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Thermal reffusivity: uncovering phonon behavior, structural defects, and domain size

Yangsu XIE, Bowen ZHU, Jing LIU, Zaoli XU, Xinwei WANG

《能源前沿(英文)》 2018年 第12卷 第1期   页码 143-157 doi: 10.1007/s11708-018-0520-z

摘要: To understand the relation between different nanostructures and thermal properties, a simple yet effective model is in demand for characterizing the underlying phonons and electrons scattering mechanisms. Herein, we make a systematic review on the newly developed thermal reffusivity theory. Like electrical resistivity which has been historically used as a theory for analyzing structural domain size and defect levels of metals, the thermal reffusivity can also uncover phonon behavior, structure defects and domain size of materials. We highlight that this new theory can be used for not only metals, but also nonmetals, even for amorphous materials. From the thermal reffusivity against temperature curves, the Debye temperature of the material and the ideal thermal diffusivity of single perfect crystal can be evaluated. From the residual thermal reffusivity at the 0 K limit, the structural thermal domain (STD) size of crystalline and amorphous materials can be obtained. The difference of white hair and normal black hair from heat conduction perspective is reported for the first time. Loss of melanin results in a worse thermal protection and a larger STD size in the white hair. By reviewing the different variation of thermal reffusivity against decreasing temperature profiles, we conclude that they reflected the structural connection in the materials. Ultimately, the future application of thermal reffusivity theory in studying 2D materials and amorphous materials is discussed.

关键词: thermal reffusivity theory     phonon behavior     structure defects     structural thermal domain (STD) size     2D material     amorphous material    

Advances in chemical synthesis and application of metal-metalloid amorphous alloy nanoparticulate catalysts

WU Zhijie, LI Wei, ZHANG Minghui, TAO Keyi

《化学科学与工程前沿(英文)》 2007年 第1卷 第1期   页码 87-95 doi: 10.1007/s11705-007-0018-4

摘要: This paper reviews the advances in the chemical synthesis and application of metal-metalloid amorphous alloy nanoparticles consisting of transition metal (M) and metalloid elements (B, P). After a brief introduction on the history of amorphous alloy catalysts, the paper focuses on the properties and characterization of amorphous alloy catalysts, and recent developments in the solution-phase synthesis of amorphous alloy nanoparticles. This paper further outlines the applications of amorphous alloys, with special emphasis on the problems and strategies for the application of amorphous alloy nanoparticles in catalytic reactions.

Influence of using amorphous silicon stack as front heterojunction structure on performance of interdigitated

Rui JIA,Ke TAO,Qiang LI,Xiaowan DAI,Hengchao SUN,Yun SUN,Zhi JIN,Xinyu LIU

《能源前沿(英文)》 2017年 第11卷 第1期   页码 96-104 doi: 10.1007/s11708-016-0434-6

摘要: Interdigitated back contact-heterojunction (IBC-HJ) solar cells can have a conversion efficiency of over 25%. However, the front surface passivation and structure have a great influence on the properties of the IBC-HJ solar cell. In this paper, detailed numerical simulations have been performed to investigate the potential of front surface field (FSF) offered by stack of n-type doped and intrinsic amorphous silicon (a-Si) layers on the front surface of IBC-HJ solar cells. Simulations results clearly indicate that the electric field of FSF should be strong enough to repel minority carries and cumulate major carriers near the front surface. However, the over-strong electric field tends to drive electrons into a-Si layer, leading to severe recombination loss. The n-type doped amorphous silicon (n-a-Si) layer has been optimized in terms of doping level and thickness. The optimized intrinsic amorphous silicon (i-a-Si) layer should be as thin as possible with an energy band gap ( ) larger than 1.4 eV. In addition, the simulations concerning interface defects strongly suggest that FSF is essential when the front surface is not passivated perfectly. Without FSF, the IBC-HJ solar cells may become more sensitive to interface defect density.

