共查询到20条相似文献,搜索用时 609 毫秒
1.
Abhishek K. Kothari Shihao Hu Zhenhai Xia Erkan Konca Brian W. Sheldon 《Acta Materialia》2012,60(8):3333-3339
Multiwalled-carbon-nanotube (MWCNT)-reinforced silicon nitride coatings were grown to evaluate the toughness contribution of nanotubes in a ceramic coating. An MWCNT array was first grown using catalytic chemical vapor deposition of acetylene on a silicon substrate. This aligned MWCNT preform was then infiltrated with an amorphous silicon nitride matrix by low-pressure chemical vapor deposition of dichlorosilane (DCS) and ammonia (NH3). The fracture toughness of this material was determined by generating cracks using nanoindentation and then employing finite-element analysis to estimate the bridging toughness contribution of the MWCNTs. The MWCNT bridging toughness of the composites is determined to be ~5.6 MPa m1/2, which is seven times higher than that of the matrix. The interfacial frictional stress is also estimated and ranges from 7 to 20 MPa. 相似文献
2.
Rossana GaziaPietro Mandracci Federico MussanoStefano Carossa 《Surface & coatings technology》2011,206(6):1109-1115
Aluminium nitride thin films were deposited on titanium fixtures, while silicon oxide thin films were deposited on titanium fixtures and chromium-cobalt substrates, using the RF magnetron sputtering technique. Each coating showed different corrosion behaviours when electrochemical characterisations were made in a simulated biological environment, i.e. Hank's solution. Although aluminium nitride was more effective in reducing the localised corrosion on titanium implants, silicon oxide showed the best behaviour against general corrosion and results were consistent for the two kinds of substrates. Moreover the application of a SiO2/AlN bilayer onto the Ti fixtures improved the performances of each separate coating. When the coated surfaces were compared to uncoated substrates, there was no statistically significant difference in cell viability in the response of two different human osteoblastic cell lines — Saos-2 and MG-63. Field emission scanning electron microscopy assessed the surface morphology of coated and uncoated samples, whilst Fourier transform infrared spectroscopy was applied to investigate the bonding structure of barrier layers on silicon samples. On the basis of the data obtained, we are of the opinion that the tested materials show some promising characteristics for the fabrication of novel dental implants with reduced ion release properties. 相似文献
3.
Wen-Qi Wang Xiao-Ping Zou Nan-Jia Zhou Guang Zhu Gui-Ying Wang Zhen-Sheng Peng 《稀有金属(英文版)》2013,32(2):186-190
Large-scale vapor-solid synthesis of ultralong silicon nitride (Si3N4) nanowires was achieved by using simple thermal evaporation of mixture powders of active carbon and monoxide silicon. The products were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The results suggest that the silicon nitride nanowires have a smooth surface, with lengths of up to several hundreds of microns and diameters of 100-300 nm. A detailed study of both the chemical and structural composition was performed. Such ultralong silicon nitride nanowires demonstrate potential applications as materials for constructing nanoscale devices and as reinforcement in advanced composites. 相似文献
4.
Advanced structural ceramics, such as silicon nitride-based materials, are of significant interest due to their excellent physical and mechanical properties. However the cost of grinding these ceramics, an integral part of their fabrication, is very high and can result in surface and subsurface damage to the material. These defects can significantly reduce the strength and reliability of the finished component and are sensitive to grinding parameters. In this investigation, the effect of finish electrolytic in-process dressing (ELID) grinding on the flexural strength of silicon nitride specimens were studied. Kyocera's silicon nitride SN 235, in the form of Modulus of Rupture (MOR) specimens, were ground using the application of ELID grinding with a # 6000 grit sized cast iron bonded diamond (CIB-D) grinding wheel. A significant improvement in the strength of the Si3N4 specimens was noted when finish ELID grinding was performed. This was the result of ductile regime grinding using the application of finish ELID grinding. Another method to improve the flexural strength of silicon nitride specimens will also be addressed in this paper. 相似文献
5.
Juergen Lenz Ravi K. Enneti Valmikanathan Onbattuvelli Kunal Kate Renee Martin Sundar Atre 《JOM Journal of the Minerals, Metals and Materials Society》2012,64(3):388-392
Silicon nitride has been the favored material for manufacturing high-efficiency engine components for transportation due to
its high temperature stability, good wear resistance, excellent corrosion resistance, thermal shock resistance, and low density.
The use of silicon nitride in engine components greatly depends on the ability to fabricate near net-shape components economically.
