检索结果-南通市图书馆

Cementing mechanism of bio-phosphate cement

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2015年第6期58卷 1112-1117页

作者： YU XiaoNiu QIAN ChunXiang WANG Xin school of materials Science and Engineering Southeast University Research Institute of Green Construction materials Southeast University

Cementing mechanism of bio-phosphate cement was investigated by Fourier transform infrared spectroscopy(FTIR), X-ray photoelectron spectroscopy(XPS), thermogravimetric-differential scanning calorimetry(TG-DSC) analysis and scanning electron microscopy(SEM). The results of FTIR and XPS show that Si-O bond and Si(2p) electron binding energy in sandstone cemented via chemical and microbiological methods are changed by the binding effects of barium hydrogen phosphate with quartz sand. Compared with barium hydrogen phosphate precipitated in solution, there were higher decomposition temperatures or melting points in sandstone. The FTIR, XPS, and TG-DSC results indicate that the microbial-induced and chemical precipitation of barium hydrogen phosphate can interact with quartz sand to generate van der Waals bond, which plays a role in the binding function between loose sand particles and barium hydrogen phosphate. SEM results show that barium hydrogen phosphate after chemical precipitation in sandstone has better dispersion than microbiological deposition. Therefore, barium hydrogen phosphate via chemical precipitation did not bind loose sand particles into sandstone.

关键词： X-ray photoelectron spectroscopy Fourier transform infrared spectroscopy cementing mechanism bonding effects van der Waals bond

The near-Surface Region of Cubic Boron Nitride Single Crystal from the Li3N-hBN System

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 2014年第4期31卷 182-184页

作者： GUO Xiao-Fei XU Bin WEN Zhen-Xing FAN Xiao-Hong TIAN Bin school of materials Science and Engineering Shandong University Jinan 250061 school of materials Science and Engineering Shandong Jianzhu University Jinan 250101

Cubic boron nitride single crystals are synthesized with lithium nitride as a catalyst under high pressure and high temperature. The main phases in the near-surface region, which around the single crystal are determined as a mixture of hexagonal boron nitride （hBN）, cubic boron nitride （cBN） and lithium boron nitride （Li3BN2）. High resolution transmission electron microscopy examinations show that there exist lots of nanometer-sized cubic boron nitride nuclei in this region. The interface phase structures of cubic boron nitride crystal and its near-surface region are investigated by means of transmission electron microscopy. The growth mechanism of cubic boron nitride crystal is analyzed briefly. It is supposed that LisBN2 impels the direct conversion of hBN to cBN as a real catalyst, and cBN is homogeneously nucleated in the molten state under high pressure and high temperature.

关键词： BORON nitride SINGLE crystals -- Spectra LITHIUM nitrides HIGH resolution spectroscopy NUCLEATION TRANSMISSION electron microscopy

Insights into efficient transition metal-nitrogen/carbon oxygen reduction electrocatalysts

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Energy Chemistry 2021年第5期30卷 470-485页

作者： Hao-Yu Wang Chen-Chen Weng Zhong-Yong Yuan National Institute for Advanced materials School of Materials Science and EngineeringNankai UniversityTianjin 300350China

It is of vital importance to accelerate the sluggish oxygen reduction reaction(ORR)process at the cathode with earth-abundant metal-based catalysts for the commercialization of low-temperature polymer electrolyte membrane fuel *** consideration of high catalytic activity,long-term stability and low cost of potential ORR electrocatalysts,transition metal species have attracted much interest and transition metal-nitrogen-carbon(M-N/C,M=Fe,Co,Ni,Mn,etc.)catalysts have been widely considered as the most promising non-precious metal catalysts for ***,the fundamental understanding of ORR catalytic mechanism and the identification of active centers are briefly introduced,and then different M-N/C catalysts classified by precursors with the strategies for design and optimization are *** challenges and possible opportunity for future development of high-performance ORR catalysts are finally proposed.

