Non-isothermal decomposition kinetics and lifetime of Tb2(0-MBA)6(PHEN)2

The thermal decomposition of Tb2(O-MBA)6(PHEN)2 (O-MBA: o-methylbenzoate; PHEN: 1,10-phenanthroline) and its kinetics were studied under the non-isothermal condition by thermogravimetry-derivative thermogravimetry (TG-DTG) techniques. Kinetic parameters were obtained from analysis of TG-DTG curves by the Achar method and the Madhusudanan-Krishnan-Ninan (MKN) method. The most probable mechanism function was suggested by comparing the kinetic parameters. The kinetic equation for the first stage can be expressed as dcddt = Aexp(-E/RT) 3(1 - α)2/3 The lifetime equation at mass loss of 10% was deduced as lnr= -28.7429 + 19797.795/Tby isothermal thermogravimetric analysis.     

Kinetics of isothermal reduction of stainless steelmaking dust pellets

The stainless steelmaking dust pellets were reduced in isothermal temperature condition simulating the direct recycling practice in the stainless steel production and the kinetics of the reduction process was investigated.The pellets were formed after mixing the dust with carbon as the reducing agent and dolomite as the binder and smelting flux. An electric furnace was used to heat the pellets and an electrical microbalance was used to check the mass of the pellets in the reduction process. The reduction rate was calculated according to the data of pellet mass change in consideration of the evaporation of moisture, zinc and lead at high temperature. The results of the experi-ments show that the reduction process is in two consecutive stages. The reduction kinetic models were set up for each stage and the kinetic parameters such as activation energy and frequency factor were determined. The apparent activation energy of the first stage is 21.69 kJ/mol, and this stage is controlled by chemical reaction. The apparentactivation energy of the second stage is 17.35 kJ/mol, and this stage is controlled by the diffusion of carbon monox-ide through the resultants of reaction.     

Adsorption of platinum (Ⅳ) onto D301R resin

Pt (Ⅳ) was quantitatively adsorbed by D301R resin in the medium of pH=3.47. The statically saturated adsorption capacity is 410 mg/g.Pt (Ⅳ) adsorbed on D301R resin can be eluted by 1.0-2.0 mol/L NaOH. The rate constant is k298=5.43×10-5s-1. The adsorption of Pt (Ⅳ) on D301R resin obeys the Freundlich isotherm. The adsorption parameters of thermodynamics are as follows: enthalpy change ΔH=4.37 kJ/mol, Gibbs free energy change ΔG=-5.39 kJ/mol, and entropy change ΔS=32.76 J/(mol.K). The apparent activation energy is Ea=22.5 kJ/mol. The coordination molar ratio of the functional group of D301R resin to Pt(Ⅳ) is 2:1.     

Crystallization kinetics and induced magnetic properties of bulk （Fe,Co）-Zr-Nd-B metallic glass

Crystallization kinetics and phase transformation of bulk Fe64 Co7 Zr6 Nd3B20 metallic glass were studied by X-ray diffractometry (XRD), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). Based on the Kissinger analyses, the activation energies for the nucleation and growth during the first, second and third crystallization-stages of the metallic glass are determined to be 294, 475 and 365 kJ/mol, respectively, and the activation energy for the glass transition is determined to be 1 242 kJ/mol. The Johnson-Mehl-Avrami (JMA) analysis under the isothermal condition reveals that the crystallization process is a three-dimensional controlled growth of nuclei at a constant nucleation rate. The crystalline grains are in the size of less than 50 nm after the selected annealing treatments. In the completely crystallized state, the alloy exhibits the maximum coercivity (Hc) of 34.8 kA/m and corresponding energy product of 11 kJ/m^3.     

Synthesis, characterization, and thermostability of bis（2,2,6,6-tetramethyl-3,5-heptanedionato）barium（II）

The metal-organic chemical vapor deposition (MOCVD) technique is a promising process for high-temperature superconductor YBa2 Cu3O7-δ(YBCO) preparation. In this technique, it is a challenge to obtain barium precursors with high volatility. In addition, the purity, evaporation characteristics, and thermostability of adopted precursors in whole process will decide the quality and reproducible results of YBCO film. In the present report, bis(2,2,6,6-tetramethyl-3,5-heptanedionato)barium(Ⅱ) (Ba(TMHD)2) was synthesized, and its structure was identified by FTIR, 1 H NMR, 13C NMR, and ESI-MS spectroscopy. Subsequently, the thermal properties and the kinetics of decomposition were systematically investigated by nonisothermal thermogravimetric analysis methods. Based on the average apparent activation energy evaluated by the Ozawa, Kissinger, and Friedman methods, the volatilization process was discussed, and all results show that Ba(TMHD)2 is unstable and highly sensitive to the change of temperature during the whole evaporation process. Therefore, it is very important to choose suitable volatilization technology and conditions for avoiding Ba(TMHD)2 break-down (or thermal aging) during MOCVD process. Subsequently, the possible conversion function is estimated through the Coats-Redfern method to characterize the evaporation patterns and follows a phase boundary reaction mechanism by the contracting surface equation with average activation energy of 118.7 kJ .mol-1.     

