P.W.Shum
,
M.Escursell
,
T.H.Wong
,
K.Y.Li
,
Z.F.Zhou
,
Y.G.Shen
金属学报(英文版)
Titanium-aluminium-nitride (Ti1-xAlxN) coatings were deposited by close-field unbalanced magnetron sputtering on M42 steel substrates and WC-6wto inserts at 450℃. The tribological behavior was analyzed by sliding against steel and WC-6wt0o balls, while the turning performance was evaluated by a conventional turning machine at high cutting speeds without using coolants. In the tribological tests, the formation of transfer layer and the variations of hardness of the coatings played an important role for sliding against steel balls. For the coatings sliding against WC-6wto balls, the Ti-Al-N coatings showed a similar friction coefficient, but the TiN coating exhibited a lower value. The difference could be explained by the tri-oxidation wear mechanism. In the turning tests, a superior cutting performance of the coating was found at x=0.45, which endured 38 minutes before the tool flank wear reached the maximum value of 0.3mm, whereas only 20 minutes were endured for the TiN coating. The excellent performance of the coatings in the turning tests could be explained by the enhanced mechanical properties and oxidation/diffusion resistance of the coatings.
关键词:
hardness
,
null
,
null
,
null
A.Vyas
,
K.Y.Li
,
Z.F.Zhou
,
Y.G.Shen
金属学报(英文版)
Carbon nitride ( CNx thin films have been deposited onto Si(100) (for structural and mechanical analyses) and M42 high-speed-steel (for tribological measurements) substrates at room temperature by closed-field unbalanced magnetron sputtering. The mechanical and tribological properties of these films were highly dependent on the N/C concentration ratio that was adjusted by the F(N2)/F(Ar) flow-rate ratio at fixed substrate biasing of -60V during deposition. The films were characterized by employing scanning electron microscopy (SEM), atomic force microscopy (AFM), nano-indentation measurements, X-ray photoelectron spectroscopy (XPS), Raman scattering and Fourier transform infrared (FTIR) spectroscopy, pin-on-disc tribometer, scratch tester, and Rockwell-C tester. The results showed that the N content in the films increased with the N2 pressure. However, the maximum N/C ratio obtained was 0.25. The nanohardness was measured to be in the range of 11.7-20.8 GPa depending on the N/C ratios. The XPS N 1s spectra showed the existence of both N-C sp^2 and N-C sp^3 bonds in films. Raman and FTIR spectra exhibited that N-C bonds were fewer when compared to other N-C bonds. The friction coefficient of the film deposited onto steel substrate with N/C=0.26 was measured to be -0.08 and for film with N/C=0.22 a high critical load of 70N was obtained. The tribological data also showed that the wear rates of these films were in the range of -10^-16m^3/Nm, indicating excellent wear resistance for CNx films.
关键词:
carbon nitride
,
null
,
null
High Temperature Materials and Processes
In order to decrease the solubility of NiO cathode of molten carbonate fuel cell (MCFC) and develop materials and coatings for separators in the cathode side of MCFC, dysprosium was introduced to modify nickel. In present paper, binary Ni-Dy alloys containing 1, 3 and 5 mass%Dy respectively were prepared. The alloys are two-phase composed of a nickel solid solution and an intermetallic phase Ni17Dy2. The oxidation behavior of the alloys at 923-1023K in air was evaluated by thermogravimetric tests coupled with some physical analysis techniques. The samples pre-oxidized at 923K for 100h were then immersed in molten (0.62Li,0.38K)(2)CO3 at 923K to examine the effect of Dy on the lithiation of NiO in the melt. The results indicated that the addition of dysprosium to nickel increased its oxidation rate, except for Ni-1Dy at 1023K. The scales formed on the alloys were composed of NiO with a trace of DY2O3. The lithiation of NiO in molten (Li,K)(2)CO3 could be favored by the addition of dysprosium. For comparison, binary Ni-Y alloys were also examined. The effect of yttrium on the air oxidation and molten (Li,K)(2)CO3 corrosion of nickel was similar to dysprosium, except that the Y-containing precipitates in Ni-Y alloys underwent very fast preferential corrosion while the Dy-containing intermetallic phases in Ni-Dy alloys not.
