X.L.Zhao1)
,
T.L.Guo2)
,
M.Ohkohchi3)
,
T.Okazaki3)
,
S.Iijima and Y.Ando3) 1) Japan Science and Technology Corporation
,
Department of Physics
,
Meijo University
,
Shiogamaguchi1 501
,
Tempaku ku
,
Nagoya 468 8502
,
Japan 2) Scientific Research Department
,
Shenyang University
,
Wanghuanan Street21
,
Dadong District
,
Shenyang 110044
,
China 3) Department of Physics
,
Meijo University
,
Shiogamaguchi 1 501
,
Tempaku ku
,
Nagoya 468 8502
,
Japan$
金属学报(英文版)
Multiwalled carbon nanotubes ( MWNTs) were prepared by DCarc dischargein hydrogen gas, and werethermally purified byinfrared radiation in air. The morphology of pristineand purified MWNTs was observed by scanning electron microscope ( SEM) , and the crys tallinestructureand perfection wereinvestigated by high resolution transmission electron mi croscope( HRTEM) and Raman spectrometer. Itcameto the conclusion thatthese MWNTs possessed a high degreeof graphitization and very narrow centralchannel(about1 0 nm indiameter) , giving risetotheappearanceof breathing modesfor MWNTs.
关键词:
multiwalled carbon nanotubes
,
null
,
null
,
null
,
null
Transactions of Nonferrous Metals Society of China
Pitting corrosion behavior of Al2024-T3 in sodium chloride solution was investigated by using potentiodynamic scanning (PDS) measurements and electrochemical impedance spectroscopy (EIS) technique. When pitting corrosion Of the alloy occurs, there exists a passive region in the anodic branch of PDS polarization curve, which is enlarged with the increasing of immersion time due to the competition of the halide ions with OH- ions to adsorb on the oxide film to form the corrosion products film and the increase of pitting corrosion area. Two capacitive semicircles were observed in complex plane plot. For more extensive pitting and general corrosion of Al2024-T3, the passive region in PDS disappeared, while another depressed semicircle was observed in Nyquist plot because of the formation of corrosion products film. On the other hand, the low frequency inductive loop, which had often been regarded as a manifestation of pitting or formation and precipitation of a salt film, was not observed, which indicates that the low frequency inductive loop can not be the characteristic of pitting corrosion or the formation of salt film. The results also show that higher reactant CPE exponent values will correspond to more extensive transformation of a metal surface by very localized corrosion, while general corrosion can result in a smaller CPE exponent value.
关键词:
Al2024-T3;pitting corrosion;electrochemical impedance spectroscopy;potentiodynamic scanning;electrochemical impedance spectroscopy;localized corrosion;al;inhibition;behavior
Journal of Crystal Growth
Single crystals of quasi-one-dimensional charge-density-wave conductor blue bronze Tl(0.3)MoO(3) have been grown by electrolytic reduction method using the raw materials Tl(2)CO(3)-MoO(3) with composition around 1:4.3 mol ration. The electrolytic temperature was about 570 degrees C, and electrolytic current was 25 mA during the electrolytic process. By this method, the Tl(0.3)MoO(3) single crystals obtained have a relatively large average size and high quality. Platelet crystals with typical dimensions of 7 x 2 x 1 mm(3) were obtained. The crystal structure is monoclinic with space group C2/m. The parameters of the unit cell of the single crystal are as follows: a = 18.486(6)angstrom, b = 7.555(2)angstrom, c = 10.032(3)angstrom and beta = 118.38(3)degrees. The C-center symmetry of Tl(0.3)MoO(3) crystal is demonstrated by the selected area electron diffraction (SAED) patterns in the transmission electron microscope (TEM). The full-width at half-maximum (FWHM) of the rocking curve of the (201) Bragg peak of the Tl(0.3)MoO(3) was approximately 0.4 degrees. These are evidences that the single crystal is of high quality. The temperature dependence of the resistivity shows that a metal-semiconductor transition occurs near 181 K. (c) 2005 Elsevier B.V. All rights reserved.
