首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 109 毫秒
1.
《Thermochimica Acta》1987,112(2):275-287
The thermal investigations of metal carboxylato complexes of the first transition metals, Mn(II), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) and non transition metals like Zn(II) and Cd(II) in solid state were carried out under non-isothermal condition in nitrogen atmopshere by thermogravimetric (TG) and differential thermal analyses (DTA) methods. The results of DTA curves inferred that the thermal stability of the complex decreased approximately with the increase of standard potential of the central metal ion. The thermal parameters like activation energy (Ea1), enthalpy change (ΔH) and entropy change (ΔS) corresponding to deaquation, deammoniation and decomposition processes occurred simultaneously or separately were determined from TG and DTA curves by the standard methods. A linear correlation has been found in the plots of ΔH vs. ΔS and Ea1 vs. ΔS in deaquation, deammoniation and decomposition processes. An irreversible phase transition was noticed for H2[Mn(suc)2] and H2[Co(suc)2] complexes in DTA curves. The residual pyrolysed products were metal carbonates.  相似文献   

2.
2,2,2-三硝基乙基-N-硝基甲胺的热安全性   总被引:1,自引:0,他引:1  
为评价2,2,2-三硝基乙基-N-硝基甲胺(TNMA)的热安全性, 得到计算TNMA热安全性参数用的基本数据, 用经验式估算了TNMA的比热容(Cp)和热导率(λ). 用键能贡献于生成热Qf的加和法, 估算了TNMA的标准生成焓ΔcHmθ(TNMA, s, 298.15 K). 用热力学公式计算了TNMA的标准燃烧焓ΔUmθ(TNMA, s, 298.15 K)和标准燃烧能ΔcHmθ(TNMA, s, 298.15 K). 用Kamlet-Jacobs 公式估算了爆速、爆压和爆热. 用经验式估算了分解热(Qd). 通过差示扫描量热(DSC)曲线和高灵敏度布鲁顿玻璃薄膜压力计测得的逸出气体标准体积(VH)-时间(t)曲线, 得到了TNMA放热分解反应的动力学参数. 用上述基本数据得到了评价TNMA的热安全性参数: 自加速分解温度(TSADT), 热爆炸临界温度(Tbe0和Tbp0), 绝热至爆时间(tTIad), 撞击感度50%落高(H50), 热点起爆临界温度(Tcr), 被300 K环境包围的半厚和半径为1 m的无限大平板、无限长圆柱和球形TNMA的热感度概率密度函数S(T), 相应于S(T)-T关系曲线最大值的峰温(TS(T)max), 安全度(SD), 临界热爆炸环境温度(Tacr)和热爆炸概率(PTE). 结果表明: (1) TNMA有较好的热安全性和对热抵抗能力, 与环三亚甲基三硝胺(RDX)相比, TNMA易从热分解过渡到热爆炸; (2) 不同形状大药量TNMA 热安全性降低的次序为: 球>无限长圆柱>无限大平板; (3)TNMA有高的燃烧能、高的爆轰化学能(爆热)和接近环四亚甲基四硝胺(HMX)的爆炸性能, 其对冲击敏感, 冲击感度与季戊四醇四硝酸酯(PETN)和特屈尔接近, 可用作混合炸药主组分.  相似文献   

3.
《Tetrahedron》2019,75(36):130494
We have examined enantioselective bioreduction of acetophenone and its substituted derivatives into corresponding S-alcohols catalyzed by Daucus carota and Petroselinum crispum plant cells in water and isooctane. We found that the nature of the substituent has a profound effect on the relative reactivity of substituted acetophenones and enantioselectivity of biocatalytic reduction. Electron-withdrawing substituents –Br and –NO2 enhance the initial rate of reaction and yields of products, while electron-donating substituent –OCH3 decreases them. The reduction rates and yields of products in water were noticeably higher in comparison with similar reductions conducted in isooctane. Correlations between the initial reaction rate and the substituent constant (σ+) in the aromatic ring characterizing its nature were established. Comparison of ρ constants of bioreduction catalyzed by D. carota and P. crispum shows that the sensitivity of the reduction to the nature of the substituents is more significant in the case of D. carota biocatalyst. Comparison of ρ constants for D. сarota and P. crispum in water and isooctane indicates that the sensitivity of bioreduction to the nature of the substituent tends to increase from water to isooctane.  相似文献   

