CHEMICAL ENGINEERING SCIENCE
·
2021
·
IF 4.311
Zhang Li,Zhaolin Gu,Ran Li,Chen Wang,Chungang Chen,Chunlei Yu,Yigen Zhang,Qinglin Shu,Junwei Su
Droplet snap off is one of the most usual phenomena in oil recovery during water injection in water-wet porous media. In this work, the droplet dynamic snap-off process in a short, abrupt constriction is investigated. Three different phenomena, i.e. total breakup, partial breakup and non-breakup, of the nonwetting phase droplets are observed, the flow characteristics of droplets in each phenomenon and relevant physical mechanisms are analyzed. We find that both the initial size and velocity of the droplet greatly influence the breakup process. The viscosity of droplet also affects the breakup state. The critical conditions of each phenomenon are obtained based on dimensionless droplet size and capillary number, which could be used to predict the droplet breakup state. Under a certain capillary number, daughter droplet distribution is influenced by initial droplet size.
研究领域:
石油工程
·
流体力学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
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2021
·
IF 5.471
Jincheng Lei,Ziqian Li,Shuai Xu,Zishun Liu
Fracture is a highly nonlinear problem, especially under a large deformation in cross-linked elastomers. Existing constitutive theories and fracture models fail to predict the fracture behavior of cross-linked elastomers because of the absence of the random polymer network structure. Meanwhile, few numerical methods can present the realistic fracture process of a polymer network. In this study, we propose a mesoscopic network mechanics method to present the entire large deformation and fracture process of the polymer network in cross-linked elastomers. The microstructure of a cross-linked elastomer is abstracted as a polymer network model where nodes are referred to as crosslinkers and connections between nodes are referred to as polymer chains. A hybrid total energy form of the network model is proposed including the free energy of polymer chains and volumetric deformation energy. In addition, using a proposed stretch criterion of polymer chains to realize chain scission, this mesoscopic network mechanics method is numerically implemented by coding. Two-dimensional network models with uniform and randomly distributed chain lengths, as well as models with different types of pre-cracks, are constructed and simulated under uniaxial tension tests using our method. Our method reproduces the entire hyper-elastic large deformation and fracture process of polymer network models. The random network models show a lower Young's modulus and a less significant strain-hardening stage, indicating that the structural randomness is the primary cause of accuracy degradation for existing hyperelastic constitutive models under large deformations. The results also reveal that the structural randomness of the polymer network is a primary reason for the ductile fracture and the low notch sensitivity of cross-linked elastomers.
研究领域:
材料科学
·
力学
✓ 已验证
产品关联
DOI
高影响因子
Materials Today Physics
·
2020
·
IF 10.443
S.Y. Zheng,H.C. Yu,C. Yang,W. Hong,F. Zhu,J. Qian,Z.L. Wu,Q. Zheng
The rapid developments of tough hydrogels have broadened the applications of gel materials in biomedicine and engineering fields, which recalls the fundamental understanding of the fracture behaviors of these tough, soft materials. Herein, we study the fracture behaviors of a Fe 3+ coordinated poly(acrylic acid- co -acrylamide) (P(AAc- co -AAm)) hydrogel through pure shear tests. We measure a material-specific length, called fractocohesive length L f , defined by the ratio of fracture energy to fracture work ( L f = Г / W f ). We show that L f scales several important lengths that characterize the fracture behaviors of the hydrogel, including the transition length of cut-sensitivity L c measured by stretching samples of various initial crack lengths to rupture, the increment of the crack length needed to attain the steady state L ss measured from the resistance curve, and the size of large deformation zone L i measured by the polarized microscopic image. We further show that the fracture of P(AAc- co -AAm) hydrogel is viscoelastic, as demonstrated by tensile and rheological tests at different deformation rates . This work gives an insight into the fracture behaviors of P(AAc- co -AAm) hydrogel and provides a methodology that should be applicable in characterizing the fracture behaviors of other tough materials.
