|
In this article the effect of
graphitization in two dimensional c-c composite bodies
prepared by impregnation of novalak resin is reported.
Mechanical properties were determined by bending tests and
microstructural features were studied by SEM and XRD.It
was found that primary graphitization at 2300°C followed
by graphitization at 2500°C improves the mechanical
strength remarkable. Repeated graphitization and long-term
treatment at 2500°C, however , found to have an adverse
effect .Microstructural observations revealed that the
level of strength is mainly controlled by a sheath
developed around the fibre during graphitization.
Applying
and improper thermal regime affects the matrix - fibre
adherence and may cause the destruction of the fibres.
This enhances the crack propagation and causes early
failure of composite body under loading.
A.Sedghi and F.Golestani Fard |
|
Part І.Optimization of curing stages
Curing of novalak resin has
been investigated by applying different thermal analysis
methods and solvent exteraction technique
Result revealed theat cure
can be optimized by finding the critical steps in cure and
hold resin in these steps for appropriate time . Best
result were also archieved by using resins which contained
lower free phenol and hexamine amount.Application of
pressure is necessary in initial stages of cure but found
to be harmful in the final stages . It was also found that
due to the defects produced in the final stages of curing,
this process cannot be completed and long time post cure
should be applied on these resin.By applying a special
curing regime, it was proved that defects during pyrolysis
stage could be decreased profoundly and a carbon residue
of more than 67 percent expected.the results are explained
by emphasis on carbon carbon
application
A.Sedghi and F.Golestani Fard
|
|
In the fabrication of carbon carbon
composites by thermoset resin precursors, the amount of
precursor resin is so important, but there is not enough
information on the effect of this parameter on the
properties of two-dimensional carbon carbon composites
during and after composite fabrication.
In this research, the effect of phenolic resin precursor
on the structure and properties of two-dimensional carbon
carbon composites investigated during and after
fabrication.In this respect, a model of resin distribution
between carbon fibre layers proposed and effect of its
variation during and after fabrication on microstructure
and mechanical properties of two-dimensional carbon
carbon composites investigated.
A.Sedghi and F.Golestani Fard |
|
In this study two different batches of
acid (H2SO4) and alkaline (NaOH) treated raw raice husks
prepared.the materials were subjected to coking and
pyrolysis for producing SiC under argon atmosphere.The
effect of alkaline and acid treatments on qauntity and
type of SiC (whiskers and particulates) via their effect
on internal and external surfaces of rice husks were
determined.
It was
concluded that, silicon carbide whiskers (SiCw) growed
over both internal and external surface of rice husks
with a higher SiCw growth on external syrface due to
presence of larg quantity of SiO2. It was also shown that
use of alkaline treatment on rice husks resulted in
disintegration of external surface and also the removal of
free SiO2, whereas the use of acid treatment did not have
any major effect on external or internal surface of rice
husks therefore silica was unaffected. However, acid
treatment resulted in decomposition of high molecular
weight organic compounds to smaller molecules. The overall
effect of alkaline and acid treatments on rice husks was a
reduction and increase of resultant SiC, respectively.
R . Elami , F. Akhlagi & A . Sedghi
|
|
RuO2 TiO2 coatings because
of very good corrosion resistance and electrochemical
properties have been widely used in chlor alkali
industries.
In the
present work, RuO2 TiO2 coatings were produced by
thermal decomposition from aqueous solutions of ruthenium
and titanium chlorides in appropriate combination.
The
electrochemical behaviours of coatings were assessed by
electrochemical techniques such as cyclic voltammetry and
polarisation measurements.
SEM
micrographs of the electrodes show a cracked mud
morphology over the electrodes.Microscopic observation of
the electrodes surfaces indicated deepening of cracks and
pit formation on the surfaces by electrolysis.
The
compactness uniformity of the coating improved as the RuO2
content increased. The increase in RuO2 content also
decreased the over potential.
It is
concluded that it is more beneficial to coat the used
anodes for chlor.
Alkali
industry for a cost saving purpose, while electrochemical
behavioure doesnt change
A . Plasseyed , M .Saremi , A. Sedghi
|
|
Protective coatings are
applied on the engineering materials to improve their
physical, thermo chemical and mechanical properties. These
coatings are used in various fields of industrial
applications specially gas turbine blades, and in this
respect, many research projects have been conducted to
improve their properties. In the present study, the
formation of Al-Pt (Aluminum/Platinum) alloy coatings on
Nickel-based superalloys has been investigated. Sputtering
ion beam technique under Argon plasma, pack cementation
and subsequent heat treatment has been used to fabricate
these coatings.
The main goal of this paper is to change the
method for fabrication of platinum layer and investigate
about effect of this variation on the morphology of
coating. The results of this study confirm well with the
results of other investigations, and its related to slow
diffusion of platinum through coating. This method can
produce uniform coatings faster and promise to be
industrial technique for the fabrication of such coatings.
A
. Sedghi , A . SHOKOHI |
.gif)
.jpg)
