Investigation of the structural, optical, elastic and electrical properties of spinel LiZn2Fe3O8 nanoparticles annealed at two distinct temperatures

Nanoparticles of Li0.5ZnFe1.5O4 (LiZn2Fe3O8) with the spinel structure were prepared by a sol–gel auto-combustion method at two different annealing temperatures.

Alteration of Thermal Characteristics of Polymer for the Purpose of Creating a Two-Stage Shape Memory Polymer

A polymer fabricated by mixing PU soft segment and epoxy bore the thermal characteristics of the melting temperature, Tm, of PU soft segment and the glass transition temperature, Tg, of epoxy. The polymer fabricated even exhibited the shape memory effect at the Tg and Tm. Based on this observation, it was speculated that simply mixing two polymers bearing totally different thermal characteristics each other could result in a two-stage SMP, which could exhibit the shape memory effect at the two distinct temperatures. However, it was actually observed that the two-stage SMP was not always successfully created by that method. But DSC measurements revealed that such an unsuccessfully fabricated SMP still bore the thermal characteristics of its ingredient polymers. Hence, the mixing of appropriate polymers still could result in a new two-stage SMP, and the method of two-polymer-mixing must be still an effective method for creating a two-stage SMP.

Electrical Characterisation of 4H-SiC Epitaxial Samples Treated by Hydrogen or Helium

This paper presents results of investigations about the influence of Hydrogen (introduced by annealing or plasma implantation), and Helium (ion implantation followed by a proper annealing for creating nanocavities) on the electrical properties of 4H-SiC n-type epitaxial samples. First, 4HSiC epitaxial layers were hydrogenated either by annealing under H2 ambient or by a RF plasma treatment. This last process took place before or after the deposition of Schottky contacts. Two different annealing temperatures were imposed (300°C and 400°C), as well as two plasma hydrogen doses for the same low energy. An improvement of electrical characteristics (25 % increasing of the minority carrier diffusion length, lowering of ideality factor, better switching characteristic) is detected for samples annealed at 400°C. The treatment of 4H-SiC surface in hydrogen plasma through Ni metal also increases the diffusion length, but not sufficiently to have an effect on I-V characteristics. A second set of 4H-SiC epitaxial layers were secondly implanted with He+ ions at two distinct temperatures. An annealing at 1700°C during 30 minutes under argon atmosphere was then carried out. C-V measurements revealed the presence of a high charge density zone around the nanocavities, containing fixed negative charges, opposite in sign to the donor atoms.

Tribochemistry of ZDOL Decomposition on Carbon Overcoats in Ultra-High Vacuum (UHV)

Tribochemical studies of the effect of lubricant bonding on the tribology of the head/disk interface (HDI) were conducted using hydrogenated (CHx) carbon disk samples coated with perfluoropolyether ZDOL lubricant. The studies involved drag tests with uncoated and carboncoated Al2O3-TiC sliders and also thermal desorption experiments in an ultra-high vacuum (UHV) tribochamber. We observed that a larger mobile lubricant portion significantly enhances the wear durability of the (head/disk interface) HDI by providing a reservoir to constantly replenish the lubricant displaced in the wear track during drag tests. In the thermal desorption tests we observed two distinct temperatures of desorption. The mobile ZDOL layer is desorbed at the lower thermal desorption temperature and the residual bonded ZDOL layer is desorbed at the higher thermal desorption temperature. We also observed that the hydrogen evolution from CHx overcoats initiates lubricant catalytic decomposition with uncoated Al2O3/TiC sliders, forming CF3 (69) and C2F5 (119). The generation of Hydroflouric acid (HF) during thermal desorption experiments provides the formation mechanism of Lewis acid, which is the necessary component for catalytic reaction causing Z-DOL lube degradation.

Tribochemistry of ZDOL Decomposition on Carbon Overcoats in Ultra-High Vacuum (UHV)

ABSTRACTTribochemical studies of the effect of lubricant bonding on the tribology of the head/disk interface (HDI) were conducted using hydrogenated (CHx) carbon disk samples coated with perfluoropolyether ZDOL lubricant. The studies involved drag tests with uncoated and carbon-coated A1203-TiC sliders and also thermal desorption experiments in an ultra-high vacuum (UHV) tribochamber. We observed that a larger mobile lubricant portion significantly enhances the wear durability of the (head/disk interface) HDI by providing a reservoir to constantly replenish the lubricant displaced in the wear track during drag tests. In the thermal desorption tests we observed two distinct temperatures of desorption. The mobile ZDOL layer is desorbed at the lower thermal desorption temperature and the residual bonded ZDOL layer is desorbed at the higher thermal desorption temperature. We also observed that the hydrogen evolution from CHx overcoats initiates lubricant catalytic decomposition with uncoated A1203/TiC sliders, forming CF3 (69) and C2F5(119). The generation of Hydroflouric acid (HF) during thermal desorption experiments provides the formation mechanism of Lewis acid, which is the necessary component for catalytic reaction causing Z-DOL lube degradation

Intracellular interactions of Leishmania mexicana with a cell line from Toxorhynchites amboinensis (77M-248) larvae

Leishmania is an intracellular parasite that lives in phagocytic vacuoles of macrophages . The promastigote form of the parasite is flagellated and interacts with macrophages through specific cell membrane receptors . Once inside phagocytic vacuoles, the parasite differentiates into the amastigote form which is small and aflagellated. Part of the life cycle of the parasite occurs in the lumen of the digestive tract of an insect, with a body temperature of 25-27 °C that promotes the preferential differentiation of the promastigote form. A cell line ( TRA-248 ) isolated from Toxorhynchites amboinensis has been adapted to grow at two different temperatures 24° and 34°C, and used in the study of dengue virus. This quality of TRA-248 cells is of relevance since they permit to analyze the behavior of leishmania in an insect cell at two distinct temperatures. In this study, TRA- 248 cells and promastigotes interacted in culture at 24° and 34°C, for 12, 24 and 48 hrs and determine if the parasites are phagocyted and able to differentiate into the amastigote form. Also, the activity of acid phosphatase was compared between TRA-248 cells and macrophages.