Journal Papers by Tahere ( T I N A ) Ebrahimi
coatings, 2024
In the realm of industries focused on tribology, such as the machining industry, among
others, t... more In the realm of industries focused on tribology, such as the machining industry, among
others, the primary objective has been tribological performance enhancement, given its substantial
impact on production cost. Amid the variety of tribological enhancement techniques, cathodic arc
evaporation physical vapour deposition (CAE-PVD) coatings have emerged as a promising solution
offering both tribological performance enhancement and cost-effectiveness. This review article aims
to systematically present the subject of CAE-PVD coatings in light of the tribological performance
enhancement. It commences with a comprehensive discussion on substrate preparation, emphasizing
the significant effect of substrate roughness on the coating properties and the ensuing tribological
performance. The literature analysis conducted revealed that optimum tribological performance could
be achieved with an average roughness (Ra) of 0.1 µm. Subsequently, the article explores the CAEPVD process and the coating’s microstructural evolution with emphasis on advances in macroparticles
(MPs) formation and reduction. Further discussions are provided on the characterization of the
coatings’ microstructural, mechanical, electrochemical and tribological properties. Most importantly,
crucial analytical discussions highlighting the impact of deposition parameters namely: arc current,
temperature and substrate bias on the coating properties are also provided. The examination of
the analyzed literature revealed that the optimum tribological performance can be attained with
a 70 to 100 A arc current, a substrate bias ranging from −100 to −200 V and a deposition temperature
exceeding 300 ◦C. The article further explores advancements in coating doping, monolayer and
multilayer coating architectures of CAE-PVD coatings. Finally, invaluable recommendations for
future exploration by prospective researchers to further enrich the field of study are also provided.
Results in Physics, 2022
The present work studied the scalability of phase change material (PCM) down to a single-digit nm... more The present work studied the scalability of phase change material (PCM) down to a single-digit nm with single wall metallic carbon nanotubes (SWCNT) electrodes. For this purpose, the low bias electron transport properties of Ge 2 Sb 2 Te 5 (GST) are investigated using a DFT-NEGF formalism. The amorphous Ge 2 Sb 2 Te 5 (a-GST) is obtained using DFT-based molecular dynamic simulation. It has been seen that while 6 nm crystalline Ge 2 Sb 2 Te 5 (c-GST) has a large transmission near the Fermi level, a-GST exhibits a clear band-gap, and by further reduction of its length to 12 Å, the band-gap disappears. The electrical conductance of nanowire a-GST is predominantly due to coherent electron transport via acceptor-like and donor-like traps. The c-GST/a-GST conductance (c ∕ a) ratio as a function of the device length is calculated, which shows good agreement compared with experimental works. We show that the ultimate limit for downscaling the nanowire GST sandwiched between SWCNT electrodes is about 24 Å. This can be attributed to the overlapping metalinduced gap states from electrodes that lead to the disappearance of the band-gap of the amorphous phase and a sharp decrease in the c ∕ a ratio in shorter channel length. The On/Off ratio of 12 Å GST sharply drops below 10, and the reliable read procedure is not possible on this size scale. We have also investigated the effect of interfacial stress between the electrode and GST and show that it reduces the c ∕ a ratio and hurts the switch-ability of the device.
International Polymer Processing, No. 5, 2018
Autonomous self-healing was achieved by synthesizing epoxy coatings which contain dual micro/nano... more Autonomous self-healing was achieved by synthesizing epoxy coatings which contain dual micro/nanocapsules; epoxy and amine. Epoxy micro/nanocapsules were prepared by an in situ polymerization process and amine microcapsules were fabricated by vacuum infiltration of diethylenetriamine into nanoporous hollow glass microspheres. Both types of capsules were embedded into epoxy matrix. When cracks were created and started to grow in the coating, the micro/nano-capsules near the crack were ruptured and released their contents. As a result of curing reaction between released curing agents (epoxy and amine), healing of the cracked sites was completed. In this work, some properties of epoxy/amine micro/nanocapsule based self-healing coatings such as morphology of micro/nanocapsule and coating, healing and corrosion properties were studied. Also thermal stability and adhesion properties of this kind of coating were evaluated comprehensively. It was found out that optimum mass ratio of epoxy/amine capsules ratio is 1 : 1 and the highest healing efficiency was achieved for a total micro/nanocapsule concentration of 15 wt.%. Regarding thermal and adhesion behavior of coatings, it was observed that adding micro/nano-capsules to epoxy matrix did not change these properties significantly which means self-healing characteristics were achievable without deteriorating other properties.
