Estimation of Time to Maximum Rate Under Adiabatic Conditions(TMR_(ad)) Using Kinetic Parameters Derived From DSC-Investigation of Thermal Behavior of 3-Methyl-4-Nitrophenol

Kinetic parameters of the decomposition of hazardous chemicals can be applied for the estimation of their thermal behavior under any temperature profile.Presented paper describes the application of the advanced kinetic approach for the determination of the thermal behavior also under adiabatic conditions occurring e.g.in batch reactors in case of cooling failure.The kinetics of the decomposition of different samples(different manufacturers and batches) of 3-methyl-4-nitrophenol were investigated by conventional DSC in non-isothermal(few heating rates varying from 0.25 to 8.0K/min) and isothermal(range of 200~260℃) modes.The kinetic parameters obtained with AKTS-Thermokinetics Software were applied for calculating reaction rate and progress under different heating rates and temperatures and verified by comparing simulated and experimental signals.After application of the heat balance to compare the amount of heat generated during reaction and its removal from the system,the knowledge of reaction rate at any temperature profiles allowed the determination of the temperature increase due to the self-heating in adiabatic and pseudo-adiabatic conditions.Applied advanced kinetic approach allowed simulation the course of the Heat-Wait-Search(HWS) mode of operation of adiabatic calorimeters.The thermal safety diagram depicting dependence of Time to Maximum Rate(TMR) on the initial temperature was calculated and compared with the results of HWS experiments carried out in the system with Ф-factor amounting to 3.2.The influence of the Ф-factor and reaction progress reached at the end of the HWS monitoring on the TMR is discussed.Presented calculations clearly indicate that even very minor reaction progress reduces the TMRad of 24h characteristic for a sample with initial reaction progress amounting to zero.Described estimation method can be verified by just one HWS-ARC,or by one correctly chosen ISO-ARC run of reasonable duration by knowing in advance the dependence of the TMR on the initial temperature for any Ф-factor.Proposed procedure results in significant shortening of the measuring time compared to a safety hazard approach based on series of ARC experiments carried out at the beginning of a process safety evaluation.

Thermal Behavior, Specific Heat Capacity and Adiabatic Time-to-explosion of GDN

A new compound, [（NH2）2C=NH2]＋N（NO2）2-（GDN）, was prepared by mixing ammonium dinitramide （ADN） and guanidine hydrochloride in water. The thermal behavior of GDN was studied under the non-isothermal conditions with DSC and TG/DTG methods. The apparent activation energy（E） and pre-exponential constant（A） of the exothermic decomposition stage of GDN were 118.75 kJ/mol and 10^10.86 s^-1, respectively. The critical temperature of the thermal explosion（Tb） of GDN was 164.09 ℃. The specific heat capacity of GDN was determined with the Micro-DSC method and the theoretical calculation method, and the standard molar specific heat capacity was 234.76 J·mol^-1·K^-1 at 298.15 K. The adiabatic time-to-explosion of GDN was also calculated to be a certain value between 404.80 and 454.95 s.

Estimation of the kinetic parameters for thermal decomposition of HNIW and its adiabatic time-to-explosion by Kooij formula

A differential/integral method to estimate the kinetic parameters(apparent activation energy Eaand pre-exponential factor A) for thermal decomposition reaction of energetic materials based on Kooij formula are applied to study the nonisothermal decomposition reaction kinetics of hexanitrohexaazaisowurtzitane(HNIW) by analyzing nonisothermal DSC curve data. The apparent activation energy(Ea) obtained by the integral isoconversional non-isothermal method based on Kooij formula is used to check the constancy and validity of apparent activation energy by the differential/integral method based on Kooij formula. The most probable mechanism function of thermal decomposition reaction of HNIW is determined by a logical choice method. The equations for calculating the critical temperatures of thermal explosion(Tb) and adiabatic time-toexplosion(tTIad) based on Kooij formula are used to calculate the values of Tband tTIadto evaluate the thermal safety and heat-resistant ability of HNIW. All the original data needed for analyzing the kinetic parameters are from nonisothermal DSC curves. The results show that the kinetic model function in differential form and the values of Eaand A of decomposition reaction of HNIW are 3(1 a)[ ln(1 a)]2/3, 152.73 kJ mol 1and 1011.97s 1, respectively, and the values of self-accelerating decomposition temperature(TSADT), Tband tTIadare 486.55 K, 493.11 K and52.01 s, respectively.

