Al元素对Zr-Si-N复合膜的微结构与力学性能的影响

采用反应磁控溅射方法制备了一系列不同铝含量的Zr-Al-Si-N复合膜,用能谱仪、X射线衍射仪和显微硬度计对复合膜进行表征,研究了铝元素对Zr-Si-N复合膜的微结构和力学性能的影响.结果表明,当铝的原子分数N_(Al) ≤10.84%时,Zr-Al-Si-N复合膜中fcc-(ZrAlSi)N为主要相;当N_(Al) ≥14.67%时,Zr-Al-Si-N复合膜是fcc-(ZrAlSi)N和h-AlN的混合相;铝原子分数为4.80%时,Zr-Al-Si-N复合膜的显微硬度达到最大值43.92 GPa;随着铝原子含量的进一步增加,Zr-Al-Si-N复合膜的显微硬度迅速下降.对复合膜的致硬机理进行了讨论.     

电子晶体学图像处理及其在材料科学中的应用

本文指出，借助高分辨电子显微镜观察到的显微像并不总直观地反映晶 体结构，对于在特定离焦条件下拍摄到的结构像，其分辨率还要受显微镜分辨本领的限制，只有超高压高分辨电子显微镜才能直接给出原子分辨率的结构像。文章介绍了衍射晶体学与高分辨电子显微学相结合起来的优越性，和据此发展的电子晶体学图像处理技术，用此技术可以实现“从头”测定晶体结构，并能把中等电压电子显微镜得到的结构像分辨率约提高1倍，达到原子分辨率。文中举例介绍了此技术在测定晶体结构和缺陷中的应用。     

加氮对直流电弧等离子体喷射金刚石膜显微组织和断裂强度的影响

利用DcArcP1asmaJetcVD法制备搀杂氮的金刚石厚膜。研究了在反应气体cH。／Ar／H：中加入N!对金刚石膜显微组织和力学性能的影响。在固定H2、Ar、CH4流量的情况下改变N2的流量，即反应气体中氮原子和碳原子的变化比例(N／C比，范围从0．06～0．68)，同时在固定的腔体压力(4kPa)和衬底温度(800℃)下进行金刚石膜生长。用扫描电镜(SEM)观察金刚石膜形貌、用X射线衍射表征晶体取向，用三点弯曲的方法来测量金刚石膜的断裂强度。结果表明，氮气在反应气体中的大量加入，对直流等离子体喷射制备金刚石膜的显微组织和力学性能有显著的影响。     

时效处理对Al0.25 CrFeMn1.3Ni高熵合金显微组织演变及耐磨性的影响

采用真空磁悬浮炉熔炼了Al0.25CrFeMn1.3Ni高熵合金,利用场发射扫描电镜、X射线衍射和场发射电子探针显微分析等研究了不同温度时效处理对其显微组织及耐磨性能的影响.结果表明:铸态合金的组织由Cr-Mn-Fe-Ni FCC相基体、Al-Ni-Mn B2相粒状组织和Fe-Cr-Mn BCC相枝晶基体组成.时效处理...     

Ti(C,N)固溶体的N/C原子比对Ti(C,N)基金属陶瓷组织及力学性能的影响

本文以不同N/C原子比的Ti(C,N)固溶体为硬质相,通过真空烧结制备了Ti(C,N)基金属陶瓷。用三点弯曲法、洛氏硬度计、压痕法分别测得试样的抗弯强度、硬度、断裂韧性,并通过光学金相显微镜、XRD、SEM、EDS等手段研究了Ti(C,N)固溶体的N/C原子比对Ti(C,N)基金属陶瓷组织的影响规律。结果表明:在一定范围内随着N/C原子比的增大,Ti(C,N)固溶体在液相中溶解度下降,环形相的析出受到抑制,使得金属陶瓷的硬质相芯部逐渐细化且分散均匀,环形相厚度减薄。但Ti(C,N)固溶体的N/C原子比为6∶4及以上时,硬质相与液相之间的润湿性较差,使得金属陶瓷孔隙度增加,显微组织中开始出现亮白色的晶粒。随N/C原子比的增大,金属陶瓷的抗弯强度和硬度先增大后降低,断裂韧性逐渐降低。当Ti(C,N)固溶体的N/C原子比为5∶5时,金属陶瓷的综合力学性能最佳,其抗弯强度为2 429 MPa,硬度为92.2 HRA,断裂韧性为8.44 MPa·m~(1/2)。     

1Cr11Ni2W2MoV钢的离子渗氮

利用脉冲直流辉光等离子技术,对1Cr11Ni2W2MoV马氏体热强不锈钢进行不同工艺参数的离子渗氮。利用光学显微镜、显微硬度计、XRD对渗氮层的显微组织及硬度进行了分析。结果表明,在所选用的离子渗氮工艺参数下,1Cr11Ni2W2MoV钢渗层只由扩散层组成,渗氮温度≤560℃时,渗层主要由固溶N原子的α相组成,并伴有少量的γ'-Fe4N和CrN析出;随着渗氮温度的升高和渗氮时间的延长,固溶N原子的α相逐渐转变成γ'-Fe4N相,当处理温度达到590℃时,渗层主要由γ'-Fe4N和Cr N组成。离子渗氮后渗层的表面硬度较未渗氮前有显著的提高,在一定范围内,渗层的表面硬度和渗层深度都随着渗氮温度和渗氮时间的增加而增加,渗层硬度梯度分布也随着渗氮时间的延长变得平缓。     