4.
When reaction mixtures of rare earth(III) sulphates and tetramethylammonium sulphate in molar ratios of from 1∶4 to 1∶12 were evaporated at ambient temperature and the concentrated reaction mixture was treated with ethanol, double sulphates with general empirical formula (CH3)4NLn(SO4)2·2H2O (Ln=Ho?Lu and Y) were obtained as reaction products. The crystalline products were identified by quantitative analysis, X-ray powder diffraction patterns and TG, DTG and DTA analysis. They were found to be isostructural. Their thermal decomposition took place in three stages. The temperature range of the dehydration mainly decreased from Ho to Lu. The thermal decomposition in the second and third stages occurred with many thermal events. As final product, Ln2O(SO4)2 was obtained.  相似文献   

5.
The thermal decomposition of nitrocellulose (NC) 12.1% N, has been studied with regard to kinetics, mechanism, morphology and the gaseous products thereof, using thermogravimetry (TG), differential thermal analysis (DTA), IR spectroscopy, differential scanning calorimetry (DSC) and hot stage microscopy. The kinetics of the initial stage of thermolysis ofNC in condensed state has been investigated by isothermal high temperature infrared spectroscopy (IR). The decomposition ofNC in KBr matrix in the temperature range of 142–151°C shows rapid decrease in O?NO2 band intensity, suggesting that the decomposition of NC occurs by the rupture of O?NO2 bond. The energy of activation for this process has been determined with the help of Avrami-Erofe'ev equation (n=1) and is ≈188.35 kJ·mol?1. Further, the IR spectra of the decomposition products in the initial stage of thermal decomposition ofNC, indicates the presence of mainly NO2 gas and aldehyde.  相似文献   

6.
《Thermochimica Acta》1987,109(2):331-342
Thermal investigation of metal carboxylato complexes of the first transition metals, Mn(II), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) and non-transition metals like Zn(II) and Cd(II) in the solid state has been carried out under non-isothermal conditions in nitrogen atmosphere by simultaneous TG and DTA. TG and DTA curves inferred that the thermal stability of the complex decreased approximately with the increase of the standard potential of the central metal ion. The thermal parameters like activation energy, Ea, enthalpy change, ΔH, and entropy change, ΔS, corresponding to the dehydration and decomposition of the complexes are determined from TG and DTA curves by standard methods. A linear correlation is found between ΔH and ΔS and Ea and ΔS in dehydration and decomposition processes. DTA curves show an irreversible phase transition for Na2Mn(mal)2], Na2[Cu(mal)2] and Na2,[Co(suc)2] complexes. The residual products in these decomposition processes being a mixture of two oxides, of oxide and carbonate or a mixture of two carbonates.  相似文献   

7.
The non-isothermal decomposition of anhydrous disilver malonate was studied up to 300°C by means of TG, DTA and DSC techniques in different atmospheres (e.g. N2, H2 and air). Acetic acid, CO2, acetone and CO were identified as the volatile decomposition products using gas chromatography. Silver metal, on the other hand, was identified as the final solid product using X-ray powder diffraction. The mechanism described involves the breakdown of adsorbed radicals, probably including-CH2COO- and related species, on the surface of the metallic silver product. The activation energy (ΔE) and the frequency factor (InA) were calculated for the decomposition process from the variation of peak temperature (of the DTA curves) with the rate of heating (φ). The enthalpy change (ΔH), the heat capacity (C p) and entropy change (ΔS) were calculated from the DSC measurements.  相似文献   

