立方氮化硼(c-BN)薄膜的光学带隙

用两步射频溅射法在n型Si(111)片和熔融石英片上沉积出不同体积分数的立方氮化硼(c-BN)薄膜,薄膜的成分由傅里叶红外吸收谱标识;用紫外-可见分光光度计测量了沉积在石英片上的BN薄膜的透射光谱T_e(λ)和反射光谱R_e(λ),薄膜的厚度用台阶仪测得。由透射、反射光谱计算了薄膜的光吸收系数a,进而采用有效的中间形式,确定了氮化硼薄膜的光学带隙。结果表明:随着c-BN体积分数的增加,光学带隙随之增大。确定出的光学带隙和经验公式的计算结果相吻合。     

Ag基钎料钎焊立方氮化硼的焊接性与微观结构

在不同真空钎焊温度和保温时间条件下,研究了Ag基活性钎料钎焊立方氮化硼的焊接性与微观结构。试验结果表明:钎料中Ti的质量分数为12%、钎焊温度为950℃、保温时间为20 min时可实现Ag-Cu-Ti活性钎料与立方氮化硼的牢固连接。Ag-Cu-Ti活性钎料对c-BN的润湿性较好,界面结合紧密,并在界面处形成反应层。微观分析表明:钎焊过程中Ag-Cu-Ti合金钎料中的Ti向c-BN磨粒表面富集,并与c-BN磨粒表面N和B元素发生反应,形成TiN和TiB2,实现了Ag-Cu-Ti活性钎料与立方氮化硼磨粒的化学冶金结合。     

工作气压对氮化硼薄膜场发射特性的影响

利用射频磁控溅射方法，在n型(100)Si基底上沉积了氮化硼(BN)薄膜，并在超高真空系统中测量了BN薄膜的场发射特性．研究发现，沉积时工作气压的变化对BN薄膜的场发射特性有很大影响，工作气压为2Pa时沉积的BN薄膜样品的场发射特性较好，其阈值电场为6V/μm，场发射电流为320μA／cm^2．F—N曲线表明，在外加电场的作用下，电子是通过隧道效应穿透BN薄膜表面势垒发射到真空的．     

衬底及压强对磁控溅射ZnO薄膜表面形貌的影响

在压强为0.5Pa和0.7Pa的情况下,采用磁控溅射法分别在Si及石英玻璃衬底上生长ZnO薄膜。利用原子力显微镜对ZnO薄膜的表面形貌进行观察,研究了压强及衬底对薄膜表面形貌的影响。研究表明:在Si衬底上生长的ZnO薄膜,压强为0.7Pa时比压强为0.5Pa时表面粗糙度要大;在相同溅射气压(0.7Pa)下,Si衬底上得到的ZnO薄膜质量明显优于石英玻璃衬底上的。     

电弧离子镀CrN_x薄膜的组织结构与性能研究

采用电弧离子镀技术在高速钢(HSS)基体上制备CrN_x薄膜,考察氮气气压对CrN_x薄膜的表面形貌、结构、显微硬度及摩擦系数的影响。用扫描电镜、X射线衍射仪、显微硬度计、摩擦磨损试验机等分别测试分析薄膜的表面形貌、薄膜的结构、显微硬度以及摩擦系数。结果表明,氮气气压较低时(0.1Pa),薄膜以Cr相为主;随着氮气气压的升高(0.5~4.0Pa),薄膜中出现了Cr_2N和Cr的混合相,薄膜以Cr_2N相为主;随着氮气气压的升高,薄膜的显微硬度在氮气气压为0.5Pa和4.0Pa时出现极值,CrN_x薄膜的最大摩擦系数和平均摩擦系数都有所减少。     

脉冲激光沉积AlN薄膜的工艺优化与机械性能

采用脉冲激光沉积(PLD)方法在单晶Si衬底上制备AlN薄膜.利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)对薄膜的形貌和微观结构进行了分析;采用显微硬度仪、球-盘式磨损试验机和涂层自动划痕仪测试了薄膜的机械性能.通过正交实验,分析了工艺参数与AlN薄膜硬度之间的关系,得出沉积气压是对薄膜硬度影响大的因素,并研究了沉积气压对AlN薄膜表面形貌、微观结构、沉积速率、硬度、结合力和摩擦性能的影响.实验结果表明:所制备的薄膜均为非晶结构,随着沉积气压的上升,薄膜沉积速率降低,薄膜表面粗糙度降低,摩擦系数变小,当气压由0.1Pa增加到1Pa时,薄膜的硬度和耐磨性提高,但是随着气压进一步增大,其硬度和耐磨性下降.     

