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apparent activation energy of Concrete in Early Age Determined by Adiabatic Test

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Journal of Wuhan University of Technology(Materials Science) 2007年第3期22卷 537-541页

作者：王甲春阎培渝 Department of Civil Engineering Nanjing University of Aeronautics and Astronautics

The apparent activation energy of concrete in early age was determined by adiabatic temperature rise test with different initial temperatures. The influence of mineral admixtures such as fly ash, slag and silica fume on the apparent activation energy of concrete was investigated. The equivalent age that expresses the maturity of concrete was calculated to evaluate the cracking risk of concrete in structures. The results reveal that a substitution of 20% fly ash for Portland cement obviously decreases the apparent activation energy of concrete, however, a substitution of 10% silica fume for Portland cement increases the apparent activation. Finite element method analysis of a simulating concrete wall shows that the concrete containing 20% fly ash has the lowest cracking risk.

关键词： mineral admixtures apparent activation energy equivalent age cracking risk

Determination of the apparent activation energy of Concrete Carbonation

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Journal of Wuhan University of Technology(Materials Science) 2013年第5期28卷 944-949页

作者：李果 YUAN Yingshu DU Jianmin JI Yongsheng Jiangsu Key Laboratory of Environmental Impact and Structural Safety in Engineering China University of Mining & Technology

Accelerated carbonation experiments about the development of carbonation rates of ordinary Portland cement concrete under different artificial climates were carried out. Six water cement ratios and six climate condition combinations of temperature and relative humidity were used. Results indicate that changes of concrete carbonation rate with environmental temperature agree the Arrhenius law well, which suggests concrete carbonation rate has obvious dependence on temperature. The higher the temperature is, the more quickly the concrete carbonates, and at the same time it is also affected by environmental relative humidity. Thereafter, the apparent activation energy Ea of concrete carbonation reaction was obtained, ranging from 16.8 to 20.6 kJ/mol corresponding 0.35-0.74 water cement ratio, and lower water cement ratio will cause the apparent activation energy increase. Concrete carbonation rates will increase 1.1-1.69 times as temperature increase every 10 ℃ at the temperature range of 10 to 60 ℃.

关键词： concrete carbonation rate apparent activation energy temperature

Calculation of apparent activation energy of Coal Oxidation at Low Temperatures by Measuring CO Yield

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International Journal of Mining Science and Technology 2006年第1期16卷 37-41页

作者： QI Feng,LI Zeng-hua,PAN Shang-kun,ZHANG Lin School of Mining and Safety Engineering, China University of Mining & Technology, Xuzhou, Jiangsu 221008, China School of Mining and Safety Engineering China University of Mining & Technology Xuzhou Jiangsu 221008 China

By analyzing previous studies on activation energy of coal oxidation at low temperatures, a theoretical cal- culation model of apparent activation energy is established. Yield of CO is measured by using the characteristic detector of coal oxidation at 30–90 ℃ . The impact of parameters, such as airflow and particle size, on activation energies is ana- lyzed. Finally, agreement was obtained between activation energies and the dynamic oxygen absorbed in order to test the accuracy of the model. The results show that: 1) a positive exponential relation between concentration of CO and temperature in the process of the experiment is obtained: increases are almost identical and the initial CO is low; 2) the apparent activation energies increase gradually with the sizes of particle at the same airflow, but the gradients increase at a decreasing rate; 3) the apparent activation energies increase linearly with airflow. For the five coal particles, the differences among the energies are relatively high when the airflow was low, but the differences were low when the air- flow was high; 4) the optimum sizes of particle, 0.125–0.25 mm, and the optimum volume of airflow, 100 mL/min, are determined from the model; 5) the apparent activation energies decrease with an increase in oxygen absorbed. A nega- tive exponential relation between the two is obtained.

关键词： coal oxidation at low temperature apparent activation energy particle size airflow

Thermal Behavior and Kinetics of Raw/Pyrolytic Wood and Coal Blends during Co-combustion Process

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Journal of Iron and Steel Research(International) 2016年第9期23卷 917-923页

作者： Jian DING Qing-cai LIU Li-jun JIANG Guo-qing LIU Shan REN Jian YANG Lu YAO Fei MENG College of Materials Science and Engineering Chongqing University

The thermal properties of raw wood（RW） biomass,corresponding pyrolytic wood（PW）biomass,and their blends with anthracite coal（AC） were evaluated under combustion conditions with a thermogravimetric analysis（TGA）method.The blending ratios of the biomass with AC ranging from 0 to 100 mass% were taken into consideration to investigate the thermal behavior and kinetics of these blends during their co-combustion.For blends with different ratios of the RW to AC and 100% AC（100AC）,two distinct mass loss peaks related to the release or combustion process of the volatiles and the combustion of the char were noted.The addition of a higher ratio of RW or PW into AC can improve the combustion process of the blends.The thermal behavior of the RW/AC or PW/AC blends could not be characterized by a simple linear correlation of their pure material thermal behavior.With the RW/PW addition ratios varying from 25 mass% to 80 mass%,the apparent activation energy of the blends gradually decreased from 48.46 to 34.93 kJ/mol and from 82.74 to 37.81 kJ/mol for the RW/AC and PW/AC blends,respectively,with high correlation coefficient（R;） values ranging from 0.995 6 to 0.998 4.