Dynamic Mechanical Behavior and Adiabatic Shear Bands of Ultrafine Grained Pure Zirconium

Dynamic compression tests were carried out to investigate dynamic mechanical behavior and adiabatic shear bands in ultrafine grained(UFG)pure zirconium prepared by equal channel angular pressing(ECAP)and rotary swaying.The cylindrical specimens were deformed dynamically on the split Hopkinson pressure bar(SHPB)at different strain rates of 800 to 4000s^-1 at room temperature.The temperature distribution of the shear bands was estimated on the basis of temperature rise of uniform plastic deformation stage and thermal diffusion effect.The results show that the true stress-true strain curves of UFG pure zirconium are concave upward trend of strain in range of 0.02-0.16 due to the effects of strain hardening,strain rate hardening and thermal softening.The formation of the adiabatic shear bands is the main reason of UFG pure zirconium failure.A large number of micro-voids are observed in the adiabatic shear bands,and the macroscopic cracks develop from the micro-voids coalescence.The fracture surface of UFG pure zirconium exhibits quasi cleavage fracture with the characteristic features of shear dimples and river pattern.The highest temperature within the shear bands of UFG pure zirconium is about 592 K.

Thermal characteristic evolution of lithium-ion batteries during the whole lifecycle

This work extensively investigates the thermal characteristic evolution of lithium-ion batteries under different degradation paths,and the evolution mechanism through multi-angle characterization is revealed.Under different degradation paths,the evolution trend of temperature rise rate remains unchanged with respect to depth of discharge during the adiabatic discharge process,albeit to varying degrees of alteration.The temperature rise rate changes significantly with aging during the adiabatic discharge process under low-temperature cycling and high-rate cycling paths.The total heat generation rate,irreversible heat generation rate,and reversible heat generation rate exhibit similar evolution behavior with aging under different degradation paths.The interval range of endothermic process of reversible electrochemical reactions increases and the contribution of irreversible heat to the total heat increases with aging.To further standardize the assessment of different degradation paths on the thermal characteristics,this work introduces the innovative concept of“Ampere-hour temperature rise”.In low-temperature cycling and high-rate cycling paths,the ampere-hour temperature rise increases significantly with aging,particularly accentuated with higher discharge rates.Conversely,in high-temperature cycling and high-temperature storage paths,the ampere-hour temperature rise remains relatively stable during the initial stages of aging,yet undergoes a notable increase in the later stages of aging.The multi-angle characterization reveals distinct thermal evolution behavior under different degradation paths primarily attributed to different behavior changes of severe side reactions,such as lithium plating.The findings provide crucial insights for the safe utilization and management of lithium–ion batteries throughout the whole lifecycle.

Effect of CO_(2) dilution on laminar burning velocities,combustion characteristics and NO_(x) emissions of CH_(4)/air mixtures

