非平衡磁控溅射离子镀Cu-Nb纳米晶薄膜的微观结构及性能

研究了Nb含量对纳米晶Cu-Nb薄膜微观结构和性能的影响。使用非平衡磁控溅射离子镀技术,在具有(100)晶面的单晶Si基体和玻璃基体上制备不同Nb含量的Cu-Nb纳米晶薄膜,研究Nb含量对纳米晶Cu-Nb薄膜微观结构和性能的影响。将样品置于卧式真空退火炉中进行400 ℃退火,用配备了能量色散X射线光谱仪的场发射扫描电镜、原子力显微镜、X射线衍射仪、纳米压痕仪和四探针电阻率测试仪等分析了退火前后薄膜的微观结构、力学性能与电学性能。结果表明,沉积态Cu-Nb薄膜表面由致密的纳米晶组成,表面粗糙度最高仅为8.54 nm,且无明显的孔洞和裂纹等缺陷。随着Nb含量的增加,薄膜的平均晶粒尺寸下降5 nm,薄膜的硬度也因细晶强化而有所增加,在靶电流为1.3 A时达到最大值4.9 GPa。退火态样品在硬度、弹性模量、平均晶粒尺寸和表面粗糙度方面与沉积态薄膜相比有较小的变化,Cu-Nb薄膜表现出优良的热稳定性。Nb的加入可有效细化晶粒,达到细晶强化的效果,同时Cu-Nb不互溶的特性使得纳米晶薄膜在高温下也可保持较好的热稳定性。Nb靶溅射电流为0.5 A 时薄膜综合性能最佳,此时沉积态Cu-Nb薄膜的电阻率最低,为3.798×10^-7 Ω/m,硬度和弹性模量高达4.6 GPa和139.5 GPa,薄膜厚度为1050 nm,粗糙度R_a为4.70 nm。     

类富勒烯/非晶多层碳膜的制备及性能

针对碳基薄膜存在的高应力问题,利用单极脉冲等离子体增强化学气相沉积技术在单晶硅衬底上制备了含氢类富勒烯/非晶层交替构成的类金刚石多层膜。采用高分辨透射电子显微镜和激光拉曼光谱仪分析了多层膜的结构特征;用X射线光电子能谱分析了薄膜的化学键状态;用纳米压痕仪测定了薄膜的硬度和弹性模量;在CSM往复式摩擦磨损试验机上考察了薄膜在大气下的摩擦学性能,同时比较了多层膜与非晶、类富勒烯薄膜的力学性能和摩擦磨损性能。结果表明:多层膜的硬度高于非晶和类富勒烯单层薄膜,达到28.78GPa;在大气环境下与Si3N4球对摩时平均摩擦因数略低于类富勒烯单层膜,耐磨性明显优于单层非晶和类富勒烯薄膜。     

Mechanical and tribological properties of coatings sputtered from SiC target in the presence of CH4 gas

Amorphous hydrogen-free silicon carbide (a-SiC) coatings demonstrate good adhesion to different steel substrates, low intrinsic stress and high hardness however show quite high coefficient of friction in comparison with carbon-based coatings. Some addition of carbon to SiC can promote the decrease of friction coefficient.In the present work the amorphous hydrogenated silicon-carbide (a-SiC:H) films with different C/Si ratio were prepared at room temperature using DC magnetron sputtering in two ways: (i) sputtering of silicon target; (ii) sputtering of SiC target, both in the gas mixture of Ar and CH₄. In the latter case the films contained less hydrogen at the same C/Si ratio. The mechanical and tribological properties of these films were studied to find their optimum combination.The hardness, elastic modulus (nanoindentation), intrinsic stress (Stoney's formula) and coefficient of friction (pin on disc tribometer) were examined in dependence on the technological parameters, film structure and composition (Raman spectra, electron probe microanalysis). An increase of carbon in the films from 50 to 70 at.% resulted in decrease of hardness and friction coefficient. In the first case (i) the hardness decreased from 13 to10 GPa and in the second case (ii) from 23 to 16 GPa. Thus sputtering of SiC target in the gas mixture of Ar and CH₄ allows obtaining at room temperature the films with C/Si > 1 in which relatively high hardness (16-18 GPa) and low friction coefficient (~ 0.15) are combined.     