关键词： thermal property thermogravimetric analysis raw wood biomass pyrolytic wood biomass apparent activation energy

Characteristics of Hydrogen Storage Alloy Mg_2Ni Produced by Hydriding Combustion Synthesis

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Journal of Materials Science & Technology 2004年第2期20卷 209-212页

作者： QianLI QinLI LijunJIANG Kou-chihCHOU FengZHAN QiangZHENG ResearchCenterofenergyMaterialsandTechnology GeneralResearchInstituteforNonferrousMetalBeijing100088China DepartmentofPhysicalChemistry UniversityofScienceandTechnologyBeijingBeijing100083China

A high activity and large capacity of hydrogen storage alloy Mg2Ni by hydriding combustion synthesis was investigated by means of pressure composition isotherms, X-ray diffraction and scanning electron microscopy. The results showed that the maximum hydrogen absorption capacity of Mg2Ni is 3.25 mass fraction at 523 K, just after synthesis without any activation. The relationships between the equilibrium plateau pressure and the temperature for Mg2Ni were lgp (0.1 MPa)=-3026/T+5.814 (523 K≤T≤623 K) for hydriding and Igp (0.1 MPa)=-3613/T+6.715 (523 K≤T ≤623 K) for dehydriding. The kinetic equation is [-ln(1-a)]3/2 = kt and the apparent activation energy for the nucleation and growth-controlled hydrogen absorption and desorption were determined to be 64.3±2.31kJ/(mol.H2) and 59.9±2.99kJ/(mol.H2)respectively.

关键词： Hydriding combustion Mg2Ni Hydrogen storage property apparent activation energy

Effect of Al2O3 on the viscosity of CaO-SiO2-Al2O3-MgO-Cr2O3 slags

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International Journal of Minerals,Metallurgy and Materials 2021年第5期28卷 797-803页

作者： Chen-yang Xu Cui Wang Ren-ze Xu Jian-liang Zhang Ke-xin Jiao School of Metallurgical and Ecological Engineering University of Science and Technology BeijingBeijing 100083China State Key Laboratory of Advanced Metallurgy University of Science and Technology BeijingBeijing 100083China

We investigated the effect of Al2O3 content on the viscosity of CaO-SiO2-Al2O3-8wt%MgO-1wt%Cr2O3(mass ratio of CaO/SiO2 is 1.0,and Al2O3 content is 17wt%-29wt%)slags.The results show that the viscosity of the slag increases gradually with increases in the Al2O3 content in the range of 17wt%to 29wt%due to the role of Al2O3 as a network former in the polymerization of the aluminosilicate structure of the slag.With increases in the Al2O3 content from 17wt%to 29wt%,the apparent activation energy of the slags also increases from 180.85 to 210.23 kJ/mol,which is consistent with the variation in the critical temperature.The Fourier-transform infrared spectra indicate that the degree of polymerization of this slag is increased by the addition of Al2O3.The application of Iida’s model for predicting the slag viscosity in the presence of Cr2O3 indicates that the calculated viscosity values fit well with the measured values when both the temperature and Al2O3 content are at relatively low levels,i.e.,the temperature range of 1673 to 1803 K and the Al2O3 content range of 17wt%-29wt%in CaO-SiO2-Al2O3-8wt%MgO-1wt%Cr2O3 slag.

关键词： slag viscosity high aluminium oxide apparent activation energy structure viscosity prediction

Investigation of the kinetic mechanism of the demanganization reaction between carbon-saturated liquid iron and CaF2–CaO–SiO2-based slags

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International Journal of Minerals,Metallurgy and Materials 2018年第4期25卷 399-404页

作者： Sheng-chao Duan Chuang Li Han-jie Guo Jing Guo Shao-wei Han Wen-sheng Yang School of Metallurgical and Ecological Engineering University of Science and Technology Beijing Beijing 100083 China Beijing Key Laboratory of Special Melting and Preparation of High-End Metal Materials Beijing 100083 China China Metallurgical Planning and Research Institute Beijing 100711 China