8.
A novel complex [Ni(H2O)4(TO)2](NO3)2·2H2O (TO = 1,2,4-triazole-5-one) was synthesized and structurally characterized by X-ray crystal diffraction analysis. The decomposition reaction kinetic of the complex was studied using TG-DTG. A multiple heating rate method was utilized to determine the apparent activation energy (E a) and pre-exponential constant (A) of the former two decomposition stages, and the values are 109.2 kJ mol?1, 1013.80 s?1; 108.0 kJ mol?1, 1023.23 s?1, respectively. The critical temperature of thermal explosion, the entropy of activation (ΔS ), enthalpy of activation (ΔH ) and the free energy of activation (ΔG ) of the initial two decomposition stages of the complex were also calculated. The standard enthalpy of formation of the new complex was determined as being ?1464.55 ± 1.70 kJ mol?1 by a rotating-bomb calorimeter.  相似文献   

9.
Although the reaction products are unstable at the reaction temperatures, at a heating rate of 2 deg·min?1 ammonium peroxo vanadate, (NH4)4V2O11, decomposes to (NH4)[VO (O2)2 (NH3)] (above 93°C); this in turn decomposes to (NH4) [VO3 (NH3)] (above 106°C) and then to ammonium metavanadate (above 145°C). On further heating vanadium pentoxide is formed above 320°C. The first decomposition reaction occurs in a single step and the Avrami-Erofeev equation withn=2 fits the decomposition data best. An activation energy of 148.8 kJ·mol?1 and a ln(A) value of 42.2 are calculated for this reaction by the isothermal analysis method. An average value of 144 kJ·mol?1 is calculated for the first decomposition reaction using the dynamic heating data and the transformation-degree dependence of temperature at different heating rates.  相似文献   

10.
The non-isothermal decomposition of cobalt acetate tetrahydrate was studied up to 500°C by means of TG, DTG, DTA and DSC techniques in different atmospheres of N2, H2 and in air. The complete course of the decomposition is described on the basis of six thermal events. Two intermediate compounds (i.e. acetyl cobalt acetate and cobalt acetate hydroxide) were found to participate in the decomposition reaction. IR spectroscopy, mass spectrometry and X-ray diffraction analysis were used to identify the solid products of calcination at different temperatures and in different atmospheres. CoO was identified as the final solid product in N2, and Co3O4 was produced in air. A hydrogen atmosphere, on the other hand, produces cobalt metal. Scanning electron microscopy was used to investigate the solid decomposition products at different stages of the reaction. Identification of the volatile gaseous products (in nitrogen and in oxygen) was performed using gas chromatography. The main products were: acetone, acetic acid, CO2 and acetaldehyde. The proportions of these products varied with the decomposition temperature and the prevailing atmosphere. Kinetic parameters (e.g.E and lnA) together with thermodynamic functions (e.g. °H, C p and °S) were calculated for the different decomposition steps. In celebration of the 60th birthday of Dr. Andrew K. Galwey  相似文献   

11.
Four new complex compounds were prepared by reaction of zinc carboxylate and methyl-3-pyridyl carbamate. The synthesized complex compounds of the general formula (RCOO)2ZnL2 (RCOO-= HCOO- (form), CH3COO- (ac), CH3CH2CH2COO- (but), (CH3)2CHCOO- (isobut), L= methyl-3-pyridyl carbamate (mpc)) were characterized by chemical analysis, IR spectroscopy and studied by methods of thermal analysis (TG/DTG, DTA). CH2O, CO2, (CH3)2CO, (C3H7)2CO were found as volatile products of thermal decomposition. ZnO was found as final product of thermal decomposition of the prepared complexes heated up to 700°C. Mass spectroscopy, X-ray powder diffraction method, IR spectra and chemical analysis were used for the determination of the thermal decomposition products. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

