Phase Decomposition Temperature Research Articles

α'-(Fe<sub>100-x</sub>Ni<sub>x</sub>)-N(x=5-30)薄膜の構造と飽和磁化

Fe-Ni-N films were fabricated on MgO{100} single-crystal substrates by dc facing-targets sputtering. Structural analysis and magnetic measurement were carried out. The results can be summarized as follows: (1) for the as-deposited (Fe100-xNix)-N films, α' phase with a stoichiometric N content of 11 at% can be formed up to x = 10; (2) the phase decomposition temperature Tp.d. of α'-(Fe100-xNix)16N2(x=0-10) depends strongly on the Ni content of the film. The Tp.d. of α'-(Fe100-xNix)16N2 decreases from about 200 °C(x=0) to about 50 °C(x=10) with increasing Ni content; (3) the formation at R.T. of stable α''-(Fe100-xNix)16N2(x=5-30) in the Fe-Ni alloy system is concluded to be difficult; and (4) judging from the dependence of the saturation magnetization for α'-(Fe100-xNix)16N2 on the Ni content, the saturation magnetization of α'-Fe16N2 is 220 emu/g.

Low‐Fired (Zn,Mg)TiO3 Microwave Dielectrics

A dielectric ceramic comprised of (Zn1‐xMgx)TiO3 (x= 0 to x= 0.5) with low sintering temperature and promising microwave properties was prepared by applying a semichemical synthesis route and a microbeads milling technique. X‐ray diffractometry and thermal analyses results indicated that the phase stability region of the hexagonal (Zn,Mg)TiO3 extended to higher temperatures as the amount of magnesium increased. The dielectric properties in this system exhibited a significant dependence on the sintering conditions, especially near the phase decomposition temperature. From 950°C, the temperature compensation characteristics occurred as the phase composition changed from hexagonal (Zn,Mg)TiO3 to two phases: (Zn,Mg)2TiO4 and rutile. The magnesium content for zero temperature coefficient (tauf) was ~3 mol% at 950°C; however, tauf increased with the sintering temperatures because of the shift of the decomposition temperature.

Glycine on Pt(111): a TDS and XPS study

The adsorption and desorption of in situ deposited glycine on Pt(111) were investigated with thermal desorption spectroscopy (TDS) and X-ray photoelectron spectroscopy (XPS). Glycine adsorbs intact on Pt(111) at all coverages at temperatures below 250 K. The collected results suggest that the glycine molecules adsorb predominantly in the zwitterionic state both in the first monolayer and in multilayers. Upon heating, intact molecules start to desorb from multilayers around 325 K. The second (and possibly third) layer(s) are somewhat more strongly bound than the subsequent layers. The multilayer desorption follows zero order kinetics with an activation energy of 0.87 eV molecule −1. From the first saturated monolayer approximately half of the molecules desorbs intact with a desorption peak at 360 K, while the other half dissociates before desorption. Below 0.25 monolayer all molecules dissociate upon heating. The dissociation reactions lead to H 2, CO 2, and H 2O desorption around 375 K and CO desorption around 450 K. This is well below the reported gas phase decomposition temperature of glycine, but well above the thermal desorption temperatures of the individual H 2, CO 2, and H 2O species on Pt(111), i.e. the dissociation is catalyzed by the surface and H 2, CO 2, and H 2O immediately desorb upon dissociation. For temperatures above 500 K the remaining residues of the dissociated molecules undergo a series of reactions leading to desorption of, for example, H 2CN, N 2 and C 2N 2, leaving only carbon left on the surface at 900 K. Comparison with previously reported studies of this system show substantial agreement but also distinct differences.

