共查询到20条相似文献,搜索用时 15 毫秒
1.
Y. H. Cheng B. K. Tay S. P. Lau X. Shi X. L. Qiao Z. H. Sun J. G. Chen Y. P. Wu C. S. Xie 《Diamond and Related Materials》2001,10(12):2137-2144
Carbon nitride films were deposited by filtered cathode vacuum arc combined with radio frequency nitrogen ion beam source. Both visible Raman spectroscopy and UV Raman spectroscopy are used to study the bonding type and the change of bonding structure in carbon nitride films with nitrogen ion energy. Both C–N bonds and CN bonds can be directly observed from the deconvolution results of visible and UV Raman spectra for carbon nitride films. Visible Raman spectroscopy is more sensitive to the disorder and clustering of sp2 carbon. The UV (244 nm) Raman spectra clearly reveal the presence of the sp3 C atoms in carbon nitride films. Nitrogen ion energy is an important factor that affects the structure of carbon nitride films. At low nitrogen ion energy (below 400 eV), the increase of nitrogen ion energy leads to the drastic increase of sp2/sp3 ratio, sp2 cluster size and C---N bonds fraction. At higher nitrogen ion energy, increase leads to the slight increase of CN bonds fraction and sp2 cluster size, slight decrease of C---N bonds fraction and sp2/sp3 ratio. 相似文献
2.
Deposition of carbon nitride films by filtered cathodic vacuum arc combined with radio frequency ion beam source 总被引:2,自引:0,他引:2
Y. H. Cheng B. K. Tay S. P. Lau X. Shi H. C. Chua X. L. Qiao J. G. Chen Y. P. Wu C. S. Xie 《Diamond and Related Materials》2000,9(12):2010-2018
Atomically smooth carbon nitride films were deposited by an off-plane double bend filtered cathodic vacuum arc (FCVA) technique. A radio frequency nitrogen ion source was used to supply active nitrogen species during the deposition of carbon nitride films. The films were characterized by atomic force microscopy (AFM), XPS and Raman spectroscopy. The internal stress was measured by the substrate bending method. The influence of nitrogen ion energy (0–1000 eV) on the composition, structure and properties of the carbon nitride films was studied. The nitrogen ion source greatly improves the incorporation of nitrogen in the films. The ratio of N/C atoms in the films increases to 0.40 with an increase in the ion beam energy to 100 eV. Further increase in the ion beam energy leads to a slight decrease in the N/C ratio. XPS results show that nitrogen atoms in the films are chemically bonded to carbon atoms as C---N, C=N, and CN bonds, but most of nitrogen atoms are bonded to sp2 carbon. The increase in nitrogen ion energy leads to a decrease in the content of nitrogen atoms bonded to sp2 carbon, and an increase in the content of nitrogen atoms bonded to sp3 and sp1 carbon. Raman spectra indicate an increase in the sp2 carbon phase in carbon nitride films with an increase in nitrogen ion energy. The increase in sp2 carbon fraction is attributed to the decrease in internal stress with increasing nitrogen ion energy. 相似文献
3.
S. Orlanducci V. Sessa M. L. Terranova F. Tazzioli C. Vicario I. Boscolo S. Cialdi L. Catani M. Rossi 《Diamond and Related Materials》2003,12(12):2186-2194
The photoemission behaviour of a series of diamond-based polycrystalline films irradiated by the second (2.3 eV), third (3.5 eV) and fourth (4.7 eV) harmonics produced by a Q-switched-mode-locked Nd: Yag laser has been investigated and related to the structural and compositional characteristics of the layers. The materials were polycrystalline undoped diamond films as well as Nd- and N-containing diamond films grown by CVD techniques, diamond-like and amorphous carbon layers. The morphological and structural characteristics of the films were investigated by electron microscopy, Raman spectroscopy and electron diffraction. The analysis of the photoemission curves does not evidence any improvement of the emission efficiency in the case of Nd-containing films nor for the diamond films grown in the presence of N2. The results evidence conversely a strong correlation between the characteristics of the photoemission process at sub-band gap energies and the presence of amorphous sp2-C patches located at the diamond film surfaces. The photoemitting properties of our samples are discussed and rationalized by considering charge emission occurring at the sp2-diamond-vacuum border and the emission process governed by the ratio of amorphous sp2-C to crystalline sp3-C. The rather high values of quantum efficiency measured in the course of the present research at 3.5 and 4.7 eV suggest that a proper distribution of amorphous carbon onto a good quality diamond surface is the key factor for the preparation of efficient and stable photocathode materials. 相似文献
4.
