High-resolution electron microscopy of microstructure of MnF2 subjected to shock compression at 4.4 GPa

Microstructure of MnF₂ subjected to by shock compression at 4.4 GPa was examined using transmission electron microscopy (TEM). Lamellar structure consisting of twin-related domains of rutile-structure and intergrowth of α- PbO₂-type phase is observed in the electron diffraction pattern and TEM images. The crystallographic relationship between rutile and α- PbO₂-type phases can be expressed as and .     

Rapid reduction of titanium dioxide nano-particles by reduction with a calcium reductant

Micro-, submicron-, and nano-scale titanium dioxide particles were reduced by reduction with a metallic calcium reductant in calcium chloride molten salt at 1173 K, and the reduction mechanism of the oxides by the calcium reductant was explored. These oxide particles, metallic calcium as a reducing agent, and calcium chloride as a molten salt were placed in a titanium crucible and heated under an argon atmosphere. Titanium dioxide was reduced to metallic titanium through a calcium titanate and lower titanium oxide, and the materials were sintered together to form a micro-porous titanium structure in molten salt at high temperature. The reduction rate of titanium dioxide was observed to increase with decreasing particle size; accordingly, the residual oxygen content in the reduced titanium decreases. The obtained micro-porous titanium appeared dark gray in color because of its low surface reflection. Micro-porous metallic titanium with a low oxygen content (0.42 wt%) and a large surface area (1.794 m² g⁻¹) can be successfully obtained by reduction under optimal conditions.     

Magnetic properties of La-Co substituted M-type strontium hexaferrites prepared by polymerizable complex method

Magnetic properties of La-Co substituted M-type strontium hexaferrites were studied. The samples were prepared by polymerizable complex method. Crystal structure of samples has been investigated by powder X-ray diffraction (XRD). Single-phase M-type strontium hexaferrites with chemical composition of Sr_1.05−xLa_xFe_12−xCo_xO₁₉ (x=0-0.4) were formed by heating at 1173 K for 24 h in air. Magnetic properties were discussed by measurements of M-H curves with vibrating sample magnetometer (VSM). La-Co substituted M-type strontium hexaferrites prepared by polymerizable complex method showed typical magnetic hysteresis of hard ferrite. The coercive force increased significantly by La-Co substitution with polymerizable complex method. Maximum coercive force achieved in this study is 8.0 kOe (640 kA/m). Scanning electron microscopy revealed that the prepared ferrite particles have plate-like shape of diameter range between 20 and 500 nm.     

Invar effects on some iron-base amorphous alloys

The thermal expansion and magnetic properties of Fe-B and Fe-P amorphous alloys prepared from melts have been investigated. These amorphous alloys show distinct Invar characteristics. heir magnetic properties are also very similar to those of Fe-Ni crystalline Invar alloys; that is, the high-field susceptability and forced-volume magnetostriction are remarkably large, the magnetic moment per Fe atom does not increase linearly, the Curie temperature decreases with a decrease in concentration of B or P, and their reduced their magnetization curves are much flatter than those of crystalline pure Fe.     

Monte carlo studies of phase transitions in polymer blends and block copolymer melts

Summary The unmixing transition of both symmetrical polymer blends AB (i.e. chain lengthsN _A=N _B=N) and asymmetrical ones (N _B/N _A=2,3) is studied by large-scale Monte Carlo simulations of the bond fluctuation model. Combination of semi-grand-canonical simulation techniques, ?histogram reweighting? and finitesize scaling allows an accurate location of the coexistence curve in the critical region. The variation of the critical temperature with chain length (N) is studied and compared to theoretical predictions. For the symmetrical case, use of chain lengths up toN=512 allows a rough estimation of crossover scaling functions for the crossover from Ising to mean-field exponents. The order-disorder transitions in melts of both symmetric (compositionf=N _A/(N _A+N _B)=1/2) and asymmetric (f=3/4) block copolymers is studied for very short chains (16≤N≤60). The interplay between structure and chain configuration is emphasized. Qualitative evidence for ?dumbell formation? of chains and vacancy enrichment in A-B-interfaces and near hard walls is presented. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.     

On a p-Local Geometry Associated with a Complex of Non-Trivial p-Subgroups

Let D be a complex of non-trivial p-subgroups of a finite groupG, closed under G-conjugation. In this paper, a p-local geometry^p(G; D) is introduced for G associated with the complex D. Thehomotopy equivalence between ^p(G; D) and D is also studied.2000 Mathematics Subject Classification 20E15, 51E24.     

Non-existence of phase transition of oriented percolation on Sierpinski carpet lattices

 A percolation problem on Sierpinski carpet lattices is considered. It is obtained that the critical probability of oriented percolation is equal to 1. In contrast it was already shown that the critical probability p _c of percolation is strictly less than 1 in Kumagai [9]. This result shows a difference between fractal-like lattice and ℤ ^d lattice. Received: 15 May 2002 / Revised version: 11 October 2002 / Published online: 21 February 2003 Mathematics Subject Classification (2000): Primary: 60K35, 82B43; Secondary: 82B26