直流磁控溅射工艺参数对β-FeSi_2薄膜性能的影响

采用室温直流磁控溅射Fe-Si组合靶的方法,经过后续Ar气氛围退火,在单晶Si(111)衬底上生长β-FeSi2薄膜。研究了溅射功率、工作气压、Ar气流量、沉积时间等工艺参数对β-FeSi2薄膜结构特性及电学特性的影响,通过Raman、Hall、X射线衍射(XRD)等测试对其性能进行表征,对工艺参数进行了优化,在溅射功率为80W、工作气压为1.3Pa和Ar气流量为35SCCM时溅射沉积Fe-Si薄膜,不仅可以得到单一相的β-FeSi2,而且薄膜结晶质量较好。最终,在上述实验条件下制备得到的未掺杂的β-FeSi2薄膜是n型导电的,β-FeSi2薄膜中载流子浓度约为3.3×1016cm-3,迁移率为381cm2/Vs。     

工作气压对TiO2薄膜结构的影响

用射频磁控溅射方法以纯金属钛做靶材在氩氧混合气体中制备了TiO2薄膜，Raman光谱测量表明，工作气压从0．2Pa变化到2Pa时，TiO2薄膜的结构由金红石相变化到锐钛矿相，厚度对TiO2薄膜结构没有明显影响．     

金刚石薄膜的制备及透射率研究

用磁控溅射法制备金刚石薄膜,研究了工作气压、溅射电流、镀膜时间三个参数对金刚石薄膜透射率的影响。得到最佳工艺参数:工作气压1.3Pa,溅射电流0.4A,镀膜时间2min。镀制的金刚石薄膜可以作为红外元件的保护膜与增透膜。     

CaO稳定ZrO_2陶瓷Rietveld定量相分析

采用质量分数7%CaO稳定的ZrO2粉为原料,通过添加质量分数0.0~2.0%H3BO3助剂,经1 700℃2、h常压烧结制备得到CaO稳定的ZrO2陶瓷(CSZ)。采用XRD对烧结样品进行物相组成分析,运用Rietveld全谱拟合定量相分析方法对陶瓷中相组成的含量进行计算。结果表明:烧结样品由立方相和四方相ZrO2组成,立方相的含量随着H3BO3添加量的增加而降低,四方相与立方相的比值随H3BO3添加量的变化基本呈线性关系。Rietveld全谱拟合分析能准确表征CSZ中物相组成及含量(四方相与立方相)变化,为氧化锆陶瓷物相组成及含量变化对其性能影响的深入研究奠定基础。     

Relationship between the orientation of texture and heteroepitaxy of diamond and related materials films on silicon single crystal and the valence electron structure of the interface

Diamond and cubic boron nitride films have already been applied practically because of their excellent properties. The specific orientations of the films have special meaning on their application in optics and microelectronics fields. In this paper, the relative electron density differences of the interface between the different crystal planes of silicon substrate and those of diamond and cubic boron films are calculated with the empirical electron theory in solids and molecules. Analyses on the calculation results show that in the range of the researched films, the smaller the relative electron density difference between the film and the substrate is, the stabler the film is in thermodynamics. Therefore, the electron density difference is the essential factor of determining the orientation of the texture and heteroepitaxy of the films. The deductions accord well with the experimental facts. The calculation methods and the theory not only provide a new angle of view for the research of the growth mechanism of diamond film and cubic boron nitride film on the silicon substrate, but also provide a possible direction for the prediction of the orientation of other films. Supported by the Research Project of the Ministry of Education of China (Grant No. 02018) and the Beijing Natural Science Foundation (Grant No. 2072014)     

金刚石类超薄膜的力学性能和表面性质与掺杂剂对它的影响

用经典的力场方法对金刚石（C）、氮化硼（BNx）和氮化碳（CNx）结晶硬涂层膜的力学性能进行了探讨,确定原子结构、本体和杨氏模量为膜厚度的函数。探讨了吸附物对金刚石模量或表面张力的影响。另外,研究了不同氮化物中氮浓度以及不同取向和键合环境（sp^2和sp^3）下氮原子对模量的影响,揭示了系统的规律。同时,测定了空位对硬度的影响。     

Low pressure synthesis of boron nitride with(C2H5)2O·BF3 and Li3N precursor

Cubic boron nitride(c-BN) was synthesized through benzene thermal method at a lower temperature of 300 ℃ by selecting liquid(C2H5)2O·BF3 and Li3N as reactants. Hexagonal boron nitride(h-BN) and orthorhombic boron nitride(o-BN) were also obtained. The samples were characterized by X-ray powder diffractometry and Fourier transformation infrared spectroscopy. The results show that all the BF3, BCl3 and BBr3 in the same family compounds can react with Li3N to synthesize BN since the strongest bond of B-F can be broken. Compared with BBr3, liquid (C2H5)2O·BF3 is cheaper, less toxic and more convenient to operate. Li3N not only provides nitrogen source but also has catalytic effect on accelerating the formation of c-BN at low temperature and pressure.     