Effects of laser surface melting on crystallographic texture,microstructure, elastic modulus and hardness of Ti−30Nb−4Sn alloy

The biocompatibility of orthopedic implants is closely related to their elastic modulus and surface properties. The objective of this study was to determine the effects of cold rolling, recrystallization and laser surface melting (LSM) on the microstructure and mechanical properties of a biphase (α″+β) Ti−30Nb−4Sn alloy. X-ray diffraction (XRD) texture analysis of the cold-rolled substrate revealed the [302]_α″//ND texture component, while analysis of the recrystallized substrate showed the [302]_α″//ND and [110]_α″//ND components. The β-phase texture could not be directly measured by XRD, but the presence of the [111]_β//ND texture component was successfully predicted by considering the orientation relationship between the α″ and β phases. Nanoindentation measurements showed that the elastic modulus of the cold-rolled substrate (63 GPa) was lower than that of the recrystallized substrate (74 GPa). Based on the available literature and the results presented here, it is suggested that this difference is caused by the introduction of crystal defects during cold deformation. The combined nanoindentation/EBSD analysis showed that the nanoindentation results are not affected by crystal orientation. LSM of the deformed alloy produced changes in hardness, elastic modulus and crystallographic texture similar to those produced by recrystallization heat treatment, creating a stiffness gradient between surface and substrate.     

纳米晶体Ti表面磁控溅射SiC薄膜的干摩擦学性能

采用室温磁控溅射技术在纳米晶体钛(剧烈塑性变形制备)表面制备出碳化硅(SiC)薄膜,研究SiC薄膜的组织结构、纳米压痕行为和摩擦磨损性能。结果表明:SiC薄膜具有纳米尺度"畴"特征的表面形貌、高含量Si-C键、与基材间具有明显且呈梯度的元素扩散、低的纳米硬度(10.62GPa)、低的弹性模量(83.34GPa)和高的硬模比(0.128)。在1.96N载荷、氮化硅球(半径为2mm)为对摩件、室温空气条件下,其磨损速率为10-5mm3.m-1.N-1级、摩擦系数约为0.162,磨损后薄膜不出现裂纹和剥落。     

Mechanical, tribological and erosion behaviour of super-elastic hard Ti-Si-C coatings prepared by PECVD

Titaniun carbide (TiC) based coatings prepared by low temperature Plasma Enhanced Chemical Vapor Deposition (PECVD) are investigated as attractive candidates for wear resistance, and particularly for protection against solid particle erosion. In the present work, we incorporated silicon (Si) as an alloying element to TiC, to obtain ternary nanostructured Ti-Si-C films. The incorporation of Si in TiC resulted in significant microstructural, mechanical and tribological modifications. By controlling the Si content in the films, we observed a transition between films consisting of fine nano-sized TiC crystallites (nc-TiC) embedded in an amorphous C:H matrix (a-C:H) to a microstructure formed by nc-TiC encapsulated in a-SiC/a-C:H matrix. This allowed one to selectively control the main mechanical characteristics, namely the hardness (H), the Young's modulus (E), and the friction coefficient (μ), in the range of 14-32 GPa, 140-240 GPa, and 0.16-0.6, respectively. For films prepared under optimized conditions, high elastic strain to failure and high resistance to plastic deformation of the Ti-Si-C films, expressed by H/E and H³/E² ratios, resulted in an 8 fold increase of the erosion resistance at an impact angle of 90° compared to a bare steel substrate. Erosion resistance at 30° increased by a factor of 22 compared to bare substrate due to a simultaneous combination of high H and low μ. Taking into consideration the severe erosion test conditions and the Ti-Si-C film thickness of less than 5 μm in this work, further improvement is expected for thicker films.     

GROWTH OF β-SiC BY rf SPUTTERING ON SILICON SUBSTRATES

1. IlltroductiollSili(.oll t.arbide (SiC) llas beell il1vestigated as a nlaterial with great poteIltial il1 high-p()xxer. high teulperature. and high-f1equel1c} devices, sil1ce it has feat[tres of high break-(l()ttll voltage, l1igll satllratioll t.elocit}…     

High-temperature thermal stability of C/C-ZrC-SiC composites via region labeling method

To investigate the thermal stability of ceramic-matrix composites, three kinds of C/C-ZrC-SiC composites with different Zr/Si molar ratios were synthesized by reactive melt infiltration. Employing region labeling method, the high-temperature thermal stability of the composites was systematically studied by changing the temperature and holding time of thermal treatment. Results show that the mass loss rate of low Si composites has a growth trend with increasing temperature, and a crystal transformation from β-SiC to α-SiC occurs in the composites. In the calibrated area, SiC phase experiences Ostwald ripening and volume change with location migration, while ZrC phase experiences a re-sintering process with diffusion. Moreover, it is found that increasing temperature has a more obvious effect on the thermal stability than extending holding time, which is mainly attributed to the faster diffusion rate of atoms.     

