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颗粒尺寸、挤压和时效时间对Sic颗粒增强Al-cu-Mg基复合材料微观结构及硬度的影响

粉末冶金材料科学与工程 2017年第1期22卷 26-32页

作者：沈茹娟王德高郭柏松宋旼中南大学深圳研究院深圳518057 中南大学粉末冶金国家重点实验室长沙410083

研究Si c颗粒尺寸、挤压和时效时间对粉末冶金法制备的Si c颗粒增强Al-cu-Mg基复合材料微观结构及硬度的影响。研究表明,挤压对复合材料的微观结构和硬度有重要影响,能够极大促进增强体在Al基体中的均匀分布和复合材料的致密化。挤压后... 详细信息

研究Si c颗粒尺寸、挤压和时效时间对粉末冶金法制备的Si c颗粒增强Al-cu-Mg基复合材料微观结构及硬度的影响。研究表明,挤压对复合材料的微观结构和硬度有重要影响,能够极大促进增强体在Al基体中的均匀分布和复合材料的致密化。挤压后的复合材料残留微孔减少,密度和硬度均得到显著提高。时效时间和Si c尺寸对复合材料中析出相的数量及尺寸有显著影响。采用较小尺寸的Si c作为增强体时,随时效时间延长,析出相在基体中均匀析出,没有明显长大,在时效12 h内没有出现峰时效。然而,采用较大尺寸的Si c作为增强体时,随时效时间延长,基体中的析出相不是很均匀,并有部分发生明显粗化,在同样的时效时间范围内出现了峰时效。

关键词： Al基复合材料 Si c 颗粒尺寸颗粒分布时效时间硬度

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Hardness of Pillared-Graphene Nanostructures via Indentation Simulation

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MRS ADVANcES 2017年第1期2卷 45-50页

作者： Sasaki, R. Shintani, K. Univ Electrocommun Dept Mech Engn & Intelligent Syst 1-5-1 Chofugaoka Chofu Tokyo 1828585 Japan

Pillared-graphene is one of nanocarbon hybrids. It consists of graphene sheets and carbon nanotubes (cNTs);the latter are bonded vertically to the former. In order to investigate the hardness of pillared-graphene, indentation simulations are performed using a molecular dynamics method. It is revealed that the hardness of pillared-graphene increases with increasing the diameter of the cNTs, whereas it decreases with increasing the distance between cNTs or temperature. Such tendencies can be understood by considering the deformations of graphene and cNTs individually.

关键词： c nano-indentation hardness

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Synthesis and characterization of novel activated carbon from Medlar seed for chromium removal: Experimental analysis and modeling with artificial neural network and support vector regression

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Resource-Efficient Technologies 2017年第3期3卷 236-248页

作者： Mostafa Solgi Tahereh Najib Shahyar Ahmadnejad Bahram Nasernejad Chemical Engineering Department Babol Noshirvani University of Technology P.O. Box 484 *** Babol Iran Chemical Engineering Department Amirkabir University of Technology (Tehran Polytechnic) P.O. Box 15875-4413 Tehran Iran Electrical Engineering Department Babol Noshirvani University of Technology P.O. Box 15875-4413 Babol Iran

In this study, for the first time the activated carbon has been produced from medlar seed (Mespilus germanica) via chemical activation with KOH. The carbonization process was carried out at different temperatures of 450, 550, 650 and 750 °c. The Nitrogen adsorption-desorption, Fourier transform infrared spectroscopy (FTIR) and Field Emission Scanning Electron Microscope (FESEM) analyses were carried out on the adsorbents. The effect of operating parameters, such as pH, initial concentration of cr(VI), adsorbent dosage and contact time were investigated. The experimental data showed better agreement with the Langmuir model and the maximum adsorption capacity was evaluated to be 200 mg/g. Kinetic studies indicated that the adsorption process follows the pseudo second-order model and the chemical reaction is the rate-limiting step. Thermodynamic parameters showed that the adsorption process could be considered a spontaneous (ΔG < 0), endothermic (ΔH > 0) process which leads to an increase in entropy (ΔS > 0). The application of support vector machine combined with genetic algorithm (SVM-GA) and artificial neural network (ANN) was investigated to predict the percentage of chromium removal from aqueous solution using synthesized activated carbon. The comparison of correlation coefficient (R 2 ) related to ANN and the SVR-GA models with experimental data proved that both models were able to predict the percentage of chromium removal, by synthetic activated carbon while the SVR-GA model prediction was more accurate.