Richard M. Laine†‡§ Florence Babonneau¶ Kay Y. Blowhowiak§ Richard A. Kennish§ Jeffrey A. Rahn‡†† Gregory J. Exarhos‡‡ Kurt Waldner‡ 《Journal of the American Ceramic Society》1995,78(1):137-145
The pyrolytic evolution of poly(N-methylsilazane), –[H2 SiN-Me] x –, from preceramic polymer to ceramic product is followed by heating samples of the partially cross-linked polymer, in 200°C increments, from ambient temperature to 1400°C. The intermediate products are characterized by chemical analysis, diffuse reflectance Fourier transform IR spectroscopy (DRIFTS), Raman spectroscopy, and 29 Si and 13 C magic-angle spinning (MAS) solid-state NMR. Spectro-scopic characterization indicates that the 1400°C pyrolysis products are amorphous silicon nitride mixed with amorphous and graphitic carbon (as determined by Raman spectroscopy), rather than silicon carbide nitride, as expected based on the presence of up to 20 mol% retained carbon. Efforts to crystallize the silicon nitride through heat treatments up to 1400°C do not lead to any crystalline phases, as established by transmission electron microscopy (TEM) and small-area electron diffraction (SAD). It appears that the presence of free carbon, along with the absence of oxygen, strongly inhibits crystallization of amorphous silicon nitride. These results contrast with the isostructural poly-(Si-methylsilazane), –[MeHSiNH] x –, which is reported to form silicon carbide nitride on pyrolysis. 相似文献
5.
Colin A. Wolden R.F. Davis Z. Sitar John T. Prater 《Diamond and Related Materials》1997,6(12):1862-1867
The radial uniformity and scaleable nature of flat flames make them an attractive technique for diamond deposition. Due to the high temperatures involved in combustion synthesis, typically molybdenum and silicon have been used as substrates. Here we report low-temperature diamond deposition on glass substrates. Diamond deposition was achieved on ordinary sodium silicate glass at substrate temperatures of 500°C; however, film delamination occurred during cooling after deposition. Vycor™ and Pyrex™ are two glasses that have thermal expansion coefficients that are similar to diamond. Continuous, optically transparent films were successfully deposited on both glasses. The diamond films have been characterized by scanning electron microscopy, Raman spectroscopy and secondary ion mass spectroscopy (SIMS). The dependence of hydrogen and sp2-bonded carbon incorporation in the films on reactant composition was quantified. These films were optically transparent and showed good adhesion as measured by a simple tape test. 相似文献
6.
Reaction and Formation of Crystalline Silicon Oxynitride in Si–O–N Systems under Solid High Pressure
Ya-Li Li Fen Zheng Yong Liang Xian-Feng Ma Suo-Jing Cui Takamasa Ishigaki 《Journal of the American Ceramic Society》2001,84(4):875-877
Oxidized amorphous Si3 N4 and SiO2 powders were pressed alone or as a mixture under high pressure (1.0–5.0 GPa) at high temperatures (800–1700°C). Formation of crystalline silicon oxynitride (Si2 ON2 ) was observed from amorphous silicon nitride (Si3 N4 ) powders containing 5.8 wt% oxygen at 1.0 GPa and 1400°C. The Si2 ON2 coexisted with β-Si3 N4 with a weight fraction of 40 wt%, suggesting that all oxygen in the powders participated in the reaction to form Si2 ON2 . Pressing a mixture of amorphous Si3 N4 of lower oxygen (1.5 wt%) and SiO2 under 1.0–5.0 GPa between 1000° and 1350°C did not give Si2 ON2 phase, but yielded a mixture of α,β-Si3 N4 , quartz, and coesite (a high-pressure form of SiO2 ). The formation of Si2 ON2 from oxidized amorphous Si3 N4 seemed to be assisted by formation of a Si–O–N melt in the system that was enhanced under the high pressure. 相似文献
7.
