MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
·
2024
·
IF 6.1
Qianglong He,Wenchao Guo,Yunwei Shi,Aiyang Wang,Weimin Wang,Zhengyi Fu
In this study, B 4 C–TiB 2 –graphite ceramic composites were prepared via reactive hot-pressing sintering using B 4 C and TiC as the raw materials. The reaction process, microstructure, and mechanical properties were investigated. The solid-phase reaction is a diffusion-controlled process, wherein the B atoms diffuse into TiC and react to form TiB. Thereafter, TiB 2 is generated with the entry of subsequent B atoms. A core–shell structure is formed, wherein TiB 2 particles are wrapped by layered graphite. The products TiB 2 and graphite inhibit the growth of B 4 C matrix grains, which are instrumental in fine grain strengthening. In addition, the novel TiB 2 –graphite-agglomerated structure significantly improves the fracture toughness of the ceramic composites through crack deflection, bridging, and branching toughening mechanisms. Therefore, the comprehensive properties of B 4 C–TiB 2 –graphite ceramic composites are better than those of pure B 4 C ceramics. Specifically, the fracture toughness is approximately 6.77 MPa m 1/2 , which is considerably higher than that of pure B 4 C ceramics (2.47 MPa m 1/2 ).
研究领域:
材料科学
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陶瓷工程
✓ 已验证
产品关联
DOI
高影响因子
BIOCHEMICAL SYSTEMATICS AND ECOLOGY
·
2023
·
IF 1.6
Shuang Guo,Dongyu Gu,Chang Liu,Shanshan Tang,Yi Wang,Yi Yang
Morus alba leaves have a long history as a plant medicine and possess many biological activities. Antioxidant activity is the basis of its many biological activities. In order to explore the antioxidant effect of Morus alba leaves, antioxidant and its mechanism of scavenging free radicals have been investigated in this study. As results, rutin with the EC 50 of 27.94 ± 1.18 μg/mL and 25.86 ± 0.09 μg/mL to DPPH· and ABTS· + respectively was enriched by liquid-liquid extraction, and isolated by high-speed counter-current chromatography and identified by NMR, and was recognized as the main antioxidant in Morus alba leaves. The results of reaction thermodynamics and frontier molecular orbital theory indicated that 4′-OH in rutin was the most active group, which scavenged free radicals by hydrogen atom transfer in non-polar media and single electron transfer followed by proton transfer in polar media. Polar solvents were more helpful for rutin to exert its antioxidant effect. This study not only explored the antioxidant basis of Morus alba leaves, but also revealed its mechanism of scavenging free radicals.
研究领域:
植物化学
·
药理学
✓ 已验证
产品关联
DOI
高影响因子
ORGANIC PROCESS RESEARCH & DEVELOPMENT
·
2021
·
IF 3.317
Jihe Zhao,Wenhai Zhang,Jiwen Hu,Shudong Lin,Xuefeng Gui,Shi Li,Xiao Wang,Zhihua Li,Yuanyuan Tu,Fuwei Nian,Daguang He
Polymerization reactions are exothermic processes that are often accompanied by viscosity changes, and they can pose hazards due to thermal runaway. This paper describes an investigation of the potential for thermal runaway in the industrial process of styrene solution polymerization, in which particular focus was devoted to the effects of the monomer concentration and the solvent. As the monomer concentration increased from 20.0 to 50.0 wt %, the heat of reaction Qr and the adiabatic temperature rise ΔTad increased in a linear manner from 19.0 ± 0.2 to 58.1 ± 0.6 kJ and 21.7 ± 0.1 to 64.8 ± 0.6 K, respectively, and the maximum temperature attained by the synthesis reaction (MTSR) was also increased from 86.1 ± 0.2 to 101.5 ± 0.2 °C. In addition, the molecular weight distribution of polystyrene was around 1.9, and the distribution was broad. The risk of a potential runaway reaction was evaluated using the Stoessel assessment criteria and Zurich Hazard Analysis. The criticality of runaway polymerization remained constant with increasing concentration, and class 1 risk was observed. However, the severity of a potential runaway reaction was increased from negligible to medium class. It was found that the solvent had an important effect on the risk of thermal runaway during polymerization. The criticality of the high-boiling solvents toluene and cyclohexanone used in this work was class 1, while that of the low-boiling solvent ethyl acetate was class 3. This work provides valuable insight that can help to control thermal risk in the chemical industry.