关键词: amorphous silicon     front surface field     simulations     interdigitated back contact-heterojunction solar cells    

Thermodynamic study on dynamic water and organic vapor sorption on amorphous valnemulin hydrochloride

Jinbo OUYANG, Jingkang WANG, Yongli WANG, Qiuxiang YIN, Hongxun HAO

《化学科学与工程前沿(英文)》 2015年 第9卷 第1期   页码 94-104 doi: 10.1007/s11705-015-1460-3

摘要: The sorption of water and organic vapors on valnemulin hydrochloride was determined by dynamic vapor sorption at 25 °C. The adsorption-desorption behavior of water vapor and a series of organic vapors was investigated to probe the structural changes in valnemulin hydrochloride before and after sorption. The isothermal adsorption equilibrium data was evaluated using Guggenheim-Anderson-deBoer (GAB) and Brunauer-Emmett-Teller (BET) models. The BET model is applicable only at low relative pressures (0.1≤RP≤0.4) while the GAB model is applicable in the whole range of RPs (0.1≤RP≤0.9). The sorption kinetics at high RPs was determined by fitting the sorption data to the Avrami equation and the sorption content time relationship could be predicted by the Avrami equation. Finally, the possible sorption mechanism of valnemulin hydrochloride was also discussed.

关键词: valnemulin hydrochloride     water vapor     organic vapors     sorption     kinetics    

Hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol on NiB/SiO2 amorphous alloy catalyst

SONG Yun, LI Wei, ZHANG Minghui, TAO Keyi

《化学科学与工程前沿(英文)》 2007年 第1卷 第2期   页码 151-154 doi: 10.1007/s11705-007-0028-2

摘要: NiB/SiO amorphous alloy catalyst was prepared by power electroless plating method and characterized by induction coupled plasma (ICP), Brunauer Emmett Teller method (BET), transmission electron microscope (TEM) and X-ray diffraction (XRD) techniques. The catalytic performance of NiB/SiO was investigated for the hydrogenation of furfuryl alcohol (FA) to tetrahydrofurfuryl alcohol (THFA). The effects of operational conditions, such as reaction temperature, pressure, and stirring rate were carefully studied. The proper conditions were determined as the following: pressure 2.0 MPa, temperature 120?C and stirring rate 550 r/min. A typical result with FA conversion of 99% and THFA selectivity of 100% was obtained under such conditions, which was close to that over Raney Ni.

关键词: following     Brunauer     electroless     temperature     transmission    

>In situ growth of phosphorized ZIF-67-derived amorphous CoP/Cu2O@CF electrocatalyst

《化学科学与工程前沿(英文)》 2023年 第17卷 第10期   页码 1430-1439 doi: 10.1007/s11705-023-2320-1

摘要: Transition metal phosphides have been extensively studied for catalytic applications in water splitting. Herein, we report an in situ phosphorization of zeolitic imidazole frameworks (ZIF-67) to generate amorphous cobalt phosphide/ZIF-67 heterojunction on a self-supporting copper foam (CF) substrate with excellent performance for hydrogen evolution reaction (HER). The needle-leaf like copper hydroxide was anchored on CF surface, which acted as implantation to grow ZIF-67. The intermediate product was phosphorized to obtain final electrocatalyst (CoP/Cu2O@CF) with uniform particle size, exhibiting a rhombic dodecahedron structure with wrinkles on the surface. The electrochemical measurement proved that CoP/Cu2O@CF catalyst exhibited excellent HER activity and long-term stability in 1.0 mol·L–1 KOH solution. The overpotential was only 62 mV with the Tafel slope of 83 mV·dec–1 at a current density of 10 mA·cm–2, with a large electrochemical active surface area. It also showed competitive performance at large current which indicated the potential application to industrial water electrolysis to produce hydrogen. First-principle calculations illustrated that benefit from the construction of CoP/ZIF-67 heterojunction, the d-band center of CoP downshifted after bonding with ZIF-67 and the Gibbs free energy (ΔGH*) changed from –0.18 to –0.11 eV, confirming both decrease in overpotential and excellent HER activity. This work illustrates the efficient HER activity of CoP/Cu2O@CF catalyst, which will act as a potential candidate for precious metal electrocatalysts.

关键词: CoP/Cu2O@CF     electrocatalyst     phosphorization     HER     DFT    

Liquid metal material genome: Initiation of a new research track towards discovery of advanced energy