The laminar combustion characteristics of CH_(4)/air premixed flames with CO_(2) addition are systemically studied.Experimental measurements and numerical simulations of the laminar burning velocity(LBV)are performed in CH_(4)/CO_(2)/Air flames with various CO_(2) doping ratio under equivalence ratios of 1.0–1.4.GRI 3.0 mech and Aramco mech are employed for predicting LBV,adiabatic flame temperature(AFT),important intermediate radicals(CH_(3),H,OH,O)and NO_(x) emissions(NO,NO_(2),N2O),as well as the sensitivity analysis is also conducted.The detail analysis of experiment and simulation reveals that as the CO_(2) addition increases from 0%to 40%,the LBVs and AFTs decrease monotonously.Under the same CO_(2) doping ratio,the LBVs and AFTs increase first and then decrease with the increase of equivalence ratio,and the maximum of LBV is reached at equivalence ratio of 1.05.The mole fraction tendency of important intermediates and NO_(x) with equivalence ratio and CO_(2) doping ratio are similar to the LBVs and AFTs.Reaction H+O_(2)⇔O+OH is found to be responsible for the promotion of the generation of important intermediates and NO_(x) under the equivalence ratios and CO_(2) addition through sensitivity analysis.The sensitivity coefficients of elementary reactions that the increasing of CO_(2) doping ratio promotes or inhibits formation of intermediate radicals and NO_(x) decreases.

Structural Characterization and Thermal Properties of 1-Amino-1- ethylamino-2,2-dinitroethylene

1-amino-1-ethylamino-2,2-dinitroethylene （AEFOX-7） was synthesized by the reaction of 1,1- diamino-2,2-dinitroethylene （FOX-7） and ethylamine aqueous solution at 92 ℃. The the- oretical investigation on AEFOX-7 was carried out by B3LYP/6-311＋＋G^＊＊ method. The IR frequencies and NMR chemical shifts were performed and compared with the experimental results. The thermal behavior of AEFOX-7 was studied with differential scanning calorimetry and thermal gravity-derivative thermogravimetry methods, and can be divided into a melting process and an exothermic decomposition process. The enthalpy, apparent activation energy and pre-exponential factor of the exothermic decomposition reaction were obtained as 374.88 kJ/mol, 169.7 kJ/mol, and 10^19.24 s^-1, respectively. The critical temperature of thermal explosion of AEFOX-7 is 145.2 ℃. The specific heat capacity of AEFOX-7 was determined with micro-DSC method and theoretical calculation method, and the molar heat capacity is 214.50 J/（mol K） at 298.15 K. The adiabatic time-to-explosion of AEFOX-7 was calculated to be a certain value between 1.38-1.40 s. The thermal stability of AEFOX-7 is much lower than that of FOX-7.

锂离子动力电池充放电热跟踪系统设计

为实现18650锂离子电池在室温下以1 C倍率充放电时产热测量的绝热环境,设计一种基于电池温度与环境温度跟随策略的锂离子动力电池充放电热跟踪系统,采用硅胶加热片对绝热温控腔体进行加热,STM32单片机和LM2596电源管理芯片搭建可调节电源实现驱动。利用Matlab对绝热箱温控系统进行模型辨识,提出一种Smith预估模糊PID算法进行控制。仿真与实验结果表明:绝热箱内电池温度与环境温度的最大跟踪误差不超过0.5℃,具有响应速度快、误差小等优点,能够满足18650锂离子电池在室温下以1 C倍率充放电时产热测量的需求。

基于热功率的焊接热输入分配及稀释率预测

【目的】热输入Q_(HI)仅简单描述了焊接能量的来源与大小,没有阐明焊缝与母材吸收的热量如何分配的不足。【方法】该文利用基于填充金属量提出的热功率PPR概念,通过焊缝尺寸测量,JmatPro与公式计算等手段,实现了焊接热输入分配及稀释率进行的预测。【结果】基于P_(PR)可实现对熔化母材面积A_(mb)的预测,其曲线变化可分为渐增区、快增区、缓增区3个阶段。结合JmatPro计算的材料体积比热容与A_(mb)预测公式,可将不同PPR下的有效焊接热输入Q_(e)进行细分,发现在可焊区形成焊缝的热输入只占其31.77%~34.69%。【结论】提出了基于P_(PR)的焊缝面积百分比稀释率δ预测公式,并给出可焊区的焊接热功率为12.69~47.88 kW/cm^(2),稀释率为48.28%~85.03%。