مجله صنعت آبكاري، شماره 36، 1384, 2005
مجله پوشش هاي سطحي، شماره 16، 1385, 2006
فصلنامه علمي، خبري و پژوهشي دنیای مواد، شماره 10، 1389, 2010
فصلنامه علمي، خبري و پژوهشي دنیای مواد، شماره 12 و 13، 1390, 2011
فصلنامه زنگ، فصلنامه علمی، آموزشی، ترویجی انجمن خوردگی ایران، شماره 64، 1395, 2016
Journal of Advanced Materials and Technologies, No. 2, 2017
In the field of coatings, extensive laboratory research has been conducted in the last decade. In... more In the field of coatings, extensive laboratory research has been conducted in the last decade. In the present work, effectiveness of epoxy resin filled microcapsules was investigated for future using in healing of cracks generated in coatings. Microcapsules were prepared by in situ polymerization of urea–formaldehyde resin to form shell over epoxy resin droplets. The optimal process parameters for synthesizing the microcapsules were selected. The as-synthesized microcapsules were studied by various characterizations techniques, including scanning electron microscope (SEM), Fourier transform-infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicate that microcapsules containing epoxy resins can be synthesized successfully. The average size is around 100 µm. The rough outer surface of microcapsule is composed of agglomerated urea–formaldehyde nanoparticles. The microcapsules basically exhibit good storage stability at room temperature, and they are chemically stable before the heating temperature is up to approximately 250 °C.
Journal of Nanostructure in Chemistry 2 (2011) 29-32, 2011
Iranian Journal of Materials Science & Engineering , Vol. 13, No. 4, 2016
Polymer Science, Series B, Vol. 59, No. 3, 1–11, 2017
–In the field of coatings, extensive laboratory research has been conducted in the last decade. I... more –In the field of coatings, extensive laboratory research has been conducted in the last decade. In the present work, effectiveness of epoxy resin filled micro/nanocapsules was investigated for future using in healing of cracks generated in coatings. Micro/nanocapsules were prepared by in situ polymerization of urea– formaldehyde resin to form shell over epoxy resin droplets. The optimal process parameters for synthesizing the micro/nanocapsules were selected. The as-synthesized capsules were studied by various characterizations techniques, including scanning electron microscope (SEM), particle size analyzer (PSA), Fourier transform-infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicate that micro/nanocapsules containing epoxy resins can be synthesized successfully. The rough outer surface of microcapsule is composed of agglomerated urea–formaldehyde nanoparticles. They basically exhibit good storage stability at room temperature, and they are chemically stable before the heating temperature is up to approximately 250°C.
This study is focused on the role of nano hydroxyapatite particles on the mechanical properties o... more This study is focused on the role of nano hydroxyapatite particles on the mechanical properties of PMMA/ HA nanocomposites. In order to achieve a proper and homogeneous distribution of HA particles in the polymer matrix, mixer milling process was applied. Wear, compression and three-point bending tests were conducted. It was observed that wear rate decreased by increasing in HA content in both atmosphere and artificial saliva. The results of compression tests showed that the addition of 2.5 percent HA to PMMA promoted ultimate compressive strength, yield strength and modulus while caused to decrease elongation at break. Also it was elucidated that addition of HA more than 2.5 wt% caused a decrease in both ultimate compressive strength and compression yield strength and an increase in elongation at break. The results of three-point bending tests on the PMMA cements containing 2.5 percent HA demonstrated the maximum bending strength value and modulus among all the HA containing formulations. However there was no direct proportionality between the results of bending tests and the HA content and the addition of HA to PMMA (up to 10 wt%) did not change the bending properties significantly.