研究领域:
化学工程
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安全科学
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2020
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IF 3.83
Shuai Wang,Yangyang Deng,Mingsheng Yang,Luyao Wang,Huaiqian Li,Pengfei Xing
Dense B 4 C–SiC–CrB 2 ternary composites were fabricated via reactive hot pressing with B 4 C and chromic silicides (84 wt% CrSi 2 +16 wt% CrSi) as raw materials. The effects of chromic silicides on the densification, phase components, microstructure and performance of the prepared composites were investigated. The reaction mechanism and toughening mechanism were also studied. The results indicated that the chromic silicides were the reactive sintering aids which reacted with B 4 C and C to introduce CrB 2 and SiC in the matrix in situ. Partial B 4 C, CrB 2 and SiC formed the eutectic liquid phase, which enhanced the densification of B 4 C. The addition of chromic silicides enhanced the densification and fracture toughness while reduced the hardness. The good comprehensive performances of 435 MPa flexural strength , 4.09 MPa m 1/2 fracture toughness and 33.11 GPa hardness were obtained in the composites fabricated with 10 wt% chromic silicides. The higher addition amounts of chromic silicides resulted in the larger-size SiC, which reduced the flexural strength. The transgranular fracture of SiC and partial CrB 2 , the existing phenomena such as microcracks , crack branching and crack deflection could cumulatively improve the fracture toughness of the materials.
研究领域:
材料科学
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陶瓷学
✓ 已验证
DOI
高影响因子
JOURNAL OF WUHAN UNIVERSITY OF TECHNOLOGY-MATERIALS SCIENCE EDITION
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2021
·Vol. 35
·期 6
·1031-1037
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IF 0.957
Cao Yaoqin,He Qianglong,Wang Weimin
B 4 C-TiB 2 -SiC composites with excellent properties were prepared by reactive hot-pressing using B 4 C, TiC, and Si powders as the raw materials. The phase transition process was investigated by heating the powder mixture to different temperatures and combined with XRD tests. TiB 2 and SiC phases were synthesized through an in situ reaction, and the mechanical and thermal properties were improved simultaneously. Microstructure and mechanical properties were also studied, and the 60wt% B 4 C-21.6wt% TiB 2 -18.4wt% SiC composite showed a relative density of 99.1%, Vickers hardness of 34.6 GPa, flexural strength of 582 MPa, and fracture toughness of 5.08 MPa·m 1/2 . In addition, the values of thermal conductivity and thermal expansion coefficient were investigated, respectively.
研究领域:
材料科学
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工程学
✓ 已验证
DOI
高影响因子
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
·
2024
·Vol. 149
·期 10
·4827-4838
·
IF 3
Li Weilong,Zhang Fengyan,Li Xiaoquan,Hu Jiwen,Gui Xuefeng,Lin Shudong
Epoxy acrylate is produced by esterifying epoxy resin and acrylic acid through a ring-opening reaction. This process is highly exothermic and can be challenging to control gel formation. The thermal hazards of epoxy acrylate preparation were evaluated in this study by investigating the ring-opening esterification reaction between acrylic acid (AA) and bisphenol A epoxy resin (E-51) catalyzed by triethylamine (TEA). The heat release during the reaction process was analyzed using a reaction calorimeter (RC1 mx ) to simulate industrial conditions. Increasing the TEA catalyst content from 0.3 to 1.0 mass% resulted in a significant rise in reaction conversion from 75.35 ± 0.10% to 98.44 ± 0.10%. Differential scanning calorimetry (DSC) and accelerating rate calorimeter (ARC) were used to examine the thermal runaway process during epoxy acrylate synthesis. Increasing the TEA content from 0.3 to 1.0 mass% decreased the initial reaction temperature from 60.16 ± 0.62 to 45.33 ± 0.40 °C and the critical temperature of side reactions from 153.71 ± 1.51 to 117.85 ± 1.19 °C. The severity of the runaway was classified as medium at process temperatures of 80–110 °C. This study highlights the importance of considering reaction conditions to prevent uncontrolled reactions during epoxy acrylate synthesis, providing valuable insights for industrial epoxy acrylate preparation.