Adsorption of XSD-296 resin for Cr（Ⅵ）

The adsorption properties of XSD-296 for Cr（Ⅵ） were studied by using chemical analysis and infrared spectrometry. Experimental results show that XSD-296 resin has a good adsorption ability for Cr（Ⅵ） at pH=2.6 in the HAc-NaAc medium. The statically saturated adsorption capacity is 235 mg/g resin. The apparent activation energy of adsorption reaction, Ea, is 16.73 kJ/mol, and the thermodynamic parameters are △H=11.62 kJ/mol, △G298 K=-4.13 kJ/mol. The adsorption behavior of resin for Cr（Ⅵ） is in accordance with Freundlich adsorption isotherm. Cr（Ⅵ ） adsorbed on resin can be eluted by 5%NaCl-5%NaOH or 5%NH4Cl-5%NH3-H2O quantitatively. Infrared spectra and adsorption mechanism show that the functional group of resin coordinates with Cr（Ⅵ） to form co-ordination compound. The coordination molar ratio of the functional group of resin to Cr（Ⅵ） is 1：1.     

Catalytic performance and kinetics of Au/γ-Al_2O_3 catalysts for low-temperature combustion of light alcohols

Au/γ-Al2O3 catalysts were prepared by deposition-precipitation method for the catalytic combustion of low concentration alcohol streams(methanol,ethanol,iso-propanol and n-propanol).The catalysts were characterized by X-ray photoelectron spectroscopy(XPS),X-ray diffractometry(XRD) and energy dispersive X-ray micro analysis(EDS) techniques.The XPS results showed that there was only Au0 on the surface of catalysts.The XRD patterns showed that Au was presumably highly dispersed over γ-Al2O3.The temperatures for complete conversion of methanol,ethanol,iso-propanol and n-propanol with concentration of 2.0 g/m3 were 60,155,170 and 137 ℃,respectively,but they were completely mineralized into CO2 and H2O at 60,220,260 and 217 ℃ respectively over the optimized catalyst.The activity of the catalyst was stable in 130 h.The kinetics for the catalytic methanol elimination followed quasi-first order reaction expressed as r=0.652 8c0+0.084 2.The value of apparent activation energy is 54.7 kJ/mol in the range of reaction temperature.     

Removal of Co(Ⅱ) from aqueous solutions by NKC-9 strong acid resin

A strong acidic ion exchange resin(NKC-9)was used as a new adsorbent material for the removal of Co(Ⅱ)from aqueous solutions.The adsorption isotherm follows the Langmuir model.The maximum adsorption capacity of the resin for Co(Ⅱ)is evaluated to be 361.0 mg/g by the Langmuir model.It is found that 0.5 mol/L HCl solution provides effectiveness of the desorption of Co(Ⅱ)from the resin.The adsorption rate constants determined at 288,298 and 308 K are 7.12×10-5,8.51×10-5and 9.85×10-5s-1, respectively.The apparent activation energy(Ea)is 12.0 kJ/mol and the adsorption parameters of thermodynamic are-H Θ=16.1 kJ/mol,-SΘ=163.4 J/(mol·K),-G Θ 298 K=-32.6 kJ/mol,respectively.The adsorption of Co(Ⅱ)on the resin is found to be endothermic in nature.Column experiments show that it is possible to remove Co(Ⅱ)ions from aqueous medium dynamically by NKC-9 resin.     

Thermal stability of nanocrystalline in surface layer of magnesium alloy AZ91D

Isothermal and isochronal annealing was conducted to study the thermal stability of the nanocrystalline in the surface layer of Mg alloy AZ91D induced by high-energy shot peening(HESP) .Field emission scanning electron microscope(FESEM) and X-ray diffractometer were used to characterize the microstructure.Results showed that nanocrystalline produced by HESP on the surface layer of the magnesium alloy AZ91D was 60-70 nm on average.The nanocrystalline could remain stable at about 100℃,and grew up slowly between 100℃ and 200℃.When the annealing temperature reached 300℃,the growth rate of the nanocrystalline increased significantly.The kinetic coefficient n of the nanocrystalline growth was calculated to be 2-3 and the grain growth activation energy Q=39.7 kJ/mol,far less than the self-diffusion activation energy of magnesium atoms in the coarse polycrystalline material.     