12.
A relationship between local structure, thermal stability and electrical conductivity (σ) of xR2O·10Fe2O3·(90 ? x)V2O5 glasses (abbreviated as xRFV glasses, where R = Li, Na, K; x = 20 and 40 in mol %) was investigated by 57Fe-Mössbauer spectroscopy, X-ray diffractometry, differential thermal analysis (DTA) and DC two- and four-probe method. From DTA study, thermal stability of 20RFV glasses is lower than that of 40RFV glasses by evaluating Hruby parameter (K gl). Constant activation energy for crystallization (E a) of 2.5 eV obtained from both 20RFV and 40RFV glasses indicate that the crystallization proceeds with the cleavage of Fe–O bond having the energy of 2.6 eV. Isochronally annealed 20RFV glass at 400–450 °C resulted in the increase in electrical conductivity (σ) from the order of 10?3 to 10?1 S cm?1, whereas slight decrease in σ was observed for 20RFV glass annealed above 460 °C. A paramagnetic doublet with an identical isomer shift (δ) of 0.39 mm s?1 was observed in the 57Fe-Mössbauer spectra of 20RFV glass after isothermal annealing conducted at 400–450 °C for 100 min, which caused a decrease of quadruple splitting (Δ) from 0.67 to 0.52 mm s?1 for 20LiFV glass and from 0.66 to 0.53 mm s?1 for 20NaFV glass. On the other hand, three paramagnetic doublets with δ and Δ of 0.40 and 0.25, 0.38 and 0.60, and 0.31 and 1.11 mm s?1 respectively were observed for 20RFV glass annealed at 460–550 °C, reflecting precipitation of semiconducting FeVO4 phase having σ of 6.0 × 10?7 S cm?1. It can be concluded that isochronal annealing of 20RFV glass below 450 °C resulted in increase in σ due to the structural relaxation, while annealing above 500 °C resulted in the decrease of σ due to the precipitation of FeVO4 phase.  相似文献   

13.
The reaction between thiobenzoyl chloride S oxide 4, (R = C6H5) and the azide ion at -80° leads to the labile thiobenzoyl azide S-oxide 5, (R = C6H5) Raising the temperature to -40° initiates decomposition of the latter to benzomtrile, nitrogen, sulfur and sulfur dioxide The thermally induced process was monitored by differential thermal analysis (DTA) which yielded a maximum heat effect at -11° The derived reaction enthalpy is ΔH=?45.6 kcal mole?1 and the activation parameters are ΔH = 20.2 kcal mol?1 ΔS = 6.3 eu (at ?11°). The DTA shape index (S) and the reaction type index (M) are found to be in excellent agreement with a rate controlling first order reaction. Apart from the main peak at -11°, lack of a temperature difference signal throughout the range of measurement rules out an enthalpy-significant azide isomenzation and further suggests that decomposition takes place from a single isomer. Semi-empirical energy barrier calculations provide a rationale for the single conformer interpretation. The data are consistent either with a reaction in which N2 and SO are expelled simultaneously or with the formation of a short-lived intermediate arising from N2 loss which rapidly eliminates sulfur monoxide. Intermediate formation of thiatriazole S-oxide cannot, however, be ruled out unambiguously.Since thioazides cyclize readily to thiatriazoles, whereas thioazide S oxides are not observed to cyclize, MO calculations have been carried out for the ring closures 2→3 and 5→6 (R= H) Orbital correlation diagrams for each potential energy surface show that ring formation is “allowed” in both cases. It is suggested that the variable chemical behavior of thioazides and their S-oxides is due to disruption of aromatic character in the hypothetical thiatriazole S-oxide product.  相似文献   

14.
Non-isothermal studies of some adduct molecules of metallic halides with tetrahydropyran as the type MX2(THP)y in solid state, were carried out with a Derivatograph, where M  Mn(II), Co(II), Ni(II), Cu(II) or Cd(II), XCl- or Br-, THPtetrahydropyran and y0.1–1. These adduct molecules lost tetrahydropyran in single or multiple steps upon heating. Thermally stable intermediate products were isolated and characterised by elemental analysis and IR spectral measurement. The activation energy for each step of decomposition of the adduct was evaluated from the analysis of TG, DTG and DTA curves of the respective derivatogram. The enthalpy change was evaluated from the DTA peak area and the order of reaction was found to be unity, for each step of decomposition. Thermal parameters for the above adducts were compared with the adducts of other oxocompounds like dioxan, tetrahydrofuran, ethylene glycol dimethyl ether and diisopropyl ether.  相似文献   

