共查询到20条相似文献,搜索用时 15 毫秒
1.
《Synthetic Metals》1998,95(2):135-142
Binary graphite intercalation compounds with sulfuric acid (H2SO4GICs), perchloric acid (HClO4GICs) as well as chromium trioxide (CrO3GICs) are known to be readily de-intercalated due to cathodic reduction and/or washing with aqueous solutions. The subsequent electrochemical intercalation of sulfuric and perchloric acid into the host CrO3GICs has resulted in the ternary CrO3H2SO4GICs and CrO3HClO4GICs, respectively. The products of the subsequent intercalation composed of the bi- and co-intercalation domains appeared to be very resistant to de-intercalation. The comparison of the results of the X-ray microprobe and X-ray diffraction analysis obtained for the original CrO3GICs and the cathodically reduced ternary compounds have allowed insight into the structural and chemical changes developing during the subsequent intercalation/de-intercalation process. The knowledge of these properties is helpful for both the better understanding of the intercalation mechanism of the acids into the host CrO3GIC and the elucidation of the extremely high stability of the ternary compounds. 相似文献
2.
《Synthetic Metals》2001,125(2):141-146
Intercalation reaction of benzene (C6H6) into CsC24 and the characteristics of resulting ternary graphite intercalation compound (GIC) have been investigated, in comparison with the similar CsC24–ternary GICs with ethylene (C2H4) and acrylonitrile (C2H3CN), and the behavior of these organic molecules within the interlayer nanospace has been discussed. The stability of these ternary GICs under exposure in air, in both stage structure and electrical conductivity was found to be in the order of C2H4–, C6H6– and C2H3CN–GICs. This result was reasonably explained as follows: the C2H4 molecules in the interlayer space oligomerize considerably and form network preventing diffusion of the Cs atoms in the interlayer, while the C6H6 molecules form only dimers or trimers and unable to form network, and the C2H3CN molecules, in spite of their strong tendency to polymerize, apparently do not form oligomers in the interlayer space, and its ternary GIC tends to degrade easily. By the electrical and galvanomagnetic measurements, it is revealed that the dominant carrier of these ternary GICs is electrons, even when the electrical conductivity decreases considerably after prolonged exposure in air, while the host graphite, Grafoil, shows two-carrier conduction. This fact indicates that the degradation of the ternary GICs occurs mainly at the periphery or surface layer of the crystallite, and at the inside of the crystallite, the ternary stage structure is retained unchanged. 相似文献
3.
4.
《Corrosion Science》1986,26(1):7-14
Practically all constructional steels are working under applied loads and environments. Below some stress levels the deterioriation of the material occurs by typical corrosion modes. Modern constructions are often loaded with enough high stresses to promote catastrophic failures due to stress corrosion crack propagation. Actually the whole range of metallic materials used in reliable constructions which are exposed to corrosive environments should be tested for their sensitivity to stress corrosion cracking. By measuring the material constant KISCC (critical stress intensity factor for stress corrosion cracking) it is possible to construct the reliable parts working in a safe range of stresses, which cannot be computed knowing yield strength of the material only. For measuring KISCC values of high strength CrMnSiNi and CrMo steels, original stands were built and long-term (> 103h) tests applied by means of the cantilever beam method. Sensitivity of tested steels to stress corrosion cracking was expressed as a ratio KISCC:KIC. Some other observations concerning kinetics of crack propagation and other properties of the materials have been carried out. 相似文献
5.
The high temperature oxidation behaviour of FeCrNi austenitic alloys containing 1% Ti which, in some cases, had been converted into an oxide dispersion has been examined. The oxide dispersions were produced by an internal oxidation treatment using a 50/50 Cr/Cr2O3 powder mixture in a sealed quartz capsule at 1100°C: the samples were not in direct contact with the powders. Generally, the effect of the dispersed oxide was much less pronounced than in corresponding nickel-free, ferritic alloys. Nevertheless, the time-to-breakaway of the protective Cr3O3 scale which developed on Fe18CrNi alloys was substantially increased, although the differences between the untreated and the internally oxidized alloys reduced with increasing nickel content. An Fe14Cr20Ni alloy did not show any improvement after internal oxidation. Unlike the ferritic alloys, no coarsening of the dispersoid phase was observed during exposure. 相似文献
6.
