Enthalpies of Solution of Complexes of Rare Earth Nitrate with L-α-Histidine in Water

The enthalpies of solution in water of complexes of RE(NO 3) 3 (RE=La～Nd, Sm～Lu, Y) with L α Histidine (His) were measured at 298.15 K. The standard enthalpies of formation of RE(His) 3+ (aq) were calculated. The 'tetrad effect' regularity was observed from the curve, which is the enthalpies of solution plotted against the atomic numbers of the elements in lanthanide series.

Calculation on the Solid Solution Forming Enthalpies of Re-Mo-Ti Gradient Alloy in Thermodynamics

The idea about preparation of Re-Mo-Ti alloy is put forward because of applications of Re and Mo-Re alloys in aerospace.Basing on the thermodynamics theory,the feasibility of developing a new high temperature alloy Re-Mo-Ti is investigated.The solid solution forming enthalpies of binary alloys Re-Ti,Mo-Ti and Mo-Re are calculated with the Miedema thermodynamics theory.The Miedema theory of binary alloy can be used in ternary alloy through Kohler model or Toop model.The calculated results show that the forming enthalpies of binary alloys Re-Ti,Ti-Mo and Re-Mo are negative,which indicates that binary alloys Re-Ti,Ti-Mo and Re-Mo can form solid solution in wider component area.The forming enthalpies of Re-Mo-Ti ternary alloy are still negative and smaller than those of binary alloys Re-Ti,Ti-Mo or Re-Mo,which indicates it is possible to form large solid solution graph area among ternary alloys of Ti,Mo,Re elements.It is feasible to develop a new high temperature material in thermodynamics,in this material Re-Mo-Ti solid solution as base phase,and the Ti5Re24 intermetallic compounds or interphase ω (Ti4Mo3) as strengthening phase.

Thermochemical Properties and Non-isothermal Decomposi-tion Reaction Kinetics of N-Guanylurea Dinitramide (GUDN)

The constant-volume combustion energy, cUD(GUDN, s, 298.15 K), enthalpy of solution in acetic ether, solmHQD and kinetic behavior of the exothermic decomposition reaction of the title compound (GUDN) are deter-mined by a precise rotating bomb calorimeter, a Calvet microcalorimeter and DSC, respectively. Its standard en-thalpy of combustion, cmHQD (GUDN, s, 298.15 K), standard enthalpy of formation, fHQDm (GUDN, s, 298.15 K) and kinetic parameters of the exothermic main decomposition reaction in a temperature-programmed mode [the apparent activation energy (aE) and pre-exponential factor (A)] are calculated. The values of cUD (GUDN, s, 298.15 K), cmHQD (GUDN, s, 298.15 K), fmHQD(GUDN, s, 298.15 K) and solmHQD of GUDN are (-7068.64±2.37) J·g-1, (-1467.66±0.50) kJ·mol-1, (-319.76±0.58) kJ·mol-1 and (165.737±0.013) kJ·mol-1, respectively. The kinetic model function in integral form and the value of aEand A of the exothermic main decomposition reaction of GUDN are 220.20 kJ·mol-1 and 1021.18 s-1, respectively. The critical temperature of thermal explosion of GUDN is 217.6 ℃

Influence of electric field on the quenched-in vacancy and solute clustering during early stage ageing of Al-Cu alloy

The effects of electric field on the evolution of excess quenched-in vacancy as well as solute clustering in Al-4wt%Cu alloy, and on the vacancy migration and formation enthalpy of pure aluminum were investigated, using positron annihilation lifetime spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, transmission electron microscopy, hardness measurement and four-probe electrical resistivity measurement. The results showed that the electric field improved age hardening response obviously and postponed the decay of excess vacancies for 30rain during the early stage ageing of Al-4wt%Cu alloy. A large number of 2-4nm GP zones with dense distribution were observed after 1 min ageing with an electric field applied. The electric field-assisted-aged sample owned a lower coarsening rate of GP zone, which was about three fifths of that in the aged sample without an electric field, from 1 min to 120 rain ageing. The electric field contributed 8% increase of the vacancy migration enthalpy （0.663 ±0.021 eV） of pure Al, comparing with that （0.611 ±0.023 eV） of pure Al without an electric field. The increase of vacancy migration enthalpy, induced by the electric field, was responsible for the difference on evolution of quenched-in vacancy, rapid solute clustering and age hardening improvement during the early stage ageing of Al-4wt%Cu alloy.