关键词： Activated carbon chromium removal Medlar seed Artificial neural network Support vector regression qe (mg/g) adsorption capacity at equilibrium time qe,cal (mg/g) theoretical equilibrium adsorption capacity k1 (1/min) pseudo-first order adsorption rate constant k2 (g/mg min) pseudo-second order adsorption rate constant kid (g/mg min) intra-particle diffusion rate constant c constant indicating thickness of the boundary lay qmax (mg/g) maximum adsorption capacity B (L/g) Langmuir isotherm constant n adsorption intensity KF (mg/g) Freundlich isotherm constant ΔS o (J/mol K) standard entropy change ΔGo (kJ/mol) Gibbs free energy change ΔHo (kJ/mol) standard enthalpy change R (j/mol K) universal gas constant T (K) temperature kd (ml/g) distribution coefficient Δq (%) normalized standard deviation

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Recent advances in guest effects on spin-crossover behavior in Hofmann-type metal-organic frameworks

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coordination chemistry Reviews 2017年 335卷 28-43页

作者： Zhao-Ping Ni Jun-Liang Liu Md. Najbul Hoque Wei Liu Jin-Yan Li Yan-cong chen Ming-Liang Tong Key Laboratory of Bioinorganic and Synthetic Chemistry of Ministry of Education School of Chemistry Sun Yat-Sen University Guangzhou 510275 PR China

The incorporation of spin-crossover (ScO) properties into metal-organic frameworks (MOFs) is an appealing subclass of multifunctional MOFs with potential applications in molecular sensing. This review focuses on the design of ScO Hofmann-type MOFs, with emphasis on the guest effect on their ScO properties. The influences of guest size, dielectric constant, π ⋯ π interaction, hydrogen bonding interactions, weak X⋯M′ covalent bonding, and chemical reaction on the ScO properties of Hofmann-type MOFs are systematically explored. Further enhancements of sensing properties are also illustrated.

关键词： azpy trans -4,4′-azopyridine pz pyrazine py pyridine 3-Fpy 3-fluoropyridine 3-NH 2 py 3-aninopyridine phpy 4-phenylpyridine bpac bis(4-pyridyl)acetylene bpeben 1,4-bis(4-pyridylethynyl)-benzene dpsme 4,4′-di(pyridylthio)methane bipytz 3,6-bis(4-pyridyl)-1,2,4,5-tetrazine bpmp 1,4-bis(pyridin-4-ylmethyl)piperazine bpp 2,5-bis(pyrid-4-yl)pyridine dpb 1,4-di(pyridin-4-yl)benzene bz benzene Ac acetone Acn acetonitrile IBz iodobenzene MeOH methanol EtOH ethanol Tol toluene fur furan pyr pyrrole thio thiophene Mal maleic anhydride HMal Maleic acid bpbd 2,3-bis(4′-pyridyl)-2,3-butanediol n -PrOH 1-propanol c 6 H 12 cyclohexane s -BuOH sec -butanol i -BuOH isobutanol i -PrOH isopropanol naph naphthalene anth anthracene TclBz 1,2,4-trichlorobenzene clBz chlorobenzene BrBz bromobenzene dpe 1,2-di(4-pyridyl)ethylene dpa 1,2-di(4-pyridyl)ethane bbz bibenzyl stb stilbene bpb bis(4-pyridyl)butadiyne bipydz 3,6-bis(4-pyridyl)-1,2-diazine c 7 H 8 2,5-norbornadiene Spin-crossover Host-guest interaction Hofmann-type Metal-organic frameworks

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Design and commissioning of a thermal stability test-rig for mixtures as working fluids for ORc applications

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Energy Procedia 2017年 129卷 176-183页