关键词： Electrocatalysis Oxygen reduction reaction Metal-nitrogen/carbon Fuel cell

在线全文

学校读者我要写书评

暂无评论

量子极限下的能量耗散

Science Bulletin 2024年第9期69卷 1221-1227页

作者：李海龙江华孙庆丰谢心澄 International Center for Quantum materials School of PhysicsPeking UniversityBeijing 100871China Interdisciplinary Center for Theoretical Physics and Information Sciences(ICTPIS) Fudan UniversityShanghai 200433China Institute for Nanoelectronic Devices and Quantum Computing Fudan UniversityShanghai 200433China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of SciencesBeijing 100190China Hefei National Laboratory Hefei 230088China

Energy dissipation is of fundamental interest and crucial importance in quantum systems. However,whether energy dissipation can emerge without backscattering inside topological systems remains a question. As a hallmark, we propose a microscopic picture that illustrates energy dissipation in the quantum Hall(QH) plateau regime of graphene. Despite the quantization of Hall, longitudinal, and two-probe resistances(dubbed as the quantum limit), we find that the energy dissipation emerges in the form of Joule heat. It is demonstrated that the non-equilibrium energy distribution of carriers plays much more essential roles than the resistance on energy dissipation. Eventually, we suggest probing the phenomenon by measuring local temperature increases in experiments and reconsidering the dissipation typically ignored in realistic topological circuits.

关键词： Energy dissipation Topological systems Non-equilibrium energy distribution Chern insulators Quantum limit

Enhancement of shear stability of a Fe-based amorphous alloy using electrodeposited Ni layers

在线全文

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2018年第12期34卷 2283-2289页

作者： Y.C.Wang X.M.Luo L.J.Chen H.W.Yang B.Zhang G.P.Zhang school of materials Science and Engineering Shenyang University of Technology Shenyang National Laboratory for materials Science Institute of Metal ResearchChinese Academy of Sciences Key Laboratory for Anisotropy and Texture of materials Ministry of EducationSchool of Materials Science and EngineeringNortheastern University

Tensile and fracture behaviors of sandwich-structured composites consisting of a Fe-based amorphous layer with a constant thickness and ultrafine-grained Ni layers with different thicknesses were investigated. The results indicate that the initiation and the stable propagation of the shear band in the amorphous layer was dominated by the Ni layers due to their strong constraint role. The catastrophic fracture of the amorphous layer was postponed in the sandwich composites through properly increasing the constrained Ni layer thickness, which effectively decreased the shear stress on the shear fracture planes of the amorphous layer, and thus led to stable propagation of the primary SB characterized by the increase in the smooth region size of the shear band.

关键词： Sandwich-structured composites Amorphous alloy Shear stability Plasticity Fracture

Effect of yttrium on microstructure and mechanical properties of laser clad coatings reinforced by in situ synthesized TiB and TiC

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2011年第5期29卷 477-483页

作者：李军王慧萍李曼萍于治水 school of materials Engineering Shanghai University of Engineering Science

Titanium-based composite coatings with and without Y particles were deposited by laser cladding on Ti6Al4V substrates. Solidification microstructure,phase constituents and distribution of the reinforcements with different morphologies,were investigated by X-ray diffractometer （XRD）,scanning electron microscopy （SEM） and electron probe micro analyzer （EPMA）. In addition,the effects of the addition of Y on mechanical properties （in terms of microhardness and the cracking susceptibility） were also highlighted. The results showed that the coatings were composed of α-Ti cellular dendrites,coarse needle-shaped TiB phase and an eutectic in which a large number of needle-shaped TiB whiskers and a few equiaxial TiC particles were uniformly embedded. Y was not stable and was transformed into Y2O3 during laser cladding. The addition of Y could refine the microstructure of the coating by hastening the spheroidization of primary phase structure. Moreover,it could also decrease the activity of carbon and prevent solute atoms from traversing the interface and moving into primary phase structure,namely,increase the fraction volume of TiC in the coating. All of there factors made the cracking susceptibility of the coating containing Y reduced on the premise that microhardness of the coating was increased. Microhardness of the coating without Y ranged from HV 875.6 to HV 659.8,the average microhardness was about HV 747.9. For the coating with Y,microhardness changed from HV 876.5 to HV 741.5 and the average michardness was about HV 795.3. Fracture toughness of the upper,middle,bottom and interface of the coating without Y were 6.33,8.91,11.94 and 11.93 MPa.m1/2. Fracture toughness of the similar positions of the coating with Y were 8.58,12.93,13.81,17.11 MPa.m1/2,respectively. The coating with Y presented higher microhardness and fracture toughness in comparison with that without Y. Obviously,the addition of Y had a very positive effect on the microstructure and mechanical properties

关键词： coating laser cladding in situ synthesis microstructure mechanical properties rare earths

Phase,microstructure and compressive properties of refractory high-entropy alloys CrHfNbTaTi and CrHfMoTaTi