15.
The high nitrogen compound 3,6-bis(1H-1,2,3,4-tetrazol-5-yl-amino)-1,2,4,5-tetrazine and the high energy density material hexanitrohexaazaisowurtzitane (HNIW), were used as substitute of hexogen (RDX) in the composite modified double base (CMDB) propellant formulations, the propellant samples were prepared, the thermal behaviors, nonisothermal reaction kinetics, and thermal safety were carried out, and the eight important parameters were calculated and obtained as the self-accelerating decomposition temperature (T SADT), thermal ignition temperature (T TIT), critical temperatures of thermal explosion (T b), critical temperature of hot-spot initiation (T cr,hot-spot), characteristic drop height of impact sensitivity (H 50), critical thermal explosion ambient temperature (T acr), safety degree (S d), and thermal explosion probability (P TE). It shows that the content of HNIW has a large effect on the decomposition reaction mechanism of the CMDB propellant, when the content of HNIW is 10 %, the decomposition reaction are controlled by the random nucleation and subsequent growth (n = l), and the reaction mechanism obeys Mampel law; but when the content of HNIW is 20 %, the decomposition reaction are controlled by the chemical reaction (n = 1/4). The mechanism can not be changed by the catalysts, and they just make the apparent activation energy change slightly. For the sample, from BC01 to BC04, the values of T SADT and T TIT making an upward tendency, show the resistivity to heat: BC04 > BC03 > BC02 > BC01; the values of T acr and S d, BC01 are the maximum and BC02 are the minimum, show the heat sensitivity: BC01 > BC03 > BC04 > BC02. For the same radius, the thermal safety of the sphere sample is greater than that of the infinite cylinder one.  相似文献   

16.
The synthesis and photoconductivity properties of the alkylthia and triethyleneoxysulfonyl substituted oxotitanium(IV) phthalocyanines (1a and 2a) are reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, electronic spectroscopy and mass spectroscopy. The mesogenic properties of these new materials were studied by differential scanning calorimetry and optical microscopy. The electrical dark conductivities (σd) and photoconductivities (σph) of deposited films of 1a and 2a were investigated in various media with different concentrations of oxygen. Molecular oxygen increases photoconductivities (σph) significantly. The photoconductivity mechanism and formation of Pc+ which is positive charge carrier under the light irradiation of the phthalocyanine molecules are demonstrated using the theoretical calculations. The geometries of the oxotitanium(IV) phthalocyanines (TiOPc) are optimized with PM3 semi-empirical method, and their visible absorption maxima are calculated with ZINDO/S method. The results agree well with the observed values. It was found that for the calculation of visible absorption of neutral and positively charged substituted TiOPc molecules using ZINDO/S method could rapidly yield excellent results. Dipole moment, HOMO, LUMO energies and atomic charges are also calculated for clarification of the oxygen effect on the photoconductivity using PM3 and ZINDO/S methods.  相似文献   

17.
The non-isothermal decompositions of silver maleate dihydrate (C4H2O4Ag22H2O) and anhydrous silver fumarate (C4H2O4Ag2) were studied up to 500°C, in a dynamic atmosphere of air, by means of TG and DTA measurements. Both compounds showed some sublimation (at 120°C for silver maleate and at 180°C for silver fumarate) prior to the onset of decomposition (at 170°C for silver maleate and at 280°C for silver fumarate). The gaseous decomposition products of both compounds were found, using IR spectroscopy, to be dominated by maleic anhydride and CO2. Minor proportions of ethylene, ethyl alcohol, acetone, methane and isobutene were also identified. Metallic silver was the final solid product, as identified by X-ray diffractometry. NMR analysis was used to monitor the isomerization of the maleate radical into the more stable fumarate above 230°C. Kinetic parameters (E a and lnA) were calculated from the effect of heating rate, (2, 5, 10, and 20 deg min?1) on the DTA measurements. A mechanism is suggested for the decomposition pathways of these compounds, on basis of the results obtained and, also, on similarities with analogous systems.  相似文献   