钨合金杆侵彻过程中的塑性流动及热软化行为

针对钨合金杆穿甲侵彻过程中的塑性变形流动及热软化机制,对高速侵彻嵌入装甲钢中的残余弹体进行微细观组织观测,利用LS-DYNA动力学软件对钨合金杆侵彻装甲钢过程中的温度分布特性进行了数值模拟,并基于MJC本构模型讨论了热软化参数对钨合金杆侵彻性能的影响。结果表明,侵彻过程中弹靶接触区域巨大的冲击压力造成钨晶粒被严重压扁,塑性变形功转化为热量使钨晶粒发生热软化并沿径向流动形成蘑菇头。绝热剪切主要沿蘑菇头飞檐处形成并演化为层片状失效脱落。钨合金弹芯材料的热软化行为对侵彻过程中的塑性流动及侵彻效率有重要影响,当热软化行为表现为低温敏感性时,弹芯蘑菇头塑性影响区厚度降低,弹尾存速增加,从而提高侵彻效率。

磷灰石ID-TIMS高精度U-Pb定年方法

磷灰石晶体结构呈六方晶系,具有相对高的封闭温度(350~550℃),能够容纳多种元素置换进入晶格内部,是火成岩、沉积岩、变质岩和矿床研究的重要定年矿物。然而,由于磷灰石通常具有较低铀含量和高普通铅含量,精准测定其年龄仍是当前U-Pb测年技术的一大挑战。本文基于^(208)Pb-^(235)U混合稀释剂,通过优化样品清洗、溶解以及柱色谱分离纯化U和Pb等化学前处理流程,建立了磷灰石同位素稀释-热电离质谱(ID-TIMS)高精度U-Pb定年方法,并准确测定了磷灰石标样MAD2和MAP-3的年龄,其^(206)Pb/^(238)U年龄加权平均值分别为474.6±1.7Ma和800.7±1.2Ma,单点定年精度优于0.4%,为磷灰石微区原位标样研发以及样品年龄精准测定提供技术支撑。采用MAP-3作为微区原位校正标样,对磷灰石Durango和Otter Lake进行LA-ICP-MS U-Pb测年分析,通过Tera-Wasserburg谐和图图解法扣除普通铅,获得下交点年龄分别为32.1±0.6Ma(MSWD=1.3,n=36)和910±13Ma(MSWD=1.6,n=36),与前人研究结果在误差范围内一致,进一步证实普通铅含量极低的MAP-3,是一个理想的磷灰石微区原位测年标样。与高普通铅的磷灰石标样相比,使用MAP-3作为外标能直接在数据处理软件中进行数据校正,有效地简化了数据处理过程,提高磷灰石微区原位U-Pb测年结果的可靠性。

Evaluation of Thermal Hazard of Composite Modified Double-base Propellant by Microcalorimetery Method

The thermal decomposition behavior of composite modified double-base（CMDB） propellant containing cyclotrimethylene trinitramine（RDX） was studied via a Calvet microcalorimeter at five different heating rates. The activation energy（E） and the pre-exponential factor（A） of two obvious exothermic processes were obtained by Kissinger＇s method and Ozawa＇s method. The entropy of activation（△S^≠）, the enthalpy of activation（△H^≠）, and the free energy of activation（△G^≠） of the first stage were calculated. To evaluate the thermal hazard of the RDX-CMDB propellant, the critical temperature of thermal explosion（Tb）, the self acceleration decomposition temperature（Tsgox）, the adiabatic decomposition temperature increment（ATad） and the time-to-explosion of adiabatic system（t） were presented as 145.3 ℃, 138.15 ℃, 1634 K and 583.71 s（n=0） and 586.28 s（n=1）, respectively.