关键词:
electrolytic reduction;single crystal growth;thallium blue bronze;Tl(0).(3)MoO(3);charge density wave;charge-density-wave;molybdenum oxide bronzes;blue bronze;nonlinear;transport;k0.3moo3;k0.30moo3;memory;dynamics;lithium;noise
李久青
,
田虹
,
卢翠英
腐蚀学报（英文）
采用正交实验方法得出了最佳成膜工艺T3/T7,利用线性极化、极化曲线测试、中性盐雾实验等对该工艺形成的膜层耐蚀性进行了研究,并对表面膜层的性能进行了一系列测试.结果表明:在NaCl水溶液中的全面腐蚀速度可降低10～20倍,可通过504h的中性盐雾试验;经该工艺处理后铝合金腐蚀的阴阳极过程都受到明显阻滞,且自然腐蚀电位负移,点蚀电位相对于自然腐蚀电位明显正移,T3/T7处理明显的改善了铝合金在氯化物介质中的耐点蚀性能
关键词:
铝合金
,
surface treatment
,
rare earth conversion film
,
corrosion resistance
Communications in Theoretical Physics
Under various uniaxial stresses, both strains with low symmetry and isotropic strains of crystals take place. The former gives the strain-induced low-symmetry crystal fields and accordingly splittings of levels; the latter gives the isotropic parts of strain-induced crystal fields and accordingly shifts of levels. By using the wavefunctions obtained from the diagonalization of the complete d(3) energy matrix in a regular octahedral field, the relevant matrix elements and accordingly strain-induced splittings and/or shifts of t(2)(3) E-2 and t(2)(3) (4)A(2) for MgO:Cr3+ have been calculated. Their physical origins have been thoroughly analyzed and revealed. It is the admixtures of basic wavefunctions resulted from the spinorbit interaction and/or Coulomb interaction and/or Kramers degeneracy that make strain-induced splittings of levels nonzero. In contrast with this, strain-induced shifts come mainly from the zero-order approximate wavefunctions. It is found that there are nonvanishing matrix elements of operators T(2)xi, T(2)eta and T(2)zeta between wavefunctions with positive M-s and those with negative M-s', which have important effects on strain-induced splittings of levels. The shifts of t(2)(32)E under both hydrostatic pressure and uniaxial pressure have been uniformly calculated. The important results of Y-c, Z(c), P-c, Q(c) and <t(2)parallel toC(A(1))parallel tot(2)> have been evaluated.
关键词:
strain and stress;splitting and shift of levels;ligand field;admixture of wavefunctions;single-electron reduced matrix elements;pressure-induced shifts;thermal shifts;sharp lines;ruby;transitions;broadenings;corundum;spectra
李棠陶俊林王清远
材料研究学报
通过2024--T3和新型2524--T34铝合金的疲劳实验和对试样表面及疲劳断口的观测, 研究了材料的微观结构和疲劳裂纹萌生机制。实验在室温下完成, 应力比为0.1、加载频率为15 Hz。结果表明: 实验材料呈现了再结晶的层状晶粒结构, 晶粒沿着轧制方向被拉长, 并较为平坦。2024铝合金中二相粒子的分布更为密集无序, 且粗大、不规则形状的二相粒子分布更多, 而2524铝合金中二相粒子多沿轧制方向呈带状分布。2524铝合金中的多数裂纹萌生于材料中含Fe的粗大的$\beta$相粒子, 并伴有少量的滑移带裂纹形核和材料缺陷裂纹形核等; 包铝层的滑移带形成的挤入挤出为2024和2524包铝合金的裂纹多处形核提供了主要位置。
关键词:
材料科学基础学科
,
aluminum alloy
,
the second–phase particle
,
fatigue crack
,
fatigue crack initiation
李棠
,
陶俊林
,
王清远
材料研究学报
通过2024-T3和新型2524-T34铝合金的疲劳实验和对试样表面及疲劳断口的观测,研究了材料的微观结构和疲劳裂纹萌生机制.实验在室温下完成,应力比为0.1、加载频率为15 Hz.结果表明:实验材料呈现了再结晶的层状晶粒结构,晶粒沿着轧制方向被拉长,并较为平坦.2024铝合金中二相粒子的分布更为密集无序,且粗大、不规则形状的二相粒子分布更多,而2524铝合金中二相粒子多沿轧制方向呈带状分布.2524铝合金中的多数裂纹萌生于材料中含Fe的粗大的β相粒子,并伴有少量的滑移带裂纹形核和材料缺陷裂纹形核等;包铝层的滑移带形成的挤入挤出为2024和2524包铝合金的裂纹多处形核提供了主要位置.
