Abstract: Polycrystalline diamond layers are mostly used in various fields of industrial application.
Mechanical tension is generated due to the different heat expansion coefficients of the
substrate and the layer, which leads to fracturing in some cases. In this work a homogeneous
polycrystalline diamond structure has been deposited on Si/SiO2 substrate by microwave
assisted CVD method (MW-PECVD). An selective etching technique has been used to
remove the silicon below the 2.5 micron thick diamond layer. A self-supporting diamond
structure has been created this way. Polycrystalline diamond based heaters and thermometers
can be made from doped diamond materials, which can resist corrosive and radiative
Abstract: The mechanical behaviour and ballistic performance of carbon, glass (E and S type),
aramide and polyethylene fabric reinforced composites with different epoxy resins were studied.
The specimens −produced by hand lay-up method− were qualified by low velocity (Charpy and
drop weight tests) and high velocity (two different bores ballistic) impact tests. The energy
absorption capacity of the composites were found to be strongly affected by material properties of
reinforcing fibre, type of fabric structure and elasticity of resin.
Abstract: Availability of a stable carbon nanotube suspension is a prerequisite for
production of polymer composites with carbon nanotube as additives. In this work
nanotube suspensions, which have been prepared from various nanotubes in different
dispersion agents, were compared. Dispersibility of the samples was investigated by
scanning electon microscopy and atomic force microscopy. Solution of a non-ionic
surfactant was also used successfully as a new dispersion agent. Geometrical parameters
of the carbon nanotubes were determined by using atomic force microscopy. Correlation
was found between the dispersibility and the parameters of the nanotubes and relative
permittivity of the different solvents.
Abstract: Supersaturated Al-4.8Zn-1.2Mg-0.14Zr and Al-5.7Zn-1.9Mg-0.35Cu (wt.%) alloys were
processed by Equal-Channel Angular Pressing (ECAP) at 200°C. The crystallite size distribution
and the characteristic parameters of the dislocation structure of both Al matrix and precipitates were
determined by X-ray diffraction line profile analysis, which has been complemented by
transmission electron microscopy (TEM) observations. Results of these investigations show that the
bulk ultrafine-grained microstructure with high dislocation density produced by ECAP has strong
influence on the precipitation process, resulting in high strength in both alloys.
Abstract: In-situ synthesized Al2O3 reinforced metal-ceramic composite coating was fabricated on lowalloyed
carbon steel surface by laser cladding. Injection of the ceramic powder into the melted
surface can be difficult due to the effect of surface tension and to the lower density of the
Al2O3 particles, compared to that of the steel matrix. These difficulties can be avoided by the
in-situ synthesis of Al2O3 particles in the liquid steel matrix. In this paper, the results of
experiments performed by laser beam will be introduced, together with the interpretation of
these results. Experiments proved that the Al2O3 ceramic phase can be created in-situ in the
Abstract: The devitrification of the Fe-Ni-B-Si amorphous ribbon was investigated by the
differential scanning calorimetry (DSC) with scanning and isothermal methods. The
devitrification of rapidly quenched ribbons is a multilevel process. On the basis of DSC
investigations it was determined that crystallization occurs in three processes up to 700°C in
the Fe40Ni40B16Si4 alloy. In the present work the first and second steps have been discussed.
The first crystallization step involves the segregation of the Fe-Ni crystalline solid solution
from the amorphous matrix. During the second crystallization phase, in addition to austenite,
nickel silicide and two types of iron borides crystallize as well. The ribbons were relaxed at
380°C for 2 hours, following the pre-annealing at different temperatures. Pre-annealing was
performed in the DSC within the temperature range elapsing from 395°C to 420°C. The preannealing
at temperatures below the first exothermal DSC peak has an effect on the
crystallization processes. After the pre-annealing the samples were investigated by DSC. The
DSC peak of the first crystallization step shifts to higher temperatures and decrease its
enthalpy. The scanning DSC measurements, applied after the isothermal pre-annealing, were
performed in order to determine the fraction of the ribbon transformed in the primary
crystallization step. The second DSC peak shifts to lower temperatures with a maximum of
4°C. The X-ray diffraction (XRD) analyses reveal that the lattice constant changes with the
pre-annealing temperatures. Such observation was also supported by the circumstance that the
composition of the Fe-Ni solid solution undergoes certain modifications.
Abstract: Nowadays, metal matrix composites have many new areas of application owing
to their excellent properties - for example their great tensile strength and high Young’s
modulus with its relatively low weight.
The aim of this work is to an examination of ceramic fibre-reinforced aluminium matrix
composite wires made via continuous process. Furthermore, the research will outline the
double composite products that are composite wire-reinforced metal matrix composites.
Double composites are examined by tensile tests, bending tests and pressing tests. A
lot of research has been done on the thermal aging of composite wires and on measuring
the impact energy of thermal-aged specimens.
The mechanical test shows us that structures reinforced with the composite wires have
a notably higher load-carrying capacity than does a structure reinforced directly with fibres
or a structure without any reinforcement.
Abstract: Wood fiber reinforced polypropylene composites of different fiber contents without any
treatment were prepared, and tensile tests were carried out on injection molded specimens. With
increasing fiber content a decrease of the tensile strength was experienced. The weak adhesion at
the fiber-matrix interface and the typical composite failures can be seen on SEM pictures. During
the tests acoustic emission was monitored to get more information about the damage mechanism.
From the AE counts distribution it can be concluded that the maximum number of AE counts
decreases simultaneously with the tensile strength in case of the different composites.
Abstract: Polycrystalline diamond and diamond-like carbon (DLC) films were deposited by
microwave chemical vapor deposition (MW-CVD) and by pulsed laser deposition (PLD)
respectively. Ar ion bombardment was used to change the properties of these layers. The
sp2 bonds were determined directly by reflected electron energy loss spectroscopy
(REELS) and further characterization was made by Raman scattering. The polycrystalline
diamond showed only very slight π-π* transition at 6.5 eV, but after Ar ion bombardment
strong peak was formed but definitely shifted to lower energy compared to the well known
π-π* transition of graphite. The as deposited PLD carbon films showed broad peak around
5eV clearly different than the π-π* transition (6.5eV). After Ar+ ion bombardment the peak
was shifted also to lower energy range (4-5eV) with a remaining part at 6.5eV. The lower
energy part of the peak can be correlated to the transition of sp3 sites, while this change in
peak position was not detectable after ion bombardment of the reference HOPG sample,
which does not contain sp3 hybridized carbon atoms.
Abstract: Bulk Al6082 alloy is subjected to ECAP using route Bc. This paper focuses on the
determination of the anisotropy coefficients and equivalent stress-equivalent strain curve using
continuum mechanics equations. Assuming the material to be rigid-plastic, the parameters of the
constitutive equation are determined with the aid of measuring the deformation and the uniaxial
yield stress during upsetting tests in three perpendicular directions.