不同热加工工艺下花椒主要苦味物质的鉴定

花椒作为重要的香辛料,其苦味成分的存在对食品的整体风味具有显著影响。为了深入探究花椒苦味成分的形成机制及其影响因素,本研究以苦味强度为指标,利用感官评价对花椒在水煮和油炸时的工艺条件进行单因素优化。进一步地,通过有机溶剂萃取、固相萃取和制备型高效液相色谱技术,从花椒水和花椒油中分离并富集了苦味馏分。随后,利用滋味稀释分析评估了这些苦味馏分对食品感官特性的贡献。此外,采用高效液相色谱-质谱联用技术,对花椒水和花椒油中的苦味成分进行了成分鉴定。研究结果表明,在水煮过程中,花椒用量的增加和水煮时间的延长会增强苦味,而花椒的苦味在油炸过程中会随着温度升高、时间延长和用量增加而增强。推荐花椒水和花椒油的食用、加工条件如下:花椒水推荐在100℃下煮制5 min,花椒用量控制在2 g以下,以减少苦味。而花椒油建议在105~120℃的油炸温度下炸制10~30 min,花椒用量可适量添加,以保持较低苦味。花椒水中主要的苦味物质可能是槲皮素-3-鼠李糖龙胆二糖苷、槲皮素-3,7-二-O-β-D-吡喃葡萄糖苷、槲皮素-3-O-槐糖和荷叶碱,而花椒油中主要的苦味物质是羟基-α-山椒素和羟基-β-山椒素。本研究为花椒的加工利用、品质调控以及除苦抑苦等提供数据参考和理论依据。

六亚甲基二异氰酸酯与丙烯酸羟乙酯反应动力学及热动力学研究

研究了六亚甲基二异氰酸酯(HDI)与丙烯酸羟乙酯(HEA)在聚氨酯合成反应中的动力学和热动力学特征。在反应动力学方面,采用甲苯-二正丁胺滴定法获取了反应转化率数据,分别构建了二级动力学模型和Sato动力学模型来拟合实验数据。结果表明:该反应符合Van't Hoff近似规则;低转化率时,二级动力学模型拟合效果较好;而在高转化率时,由于存在自催化作用,Sato动力学模型具有更好的拟合优势;在热动力学方面,使用绝热加速量热仪(ARC)对反应放热进行了表征分析,结果显示该反应的热动力学反应级数为0.8,表观活化能为57.51 kJ/mol。该研究为聚氨酯的安全、高效和绿色合成提供了科学理论依据。

基于头峰的多步分解反应过程热失控特征参数计算方法研究

目前微通道反应器在含能材料合成领域广泛应用,极大提高了合成过程的安全性,但是仍然需要关注物料的热稳定性。绝热条件下最大反应速率到达时间(TMR_(ad))与TMR_(ad)为24 h所对应的引发温度(T_(D24))是两个表征危险化学品及含能材料热分解危险性的重要特征参数,这两个参数的传统计算方法为单步N级法和数值计算法,存在分析过程费时费力的缺点。为此,根据差示扫描量热仪动态升温测试曲线,提出了基于头峰(即多峰曲线分峰后的第一个峰)的热分解失控特征参数计算方法,采用穷举法比较了该方法与模型计算法的T_(D24)偏差,进行了数值模拟验证,并基于文献实验计算了1,8-二硝基蒽醌、改性硝基胍(M-NQ)、1,5-二硝基蒽醌和3,4-二硝基呋咱基氧化呋咱(DNTF)4种物质的热失控特征参数。数值模拟结果表明,对于两步和三步连续反应,T_(D24)的最大偏差百分比分别为2.88%和6.9%,最大偏差为6.41℃;对于三步连续反应,T_(D24)最大偏差为5.39℃。结果表明,4种含能材料的T_(D24)计算偏差分别为-4.55,0.71,3.16℃和-0.84℃,与模型计算法得到的T_(D24)相比,偏差百分比的绝对值均小于2%,证实了T_(D24)计算方法的有效性,计算T_(D24)时偏差较小,计算简便,能够较为准确地获得其热分解失控特征参数。