The pyrolysis of cross-linked polycarbosilanes, polysilanes and polysilazanes in an ammonia atmosphere to 1473 K yields amorphous, low-carbon silicon nitride powders. The efficacy of carbon removal is independent of the polymer's structure or functionality but is partially dependent on the initial cross-linking temperature. The amorphous silicon nitride powders partially crystallize to α-Si3 N4 by 1773 K. 相似文献
8.
F. Alibart O. Durand Drouhin M. Lejeune M. Benlahsen S.E. Rodil E. Camps 《Diamond and Related Materials》2008,17(6):925-930
The present work provides correlations between the optical, electronical and microstructural properties of amorphous carbon nitride films (a-CNx) deposited by Direct Current (DC) magnetron sputtering technique versus the N2/Ar + N2 ratio. The microstructure of the films was characterized by Raman spectroscopy and optical transmission measurements. The evolution of both the density of states (DOS) located between the bandtail states and the density of states around the Fermi level N(Ef), have been investigated by electrical measurements versus temperature varying the N2/Ar + N2 ratio. The evolution of the microstructure versus N reveals a continuous structural ordering of the sp2 phase, which is confirmed by the optical and the conductivity measurements. The conductivity variation was interpreted within the framework of the band structure model of the π electrons in a disordered carbon with the presence of localized states. 相似文献
9.
Reported here is the continuation of the structure characterization of carbon thin films produced by a pulsed vacuum arc plasma source. Hydrogen free carbon films with thickness up to 3 μm were prepared with average deposition rate of 5 μm/h onto various substrates. It was found that these carbon films are not quite amorphous and can be described by modelling the clustered structure with different sp3/sp2/sp bond ratios depending on deposition conditions. Results of the experimental investigations and numerical modelling of the films structure are presented. 相似文献
10.
Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy was employed to help determine the structure of boron nitride films grown by bias-enhanced chemical vapor deposition in a low-density supersonic arcjet flow. BN films containing 0.90% cubic boron nitride were analyzed by NEXAFS and compared with c-BN and h-BN reference spectra. The mainly cubic films have been shown previously to be nanocrystalline, which leads to the inability to obtain structural information from Raman scattering spectra. However, with NEXAFS, the nanocrystalline nature of the films does not strongly affect the structural interpretation. It is shown that films deposited with a bias of −75 V are primarily sp3 bonded. This high sp3 bonding character agrees with previous measrements based on infraredtransmission and reflectance spectroscopy, as well as X-ray photoelectron spectroscopy. 相似文献
11.
Osamu Funayama Tomohiro Kato Yuji Tashiro Takeshi Isoda 《Journal of the American Ceramic Society》1993,76(3):717-723
A novel polyborosilazane was synthesized by reacting per-hydropolysilazane with trimethyl borate. The chemical structure of this polymer was investigated by the techniques of infrared spectroscopy and nuclear magnetic resonance measurements. Amorphous silicon nitride was obtained by pyrolysis of this polymer in a stream of anhydrous ammonia to 1000°C with high ceramic yield. The pyrolysis product remained amorphous after additional heating to 1700°C under N2 . Crystallization to α-Si3 N4 and β-Si3 N4 proceeded with heat treatment at 1800°C under N2 . These results indicate that polyborosilazane is a good precursor for amorphous silicon nitride based materials. 相似文献
12.