LI Zuoan SONG Qinggong Department of Physical Chemistry University of Science Technology Beijing Beijing China College of Science Civil Aviation University of China Tianjin China 《稀有金属(英文版)》2004,23(2):161-164
Based on cluster variation method (CVM) and natural iteration method (NIM), order-disorde phase transition inthe intercalation compounds M_(1/2)TiS_2 is simulated by computer. The favorble conditions, under which 3a_0~(1/2)×a_0 super-structure is formed, are given, and the results are in good agreement with the experiments and theoretical calculations. Therelationship between critical temperature and M-ion-vacancy interaction parameter is linear. 相似文献
7.
《Corrosion Science》1986,26(2):95-107
Electrochemical studies were conducted to determine the critical amount of oxygen necessary to prevent corrosion by maintaining the open-circuit passivity of Fe18Cr samples initially passivated at 0.6 V(NHE) in 1N H2SO4 solutions. Samples passivated at 0.6 V(NHE) and then released to open circuit in O2-saturated (29.4 ppm O2 dissolved) solution maintained a state of passivity. Samples passivated and released to open circuit in N2-purged solution decayed to a state of active corrosion in 800–2000 min. A passive state, however, could be maintained if O2 were added to the N2 flow so that a minimum of 1.7 ppm O2 was present in solution. Furthermore, this critical amount of O2 had to be added before open-circuit decay reached 0.45 V(NHE). Auger electron spectroscopy measurements indicated that following open-circuit stabilization of passivity by O2 the percentage chromium in the film increased with increasing open-circuit potential. X-ray photo-electron spectroscopy measurements indicated that the film thickness decreased with increasing open-circuit potential. 相似文献
8.
《Corrosion Science》1985,25(5):331-339
The evolution of active current density with time has been measured on new surfaces of FeCr and FeCr-1.5 at. % Mo alloys. The solutions used were 1M and 4M HCl. At several potentials, and at steady-state current densities as high as 150 mA/cm1, the inhibiting effect of molybdenum was established after the passage of a charge density equivalent to less than three monolayers of alloy. The results suggest that molybdenum acts by enriching at surface kink or step sites in the active state. 相似文献
9.
《Journal of Alloys and Compounds》2000,296(1-2):265-271
The PrAlxGe2−x cross-section of the Pr–Al–Ge system at 1073 K was studied. The homogeneity ranges of two ternary praseodymium alumogermanides, PrAl1.55–1.48Ge0.45–0.52 and PrAl1.42–0.98Ge0.58–1.02, were determined and their crystal structures refined from X-ray single-crystal diffraction data. The former has a hexagonal structure of the AlB2 type (hP3, P6/mmm, a=4.3223(3), c=4.2585(4) Å for x=1.476(2)) and the latter a tetragonal structure of the LaPtSi type (tI12, I41md, a=4.2534(5), c=14.641(2) Å for x=1). For both structures, the Al–Ge interatomic distances are close to the sum of the covalent radii, whereas the Pr–Al(Ge) distances agree well with the sum of the metallic radii. The solubility of Ge in the cubic Laves phase PrAl2 was found to be less than 2 at.%, that of Al in off-stoichiometric PrGe2−x less than 8 at.%. Al(Ge)-centered R6 trigonal prisms constitute a common geometrical feature of the structures of the germanides RGe2−x and alumogermanides RAlxGe2−x formed by the light rare-earth elements. Substitution of Ge for Al, or replacement of a large rare-earth element by a smaller one, leads to a reduction of the prism volume. 相似文献
10.
1INTRODUCTION LiCoO2isacommerciallyusedcathodemateri alforlithiumionbattery.Comparedwithothercathodematerials,suchasLiNiO2,LiMn2O4and theirdopedcompounds,LiCoO2hastheadvanta gesofhighpotential,excellentreversibility,longcyclelifeandreliableperformance[14].Thereare mainlyseveralmethodsforsynthesisofLiCoO2,suchasconventionalceramicmethod[5,6],sol gel synthesis[7],andlow temperaturesolutioncom bustion[8].Amongthesemethods,theconvention alceramicmethodhasbeenappliedtoindustrial productio… 相似文献
11.
1 Introduction Electrogenerative leaching process is a newly- developed technique in hydrometallurgy. Although its principle has developed since the late 1960s[1], this technique has been overlooked in metallurgy until ZHANG et al[2] introduced it to the … 相似文献
12.
