检索结果-南通市图书馆

Electric-Arc Plasma Installation for Preparing Nanodispersed Carbon Structures

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2008年第4期10卷 484-490页

作者： P.STEFANOV D.gARLANOV g.vissokov ISMA Ltd.Samokovsko Chaussee Str. 1738 SofiaBulgaria Institute of Catalysis Bulgarian Academy of Sciences1113 SofiaBulgaria

An electric-arc plasma installation operated in the hidden anode arrangement is constructed and used for the preparation of carbon nanostructures. A contracted plasma arc generated by a plasma torch using an inert gas is used as heat source. The average mass temperature of arc is higher than 10^4 K, while its power density, which is directly transferred onto the electrode （anode）, is - 2 kW/mm^2. The anode contact area formed on the electrode moves against the arc by way of shifting the electrode and is hidden completely in the interior of plasma gas stream moving towards it. As a result of both the direct plasma attack and the opposite movement of streams in the hidden anode contact area, a temperature higher than 6000 K is reached. Thus, intensive vaporization takes place, which forms a saturated plasma-gas-aerosol phase of the initial material of electrode （anode）. This gas phase is mixed in and carried by the plasma stream. Over that mixed plasma stream, a controlled process of quenching （fixation） is carried out by twisted turbulent fluid streams. After the fixation, the resultant carbon nano-structures are caught by a filter and collected in a bunker.

关键词： electric-arc plasma installation nanodispersed carbon structures

Study of Nanodispersed Iron Oxides Produced in Steel Drilling by Contracted Electric-Arc Air Plasma Torch

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2008年第3期10卷 352-357页

作者： P.STEFANOV D.gALANOV g.vissokov D.PANEVA B.KUNEV I.MITOV ISMA Ltd. Samokovsko Chaussee Str. 1738 Sofia Bulgaria Institute of Catalysis Bulgarian Academy of Sciences Sofia Bulgaria

The optimal conditions on the plasma-forming gas flowrate, discharge current and voltage, distance between the plasma-torch nozzle and the metal plate surface for the process of penetration in and vaporization of steel plates by the contracted electric-arc air plasma torch accompanied by water quenching, were determined. The X-ray structural and phase studies as well as Mossbauer and electron microscope studies on the samples treated were performed. It was demonstrated that the vaporized elemental iron was oxidized by the oxygen present in the air plasma jet to form iron oxides （wiistite, magnetite, hematite）, which, depending on their mass ra- tios, determined the color of the iron oxide pigments, namely, beginning from light yellow, through deep yellow, light brown, deep brown, violet, red-violet, to black. A high degree of dispersity of the iron oxides is thus produced, with an averaged diameter of the particles below 500 nm, and their defective crystal structure form the basis of their potential application as components of iron-containing catalysts and pigments.

关键词： nanodispersed iron oxides preparation plasma torch

The Role of Nanodispersed Nitrides in the Sintering of Silicon Nitride Ceramics

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2010年第1期12卷 46-48页

作者： M.gEORgIEVA g.vissokov I.gRANCHAROV R.F.SILVA F.J.OLIVEIRA Department of Technology of Inorganic Substances University of Chemical Technology and Metallurgy Institute of Catalysis Bulgarian Academy of Sciences Ceramics and glass Eng. Department CICECO University of Aveiro

The synthesis of ceramics based on silicon nitride using nanopowders of TiN and Si3N4 as additives was studied. The ceramic compositions were pressurelessly sintered under ni- trogen atmosphere at different temperatures （1550℃, 1650℃ and 1750℃） with a heating rate of 10℃/min and a holding time of 2 h. The nanodispersed nitrides （NDN） were produced by electric-arc plasma synthesis and characterized. The ceramic composites obtained with nanoparticles of 1wt% to 5wt% TiN and 20wt% Si3N4 were characterized by scanning electron microscopy （SEM）, atom force microscopy （AFM） and energy-dispersive spectrometry （EDX）. The effect of the addition of nanodispersed powders on the mechanical properties and microstructure of Si3N4 ceramics was investigated.