polymer-plastic technology and engineering, 49, 1284–1288, 2010
Conference Presentations by Tahere ( T I N A ) Ebrahimi
11th International Conference on Materials Engineering & Metallurgy, (iMat 2022), 2022
11th International Conference on Materials Engineering & Metallurgy, (iMat 2022), 2022
This study reports the effects of solvent on the surface properties of rubbed polyvinyl alcohol (... more This study reports the effects of solvent on the surface properties of rubbed polyvinyl alcohol (PVA) thin films deposited on the glass substrate by the spin-coating method. The used solvents were water and methanol diluted 20% w/w aqueous solution. Thin films are characterized by atomic force microscopy, Fourier transform infrared (FTIR) spectroscopy, and contact angle measurements. FTIR spectra showed the characteristic valleys, which indicated the presence of C-H and O-H bonds in the chemical structure of PVA. PVA thin film thicknesses measured by AFM are in the range of 100-200 nm. The contact angles of PVA thin layers are also characterized using the sessile drop method. Using water and methanol as solvents of PVA for coating materials has a great impact on PVA molecules' chemical structure. Furthermore, mechanical rubbing of the surface of the PVA thin film by velvet causes a rearrangement of functional groups at the PVA chains. Due to the variation of chemical structure and reorientation of PVA chains, the polarity of the surface alters which correlates to the surface contact angle.
9th International Conference on Materials Engineering & Metallurgy, (iMat 2020), 2020
Self-healing was achieved by synthesizing epoxy coatings that contain dual micro/nanocapsules; ep... more Self-healing was achieved by synthesizing epoxy coatings that contain dual micro/nanocapsules; epoxy and amine. Both types of capsules were embedded into epoxy matrix. When cracks were created and started to grow in the coating, the micro/nanocapsules near the crack were ruptured and released their contents. As a result of curing reaction between released curing agents (epoxy and amine), healing of the cracked sites was completed. The coatings containing loaded micro/nanocapsules were applied on carbon steels and their self-healing behavior was investigated using scanning electron microscopy (SEM) observation and scanning electrochemical microscopy (SECM) at different capsules concentration: 5, 10, 15 and 20 wt%. SECM measurements allowed us to evaluate the local corrosion activity at the artificial defect on the coatings which was deliberately introduced into it. Both the negative feedback and redox competition modes were operated. The results confirmed the physical repair of the coating in the defect leads to a recovery of the local barrier properties of it and protection of coating sample after healing process.
9th International Conference on Materials Engineering & Metallurgy, (iMat 2020), 2020
Micro/nanocapsules containing self-healing agents have been introduced into epoxy coatings to sel... more Micro/nanocapsules containing self-healing agents have been introduced into epoxy coatings to self-heal the defects and improve the anti-corrosion behavior. To provide epoxy based coating with self-healing ability, two-component healing system consisting of urea-formaldehyde micro/nanocapsules containing epoxy and nano-porous hollow glass microspheres containing diethylenetriamine (DETA) were synthesized. When the defect was made, the micro/nanocapsules released the healing materials to fill the defected area. The coatings containing loaded micro/nanocapsules were applied on carbon steels and their self-healing behavior was investigated using scanning electron microscopy (SEM) observation and electrochemical impedance spectroscopy (EIS) technique. In order to obtain the optimum concentration of micro/nanocapsule in the coatings, coatings with 0 %, 5 %, 15% and 20 % micro/ nanocapsules were synthesized and characterized. The results confirmed that the optimum amount of micro/nanocapsules addition to the epoxy coating was found to be 15wt.%.. The results also reveal that the addition of micro/nanocapsules does not damage the barrier properties of the non-scratched epoxy coating during immersion time.
