Occurrence and elimination of in-plane misoriented crystals in AIN epUayers on sapphire via pre-treatment control

AlN epilayers are grown directly on sapphire （0001） substrates each of which has a low temperature AlN nucleation layer. The effects of pretreatments of sapphire snbstrates, including exposures to NH3/H2 and to H2 only ambients at different temperatures, before the growth of AlN epilayers is investigated. In-plane misoriented crystals occur in N-polar AlN epilayers each with pretreatment in a H2 only ambient, and are characterized by six 60°-apart peaks with splits in each peak in （1012） phi scan and two sets of hexagonal diffraction patterns taken along the [0001] zone axis in electron diffraction. These misoriented crystals can be eliminated in AlN epilayers by the pretreatment of sapphire substrates in the NH3/H2 ambient. AlN epilayers by the pretreatment of sapphire substrates in the NH3/H2 ambient are Al-polar. Our results show the pretreatments and the nucleation layers are responsible for the polarities of the AlN epilayers. We ascribe these results to the different strain relaxation mechanisms induced by the lattice mismatch of AlN and sapphire.     

粮仓效应的实验设计

设计制作了观测静态颗粒物质粮仓效应的简单实验系统.实验数据充分地展现了颗粒物质与筒仓壁之间摩擦力的“巨大”作用以及具有流动性质的颗粒物质与静态流体的显著差别,且实验结果与理论计算吻合很好.     

A Novel Frequency Measurement Method Suitable for a Large Frequency Ratio Condition

As for the obstacles to direct comparison between superhigh and lower frequencies, we accomplish the accurate comparison between low and microwave frequencies with the 10^5 ratios of the operating frequencies on the basis of phase comparison between the signals whose frequencies are related by an arbitrary integer. This method is simple and accurate, and will be widely used as a special frequency comparison approach.     

凝胶压井液用阴离子改性胍胶的制备及其流变性能

以环氧氯丙烷和NaHSO_3为原料,Na_2SO_3为引发剂,乙二胺四乙酸二钠(EDTA-2Na)为络合增效剂,经酸催化开环反应合成了磺酸型两性表面活性剂中间体3-氯-2-羟基丙磺酸钠,然后在弱酸性条件下与胍胶通过醚化反应制备了磺酸基羟丙基胍胶,其结构经IR表征。通过正交实验确定了合成配方和条件的最优结果,研究了反应温度、pH、改性胍胶浓度对成胶后凝胶的表观粘度影响,并测试了最佳条件下制备的凝胶和对应稀溶液的流变性能。结果表明:氧氯化锆可有效交联改性胍胶,在pH为6、温度为70℃、改性胍胶浓度为0.6%的条件下制备的凝胶具有剪切变稀性质以及较好的粘弹性。     

过氧氨三乙酸钛配合物分子前体热分解制备纯钛基复氧化物

在pH=2.5～4.0的条件下,以四氯化钛、过氧化氢和氨三乙酸为原料反应得到四种过氧酸钛配合物(NH₄)₄[Ti₂O～(O₂)2(ta)₂]·4H₂O (1), K₄[Ti₂O(O₂)₂(ta)₂]·6H₂O (2), Sr₂[Ti₂O(O₂)₂(ta)₂]·10H₂O (3)和Ba₂[Ti₂O(O₂)₂(ta)₂]·10H₂O (4) (H3ta=C₆H₆O₆N).配合物的EA, UV-vis, IR和X射线单晶分析表明它们含有相同的双核过氧氨三乙酸钛的阴离子结构,钛原子与过氧基团、四齿氨三乙酸和桥氧七配位.3和4中的阳离子锶和钡分别与周围的水分子和羧基氧形成九配位和十配位.配合物1, 3和4在空气中600℃分解,XRD分析表明分别得到金红石型TiO₂, SrTiO₃和四方BaTiO₃纯相.     

电流型探测器单粒子灵敏度标定的原理及应用

 采用电荷模数转换记录单个脉冲电荷的方法,标定了单能射线在电流型闪烁探测器中产生的平均电流,从而得到其灵敏度。标定结果与传统的电流法在±8%的范围内一致。该标定方法准确度高,扣除本底容易,对标定源的强度要求也大大降低。加上飞行时间法,还可对粒子进行甄别,能在中子-γ射线混合场中将中子和γ射线的电荷贡献分开,得到探测器对每种射线单独的灵敏度。该方法适用于在单个脉冲电荷信噪比较高的场合下标定脉冲电流型探测器。     

CO2势能面和振动激发态的理论研究

采用振动自洽场-组态相互作用(SCF-CI)方法通过实验振动光谱优化了CO₂分子的势能函数,由该势能函数计算得到的纯振动光谱数据与实验值相比,所有能级的误差均在4cm^-1以内,均方根偏差为1.50cm^-1,所预测的Π态振转光谱也与实验值很接近.     

纳米级金刚石超微细粉的性能参数分析

本文对用爆炸法合成的两批纳米级金刚石超细粉进行了初步研究,ＸＲＤ表明样品Ⅰ和样品Ⅱ是立方相金刚石晶体结构,粒径平均为～４０;ＦＴＩＲ光谱显示样品Ⅰ中含有较多的石英杂质;测量了纳米级金刚石超细粉的拉曼光谱,对其不同于大块金刚石拉曼峰的现象,用量子限制效应模型作出解释。     

螺旋调节式变阻器

本设计出了一个调节分辨率极高的螺旋调节变阻器。     

简式多量程微电流源数字计量仪及其应用

介绍了“简式多量程微电流源数字计量仪”的结构、原理及应用。该仪器可用于测量光电管中光电流与真空电离规管中离子流计量电路等各种微电流源领域中。