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.     

TiAlN/TiN纳米多层膜的微结构与力学性能

采用多靶反应磁控溅射制备了一系列TiAlN层厚固定,TiN层厚在一定范围内连续变化的不同调制结构的TiAlN/TiN纳米多层膜,并使用X射线衍射分析、扫描电子显微镜、纳米压痕仪和CETR-UMT-3型多功能摩擦磨损试验机对多层膜的微观结构和力学性能进行了表征和分析。研究结果表明:TiAlN/TiN纳米多层膜形成了周期性良好的成分调制结构,其中TiN层的插入并没有打断TiAlN层的柱状晶生长。在一定的调制周期下,TiN层和TiAlN层能够形成共格外延生长结构,多层膜呈现硬度异常升高的超硬效应,当TiN层厚约为1.6 nm时多层膜的硬度达到最大值50 GPa,并具有相比于TiAlN单层膜更低的摩擦系数。进一步增加TiN层厚,由于多层膜共格界面结构的破坏,多层膜的硬度随之降低。     

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.     

AlN/SiO2纳米多层膜的超硬效应与高温抗氧化性

采用反应磁控溅射法制备了一系列不同SiO2层厚的AlN/SiO2纳米多层膜,利用X射线衍射仪,高分辨透射电子显微镜、扫描电子显微镜和微力学探针表征了多层膜的微结构和力学性能,研究了多层膜微结构与力学性能随SiO2层厚的变化,考察了AIN/SiO2纳米多层膜的高温抗氧化性.结果表明,受AlN层晶体结构的模板作用,溅射条件下以非晶态存在的SiO2层在厚度<0.6nm时被强制晶化为与AIN相同的六方结构赝晶体,并与AlN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. SiO2随自身层厚的进一步增加又转变为以非晶态生长,致使多层膜的外延生长结构受到破坏,其硬度也随之降低.高温退火研究表明,高硬度的AIN/SiO2纳米多层膜的抗氧化温度为800℃,与AlN单层膜相当. SiO2层的加入尽管能使多层膜获得较高硬度,但是并不能提高其抗氧化温度.     

TiN/NbN纳米多层薄膜的交变应力场和超硬效应

为了研究纳米多层薄膜的超硬效应 ,采用反应溅射法制备从 1 4nm至 2 7nm不同调制周期的一系列TiN/NbN纳米多层膜。高分辨电子显微镜对薄膜的调制结构和界面生长方式的观察发现 ,TiN/NbN膜具有很好的调制结构 ,并呈现以面心立方晶体结构穿过调制界面外延生长的多晶超晶格结构特征。显微硬度测量表明 ,TiN/NbN纳米多层膜存在随调制周期变化的超硬效应。薄膜在调制周期为 8 3nm时达到HK39 0GPa的最高硬度。分析认为 ,两种不同晶格常数的晶体外延生长形成的交变应力场 ,对材料有强化作用 ,这是TiN/NbN纳米多层膜产生超硬效应的主要原因     

TiN／NbN纳米多层薄膜的交变应力场和超硬效应

为了研究纳米多层薄膜的超硬效应，采用反应溅射法制备从1.4nm至27nm不同调制周期的一系列TiN/NbN纳米多层膜。高分辨电子显微镜参薄膜的调制结构和界面生长方式的观察发现，TiN/NbN膜具有很好的调制结构，并呈现以面心立方晶体结构穿过调制界面外延生长的多晶超晶格结构特征。显微硬度测量表明，TiN/NbN纳米多层膜存在随调制周期变化的超硬效应。薄膜在调制周期为8.3nm时达到HK39.0 Gpa的最高硬度。分析认为，两种不同晶格常数的晶体外延生长形成的交变应力场，对材料有强化作用，这是TiN/NbN纳米多层膜产生超硬效应的主要原因。     