在线全文

学校读者我要写书评

暂无评论

International Journal of Minerals,Metallurgy and materials 2022年第6期29卷 1231-1236页

作者： Jiaojiao Yi Fuyang Cao Mingqin Xu Lin Yang Lu Wang Long Zeng Laboratory of Advanced Multicomponent materials School of Mechanical EngineeringJiangsu University of TechnologyChangzhou 213001China school of materials Science and Engineering Jiangsu UniversityZhenjiang 212013China school of materials Science and Engineering Jiangsu University of TechnologyChangzhou 213001China school of materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China

New refractory high-entropy alloys,CrHfNbTaTi and CrHfMoTaTi,derived from the well-known HfNbTaTiZr alloy through principal element substitution were prepared using vacuum arc *** phase components,microstructures,and compressive properties of the alloys in the as-cast state were *** showed that both alloys were composed of BCC and cubic Laves *** terms of mechanical properties,the yield strength increased remarkably from 926 MPa for HfNbTaTiZr to 1258 MPa for CrHfNbTaTi,whereas a promising plastic strain of around 15.0%was retained in *** morphology and composition of the network-shaped interdendritic regions were closely related to the improved mechanical properties due to elemental *** were surrounded by an incompact interdendritic shell after Mo incorporation,which deteriorated yield strength and accelerated brittleness.

关键词： refractory high-entropy alloys phase structure microstructure yield strength plastic strain

Optimization of Grain Boundary Character Distribution in Fe-18Cr-18Mn-0.63N High-Nitrogen Austenitic Stainless Steel

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2013年第5期26卷 497-502页

作者： Feng SHI Xiaowu LI Yutong HU Chuan SU Chunming LIU Institute of materials Physics and Chemistry College of Sciences Northeastern University school of materials and Metallurgy Northeastern University

Grain boundary engineering（GBE） is a practice of improving resistance to grain boundary failure of the material through increasing the proportion of low Σ coincidence site lattice（CSL） grain boundaries（special grain boundaries） in the grain boundary character distribution（GBCD）. The GBCD in a cold rolled and annealed Fe-18Cr-18Mn-0.63N high-nitrogen austenitic stainless steel was analyzed by electron back scatter difraction（EBSD）. The results show that the optimization process of GBE in the conventional austenitic stainless steel cannot be well applied to this high-nitrogen austenitic stainless steel. The percentage of low ΣCSL grain boundaries could increase from 47.3% for the solid solution treated high-nitrogen austenitic stainless steel specimen to 82.0% for the specimen after 5% cold rolling reduction and then annealing at 1423 K for 10 *** special boundaries of high proportion efectively interrupt the connectivity of conventional high angle grain boundary network and thus achieve the GBCD optimization for the high-nitrogen austenitic stainless steel.

关键词： High nitrogen austenitic stainless steel Grain boundary character distri-bution CSL grain boundary EBSD

Slip casting and pressureless sintering of Ti3AlC2

在线全文

学校读者我要写书评

暂无评论

Journal of Advanced Ceramics 2019年第3期8卷 367-376页

作者： Yimin GONG Wubian TIAN Peigen ZHANG Jian CHEN Yamei ZHANG Zhengming SUN Jiangsu Key Laboratory of Advanced Metallic materials School of Materials Science and EngineeringSoutheast UniversityNanjing211189China Jiangsu Key Laboratory of Construction materials School of Materials Scienceand EngineeringSoutheast UniversityNanjing211189China

Slip casting and subsequent pressureless sintering(PLS)allow the preparation of complex-shaped and large-sized Ti3AlC2 components for many potential *** behaviors of the suspensions,green compacts,and sintered samples of Ti3AlC2 were studied in this *** optimized condition of 1 wt%of arabic gum as dispersant at pH=10 results in a Ti3AlC2 suspension for slip casting Ti3AlC2 green compacts without macro defects or *** sintering temperature and Al4C3 embedding powder are found to dominate the properties of the sintered Ti3AlC2 *** Ti3AlC2 sample sintered at 1450℃for 1.5 h with Al4C3 embedding powder reaches the best properties,namely 95.3%relative density,hardness of 4.18 GPa,thermal conductivity of 29.11W·m-1·K-1,and electrical resistivity of 0.39μΩ·*** findings in this work may pave the way for the application of MAX phases with large size and complex shape.

关键词： slip casting pressureless sintering(PLS) properties Ti3AlC2