Lei WANG, Jing LIU

《能源前沿(英文)》 2013年 第7卷 第3期   页码 317-332 doi: 10.1007/s11708-013-0271-9

摘要: As the basis of modern industry, the roles materials play are becoming increasingly vital in this day and age. With many superior physical properties over conventional fluids, the low melting point liquid metal material, especially room-temperature liquid metal, is recently found to be uniquely useful in a wide variety of emerging areas from energy, electronics to medical sciences. However, with the coming enormous utilization of such materials, serious issues also arise which urgently need to be addressed. A biggest concern to impede the large scale application of room-temperature liquid metal technologies is that there is currently a strong shortage of the materials and species available to meet the tough requirements such as cost, melting point, electrical and thermal conductivity, etc. Inspired by the Material Genome Initiative as issued in 2011 by the United States of America, a more specific and focused project initiative was proposed in this paper—the liquid metal material genome aimed to discover advanced new functional alloys with low melting point so as to fulfill various increasing needs. The basic schemes and road map for this new research program, which is expected to have a worldwide significance, were outlined. The theoretical strategies and experimental methods in the research and development of liquid metal material genome were introduced. Particularly, the calculation of phase diagram (CALPHAD) approach as a highly effective way for material design was discussed. Further, the first-principles (FP) calculation was suggested to combine with the statistical thermodynamics to calculate the thermodynamic functions so as to enrich the CALPHAD database of liquid metals. When the experimental data are too scarce to perform a regular treatment, the combination of FP calculation, cluster variation method (CVM) or molecular dynamics (MD), and CALPHAD, referred to as the mixed FP-CVM-CALPHAD method can be a promising way to solve the problem. Except for the theoretical strategies, several parallel processing experimental methods were also analyzed, which can help improve the efficiency of finding new liquid metal materials and reducing the cost. The liquid metal material genome proposal as initiated in this paper will accelerate the process of finding and utilization of new functional materials.

关键词: liquid metal material genome     energy material     material discovery     advanced material     room-temperature liquid alloy     thermodynamics     phase diagram    

Robust topology optimization of multi-material lattice structures under material and load uncertainties

Yu-Chin CHAN, Kohei SHINTANI, Wei CHEN

《机械工程前沿(英文)》 2019年 第14卷 第2期   页码 141-152 doi: 10.1007/s11465-019-0531-4

摘要: Enabled by advancements in multi-material additive manufacturing, lightweight lattice structures consisting of networks of periodic unit cells have gained popularity due to their extraordinary performance and wide array of functions. This work proposes a density-based robust topology optimization method for meso- or macro-scale multi-material lattice structures under any combination of material and load uncertainties. The method utilizes a new generalized material interpolation scheme for an arbitrary number of materials, and employs univariate dimension reduction and Gauss-type quadrature to quantify and propagate uncertainty. By formulating the objective function as a weighted sum of the mean and standard deviation of compliance, the tradeoff between optimality and robustness can be studied and controlled. Examples of a cantilever beam lattice structure under various material and load uncertainty cases exhibit the efficiency and flexibility of the approach. The accuracy of univariate dimension reduction is validated by comparing the results to the Monte Carlo approach.

关键词: robust topology optimization     lattice structures     multi-material     material uncertainty     load uncertainty     univariate dimension reduction    

工程材料研究中科学问题的思考

于翘

《中国工程科学》 1999年 第1卷 第3期   页码 1-4

摘要:

在不少场合下,航天用工程材料处在极端条件下工作,这就对材料提出许多特殊的要求,虽然国内外有一定的研究积累,但对更精确的模型和符合特定材料的损伤的状态方程,有待深一步研究。如高级弹头再入时气动加热和粒子云侵蚀以及两者耦合效应引起弹头防护材料增大后退量的问题;空中垃圾和微流星的高速碰撞对航天器的威胁;特别是核爆和激光武器对材料的损伤和破坏,实质上是辐射引起的热击波层裂破坏,这些都属于超高速碰撞对材料的响应问题。天线罩材料、吸波材料、红外隐身材料、电磁屏蔽材料都是具有不同波长电磁波的电磁功能材料,它们对固体介质的穿透、吸收、反射等会产生响应,不同的电磁功能材料,其宏观性能的物理参量不同,但有几个参量是通用的,如介电常数、磁导率和损耗角正切,搞清这些参量与材料微观结构的关系,可以为材料设计和材料创新提供科学依据。

关键词: 天线罩材料     吸波材料     红外隐身材料     电磁兼容材料    

Zr66Al9Cu16Ni9块体非晶合金制备工艺研究

阮许平,阮宏伟

《中国工程科学》 2004年 第6卷 第5期   页码 76-78

摘要:

运用真空电弧炉熔炼合金制备试样,采用三种不同的方法对金属熔体进行处理,试样的X射线衍射晶化相分析结果表明,B2O3和Na2SiO3的混合物与所选组分的熔体发生了反应,不适合作Zr基合金的包裹物;组分为CaF2(45%),AlF3(50%),CaO(5%)以及微量的TiO2的氟盐,由于该净化剂与所选的组分发生了反应,不适合Zr基合金的净化;设备的高真空度、原材料成分的高纯度是促进合金形成非晶态的重要因素。