Yoshikazu Nakamura Yoshihisa Watanabe Yoshihito Suefuji Shigekazu Hirayama 《Journal of the American Ceramic Society》1994,77(5):1385-1387
Atomic force microscopy images were made of the surface of CVD hydrogenated amorphous carbon films. The films were deposited from toluene vapor with oxygen additions during deposition, producing very smooth surfaces. Average roughnesses of only 0.5 nm were measured for the films made with oxygen, whereas a surface roughness of 11 nm was obtained for the films deposited without oxygen. The results suggest that sp 2 - and sp 3 -bonded carbons were removed by oxygen rosion for CVD hydrogenated amorphous carbon films deposited in the presence of oxygen. 相似文献
13.
K.M. McNamara K.K. Gleason D.J. Vestyck J.E. Butler 《Diamond and Related Materials》1992,1(12):1145-1155
The quality of chemically vapor deposited diamond films was assessed in terms of sp2/sp3 content as determined by solid-state nuclear magnetic resonance (NMR) and Raman spectroscopy. While the results of the two techniques are in qualitative agreement, only the NMR spectra yield quantitative values for the sp2/sp3 ratio. Only sp3 carbon was observed in the NMR spectra of very high quality hot-filament, microwave plasma, and d.c. arc-jet chemically vapor deposited films. As expected, Raman spectroscopy is extremely sensitive to sp2 bonded carbon, identifying small amounts below the detection limit of the NMR spectrometer. Comparison of the two techniques, however, indicates that Raman spectroscopy may be so sensitive to sp2 bonded carbon that sp3 bonded carbon in films containing as much as 90% sp3 bonded material may remain undetected. NMR linewidths indicate that the sp3 carbon in such material shows more disorder than that found in high-quality polycrystalline films. 相似文献
14.
K.F. McCarty P.B. Mirkarimi D.L. Medlin T.A. Friedmann J.C. Barbour 《Diamond and Related Materials》1996,5(12):1519-1526
The sharp threshold in substrate temperature below which cubic boron nitride (cBN) cannot be formed in energetic film-deposition processes was investigated. We found that cBN could be synthesized below the threshold temperature on top of cBN that had been previously formed above the threshold temperature. That the initial nucleation of cBN is more strongly dependent on temperature than its subsequent growth is suggested. How the structure of the sp2-bonded BN that accompanied cBN growth changed with temperature was also investigated. Lowering the substrate temperature decreased the local ordering within the graphitic planes, and below the threshold temperature the separation of the graphitic planes increased dramatically. How these structural changes may influence the nucleation of cBN is discussed. 相似文献
15.
Crystallization of an amorphous silicon nitride powder produced in a radiofrequency thermal plasma 总被引:1,自引:0,他引:1
Crystallization behavior of an amorphous silicon nitride powder produced in an RF thermal plasma by the vapor-phase reaction of silicon tetrachloride and ammonia has been investigated. Effects of annealing conditions such as temperature and duration of heat treatment on the properties of powders were studied. Changes in the chemical and phase compositions, as well as in the morphology of powders were measured and interpreted. Annealing of the amorphous silicon nitride powder at 1450°C for 120 min resulted in a powder of about 80% crystalline phase content with an /β ratio of about 6.5. © 相似文献
16.
Synthesis and characterization of microporous carbon nitride 总被引:1,自引:0,他引:1
Lin Liu Ding Ma Heng Zheng Xiujie Li Mojie Cheng Xinhe Bao 《Microporous and mesoporous materials》2008,110(2-3):216-222
This research reports the preparation and characterization of amorphous microporous carbon nitride using HZSM-5 zeolite as template, and ethidene diamine and carbon tetrachloride as chemical precursors. Microporous amorphous carbon nitride is generated by removal of HZSM-5 zeolite in the obtained zeolite/carbon nitride composite using hydrofluoric acid after carbonization the precursor inside the channels of zeolite. The microporous carbon nitride was characterized by nitrogen sorption techniques, scanning electron microscopy, elemental analysis, X-ray diffraction, X-ray photoelectron spectroscopy, IR spectroscopy, Ultraviolet–visible spectroscopy, Raman spectroscopy, and thermo-gravimetric analysis. Amorphous microporous carbon nitride with high surface area and narrow pore size distribution is thermal stable under atmosphere conditions up to 700 K. 相似文献
17.
