Journal of Applied Physics
The structure changes and electrical properties in Ca4Mn3O10 under high pressure at room temperature have been studied using energy-dispersive x-ray diffraction with synchrotron radiation and resistance and capacitance measurements. A phase transition from an orthorhombic to a tetragonal phase occurred during increasing pressure to above 19.3 GPa. The equation of state of Ca4Mn3O10 was obtained from the V/V-0-P relationship. The bulk modulus B-0 and its first-order derivative B-0' of Ca4Mn3O10 were calculated based on the Birch-Murnaghan equation. (C) 2002 American Institute of Physics.
关键词:
2-dimensional ferromagnet la2-2xca1+2xmn2o7;ruddlesden-popper compound;giant magnetoresistance;crystal;oxides;films
Pan Ting
,
Song Wenjing
,
Cao Xiaodong
,
Wang Yingjun
材料科学技术（英）
doi:10.1016/j.jmst.2016.01.007
Gelatin/Alginate hydrogels were engineered for bioplotting in tissue engineering. One major drawback of hydrogel scaffolds is the lack of adequate mechanical properties. In this study, using a bioplotter, we constructed the scaffolds with different pore architectures by deposition of gelatin/alginate hydrogels layer-by-layer. The scaffolds with different crosslinking degree were obtained by post-crosslinking methods. Their physicochemical properties, as well as cell viability, were assessed. Different crosslinking methods had little influence on scaffold architecture, porosity, pore size and distribution. By contrast, the water absorption ability, degradation rate and mechanical properties of the scaffolds were dramatically affected by treatment with various concentrations of crosslinking agent (glutaraldehyde). The crosslinking process using glutaraldehyde markedly improved the stability and mechanical strength of the hydrogel scaffolds. Besides the post-processing methods, the pore architecture can also evidently affect the mechanical properties of the scaffolds. The crosslinked gelatin/alginate scaffolds showed a good potential to encapsulate cells or drugs.
关键词:
Bioplotting
,
Tissue engineering
,
Scaffolds
,
Gelatin
,
Alginate
Andrej Atrens
材料科学技术（英）
Corrosion research by Atrens and co-workers has made significant contributions to the understanding of the service performance of engineering materials. This includes: (1) elucidated corrosion mechanisms of Mg alloys, stainless steels and Cu alloys, (2) developed an improved understanding of passivity in stainless steels and binary alloys such as Fe-Cr, Ni-Cr, Co-Cr, Fe-Ti, and Fe-Si, (3) developed an improved understanding of the melt spinning of Cu alloys, and (4) elucidated mechanisms of environment assisted fracture (EAF) of steels and Zr alloys. This paper summarises contributions in the following: (1) intergranular stress corrosion cracking of pipeline steels, (2) atmospheric corrosion and patination of Cu, (3) corrosion of Mg alloys, and (4) transgranular stress corrosion cracking of rock bolts.
关键词:
Stress corrosion cracking
,
null
,
null
Science
Strengthening materials traditionally involves the controlled creation of internal defects and boundaries so as to obstruct dislocation motion. Such strategies invariably compromise ductility, the ability of the material to deform, stretch, or change shape permanently without breaking. Here, we outline an approach to optimize strength and ductility by identifying three essential structural characteristics for boundaries: coherency with surrounding matrix, thermal and mechanical stability, and smallest feature size finer than 100 nanometers. We assess current understanding of strengthening and propose a methodology for engineering coherent, nanoscale internal boundaries, specifically those involving nanoscale twin boundaries. Additionally, we discuss perspectives on strengthening and preserving ductility, along with potential applications for improving failure tolerance, electrical conductivity, and resistance to electromigration.