Solid-state synthesis of Sr-and Co-doped LaMnO_3 perovskites 总被引:5,自引:0,他引:5
1 INTRODUCTIONAnimportantgoalinthedevelopmentofsolidoxidefuelcells (SOFCs)istoreducetheoperatingtemperatureofthefuelcellstackfrom 10 0 0℃tobe low 85 0℃ .Theprimarydriversare :1)togetanop timumtrade offbetweenperformanceandlifetimeofthestackand 2 )toreducetheoveral… 相似文献
13.
《Corrosion Science》1996,38(3):469-485
The corrosion resistance of arc-melted Ni10TaP alloys containing 0, 10 and 20 at% phosphorus in 12 M HCl solution at 30 °C was investigated. The alloys containing 0 and 10 at% phosphorus suffer severe corrosion. The addition of 20 at% phosphorus to crystalline Ni10Ta alloy results in a three-orders-of-magnitude decrease in the corrosion rate. The open circuit potentials of the Ni10Ta alloys containing 0 and 10 at% phosphorus stay almost constant in the active region of nickel, while the open circuit potential of the Ni10Ta20P alloy increases almost linearly in the initial 2 h. The Ni10Ta alloy consists of intermetallic Ni8Ta and immersion in 12 M HCl results in faceting dissolution. Ni10Ta10P alloy is composed of major Ni8Ta and Ni3P phases and minor Ni2Ta and Ni2P phases. Immersion of Ni10Ta10P alloy leads to preferential dissolution of the Ni8Ta phase and to continuous thickening of the corrosion product film consisting mostly of tantalum as cations. Ni 10Ta20P alloy consists of Ni2Ta, Ni3P, Ni2P and NiP phases. Immersion of Ni10Ta20P alloy gives rise to initial increase in elemental phosphorus on the surface as a result of selective dissolution of nickel and selective oxidation of tantalum. The formation of elemental phosphorus with a high cathodic activity is responsible for the initial ennoblement of the open circuit potential and for the formation of the passive film in which tantalum is highly concentrated. The higher corrosion resistance of Ni10Ta20P alloy than Ni10Ta10P alloy is attributable to the formation of the Ni2Ta phase with a higher tantalum content than the Ni8Ta phase which is the readily corroded major intermetallic phase in the Ni10Ta10P alloy. 相似文献
14.
《Acta Materialia》2001,49(14):2691-2699
The phase evolution in the Al2O3–Y2O3 system has been studied for 4, 10, 15 and 37.5% Y2O3 amorphous powders prepared by spray pyrolysis of nitrate precursor solutions. Two distinct metastable transformation sequences were identified for the amorphous powders upon heat treatment. Crystallisation accompanied by partitioning leads to a mixture of hexagonal YAlO3 and γ-Al2O3 (spinel structure). Partitionless crystallisation, on the other hand, leads directly to a γ-Al2O3 solid solution in dilute alloys, and garnet at temperatures as low as 800°C in the stoichiometric composition provided segregation is avoided during decomposition. Further heat treatment of a yttria-supersaturated γ-Al2O3 leads to the precipitation of the orthorhombic YAlO3 that is stable up to temperatures as high as 1600°C, while hexagonal YAlO3 converts to garnet, Y3Al5O12. A rationalisation of the phase evolution sequence has been attempted on the basis of kinetic considerations, cation coordination and semi-quantitative free energy–composition curves for the various competing phases. 相似文献
15.
YANG Huaming ZHANG Xiangchao YANG Wuguo HUANG Chenghuan QIU Guanzhou Department of Inorganic Materials School of Resources Processing Bioengineering Central South University Changsha China 《稀有金属(英文版)》2004,23(2)
ZrO_2-SnO_2 composite nanoparticles were prepared by heating the hydrate precursors synthesized by the chemicalco-precipitation reaction of ZrOCl_2 and SnCl_4. The precursors were examined by differential thermal analysis (DTA) andthermogravimetric analysis (TGA). The composite powder was characterized using X-ray diffraction (XRD), transmissionelectron microscopy (TEM) and desorption isotherm (Barrett-Joyner-Halenda method). The average crystal size of thenanoparticle ranges from 15 to 30 nm for the sample containing 5%-25% ZrO_2 (mass fraction). Most of the pores in theZrO_2-SnO_2 nanoparticles are about 10-20 nm in diameter. The composite powder is promising for chemical sensors. 相似文献
16.