Crystallinity and crystallization mechanism of lithium X-ray diffractometry aluminosilicate glass by

The crystallinity of lithium aluminosilicate（LAS） glass after crystallization were studied at different temperatures by X-ray diffractometry and the crystallinity of the standard glass ceramic with known crystal and glass phases was examined. The crystallization mechanism of LAS glass was analyzed by the crystallinity, with a formula relating the crystallinity （X） and temperature （T）. The results show that the calculated crystaUinity of LAS glass by XRD increases with the erystaUization temperature, in the range of 40%-50%, which is close to the calculated ones of standard samples with spodumene quartz ratio of 40%-70%. The activation energy of LAS glass is different within different temperature ranges; nEe is 125.44 kJ/mol at 710-810 ℃ and nEe is 17.42 kJ/mol at 810-980 ℃, which indicates different crystallization mechanisms. It has been proved that the required energy for crystallization of glass in the lower temperature range includes the interracial energy between glass and crystalline phase and the free energy difference of atoms in structures of glass and crystal, and in the higher temperature ranges only the interfacial energy between glass and crystalline phase is considered.     

Non-isothermal decomposition kinetics and lifetime ofTb2(O-MBA)6(PHEN)2

The thermal decomposition of Tb2(O-MBA)6(PHEN)2 (O-MBA: o-methylbenzoate; PHEN: 1,10-phenanthroline)and its kinetics were studied under the non-isothermal condition by thermogravimetry-derivafive thermogravimetry (TG-DTG) techniques. Kinetic parameters were obtained from analysis of TG-DTG curves by the Achar method and the Madhusudanan-Krishnan-Ninan (MKN) method. The most probable mechanism function was suggested by comparing the kinetic parameters. The kinetic equation for the first stage can be expressed as dα/dt = Aexp(-E/RT) @ 3(1 - α)2/3. The lifetime equation at mass loss of 10% was deduced as lnτ= -28.7429 + 19797.795/T by isothermal thermogravimetric analysis.     

Preparation and spectroscopic, and thermal decomposition kinetic studies of europium(Ⅲ) complex [Eu(HNBD)3] (HNBD: 1-(6-hydroxy-1-naphthyl)-1,3-butanedione)

The complex of Eu(Ⅲ) with 1-(6-hydroxy-1-naphthyl)-1,3-butanedione (HNBD) was prepared for the first time and characterized by elemental analysis, IR, UV, fluorescence spectrum, and DTA-TG-DTG techniques. The IR and UV-visible spectra showed that Eu(Ⅲ) ion was coordinated to the HNBD ligand. The fluorescence spectrum showed the presence of Eu3+ characteristic emission. The TG-DTA-DTG curves showed that the thermal decomposition of the anhydrous complex was a two-stage process and the final residue was Eu2O3. The thermal decomposition kinetic parameters of the complex were evaluated from TG-DTG data by using three kinds of integral methods (Coat-Redfern equation, Horowitz and Metzger equation, Madhusudanan-Krishnan-Ninan equation). The kinetic parameters of the first stage are E* = 164.02 kJ·mol-1, A = 1.31 × 1015 s-1, △S*= 42.27 J·K-1·mol-1, △H*= 159.51 kJ·mol-1, △G*= 136.54 kJ·mol-1, and n = 3.1, those of the second stage are E*= 128.52 kJ·mol-1, A = 1.44 × 106 s-1, △S*= - 136.89 J·K-1·mol-1,△H*= 120.41 kJ·mol-1, △G*=283.85 kJ·mol-1, and n = 1.1.     

Kinetics Study on the Thermal Decomposition of Europium p-methyl-benzoate Complex with 1,10-penanthroline under Non-isothermal Con-ditions

The special strUcture and iflteresting luminescent character of Eu(lll) complex made it veryimportant in applied researches as well as in theoretical Studies. The cryStal stricture and luminescence spectrum of europium p-methylbenzoate complex with l, 10-penanthroline were reported [l]. Its non-isothermal kinetics and thermal decomposition mechanism, however, hasrarely been studied. In the paped, the thermal decomposition behavior of europium p-methylbenzoate complex with l, 10-penanthroline…     

纳米TiO_2对钼(Ⅵ)的吸附性能

研究纳米TiO_2对Mo(VI)的吸附过程,考察溶液的pH值、时间、温度等因素对吸附的影响.结果表明:在pH 1～8范围内,纳米TiO_2对Mo(VI)的吸附率均超过99%,吸附于纳米TiO_2上的Mo(VI)可用2.0 mL的0.1 mol/L NaOH溶液定量洗脱;该吸附过程符合准二级反应动力学模型,其反应的表观活化能为22.7 kJ/mol,粒子内部扩散过程是其吸附控制步骤,但液相边界层向粒子表面的扩散过程不能忽略;吸附行为服从Langmuir和D-R等温模型.在室温下,纳米TiO_2对Mo(VI)的饱和吸附容量为12.74 mg/g,平均吸附能为17.36 kJ/mol;吸附反应焓变和熵变均为正值,自由能变为负值,说明该吸附过程为自发的吸热过程.     