脉冲频率对HiPIMS制备TiN薄膜组织和力学性能的影响EI北大核心CSCD

为探究脉冲频率对通过高功率脉冲磁控溅射制备TiN薄膜组织力学性能的影响,选用Ti靶和N2气体,采用反应磁控溅射技术通过改变高功率脉冲磁控溅射(HiPIMS)电源脉冲频率在Si(100)晶片上制备不同种TiN薄膜。利用X射线衍射仪(XRD)、X射线光电子能谱仪和扫描电子显微镜(SEM)对所制薄膜晶体结构和成分、表面和断面形貌进行分析,利用纳米压痕仪对薄膜的硬度和弹性模量进行表征,并计算H/E和H^(3)/E^(2)。结果表明,高离化率Ti离子轰击促使薄膜以低应变能的晶面优先生长,所制TiN薄膜具有(111)晶面择优取向。薄膜平均晶粒尺寸均在10.3 nm以下,随着脉冲频率增大晶粒尺寸增大,结晶度和沉积速率降低,柱状生长明显,致密度下降,影响薄膜力学性能。在9 kHz时,TiN薄膜的晶粒尺寸可达8.9 nm,薄膜组织致密具有最高硬度为30 GPa,弹性模量374 GPa,弹性恢复为62.9%,具有最优的力学性能。     

Si_3N_4/CrN nanostructured multilayers grown by RF reactive magnetron sputtering

1　INTRODUCTIONInrecentyears ,ceramicsuperhardnesscomposi tionally modulatedmultilayerfilmshavebeenactivelyinvestigated[18] .Theresearchresultsshowthatmul tilayerscancombinethepropertiesoftheconstituentmaterialsandhavemoreexcellent propertiesthanthoseofthesingle layerfilm .Alargenumberofin ternalinterfaceswhichare paralleltothesubstratesurfacecanretardcrackpropagationandprovidebar rierstodislocationmovement.Multilayerswithopti mizedinterfaceareasseemtobemostpromisingwithrespecttoanoptimum…     

利用碳等离子体热处理方法在钨金属和单晶硅片表面制备站立式石墨烯

利用等离子体热处理方法,分别在W金属和单晶Si基底表面直接制备了站立式石墨烯。利用X射线衍射仪(XRD)、扫描电镜(SEM)、拉曼光谱(Raman)对获得的样品进行了结构和成分的表征,并用硬度计对样品表面硬度进行了测量。结果表明,在W金属和单晶Si基底表面分别形成了成分为W₂C-WC/石墨烯和SiC/石墨烯的复合层,且均匀的分布在相应的基底上。W₂C-WC/石墨烯复合层制备成功后,金属W的表面硬度为502.95 HV0.01,与纯金属W基底的硬度450.41 HV0.01相比,表面硬度增加52.54 HV0.01,提高了11.6%;SiC/石墨烯复合层制备成功后,SiC/石墨烯表层的硬度为836.76 HV0.025,与单晶Si基底的硬度812.74 HV0.025相比,表面硬度增加24.02 HV0.025,提高了2.95%。     

Characterization studies of pulse magnetron sputtered hard ceramic titanium diboride coatings alloyed with silicon

