LI MeiyaShantou University
,
Shantou
,
Guangdong
,
ChinaCOWLAMNUniversity of Sheffield
,
Sheffield S3 7RH
,
UKCOCCOGUniversita di Sassari
,
via Vienna 2
,
07100 Sassari
,
Italy Manuscript received 10 May
,
1994
金属学报(英文版)
Small angle neutron scattering(SANS) technique has been used to investigate the Ni_(50)Mo_(50) system prepared by mechanical alloying(MA). Significant changes of the scattering intensity have been observed among the samples with different milling time.Interesting fractal-like behavior of the sample system have been found and attempts have been made to determine the fractal dimensions. It is expected that the fractal dimension can be related to the different stages of MA to some extent.
关键词:
mechanical alloying
,
null
,
null
Acs Nano
This paper presents a systematic investigation on the incorporation of chemical exfoliation graphene sheets (GS) in TiO(2) nanoparticle films via a molecular grafting method for dye-sensitized solar cells (DSSCs). By controlling the oxidation time in the chemical exfoliation process, both high conductivity of reduced GS and good attachment of TiO(2) nanoparticles on the GS were achieved. Uniform GS/TiO(2) composite films with large areas on conductive glass were prepared by electrophoretic deposition, and the incorporation of 65 significantly improved the conductivity of the TiO(2) nanoparticle film by more than 2 orders of magnitude. Moreover, the power conversion efficiency for DSSC based on GS/TiO(2) composite films is more than 5 times higher than that based on TiO(2) alone, indicating that the incorporation of GS is an efficient means for enhancing the photovoltaic (PV) performance. The better PV performance of GS/TiO(2) DSSC is also attributed to the better dye loading of GS/TiO(2) film than that of TiO(2) film. The effect of GS content on the PV performances was also investigated. It was found that the power conversion efficiency increased first and then decreased with the increasing of GS concentration due to the decrease in the transmittance at high GS content. Further improvements can be expected by fully optimizing fabrication conditions and device configuration, such as increasing dye loading via thicker films. The present synthetic strategy is expected to lead to a family of composites with designed properties.
关键词:
graphenes;titanium dioxide;molecular-level incorporation;composite;films;dye-sensitized solar cells;oxide;transparent;nanosheets;reduction;gas
Journal of Materials Science
Based on the structure characteristic of Ti3AlC2 and the easy formation of Ti3Al1 -x Si (x) C-2 solid solution, a Si interlayer was selected to join Ti3AlC2 layered ceramic by diffusion bonding method. Joining was performed at 1,300-1,400 degrees C for 120 min under 5 MPa load in an Ar atmosphere. The phase composition and interface microstructure of the joints were investigated by XRD, SEM and EPMA. The results revealed that Ti3Al(Si)C-2 solid solution formed at the interface. The mechanism of bonding is attributed to silicon diffusing inward the Ti3AlC2. The strength of joints was evaluated by a 3-point bending test. The jointed specimens exhibit a high flexural strength of 285 +/- 11 MPa, which is about 80% of that of the Ti3AlC2; and retain this strength up to 1,000 degrees C. The high mechanical performance of the joints indicates that diffusion bonding via a Si interlayer is effective to bond Ti3AlC2 ceramic.