The demanganization reaction kinetics of carbon-saturated liquid iron with an eight-component slag consisting of CaO–SiO2–MgO–FeO–MnO–Al2O3–TiO2–CaF2 was investigated at 1553, 1623, and 1673 K in this study. The rate-controlling step（RCS） for the demanganization reaction with regard to the hot metal pretreatment conditions was studied via kinetics analysis based on the fundamental equation of heterogeneous reaction kinetics. From the temperature dependence of the mass transfer coefficient of a transition-metal oxide（MnO）, the apparent activation energy of the demanganization reaction was estimated to be 189.46 kJ·mol^–1 in the current study, which indicated that the mass transfer of MnO in the molten slag controlled the overall rate of the demanganization reaction. The calculated apparent activation energy was slightly lower than the values reported in the literature for mass transfer in a slag phase. This difference was attributed to an increase in the ＂specific reaction interface＂（SRI） value, either as a result of turbulence at the reaction interface or a decrease of the absolute amount of slag phase during sampling, and to the addition of calcium fluoride to the slag.

关键词： demoaganization reaction kinetics reaction mechanism kinetic model rate-controlling step mass transfer coefficient apparent activation energy

Effect of magnesium injection process on hot metal desulfurization

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Journal of Iron and Steel Research(International) 2020年第12期27卷 1391-1399页

作者： Jian-ming Su Zhi-he Dou Ting-an Zhang Yan Liu Key Laboratory of Ecological Metallurgy of Multi-metal Intergrown Ores of Ministry of Education Northeastern UniversityShenyang 110819LiaoningChina General Steelmaking Plant Anshan Iron and Steel Group Co.Ltd.Anshan 114021LiaoningChina

To solve the technical problems of hot metal desulfurization by injecting magnesium particulate, a new method of hot metal desulfurization by bottom-blowing magnesium vapor combined with mechanical agitation was put forward. The effects of three different desulfurization processes on the desulfurization efficiency were studied in view of thermodynamics and kinetics. It was found that the utilization efficiency of magnesium can reach 82.6% and desulfurization efficiency can reach 86.2% during the first 4 min using the method of magnesium vapor injection combined with mechanical agitation. The gasification of magnesium powder leads to significant splashing and magnesium losses in the process of magnesium powder injection, resulting in a low utilization efficiency of magnesium of 51.8% and a low desulfurization efficiency of 55.76%. activation energy for a first-order kinetic relationship between magnesium powder and sulfur was measured from the experiments, which was 142.82 kJ/mol in the temperature range of 1573-1723 K. The activation energy of the reaction between magnesium vapor and sulfur was around 54.8-65.0 kJ/mol in the temperature range of 1573-1723 K, which indicates that the desulfurization with magnesium vapor proceeds relatively easier than the desulfurization with magnesium powder.

关键词： Magnesium injection process Hot metal desulfurization Mechanical agitation apparent activation energy Magnesium vapor Bottom blowing

Effect of vanadium content on microstructure and properties of in situ TiC reinforced V_(x)FeCoNiCu multi-principal-element alloy matrix composites

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Journal of Iron and Steel Research(International) 2021年第11期28卷 1471-1480页

作者： Chun-lei Tu Xiao-dong Sun Jie Li He-guo Zhu Xiang-dong Li College of Mechanical Engineering Southeast UniversityNanjing 210094JiangsuChina Special Equipment Safety Supervision Inspection Institute of Jiangsu Province Nanjing 210036JiangsuChina College of Materials Science and Engineering Nanjing University of Science and TechnologyNanjing 210094JiangsuChina

V_(x)FeCoNiCu high entropy alloy matrix composites reinforced by in situ TiC particles(10 vol.%),i.e.,V_(x)FeCoNiCu/TiC composites,were fabricated from V–Fe–Co–Ni–Cu–Ti–C system using vacuum inductive melting method.With the content of vanadium increasing,the size of TiC particles decreased gradually.Meanwhile,vanadium agglomeration occurred slightly.The reaction mechanism of the mixed powder(Fe,V,Ti and C)and the mechanical properties of obtaining V_(x)FeCoNiCu/TiC composites were studied.It was found that three reactions occurred(Fe-Ti-FeTi-Fe_(2)Ti,FeTi-Fe_(2)Ti-Fe-Ti and Ti-C-TiC)in the heating process.The apparent activation energy for these three reactions was calculated and found to be 26.4,698.3 and 1879.0 kJ/mol,respectively.At room temperature,tensile strength and elongation increased first and then decreased with the increase in vanadium content and the microhardness increased gradually.The maximum tensile strength of the composites was determined to be 666 MPa,representing a 17.7%increase over that of FeCoNiCu/TiC high entropy alloy composites.

关键词： High entropy alloy matrix composite Vacuum inductive melting Reaction mechanism apparent activation energy Tensile strength