40 research outputs found
Macro- and microscopic properties of strontium doped indium oxide
Solid state synthesis and physical mechanisms of electrical conductivity
variation in polycrystalline, strontium doped indium oxide In2O3:(SrO)x were
investigated for materials with different doping levels at different
temperatures (T=20-300 C) and ambient atmosphere content including humidity and
low pressure. Gas sensing ability of these compounds as well as the sample
resistance appeared to increase by 4 and 8 orders of the magnitude,
respectively, with the doping level increase from zero up to x=10%. The
conductance variation due to doping is explained by two mechanisms:
acceptor-like electrical activity of Sr as a point defect and appearance of an
additional phase of SrIn2O4. An unusual property of high level (x=10%) doped
samples is a possibility of extraordinarily large and fast oxygen exchange with
ambient atmosphere at not very high temperatures (100-200 C). This peculiarity
is explained by friable structure of crystallite surface. Friable structure
provides relatively fast transition of samples from high to low resistive state
at the expense of high conductance of the near surface layer of the grains.
Microscopic study of the electro-diffusion process at the surface of oxygen
deficient samples allowed estimation of the diffusion coefficient of oxygen
vacancies in the friable surface layer at room temperature as 3x10^(-13)
cm^2/s, which is by one order of the magnitude smaller than that known for
amorphous indium oxide films.Comment: 19 pages, 7 figures, 39 reference
Thermal Stability and Shelf-life of High Energy Fuel for Torpedoes (Short Communication)
1,2-Dinitroxy propane-based liquid fuel is an advanced high energy fuel for torpedoes. The high energy fuel is used with an oxidiser, viz., hydroxyl ammonium perchlorate as a bi-propellant system for torpedo propulsion. Thermal stability of high energy fuel has been arrived at by differential thermal analysis and also by following the depletion in stabiliser content as well as increase in acidity with ageing. Rate constant for decomposition, activation energy for depletion of 2-nitro diphenylamine (2-NDPA) and shelf-life of high energy fuel have been determined. Due to the high vapour pressure of high energy fuel (because of 1,2-dinitroxy propane ), usual experimental set up could not be used and the sample was conditioned in sealed tubes. The shelf-life of high energy fuel is arrived at using Woolwich, Berthelot and Arrhenius equations and the results obtained are 100 years, 125 years and 276 years, respectively. Considering the safety aspect, the lowest value, viz., 100 years is recommended as safe life of high energy fuel. This work confirms the reported estimates of the good storage stability of high energy fuel