《Corrosion Science》1987,27(3):239-247
Anodic oxide films formed on Fe26Cr in pH 2.0 H2SO4 solution in the presence and absence of Cl− ions have been investigated using electrochemical techniques and Auger electron spectroscopy (AES) combined with ion sputtering. It is possible to incorporate Cl− ions into passive oxide films formed over the entire passive potential range only when Cl− is present in the solution from the very beginning of film formation. Cl− ion incorporation does not cause any change in film thickness or Fe/Cr ratio, or any film thinning or film breakdown. A relatively short anodization in Cl−-free solution is sufficient to prevent any subsequent Cl− ion incorporation. The susceptibility of the passive film to Cl− attack appears to depend on the presence of small amounts of impurity in the alloy. A 99.97% pure alloy does not pit, whereas a 99.93% pure alloy, with larger concentrations of C, S, Mn, Co and Ni, does suffer intergranular attack in Cl− solution. 相似文献
17.
《中国有色金属学会会刊》2020,30(9):2510-2517
Combustion synthesis involving metallothermic reduction of Fe2O3 and TiO2 was conducted in the mode of self-propagating high-temperature synthesis (SHS) to fabricate FeAl-based composites with dual ceramic phases, TiB2/Al2O3 and TiC/Al2O3. The reactant mixture included thermite reagents of 0.6Fe2O3+0.6TiO2+2Al, and elemental Fe, Al, boron, and carbon powders. The formation of xFeAl−0.6TiB2−Al2O3 composites with x=2.0−3.6 and yFeAl−0.6TiC−Al2O3 composites with y=1.8−2.75 was studied. The increase of FeAl causes a decrease in the reaction exothermicity, thus resulting in the existence of flammability limits of x=3.6 and y=2.75 for the SHS reactions. Based on combustion wave kinetics, the activation energies of Ea=97.1 and 101.1 kJ/mol are deduced for the metallothermic SHS reactions. XRD analyses confirm in situ formation of FeAl/TiB2/Al2O3 and FeAl/TiC/Al2O3 composites. SEM micrographs exhibit that FeAl is formed with a dense polycrystalline structure, and the ceramic phases, TiB2, TiC, and Al2O3, are micro-sized discrete particles. The synthesized FeAl−TiB2−Al2O3 and FeAl−TiC−Al2O3 composites exhibit the hardness ranging from 12.8 to 16.6 GPa and fracture toughness from 7.93 to 9.84 MPa·m1/2. 相似文献
18.
QUAN Yu LIU Su-qin HUANG Ke-long FANG Dong ZHANG Xue-ying HOU Hua-wei 《中国有色金属学会会刊》2010,20(8):1458-1462
Eu-doped GaOOH nanoparticles with size of 5-8 nm were prepared by hydrothermal method using sodium dodecylbenzene sulfonate (SDBS) as surfactant. Eu-doped α-Ga2O3 and β-Ga2O3 were further fabricated by annealing GaOOH:Eu and then characterized by X-ray diffraction(XRD), transmission electron microscopy (TEM) and photoluminescence (PL). The TEM results show that monodisperse Eu3+-doped GaOOH nanoparticles form and then transform into Eu3+-doped α-Ga2O3 and β-Ga2O3 through annealing the GaOOH:Eu nanoparticles at 600 and 900 °C, respectively. PL studies indicate that GaOOH:Eu has the highest intensity at 618 nm. Luminescence quenching is observed at higher Eu3+ concentration in all samples. 相似文献
19.
《中国有色金属学会会刊》2006,16(A02):269-272
20.
FENG Peizhong QU Xuanhui Akhtar Farid S.H. Islam 《稀有金属(英文版)》2006,25(3):225-230
MoSi2 is presently regarded as the most important material for electrical heating and as one with huge potential for high temperature structural uses. MoSi2 and MoSi2 matrix composites were prepared by self-propagating high temperature synthesis (SHS). Pure MoSi2 was obtained and a compound of MoSi2 and WSi2was synthesized in the form of predominant solid solution (Mo,W)Si2. By adding aluminum of 5.5 at.% to Mo-Si, the crystal structure of MoSi2 changed into a mixture of tetragonal Cllb MoSi2and hexagonal C40 Mo(Si,Al)2. The (Mo,W)Si2-Mo(Si,Al)2-W(Si,Al)2 composite materials were synthesized by adding aluminum of 5.5 at.% to Mo-W-Si. However, if the amount of the added aluminum was not larger than 2.5 at.%, it did not have any significant effect. SHS is an effective technology for synthesis of MoSi2 and MoSi2 matrix composites. 相似文献