关键词： silicon nitride ceramics nanocomposites nanopowders

Nanodispersed Oxides-Plasma-Chemical Synthesis and Properties

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2007年第5期9卷 603-610页

作者： gheorghi vissokov Katerina ZAHARIEVA Institute of Catalysis Bulgarian Academy of SciencesSofia 1113Bulgaria Chemistry Chair St.Ivan Rilski University of Mining and GeologySofia 1700Bulgaria

We discuss the plasma-chemical synthesis and the properties of transition metals oxides, Al2O3, SiO2, rare-earth oxides, oxides for ceramics and metal-ceramics, and oxides used as catalysts. Bearing in mind the indisputable advantages of using plasma-chemically synthesized nanodispersed oxides for the needs of various industrial fields, we set out to review the articles published in the past few years devoted to the problems of plasma-chemical synthesis and characterization of nanodispersed oxides.

关键词： plasma synthesis nanodispersed oxides properties

High-Temperature Thermodynamic Investigation of Nano-Dispersed Nitrides Obtained in Thermal Plasma

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2007年第2期9卷 174-176页

作者： M. gEORgIEVA g. vissokov Iv. gRANCHAROV L. BRAKALOV Department of Technology of Inorganic Substances University of Chemical Technology andMetal|urgy 8 K. Okhridski Blvd. 1756 Sofia Bulgaria

The nitrides of transient metals have a high hardness, thermal stability, remarkable wear resistance in aggressive chemical mediums, melted metals and alloys, high corrosion resistance, and low coefficient of electric resistance. Under the conditions of low-temperature argon plasma （LTP）, thermodynamic investigations were conducted in the process of obtaining of A1N, TiN and Si3N4 in a temperature range of 1000 K to 6000 K. To investigate the thermodynamic possibility of obtaining nitrides, a computer model was used which provided the equilibrium composition of gaseous and solid phases at different temperatures. The conditions for chemical equilibrium of the system were based on the minimization of gibbs＇ energy.

关键词： plasma-chemical treatment nitrides thermodynamic analysis

Plasma-Chemical Synthesis of Nanosized Powders-Nitrides,Carbides,Oxides,Carbon Nanotubes and Fullerenes

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2012年第11期14卷 980-995页

作者： Katerina ZAHARIEVA gheorghi vissokov Janis gRABIS Slavcho RAKOVSKY Institute of Catalysis Bulgarian Academy of Sciences Institute of Inorganic Chemistry Riga Technical University

In this article the plasma-chemical synthesis of nanosized powders （nitrides, car- bides, oxides, carbon nanotubes and fullerenes） is reviewed. Nanosized powders - nitrides, carbides, oxides, carbon nanotubes and fullerenes have been successfully produced using different techniques, technological apparatuses and conditions for their plasma-chemical synthesis.

关键词： plasma nanosized powders nitrides carbides oxides carbon nanotubes,fullerenes

Plasma-chemical Synthesis and Regeneration of Catalysts for CH_4 Steam Conversion

在线全文

学校读者我要写书评

暂无评论

Plasma Science and Technology 2002年第6期4卷 1551-1558页

作者： gheorghi P. vissokov Institute of Electronics Bulgarian Academy of Sciences 72 Tsarigradsko Chaussee1784 Sofia Bulgaria

