Showing 9 results for Allahkaram
S.r. Allahkaram, R. Shamani,
Volume 6, Issue 1 (winter 2009 2009)
Abstract
Abstract: Due to the expansion of high voltage Alternating Current (AC) power transmission lines and cathodically
protected buried pipelines, it is becoming more and more difficult to construct them with enough safe distances
between them. Thus, the pipelines are frequently exposed to induced AC interferences, which result in perturbation of
Cathodic Protection (CP) due to AC corrosion. To study the above criterion, an experimental set up was used with
coupons exposed to simulated soil solutions, while under both CP and AC induced condition for which an AC+DC
power supply was utilized. The experiments were carried out in several simulated soil solutions corresponding to
several soil samples collected from various regions along a buried pipeline with overhead parallel high voltage power
transmission line. The results indicated that AC corrosion depends strongly on the composition of the soil.
S.r. Allahkaram, R. Shamani,
Volume 6, Issue 2 (Spring 2009 2009)
Abstract
Abstract: The risks of alternating current (AC) corrosion and overprotection increasingly demand new criteria for
cathodically protected pipelines. To assess the risk of AC corrosion, new cathodic protection (CP) criteria have been
proposed based on DC/AC current densities measurements using coupons. The monitoring system designed for this
project was based on the instant-off method, with steel coupons simulating coating defects on a buried pipeline. The
problems associated with the instantaneous off-potential measurements have been attributed to a non-sufficient time
resolution. In present study, it has been possible to determine the de-polarisation of steel coupon within a few
milliseconds after disconnecting the coupon from the DC/AC power source, by increasing data acquisition rate. For
this, a monitoring system was developed in order to measure the IR-free potential together with the DC/AC current
densities. The monitoring system was utilized for both laboratory experiments and site survey to study the mechanism
and the condition of AC corrosion, its mitigation and more importantly to define new CP criteria.
Z. Shahri, S.r. Allahkaram,
Volume 9, Issue 4 (December 2012)
Abstract
Metal matrix composite coatings reinforced with nano-particles have attracted scientific and technological interest due to the enhanced properties exhibited by these coatings. Cobalt/hexagonal boron nitride nano-composite coatings were prepared by means of the pulse current electroplating from a chloride electrolyte on copper substrates and a comparison was made with the pure cobalt in terms of structure and tribological properties. Effects of particles concentration (5-20 gL-1) and current density (50-200 mA cm-2) on the characterization of electroplated coatings were investigated via X-ray diffraction analysis, energy dispersive spectroscopy and Vickers micro-hardness. Moreover, the tribological behavior was studied using pin-on-disc method. The results showed that cobalt/hexagonal boron nitride nano-composite coatings have higher hardness, wear resistance and lower friction coefficient than pure cobalt and the plating parameters strongly affect the coating’s properties
S. R. Allahkaram, R. Faezi Alivand, M. S. Bakhsh,
Volume 10, Issue 1 (march 2013)
Abstract
Abstract:Electroless Nickel-phosphorus (EN) coatings provide high performance in various industrial fields due to their unique properties such as excellent corrosion and wear resistance. This paper aims to study the effect of ZnO nano-particles addition on corrosion behavior of EN coatings. Various amounts of ZnO nano-particles with average diameter of 50 nm were added to hypophosphite reduced EN bath to deposit composite coatings. Microstructural investigations were carried out via scanning electron microscopy (SEM). Chemical composition of the coatings was investigated via energy dispersive spectroscopy (EDS). Electrochemical impedance spectroscopy (EIS) and polarization tests were used to study the corrosion properties of the coatings in a 3.5 wt.% NaCl solution. SEM investigations showed that the coating deposited from the bath containing 2 g/L of ZnO nano-particles had the most amount of nano-particles incorporated in the coating. EDS results revealed that incorporation of ZnO nano-particles in the composite coating resulted in a decrease in phosphorous content of the coating. Corrosion tests showed that corrosion resistance of the electroless Ni-P/nanoZnO composite coatings in 3.5 wt.% NaCl solution had an improvement in comparison to electroless Ni-P base coating
Z. Shahri, S. R. Allahkaram,
Volume 10, Issue 4 (december 2013)
Abstract
Metal matrix nano composite coatings possess enhanced properties such as corrosion and wear resistance. This paper aims to study the corrosion behavior of pure Co and Co-BN nano composite coatings deposited with different particles concentration (5-20 g L-1) on copper substrates using electroplating technique. Morphology and elemental compositions of the coatings were investigated by means of scanning electron microscope (SEM) equipped with an energy dispersive spectroscopy (EDS). The corrosion behavior was analyzed in a 3.5 wt% NaCl via polarization and impedance techniques. The results obtained in this study indicate that the co-deposition of BN nano particles improved corrosion resistance of electrodeposited cobalt coatings.