研究领域:
材料科学
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生物医学工程
✓ 已验证
产品关联
DOI
高影响因子
CERAMICS INTERNATIONAL
·
2021
·
IF 4.527
Jinzhu Zou,Huiwen Xiong,Yujuan Huang,Kechao Zhou,Dou Zhang
Porous zirconia with different porosity and pore architecture were prepared by adjusting the solid loading and the binder concentration of the suspensions, and freezing rate via an ice-templating method. The transition of the fracture mode and the relationship between the compressive strength and process parameters were identified and investigated. The load-displacement curves showed a variation from a buckling fracture at porosity above 70 % to a brittle fracture in the porosity range from 35.3 % to 55.5 %, owning to the increased resistance of the ceramic walls to buckling. As the porosity decreased from 75.0 % to 35.3 %, the mean compressive strength of the samples increased from 4.5 MPa to 197.1 MPa. Under buckling fracture, increasing the binder concentration from 2 wt% to 4 wt% contributed to the improvement of the mean compressive strength from 5.5 MPa to 14.8 MPa, although samples had similar porosity level (~73 %). For brittle fracture, samples with porosity around 54 % exhibited the improvement of mean compressive strength from 45.5 MPa to 75.1 MPa when increasing the freeze velocity from 8 °C/min to 25 °C/min.
研究领域:
材料科学
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陶瓷
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力学性能
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF ORGANIC CHEMISTRY
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2020
·
IF 4.335
Nian Zheng,Ce Liu,Ya-Nan Ding,Wei-Yu Shi,Bo-Sheng Zhang,Yong-Min Liang
Copper-catalyzed three-component redox-neutral ring opening of benzothiazoles with aryl iodides and O-benzoyl hydroxylamines for the synthesis of 1-amino-N-(2-(phenylthio)phenyl)methanimine has been developed. This one-pot reaction undergoes C–S and N–O bond cleavage and new C–S and C–N bond construction. Several control experiments excluded a free radical procedure and also demonstrated the secondary amine as a possible intermediate, which was vital to the catalytic reaction. Meanwhile, the deuteration experiment got rid of the C–H activation dehydroisomerization of the benzothiazole mechanism.
研究领域:
有机化学
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合成化学
✓ 已验证
DOI
PubMed
高影响因子
RENEWABLE ENERGY
·
2021
·
IF 8.001
Feng Lin,Yulong Ma,Yonggang Sun,Kanghe Zhao,Tingting Gao,Yingbo Zhu
Due to the inertness and structural complexity of lignin, upgrading lignin to biofuels and fine chemicals still faces great challenges. In this paper, a one-pot method was used to catalyze straw lignin with H-ZSM-5 supported by Ni and Ru bimetals, and the lignin conversion rate reached 88.1%. The yield of monophenol was 19.5%, of which the yield of 4-ethylphenol and 4-ethylguaiacol was 4.9% and 3.8%, respectively. The 2D HSQC NMR analysis confirmed that the Ni–Ru/H-ZSM-5 catalyst had an obvious activity of breaking C β -O bonds before and after the reaction. The result showed that after loading metal Ni and Ru, the Lewis acid of the catalytic system was greatly increased, which caused electron transfer between Ni and Ru. 3Ni-1.5Ru/H-ZSM-5 had the strongest activity due to the largest synergy among Ni, Ru and H-ZSM-5. The synergy was the key factor leading to the cleavage of C–C and C–O bonds in straw lignin and the high-performance catalytic degradation of lignin. Besides, the effect of reaction solvent and hydrogen resource on upgrading lignin to fine chemicals over 3Ni-1.5Ru/HZSM-5 catalyst was also intensively investigated. This research developed a method for the direct conversion of lignin into valuable monophenols.