SiO2层晶化对TiN/SiO2纳米多层膜结构和性能的影响

采用多靶磁控溅射法制备了一系列具有不同SiO2调制层厚的TiN/SiO2纳米多层膜.利用X射线衍射、X射线能量色散谱、扫描电子显微镜、高分辨电子显微镜和微力学探针表征和研究了多层膜的生长结构和力学性能.结果表明,具有适当厚度(0.45～0.9 nm)的SiO2调制层,在溅射条件下通常为非晶态,在TiN层的模板作用下晶化并与TiN层共格外延生长,形成具有强烈(111)织构的超晶格柱状晶多层膜;与此相应,纳米多层膜产生了硬度和弹性模量异常增高的超硬效应(最高硬度达45 GPa).随着SiO2层厚度的继续增加,SiO2层转变为非晶态,阻断了多层膜的共格外延生长,使纳米多层膜形成非晶SiO2层和纳米晶TiN层的多层结构,多层膜的硬度和弹性模量逐渐下降.     

结构调制超硬Ti/TiN纳米多层膜的制备及其尺寸效应

使用多弧离子镀技术在高速钢基体上制备了调制周期为5~40 nm的Ti/TiN纳米多层膜,用扫描电子显微镜(SEM)、X射线能谱仪(EDS)、X射线衍射仪(XRD)、纳米压痕仪和划痕仪等手段表征薄膜的微观结构和性能,研究了调制周期对Ti/TiN纳米多层膜性能的影响,并讨论了在小调制周期条件下Ti/TiN纳米多层膜的超硬效应和多弧离子镀技术对纳米多层膜硬度的强化作用。结果表明,与单层TiN相比,本文制备的Ti/TiN纳米多层膜分层情况良好,薄膜均匀致密,没有明显的柱状晶结构,TiN以面心立方结构沿(111)方向择优生长。随着调制周期的减小薄膜的硬度呈现先增大后减小的趋势,并在调制周期为7.5 nm时具有最大的硬度42.9 GPa和H/E值。这表明,Ti/TiN在具有最大硬度的同时仍然具有良好的耐磨性和韧性。Ti/TiN纳米多层膜的附着力均比单层TiN薄膜的附着力高,调制周期为7.5 nm时多层膜的附着力为(58±0.9) N。     

Ti3SiC2-64vol%SiC复相陶瓷高温氧化机理研究

采用热等静压原位合成了高致密的Ti₃SiC₂-64vol%SiC复相陶瓷. 通过热重实验研究其在1100~1450℃中空气气氛的高温氧化行为和机理. 研究显示,复相陶瓷的等温动力学曲线遵循抛物线型氧化或抛物线型直线型氧化规律. SiC (64vol%)的引入显著提高了Ti₃SiC₂-SiC材料的抗氧化能力. XRD及SEM-EDS分析显示,氧化膜由外层金红石型TiO₂和非晶态SiO₂组成,过渡层为TiO₂与SiO₂混合物. 高温下（1400℃）,非晶态SiO₂的形成改变了TiO₂膜的生长形态,形成致密TiO₂膜,有效阻碍了氧的扩散. 长时间氧化其抛物线速率常数比在1200℃下氧化低一个数量级. 材料在1400℃下的抗氧化性能明显优于在1200℃下的抗氧化性能.     

α-Ni(OH)2/SiO2核壳以及α-Ni(OH)2空心微球的制备及表征

采用以正硅酸乙酯(TEOS)水解为基础的硅溶胶种子生长法制备了粒径约为270nm的近单分散二氧化硅球型颗粒.采用一种新的溶液生长法,以氢氟酸作为溶液中镍离子配位剂,加入氨水调节溶液pH值的同时作为镍离子补充配位剂,60℃水浴条件下在已制得SiO2微球表面均匀包覆α-Ni(OH)₂得到Ni(OH)₂/SiO₂核壳结构,Ni(OH)₂壳层厚度约为35nm.结合多步包覆法提高Ni(OH)₂壳层厚度,三次包覆后壳层厚度达到约100nm,四次包覆后约为140nm.采用20wt％的强碱NaOH溶液对三次包覆后的Ni(OH)₂/SiO₂核壳结构进行处理,得到了壳层厚度约为95nm的α-Ni(OH)₂空心微球.空心微球具有较大的比表面积为141.06m²/g.     