关键词: 块体非晶合金     制备工艺     玻璃     熔盐     真空度    

Subsurface damage pattern and formation mechanism of monocrystalline -GaO in grinding process

《机械工程前沿(英文)》 2022年 第17卷 第2期 doi: 10.1007/s11465-022-0677-3

摘要: Monocrystalline beta-phase gallium oxide (β-Ga2O3) is a promising ultrawide bandgap semiconductor material. However, the deformation mechanism in ultraprecision machining has not yet been revealed. The aim of this study is to investigate the damage pattern and formation mechanism of monocrystalline β-Ga2O3 in different grinding processes. Transmission electron microscopy was used to observe the subsurface damage in rough, fine, and ultrafine grinding processes. Nanocrystals and stacking faults existed in all three processes, dislocations and twins were observed in the rough and fine grinding processes, cracks were also observed in the rough grinding process, and amorphous phase were only present in the ultrafine grinding process. The subsurface damage thickness of the samples decreased with the reduction in the grit radius and the grit depth of cut. Subsurface damage models for grinding process were established on the basis of the grinding principle, revealing the mechanism of the mechanical effect of grits on the damage pattern. The formation of nanocrystals and amorphous phase was related to the grinding conditions and material characteristics. It is important to investigate the ultraprecision grinding process of monocrystalline β-Ga2O3. The results in this work are supposed to provide guidance for the damage control of monocrystalline β-Ga2O3 grinding process.

关键词: monocrystalline beta-phase gallium oxide     grinding process     subsurface damage     nanocrystals     amorphous phase    

A novel approach to minimizing material loss for computer numerical control flank-regrinding of worn

《机械工程前沿(英文)》 2023年 第18卷 第3期 doi: 10.1007/s11465-023-0757-z

摘要: Flanks of end mills are prone to wear in a long machining process. Regrinding is widely used in workshops to restore the flank to an original-like state. However, the traditional method involves material waste by trial and error and dramatically decreases the potential regrinding. Moreover, over-cut would happen to the flutes of worn cutters in the regrinding processes because of improper wheel path. This study presented a new approach to planning the wheel path for regrinding worn end mills to minimize material loss and recover the over-cut. In planning, a scaling method was developed to determine the maximum size of the new cutter according to the similarity of cutter shapes before and after regrinding. Then, the wheel path is first generated by envelope theory to regrind the worn area with a four-axis computer numerical control grinder according to the new size of cutters. Moreover, a second regrinding strategy is applied to recover the flute shape over-cut in the first grinding. Finally, the proposed method is verified by an experiment. Results showed that the proposed approach could save 25% of cutter material compared with the traditional method and ensure at least three regrinding times. This work effectively provides a general regrinding solution for the worn flank with maximum material-saving and regrinding period.

关键词: flank-regrinding     worn end mill     wheel position and orientation     material loss     over-cut    

A MATLAB code for the material-field series-expansion topology optimization method

《机械工程前沿(英文)》 2021年 第16卷 第3期   页码 607-622 doi: 10.1007/s11465-021-0637-3

摘要: This paper presents a MATLAB implementation of the material-field series-expansion (MFSE) topo-logy optimization method. The MFSE method uses a bounded material field with specified spatial correlation to represent the structural topology. With the series-expansion method for bounded fields, this material field is described with the characteristic base functions and the corresponding coefficients. Compared with the conventional density-based method, the MFSE method decouples the topological description and the finite element discretization, and greatly reduces the number of design variables after dimensionality reduction. Other features of this method include inherent control on structural topological complexity, crisp structural boundary description, mesh independence, and being free from the checkerboard pattern. With the focus on the implementation of the MFSE method, the present MATLAB code uses the maximum stiffness optimization problems solved with a gradient-based optimizer as examples. The MATLAB code consists of three parts, namely, the main program and two subroutines (one for aggregating the optimization constraints and the other about the method of moving asymptotes optimizer). The implementation of the code and its extensions to topology optimization problems with multiple load cases and passive elements are discussed in detail. The code is intended for researchers who are interested in this method and want to get started with it quickly. It can also be used as a basis for handling complex engineering optimization problems by combining the MFSE topology optimization method with non-gradient optimization algorithms without sensitivity information because only a few design variables are required to describe relatively complex structural topology and smooth structural boundaries using the MFSE method.