S.r. Allahkaram, H. Mazaheri,
Volume 11, Issue 3 (september 2014)
Abstract
Ni-P Electroless coatings provide appropriate resistance to wear and corrosion. Co-deposition of particles
between layers can improve their properties, especially general corrosion and erosion-corrosion behavior by means
of nano diamond as reinforcing particles. In this study Ni-P/nano diamond composite deposition were deposited on
steel substrate. Structure of the coatings and corrosion resistance of theme were investigated by scanning electron
microscopy and corrosion tests in salty media. The composite structure of the deposit was evaluated as nano size
without using any surfactants. Also results for the composite coating show better corrosion protection and higher
hardness comparing with as -deposited Ni-P. The optimum concentration of diamond nanometer particles were found
by evaluation of scanning electron microscopy pictures, hardness measurement, linear polarization and
electrochemical impedance spectroscopy results
M. Siadat-Cheraghi, S. R. Allahkaram, Z. Shahri,
Volume 12, Issue 1 (march 2015 2015)
Abstract
Pure cobalt coatings were electrodeposited on copper substrate by means of direct electric current in a
chloride solution at different current densities in the range of 10-70 mA cm
-2
. The surface morphology and
microstructure were investigated via X-ray diffraction analysis and scanning electron microscopy. Corrosion behavior
of cobalt coatings was also studied in a 3.5 wt% NaCl solution using potentiodynamic polarization and impedance
spectroscopy techniques. The results showed that corrosion resistance of deposits was strongly influenced by the
coating’s morphology. Co deposit obtained in lower current densities exhibited the highest corrosion resistance, due
to their lower grain boundaries and so the least density of active sites for preferential corrosion attacks
T. Ebrahimi Sadrabadi, S.r. Allahkaram, N. Towhidi,
Volume 13, Issue 4 (December 2016)
Abstract
Porous hollow glass microspheres have many uses, including encapsulation of active materials. In this paper a fast and facile method for fabricating porous hollow glass-microspheres was demonstrated by etching them using dilute hydrofluoric acid. Then, a highly reactive amine was infiltrated into the etched glass microspheres. Scanning electron microscopy was conducted for the hollow glass microspheres prior and post etching process. With regards to the porous hollow glass spherical sample, the spherical nature, morphology, pore diameter and the porosity were studied using scanning electron microscopy. Formation of the intact hollow glass microspheres with an open through wall porosities following phase separation and etching of the boron oxide rich phase was demonstrated using reciprocating shaker as the most suitable agitation method. The BET results indicated that the surface of the porous microspheres contained nano-pores. It is believed that the simplicity of the reported fabrication technique of micro/nano porous structure has the potential to scaling up for large scale production
S. Akbarzadeh, S.r. Allahkaram, S. Mahdavi,
Volume 15, Issue 2 (June 2018)
Abstract
Tin-Zinc alloy coatings have many applications because of their unique properties such as corrosion resistance, solderability and flexibility. In this study, the effect of current density, temperature and pH on chemical composition, cathodic current efficiency, morphology and structures of the coatings was investigated. The results illustrated that, at low current densities (<0.5 mA/cm2), the coatings were relatively pure tin, but Zn content increased with enhancing the current density. At higher currents a relatively pure Zn film was obtained. Temperature and pH also affected chemical composition of the alloy films. Zn content of the coatings was decreased by increasing the temperature, while its variation with pH had ascending-descending trend. Morphological investigation of the coatings revealed that increasing Zn content of deposits led to porous, rough and fine grained films.
