虎
,
刘惠萍
原子核物理评论
doi:10.3969/j.issn.1007-4627.2002.02.024
采用交叉束方法, 利用负离子源产生的3-19 keV的Li-和Na-轰击惰性气体靶He, Ne和Ar, 通过静电偏转和位置灵敏探测器区分碰撞后中性粒子束和负离子束, 测量了不同碰撞系统的中性粒子计数与相应入射负离子计数的比值R(E), 并得到R(E)与入射负离子能量、负离子种类和靶原子种类的关系.
关键词:
交叉束
,
负离子解离
,
负离子-原子碰撞
High Temperature Materials and Processes
The ternary carbonate eutectic mixture of Li(2)CO(3), K(2)CO(3) and Na(2)CO(3) as a heat transfer and storage medium has excellent thermophysical properties, but with high viscidity as compared with some other inorganic salts such as chlorides and nitrates. The addition of chlorides or fluorides to molten carbonates may improve their fluidity, but possibly making the melt become more corrosive. In this study, the corrosion behavior of type 304, 310 and 316 stainless steels in an eutectic (Li,Na,K)(2)CO(3) melt with and without an eutectic mixture of NaCl and KCl at 973K in air have been examined. The experimental results indicated that 310 steel shows a much better corrosion resistance in molten carbonates than both 304 and 316 steels, due to the formation of a continuous LiCrO(2) scale. The addition of chlorides to carbonates melt accelerated the corrosion of the steels, especially 310 steel, producing scales with more porosity.
关键词:
Stainless steels;(Li,Na,K)(2)CO(3);(Na,K)Cl;molten salts corrosion;latent-heat-storage;potassium carbonates;lithium;sodium
郭飞云
,
庄乃锋
,
赵斌
,
陈建中
人工晶体学报
采用Czochralski法生长了Li_(0.067)Na_(0.933)Tb(MoO_4)_2晶体,并测试了Li~+在NaTb(MoO_4)_2晶体中的有效分凝系数.由粉末X射线衍射数据计算了晶体的晶胞参数.室温下,采用消光法测试了Li_(0.063)Na_(0.933)Tb(MoO_4)_2晶体在532 nm、633 nm和1064 nm处的费尔德常数,分别为-293.6 rad·m~(-1)·T~(-1)、-200.5 rad·m~(-1)·T~(-1)和-68.6 rad·m~(-1)·T~(-1),与纯NaTb(MoO_4)_2相比,其费尔德常数均有所增加.结果表明,在1064 nm处Li_(0.067)Na_(0.933)Tb(MoO_4)_2晶体有较高的磁光优值.
关键词:
磁光晶体
,
提拉法
,
费尔德常数
,
磁光优值
陶明慧
,
张星祥
,
张宇
,
任建岳
,
李新娥
液晶与显示
doi:10.3788/YJYXS20112601.0105
针对某航空相机的设计要求,提出了一种可行的多模式驱动时序设计方法.采用柯达公司的KAI-2093行间转移型面阵CCD传感器.结合它的结构特点和双通道数据传输的思想分析了传感器驱动时序关系,提出了3种驱动模式:binning、no-binning和TDI模式.以Ahera公司的FPGA芯片EP1C6Q240作为时序发生器并实现数据的缓存和拼接,从而实现了时序发生器与数据处理器的一体化设计.在QUARTUSII7.0开发环境下采用VHDL语言编程,通过Modelsim AE6.1b实现数据缓存器的仿真.实测结果表明,所设计的驱动时序满足KAI-2093的时序要求,binning模式下帧频可达60帧/s,120帧/s等,满足高速跟踪要求;no-binning模式下全帧输出帧频可达30帧/s;TDI模式下能保证CCD长时间工作而不影响成像质量,该没计方法提高了系统的集成度和抗干扰能力.
关键词:
航空相机
,
binning模式
,
TDI模式
,
数据缓存
,
数据拼接
,
FPGA
李志友
,
黄伯云
,
汤春峰
,
刘志坚
,
曲选辉
功能材料
用柠檬酸盐溶胶-凝胶工艺制取了三种β-MxV2O5氧化物Li0.3V2O5、Na0.33 V2O5和K0.25V2O5;TG和DTA试验显示干凝胶焙烧过程中出现两个吸热峰,中间有一个放热峰;XRD分析表明高温处理时Li0.3 V2O5可氧化成LiV3O8和V2O5,而Na0.33V2O5和K0.25有较好的化学稳定性;模拟Li-B合金/LiCl-KCl/β-MxV2O5(或α-V2O5)热电池500℃放电试验表明β相阴极放电较α相平稳,但初始电压峰值略有降低,β-Li0.3V2O5相因具有较α-V2O5相更通畅的Li+快速扩散通道,且通道内没有Na+或K+大离子对Li+扩散的阻碍,放电最为平稳,有效比容量最高.
关键词:
溶胶-凝胶工艺
,
β相钒青石
,
热电池
,
阴极
