TiN/Si3N4纳米晶复合膜的微结构和强化机制

采用高分辨透射电子显微镜对高硬度的TiN/Si3N4纳米晶复合膜的观察发现,这类薄膜的微结构与Veprek提出的nc-TiN/a-Si3N4模型有很大不同：复合膜中的TiN晶粒为平均直径约10nm的柱状晶,存在于柱晶之间的Si3N4界面相厚度为0.5～0.7nm,呈现晶体态,并与TiN形成共格界面.进一步采用二维结构的TiN/Si3N4纳米多层膜的模拟研究表明,Si3N4层在厚度约＜0.7nm时因TiN层晶体结构的模板作用而晶化,并与TiN层形成共格外延生长结构,多层膜相应产生硬度升高的超硬效应.由于TiN晶体层模板效应的短程性,Si3N4层随厚度微小增加到1.0nm后即转变为非晶态,其与TiN的共格界面因而遭到破坏,多层膜的硬度也随之迅速降低.基于以上结果,本文对TiN/Si3N4纳米晶复合膜的强化机制提出了一种不同于nc-TiN/a-Si3N4模型的新解释.     

Ti-Al-Si-N涂层界面微结构研究

采用多元等离子体浸没离子注入与沉积装置制备Ti-Al-Si-N涂层,借助X射线衍射仪、X射线光电子能谱、透射电子显微镜、纳米探针和原子力显微镜等系统研究涂层界面微结构与力学性能。研究结果表明:Ti-Al-Si-N涂层具有Si3N4界面相包裹TiAlN纳米晶复合结构,Si元素掺杂诱发涂层发生明显晶粒细化效应。随涂层Si含量增加,TiAlN晶粒尺寸显著降低,界面Si3N4层厚度增加。当Si3N4界面层厚度小于1nm并与TiAlN晶粒共格外延生长时,Ti-Al-Si-N涂层表现超高硬度约40GPa,当Si3N4界面相厚度增至2nm并呈非晶态存在时,涂层硬度降至约29GPa。     

磁控溅射TiN/Si3N4纳米复合膜的制备及其环境摩擦学特性

在高速钢基体上直流磁控溅射制备TiN/Si3N4纳米复合薄膜.用EDS、XRD、SEM、TEM、HRTEM等对薄膜的组织结构和形貌进行了表征.采用划痕仪和球-盘式摩擦仪分别测试了薄膜的结合力和在大气及真空中的摩擦学性能.结果表明,TiN/Si3N4复合薄膜由纳米TiN相镶嵌于非晶态Si3N4基体内构成.薄膜中Si含量的增加可抑制纳米TiN相的长大,降低薄膜摩擦系数,薄膜的摩擦学性能得到改善.溅射气压升高导致薄膜呈柱状结构,结合力下降,摩擦系数和磨损率上升.0.2Pa下制备含12.9at.%Si的TiN/Si3N4复合薄膜在潮湿空气和真空中均具有良好的摩擦学性能.     

TiN/Si3N4纳米多层膜的生长结构与超硬效应

采用磁控溅射方法制备了一系列不同Si3N4和TiN层厚的TiN/Si3N4纳米多层膜,采用X射线衍射、高分辨电子显微分析和微力学探针表征了薄膜的微结构和力学性能,研究了Si3N4和TiN层厚对多层膜生长结构和力学性能的影响.结果表明:当Si3N4层厚小于0.7 nm时,原为非晶的Si3N4在TiN的模板作用下晶化并与之形成共格外延生长的柱状晶,使TiN/Si3N4多层膜产生硬度和弹性模量异常升高的超硬效应.最高硬度和弹性模量分别为34.0 GPa和353.5 GPa.当其厚度大于1.3 nm时,Si3N4呈现非晶态,阻断了TiN的外延生长,多层膜的力学性能明显降低.此外,TiN层厚的增加也会对TiN/Si3N4多层膜的生长结构和力学性能造成影响,随着TiN层厚的增加,多层膜的硬度和弹性模量缓慢下降.     