The composition, structure and mechanical properties of pulsed-DC unbalanced magnetron sputtered Ti–Si–B thin films—hard coatings with the potential for excellent thermal stability and oxidation resistance—are investigated and reported in this paper. Fully dense, hard (19–37 GPa) Ti–Si–B coatings were deposited at substrate bias voltages (V_s) ranging from floating potential to −150 V which resulted in substrate temperatures of ∼90–135 °C. We found that variation of substrate biasing conditions critically affected film composition, structure and resultant mechanical properties. For instance, concentration of Si in films decreased from 18.4 at.% to 3.8 at.% as V_s was increased from floating potential to −150 V; composition profile analysis of the near-surface region of films (0–10 nm) revealed them to be rich in Si with significant differences among specimens produced at different substrate bias conditions. Variation of substrate biasing conditions provided coating structures that ranged from completely amorphous at floating substrate potential to nanocrystalline at V_s = −50 to −100 V and crystalline nanocolumnar at V_s = −150 V. We found that each of the structures obtained exhibited different specific values of hardness and elastic modulus, which is also in a good agreement with results reported for other coatings possessing similar micro- and nano-structures. Film structure was analyzed in detail by conventional and analytical transmission electron microscopy. Coatings that exhibited the highest values of hardness (37 GPa) were found to possess features such as crystalline nanocolumnar grains a few nanometres in diameter and disordered intergranular regions of different chemical composition, thus qualifying as nanocomposite films. Results of this work allowed relationships to be drawn between deposition parameters and Ti–Si–B coating composition, structure and mechanical properties. Qualitatively similar relationships are also expected for other biased plasma-assisted physical vapour deposited transition-metal-based ceramic coatings alloyed with Si (e.g. Ti–Si–N, Cr–Si–N, Cr–Al–Si–N).     

Single-step,rapid low-temperature synthesis of Si quantum dots embedded in an amorphous SiC matrix in high-density reactive plasmas

A simple, effective and innovative approach based on low-pressure, thermally nonequilibrium, high-density inductively coupled plasmas is proposed to rapidly synthesize Si quantum dots (QDs) embedded in an amorphous SiC (a-SiC) matrix at a low substrate temperature and without any commonly used hydrogen dilution. The experimental results clearly demonstrate that uniform crystalline Si QDs with a size of 3–4 nm embedded in the silicon-rich (carbon content up to 10.7at.%) a-SiC matrix can be formed from the reactive mixture of silane and methane gases, with high growth rates of ～1.27–2.34 nm s^?1 and at a low substrate temperature of 200 °C. The achievement of the high-rate growth of Si QDs embedded in the a-SiC without any commonly used hydrogen dilution is discussed based on the unique properties of the inductively coupled plasma-based process. This work is particularly important for the development of the all-Si tandem cell-based third generation photovoltaic solar cells.     

Deposition of diamond/β-SiC nanocomposite films onto a cutting tool material

The motivation behind depositing nanocrystalline diamond/β-SiC composite thin films onto a cutting tool material is not only to obtain films having a whole range of combined properties of the components but also to enhance their fracture toughness without compromising on the hardness aspect. Nanocrystalline diamond composites are expected to behave differently owing to the large volume of grain boundaries. With smooth surface morphology and improved adhesion, diamond/β-SiC nanocomposite film system may not only serve as a separate film system but may also serve as an interlayer for the further deposition of adherent diamond top layers with regard to cutting tool applications. In this paper we report the deposition of nanocrystalline diamond/β-SiC composite thin films onto WC-6 wt.% Co substrates by employing microwave plasma chemical vapor deposition (MWCVD) technique using gas mixtures of H₂ and CH₄ and tetramethylsilane [TMS, Si(CH₃)₄]. Scanning electron microscopy (SEM), glancing angle X-ray diffraction (GIXRD), energy-dispersive X-ray (EDX), micro Raman scattering and Fourier transform infrared (FTIR) spectroscopic analyses have been carried out to characterize the microstructure and composition of the deposited films. The microstructure of the composite films constitutes a phase mixture of nanometer sized diamond and β-SiC grains. By adjusting TMS gas flow during deposition, β-SiC content in the nanocomposite films can be controlled. This aspect was utilized to successfully realize diamond/β-SiC nanocomposite gradient films with diamond top layers on the hard metal substrates in a single process step.     

机械合金化与热压烧结法制备2Si-B-3C-N陶瓷

以Si_3N_4、B4C、C、Si等粉末为原料,采用机械合金化方法制备2Si-B-3C-N粉末,在氮气保护下1900 ℃, 40 Mpa热压烧结30 min获得2Si-B-3C-N陶瓷,研究了块体陶瓷微观组织结构与力学性能.高能球磨粉末在热压烧结后致密度达到了97.9%.热压烧结的2Si-B-3C-N陶瓷中主要含有等轴状的b-SiC和层片状的h-BCN相.BCN晶粒尺寸约为200 nm,SiC晶粒尺寸约为400～500 nm.BCN晶粒主要分布在SiC晶粒周围.2Si-B-3C-N陶瓷的室温抗弯强度、弹性模量、断裂韧性、硬度分别为446.6 Mpa、144.6 Gpa、5.10 Mpa×m~(1/2)和5.53 Gpa.在高温空气状态下,2Si-B-3C-N陶瓷的抗弯强度随温度的升高而降低,1000和1400 ℃下的抗弯强度分别为358.7和202.1 Mpa.     