The absence of a material database for design and simulation has further restricted the engineering community in developing
parts from silicon nitride. In this paper, the design and manufacturability of silicon nitride engine rotors for unmanned
aerial vehicles by the injection molding process are discussed. The feedstock material property data obtained from experiments
were used to simulate the flow of the material during injection molding. The areas susceptible to the formation of defects
during the injection molding process of the engine component were identified from the simulations. A test sample was successfully
injection molded using the feedstock and sintered to 99% density without formation of significant observable defects. 相似文献
6.
W. Kulisch C. PopovD. Gilliland G. CecconeJ.P. Reithmaier F. Rossi 《Surface & coatings technology》2011,206(4):667-675
Ultrananocrystalline diamond/amorphous carbon nanocomposite films (UNCD/a-C) have been deposited by microwave plasma chemical vapor deposition from a 17% CH4/N2 mixture. The films consist of diamond nanocrystallites of 3-5 nm embedded in an amorphous carbon matrix of 1-1.5 nm width. In a first series of experiments it is shown that as-grown UNCD/a-C films are hydrogen-terminated, conductive and very stable. Furthermore, by plasma- and photochemical treatments the H-termination can either be improved or replaced by terminating OH or F functionalities, whereas chemical room temperature processes to change the termination failed. A second set of investigations concerns the functionalization of differently terminated UNCD surfaces. Processes are discussed to bind DNA on H-terminated UNCD and to deposit an anti-fouling poly(ethylene glycol) layer on OH-terminated films. A third series of experiments shows that UNCD surfaces are not prone to unspecific interactions with highly-fouling proteins such as bovine serum albumin (BSA) but nevertheless some interaction will take place. However, the amount of adsorption and also the ratio of BSA and fibrinogen adsorption, which is of importance for the hemocompatibility of a surface, can be adjusted by the surface termination. Finally, it will be shown that continuous as-grown UNCD surfaces are bioinert and not cytotoxic for a variety of different cell lines. 相似文献
7.
L. Yu. Ostrovskaya V. G. Ral’chenko I. I. Vlasov A. A. Khomich A. P. Bol’shakov 《Protection of Metals and Physical Chemistry of Surfaces》2013,49(3):325-331
The peculiarities of wettability of diamond that was obtained in a nanostructured form as ultrananocrystalline diamond (UNCD) films by deposition from a gas phase are considered. Surface hydrogenation leads to hydrophobicity: advancing contact angle θ for UNCD films reaches 106 ± 1° (for diamond single crystals θ = 93°). Even higher values of θ equal to 124 ± 3° were detected for nanoporous samples of UNCD, in which a graphite-like component was removed by etching. High hydrophobicity is achieved owing to the specific surface morphology of the nanostructured diamond (anisotropic, with high content of nanopores) and chemical modification, which on the whole provides for very low values of free surface energy of the films. It was shown that laser-drilled microholes in polycrystalline diamond also can enhance the hydrophobicity. The wetting behavior of the nanostructured surfaces agrees well with the Cassie-Baxter equation for heterophase porous surfaces. The oxidation and hydrogenation of UNCD films allows controlling of θ in considerably wider ranges compared to single crystal diamond. 相似文献
8.
综述了以钛或锰金属粉与纳米金刚石、纳米碳化硅、氮化硅晶须或碳纳米管为原料,通过真空镀法对上述纳米粉体进行表面改性处理后在新能源方面的应用。介绍了钛镀覆纳米金刚石、纳米碳化硅和氮化硅晶须作为铂催化剂载体材料在直接甲醇燃料电池方面的应用,以及锰镀覆碳纳米管在超级电容器方面的应用。 相似文献
9.
Cláudio Vasconcelos Rocha Célio Albano da Costa 《Journal of Materials Engineering and Performance》2006,15(5):591-595
In-situ silicon nitride and a whisker-reinforced silicon nitride-silicon nitride composite, densified via gas pressure sintering
and hot pressing, respectively, were evaluated using the single-edge V-notched beam (SEVNB) fracture toughness technique.
The mean value ofK
IC for each material was 5.7 and 7.9 MPa·m1/2, respectively, and the toughness was influenced by the presence of the elongated Si3N4 grains in the microstructure. The notch radius was observed to have the same effect as a sharp crack when notch-root radius
was smaller than 10 μm, which was considered to be a realK
IC for these materials. 相似文献
10.
Jong-Do Kim Su-Jin Lee Seo-Jeong Park Jae-Hoon Lee 《Metals and Materials International》2011,17(3):515-519
Ceramics have attractive properties to metals and polymers, and they are consequently useful for specific applications. Silicon
nitride has been studied extensively and has been found to possess promising thermal and mechanical properties at high temperatures.