关键词:
liquid reaction synthesis;oxidation behavior;solid-solutions;aluminum;ti2alc;al
Scripta Materialia
The oxidation behavior of Zr(2)Al(3)C(4) at 1600 and 1750 degrees C was studied by means of induction heating. The oxidation kinetics follows a linear law and the interfacial reaction between Zr(2)Al(3)C(4) and O(2) is the rate-limiting step for scale growth. The microstructure of oxide scales gradually changes from intragranular (small ZrO(2) particles embedded in large Al(2)O(3) grains) to an interpenetrating dual-phase form its the exposure time increases, which is ascribed to the temperature decay of the top scale surface with scale growth. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
关键词:
Zr(2)Al(3)C(4);ZrO(2);Al(2)O(3);Oxidation;Induction heating;al2o3/zro2 composites;bulk zr2al3c4;grain-growth;alumina;coatings;yttria
Journal of Materials Science
Weibull modulus of bending strength of nanolayer-grained ceramic Ti3SiC2 was estimated with over 50 specimens, using the least square method, the moment method and the maximum likelihood technique, respectively. The result demonstrated that the m-value of this layered ceramic ranged from 25 to 29, which is much higher than that of traditional brittle ceramics. The reason of high Weibull modulus was due to high damage tolerance of this material. Under stress, delamination and kinking of grains and shear slipping at interfaces give this material high capacity of local energy dissipation and easy local stress relaxation, leading to the excellent damage tolerance of Ti3SiC2. The effect of amounts of specimens on the reliability of the estimated m-values was also investigated. It was confirmed that the stability of the estimated m-value increased with increasing numbers of specimens. The parameter obtained using the maximum likelihood technique showed the highest reliability than other methods. The ranges of failure probability were determined using the Weibull estimates calculated from the maximum likelihood technique.
关键词:
ceramics;modulus;ti3alc2;microstructure;indentations;strength
Journal of Applied Physics
The crystal structure and superconducting properties of RuSr(2-x)Ba(x)GdCu(2)O(8) (0less than or equal toxless than or equal to0.1) have been investigated. X-ray powder diffraction (XRD) patterns show that the solid solution range is 0less than or equal toxless than or equal to0.1. The superconducting transition temperature was raised up to 35 K (zero) and 62 K (onset) for x=0.07, from 16 K (zero) and 45 K (onset) for x=0.0, and then T(C) decreases with x when x>0.07. Rietveld refinement for XRD data of RuSr(2-x)Ba(x)GdCu(2)O(8) show that the apical Cu-O(1) bond length increases with an increase of x, while the Ru-O(1) bond length decreases, This may account for the enhancement of the superconducting transition temperature. (C) 2004 American Institute of Physics.
关键词:
dc magnetization;rusr2gdcu2o8;ferromagnetism;coexistence;gd
Acta Chimica Sinica
A conventional high voltage wire-like plasma can be greatly enhanced and spread by pulsed microwave to form an umbrella-like plasma continuously distributed in reactor. By use of this plasma, methane is directly converted to C-2 hydrocarbons at high yield under the condition of atmospheric or higher pressure. The effect of pressure, microwave power, pulse duration, molar ratio of H-2/CH4 and flow rate on the methane conversion was investigated. Higher conversion of methane is achieved by proper choice of parameters, and the products only comprise ethylene and acetylene; The molar ratio of C2H2/C2H4 could be adjusted through changing the pressure. With total flow rate of 300 mL/min, H-2/CH4 molar ratio of 2, pressure of 0.13 MPa, peak microwave power of 120 W, pulse duty factor of 400/400 ms, conversion of methane and yield of C-2 could reached up to 59.2% and 52% respectively.
关键词:
higher pressure;low temperature;microwave plasma;natural gas;methane
Physical Review B
The two-orbital double-exchange model is employed for the study of the magnetic and orbital orders in (RMnO3)(n)/(AMnO(3))(2n) (R: rare earths; A: alkaline-earth metal) superlattices. The A-type antiferromagnetic order is observed in a broad region of parameter space for the case of SrTiO3 as substrate, in agreement with recent experiments and first-principles calculations using these superlattices. In addition, a C-type antiferromagnetic state is also predicted to be stabilized when using substrates like LaAlO3 with smaller lattice constants than SrTiO3, again in agreement with first-principles results. The physical mechanism for the stabilization of the A and C magnetic transitions is driven by the orbital splitting of the x(2) - y(2) and 3z(2) - r(2) orbitals. This splitting is induced by the Q(3) mode of Jahn-Teller distortions created by the strain induced by the substrates. In addition to the special example of (LaMnO3)(n)/(SrMnO3)(2n), our phase diagrams can be valuable for the case where the superlattices are prepared employing narrow bandwidth manganites. In particular, several nonhomogenous magnetic profiles are predicted to occur in narrow-bandwidth superlattices, highlighting the importance of carrying out investigations in this mostly unexplored area of research.
关键词:
oxide interfaces;phase-separation;electronics;manganites;bias
