Heat Effects Occurring in the Supercooled Liquid State and Upon Crystallization of Metallic Glasses as a Result of Thermally Activated Evolution of Their Defect Systems

We show that the kinetics of endothermal and exothermal effects occurring in the supercooled liquid state and upon crystallization of metallic glasses can be well reproduced using temperature dependences of their shear moduli. It is argued that the interrelation between the heat effects and shear modulus relaxation reflects thermally activated evolution of interstitial-type defect system inherited from the maternal melt.

Time-dependent defects in integrable soliton equations

We study (1 + 1)-dimensional integrable soliton equations with time-dependent defects located at x = c ( t ), where c ( t ) is a function of class C 1 . We define the defect condition as a Bäcklund transformation evaluated at x = c ( t ) in space rather than over the full line. We show that such a defect condition does not spoil the integrability of the system. We also study soliton solutions that can meet the defect for the system. An interesting discovery is that the defect system admits peaked soliton solutions.

High-temperature electrical properties of undoped Cd1-xMnxTe (x = 0.05-0.55) crystals under cadmium vapor pressure

For the first time, the results of a study of the high-temperature electrical characteristics of undoped Cd1-xMnxTe single crystals in a wide composition range x = 0.05-0.55 are described. For this purpose, a study of Hall effect was made at the temperatures of 723–1073 K and isothermal and temperature dependences of electrical parameters were constructed. At 300 K, all the samples studied had a p-type conductivity, and Cd1-xMnxTe crystals with x = 0.02 and 0.15 had a low resistivity (102-103 Ohm×cm) while with x = 0.3 and 0.55 they had a relatively high ρ~ 107 Ohm×cm, which is due to an increase in the band gap with an increase in the MnTe content. The sample with the lowest Mn content (x = 0.02) showed the instability of the impurity-defect system during the first heating-cooling cycles: the conductivity type changed from p- to n- above 750 K and the mobility gradually increased as a result of the introduction of Cd atoms from the gas phase to the interstitial positions of the lattice. In this sample, during the first heating, the influence of donor impurities is noticeable, since the experimental line lg[e-] is significantly (~ 1-1.4 orders of magnitude) higher than that for model (undoped) CdTe, probably due to the donor behavior of Mn atoms. The crystal with the highest MnTe content (Cd0.45Mn0.55Te) also demonstrated the instability of the impurity-defect system, which was reflected in the decrease in the electrical conductivity after heat treatment at 773-873 K by almost one order of magnitude, which can be explained by a superposition of the results of the interaction of donor Cd atoms introduced from the gas phase with its native acceptor point defects (compensation) and the interaction of impurities between the matrix and Te inclusions. It has been established that a peculiarity of Cd1-xMnxTe crystals with a high content MnTe (x = 0.15, 0.55, and partially 0.3) is the inverse dependence of the carrier concentration on the cadmium vapor pressure caused by the onset of mixed conductivity of these crystals at high temperatures (T> 873 K). Accordingly, for these crystals, the value 1/RH at the moment of the onset of mixed conductivity characterizes the conditional rather than real mobility of the charge carriers. On the pressure dependences of the charge carrier concentration, the corresponding dependences are lower than the undoped CdTe (especially at low temperatures) for samples with x≥0.15 indicating that the introduction of a significant amount of MnTe (x≥0.15) leads to a decrease in the charge carrier concentration by 0.5-0.8 orders of magnitude (at ~ 773 K). This is due to the influence of Mn atoms, which form a stronger bond with Te than Cd, and therefore the generation of electrons requires more energy than in pure CdTe.

Dual defect system of tellurium antisites and silver interstitials in off-stoichiometric Bi2(Te,Se)3+ycausing enhanced thermoelectric performance

Thermoelectric performance was significantly enhanced with off-stoichiometric Bi2(Te,Se)3+yhaving the dual defect system of Te antisites and Ag interstitials.

WELDING DEFECT RATE ANALYSIS AND ITS RECTIFICATION USING SIX SIGMA METHOD DAN FMEA AT PT XYZ

In order to achieve the company quality objectives and to promote PT XYZto be the world leading fabricator which produces its products safely, with quality,and meeting the customer’s requirements while remaining competitive, therefore,PT XYZ tries hard to implement zero defect system in its welding production. PTXYZ has monitored the welding defect rate and tried to reduce that rate. Tominimize the defect rate down to zero defect, PT XYZ implements Six Sigmamethod in its welding production system, exercises systematic welding productionand implements FMEA (Failure Mode and Effect Analysis) method in order toreduce failure risk in its welding production. The combination both systems ormethods, i.e. between Six Sigma and FMEA above, when synergicallyimplemented would give promising results in the potential reduction of weld defectrate and in achieving of good quality condition which is product free from failuresor zero defect, and achieving quality objectives as well as maintaining theircustomers.