研究领域:
催化化学
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生物质转化
✓ 已验证
产品关联
DOI
高影响因子
ChemCatChem
·
2016
·Vol. 8
·期 11
·1929-1936
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IF 4.724
Bin Chen,Bin Zhang,Yibo Zhang,Xiangguang Yang
Graphical Save it for a Raney day : A series of Ag-modified Ni catalysts is prepared, and the role of bimetallic effects on the selective cleavage of C−O and C−C bonds is investigated in glycerol hydrogenolysis, a model reaction for the utilization of biomass-derived polyols. Compared to Raney Ni, the optimal Raney Ni 6 Ag catalyst is more active in glycerol conversion and efficient for C−O bond cleavage to afford a higher selectivity toward C 3 products. A series of Ag-modified Ni catalysts was prepared, and the role of bimetallic effects on the selective cleavage of C−O and C−C bonds was investigated in glycerol hydrogenolysis, a model reaction for the utilization of biomass-derived polyols. Compared to Raney Ni, the optimal Raney Ni 6 Ag catalyst was more active in glycerol conversion and efficient for C−O bond cleavage to afford a higher selectivity toward C 3 products (1,2-propanediol and lactic acid; 88 %) at the same ∼70 % conversion of glycerol, especially 1,2-propanediol (73 %). On Ni catalysts, the hydrogenation of adsorbed species was the most likely rate-limiting step in glycerol hydrogenolysis under alkaline conditions. The Ag additive enhanced the hydrogenation ability of Ni catalysts, which should be related to the higher strength of the adsorption of hydrogen and the lower strength of the adsorption of substrates on Ni sites because of the formation of Ni-Ag alloys. A mechanistic interpretation was presented for the excellent catalytic behavior.
研究领域:
催化化学
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生物质利用
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材料科学
✓ 已验证
DOI
高影响因子
Catalysis Science & Technology
·
2024
·Vol. 14
·期 14
·4058-4067
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IF 4.4
Yang You,Aijie Xu,Yao Lv,Lide Yang,Xuan Tang,Jie Tang,Yanglong Guo,Yao Cui,Wangcheng Zhan,Li Wang,Yun Guo,Sheng Dai
Complete oxidation of propane has drawn great attention in the fields of automotive emission control and volatile organic compound elimination. However, it is challenging to achieve high activity of this reaction due to the stability of propane. We here utilize a facile solvothermal method to construct tri-coordinated Al (AlIII) sites on the as-synthesized ST-Al2O3 support to alter the properties of supported Pt species. It is demonstrated that AlIII sites facilitate the dispersion and electron enrichment of supported Pt sites. Thus, Pt/ST-Al2O3 exhibits a superior activity toward complete propane oxidation, showing a 6.7-fold improvement in the turnover frequency over commercial Pt/Al2O3 catalysts. Meanwhile, Pt/ST-Al2O3 possesses a distinct reaction route originating from its stronger C–H and C–C cleavage capability, while having excellent activity not only in complete propane oxidation but also in the complete oxidation of other alkanes (CH4, C2H6, and n-C4H10). In addition, the AlIII construction strategy is successfully extended to more cases, e.g., Pd/ST-Al2O3 with higher Pd dispersion and electron density. This work provides a promising strategy for the control of the oxide support for advanced design and synthesis of alkane oxidation catalysts.
研究领域:
催化化学
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环境科学
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材料科学
✓ 已验证
产品关联
DOI
高影响因子
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
·
2020
·Vol. 22
·期 20
·11508-11518
·
IF 3.43
Jing Chen,Hanling Yang,Hongquan Fu,Hongyan He,Qiang Zeng,Xuehui Li
Electrochemical oxidation is a promising and effective method for lignin depolymerization owing to its selective oxidation capacity and environmental friendliness. Herein, the electrooxidation of non-phenolic alkyl aryl ether monomers and β-O-4 dimers was experimentally (by cyclic voltammetry, in situ spectroelectrochemistry, and gas chromatography-mass spectroscopy) and theoretically (by DFT calculations) explored in detail. Compared to the reported literature (T. Shiraishi, T. Takano, H. Kamitakahara and F. Nakatsubo, Holzforschung, 2012, 66(3), 303–309), 1-(4-ethoxyphenyl)ethanol showed a distinguishable oxidation pathway, where the resulting carbonyl product surprisingly underwent a bond cleavage on alkyl–aryl ether to ultimately produce a quinoid like compound. In contrast, β-O-4 dimers, like 2-phenoxy-1-phenethanol and 2-phenoxyacetophenone also demonstrated electrochemical oxidation induced by Cβ–O and Cα–Cβ bond cleavages. For the oxidation products, the presence of the Cα-hydroxyl group in dimers was the key to selectively generate aldehyde-containing species under mild electrochemical conditions, otherwise it produces alcohol-containing products following a different mechanism compared to the CαO containing dimers.
