Ag-rich phase precipitation in the Cu-9 mass% Al alloy with Ag additions

The Ag-rich phase precipitation in the Cu-9 mass% Al was studied using differential scanning calorimetry (DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The results indicated that Ag additions did not interfere on the metastable transitions sequence of the Cu-mass% Al alloy but Ag precipitation disturbs the β phase formation reaction and the martensitic phase decomposition reaction.     

Thermokinetic parameters and thermal hazard evaluation for three organic peroxides by DSC and TAM III

The thermokinetic parameters were investigated for cumene hydroperoxide (CHP), di-tert-butyl peroxide (DTBP), and tert-butyl peroxybenzoate (TBPB) by non-isothermal kinetic model and isothermal kinetic model by differential scanning calorimetry (DSC) and thermal activity monitor III (TAM III), respectively. The objective was to investigate the activation energy (E _a) of CHP, DTBP, and TBPB applied non-isothermal well-known kinetic equation to evaluate the thermokinetic parameters by DSC. We employed TAM III to assess the thermokinetic parameters of three liquid organic peroxides, obtained thermal runaway data, and then used the Arrhenius plot to obtain the E _a of liquid organic peroxides at various isothermal temperatures. In contrast, the results of non-isothermal kinetic algorithm and isothermal kinetic algorithm were acquired from a highly accurate procedure for receiving information on thermal decomposition characteristics and reaction hazard.     

The use of DSC in describing the structure evolution of an AlZnMg alloy

Summary The potential of DSC in suggesting modifications of thermal treatments of Al alloys to increase mechanical properties is described. Significant results can be obtained from calorimetric evolution after a series of annealings, even without a direct observation of the microstructure. The role of a reference baseline is discussed. The Guinier-Preston (GP) zones formation, dissolution or transformation is followed, and their relevance for the microhardness increase is shown, for an AlZnMg alloy of technical interest. Multi-stage thermal treatments have been confirmed to be beneficial. A secondary precipitation occurs at room temperature after annealing at temperatures at which primary precipitation is almost complete.     

The long and short of it: the influence of N-carboxyethyl versusN-carboxymethyl pendant arms on in vitro and in vivo behavior of copper complexes of cross-bridged tetraamine macrocycles

A cross-bridged cyclam ligand bearing two N-carboxymethyl pendant arms (1) has been found to form a copper(II) complex that exhibits significantly improved biological behavior in recent research towards (64)Cu-based radiopharmaceuticals. Both the kinetic inertness and resistance to reduction of Cu-1 are believed to be relevant to its enhanced performance. To explore the influence of pendant arm length on these properties, new cross-bridged cyclam and cyclen ligands with longer N-carboxyethyl pendant arms, 2 and 4, and their respective copper(II) complexes have been synthesized. Both mono- as well as di-O-protonated forms of Cu-2 have also been isolated and structurally characterized. The spectral and structural properties of Cu-2 and Cu-4, their kinetic inertness in 5 M HCl, and electrochemical behavior have been obtained and compared to those of their N-carboxymethyl-armed homologs, Cu-1 and Cu-3. Only the cyclam-based Cu-1 and Cu-2 showed unusually high kinetic inertness towards acid decomplexation. While both of these complexes also exhibited quasi-reversible Cu(II)/Cu(I) reductions, Cu-2 is easier to reduce by a substantial margin of +400 mV, bringing it within the realm of physiological reductants. Similarly, of the cyclen-based complexes, Cu-4 is also easier to reduce than Cu-3 though both reductions are irreversible. Biodistribution studies of (64)Cu-labeled 2 and 4 were performed in Sprague Dawley rats. Despite comparable acid inertness to their shorter-armed congeners, both longer-armed ligand complexes have poorer bio-clearance properties. This inferior in vivo behavior may be a consequence of their higher reduction potentials.     