关键词:
材料科学基础学科
,
铝合金
,
二相粒子
,
疲劳裂纹
,
裂纹萌生
Corrosion
New golden. yellow-colored cerium chemical conversion coatings on aluminum alloy 2024-T3 (AA2024-T3 [UN A92024]) surface at room temperature were obtained by immersing the alloy into a cerium solution containing zinc chloride (ZnCl2) and hydrogen peroxide (H2O2). Electrochemical methods and immersion tests were used to study the dynamics of the coatings formation and their corrosion resistance in 3.5% sodium chloride (NaCl) solution. The morphologies of the coatings were recorded by scanning electronic microscopy (SEM). Energy-dispersive x-ray (EDX) analysis and x-ray photoelectron spectroscopy (XPS) were used to analyze the chemical composition and the oxidation state of the elements in the coatings. Polarization experiments and immersion tests in 3.5% NaCl solution showed that the sensitivity to pitting corrosion for the conversion-coated AA2024-T3 was greatly lower than that of the untreated specimens, and the corrosion resistance improved markedly. SEM photographs showed that the coatings consisted of a lot of spherical particles. EDX and XPS experimental results showed that the coatings were made up of oxygen, cerium, and aluminum, and the spherical particles contained higher contents of cerium and oxygen than the other sites. Cerium was mainly in the form of Ce4+. The mechanisms of conversion coatings formation and improvement on corrosion resistance also are discussed.
关键词:
aluminum;cerium;conversion coating;corrosion resistance;electrochemistry;scanning electronic microscopy;x-ray photoelectron;spectrum;x-ray-absorption;al-alloys;edge spectroscopy;pitting corrosion;protection;inhibition;surface;xps
Materials Chemistry and Physics
The corrosion behaviour of the sol-gel coatings doped with cerium chloride or cerium nitrate on 2024-T3 aluminum alloy was investigated by using electrochemical impedance spectroscopy (EIS) and immersion tests. The sol-gel matrix was obtained through hydrolysis, condensation of 3-glycidoxypropyltrimethoxysilane (GPTMS) and tetramethoxysilane (TMOS), using diethylentriamine as curing agent. The results indicated that cerium nitrate with concentration of 1 x 10(-3) mol L(-1) in the silane solution was excellent on self-healing for the sol-gel coating, while cerium chloride had no obvious effect. This result suggested that the introduction of Cl(-) promoted the under-film pitting of 2024-T3 substrate. It was found that Ce(OH)(3) and Ce(OH)(2)(2+) simultaneously existed in the silane solution by X-ray diffraction (XRD) analysis. Ce(OH)(2)(2+) transformed to CeO(2) due to high-temperature curing of sol-gel matrix demonstrated by X-ray photoelectron spectroscopy (XPS) analysis. Therefore, it can be considered that Ce(OH)(3) and CeO(2) played inhibition roles in the corrosion process of the sol-gel coatings. (C) 2010 Elsevier B.V. All rights reserved.
关键词:
Electrochemical impedance spectroscopy;Sol-gel coatings;Corrosion;X-ray photoelectron spectroscopy;self-healing properties;galvanized steel;silane solutions;protection;inhibition;pretreatments;spectroscopy