关键词:
molten carbonate fuel cell;Ni-Dy alloys;oxidation;molten carbonates;lithiation;fe-20cr alloys;behavior;600-800-degrees-c;coatings
Journal of Physics-Condensed Matter
Based on ab initio total energy calculations, Li, Na and Ag interstitials are found to be stable with at least a 1.56 eV energy barrier to transform to a zinc substitutional site in ZnO, whereas K interstitial has a relatively small energy barrier at 0.79 eV. The isolated dopant substitutional defects (LiZn, NaZn, KZn and AgZn) are found to be rather stable, with at least a 3.4 eV energy barrier to transform to an interstitial site. All of the dopant interstitials (Lii, Nai, Ki and Agi) are fast diffusers. The diffusion of Li interstitial is isotropic, whereas the diffusion of Na, K and Ag interstitials is highly anisotropic. Fundamental processes of the vacancy-assisted mechanisms are systematically investigated and specific values of the energy barriers are obtained.
关键词:
augmented-wave method
冯剑
,
黄金亮
,
贾玉鑫
稀土
为了提高Mg-8Li-3Gd-3Y-0.6Al合金铸锭的力学性能,对合金进行了均匀化退火处理.通过金相显微镜、扫描电镜、显微硬度测试、X射线衍射、拉伸力学性能测试等手段,研究了均匀化条件对Mg-8Li-3Gd-3Y-0.6Al合金的显微组织和力学性能的影响.结果表明,铸态合金经773K 8h的均匀化处理后,铸态时的网状相完全溶解到基体中,第二相弥散分布在基体中,同时退火态合金的抗拉强度达到了154 MPa,比铸态合金提高了23％.合金最佳的均匀化退火工艺是773K 8h,此时该合金具有较好的综合力学性能.
关键词:
Mg-8Li-3Gd-3Y-0.6Al合金
,
显微组织
,
均匀化
,
力学性能
High Temperature Materials and Processes
The ternary carbonate eutectic mixture of Li(2)CO(3), K(2)CO(3) and Na(2)CO(3) as a heat transfer and storage medium has excellent thermophysical properties, but with high viscidity as compared with some other inorganic salts such as chlorides and nitrates. The addition of chlorides or fluorides to molten carbonates may improve their fluidity, but possibly making the melt become more corrosive. In this study, the corrosion behavior of type 304, 310 and 316 stainless steels in an eutectic (Li,Na,K)(2)CO(3) melt with and without an eutectic mixture of NaCl and KCl at 973K in air have been examined. The experimental results indicated that 310 steel shows a much better corrosion resistance in molten carbonates than both 304 and 316 steels, due to the formation of a continuous LiCrO(2) scale. The addition of chlorides to carbonates melt accelerated the corrosion of the steels, especially 310 steel, producing scales with more porosity.
关键词:
Stainless steels;(Li,Na,K)(2)CO(3);(Na,K)Cl;molten salts corrosion;latent-heat-storage;potassium carbonates;lithium;sodium
刘颖
腐蚀与防护
为了探讨在熔融碳酸盐中加入氯化物对不锈钢的腐蚀作用的影响,采用浸泡方法研究了304和310不锈钢在添加了氯化物的700℃熔融(Li,Na,K)2CO3中的腐蚀行为.结果表明,两种不锈钢都遭受了严重腐蚀,不锈钢的快速腐蚀与循环的氯化-氧化反应有关.
关键词:
不锈钢
,
(Li,Na,K)2CO3-(Na,K)Cl
,
熔盐腐蚀
,
氯化-氧化
胡标
,
尹明
,
王庆平
,
闵凡飞
,
杜勇
兵器材料科学与工程
基于文献报道的实验数据,采用相图计算(CALPHAD:CALculation of PHAse Diagrams)方法对V-M(M=Li,Na,K,Sc,Ag)5个二元系进行相图热力学研究.通过热力学优化计算获得了一套描述液相、(V)、(Li)、(Na)、(K)、(αSc)、(βSc)和(Ag)相的热力学参数.V-Li、V-Na和V-K体系中的气相视为由组元V、Li、Li2、Na、Na2、K和K2混合的理想气体.与实验相图数据对比表明,获得的热力学参数能够准确地描述实验相平衡数据.
关键词:
V-M(M=Li,Na,K,Sc,Ag)
,
CALPHAD方法
,
相图
,
热力学模型