Thermal Decomposition Kinetics of Lead 2,4,6-Trinitroresorcinate Monohydrate

IntroductionLead 2 ,4,6- trinitroresorcinate monohydrate,Pb( TNR)· H2 O,has good detonating propertiesand is sensitive to flame.It can be used as initiat-ing agent,igniter powder or delay powder.Itspreparation,properties,crystal structure[1] andthermal behavior[2 ] have been reported.In the pre-sent paper,we will report its kinetic parametersand mechanism of thermal decomposition reactionstudied with TG- DTA,IR and DSC.This is quiteuseful in the evaluation of its thermal stability un-d…     

Non-isothermal short-range-ordering by excess vacancies in αCu−Zn alloys

The kinetics short-range-order (SRO) in quenched Cu-30 at.% Zn, Cu-25 at. %Zn and Cu-20 at. %Zn was investigated by differential scanning calorimetry (DSC). It was evidenced a growing atomic mobility with increasing Zn content. From the DSC traces it is inferred that ordering is established in one stage, assisted by excess vacancies. As the quenching temperature increases considerable reordering occurs during cooling from the quenching temperature. The variation in the SRO non-isothermal behaviour with quenching temperature and composition is interpreted in terms of the atomic mobility and the degree of disorder together with the concentration of vacancies retained by quenching. Activation energies which control the mean life of vacancies and those which control the ordering rate were very similar, indicating that the mobility of vacancies is highly effective in generating SRO. Such activation energies are somewhat lower than the effective energies which control the kinetics of the process obtained from the DSC traces, suggesting that the presence of solute-vacancy complexes may be important as the Zn concentration increases. This feature was confirmed by an estimation of the solute-vacancy binding energy. It was also inferred that divacancy formation is unlikely in the alloys under study.     

2，4，6-三硝基间苯二酚钡一水化合物的热分解动力学(英)

0IntroductionBarium2,4,6鄄trinitroresorecinatemonohydrate,Ba(TNR)·H2O,hasgooddetonatingpropertiesandissensitivetoflame.Itcanbeusedasinitiatingagent,igniterpowderordelaypowder.Itspreparation[1],pro鄄perties[1],crystalstructure[1]andthermalbehavior[2]haveb…     

3,7-二硝基亚氨基-2,4-二氮杂双环[3,3,0]辛烷的放热分解反应动力学

The kinetic parameters of the exothermic decomposition reaction of the title compound in a temperature-programmed mode have been studied by means of DSC. The DSC data obtained are fitted to the integral, differential and exothermic rate equations by linear least-squares, iterative, combined dichotomous and least-squares methods, respectively. After establishing the most probable general expression of differential and integral mechanism functions by the logical choice method, the corresponding values of the apparent activation energy (Ea), pre-exponential factor (A) and reaction order (n) will be obtained by the exothermic rate equation. The results show that the empirical kinetic model function in differential form and the values of Ea and A of this reaction are (1-α)0.44, 230.4 kJ/mol and 1018.16 s-1, respectively. With the help of the heating rate and obtained kinelic parameters, the kinetic equation of the exothermic decomposition reaction process of the title compound is proposed. The critical temperature of thermal explosion of the compound is 302.6℃. The above-mentioned kinetic parameters are quite useful for analyzing and evaluating the stability and thermal change rule of the title compound.     

非等温法研究TGDDM/DDS体系固化反应动力学

采用DSC对4,4′-四缩水甘油基二氨基二苯基甲烷(TGDDM)和3,3′-二氨基二苯基砜(DDS)体系的固化反应动力学进行了研究.分别通过n级反应法和Malek的最大概然机理函数法确定了固化反应机理函数,求解了固化反应动力学参数,得到了固化反应动力学模型.结果表明,通过Kissinger,Crane方法求解动力学参数所得到的n级反应模型与实验值差别较大;而采用Malek方法判别机理,表明该固化反应按照自催化反应机理进行,实验得到的DSC曲线与模型计算所得到的曲线吻合的较好,所确立的模型在5~20K/min的升温速率下能较好地描述TGDDM/DDS体系的固化反应过程,并为工艺参数的选择和工艺窗口的优化提供了理论依据.     