作者： L. Keulen c. Landolina A. Spinelli P. Iora c. Invernizzi L. Lietti A. Guardone Department of Aerospace Science & Technology Politecnico di Milano Via La Masa 35 20156 Milano Italy Department of Mechanical Engineering Politecnico di Milano Via La Masa 1 20156 Milano Italy Energy Department Politecnico di Milano Via Lambruschini 4 20156 Milano Italy Department of Mechanical and Industrial Engineering University of Brescia Via Branze 38 25121 Brescia Italy

A novel test-rig for studying the thermal stability of mixtures as working fluids for ORc applications was designed and commissioned at the Laboratory of compressible-fluid dynamics for Renewable Energy Applications (cREA) of Politecnico di Milano, in collaboration with the University of Brescia. The set-up is a standard one, in which a vessel containing the fluid under scrutiny is placed in a vertical oven for ~ 100 hours at a constant temperature T = T stress . During the test, the pressure P is monitored to detect thermal decomposition of the fluid. After the test, the vessel is placed in a controlled thermal bath, where the pressure is measured at different value of the temperature T , with T < T stress and T < T c ( T c critical temperature). The resulting isochoric pressure-temperature dependence is compared to that obtained before the fluid underwent thermal stress. If departure from the initial fluid behavior is observed, significant thermal decomposition occurred and a chemical analysis of the decomposition products is carried out using gas chromatography and mass spectroscopy. The novelty of the set-up is the possibility of taking samples of both liquid and vapor phases of the fluid, a capability that was introduced to study thermal decomposition of mixtures, whose composition depends on the pressure and temperature, as well as to capture the more volatile products of thermal decomposition of pure fluids and mixtures. Preliminary experimental results are reported for the pure siloxane fluid MDM (Octamethyltrisiloxane, c 8 H 24 O 2 Si 3 ).

关键词： Thermal stability Working fluids for ORc applications Binary mixtures of siloxane fluids MM (Hexamethyldisiloxane c 6 H 18 OSi 2 ) MDM (Octamethyltrisiloxane c 8 H 24 O 2 Si 3 ) ORc applications

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Influence of Pretreatment on Kinetics at carbon Electrodes and consequences for Flow Battery Performance

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MRS ADVANcES 2017年第21-22期2卷 1131-1142页

作者： Buckley, D. N. Bourke, A. Lynch, R. P. Quill, N. Miller, M. A. Wainright, J. S. Savinell, R. F. Univ Limerick Bernal Inst Dept Phys & Energy Limerick Ireland Case Western Reserve Univ Dept Chem Engn Cleveland OH 44106 USA Waterford Inst Technol Sch Engn Waterford Ireland

Using cyclic voltammetry (cV) and electrochemical impedance spectroscopy (EIS), it was shown for four different types of carbon that electrode treatments at negative potentials enhance the kinetics of V-IV-V-V and inhibit the kinetics of V-II-V-III while electrode treatments at positive potentials inhibit the kinetics of V-IV-V-V and enhance the kinetics of V-II-V-III. These observations may explain conflicting reports in the literature. The potentials required for activation and deactivation of electrodes were examined in detail. The results suggest that interchanging the positive and negative electrodes in a vanadium flow battery (VFB) would reduce the overpotential at the negative electrode and so improve the performance. This is supported by flow-cell experiments. Thus, periodic catholyte-anolyte interchange, or equivalent alternatives such as battery overdischarge, show promise of improving the voltage efficiency of VFBs.

关键词： kinetics c V

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Thermal Rectification characteristics of Graphene Nanoribbons of Asymmetric Geometries

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MRS ADVANcES 2017年第1期2卷 15-20页

作者： Iwata, T. Shintani, K. Univ Electrocommun Dept Mech Engn & Intelligent Syst 1-5-1 Chofugaoka Chofu Tokyo 1828585 Japan

The rectification of heat in graphene nanoribbons (GNRs) of asymmetric geometries is investigated by means of nonequilibrium molecular dynamics (NEMD). Two kinds of geometries of GNRs are addressed;a trapezoidal or T-shaped step is inserted halfway through a GNR in its longitudinal direction. The thermal conductivities (Tcs) of the GNRs in the two longitudinal directions, forward and backward, are calculated making their width and temperature change. It is revealed that the thermal rectification ratio (TRR) of T-shaped GNRs are larger than those of trapezoidal GNRs and that the characteristics of heat transport in such asymmetric GNRs can be understood by considering the local phonon density of states (DOSs).