Si和C的存在形态对TiSiCN薄膜微观结构与性能的影响

为扩展Ti Al N和Ti CN薄膜的应用,以适应高速切削和绿色干式切削加工技术发展趋势和要求,采用工业化多弧离子镀在工业用钢H13表面制备Ti SiCN硬质薄膜,以改善H13钢的力学和摩擦学性能。借助扫描电子显微镜、X射线衍射仪、X射线光电子能谱仪、维氏显微硬度计、摩擦磨损仪研究了Si和C的存在形态及其对Ti SiCN薄膜的微观形貌、微观结构、硬度和摩擦磨损性能的影响。结果表明:Ti Si CN薄膜组织致密,具有纳米晶Ti(CN)与非晶相(SiC、Si3N4和C);薄膜中C原子固溶于Ti(CN)中,随着C含量的增加,Ti(CN)固溶度增加;部分C以非晶态的形式存在,起到阻碍Ti Si CN纳米晶粒生长作用; Si以非晶SiC和Si3N4相的形式存在,并包裹Ti CN纳米晶,抑制薄膜晶粒的长大;高Si含量Ti Si CN-No.2薄膜和高C含量Ti Si CN-No.3薄膜表现出高硬度和耐磨减摩特性。     

射频磁控溅射法制备TiSiCN纳米复合膜的微观结构和力学性能研究

采用射频磁控溅射工艺在Si基底上制备TiSiCN纳米复合膜,固定靶材中的Ti含量,通过改变Si和C的含量比沉积得到一系列薄膜,采用X射线衍射仪(XRD)、高分辨透射电子显微镜(HRTEM)、X射线光电子能谱(XPS)和纳米压痕仪研究了不同Si/C含量比对TiSiCN纳米复合膜的微观结构和力学性能的影响。结果表明,Si/C含量比对TiSiCN纳米复合膜的微观结构和硬度具有显著影响,当Si/C含量比为Si2C2时制得薄膜的微观结构为晶化的界面相(SiNx+C)与其包裹的TiN纳米晶粒共格外延生长,薄膜硬度达到最高值46GPa。     

评Veprek的nc-TiN/a-Si_3N_4模型和其“超过金刚石硬度”的实验基础

由于报道获得了超过金刚石的硬度,TiN/Si3N4纳米复合薄膜成为十多年来超硬材料和薄膜材料的重要热点。本文从实验基础方面对这类薄膜的Veprek模型和"超高硬度"进行了评述。在微结构方面,Veprek提出的非晶Si3N4包裹TiN纳米晶的结构模型(即nc-TiN/a-Si3N4)缺乏足够的实验依据,直接观察表明:高硬度薄膜中的TiN晶粒并非等轴晶,而是纳米直径的柱状晶。就Si3N4界面相来说也并非以1个单分子层(~0.3 nm)的非晶态存在,而是厚度约3个分子层(~0.7 nm)的晶体态,更重要的是Si3N4界面相与相邻的TiN晶体形成了共格结构。在制备技术方面,十余年来始终没有人在这类材料中重复出Veprek超过金刚石硬度的结果,Veprek不仅将其归咎于缺乏足够高的沉积温度和氮分压,甚至归咎于薄膜中存在不可避免的微量氧,但也缺乏足够的直接证据。在超高硬度的样品方面,Veprek所报道超过金刚石硬度(最高达138.9 GPa)的样品不但未经任何他人检测确认,而且现在这些样品已经不存在了。     

反应溅射HfC/Si3N4纳米多层膜的微结构与力学性能

通过反应磁控溅射制备了一系列不同Si3N4层厚的HfC/Si3N4纳米多层膜,采用X射线光电子能谱、X射线衍射、扫描电子显微镜和微力学探针表征了多层膜的微结构、硬度与弹性模量,研究了Si3N4层厚度变化对纳米多层膜微结构与力学性能的影响。结果表明,溅射的Si3N4粒子不与C2H2气体反应,因NaCl结构HfC晶体调制层的模板效应,溅射态为非晶的Si3N4层在厚度小于约1 nm时被强制晶化,并与HfC晶体层形成共格外延生长结构,多层膜呈现强烈的(111)择优取向柱状晶,其硬度和弹性模量显著上升,最高值分别达到38.2 GPa和343 GPa。进一步增加Si3N4层的厚度后,Si3N4层转变为以非晶态生长,多层膜的共格外延生长结构受到破坏,其硬度和模量也相应降低。     

Si含量对(AlCrTiZrHf)-Six-N高熵薄膜微观结构和力学性能的影响

采用自制的复合靶材,通过直流磁控溅射技术,在单晶Si基片上沉积一系列不同Si含量的(AlCrTiZrHf)-Si_x-N高熵薄膜,并依次采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、高透射电子显微镜(HRTEM)和纳米压痕仪对薄膜进行表征和测试,研究Si含量对其微观结构和力学性能的影响。实验结果显示,(AlCrTiZrHf)N薄膜成柱状晶生长,并具有(111)晶面的择优取向。Si元素的掺入,使得原薄膜的(111)峰消失,(AlCrTiZrHf)-Si_x-N薄膜晶粒得到细化,同时生成网状非晶相,从而形成非晶包裹纳米晶的纳米复合结构。随着Si含量的增加,薄膜力学性能先上升后下降,这种趋势归因于所形成的纳米复合结构,并且当Si含量为8%(体积比)时,薄膜的硬度和弹性模量最高,分别为26.6和250.9 GPa。     