Coherent growth and superhardness effect of heterostructure h-TiB2/c-VC nanomultilayers

TiB₂/VC nanomultilayers with different VC layer thicknesses have been prepared by a multi-target magnetron sputtering system. X-ray diffraction, high-resolution transmission electron microscopy and nanoindentation measurements were employed to investigate the microstructure and mechanical properties of these films. The results revealed that a metastable structure of VC has been formed in epitaxial TiB₂/VC multilayers with VC layer thickness ≤0.8 nm. Meanwhile, the multilayers exhibited coherent interface between layers resulting in a significantly enhanced hardness of the films, with a maximum value of 43.9 GPa. The stable cubic structure of VC was observed for VC layer thickness ≥1.3 nm, which causes a gradual disruption of the coherent interface of the multilayers, resulting in the quick decrease of hardness.     

Coherent growth and superhardness effect of heterostructure h-TiB2/c-VC nanomultilayers

TiB₂/VC nanomultilayers with different VC layer thicknesses have been prepared by a multi-target magnetron sputtering system. X-ray diffraction, high-resolution transmission electron microscopy and nanoindentation measurements were employed to investigate the microstructure and mechanical properties of these films. The results revealed that a metastable structure of VC has been formed in epitaxial TiB₂/VC multilayers with VC layer thickness ≤0.8 nm. Meanwhile, the multilayers exhibited coherent interface between layers resulting in a significantly enhanced hardness of the films, with a maximum value of 43.9 GPa. The stable cubic structure of VC was observed for VC layer thickness ≥1.3 nm, which causes a gradual disruption of the coherent interface of the multilayers, resulting in the quick decrease of hardness.     

Influence of TiN-nanolayered insertions on microstructure and mechanical properties of TiSiN nanocomposite film

TiN nanolayers with different thicknesses were inserted in TiSiN nanocomposite film by magnetron-sputtering technique. The influences of TiN insertion nanolayers with different thicknesses on microstructure and mechanical properties of TiSiN film were investigated X-ray diffraction, high-resolution transmission electron microscopy, scanning electron microscopy, and nanoindentation techniques. When the TiN insertion layer thickness is <0.5 nm, TiN nanolayers can coordinate the misorientations between TiN nanocrystallites in adjacent TiSiN layers, leading to the transformation from the nanocomposite structure with TiN nanocrystallites encapsulated by SiN _x interfacial phase into columnar crystal structure, and disappearance of the strengthening effect from the nanocomposite structure. When the TiN insertion layer thickness increases to 1.0 nm, the film is strengthened with the epitaxial growth structures between TiSiN and TiN layers. As the TiN insertion layers further thicken, the hardness and elastic modulus evidently decrease, which can be attributed to the breakage of epitaxial growth structures between TiSiN and TiN layers.     

Microstructure and mechanical properties of TiAlN/SiO2 nanomultilayers synthesized by reactive magnetron sputtering

TiAlN/SiO₂ nanomultilayers with different SiO₂ layer thickness were synthesized by reactive magnetron sputtering. The microstructure and mechanical properties were investigated by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and nano-indentation. The results indicated that, under the template effect of B1-NaCl structural TiAlN layers, amorphous SiO₂ was forced to crystallize and grew epitaxially with TiAlN layers when SiO₂ layer thickness was below 0.6 nm, resulting in the enhancement of hardness and elastic modulus. The maximum hardness and elastic modulus could respectively reach 37 GPa and 393 GPa when SiO₂ layer thickness was 0.6 nm. As SiO₂ layer thickness further increased, SiO₂ transformed back into amorphous state and broken the coherent growth of nanomultilayers, leading to the decrease of hardness and elastic modulus.     

Ferroelectric properties of epitaxial Bi3.15Nd0.85Ti3O12 films on SiO2/Si using biaxially oriented MgO as templates

High quality epitaxial Bi_3.15Nd_0.85Ti₃O₁₂ (BNT) thin films with thicknesses from 30 to 80 nm have been integrated on SiO₂/Si substrates. MgO templates deposited by ion-beam-assisted deposition and SrRuO₃ (SRO) buffer layers processed by pulsed laser deposition have been used to initiate the epitaxial growth of BNT films on the amorphous SiO₂/Si substrates. The structural and ferroelectric properties were investigated. Microstructural studies by X-ray diffraction and transmission electron microscopy revealed high quality crystalline with an epitaxial relationship of (001)_BNT||(001)_SRO||(001)_MgO and [100]_BNT||[110]_SRO||[110]_MgO. A ferroelectric hysteresis loop with a remanent polarization of 3.1 μC/cm² has been observed for a 30 nm thick film. The polarization exhibits a fatigue-free characteristic up to 1.44 × 10¹⁰ switching cycles.     