However, it has drawbacks such as brittleness and large scatter in its mechanical properties. As a result, it is difficult
to fabricate complex shapes using traditional methods because of high cost and difficulties to machine the components. Today,
ceramic parts have limited use for production of simple shaped parts and low quantities. This study explores the possibility
of employing silicon nitride for more diverse applications using laser-assisted machining (LAM). Because the surface of the
workpiece is locally heated by an intense laser source prior to material removal, softening and damage of the workpiece surface
make machining of ceramics easy. Among the parameters of LAM, laser power is one of the decisive factors during the process.
In this study, fractured cross sections were observed to examine how the microstructure of silicon nitride was changed by
laser power. The deformation of microstructure near the surface of the workpiece increases when the laser power increases.
It is found that increasing the laser power facilitates cutting of silicon nitride but results in detrimental heat effects
on the surface of the workpiece. 相似文献
11.
镁合金磷酸盐 /氮化硅双层复合膜结构及耐蚀性能研究 总被引:1,自引:1,他引:0
目的针对传统镁合金化学转化膜裂纹尺寸大、耐腐蚀性差等问题,制备一种镁合金磷酸盐/氮化硅双层结构的抗腐蚀复合膜。方法先对镁合金进行传统磷酸盐转化处理,再运用等离子体增强化学气相沉积技术沉积氮化硅膜层,分析复合膜的形貌、元素分布、表面电位及极化曲线,并与磷酸盐转化膜进行对比。结果氮化硅膜层能在磷酸盐转化膜裂纹处选择性优先沉积,从而在相当程度上填补转化膜层的裂纹,形成致密的复合膜结构。具有复合膜结构的镁合金表面电位和腐蚀电位明显高于传统磷酸盐转化处理的镁合金。结论镁合金表面制备磷酸盐/氮化硅双层复合膜后,抗腐蚀能力明显高于传统磷酸盐转化处理的镁合金。 相似文献
12.
A.N. Jones W. Ahmed C.A. Rego H. Taylor B.D. Beake M. J. Jackson 《Journal of Materials Engineering and Performance》2007,16(1):131-134
A chemical vapor deposition (CVD) system has been used to produce polycrystalline and nanocrystalline diamond (NCD) films.
For biomedical and electronic engineering applications, it is highly desirable to deposit smooth films with decreased crystal
size. In general, diamond coatings with a crystal size of 10-100 nm range are known as NCD. There are several ways in which
NCD may be deposited including growth from fullerene precursors with argon dilution. Several workers have proposed various
mechanisms for the growth process using inert gas dilution to conventional hot filament (HF) or microwave chemical vapor deposition
(MWCVD) systems, or NCD growth through the deployment of CO2/CO or O2-rich gas environments. However, the use of inert gas dilution, with carbon containing species is the least complex approach
to growing nanocrystalline, and more recently, ultrananocrystaline diamond (UNCD). Mechanical properties of UNCD have been
determined by nanoindentation, and their nanotribological properties have been measured by nano-scratch and nano-impact testing.
The relative importance of toughness (∼E/H ratio) and elastic strain-to-break (∼H/E ratio) of these systems on their behavior
in nano-scratch and nano-impact tests is considered, and strategies for optimizing the deposition conditions for enhanced
durability under different contact conditions are suggested in this short communication. 相似文献
13.
F.-Z. Roki F. Mercier C. Bernard M. Morais A. Claudel Ph. Berne L. Chaffron 《Surface & coatings technology》2010,205(5):1302-1306
The residual porosity of structural silicon carbide (SiC) composites limits their use in advanced nuclear systems. The use of thick coatings of high-Z materials like tungsten (W) or tungsten alloys (W1−xRex) is a promising solution to overcome such problems. However, solid-state reactions occur between SiC and metals at high temperatures. An intermediate layer is therefore selected, based on thermodynamic computation. It is shown that aluminum nitride (AlN) could limit the interface reactivity at temperatures close to 1000 °C. Duplex AlN/W1−xRex coatings were fabricated in two steps by chemical vapor deposition on bulk silicon carbide to verify experimentally the theoretical material solution approach. Electron probe micro-analyses showed that, at the micrometer level, there was no interface reaction during the growth process. It is the first time that such a material stack has been fabricated, and it seems promising for the high-temperature use of SiC with tungsten alloys. 相似文献
14.