We carried out experimental studies concerning the plasma-chemicalsynthesis(PCS) of a catalyst for CH_4 steam conversion and designed and built the equipment for PCSand/ or regeneration of spent catalyst for CH_4 steam conversion. Under the conditions of anelectric-arc low-temperature plasma (LTP), we studied the Ni-O-Al system and performed acomprehensive physicochemical analysis of the ultradispersed product obtained. It's the first timeworldwide when the conditions of plasma-chemical synthesis and/ or regeneration of CH_4 steamconversion catalysts under the conditions of electric-arc LTP are investigated depending on theplasma-chemical process (PCP) parameters and the plasma-chemical reactor (PCP) type (with CW-'coldwalls' T_W = 500 K or WW-'warm walls' T_W = 1500 K), samples with a specific surface of 120 m^2/gare obtained. Plasma-chemically synthesized and/ or regenerated samples have a homogenous chemicalcomposition similar to that the girdller (USA) conventional industrial catalyst. It is empiricallyestablished that the optimal temperature range in PCR for synthesis of samples with maximumdispersity is (2000～3000) K. Results from investigation on dynamics and kinetics ofplasma-chemically synthesized and / or regenerated catalysts for CH4 steam conversion show thatunder LTP conditions premises for the formation of catalyst compositions are established. They arereduced 3 to 4 times faster than their industrial analogues. High specific surface of the samples,homogenous composition, high rate of active chemical surface formed by reduction, faulty crystallattice of catalytically active phases and mostly high catalytic activity make them a potentialcompetitor with their industrial analogues for their probable production in catalyst shops.

关键词： plasma-chemical synthesis regeneration of catalysts CH_4 steamconversion

Stepping up after spinal cord injury:negotiating an obstacle during walking

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2025年第7期20卷 1919-1929页

作者： Alain Frigon Charly g.Lecomte Department of Pharmacology-Physiology Faculty of Medicine and Health SciencesUniversitéde SherbrookeCentre de recherche du Centre Hospitalier Universitaire de SherbrookeSherbrookeQCCanada

Every day walking consists of frequent voluntary modifications in the gait pattern to negotiate *** spinal cord injury,stepping over an obstacle becomes *** over an obstacle requires sensorimotor transformations in several structures of the brain,including the parietal cortex,premotor cortex,and motor *** information and planning are transformed into motor commands,which are sent from the motor cortex to spinal neuronal circuits to alter limb trajectory,coordinate the limbs,and maintain *** spinal cord injury,bidirectional communication between the brain and spinal cord is disrupted and animals,including humans,fail to voluntarily modify limb trajectory to step over an ***,in this review,we discuss the neuromechanical control of stepping over an obstacle,why it fails after spinal cord injury,and how it recovers to a certain extent.

关键词： biomechanics locomotion neurophysiology obstacle negotiation spinal cord injury

An SPH Framework for Earthquake-Induced Liquefaction Hazard Assessment of geotechnical Structures

在线全文

学校读者我要写书评

暂无评论

Computer Modeling in Engineering & Sciences 2025年第1期142卷 251-277页

作者： Sourabh Mhaski g.V.Ramana Department of Civil Engineering Indian Institute of Technology DelhiNew Delhi110016India

Earthquake-induced soil liquefaction poses significant risks to the stability of geotechnical structures *** understanding of the liquefaction triggering,and the post-failure large deformation behaviour is essential for designing resilient *** present study develops a Smoothed Particle Hydrodynamics(SPH)framework for earthquake-induced liquefaction hazard assessment of geotechnical *** coupled flowdeformation behaviour of soils subjected to cyclic loading is described using the PM4Sand model implemented in a three-phase,single-layer SPH framework.A staggered discretisation scheme based on the stress particle SPH approach is adopted to minimise numerical inaccuracies caused by zero-energy modes and tensile ***,non-reflecting boundary conditions for seismic analysis of semi-infinite soil domains using the SPH method are *** numerical framework is employed for the analysis of cyclic direct simple shear test,seismic analysis of a level ground site,and liquefaction-induced failure of the Lower San Fernando *** agreement for liquefaction triggering and post-failure behaviour demonstrates that the SPH framework can be utilised to assess the effect of seismic loading on field-scale geotechnical *** present study also serves as the basis for future advancements of the SPH method for applications related to earthquake geotechnical engineering.

关键词： Earthquake seismic liquefaction stress particle PM4Sand smoothed particle hydrodynamics(SPH)