关键词: MATLAB implementation     topology optimization     material-field series-expansion method     bounded material field     dimensionality reduction    

A multiscale material model for heterogeneous liquid droplets in solid soft composites

《结构与土木工程前沿(英文)》 2021年 第15卷 第5期   页码 1292-1299 doi: 10.1007/s11709-021-0771-3

摘要: Liquid droplets in solid soft composites have been attracting increasing attention in biological applications. In contrary with conventional composites, which are made of solid elastic inclusions, available material models for composites including liquid droplets are for highly idealized configurations and do not include all material real parameters. They are also all deterministic and do not address the uncertainties arising from droplet radius, volume fraction, dispersion and agglomeration. This research revisits the available models for liquid droplets in solid soft composites and presents a multiscale computational material model to determine their elastic moduli, considering nearly all relevant uncertainties and heterogeneities at different length scales. The effects of surface tension at droplets interface, their volume fraction, size, size polydispersity and agglomeration on elastic modulus, are considered. Different micromechanical material models are incorporated into the presented computational framework. The results clearly indicate both softening and stiffening effects of liquid droplets and show that the model can precisely predict the effective properties of liquid droplets in solid soft composites.

关键词: liquid in solid     soft composite     computational modeling     multiscale model     heterogeneity    

Influence of soft rock-fill material as dam embankment with central bituminous concrete membrane

Peter TSCHERNUTTER

《结构与土木工程前沿(英文)》 2011年 第5卷 第1期   页码 63-70 doi: 10.1007/s11709-010-0016-3

摘要: This paper demonstrates the difficulties in determining the relevant material parameters for a valuation of the deformation behavior of the up- and downstream dam shell by means of an embankment dam of medium height. Laboratory as well as field tests on solid rock-fill material were performed before the beginning of construction. During the construction the properties of the available rock-fill changed from solid to soft materials. This gave rise to the necessity of adjusting the dam design of the downstream dam shoulder. Several times higher dam settlements as well as significant differential settlements between the up- and downstream dam shell were observed during construction and operation. Apart from this situation, the dam has been operated for nearly 20 years and the behavior of the water barrier has been very good.

关键词: embankment dam     bituminous concrete membrane     rock-fill material properties     deformation behavior    

标题 作者 时间 类型 操作

Thermal reffusivity: uncovering phonon behavior, structural defects, and domain size

Yangsu XIE, Bowen ZHU, Jing LIU, Zaoli XU, Xinwei WANG

期刊论文

Advances in chemical synthesis and application of metal-metalloid amorphous alloy nanoparticulate catalysts

WU Zhijie, LI Wei, ZHANG Minghui, TAO Keyi

期刊论文

Influence of using amorphous silicon stack as front heterojunction structure on performance of interdigitated

Rui JIA,Ke TAO,Qiang LI,Xiaowan DAI,Hengchao SUN,Yun SUN,Zhi JIN,Xinyu LIU

期刊论文

Thermodynamic study on dynamic water and organic vapor sorption on amorphous valnemulin hydrochloride

Jinbo OUYANG, Jingkang WANG, Yongli WANG, Qiuxiang YIN, Hongxun HAO

期刊论文

Hydrogenation of furfuryl alcohol to tetrahydrofurfuryl alcohol on NiB/SiO2 amorphous alloy catalyst

SONG Yun, LI Wei, ZHANG Minghui, TAO Keyi

期刊论文

>In situ growth of phosphorized ZIF-67-derived amorphous CoP/Cu2O@CF electrocatalyst

期刊论文

Liquid metal material genome: Initiation of a new research track towards discovery of advanced energy

Lei WANG, Jing LIU

期刊论文

Robust topology optimization of multi-material lattice structures under material and load uncertainties

Yu-Chin CHAN, Kohei SHINTANI, Wei CHEN

期刊论文

工程材料研究中科学问题的思考

于翘

期刊论文

Zr66Al9Cu16Ni9块体非晶合金制备工艺研究

阮许平,阮宏伟

期刊论文

Subsurface damage pattern and formation mechanism of monocrystalline -GaO in grinding process

期刊论文

A novel approach to minimizing material loss for computer numerical control flank-regrinding of worn

期刊论文

A MATLAB code for the material-field series-expansion topology optimization method

期刊论文

A multiscale material model for heterogeneous liquid droplets in solid soft composites

期刊论文

Influence of soft rock-fill material as dam embankment with central bituminous concrete membrane

Peter TSCHERNUTTER

期刊论文