LD11合金柴油机活塞铝裙的组织与性能

测试了LD11铝合金柴油机活塞铝裙的力学性能，利用光学显微境、场发射扫描电镜及透射电镜分析了活塞铝裙的微观组织结构，得出活塞铝裙微观组成相并探讨了微观组织结构与性能间的关系。     

Mo含量对CrMoN复合涂层的组织结构和性能的影响

采用直流反应磁控溅射技术在M2高速钢基片上制备了不同Mo含量的Cr Mo N复合涂层,研究了Mo含量的变化对Cr Mo N复合涂层成分、相结构、化学价态、截面形貌、显微硬度和摩擦性能等的影响.结果表明,随着Mo含量的增加,Cr Mo N复合涂层的相结构先转变为以fcc-Cr N相为基础的(Cr,Mo)N置换式固溶体,后转变为以fcc-g-Mo2N相为主的混合相,当Mo含量为69.3%(原子分数)时,伴有少量的bcc-Mo相生成;Cr Mo N复合涂层的显微硬度先增加后降低,在Mo含量为45.4%时具有最高值;当Mo含量大于45.4%时,在与对磨副摩擦过程中会生成大量的Mo O3相,降低了摩擦系数和磨损率.     

NdFeB纳米复合磁体的微观结构和磁畴结构显微分析

NdFeB纳米复合磁体中硬磁相的某些晶面间距与软磁相的几乎相等，因而采用常规透射电镜进行电子衍射或高分辩像直接鉴定物相相当困难。日本学者采用能谱(EDS)和电子能量损失谱(EELS)鉴定物相和测定了晶粒尺寸分布，并用洛伦兹力显微术研究了磁畴结分 析·检 测 构。样品采用熔体快淬法得到非晶后于973K退火结晶制得。其名义成份为Nd4.5Fe77B18.5，磁能积77KJ/m3，剩磁1.11T。用EELS研究了在997K温度退火的样品。衍衬像和EELS在加速电压为300kV配备有热场发射枪的JEM-3000F型TEM上完成。EDS在加速电压为200KV的JEM2010TEM上…     

1Cr18Ni10Ti不锈钢管扩口开裂失效分析

1Cr18Ni10Ti不锈钢导管在扩口时,喇叭口外表面出现了裂纹。采用光学显微镜、显微硬度计对钢管的表面形貌、显微组织、显微硬度进行了检测分析。结果表明:导管原材料在经氨分解气氛保护热处理中残留氨控制不当,在高温下分解出N原子,导致管材表面产生硬脆的渗氮层,塑性降低,造成扩口时开裂。     

A simple catalyst-free route for large-scale synthesis of SiC nanowires

A large number of SiC nanowires were fabricated by a simple catalyst-free method using silicon powders and expandable graphite as raw materials. Digital camera, X-ray diffractometer, Fourier transform infrared spectrometer, field-emission scanning electron microscopy and transmission electron microscopy demonstrate that a large number of loose products were obtained in graphite crucible. The products are composed of single crystalline 3C-SiC nanowires with lengths up to several tens of micrometers and diameters of 20-60 nm. The vapor-solid mechanism was proposed to interpret the growth procedure of SiC nanowires. The expandable graphite as carbon source can provide enough growth space for nanowires, which is helpful to improve the yield of SiC nanowires. The simple method provides a promising candidate for industrial fabrication of SiC nanowires.     

Aligned multi-walled carbon nanotubes on different substrates by floating catalyst chemical vapor deposition: Critical effects of buffer layer

Aligned multi-walled carbon nanotubes (MWCNTs) were synthesized by floating catalyst chemical vapor deposition on two types of substrates, with emphasis on the effects of an aluminum buffer layer. It has been revealed that the presence of the aluminum buffer layer on insulating/semiconducting silicon oxide/silicon wafer resulted in a higher growth rate, narrower diameter distribution, neater morphology and improved crystalline quality of MWCNTs. When an aluminum buffer layer is deposited on electrically conductive carbon paper, high yield CNTs can be achieved while no CNTs can be observed without this buffer layer. Morphology, structure and chemical states of the products were examined by field-emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. The generation of alumina from the aluminum buffer layer is thought to play an important role in promoting the nanotube growth. Detailed growth mechanism of MWCNTs was also discussed.     

Effect of Oxidation Time on Thermally Grown Oxide on GaN

Gallium oxide (Ga₂O₃) has been successfully grown on top of an n-type gallium nitride (GaN) substrate via thermal oxidation process which is performed in nitrous oxide ambient at 1000 °C. Effects of oxidation times on physical properties of the thermal oxide have been investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FESEM), and atomic force microscopy (AFM). XRD analysis discloses the presence of monoclinic β-Ga₂O₃ which is the most thermodynamically stable form of Ga₂O₃ on the GaN substrate after thermal oxidation. FTIR spectra shows a Ga-O vibration mode at the band around 620-660 cm^?1 for all the oxidized samples. Besides, FESEM and AFM results indicate that protrusions of grains are revealed on the surface after thermal oxidation. In addition, surface roughness of the oxide was also found to be increased with the increasing oxidation duration.     