The Microstructure and Mechanical Properties of SiC Reinforced Magnesium Based Composites by Rheocasting Process

In the present study, rheocasting process was adopted to synthesise AZ91D composites reinforced with silicon carbide (SiC) particulates. Particle-matrix interfacial reaction, distribution of particles, hardness and mechanical properties of as cast and T4 heat-treated alloy-composites were reported. The rheocast composite materials reveal uniform distribution of SiC particulates. The composite materials show an increase in hardness and elastic modulus compared to unreinforced rheocast alloy. Τhe ultimate tensile strength and ductility of composite materials were lower than those of the unreinforced alloy. 15 μm particles-composite shows significantly higher elastic modulus than the 150 μm SiC particles-composite.     

Structure,composition, and physicomechanical characteristics of tantalum diboride films

The effect of a bias potential applied to the substrate on the structure formation, substructural characteristics, and physicomechanical properties of tantalum diboride nanocrystalline films obtained by the method of nonreactive high-frequency magnetron sputtering has been investigated. It has been shown that the sign and magnitude of the bias potential exert a substantial influence on the structure, composition, and physicomechanical properties of arising coatings. Upon the application of a positive bias potential to the substrate, textured films with a columnar structure, whose greatest hardness was ～45 GPa and the elasticity modulus was only moderate, ～350 GPa, have been obtained. Upon the application of a negative bias potential to the substrate, the amorphous cluster films with a hardness of ～11.5 GPa and an elasticity modulus of ～144 GPa were condensed.     

Superhard and tougher SiC/diamond-like-carbon composite films produced by electron beam physical vapour deposition

SiC/diamond-like carbon (DLC) composite films have been produced on metal substrates via electron beam physical vapour deposition process with various substrate temperatures. The films deposited at 700 °C contain a DLC matrix and nanocrystalline 3CSiC. However, the films deposited at 900 °C contain a 3CSiC matrix and DLC plus nanocrystalline diamond. Both nanoindentation and Hysitron testing have shown that the Young’s moduli and hardnesses of the films increased with the substrate temperature. The hardness could reach ～60 GPa in some parts of the films produced at 900 °C. Meanwhile, the fracture toughness, measured using a micro-beam bending technique, reached 9.2 ± 2 MPa^1/2 for such a composite film. Both high hardness and toughness could be explained by the unique microstructure of the composite film.     

Relationship between mechanical properties and chemical groups in a-C:F films prepared by RF unbalanced magnetron sputter deposition

a-C:F films were prepared by RF unbalanced magnetron sputter deposition on Si substrates. The modulus and hardness of the films and their relationship with chemical groups in the films were investigated. The results show that the modulus and hardness of the deposited films are not only determined by the nature of cross-link C-C network, but also affected by the fluorocarbon groups. The C-C network of the films is composed of sp² cluster, thus the modulus and hardness of films are close to those of polycrystalline graphite. Compared with other fluorocarbon groups existing in the films, the effect of -(CF-CF)_n- group on the modulus and hardness of the films is much higher. With increasing of -(CF-CF)_n- group proportion, modulus and hardness of the films linearly decrease.     

Cu clustering and Si partitioning in the early crystallization stage of an Fe73.5Si13.5B9Nb3Cu1 amorphous alloy

Solute clustering and partitioning behavior in the early crystallization stage of an Fe_73.5Si_13.5B₉Nb₃Cu₁ amorphous alloy have been studied by employing a three-dimensional atom probe (3DAP) and a high resolution electron microscope (HREM). Results from the 3DAP have clearly shown that Cu atom clusters are present in the amorphous state after annealing below the crystallization temperature. The density of these clusters is in the order of 10²⁴/m³, which is comparable to that of the α-Fe grains in the optimum nanocrystalline microstructure. In the early stage of primary crystallization, Cu clusters are in direct contact with the α-Fe nanocrystals, suggesting that the α-Fe primary particles are heterogeneously nucleated at the site of Cu clusters. In the early stage of crystallization, the concentration of Si is lower in the primary crystal than in the amorphous matrix phase, unlike in the late stage of the primary crystallization, where Si partitions into the α-Fe phase with a composition of approximately 20 at.%.