The hot-pressing behavior of two amorphous and three crystalline silicon nitride powders, including both experimental and commercial samples has been investigated in the presence of MgO-Y2O3 sintering aid. The powders were characterized in terms of bulk and surface chemistry, phase composition and morphology. The sintering behavior was assessed on the basis of green and final densities, weight loss on densification and chemical and phase compositions of the dense material. © 相似文献
18.
Daxin Li Zhihua Yang Dechang Jia Xiaoming Duan Yu Zhou Dongli Yu Yongjun Tian Zihuan Wang Yinglong Liu 《Ceramics International》2018,44(4):3614-3624
Three types of SiBCN: carbon-lean, -moderate and -rich powders with the same Si/B/N mole ratio were subjected to high-energy ball milling to yield an amorphous structure. The effects of carbon content on microstructures, solid-state amorphization, surface characteristics and thermal stability of the as-milled powders were studied in detail. Results showed that the increases in carbon content can drive solid-state amorphization accompanied by strain-induced, crystallite refinement-induced and/or chemical composition-induced nucleation of nano-SiC from an amorphous body. The specific surface area increases as carbon content increases. The amorphous networks of Si–C, C–B/C–C, C–N, B–N and C–B–N bonds that compose the amorphous nature, but the species and contents of the chemical bonds are carbon content-dependent. Carbon-moderate powders possess satisfying thermal stability while carbon-rich ones perform the worst. Mechanical alloying derived SiBCN powders have outstanding oxidation resistance below 800 °C; however only carbon-moderate powders show desirable anti-oxidation ability at higher temperatures. Thus, mechanical alloying of SiBCN appears a suitable technique for developing amorphous matrix materials for practical applications. 相似文献
19.
Jie Li G. Y. Yang Jing Zhu L. Q. Zhang W. Y. Yang Z. Q. Sun 《Journal of the American Ceramic Society》2000,83(4):992-994
A MoSi2 /SiCP composite was synthesized by in situ reactive sintering of a mixture of molybdenum, silicon, and carbon powders. Its microstructural features were studied by X-ray energy dispersive spectroscopy (EDS), conventional transmission electron microscopy (CTEM), and high-resolution transmission electron microscopy (HREM). It was determined that the composite was composed of α-MoSi2 and β-SiC. There were no specific orientation relationships between the MoSi2 matrix and SiCP , because the MoSi2 and SiC were formed at 1450°C by the reaction of solid Mo and C and liquid Si. The abrupt change occurring in the microstructure of the composite is explained by the presence of an interface between MoSi2 and SiCP , where no observable SiO2 amorphous layer or particles were found. Microtwins and stacking faults were frequently observed in {111} planes of SiCP . 相似文献
20.
N. Ouahdi S. Guillemet B. Durand R. El Ouatib L. Er Rakho R. Moussa A. Samdi 《Journal of the European Ceramic Society》2008,28(10):1987-1994
Submicronic CoAl2O4 powders were prepared by double decomposition reaction between solid LiAlO2 and molten KCoCl3 at 500 °C for 24 h. The reaction mechanism involves the dissolution of LiAlO2 shifted by the precipitation of CoAl2O4 until complete transformation and the reaction leads to powders with a very homogeneous chemical composition. The powders obtained were mainly characterized by XRD, FTIR, ICP, X.EDS, electron microscopy and diffraction and diffuse reflexion. The blue pigments obtained exhibit a high thermic stability allowing their use for the colouring of ceramic tiles. 相似文献