Mo电极上磁控反应溅射AlN薄膜

采用射频反应磁控溅射法在Mo电极上沉积了AlN薄膜.研究了溅射气压、靶基距、溅射功率、衬底温度及N_2含量等不同工艺条件对AlN薄膜择优取向生长的影响.用XRD分析了薄膜的择优取向,用原子力显微镜、高分辨场发射扫描电镜表征了薄膜的形貌.实验结果表明,靶基距和溅射气压的减小,衬底温度及溅射功率的升高有利于AlN(002)晶面的择优取向生长.氮氩比对AlN薄膜择优取向生长影响较小,N_2≥50%(体积分数)时均可制得高c轴择优取向的AlN薄膜.经优化工艺参数制备的AlN柱状晶薄膜适用于体声波谐振滤波器的制备.     

金属有机化学汽相淀积生长的本征氮化镓中持续光电导和复合机制的研究

通过对室温下的本征氮化镓材料进行不同波长(360nm～377nm)的光照,分析了本征氮化镓中的持续光电导及其复合机制.实验的结果证明了两种持续光电导的特性一种是快速的复合,而且分析表明关灯后这种复合机制导致的持续光电流下降幅度随着波长的增加而增加;另一种是速度较慢的复合,它的电流衰减幅度几乎不受波长的影响.基于这些现象,提出了一个可能的物理模型,认为第一种机制是由于导带电子被电子陷阱俘获而引起的,第二种是由于导带电子与空穴陷阱俘获的空穴之间的复合而造成的.     

金属有机化学汽相淀积生长的本征氮化镓中持续光电导和复合机制的研究

通过对室温下的本征氮化镓材料进行不同波长(360nm～377nm)的光照,分析了本征氮化镓中的持续光电导及其复合机制.实验的结果证明了两种持续光电导的特性:一种是快速的复合,而且分析表明关灯后这种复合机制导致的持续光电流下降幅度随着波长的增加而增加;另一种是速度较慢的复合,它的电流衰减幅度几乎不受波长的影响.基于这些现象,提出了一个可能的物理模型,认为第一种机制是由于导带电子被电子陷阱俘获而引起的,第二种是由于导带电子与空穴陷阱俘获的空穴之间的复合而造成的.     

Synthesis of N-deficient GaN and its enhanced dielectric responses

The GaN powders were synthesized by the reaction of Ga₂O₃ and Li₃N and scanning transmission electron microscopy (STEM) analysis showed the as-prepared GaN were N-deficient with the N vacancies reaching as much as 21%. Besides single-phase of the hexagonal GaN, no other phase from impurities can be detected under the high-resolution transmission electron microscopy (HRTEM) observations. The room temperature (RT) frequency spectrums of the relative dielectric constants _r were measured and the N-deficient GaN exhibited at least twofold enhancement than that of GaN nanostructure materials, especially at low frequency range. Because of the great number of N vacancies (V_N), the rotation direction polarization (RDP) contributes mostly for the enhancement of _r in N-deficient GaN.     

A COMPREHENSIVE INVESTIGATION ON A PECULIAR DEFECT IN WURTZITE GaN FILM

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Shape controlled synthesis and growth mechanism of one-dimensional zinc oxide nanomaterials

Some types of ZnO nanostructures with various shape and size, including tetrapod-like ZnO (T-ZnO) nanorods, nanowires and nanonbbons, have been obtained by controlled growth process. The nanostructures of ZnO have been investigated by means of field-emission scanning electron microscope, transmission electron microscopy and high-resolution transmission electron microscopy. The growth mechanisms of various ZnO nanostructures were proposed and discussed.     

Synthesis of (Ti,W, Mo,V)(C,N) nanocomposite powder from novel precursors

(Ti, W, Mo, V)(C, N) nanocomposite powders with globular-like particle of ∼10–100 nm were synthesized by a novel method, namely carbothermal reduction–nitridation (CRN) of complex oxide–carbon mixture, which was made initially from salt solution containing titanium, tungsten, molybdenum, vanadium and carbon elements by air drying and subsequent calcining at 300 °C for 0.5 h. Phase composition of reaction products was discussed by X-ray diffraction (XRD), and microstructure of the calcined powders and final products was studied by scanning electron microscopy (SEM) and transmission electron microscope (TEM), respectively. The results show that the synthesizing temperature of (Ti, W, Mo, V)(C, N) powders was reduced greatly by the novel precursor method. Thus, the preparation of (Ti, 15W, 5Mo, 0.2V)(C, N) is at only 1200 °C for 2 h. The lowering of synthesizing temperature is mainly due to the homogeneous chemical composition of the complex oxide–carbon mixture and its unusual honeycombed structure.