Field Emission Characteristics of BN Films Treated with H2 and O2 Plasma

BN films were synthesized on the (100)-oriented surface of n-Si (0.008-0.02Ωm) by rf magnetron sputtering physical vapor deposition (PVD). A BN film was first treated with H2 plasma for 60 rain and then the H2 treated sample was treated with O2 plasma for 15rain. The films were characterizes by using Fourier transform infrared spectra (FTIR) and atomic force microscopy (AFM). The field emission characteristics of BN films were measured in an ultrahigh vacuum system. A turn-on electric field of 8 V/μm and a current of 400μA/cm^2 were obtained for the BN film treated with H2 plasma. The results show that the surface plasma treatment makes no apparent influence on the surface morphology of the BN films. The transformations of the sample emission characteristics have to do with the surface negative electron affinity (NEA) of the films possibly. The turn-on electric field of the BN film treated with H2 plasma is lower than that without treatment, which possibly attributes to the surface NEA effect. The surface NEA of the H2 treated BN film is lost after O2 plasma treatment.     

光谱指数的植物叶片叶绿素含量估算模型

叶片叶绿素能够有效监测植被的生长状况,利用光谱指数反演植被叶绿素含量是目前的通用方法。实测了盐生植物光谱反射率和叶片叶绿素含量。对SPAD值进行变换,对比Pearson与VIP方法探讨盐生植被叶片叶绿素含量与植被指数的相关性并进行精度验证,从中选出最佳拟合模型。研究表明,通过对Pearson与VIP相关性分析,最终选定VIP方法建立植被指数的叶片叶绿素估算模型,NDVI₇₀₅,ARVI,CI_{red edge},PRI,VARI,PSRI和NPCI的VIP值均大于0.8,因此选定这七个植被指数为最优植被指数;预测结果显示,所有模型的相关性都在0.7以上,预测值与实测值相关性最好的是经过倒数变换的SPAD值,R=0.816,RMSE=0.007。基于VIP方法的反演模型能较好地估算研究区植被叶绿素含量,该方法为植物叶绿素含量诊断的实际应用提供了重要的理论依据和技术支持。     

基于舌诊NIR反射光谱血清总蛋白含量的无创测量

采用舌诊近红外反射光谱对人体血清总蛋白(TP)含量进行无创检测。采集58例舌尖反射光谱进行反射率归一化并记录相对应的血清总蛋白生化分析值,将样本分为训练集和预测集,运用主成分分析结合BP神经网络法和偏最小二乘算法分别建立预测模型。主成分分析结合BP神经网络模型对预测集进行预测,平均相对误差为7.35%,均方根误差为3.069 1 g·L-1,相关系数为0.902 1。偏最小二乘模型对预测集进行预测,平均相对误差为4.77%,均方根误差为0.130 1 g·L-1,相关系数为0.971 8。实验结果证实了舌诊近红外反射光谱可以较为准确地用于总蛋白含量的无创检测。     

Characteristics of grain growth of microarc oxidation coatings on pure titanium

Grainy titania coatings are prepared by microarc oxidation on pure titanium （TA2） substrates in a Na2SiO3NaF electrolytic solution. The coating thickness is measured by an optical microscope with a CCD camera. Scanning electron microscope （SEM） and x-ray diffraction （XRD） are employed to characterize the microstructure and phase composition of coatings. The results show that the coating thickness increases linearly as the treatment time increases. The coatings are mainly composed of anatase and rutile （TiO2）. With the increase of treatment time, the predominant phase composition varies from anatase to rutile, which indicates that phase transformation of anatase into rutile occurs in the oxidizing process. Meanwhile, the size of grains existing on the coating surface increases and thus the surface becomes much coarser.     