انجمن پلیمر, 2009
In current study, the role of milling time on thermal properties and crystallization behavior of ... more In current study, the role of milling time on thermal properties and crystallization behavior of medium density polyethylene (MDPE) was investigated. For this purpose, high energy ball mill and differential scanning calorimetery (DSC) were used. The results of DSC tests indicated that the milling process affected on crystallization behavior and thermal properties of MDPE. Rising crystallization temperature, specific heat capacity and crystallinity index and decreasing Avrami index were caused by ball milling. While, melting temperature did not change even with long time mechanical mixing. Moreover, thermal properties of polymer were not changed significantly by increasing milling time.
The Second Conference on Application of Nanotechnology in Science, Engineering and Medicine, 2011
This study is focused on the role of nano hydroxyapatite particles on the degradation behavior of... more This study is focused on the role of nano hydroxyapatite particles on the degradation behavior of nano HA/PMMA composites. In order to achieve a proper and homogeneous distribution of HA particles in the polymer matrix, mixer milling process was applied. Thermo gravimetric analysis was conducted using TGA analyzer. It is observed that the degradation of samples takes place in a single stage and the addition of nano HA to PMMA promotes degradation behavior of samples.
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Journal Papers by Tahere ( T I N A ) Ebrahimi
others, the primary objective has been tribological performance enhancement, given its substantial
impact on production cost. Amid the variety of tribological enhancement techniques, cathodic arc
evaporation physical vapour deposition (CAE-PVD) coatings have emerged as a promising solution
offering both tribological performance enhancement and cost-effectiveness. This review article aims
to systematically present the subject of CAE-PVD coatings in light of the tribological performance
enhancement. It commences with a comprehensive discussion on substrate preparation, emphasizing
the significant effect of substrate roughness on the coating properties and the ensuing tribological
performance. The literature analysis conducted revealed that optimum tribological performance could
be achieved with an average roughness (Ra) of 0.1 µm. Subsequently, the article explores the CAEPVD process and the coating’s microstructural evolution with emphasis on advances in macroparticles
(MPs) formation and reduction. Further discussions are provided on the characterization of the
coatings’ microstructural, mechanical, electrochemical and tribological properties. Most importantly,
crucial analytical discussions highlighting the impact of deposition parameters namely: arc current,
temperature and substrate bias on the coating properties are also provided. The examination of
the analyzed literature revealed that the optimum tribological performance can be attained with
a 70 to 100 A arc current, a substrate bias ranging from −100 to −200 V and a deposition temperature
exceeding 300 ◦C. The article further explores advancements in coating doping, monolayer and
multilayer coating architectures of CAE-PVD coatings. Finally, invaluable recommendations for
future exploration by prospective researchers to further enrich the field of study are also provided.
Conference Presentations by Tahere ( T I N A ) Ebrahimi
others, the primary objective has been tribological performance enhancement, given its substantial
impact on production cost. Amid the variety of tribological enhancement techniques, cathodic arc
evaporation physical vapour deposition (CAE-PVD) coatings have emerged as a promising solution
offering both tribological performance enhancement and cost-effectiveness. This review article aims
to systematically present the subject of CAE-PVD coatings in light of the tribological performance
enhancement. It commences with a comprehensive discussion on substrate preparation, emphasizing
the significant effect of substrate roughness on the coating properties and the ensuing tribological
performance. The literature analysis conducted revealed that optimum tribological performance could
be achieved with an average roughness (Ra) of 0.1 µm. Subsequently, the article explores the CAEPVD process and the coating’s microstructural evolution with emphasis on advances in macroparticles
(MPs) formation and reduction. Further discussions are provided on the characterization of the
coatings’ microstructural, mechanical, electrochemical and tribological properties. Most importantly,
crucial analytical discussions highlighting the impact of deposition parameters namely: arc current,
temperature and substrate bias on the coating properties are also provided. The examination of
the analyzed literature revealed that the optimum tribological performance can be attained with
a 70 to 100 A arc current, a substrate bias ranging from −100 to −200 V and a deposition temperature
exceeding 300 ◦C. The article further explores advancements in coating doping, monolayer and
multilayer coating architectures of CAE-PVD coatings. Finally, invaluable recommendations for
future exploration by prospective researchers to further enrich the field of study are also provided.