Y. Q. Jia1)
,
J. G. Li1)
,
Y. M. Wang2)
,
L. X. Ding2)
,
X. M . Qin1) and X. D. Sun1)1) School of Materials and Metallurgy
,
Northeastern University
,
Shenyang 110006
,
China2) Department of Materials
,
School of Mechanical Engineering
,
Shenyang University
,
Shenyang 110044
,
China
金属学报(英文版)
Using yttriu m nitrate as the m other salt , synthesis of ultrafine yttria po w der through w et che mical route w as investigated . Choice of precipitant has dra m atic effects on co m position ,particle size distribution and particle m orphology of the precipitates . When a m m onia solutionw as used as the precipitant , the precursor precipitate w as m ainly Y2( O H) 5 14( N O3) 0 86· H2 O with co m paratively large particle size , broad size distribution and co m plex particleshapes . When sodiu m hydroxide solution w as used , roughly spherical α Y( O H)3·3 H2 Opre cipitate w ith sm all particle size and narro w size distribution w as obtained . The transfor m a tion sequence of dry α Y( O H)3 ·3 H2 O gel during calcination w as determ ined to be α Y( O H) 3·3 H2 O→ Y O O H→ Y2 O3 . After calcining at 600 ℃ for 1 hour , both Y2( O H) 5 14( N O3) 0 86· H2 O and α Y( O H) 3·3 H2 O transfor m to well crystallized Y2 O3 pow ders ,w ith particle sizes of 50 ～3000 n m and 20 n m , respectively .
关键词:
KEYW ORDS yttria
,
null
,
null
,
null
高健
,
康健
,
吴学玲
,
徐競
,
李邦梅
,
邱冠周
中国有色金属学报
以分离于江西某铜矿的嗜铁钩端螺旋菌(L. ferriphilum YSK)菌株为研究对象,报道不同Fe2+浓度对 L. ferriphilum生长活性的影响.结果表明,YSK菌株生长最适宜的Fe2+浓度约为0.1 mol/L.当初始Fe2+浓度为0.4 mol/L时,进入对数生长期前很明显需要一个较长的延迟期,表明该Fe2+浓度对细胞的生长产生较强的抑制作用;当初始Fe2+浓度为0.6 mol/L时,YSK菌株的生长完全受到抑制.尽管高浓度的Fe2+抑制细胞的生长,但受到抑制而不生长繁殖的YSK细胞仍然具有氧化Fe2+的能力.
关键词:
L.ferriphilum YSK菌株
,
Fe2+
,
生长活性
Z.Y. Wu
金属学报(英文版)
The Si L2,3 X-ray absorption near-edge structure (XANES) can be used to probe thelocal structure around Si and derive electronic information of the unoccupied s- andd-like partial density of states in nano-size SiO2. We present Si L2,3-edge for threedifferent size silicates acquired by total electron yield (TEY) at the photoemission sta-tion of Beijing Synchrotron Radiation Facility (BSRF). The Si L2,3-edge spectra areinterpreted based on ab initio full multiple-scattering (MS) calculation. The Si L2.3-edge of nano-size materials has XANES similar to that of a-quartz. The similaritiesbetween the Si L2.3-edge shapes attest to a common molecular-orbital picture of theirSi-O bonding and the same coordination state. However, a considerable broadeningof Si L2,3-edge XANES spectra as decrease of particle size is also an indicative ofpolyhedral distortions.
关键词:
multiple scattering calculation
,
null
,
null
,
null
Physical Review B
The composition dependent lattice parameter, phase stability, elastic moduli, and magnetic transition temperature of the Ni(2+x)Mn(1-x)Ga shape-memory alloys are studied by using the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation. The lattice parameter and tetragonal shear modulus of the cubic L(21) austenite phase decreases linearly with increasing concentration x of excess Ni atoms. The heats of formation of both cubic L(21) and tetragonal beta''' phases and their difference increase with x, indicating decreasing stability of the cubic and tetragonal phases and increasing driving force for the L(21) to beta''' martensitic transition. Investigating the electronic density of states, we find that the Ni-induced decreasing phase stability can mainly be ascribed to the weakening of the covalent bonding between minority spin states of Ni and Ga. Using the computed parameters, the composition dependence of the martensitic transition temperature is discussed. The theoretical Curie temperature, estimated from the Heisenberg model in combination with the mean-field approximation, is larger for the beta''' phase than for the L(21) phase. For both phases, the Curie temperature decreases nearly linearly with increasing x.
关键词:
ni-mn-ga;exchange interactions;ferromagnetic metals;phase-transformation;electronic-structure;martensitic phase;potential;model;ni2mnga;approximation;temperatures
Y.M.Hao1) and Y.Gao2) 1)Department of Physics
,
Tianjin Normal University
,
Tianjin 300074
,
China 2)Library
,
Tianjin Normal University
,
Tianjin 300074
,
China
金属学报(英文版)
tructuraland magnetic propertiesof Ho2 AlFe16 x Mnx( x= 0 8) compoundshave been in vestigated by means of x ray diffraction and magnetization measurements. Thecompoundshave a hexagonal Th2 Ni17 typestructure. With increasing x,the unit cell volumes have a smallincreaseinitially,followed by a greaterlinearincrease. The Curietemperatureandthe saturation magnetization of these compounds show marvelous drop with increasing x. The valuesofJRTofthecompoundsfor x =2 ,3 , and 4 are given.
关键词:
unit cellvolume
,
null
,
null
,
null
齐季
,
谢飞
,
王丹
,
宋志国
,
孙岩
,
肖辉宗
材料保护
目前,有关温度对CO2-3 HCO3-环境下X80管线钢腐蚀行为的影响规律尚无统一的认识.为了探究高强度钢在不同温度的0.5 mol/L Na2CO3+1.0 mol/L NaHCO3溶液中的腐蚀行为,采用动电位极化、电化学阻抗技术,并结合金相显微镜观察研究了温度对X80管线钢在0.5 mol/L Na2CO3+1.0 mol/L NaHCO3溶液中电化学腐蚀行为的影响规律,并通过Mott-Schottky曲线对不同温度下钝化膜的半导体性质进行探讨.结果表明:温度从30℃上升至75℃时,X80钢的点蚀电位和电荷转移电阻均逐渐减小,腐蚀现象越明显;当温度达到90℃时,点蚀电位和电荷转移电阻反而增大,腐蚀程度有所减缓;在0.3～0.7 V内,钝化膜呈现出典型的n型半导体特征;随着温度的升高,钝化膜内的施主电流密度和平带电位呈现先降低后增加的趋势,钝化膜稳定性先减弱后增强;在75～90℃之间存在一个临界温度,此温度下钝化膜的缺陷密度最大,保护性最差.
关键词:
X80管线钢
,
温度
,
腐蚀电化学
,
Mott-Schottky曲线