An experimental trial for the synthesis of α″-(Fe 100− xCo x) 16N 2 ( x = 0–30) martensite films by reactive sputtering

In order to determine the synthesis conditions of α″-(Fe 100− x Co x ) 16N 2, FeCo nitrided films were fabricated on MgO single-crystal substrates using reactive sputtering. The thermal stability of the α′ Fe Co phase was evaluated by measuring the temperature dependence of σ s. It was found that: (1) for the as-deposited (Fe 100− x Co x )-N films, α′ FeCo martensite phase with a stoichiometric N content of 11 at% can be formed up to x = 10, and with increasing x, α′ FeCo phase with stoichiometric N content is not formed. (2) The phase decomposition temperature, T pd, of α′-(Fe 100− x Co x )-N ( x = 0–30) phase depends strongly on the Co and N contents of the α′ FeCo phase. The T pd of α′ phase decreases from 200°C ( x = 0) to RT ( x = 30) with increasing Co and N contents. (3) The formation at RT of stable α″-(Fe 100− x Co x ) 16N 2 ( x = 10–30) phase in the FeCo alloy system is concluded to be fairly difficult.

Non-aqueous thermal decomposition route to colloidal inorganic oxides

Ceria, zirconia and zinc oxide have been successfully prepared by the thermal decomposition of the respective soluble cerium, zirconium and zinc salts in decan-1-ol, undecan-1-ol and ethane-1,2-diol. Only those metal salts whose (solid phase) decomposition temperature was less than or equal to the reflux temperature of the solvent were found to be effective. The growth rate of the oxides was found to be governed by the metal salt:solvent molar ratio and by the volume of solvent used in the preparation. This allowed the morphology of the primary oxide particles to be controlled: low molar ratios (ca. 0.01–0.02) and large volumes of solvent (allowing precise temperature control) afforded almost spherical, relatively monodisperse, colloidal particles; high molar ratios (ca 0.2), however, led to the formation of ill defined products reminiscent of oxides formed by aqueous phase precipitation, in accord with the principles of solution nucleation and particle growth. It was further observed that in the case of ceria, the precipitation rate governed the colour of the produced solids, indicating, it is suggested, that the molar ratio of cerium: oxygen varies according to the rate at which the oxide is formed.

A thermomechanical analysis study of selected compounds

The TG and DTA profiles of compounds such as calcium oxalate monohydrate and copper sulfate pentahydrate are well known. A TMA study of these and other compounds is presented which, in addition to providing interesting data on the physical nature of phase changes and decomposition temperature ranges, confirms the classification of TMA as a principal thermal analysis technique.

M�ssbauer and uv-visible spectroscopic study of the interaction of bis(toluene)iron(0) with surface hydroxyl groups of silica

Mossbauer and in-situ uv-visible spectroscopy to probe the interaction of toluene solutions of solvated iron atoms with silica gel having different concentrations of surface hydroxyl groups. Surface hydroxyl groups on sihca are found to facilitate the decomposition of bis(toluene)iron(0) well below its “normal” solution phase decomposition temperature of −30 °C. The silica supported iron clusters formed in this way are found to be finely divided crystallites of α-Fe2O3 with diameters less than 50 A.

Radiation cure of explosive/propellant formulations

Abstract The feasibility of radiation curing energetic compositions has been demonstrated. Binders consisting of vinyl-terminated polybutadieneacrylonitrile copolymer (VTBN) and a combination of styrene and 2-hydroxyethyl methacrylate have been cured using x-rays at a dose of 1.2 × 106 roentgen to give flexible, rubbery solid materials with rupture stress of 0.8 to 8.3 MPa and strain of 130–230 percent at 25°C. Irradiation of RDX (1,3,5-trinitro-l,3,5-triazacyclohexane) and HMX (1,3,5,7-tetranitro-l,3,5,7-tetrazacyclooctane) a t the 1.2 × 106 roentgen dose level caused no measurable ni tramine decomposition. The VTBN binder system loaded with 70% nitramine energetic filler was cured by irradiation (1.2 × 106 roentgen) t o give rubbery solids with 2.2–2.8 MPa stress a t rupture and nearly 100% strain (25°C). The filled systems display Taliani slopes, nitramine phase transitions and decomposition temperatures which are well within normal 1imits for explosives and propellants.