关键词： c nanoscale thermal conductivity

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Procedure Selecting Pumps Running as Turbines in Micro Hydro Plants

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Energy Procedia 2017年 126卷 549-556页

作者： S. Barbarelli M. Amelio G. Florio N.M. Scornaienchi Department of Mechanical Energy and Management Engineering University of Calabria – Rende (Italy)

The authors present a combined method using statistical and numerical models for selecting a pump running as turbine in micro hydro plants. The data of the site (head and capacity) allow calculating two coefficients, c Q and c H , which identify the pump to use successfully as turbine in that place. A one dimensional model, starting from data available on the pumps manufacturers catalogues, reconstructs a virtual geometry of the PAT, then calculates the performances curves, head vs. capacity, efficiency vs. capacity. The procedure has been applied with the aim to select a PAT recovering energy from a pipeline whose characteristic curve is known.

关键词： Hydropower Experimental measures Pump as Turbine c Q - c H conversion factors One-dimensional model case study

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Highly conductive Wire: cu carbon Nanotube composite Ampacity and Metallic cNT Buckypaper conductivity

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MRS ADVANcES 2017年第2期2卷 71-76页

作者： de Groh, Henry c., III NASA Glenn Res Ctr Cleveland OH 44135 USA

carbon nanotube (cNT) composites are being explored to improve the conductivity and density of electrical wire used in aviation. Presented are the current carrying capacity of a cNT-cu composite and Roman spectroscopy and electrical conductivity of Buckypaper (BP) made of normal and sorted 95% metallic cNT (m-cNT). The ampacity of the cu-cNT composite was 3.8% lower than pure cu. This is significant because it is not in agreement with high cNT ampacity claims. The average conductivity of the cNT in the sorted, 95% metallic BP was 2.5 times higher than the cNT in the un-sorted BP. This shows the importance of the intrinsic cNT conductivity as opposed to interfacial resistances and that the conductivity of the semiconductor cNT present in the un-sorted BP must be much lower than the conductivity of m-cNT. The high conductivity of the sorted BP provides proof that conductivity improvements in cNT composites can be made by the use of sorted, highly conductive m-cNT.

关键词： c cu composite

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Stroke Due to Hypercoagulable State can Mimic Multiple Sclerosis: A case Report

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World Journal of Neuroscience 2017年第3期7卷 267-274页

作者： Niknam Zahra Saadat Alireza Nabavi Seyed-Massood Morsali Damineh Hatami-Sadabadi Farhad Kheirkhahan Meghdad Mehdipour Baharak Neurologist Neurology Department University of Baghiatalahaazam Tehran Iran University of Baghiatalahaazam Tehran Iran Department of Regenerative Biomedicine Cell Science Research Center Royan Institute for Stem Cell Biology and Technology ACECR Tehran Iran Senior postdoctoral fellow Neurology department Texas University Huston Texas USA General physician Kheradmand Clinical Research Center Medical Affairs Division Actoverco Pharmaceutical Company Tehran Iran

Introduction: Stroke is the second major cause of mortality worldwide and in several cases, and it may lead to disability. Factor V Leiden is a common genetic thrombophilia, which causes activated protein c (APc) resistance. Hyperhomocysteinemia and factor V Leiden deficiency, two independent coagulopathy factors, can lead to venous and arterial infarctions in multiple small and large arteries and veins anywhere in the body. case Report: Here, we report a unique case in which both hyperhomocysteinemia and factor V Leiden deficiency are documented together with MTHFR (c677T) (Methylene Tetra Hydro Folate Reductase) gene polymorphism and activated protein c resistance respectively. conclusion: More interestingly, the mode of presentation in this case highly resembled that of progressive multiple sclerosis;all signs and symptoms slowly progressed without any systemic signs at first few years. Further studies needed to assess current outcomes.

关键词： Hyperhomocysteinemia Thrombophilia V MTHFR (c677T) Gene Polymorphism Activated Protein c Resistance Multiple Sclerosis

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