聚苯乙烯合成工艺热危险性研究

为了研究聚苯乙烯合成工艺聚合反应的热危险性,利用反应量热仪(RC1mx)研究聚合反应过程的热效应;利用绝热加速量热仪(ARC)测试聚合反应前后混合物料的绝热分解特性,并开展动力学研究。RC1mx实验结果表明,聚合反应总放热量为82.612 kJ,绝热温升ΔT_(ad)为152.6℃,最高合成反应温度为252.6℃,技术最高温度为146℃。ARC实验结果表明,聚合反应混合物料的绝热过程分为2个阶段:第1阶段放热在62~118℃,绝热温升为56℃;第2阶段放热在118~145℃,绝热温升为27℃。根据ARC实验第1阶段绝热分解动力学分析,得到表观活化能为120.55 kJ/mol,指前因子A为36.5 min^(-1),求得失控反应最大反应速率时间。根据RC1mx和ARC实验结果对聚苯乙烯合成工艺聚合反应进行了热危险性评估。

Thermal stability assessment of anti-explosive ammonium nitrate

The explosivity experiment of anti-explosive ammonium nitrate (AEAN) shows that the explosive characteristic of AEAN is eliminated. The adiabatic decompositions of ammonium nitrate and AEAN were investigated with an accelerating rate calorimeter (ARC). The curves of thermal decomposition temperature and pressure versus time, self-heating rate and pressure versus temperature for two systems were obtained. The kinetic parameters such as apparent activation energy and pre-exponential factor were calculated. The safety of AEAN was analyzed. It was indicated that AEAN has a higher thermal stability than AN. At the same time, it can be shown that the elimination of its explosive characteristic is due to the improvement on the thermal stability of AEAN.

典型二元硝基化合物的热危险性分析

文章选择了2,4-二硝基苯胺、2,6-二硝基苯胺和1,4-二硝基苯3种典型的二元硝基化合物作为实验对象,通过差示扫描量热实验(DSC)、热重实验(TG/DTG)和绝热加速量热实验(ARC)分析了3种物质的分解过程,获取了热危险性数据和动力学参数。结果表明,3种物质的分解过程均可分为三个阶段,即能量缓慢释放阶段、能量积聚阶段和能量爆发阶段,在物质储运过程中需要严格控制温度,防止物质进入能量爆发阶段;3种物质的危险性程度由高到低依次为2,4-二硝基苯胺、2,6-二硝基苯胺、1,4-二硝基苯。

软包型高能量密度三元锂离子电池热失控特性研究

为充分认识软包型高能量密度三元锂离子电池发生热失控的条件和后果,采用电池绝热量热仪分别考察了不同类型镍钴锰三元软包锂离子电池的热失控反应特性,得到了不同能量密度电池的热失控起始放热温度、热失控触发温度、绝热温升、达到最大反应速率时间等热安全参数的变化规律,讨论了软包型高能量密度锂离子电池发生热失控的条件和机理,提出了表征电池热失控危险特性的安全判据。高能量密度软包型锂离子电池最低在50℃左右即可发生自反应放热,120~180℃时发生不可逆热失控,该过程产生大量气体导致鼓包、破裂,电池材料燃烧后最高温度可达600℃。研究得到的电池关键量热参数和规律能够为动力电池及储能系统的风险评估、监测预警和安全防护等提供基础数据和理论依据。

Effect of dilution gas composition on the evolution of graphite electrode characteristics in the spark gap switch

As the widely implemented electrode material,graphite has the characteristic of sublimation by the thermal shock of the switching arc,and the produced carbon vapor is easy to condense into carbon powders and deposit in the switch.The impact of the type of dilution gas in a mixture of20%oxygen and 80%dilution gas on the sublimation and oxidation characteristics of the graphite electrode is investigated.It is found that when nitrogen dilution gas was replaced by argon,the heat flux to the electrodes decreased,which led to a 63%reduction of graphite sublimation.At the same time,the cooling rate of the arc was slower in argon,which promotes oxidation of the carbon vapor.The residual solid carbon can be reduced by 70%–85%by using argon as the dilution gas.Consequently,it is demonstrated that the stability and working life of the switch could be increased by appropriate selection of the dilution gas.