研究领域:
林产化学
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环境科学
·
有机化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
MATERIALS SCIENCE FORUM
·
2016
·
IF 0
Yu Mei Zhou,Feng Lin Zhang,Peng Cheng Li,Kun Bai,Shang Hua Wu
AlMgB14 is a very hard and brittle material which need be modified for utilizing as cutting tool materials. In present study, TiB2 and Ni3Al were used to strengthen and toughen AlMgB14 material. The microstructure of the AlMgB14-TiB2-Ni3Al composites was analysized by scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDX) and an X-ray diffractometer (XRD). The hardness and fracture toughness of the AlMgB14-TiB2Ni3Al composites were also examined. The results showed that the major phases in AlMgB14-Ni3Al composites were TiB2, AlMgB14, MgAl2O4 , Ni3Al and NiAl. With the increasing of the amount of Ni3Al, more intergranular fractured features can be found in the fractured surface of the composites, the hardness and fracture toughness of the composites were both decreased comparing to the synthesised AlMgB14. The AlMgB14-TiB2-4wt.% Ni3Al composite has a hardness of 28.1 Gpa and a fracture toughness of 3.14 MPa·m1/2.
研究领域:
材料科学
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机械工程
✓ 已验证
DOI
Catalysis Science & Technology
·
2023
·Vol. 13
·期 6
·1748-1754
·
IF 5
Shaoyuan Guo,Xinli Tong,Lingwu Meng,Guobao Yang
Selective oxidative C–C and C–O bond cleavage is of significance to the efficient utilization of biomass and biomass-derived platform compounds. In this work, the selective oxidative cleavage of C–C and C–O bonds has been developed with an iron-based catalyst (Fe–N–C) in the presence of molecular oxygen. Specifically, the β-O-4 lignin model compound was successfully converted to phenol and methyl benzoate in a methanol solvent, where the substrate conversion was 95.0% and the yields of phenol and methyl benzoate were 94.9% and 63.7%, respectively, when the reaction was performed with the Fe–N–C-850 catalyst at 120 °C for 4 h. Also, the oxidative transformations of other lignin models to phenols and methyl benzoates were achieved. Further investigations showed that the existence of the Fe3C phase in the catalyst plays an important role in the aerobic oxidative cleavage of C–C and C–O bonds in the β-O-4 lignin model.
研究领域:
生物质化学
·
催化化学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF THE ELECTROCHEMICAL SOCIETY
·
2021
·Vol. 168
·期 1
·016504
·
IF 4.316
Haomin Jiang,Yujuan Cheng,Zhaohui Wang,Zhiqun Bai,Yang Tang,Yanzhi Sun,Pingyu Wan,Yongmei Chen
The cleavage of the linkage bonds among the C9 units in lignin molecules via selective oxidation method to obtain small-weight aromatic compounds is an important way to lignin valorisation. In this study, the cleavage pathways of bonds in a lignin model compound, GGE (guaiacylglycerol-β-guaiacyl ether), by the reactive oxygen species (ROS) in situ generated through electrochemical oxygen reduction reaction (ORR) in an aprotic ionic liquid ([BMIM]BF4) was investigated. The results indicated that when the main ROS was ·OOH, coniferyl alcohol, guaiacol and vanillin were detected as the degradation products which is supposed to be caused by β-O-4 bonds cleavage; Otherwise, when HO2− was the main ROS, coniferyl alcohol could not be detected and the degradation reaction is believed to be trigerred by Cα-Cβ bonds cleavage.
研究领域:
生物化学
·
环境科学
✓ 已验证
DOI
高影响因子
危险品化学品经营许可证（带存储）