在室温条件下制备高质量纳米结构TiN薄膜研究

在室温条件下,利用磁过滤等离子体在单晶硅和不锈钢表面上制备了性能优异的纳米结构TiN薄膜.运用原子力显微镜和掠角入射X射线衍射仪对其结构与形貌进行了表征,利用纳米压痕仪测量了TiN薄膜的硬度和弹性模量.结果表明:TiN薄膜表面光滑,致密,无柱状晶;TiN晶粒的平均尺寸为50nm,薄膜硬度达50 GPa,是传统CVD和PVD技术沉积氮化钛的两倍多;XRD衍射试验表明,纳米TiN的衍射角都普遍向小角度移动,TiN晶粒沿(111)择优生长.     

Preparation and characterization of LiNiVO4 powder and non-stoichiometric LiNixVyOz films

Inverse spinel type structured oxide, LiNiVO₄, was synthesized by using solid-state method and the crystalline powder was characterized by Rietveld refinement and X-ray photoelectron spectroscopy. Non-stoichiometric lithium nickel vanadate thin films were prepared by physical vapour deposition technique. The amorphous films were characterized by Rutherford back-scattering spectroscopy (RBS), nuclear reaction analysis (NRA), Auger electron spectroscopy (AES), X-ray diffraction (XRD), scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) analytical methods. Films crystal growth at various temperatures was also studied by XRD and SEM. The HRTEM analysis of sputtered film shows nanocrystalline domains of NiO and LiNiVO₄ phases with characteristic lattice parameters of the host compound and the results correlate well with the XRD data. Electrochemical properties of the films were discussed.     

Synthesis and characterization of C3N4 nanowires and pseudocubic C3N4 polycrystalline nanoparticles

C₃N₄ nanowires and pseudocubic C₃N₄ polycrystalline nanoparticles have been synthesized by the reaction between C₃N₃Cl₃ and NaN₃ with Zn powder as catalyst. The process was carried out using a constant-pressure benzene thermal method at 40 MPa and 220 °C. The prepared nanowires have a diameter range of 3-6 nm and length range of 100-200 nm, while the diameters of the nanoparticles range from 10 nm to 40 nm. The as-prepared samples were characterized by X-ray powder diffraction (XRD), Fourier transform spectroscopy (FTIR), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy (XPS).     

Structural and optical properties of pulsed laser deposited V2O5 thin films

Pulsed laser deposited nanocrystalline V₂O₅ thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM) and optical spectroscopy. The films were deposited on amorphous glass substrates, keeping the O₂ partial pressure at 13.33 Pa and the substrate temperature at 220 °C. The characteristics of the films were changed by varying the laser fluence and repetition rate. XRD revealed that films are nanocrystalline with an orthorhombic structure. XPS shows the sub-stoichiometry of the films, that generally relies on the fact that during the formation process of V₂O₅ films, lower valence oxides are also created. From the HRTEM images, we observed the size evolution and distribution characteristics of the clusters in the function of the laser fluence. From the spectral transmittance we determined the absorption edge using the Tauc plot. Calculation of the Bohr radius for V₂O₅ is also reported.     

燃烧合成ZrB2 / Al2O3 复合粉体及其界面分析

采用燃烧还原合成技术, 以还原体系(B₂O₃ + ZrO2 + Al) 为反应体系制备了ZrB₂ / Al₂O₃ 复合粉体。利用X射线衍射(XRD) 、X 射线光电子能谱(XPS) 和透射电镜( TEM、HRTEM) 对复合粉体的物相组成、化学组成及界面结构进行了表征分析。结果表明, 复合粉体中存在Zr 、B、Al 和O 元素且它们分别以ZrB₂ 和Al₂O₃ 为主要存在形式, ZrB₂ 和Al₂O₃ 为复合粉体的主晶相。复合粉体中有少量ZrO2 的存在, 分析认为是合成反应过程中未参加反应的ZrO2 。ZrB₂ 和Al₂O₃ 颗粒间形成了结合良好的界面, 这主要与ZrB₂ 的结晶过程有关。      

Synthesis of GaN nanoparticles from NH4[Ga(OH)2CO3] under a flow of ammonia gas

In this investigation, we report the synthesis of gallium nitride (GaN) nanoparticles from ammonium-carbonato-dihydroxo-gallate (NH₄[Ga(OH)₂CO₃]) in the flow of NH₃ gas in a temperature range of 500-900 °C. The GaN nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR). The FTIR and XPS revealed that the conversion of NH₄[Ga(OH)₂CO₃] to GaN under a flow of ammonia proceeds stepwise via amorphous gallium oxynitrides (GaO_xN_y) intermediates. Nanosized GaN particles with an average diameter of approximately 20-40 nm were obtained. The results obtained demonstrate that the large-quantity nanosized GaN particles can be synthesized from NH₄[Ga(OH)₂CO₃] powders.     