研究领域:
化学工程
·
安全科学
✓ 已验证
产品关联
DOI
高影响因子
MATERIALS CHEMISTRY AND PHYSICS
·
2024
·
IF 4.3
Yonghui Yu,Jie Wei,Xianghui Yan,Yuhong Chen,Biao Zhang,Yujin Wang,Feng Ye,Limeng Liu
TaB 2 –SiC composites with 0–20 wt% SiC contents were prepared by reaction hot pressing using Ta, B and SiC powders as starting materials. Densification, constituent phases, microstructure and mechanical properties, namely Vickers hardness, fracture toughness and flexure strength, were evaluated by means of inspection of sintering shrinkage, density measurement, XRD, SEM, TEM, HRTEM, EDS, SAED, indentation and three-point bending tests. Phase formation, including dominant (TaB 2 , SiC) and minor (TaC, glassy SiO 2 ) phases, was checked by thermodynamic assessment relevant with Ta 2 O 5 and B 2 O 3 impurities introduced into the reaction system by the starting powders. The results showed that mixtures of Ta, B and SiC powders would initiate self-propagating combustion synthesis (SPCS) at about 900 °C; a transient hold at 800 °C for 1 h could suppress this reaction. Volatilization of B 2 O 3 impurity in association with local high temperature due to SPCS helped reduce the TaC and glassy SiO 2 minor phase formation. TaB 2 –SiC composites could reach 99 % relative densities with 3 wt% SiC addition and above. Compositions with <7.5 wt% SiC additions showed uniform dispersion of SiC particles at multi-TaB 2 grain junctions while compositions with higher SiC content revealed SiC segregation. Bending strength of 503 MPa and fracture toughness of 6.69 MPa⋅m 1/2 could be reached with 7.5–20 wt% SiC addition.
研究领域:
材料科学
·
机械工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2016
·
IF 2.933
Xiaorong Zhang,Zhixiao Zhang,Weimin Wang,Xiaoliang Zhang,Jingbo Mu,Guangsuo Wang,Zhengyi Fu
High-performance B 4 C composites toughened by TiB 2 -SiC agglomerates were fabricated via reactive hot pressing with B 4 C, TiC and Si as raw materials. The TiB 2 -SiC composite serves as a composite toughening phase formed in the B 4 C matrix through an in situ reaction; its agglomerates are composed of interlocked TiB 2 and SiC, which can remarkably improve the toughness of the B 4 C composites. The Vickers hardness , flexural strength and fracture toughness of the B 4 C-TiB 2 -SiC composite reached 35.18 ± 0.45 GPa, 567 ± 14 MPa, and 6.38 ± 0.18 MPa m 1/2 respectively. The special toughening structure of the TiB 2 -SiC composite introduced into B 4 C ceramics was evaluated for the first time in this study.
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2019
·
IF 4.029
Xiaorong Zhang,Zhixiao Zhang,Yuming Liu,Aiyang Wang,Shi Tian,Weimin Wang,John Wang
In this work, we systematically studied the effects of powder characteristics (B 4 C, TiC and Si powders) on the existential form of toughening phases (SiC and TiB 2 ) as well as the overall microstructure and properties of B 4 C–TiB 2 –SiC composites fabricated by reactive hot pressing. The particle size of the TiC powder plays a largely determining role in the development of novel toughening phases, the TiB 2 –SiC composite structure, that are formed in the B 4 C matrix, while the Si particle size affects the agglomerate level of the SiC phase. The TiB 2 –SiC composite structure and SiC agglomerates enhance the fracture toughness, but decrease the flexural strength . Both the microstructure and mechanical properties of B 4 C–TiB 2 –SiC composites can be effectively tuned by regulating the combinations of the particle sizes of the starting powders. The B 4 C–TiB 2 –SiC composites demonstrate flexural strength, fracture toughness and Vickers hardness in the respective range of 567–632 MPa, 5.11–6.38 MPa m 1/2 , and 34.8–35.6 GPa.