The simulation of the thermal behavior of energetic materials based on DSC and HFC signals

Two small calibre and four medium calibre types of propellants were investigated non-isothermally (0.25–4K min⁻¹) by differential scanning calorimetry (DSC) in the range of RT-260°C and isothermally (60–100°C) by heat flow calorimetry (HFC). The data obtained from both techniques were used for the calculation and comparison of the kinetic parameters of the decomposition process. The application of HFC allowed to determine the kinetic parameters of the very early stage of the reaction (reaction progress α below 0.02) what, in turn, made possible the precise prediction of the reaction progress under temperature mode corresponding to real atmospheric changes according to STANAG 2895. In addition, the kinetic parameters obtained from DSC data enabled determination of self-accelerating decomposition temperature (SADT) and comparison of the predicted ignition temperature during slow cook-off with the experimental results. The study contains also the results of the calculation of the time to maximum rate (TMR_ad) of the propellants under adiabatic conditions.     

Study of Copper Chloride Coordination with L-α-Histidine

Thermochemical and kinetic equations for nonequilibrium reactions that occur at constant pressure and temperature were proposed. Thermodynamic and kinetic characteristics of copper(II) reaction with histidine (His) were obtained. The enthalpy of formation of copper(II) complex with histidine at temperatures from 298.15 to 323.15 K was determined by microcalorimetry. The standard enthalpy of formation of Cu(His)₂ ^{2 +}(aq) was calculated. The enthalpy, entropy, and Gibbs energy of activation, rate constants, activation energies, preexponential factor, and reaction order were obtained on the basis of experimental and calculated data. The resulting data suggest that the title reaction readily proceeds at the indicated temperatures. The Cu(His)₂Cl₂·H₂O complex was isolated in the solid state and characterized by IR spectroscopy and thermal analysis.     

Thermokinetic analysis of two-step curing reactions in melt: Part I. Investigation of low molecular model systems

Kinetic investigations of thermo-controlled two-step reactions between an uretdione cross-linker and OH-groups are undertaken. Non-isothermal DSC measurements are chosen for the determination of the kinetic parameters (E, A, n) using of THERMOKINETICS software. The system can be described very accurately with a four-step kinetic model of consecutive reactions. On the basis of the kinetic model and parameters the realization of the first reaction step, which is the formation of the allophanate network is simulated. Finally, the result of the calculated progress of the reaction is evaluated by FT-IR and isothermal DSC measurements.     

(NBR/PVC)/CuSO_4复合材料中配位交联反应的研究

采用差示扫描量热法(DSC)和傅立叶转换红外光谱(FT-IR)对丁腈橡胶/聚氯乙烯合金/无水硫酸铜((NBR/PVC)/CuSO4)混合物的配位交联反应进行了研究.结果表明,(NBR/PVC)/CuSO4共混物在升温过程中出现两个放热峰,分别归因于腈基(—CN)和CuSO4之间的配位交联反应和体系中NBR/PVC的自交联反应.通过对共混物配位交联反应动力学参数的计算发现,混合物中CuSO4含量的多少并未对体系配位交联反应的进行产生影响.同时共混物中PVC的存在促进了配位交联反应的进行,降低了铜离子(Cu2+)与—CN之间配位交联反应的表观活化能Ea.     