Hydrothermal synthesis and characterization of CePO4/C core-shell nanorods

The CePO₄/C nanocomposite with core-shell nanostructure has been successfully synthesized using glucose and CePO₄ by a facile and simple hydrothermal method at 160 °C for 24 h. The new material consists of a monoclinic CePO₄ core and an amorphous-C shell. The TEM micrograph indicated that the CePO₄/C nanocomposite was core-shell nanorods. The effects of glucose concentration on the C shells and luminescent intensity of CePO₄/C nanocomposite were investigated. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL). This method is simple, low-cost and does not need any surfactant.     

Photochemical synthesis and characterization of Bi2S3 nanofibers

Bismuth sulfide (Bi₂S₃) nanofibers have been successfully prepared by a photochemical method from an aqueous solution of bismuth nitrate (Bi(NO₃)₃) and thioacetamide (TAA) in the presence of complexing agents of nitrilotriacetic acid (NTA) at room temperature. It was found that the irradiation time, the pH of the solution, and the species of complexing agents play important roles in the morphology control of the bismuth sulfate (Bi₂S₃) nanomaterials. The nanofibers were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED), high resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectra (XPS), and UV-Visible absorption spectra (UV-Vis). Probable mechanisms for the photochemical formation of Bi₂S₃ nanofibers in aqueous solutions are proposed. The photochemical method is a convenient approach for controlling the shape for other metal sulfide semiconductor nanocrystals.     

Synthesis, characterization, and hydrophobic properties of Bi2S3 hierarchical nanostructures

Novel Bi₂S₃ hierarchical nanostructures self-assembled by nanorods are successfully synthesized in mild benzyl alcohol system under hydrothermal conditions. The hierarchical nanostructures exhibit a flower-like shape. X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) were used to characterize the as-synthesized samples. Meanwhile, the effect of various experimental parameters including the concentration of reagents and reaction time on final product has been investigated. In our experiment, PVP plays an important role for the formation of the hierarchical nanostructures and the possible mechanism was proposed. In addition, Bi₂S₃ film prepared from the flower-like hierarchical nanostructures exhibits good hydrophobic properties, which may bring nontrivial functionalities and may have some promising applications in the future.     

凝胶注模成型制备纳米复合多孔氮化硅陶瓷

采用凝胶注模成型两步法烧结工艺,利用纳米碳粉增强,成功地制备出了具有高强度、结构比较均匀并有较高气孔率的氮化硅多孔陶瓷。借助X射线衍射(XRD)、扫描电子显微镜(SEM)、X射线能谱(EDS)、Archimedes法和三点弯曲法等方法对多孔氮化硅陶瓷的微观结构和基本力学性能进行了研究。结果表明:在适当工艺条件下可制成平均强度>100 MPa、气孔率>60%的多孔氮化硅陶瓷。SEM照片显示气孔是由长柱状β-Si₃N₄晶搭接而成的,气孔分布均匀。XRD图谱显示有SiC生成。发育良好的柱晶结构、均匀的气孔分布以及反应生成的SiC微晶是获得高性能的主要原因。      

Hydrothermal-reduction synthesis of manganese oxide nanomaterials for electrochemical supercapacitors

In the present work, amorphous manganese oxide nanomaterials have been synthesized by a common hydrothermal method based on the redox reaction between MnO4(-) and Fe(2+) under an acidic condition. The synthesized MnO2 samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and electrochemical studies. XRD results showed that amorphous manganese oxide phase was obtained. XPS quantitative analysis revealed that the atomic ratio of Mn to Fe was 3.5 in the MnO2 samples. TEM images showed the porous structure of the samples. Electrochemical properties of the MnO2 electrodes were studied using cyclic voltammetry and galvanostatic charge-discharge cycling in 1 M Na2SO4 aqueous electrolyte, which showed excellent pseudocapacitance properties. A specific capacitance of 192 Fg(-1) at a current density of 0.5 Ag(-1) was obtained at the potential window from -0.1 to 0.9 V (vs. SCE).