关键词:
strain-rate sensitivity;stacking-fault energy;nano-scale twins;cu-al;alloys;nanocrystalline metals;mechanical-properties;activation;volume;copper;deformation;behavior
Journal of Physics and Chemistry of Solids
La1-xCaxCrO3 (x = 0.0-0.5) samples were prepared by the sol-gel method. The sintering temperature of the samples can decrease to 1573 K. The crystal structures of La1-xCaxCrO3 at room temperature all are of the orthorhombic perovskite GdFeO3-type. XPS analysis indicates that the chromium ions are in a mixed valence state. The introduction of Ca2+ into the lattice is compensated by the oxidation of Cr3+ to Cr6+. With increasing x, the amount of Cr6+ increases. The presence of Cr6+ is one of the key factors affecting the electrical conductivity of La1-xCaxCrO3. (C) 2001 Published by Elsevier Science Ltd.
关键词:
ceramics;photoelectron spectroscopy;electrical conductivity
F.F.Hammad
,
M.Sh.Khalil
,
A. H. Salama
材料科学技术（英）
The electrical conductivity of pure CaTiO3 and that containing 0.5 similar to5.0 mole fraction CuO as dopant were measured in the temperature range 291 similar to 773 K. The conductivity values varied as a function of temperature and dopant concentration. The activation energy in the lower temperature range depended on the impurity content while in the high temperature range it indicated a value of energy gap width. The infrared absorption spectra in the range of 100 similar to 4000 cm(-1) revealed the presence of two main bands at 340 and 570 cm(-1) which were assigned to TiO6 octahedral normal mode. Bands in the range of 106 similar to 270 cm(-1) were due to the vibration of anion TiO3-2. Some bands were observed at higher values due to the presence of lattice imperfections. There was a slight shift in band position with increasing dopant concentration which favors the formation of orthorhombic modification.
关键词:
Na Yin Hongchao Wang Chunlei Wang
材料科学技术（英）
Lanthanum ferrites ceramics La0.9A0.1FeO3 (A=Mg, Ca, Sr, Ba) have been prepared by solid state reaction. X-ray power diffraction analysis reveals that all samples are of pure perovskite structure with orthorhombic phase. Electrical conductivity and Seebeck coefficient have been measured in vacuum within the temperature range between room temperature and 800°C. The electrical conductivity shows semiconducting behavior. Temperature dependence of electrical conductivity indicates that adiabatic small-polaron hopping mechanism is dominant for their electric transportations. Seebeck coefficients are positive for samples, suggesting p-type conduction in the whole temperature range. The highest Seebeck coefficient is found to be 654 μV/K for La0.9Mg0.1 FeO3. Except La0.9Ba0.1FeO3, the electrical conductivity of La0.9A 0.1FeO3 increases with increasing atomic number of the A-site element, while Seebeck coefficient decreases.
关键词:
La0:9A0:1FeO3 ceramics
,
electrical conductivity
,
Seebeck coefficient
A.M. El-Sayed F.M. Ismail S.M. Yakout
材料科学技术（英）
Carbon dioxide gas sensors based on BaTiO3-CuO composite with different concentrations of Ag addition (1, 1.5 and 2 wt%) have been prepared by stander ceramic method and sintered at 500 and 700°C for 5 h. Electrical conductivity and gas sensing properties of the prepared samples were investigated. Electrical conductivity measurement was used to characterize the obtained sintered sensor pellets. It was found that electrical conductivity and the sensitivity to CO2 were improved with Ag addition and sintering. The correlation between Ag content at different sintering temperature and sensing characteristics towards CO2 is discussed.
关键词:
BaTiO3-CuO composite; Ag addition
A.M. El-Sayed F.M. Ismail S.M. Yakout
材料科学技术（英）
Carbon dioxide gas sensors based on BaTiO3-CuO composite with different concentrations of Ag addition (1, 1.5 and 2 wt%) have been prepared by stander ceramic method and sintered at 500 and 700°C for 5 h. Electrical conductivity and gas sensing properties of the prepared samples were investigated. Electrical conductivity measurement was used to characterize the obtained sintered sensor pellets. It was found that electrical conductivity and the sensitivity to CO2 were improved with Ag addition and sintering. The correlation between Ag content at different sintering temperature and sensing characteristics towards CO2 is discussed.
关键词:
BaTiO3-CuO composite; Ag addition