Purification of solar cell silicon materials through filtration 总被引:2,自引:0,他引:2
Silicon is the material most commonly used in the manufacturing of photovoltaic (PV) cells. In the current study, laboratory experiments of purification of solar cell silicon materials through filtration are carried out. Inclusion removal from silicon was investigated. The purpose is to achieve clean silicon materials for solar cells. Silicon samples and filter samples were analyzed using microscopeobservation, EPMA, and X-ray detection. Silicon nitride (Si3N4) and silicon carbide (SiC) particles are the main non-metallic inclusions present in top-cut silicon scrap. Almost all inclusions larger than 10 μm can be removed from silicon by the porous foam filter. In mass fraction, more than 90% inclusions areremoved. Si3N4 particles are mainly removed on the top surface of the filter, and SiC particles are mainly removed by entering the pores and attaching tothe filter material. SiC inclusions are not only simply attached on the surfaceof the filter material, but are found also inside the filter material. There are SiC bridges near the filter materials. These bridges may fill the spaces between filter material, and this will further retard inclusions passing through the filter. Three-dimensional turbulent fluid flow and inclusion motion in the filter was calculated. Both experimental observation and fluid flow simulation indicate that most of the inclusions are entrapped at the upper part of the filter. 相似文献
15.
16.
A two-step plasma enhanced chemical vapor deposition procedure has been developed to produce high quality SixNyHz films for quantum cascade laser applications. The procedure consists in exposing the GaAs substrate to a controlled N2 plasma previous to the silicon nitride film deposition. The pre-treatment causes the formation of a thin GaN film that passivates the GaAs wafer. The method has been optimized varying RF power, N2 flow rate and process time of the pre-treatments and monitoring their effects on the resulting chemical composition and dielectric properties of the nitride overlayers, by means of infrared spectroscopy, X-ray photoelectron spectroscopy and electric characterizations. A narrow window in the pre-treatment RF power, N2 flux and time values, improves the composition, structural and dielectric properties of the silicon nitride overlayers. The best result has been found depositing the silicon nitride films on GaAs wafer after 2 min of N2 plasma treatment with a power of 20 W and a 50 cm3/min flow rate. 相似文献
17.
A. Kumar H. L. Chan N. B. Dahotre 《Journal of Materials Engineering and Performance》1997,6(5):583-585
CN
x
/TiN composite coatings were deposited on Si (100) substrates using the pulsed laser deposition (PLD) method. Previous results
showed that a seed of titanium nitride (TiN) layer between silicon substrates and a top layer of carbon nitride increased
the hardness and modulus values of overall composite coatings (Ref 1). This paper describes the same approach to growing carbon
nitride composite coatings with varying thicknesses of different kinds of buffer layers and carbon nitride films on Si (100)
substrates at different temperatures and pressures. Preliminary results showed the presence of carbon nitride films by the
Fourier transform infrared spectroscopy (FTIR) method. The mechanical properties of the films were characterized using the
nanoindentation technique. The crystallographic properties of the films were characterized using the x-ray diffractometer
method. 相似文献
18.
S. M. Aouadi D. M. Schultze S. L. Rohde K. -C. Wong K. A. R. Mitchell 《Surface & coatings technology》2001,140(3):269-277
A series of monolithic and multilayer coatings of chromium nitride with various compositions and architectures were deposited at low temperatures (<200°C) on silicon substrates using ion-assisted reactive magnetron sputtering. All coatings had a total thickness in the 1.5±0.3 μm range. The multilayer coatings were designed such that their period and CrN fraction varied in the range 30–150 nm and 0.50–0.93, respectively. Real-time in situ ellipsometry was used to monitor and control the deposition process. The deposited coatings were characterized post-deposition using X-ray diffraction (XRD), Rutherford backscattering (RBS), X-ray photoelectron spectroscopy (XPS), and spectroscopic ellipsometry (SE). The primary chromium nitride phases (Cr2N and CrN) in the films were identified using XRD. The chemical composition of selected samples was determined from RBS and XPS measurements. The phase composition of the deposited layers was deduced from the analysis of the SE data. The mechanical properties of the coatings were evaluated using a nanoindenter. The measured hardness values were in excess of 20 GPa. The results of the different characterization and testing techniques were correlated and follow-up work on this project suggested. 相似文献
19.
20.
Julin Wan Amiya K. Mukherjee 《JOM Journal of the Minerals, Metals and Materials Society》2003,55(1):28-33
In an investigation of the creep properties of silicon nitride/silicon carbide nanocomposites, the micro-nano type composites
with nano-SiC at intragranular and inter-granular regions show behavior not much different from that of silicon-nitride monolith.
The improvement of creep resistance is modest, up to about one order of magnitude decrease in steady-state creep rate. The
creep rate parameters such as activation energy and stress exponent measured for this type of nanocomposite are within the
range of those of silicon nitride. This evidence suggests that a special strengthening mechanism may not be necessary for
this type of material. Nano-nanocomposites show remarkably lower creep rates, possibly pointing to a new creep mechanism such
as solid-state diffusion.
For more information, contact A.K. Mukherjee, University of California-Davis, Department of Chemical Engineering and Materials
Science, Davis, CA 95616; e-mail akmukherjee@ucdavis.edu. 相似文献