Energetic and Kinetic Evaluations Conducted in a Quasi-Binary Cu−1 at% Co2Si Alloy Through DSC

By means of differential scanning calorimetry (DSC) the precipitation process from a supersaturated solid solution of Cu−0.65 at% Co−0.33 at% Si (Cu−1 at% Co2Si) was investigated. On the basis of enthalpimetric calculations it was found that the decomposition begins with cobalt precipitation. Clustering of atoms of cobalt initiates the precipitation of silicon, and particles of the stoichiometric Co2Si composition are finally formed. Kinetic parameters were obtained by a convolution method based on the Mehl–Johnson–Avramiformalism. Their values are all in agreement with the experimentally observed behavior displayed by DSC traces. Decay kinetics of cobalt and silicon matrix during simulated isothermal calculations using DSC data reveals good agreement with similar computed results reported in literature. Precipitate dissolution obeys quite well to a three-dimensional diffusion kinetic law previously developed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Influence of Ag addition on the thermal behavior of the Cu-11 mass% Al alloy

In this work the influence of Ag additions on the thermal behavior of the Cu-11 mass% Al alloy was studied using differential scanning calorimetry, in situ X-ray diffractometry and scanning electron microscopy. The results indicated that changes in the heating rate shift the peak attributed to α phase formation to higher temperatures, evidencing the diffusive character of this reaction. The activation energy value for the α phase formation reaction, obtained from a non-isotherm kinetic model, is close to that corresponding to Cu atoms self diffusion, thus confirming that this reaction is dominated by Cu atoms diffusion through the martensite matrix.     

Kinetics and Mechanism of the Reaction of Carbon Tetrachloride with Copper in Dimethylacetamide

The reaction of copper with carbon tetrachloride in dimethylacetamide was studied. In the absence of atmospheric oxygen, the oxidative dissolution of copper occurred by the mechanism of single-electron transfer with the formation of C₂Cl₆ and copper(I) complexes. The kinetic and thermodynamic parameters of the reaction were found. The reaction mechanism is discussed.     

Kinetics and mechanism of the reaction of benzyl bromide with copper in dimethylacetamide in the presence of oxygen

The reaction of copper metal with benzyl bromide in dimethylacetamide in the presence of oxygen has been studied. Oxidative dissolution of copper follows the single-electron transfer mechanism with formation of benzaldehyde, benzyl alcohols, and copper(II) coordination compounds. The kinetic and thermodynamic parameters of the process have been determined by resistometry. Intermediately formed species have been identified and quantitated, and the reaction stereochemistry has been studied. The reaction mechanism is discussed.     

Metal‐complex formation and DNA interaction of 5, 10,15,20‐tetrakis(1‐methyl‐4‐pyridiyl)‐porphine: Study of the mechanistic aspects

The macrocyclic porphyrin 5,10,15,20‐tetrakis(1‐methyl‐4‐pyridiyl)‐porphine is studied in its ability to coordinate Cu(II) even at very low pH values and to interact, as a copper complex, with calf‐thymus (CT‐DNA). The kinetics and equilibria for metal‐ligand complexes formation are spectrophotometrically studied, particularly focussing on the mechanistic information provided by the kinetic approach. The rate constants of complex formation is much lower than that of water exchange at Cu(II); this behavior is ascribed to an equilibrium between two porphyrin populations, only one of them being reactive. Concerning the interaction of the copper–porphyrin complex (D) with CT‐DNA, it has been found that the complex binds to G–C base pairs by intercalation while forms external complex with the A–T base pairs. The kinetic results agree with a reaction mechanism that takes into account the slow shuffling from an AT‐bound form (DAT) to a GC‐bound form (DGC) of the copper complex (D), finally leading to a more stable DGC* intercalated form. Kinetic and equilibrium parameters for the copper complex binding to the nucleic acid are obtained, and the binding mechanism is discussed. A mechanism is proposed where D reacts simultaneously with (G–C) and (A–T) base pairs. The resulting bound forms interconvert according to a “shuffling” process, which involves formation of an intermediate (DGC) form. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 79–89, 2010     

DSC examination of alloys

The formation and thermal dissolution of dispersed particles was studied in aluminium alloys. It was found that only high heating rates (80°C min⁻¹) could provide DSC curves characteristic of the phase structure of the samples. The kinetic evaluation of the DSC curves was carried out by least squares curve fitting. In this way reasonable kinetic parameters and reliable peak resolution could be obtained for the overlapping peaks.