研究领域:
材料科学
·
机械工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ALLOYS AND COMPOUNDS
·
2014
·
IF 2.726
Zhixiao Zhang,Chongjun Xu,Xianwu Du,Zili Li,Jilin Wang,Weihong Xing,Yuan Sheng,Weimin Wang,Zhengyi Fu
High-performance TiB 2 –SiC composites were fabricated with a new reaction system of B 4 C–TiC–Si by reactive hot pressing. The reaction process was controlled by the diffusion of boron atoms and hindered by the accumulated product layer of TiB 2 and C. The melting Si can offer another diffusion path for boron atoms, thereby promoting the reaction process. The Vickers hardness , flexural strength , and fracture toughness of the fabricated TiB 2 –SiC composites respectively reached 28.6 ± 0.6 GPa, 654 ± 49 MPa, and 6.8 ± 0.5 MPa m 1/2 . Both the intergranular fracture resulting from mismatch in thermal expansion coefficient between TiB 2 and SiC and the transgranular fracture resulting from the network structure of TiB 2 can enhance the fracture toughness of the TiB 2 –SiC composite.
研究领域:
材料科学
·
机械工程
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
·
2022
·
IF 6.364
Qingyi Kong,Sijia Huo,Lei Chen,Yujin Wang,Jiahu Ouyang,Yu Zhou
Fully dense (Zr, Ti)B 2 -(Zr, Ti)C-SiC ceramics were prepared by reactive hot-pressing using ZrB 2 , TiC, and SiC as the initial materials for the first time. Effects of SiC addition on the microstructure evolution and mechanical properties were reported. The in-situ reaction between ZrB 2 and TiC as well as the SiC addition leads to the grain refinement. Besides, elongated (Zr, Ti)B 2 plate-like grains are obtained due to the occurrence of a transient liquid phase, which leads to the crack deflection in the matrix effectively. Mechanical properties are improved significantly due to grain-refinement and solid solution strengthening, and plate-like grains toughening effects. The ZrB 2 -10 mol%TiC composite with 10 mol% SiC additional exhibits good comprehensive mechanical properties of the hardness of 20.2 GPa, the flexural strength of 803 MPa, and the fracture toughness of 5.7 MPa m 1/2 .
研究领域:
材料科学
·
陶瓷工程
✓ 已验证
产品关联
DOI
高影响因子
SEPARATION AND PURIFICATION TECHNOLOGY
·
2024
·
IF 8.1
Yikang Huang,Liang Zhu,Ning Zeng,Pinjie Wang,Ge Gao,Wufeng Jiang,Xiaoshan Li,Liqi Zhang
Developing amine solutions with low energy consumption is of great significance for CO 2 capture technology. Currently most of studies focused on reducing sensible heat and heat of vaporization by anhydrous absorbents and phase-change absorbents based on amines. It should be noted that CO 2 reaction heat of amines is also an important section for energy consumption. In this work, CO 2 reaction heat of 7 secondary amines was investigated aiming to reveal structure–activity relationship between CO 2 reaction heat and the length of the carbon chain, methyl side chain and hydroxyl group in secondary amines. The CO 2 reaction heat of 7 secondary amines was directly measured by microcalorimeter with high precision. Results showed that increasing the length of carbon chain, introducing hydroxyl group and removing methyl side chain in secondary amines could increase CO 2 reaction heat. The lengthening of carbon chain and the addition of the hydroxyl group led to an increase in the electronegativity in N atom of the secondary amines, thereby increasing the reactivity and reaction heat of the secondary amine. The steric hindrance caused by methyl side chain reduced the reactivity and reaction heat of secondary amine. This study could help to screen and develop energy-saving secondary amine absorbents for CO 2 capture.
研究领域:
化学工程
·
环境科学
·
物理化学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）