Showing papers by "Yi Chen published in 1991"
TL;DR: In this article, a Ni•P ultrafine amorphous alloy was prepared by reacting nickel chloride and sodium hypophosphite in an aqueous solution and the dynamic process of the reaction has been studied.
Abstract: Ni‐P ultrafine amorphous alloy particles have been prepared by reacting nickel chloride and sodium hypophosphite in an aqueous solution. X‐ray diffraction revealed the amorphous structure of the particles and transmission electron microscopy showed that the particles are spherical, with an average diameter of about 150 nm. X‐ray photoelectron spectroscopy confirmed that all nickel and phosphorus atoms are in the elementary state on the surface of the particles, which implied the alloying state of the particles. The dynamic process of the reaction has been studied. It is found that the reaction ended within 65 min at a pH value of 10 and 351 K when the sodium hypophosphite was exhausted, and the unreacted solid residue Ni(OH)2 should be washed out with ammonia solution to obtain ‘‘pure’’ Ni‐P ultrafine amorphous alloy particles.
24 citations
TL;DR: In this article, a new kind of ultrafine amorphous particles Fe82P11B7 have been successfully prepared by the reaction of Fe(III) chloride, sodium hypophosphite and potassium borohydride in aqueous solution.
Abstract: A new kind of ultrafine amorphous particles Fe82P11B7 have been successfully prepared by the reaction of Fe(III) chloride, sodium hypophosphite and potassium borohydride in aqueous solution. X‐ray diffraction and Mossbauer spectroscopy confirmed the amorphous structure of the particles and scanning electron microscopy showed that the particles are nearly spherical with the diameters from 150 to 350 nm. The structure relaxation and crystallization of the amorphous particles were also studied by Mossbauer spectroscopy. It is found that the particles began to crystallize when annealed at 573 K, below which, no crystalline phases were formed, but the amorphous structure significantly varied. The particles crystallized to form α‐Fe and Fe3(P0.6B0.4) completely when annealed at 673 and 773 K.
19 citations
TL;DR: Thermodynamic properties of the spin-1/2 Heisenberg ferromagnet are calculated by using Handscomb's Monte Carlo method and find that the susceptibility diverges exponentially at zero temperature.
Abstract: Thermodynamic properties of the spin-1/2 Heisenberg ferromagnet are calculated by using Handscomb's Monte Carlo method. Several methods of analyses are used to determine critical properties of the model. For a square lattice we find that the susceptibility diverges exponentially at zero temperature. That is, \ensuremath{\chi}\ensuremath{\sim}exp[b(J/${\mathit{k}}_{\mathit{B}}$T)] with the constant b=4.5\ifmmode\pm\else\textpm\fi{}0.5, which is lower than the prediction (b=2\ensuremath{\pi}) of a modified spin-wave theory. For the simple-cubic lattice, we find that the critical temperature ${\mathit{k}}_{\mathit{B}}$${\mathit{T}}_{\mathit{c}}$/J=1.68\ifmmode\pm\else\textpm\fi{}0.01, and the ratio of the exponents \ensuremath{\gamma}/\ensuremath{
u}=2.0\ifmmode\pm\else\textpm\fi{}0.05, which are in good agreement with the estimates of the high-temperature series-expansion method.
11 citations
15 Mar 1991-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, two new metastable phases were found in the as-quenched condition, a simple cubic structure with a lattice constant of 0.63 nm and a body centred cubic (b.c.c.) structure, respectively.
Abstract: An FeCSi alloy treated with a nodularizer, Fe-45at.%Si-3at.%Mg was melt quenched by single roller melt spinning. Two new metastable phases were found in the as-quenched condition. The major metastable phase is a simple cubic structure with a lattice constant of 0.63 nm. By using the convergent beam electron diffraction technique, the detailed structure was analyzed to be point group 432 and space group P4 1 32 or P4 3 32. The second metastable phase is a body centred cubic (b.c.c.) structure with a lattice constant of 0.89 nm. Decomposition of these two metastable phases was studied by in situ heating in a transmission electron microscope. At around 300°C, graphite particles precipitate out in the simple cubic structured metastable phase. However, no phase transition was noted in the b.c.c. structured metastable phase after heating at around 300 °C for 2 h.
11 citations
01 Nov 1991
TL;DR: This paper investigates optimal restoration for the union noise model based upon the individual granulometric pattern spectra of the image and noise based upon a class of random-grain image and Noise models.
Abstract: Morphological tau-openings are binary filters that are translation invariant, increasing, antiextensive, and idempotent. The Matheron representation for tau-opening filters show that they are always given by unions of elementary openings. Historically tau-openings have been employed to restore binary images corrupted by union noise. This paper investigates optimal restoration for the union noise model based upon the individual granulometric pattern spectra of the image and noise. It does so for a class of random-grain image and noise models.
7 citations
TL;DR: Chiral symmetry breaking in the continuum limit of SU(2) Yang-Mills theory coupled to an unflavored fermion on a two-dimensional lattice is found using a hybrid algorithm based on the projector hamiltonian Monte-Carlo method.
Abstract: We study chiral symmetry of SU(2) Yang-Mills theory coupled to an unflavored fermion on a two-dimensional lattice using a hybrid algorithm based on the projector Hamiltonian Monte Carlo method. The correlation functions of a chiral condensate and of fermion occupation number are calculated. We find chiral-symmetry breaking in the continuum limit. The theory is calculated to reside in only one phase in which chiral symmetry is broken.