Zr_(47)Cu_(44)Al_9大块非晶合金的变温晶化行为

利用示差扫描量热仪(DSC)研究了Zr_(47) Cu_(44)Al_9大块非晶合金在连续升温过程中的的变温晶化行为.利用Kissinger方法计算其特征温度表观激活能,利用Doyle方法计算其局域激活能.结果表明,Zr_(47) Cu_(44)Al_9大块非晶合金具有良好的热稳定性.利用Kissinger方法计算得到的其玻璃转变激活能E_g为390.2kJ/mol、晶化激活能E_x为325.1kJ/mol、晶化峰值的激活能E_p为299.5kJ/mol.随着加热速率的提高,各特征温度值向高温端移动,其晶化峰值温度所对应的晶化体积分数减小.局域激活能随着非晶晶化体积分数的增加而逐渐减小.     

Thermodynamic properties of LaCrO3

1. Introduction It is known that a lanthanum chromate with perovskite structure with high melting point and chemical stability [1] is a promising candidate base material for solid oxide fuel cells interconnects [2-3] and electrode materials [4]. In order to evaluate the chemical compatibility between a lanthanum chro- mate and other ceramic materials, it is necessary to study the thermodynamic properties of LaCrO3. Na- tsuko Sakai and Svein St?len [5] studied the heat capacity and thermodyna…     

Direct extraction of Mo(VI) from acidic leach solution of molybdenite ore by ion exchange resin: Batch and column adsorption studies

The adsorption behavior of ion exchange resin D301 in the extraction of hexavalent molybdenum from high acidic leach solution was investigated. SEM, EDS and Raman spectra analyses were applied to studying the adsorption capacity, reaction kinetics and possible adsorption mechanism in detail. Results showed that the adsorption capacity of D301 resin for molybdenum from high acidic leach solution was up to 463.63 mg/g. Results of the kinetic analysis indicated that the adsorption process was controlled by the particle diffusion with the activation energy 25.47 kJ/mol (0.9α1.2 mm) and 20.38 kJ/mol (0.6α0.9 mm). Furthermore, the molybdenum loaded on the resin could be eluted by using 2 mol/L ammonia hydroxide solution. Besides, dynamic continuous column experiments verified direct extraction of molybdenum from acidic leach solutions by ion exchange resin D301 and the upstream flow improved dynamic continuous absorption.     

Effects of rare-earth elements on the glass-forming ability and mechanical properties of Cu46Zr47-xAl7Mx (M = Ce, Pr, Tb, and Gd) bulk metallic glasses

Cu46Zr47-xAl7Mx(M = Ce,Pr,Tb,and Gd) bulk metallic glassy(BMG) alloys were prepared by copper-mold vacuum suction casting.The effects of rare-earth elements on the glass-forming ability(GFA),thermal stability,and mechanical properties of Cu46Zr47-xAl7Mx were investigated.The GFA of Cu46Zr47-xAl7Mx(M = Ce,Pr) alloys is dependent on the content of Ce and Pr,and the optimal content is 4.at %.Cu46Zr47-xAl7Tbx(x = 2,4,and 5) amorphous alloys with a diameter of 5 mm can be prepared.The GFA of Cu46Zr47-xAl7Gdx(x = 2,4,and 5) increases with increasing Gd.Tx and Tp of all decrease.Tg is dependent on the rare-earth element and its content.△Tx for most of these alloys decreases except the Cu46Zr42Al7Gd5 alloy.The activation energies △Eg,△Ex,and △Ep for the Cu46Zr42Al7Gd5 BMG alloy with Kissinger equations are 340.7,211.3,and 211.3 kJ/mol,respectively.These values with Ozawa equations are 334.8,210.3,and 210.3 kJ/mol,respectively.The Cu46Zr45Al7Tb2 alloy presents the highest microhardness,Hv 590,while the Cu46Zr43Al7Pr4 alloy presents the least,Hv 479.The compressive strength(σc.f.) of the Cu46Zr43Al7Gd4 BMG alloy is higher than that of the Cu46Zr43Al7Tb4 BMG alloy.     

Adsorption behavior of Pd(Ⅱ) from aqueous solutions by D201 resin

The adsorption and desorption behaviors of Pd(Ⅱ) on D201 resin were investigated. The effects of parameters including HCl concentrations, initial metal ion concentrations, contact time, and temperature on the adsorption of Pd(Ⅱ) were studied by batch method. The HCl concentration for studying the effects was set from 0.01 to 2 mol·L-1 and the optimal adsorption condition is in 0.01 mol·L-1 HCl solution. The adsorption isotherm of Pd(Ⅱ) on D201 resin was determined and the equilibrium data fitted the Langmui...