氮化硼对水性膨胀型防火涂料性能的影响

对六方氮化硼和立方氮化硼分别进行了剥离和羟基化改性,并采用X射线衍射、红外光谱分析、BET比表面积分析和热重分析对其结构进行了表征。将剥离前后的六方氮化硼,以及羟基化改性前后的立方氮化硼作为功能性填料应用于水性膨胀型防火涂中,研究了这4种氮化硼对水性膨胀型防火涂料性能的影响。结果表明,它们均能明显提高膨胀型防火涂料的阻燃性能,其中剥离后的六方氮化硼的阻燃效果最好。羟基化改性以及剥离均可提高氮化硼阻燃性能。剥离不仅可以提高六方氮化硼的阻燃性,还可以提高其涂料的耐水性,可能是因为剥离后的六方氮化硼纳米尺寸更小,更趋近于片状（层数减少）,利于在涂料以及碳层中的均匀分散,但羟基化改性由于提高了立方氮化硼的表面亲水性,因而降低了其涂料的耐水性。     

电沉积法制备PbS薄膜的XRD分析

采用阴极恒电压法在ITO导电玻璃表面沉积了PbS薄膜,并用X-射线衍射仪(XRD)对薄膜的结构进行了表征,研究了沉积电压对薄膜的晶相组成的影响.结果表明:在U=3.0 V时,可制备出沿(111)晶面取向生长的立方相PbS薄膜;随沉积电压从3.0 V增加到4.5 V,薄膜的生长取向从(111)晶面变为(200)晶面,且PbS衍射峰的强度越来越强,到18 V时达到最强.     

表面覆盖氮化硼膜的金刚石膜的场发射特性

利用热丝化学气相沉积（HFCVD）方法在Si衬底上生长了4μm厚的金刚石膜,然后利用射频磁控溅射方法在金刚石膜上沉积了100nm厚的六角氮化硼（h—BN）薄膜．在超高真空系统中测试了覆盖氮化硼（BN）薄膜前后金刚石膜的场发射特性,结果表明覆盖BN薄膜后的金刚石膜的场发射特性明显提高,开启电场由14V／μm升到8V／μm．F—N曲线表明,覆盖BN薄膜后的金刚石膜在强电场区域的场增强因子有所降低,这可能归因于场发射点随着电场的增强而改变．     

气体压强对n型a-Si:H薄膜光学性能的影响

用射频等离子增强化学气相沉积(RF-PECVD)制备磷掺杂氢化非晶硅(a-Si:H)薄膜,研究了辉光放电气体压强(20~80 Pa)对薄膜折射率、消光系数、光学带隙以及氢含量的影响;用激光拉曼光谱研究了气体压强对a-Si:H薄膜微结构的影响,并与薄膜的光学性能进行了综合讨论。结果表明,随着辉光放电气体压强的增加,a-Si:H薄膜的光学带隙和氢含量都有不同程度的增大,但折射率和消光系数却逐步减小;与此同时,薄膜内非晶网络的短程和中程有序程度逐渐恶化。     

Development of an ultrahard nanotwinned cBN micro tool for cutting hardened steel

Binderless nanotwinned cubic boron nitride (nt-cBN) synthesized from onion-structured BN precursors under high pressure and high temperature shows a very fine microstructure consisting of densely lamellar nanotwins (average thickness of 4 nm) within nanograins. The unique nanotwinned microstructure offers high hardness, wear resistance, fracture toughness, and thermal stability which are essential for advanced cBN tool materials. Thus, a circular micro tool of nt-cBN was fabricated using femtosecond laser contour machining followed by focused ion beam precision milling. Thereafter turning tests were performed on hardened steel using the studied micro tool. To evaluate the cutting performance, the machined surface quality and subsurface damage of the hardened steel were characterized. The wear mechanism of the nt-cBN micro tool was also investigated. It is found that the fabricated nt-cBN micro tool can generate high quality surface with surface roughness less than 7 nm and nanograin subsurface of about 500 nm deep. In addition, abrasive wear is found to be the dominant wear mechanism of the nt-cBN micro tool in turning hardened steel. These results indicate that nt-cBN has outstanding potential for ultra-precision cutting hardened steel.     

Structure and Composition of Crystalline Carbon Nitride Films Synthesized by Microwave Plasma Chemical Vapor Deposition

Crystalline carbon nitride thin films were prepared on Si (100) substrates by a microwave plasma chemical vapor deposition method, using CH4/N2 as precursor gases. The surface morphologies of the carbon nitride films deposited on Si substrate at 830℃ are consisted of hexagonal crystalline rods. The effect of substrate temperature on the formation of carbon nitrides was investigated. X-ray photoelectron spectroscopy analysis indicated that the maximum value of N/C in atomic ratio in the films deposited at a substrate temperature of 830℃ is 1 .20, which is close to the stoichiometric value of C3N4. The X-ray diffraction pattern of the films deposited at 830℃ indicates no amorphous phase in the films, which are composed of β- and α-C3N4 phase containing an unidentified C-N phase. Fourier transform infrared spectroscopy supports the existence of C-N covalent bond.