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Volume 7#2 2015 |
КОМПОЗИТЫ и НАНОСТРУКТУРЫ COMPOSITES and NANOSTR UCTURES |
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CONTENTS |
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NEW
MATERIALS FOR MACHINERY ENGINEERING: SILICON CARBIDE REINFORCED WITH
DIAMOND PARTICLES........................................................................................................................................................71 A process
of obtaining composites containing silicon carbide matrix and diamond
particles (C/SiC) is disclosed. The process differs
from well known fabrication technologies of producing super materials, such
as diamond or cubic boron nitride by providing a possibility to make elements of both complicated shapes and large
sizes. This allows consider a new type of the composite
as structured material of unique combination of high wear resistance,
rigidity, thermal conductivity and low thermal expansion (p. 61-71; fig. 8). S.A.Firstov, V.F.Gorban, N.A.Krapivka, E.P.Pechkovsky, M.V.Karpets AN EFFECT OF
RATIO OF o-PHASE AND FCC-PHASE TO ELECTRONIC CONCENTRATION OF CAST
TWO-PHASE HIGH-ENTROPY
ALLOYS......................................................................................................................72 Eleven multicomponent two-phase high-entropy alloys (HEAs) of
mainly equiatomic composition are studied. The
alloys include 5 to 7 elements V, Cr, Mo, Mn, Fe, Co, Ni,
Cu (Smix=13.4-16.2 J/mol-K). They
contain intermetallic polycomponent
o-phase and FCC-substitutional solid solution in quantity
from 0 up to 100 mass %. Electronic concentrations Csd
of alloys are within 6.9 - 8.2
electron/atom. Dependencies
between three characteristics of alloys chemical composition, its calculated
value of electronic concentration Csd and experimentally obtained ratio of o-phase to FCC-phase are evaluated. It is
shown that the value of electronic concentration, Csd,
for HEAs of a type under consideration reflects not only their chemical and phase structure, but also a quantitative ratio of o-phase and the FCC-phase in them.
Using electronic concentration of
individual elements and thermodynamic characteristics of o-forming pairs in alloys, a
physical interpretation of their effect on a change in quantity of o-phase and FCC-phase in HEAs is
suggested. An effect of
quantity of o-phase in HEAs and individual elements in them on
hardness, elastic modulus and elastic deformation is measured by method of tool automatic indentation (p. 72-84; fig. 3). Deev I.S., Belov P. A., Kobets
L.P. EXPERIMENTAL
NONCLASSICAL EFFECTS AS A BASE OF «THEORY OF TORSIONS» IN
FRACTURE MECHANICS OF POLYMERIC
COMPOSITES....................................................................................................85 Results of
fractographic observations of a new «torsion» mode
of fracture of the polymer matrix which characteristic feature is fragmentation
and localization of so called arrays of material of local areas «torsions» of
various forms in the loaded polymers and polymer matrix composites are generalized. It is shown that the «torsion»
mode of fracture in various types of loading is universal
and characteristic for polymer matrix reinforced with various fibres (carbon, glass, organic etc.) nanomodified
polymers, and is observed on both meso- and microlevels. The brightest nonclassical
effects, which can be formalized to construct on their basis «a torsion's theory», are chosen and offered for discussion. It
is found that for each mode of cracks there are two submodes, at which crack surfaces can be
either rough, or mirror like. There are exist non-fractured torsions, which
preserve their microstructure. Torsions can be of various shapes, spiral,
cylindrical, conical etc. depending on boundary conditions on their ends. Obtained experimental data present a diverse and interesting base
for theoretical models of torsions formation and fracture mechanics of polymers (p. 85-96; fig. 9). V.S.
Zarubin, G.N. Kuvyrkin,
I.Y. Savelyeva ELASTIC
PROPERTIES OF A COMPOSITE WITH LAMELLAR ANISOTROPIC INCLUSIONS.............................................97 Upper and
lower boundaries values of the elastic volume and shear moduli
of a composite with anisotropic inclusions of a lamellar form are obtained by using the variation approach. The mathematical model
of interaction of the inclusions and with isotropic linearly elastic medium, moduli of
elasticity of which are to be determined is constructed. With the use of this
model, dependences
predicting elastic properties of the composites with anisotropic lamellar
inclusions (including in the form of nanostructural elements) are obtained by a self-comistancy method (p. 97-108; fig. 4). S.M.Nikulin, A.A.Tashkinov, V.E.Shavshukov, A.V.Rozhkov AN EFFECT
OF MODIFICATION OF THE CARBON FABRIC SKELETON BY MWCNTS ON THE
PYROLYTIC CARBON SATURATION STAGE IN THE PROCESS OF FABRICATION CARBON-CARBON
COMPOSITE
MATERIAL.........................................................................................................................
109 A way of
fabrication nanomodified carbon-carbon composite
material, carbon-fiber preform with pyrolytic carbon deposited isothermal
method, wherein the catalyst particles formed on the surface of carbon fibers
by the thermal decomposition of compositions
based on salts of the catalytically active metal and reducing and nanomodification carbon-fiber preforms carried synthesis of multi-walled carbon nanotubes
by chemical vapor deposition. Density and open porosity of the material obtained were measured. According to the research have been
identified depending on the effect of carbon nanotubes and catalysts for the process of
isothermal saturation of pyrolytic carbon (p.
109-114; fig. 1). N.A.Popova, A.I.Drachev, G.V.Stepanov, R.A.Sadykov GRAPHENE MICROTI
BESDERIVED FROM POLYACRYLONITRILE
PRECURSOR.............................................................115 Single-walled
carbon microtubes with diameter of 0.5-3 mm and length of more then 1000 mm were produced by thermostabilization and subsequent carbonization of polyacrylonitrile
(PAN) fine powder. Structure and dimensions of tubes were studied by Scanning
Electron Microscopy; two-dimensional graphene
structure of tube walls were difined by X-ray
diffraction (p. 115- 120; fig.
7). |
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© ISSP RAS «COMPOSITES and NANOSTRUCTURES» 2015 |
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