We develop a free energy density to model a structural first-order phase transformation from a high-temperature cubic phase to a low-temperature tetragonal phase. The free energy density models the softening of the elastic modulus controlling the low-energy path from the cubic to the tetragonal lattice, the loss of stability of the tetragonal phase at high temperatures and the loss of stability...

Possible phase transformation kinetic pathways from the high temperature b phase to the low temperature (a+ b) two-phase Ti alloys were analyzed using the graphical thermodynamic method and the assumption that diffusionless and displacive transformations take place much faster than phase separation which requires long-range diffusion. It is shown that depending on the composition of a b-stabili...

We have investigated the phase transformation of bulk MoS2 crystals from the metastable metallic 1T/1T' phase to the thermodynamically stable semiconducting 2H phase. The metastable 1T/1T' material was prepared by Li intercalation and deintercalation. The thermally driven kinetics of the phase transformation were studied with in situ Raman and optical reflection spectroscopies and yield an acti...

Phase transformation affects multiphase flow in geothermal and gas-condensate reservoirs due to the same substance occurring in different phases. These effects change the phase behavior and the flow characteristics. The goals of this research were to compare the flow behavior and relative permeabilities difference between two-phase flow with and without phase transformation effects in smooth-wa...

Different phases of iron oxide were obtained by hydrothermal treatment of ferric solution at 200°C with the addition of either KOH, ethylenediamine (EDA), or KOH and EDA into the reaction system. As usually observed, the α-Fe2O3 hexagonal plates and hexagonal bipyramids were obtained for reaction with KOH and EDA, respectively. When both KOH and EDA were added into the reaction system, we obser...

The most efficient way to tune microstructures and mechanical properties of metallic alloys lies in designing and using athermal phase transformations. Examples are shape memory alloys and high strength steels, which together stand for 1,500 million tons annual production. In these materials, martensite formation and mechanical twinning are tuned via composition adjustment for realizing complex...

There are two crystalline modifications of zinc sulphide. The high-temperature hexagonal (e) phase and the low-temperature cubic (/~) phase exhibit a reconstructive transformation at a transition temperature of about 1020 ° C. The transformation of e phase back to ~ phase is a sluggish process compared to that of/3 to :~ [1], therefore once it is formed the a phase will remain as a metastable p...

Objective(s): NiTi is known as the most important material for manufacturing implants and medical devises duo to its shape memory and superelasticity properties, high energy damping, and high corrosion resistance. Methods: In this project, the possibility of producing nanostructured NiTi implant with high porosity was investigated. For reaching to the nan...

Magnetization and crystal structure of Eu1-~Ca,Mn0; (OFx<l) perovskite have been studied. I t is shown that these compou~ids call be divided into four concentration regions in which different magnetic phases coexlst. The antiferromagnetic phases are associated with the regular arrangement of Mn3+ and Mn4+ ions in ratios 1:0, I:]. 1:3 and 0:I respectively. The ferromagnetic phases are attributed...