18.
The expressions to calculate the critical rate of temperature rise of thermal explosion $ ({\text{d}}T / {\text{d}}t)_{{\text{T}_{\text{b}} }} $ for energetic materials (EMs) were derived from the Semenov’s thermal explosion theory and autocatalytic reaction rate equation of nth order, CnB, Bna, first-order, apparent empiric-order, simple first-order, Au, apparent empiric-order of m = 0, n = 0, p = 1 and m = 0, n = 1, p = 1, using reasonable hypotheses. A method to determine the kinetic parameters in the autocatalytic-decomposing reaction rate equations and the $ ({\text{d}}T / {\text{d}}t)_{{\text{T}_{\text{b}} }} $ in EMs when autocatalytic decomposition converts into thermal explosion from data of DSC curves at different heating rate was presented. Results show that (1) under non-isothermal DSC conditions, the autocatalytic-decomposing reaction of NC (12.97 % N) can be described by the first-order autocatalytic reaction rate equation dα/dt = 1016.00exp(?174520/RT)(1 ? α) + 1016.00exp(?163510/RT)α(1 ? α); (2) the value of $ ({\text{d}}T / {\text{d}}t)_{{\text{T}_{\text{b}} }} $ for NC (12.97 % N) when autocatalytic decomposition converts into thermal explosion is 0.354 K s?1.  相似文献   

19.
1,2‐Diorganylsubstituted derivatives of hydrazinium azide were examined in order to investigate their higher volatility and higher sensitivity to initiation compared to 1,1‐diorganylsubstituted hydrazinium azide derivatives. The compounds were synthesized from the respective hydrazines by reaction with HN3 and characterized by elemental analysis, vibrational (IR, Raman) and multinuclear NMR spectroscopy (1H, 13C, 14N). Their sensitivity to friction, shock, electrostatic impact and heat was examined and the explosion products were investigated. The crystal structure of pyrazolidinium azide was determined.  相似文献   

20.
为应用热爆炸临界温升速率(dT/dt)Tb评价含能材料(EMs)的热安全性, 得到计算(dT/dt)Tb值的基本数据, 用合理的假设, 由Semenov的热爆炸理论和9 个自催化反应速率方程[dα/dt=Aexp(-E/RT)α(1-α) (I), dα/dt=Aexp(-E/RT)(1-α)n(1+Kcatα) (II), dα/dt=Aexp(-E/RT)[αa-(1-α)n)] (III), dα/dt=A1exp(-Ea1/RT)(1-α)+A2exp(-Ea2/RT)α(1-α) (IV), dα/dt=A1exp(-Ea1/RT)(1-α)m+A2exp(-Ea2/RT)αn(1-α)p (V), dα/dt=Aexp(-E/RT)(1-α) (VI), dα/dt=Aexp(-E/RT)(1-α)n (VII), dα/dt=A1exp(-Ea1/RT)+A2exp(-Ea2/RT)(1-α) (VII), dα/dt=A1exp(-Ea1/RT)+A2exp(-Ea2/RT)α(1-α) (IX)]导出了计算(dT/dt)Tb值的9 个表达式. 提出了从不同恒速升温速率(β)条件下的差示扫描量热(DSC)曲线数据计算/确定EMs自催化分解反应的动力学参数和自催化分解转向热爆炸时的(dT/dt)Tb的方法. 由DSC曲线数据的分析得到了用于计算(dT/dt)Tb值的β→0 时的onset 温度(Te0),热爆炸临界温度(Tb)和相应于Tb时的转化率(αb). 分别用线性最小二乘法和信赖域方法得到方程(I)和(VI)及方程(II)-(V)和方程(VII)-(IX)中的自催化分解反应动力学参数. 用上述基础数据得到了EMs的(dT/dt)Tb值. 结果表明: (1) 在非等温DSC条件下硝化棉(NC, 13.54% N)分解反应可用表观经验级数自催化反应速率方程dα/dt=1015.82exp(-170020/RT)(1-α)1.11+1015.82exp(-157140/RT)α1.51(1-α)2.51描述; (2) NC (13.54% N)自催化分解转向热爆炸时的(dT/dt)Tb值为0.103 K·s-1.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号