FT 合成用铁催化剂化学形态的研究

采用穆斯堡尔谱方法,研究了FT 合成用熔铁、沉淀铁、载体铁三种类型的催化剂在灼烧、还原、于合成气中反应后铁的化学形态及其变化。研究结果表明,铁催化剂中存在着助催化剂、载体与铁相间的相互作用,这种相互作用导致铁的化学形态变化及穆斯堡尔超精细参数的改变。     

Determination of the magnetocaloric effect associated with martensitic transition in Ni46CunMn38Sn12 and Ni50CoMn34In15 Heusler alloys

This paper presents a study of the inverse magnetocaloric effect （MCE） corresponding to martensitic transition using various experimental approaches for Ni46Cu4Mn38Sn12 and NisoCoMn34In]5 Heusler alloy. Through heat capacity measurements, it is found that the ＂giant inverse MCE＂ upon martensitic transition evaluated by the Maxwell relation in these alloys are unphysical results. This is due to the coexistence of both martensitic and austenitic phases, as well as thermal hysteresis during martensitic transition. However, careful study indicates that the spurious results during martensitic transition can be removed using a Clausius Clapeyron equation based on magnetization measurements.     

考虑晶粒度的GH4169高温合金微铣削残余应力仿真与实验研究

微细铣削中,由于受加工余量限制,铣刀每齿进给量非常小甚至小于材料内部晶粒尺寸。当切削在晶粒间进行时会造成切削不连续,从而使铣削过程颤振急剧增大,引起加工表面质量下降,严重影响微型零件的疲劳寿命和使用性能。本研究基于Voronoi图建立多晶体几何模型,通过仿真与实验验证的方法对刀具刃口圆弧半径、切削深度和晶粒尺寸对已加工表面残余应力的影响规律进行详细研究,建立多元线性回归模型并进行显著性检验。对经热处理后具备不同晶粒尺寸的高温合金GH4169进行微铣削实验,通过X射线衍射法测量工件进给方向已加工表面的残余应力值,将实验值与预测值进行对比,从而验证残余应力预测模型的准确性。结果表明,其误差分布在2.18%～7.35%,不超过10%,说明残余应力的预测模型准确性较高。     

水热合成奇异形态的ZnO晶体

本文采用水热法,以3mol/L KOH为矿化剂,填充度35;,温度430℃,在Zn(OH)2中添加SnCl2·2H2O,添加量为Sn2+:Zn2+=2;条件下,合成出ZnO晶体.产物中除了大量短六棱柱形晶体外,还出现了部分冰激凌形晶体.六棱柱形晶体具有典型的ZnO特征,显露正极面c{0001}、负极面-c{000-1}、柱面m{10-10}、正锥面p{10-11}和负锥面-p{10-1-1}.而冰激凌形晶体有明显的六棱锥晶体外壳,X光能谱(EDS)检测证实晶体各部位的组分均为ZnO.     

In掺杂对水热法合成ZnO晶体形貌的影响

本文采用水热法,在ZnO中添加In2O3为前驱物,3mol/L KOH作矿化剂,温度430℃,填充度35;,反应24h,制备了掺In的ZnO晶体.未掺杂In2O3合成的纯ZnO晶体呈六棱锥状,显露负极面-c{0001}、六棱锥面+p{1011}和-p{1011},一般不显露{0001}面.前驱物中掺杂In2O3所合成的ZnO晶体呈六角片状,直径约为5～20 μm,大面积显露{0001}面,另外还显露正锥面+p{1011}、负锥面-p{1011}和负极面-c{0001}.由此可见In掺杂可以明显的改变晶体的形态,使c轴极性快速生长趋向得到明显改善,有利于降低晶体生长缺陷.当采用ZnO晶片为籽晶时,通过水热反应在晶片上生长了一层掺In的ZnO薄膜,通过Hall参数测量得到晶体膜层的电子迁移率约为22cm2/(V·s),载流子浓度约为2×1020 cm-3,具有良好的导电性,同时也说明In可以微量掺入氧化锌晶体.     

无磁光学非互易实验教学与设计

作为一种有趣的非线性光学效应,四波混频在众多领域有重要的应用。本文利用四波混频效应实现无磁的光学非互易,分别研究了信号光失谐量、泵浦光光功率和气体池温度等参量对信号光正向和反向传播时透过率的影响。实验结果表明改变这些参量可有效地调控正向透过率,而极低的反向透过率几乎不受影响。该文对于大学物理实验教学具有一定的参考价值。