Ti-N-C-O系的热力学分析与相平衡

本文从热力学的角度分析了TiO2碳热还原反应制备TiC、TiN在不同的PCO、PN2下的最佳温度范围,并绘制了各相稳定存在与PCO、PN2的关系图.     

添加剂对自蔓延高温合成AlN的影响

着重研究了添加剂对自蔓延高温合成ＡｌＮ中的含氧量增加的影响,讨论了ＡｌＮ中的氧量增加的影响,讨论了ＡｌＮ形态与含氧量之间的关系。疏松剂ＮＨ４Ｃｌ虽可使得产物疏松,易于破碎,但它增加了体系中水蒸汽量,促进ＡｌＮ中含量的增加。     

机械力活化合成纳米晶氮化铝研究

通过氧化铝碳热还原反应,用机械力活化法合成了纳米结构的氮化铝,研究了球磨活化对氧化铝碳热还原反应的作用。发现氧化铝经球磨活化后,氮化铝在１０００℃开始生成,碳热还原反应加快,反应激活能由５２９ｋＪ／ｍｏｌ降低到４５７ｋＪ／ｍｏｌ。机械力活化合成的氮化铝晶粒尺寸为２９ｎｍ,粒平均为８μｍ,颗粒尺寸符合对数－正态分布。     

SiO2-AlN-BN复合材料的制备和性能研究

热压烧结制备了ＳｉＯ２－ＡＩＮ－ＢＮ复合材料,研究了ＳｉＯ２－ＡＩＮ－ＢＮ复合材料的力学性能、介电性能和热学性能。结果说明：第二相颗凿攻第三相颗粒ＢＮ的引入对ＳｉＯ２－ＡＩＮ－ＢＮ复合材料的力学性能有显著的补强增韧作用。同时ＳＯ２－ＡＩＮ－ＢＮ复合材料也展现了优秀的介电性能和热学性能而有望成为一新型介电复合材料。     

Deposition of carbon nitride films by filtered cathodic vacuum arc combined with radio frequency ion beam source

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.     

Brillouin light scattering from surface phonons in hexagonal and cubic boron nitride films

Phase velocities of surface acoustic waves in several boron nitride films were investigated by Brillouin light scattering. In the case of films with a predominantly hexagonal crystal structure, grown under conditions close to the nucleation threshold of cubic BN, four independent elastic constants have been determined from the dispersion of the Rayleigh and the first Sezawa mode. The large elastic anisotropy of up to c₁₁/c₃₃=0.1 is attributed to a pronounced texture with the c-axes of the crystallites parallel to the film plane. In the case of cubic BN films, the dispersion of the Rayleigh wave provides evidence for the existence of a more compliant layer at the substrate-film interface. The observed broadening of the Rayleigh mode is identified to be caused by the film morphology.     

Si_3N_4在BaTiO_3基低阻高性能PTCR陶瓷材料中的作用

要同时保证 PTCR材料和元件具有低室温电阻率和较高的 PTC特性 ,有较大难度。研究了添加 Si3N4作为烧结助剂 ,对 PTCR材料的显微结构和电学性能的影响。同添加 Si O2 作为烧结助剂相比 ,添加 1.0 %的 Si3N4的 PTCR材料更易同时满足低阻高性能要求。     

Preparation and properties of TiN and AlN films from alkoxide solution by thermal plasma CVD method

Single phase TiN and AlN films were prepared on a Si wafer from titanium tetra-etoxide and aluminum tri-butoxide solutions dissolved in ethanol and toluene, respectively, using an Ar/N₂/H₂ radio-frequency (r.f.) inductive thermal plasma chemical vapor deposition (CVD) method. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, measurement of electrical resistivity and Vickers microhardness. Factors affecting the formation of the films (lattice parameter, chemical composition, oxygen/carbon content, and deposition rate of the films) were examined in terms of the N₂ flow rate (2.5–4.5 slm), substrate temperature (300–700°C), feed rate of the solution (0.025–0.3 ml/min), and the mole ratio of the alkoxide solution (1:1–1:3). The optimum conditions for preparation of TiN films produced a film 0.2–3 μm thick with an oxygen content of 8 at.% and a free carbon content of 4 at.%, showing an electrical resistivity of 370 μΩ cm. The optimum conditions for AlN films produced a film 0.3 μm thick containing 14 at.% oxygen and 8 wt.% carbon. The deposition rate of the TiN film was determined to be 30–35 nm/min. The Vickers microhardness of the TiN and AlN films was found to be 10±1 and 13±3 GPa, respectively.     

Preparation of (Ti1−xAlx)N films from mixed alkoxide solutions by plasma CVD

(Ti_1−xAl_x)N films were prepared on a Si wafer at 700°C from toluene solution of alkoxides (titanium tetraetoxide and aluminum tri-butoxide) in an Ar/N₂/H₂ plasma by the thermal plasma chemical vapor deposition (CVD) method. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, electrical resistivity, and Vickers micro-hardness. Single phase TiN formed at an Al atomic fraction of 0–0.2, with a mixed TiN and AlN phase occurring up to 0.6 and single phase AlN forming above 0.8. The films had relatively sooth surfaces, 0.4 μm thick at an Al atomic fraction of 0.2, and thickened with increasing Al fraction. The atomic concentration of Ti, Al, N, O, and C determined from their respective XPS areas showed that the Ti and Al contents of the films changes with the solution composition in a complementary way. The impurities were about 10 at.% oxygen and carbon. The electrical resistivity was almost unchanged from the value of 10³ μΩ cm at 0–0.6 Al but then suddenly increased to 10⁴ μΩ cm at higher Al contents. The hardness showed a synergic maximum of about 20 GPa at an Al fraction of 0.6–0.8.     

Titanium–aluminum–nitride coatings for satellite temperature control

Intense solar irradiation, radiative cooling to outer space, and internal heat generation determine the equilibrium temperature of a spacecraft. The balance between the solar absorption and thermal emittance of the surface is therefore crucial, in particular for autonomous parts directly exposed to the solar radiation and thermally insulated from the main thermal mass of the spacecraft. The material composition but also the coating thickness are found to influence the equilibrium temperature of an object in space. In this paper we report on a systematic search for a suitable composition and thickness of Ti_xAl_yN_z alloy coatings prepared by reactive, unbalanced magnetron sputtering from targets consisting of differently sized titanium and aluminum sectors. The films were deposited on glass, glassy carbon, aluminum sheet metal, and on sputtered aluminum and Ti_xAl_(1−x) films on glass. The stoichiometry and sheet resistance of the films was determined with Rutherford backscattering and four-point probe measurements respectively. Reflectance spectra for the visible and infrared spectral ranges were used to obtain average solar absorptance and thermal emittance values used in model calculations of the equilibrium temperature. Neglecting internal heat contributions, the lowest calculated equilibrium temperature in orbit around the Earth, 32.5°C, was obtained for a 505-nm-thick Ti_0.14Al_0.47N_0.40-film.