Structural and mechanical properties of titanium and titanium diboride monolayers and Ti/TiB2 multilayers

Nano-multilayers represent a new class of engineering materials that are made up of alternating nanometer scale layers of two different components. In the present work a titanium (Ti) monolayer was combined with titanium diboride (TiB₂) to form a Ti/TiB₂ nano-multilayer. Designed experimental parameters enabled an evaluation of the effects of direct current bias voltage (U_b) and bilayer thickness (Λ) during multilayer deposition on the mechanical properties of reactively sputtered Ti/TiB₂ multilayer films. Their nanostructures and mechanical properties were characterized and analyzed using X-ray photoelectron spectroscopy (XPS), low-angle and high-angle X-ray diffraction (XRD), plan-view and cross-sectional high-resolution transmission electron microscopy (HRTEM), and microindentation measurements. Under the optimal bias voltage of U_b = − 60 V, it was found that Λ (varied from 1.1 to 9.8 nm) was the most important factor which dominated the nanostructure and hardness. The hardness values obtained varied from 12 GPa for Ti and 15 GPa for TiB₂ monolayers, up to 33 GPa for the hardest Ti/TiB₂ multilayer at Λ = 1.9 nm. The observed hardness enhancement correlated to the layer thickness, followed a relation similar to the Hall-Petch strengthening dependence, with a generalized power of ∼ 0.6. In addition, the structural barriers between two materials (hcp Ti/amorphous TiB₂) and stress relaxation at interfaces within multilayer films resulted in a reduction of crack propagation and high-hardness.     

Influence of modulation periods and modulation ratios on the structure and mechanical properties of nanoscale TiAlN/TiB2 multilayers prepared by IBAD

Alternate hard TiAlN/TiB₂ multilayers with different modulation periods (Λ) ranging from 0.6 to 27 nm and modulation ratios (t_TiAlN:t_TiB2) ranging from 8:1 to 25:1 were prepared using an ion beam assisted deposition (IBAD) system. The effect of Λ and t_TiAlN:t_TiB2 on the hardness, elastic modulus, residual stress, and fracture resistance were investigated using various characterization techniques. All multilayers with clear interfaces displayed higher hardness than individual TiAlN and TiB₂ layers. The maximum hardness of 35 GPa and critical load of 84 mN were obtained for the multilayer with a Λ of 2.2-8.8 nm and t_TiAlN:t_TiB2 of 8:1. Strong TiAlN (111) crystallographic texture as well as multilayer structure is thought to be be responsible for the increasing hardness of the TiAlN/TiB₂ multilayers.     

Microstructure and mechanical properties of as-deposited and annealed TiB2/BN superlattice coatings

TiB₂/BN multilayers with the modulation ratios (t_TiB2:t_BN) ranging from 1:1 to 16:1 and a constant modulation period of 24 nm were prepared by magnetron sputtering. The TiB₂/BN multilayers were subsequently annealed in a vacuum environment at temperatures of 500-700 °C for 30 min, then characterized by extensive measurements. All multilayers exhibited small grain sizes and stable layer structures with polycrystalline with TiB₂(001), TiB₂(101), TiB₂(002) textures or amorphous BN, resulting in higher hardness and elastic modulus than that of individual monolithic TiB₂ or BN coatings. The hardness of as-deposited multilayer can reach as high as 39.34 GPa at t_TiB2:t_BN = 13:1, meanwhile the friction coefficient got to 0.028, which was also the lowest. The hardness and friction were almost unchanged after annealing at 500-700 °C, which was attributed to good thermal stability in the layer structure and the existence of stable TiB_xN_y phases.