Tumerkan Kesim - Academia.edu (original) (raw)

Papers by Tumerkan Kesim

Research paper thumbnail of Characterization of designed, transparent and conductive Al doped ZnO particles and their utilization in conductive polymer composites

Powder Technology, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Research paper thumbnail of Microstructural stability, defect structures and deformation mechanisms in a Ag3Sn/Cu3Sn alloy

Journal of Materials Science, 2016

Ag 3 Sn and Cu 3 Sn are important intermetallic compounds formed in lead-free solders and dental ... more Ag 3 Sn and Cu 3 Sn are important intermetallic compounds formed in lead-free solders and dental amalgams. In this paper, we present a study on the microstructural stability in a Ag 1.5 Cu 1.5 Sn alloy using a combination of scanning and transmission electron microscopy experiments. The as-cast microstructure comprises the D0 a phases h-Ag 3 Sn and e 1-Cu 3 Sn, plus a small amount of g-Cu 6 Sn 5. There is topotaxial precipitation of Ag 3 Sn within the Cu 3 Sn phase, which coarsens with heat treatment at 450°C. For extended low-temperature aging (1000 h at 100°C), there is also precipitation of Cu 3 Sn within the Ag 3 Sn phase. All the heat-treatments result in the formation of secondary defects in the near-surface region. These defects are dislocations in the Ag 3 Sn and {011}-type twins in the Cu 3 Sn. The same defect types are observed in these phases for as-cast samples deformed in compression suggesting that different deformation mechanisms are operating in these isostructural phases.

Research paper thumbnail of Extended Aging of Ag/W Circuit Breaker Contacts: Influence on Surface Structure, Electrical Properties, and UL Testing Performance

Journal of Materials Engineering and Performance, 2015

Samples of 120 V, 30 A commercial circuit breakers were subjected to various aging treatments and... more Samples of 120 V, 30 A commercial circuit breakers were subjected to various aging treatments and the resulting microstructures at the surfaces of the Ag/W contacts were studied using a combination of x-ray diffraction, scanning electron microscopy, and energy-dispersive x-ray spectroscopy techniques. Breakers aged naturally in a hot, humid climate were compared to those subjected to accelerated aging in dry and humid environments. The most extensive oxidation was observed for contacts from breakers subjected to accelerated humid aging; these contacts exhibited thick surface layers consisting of Ag 2 O, Ag 2 WO 4 , Cu(OH) 2 •H 2 O, and WO 3 phases. Far less surface degradation was observed for dry-aged contacts. Naturally aged contacts showed variations in degradation with more oxidation at the surface regions outside the physical contact area on the contact face. A correlation was found between the contact resistances measured from these samples following ASTM standard B 667-97 and the observed surface microstructures. To evaluate the effects of the surface oxides on breaker performance, humid-aged breakers were subjected to standardized UL overload/temperature-rise, endurance, and short-circuit testing following UL489. The contacts in these breakers exhibit similar microstructural and property changes to those observed previously for as-manufactured contacts after UL testing. These data illustrate the robust performance of this contact technology even after being subjected to aggressive artificial aging.

Research paper thumbnail of Surface Degradation of Ag/W Circuit Breaker Contacts During Standardized UL Testing

Journal of Materials Engineering and Performance, 2015

The near-surface microstructure of Ag/W contacts from 120 V, 30 A commercial circuit breakers in ... more The near-surface microstructure of Ag/W contacts from 120 V, 30 A commercial circuit breakers in the asmanufactured condition and after standardized UL overload/temperature-rise, endurance, and short-circuit testing have been investigated using a combination of x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy, focused ion beam milling, and transmission electron microscopy. The as-manufactured contacts comprised three constituents: sintered Ag/W composite particles with finegrained Ag and coarse-grained W, coarse-grained pockets of Ag infiltrate, and a nano-crystalline surface Ag layer. There are also WO 3 and Ag 2 O phases at the surface. After UL overload/temperature-rise testing, there is Ag loss giving a porous W-rich layer at the contact surface. In addition to binary oxides, we observe the formation of Ag 2 WO 4. After UL endurance testing, material is swept across the surface by the breaker action giving a W-rich eroded porous surface on one side and a build-up of mixed oxides on the other. After UL short-circuit testing, a W crust forms due to melting and re-solidification of W and vaporization of Ag, and mid-plane cracks form due to the severe thermal gradients. There is a strong correlation between the observed microstructural features and the contact resistance measurements obtained from these samples.

Research paper thumbnail of Pyroelectric response of lead zirconate titanate thin films on silicon: Effect of thermal stresses

Journal of Applied Physics, 2013

Ferroelectric lead zirconate titanate [Pb(ZrxTi1-xO)3, (PZT x:1-x)] has received considerable int... more Ferroelectric lead zirconate titanate [Pb(ZrxTi1-xO)3, (PZT x:1-x)] has received considerable interest for applications related to uncooled infrared devices due to its large pyroelectric figures of merit near room temperature, and the fact that such devices are inherently ac coupled, allowing for simplified image post processing. For ferroelectric films made by industry-standard deposition techniques, stresses develop in the PZT layer upon cooling from the processing/growth temperature due to thermal mismatch between the film and the substrate. In this study, we use a non-linear thermodynamic model to investigate the pyroelectric properties of polycrystalline PZT thin films for five different compositions (PZT 40:60, PZT 30:70, PZT 20:80, PZT 10:90, PZT 0:100) on silicon as a function of processing temperature (25–800 °C). It is shown that the in-plane thermal stresses in PZT thin films alter the out-of-plane polarization and the ferroelectric phase transformation temperature, with ...

Research paper thumbnail of Indium tin oxide thin films elaborated by sol-gel routes: The effect of oxalic acid addition on optoelectronic properties

Thin Solid Films, 2013

ABSTRACT Single layer indium tin oxide (ITO) thin films were deposited on glass using modified so... more ABSTRACT Single layer indium tin oxide (ITO) thin films were deposited on glass using modified sol-gel formulations. The coating sols were prepared using indium (InCl3 center dot 4H(2)O) and tin salts (SnCl4 center dot 5H(2)O). The stable sols were obtained using ethanol (C2H5OH) and acetylacetone (C5H8O2) as solvents and by the addition of oxalic acid dihydrate (C2H2O4 center dot 2H(2)O) in different amounts. The effect of oxalic acid content in the sol formulation and post-coating calcination treatment (in air at 300-600 degrees C) on electrical/optical properties of ITO films have been reported. It was shown that film formation efficiency, surface coverage and homogeneity were all enhanced with oxalic acid addition. Oxalic acid modification also leads to a significant improvement in electrical conductivity without affecting the film thickness (45 +/- 3 nm). ITO films exhibiting high transparency (approximate to 93%, visible region) with a sheet resistance as low as 3.8 +/- 0.4 k Omega/sqr have been formed by employing coating sols with optimized oxalic acid amount. The mechanisms and factors affecting the functional performance of oxalic acid-modified films have been thoroughly discussed and related to the microstructural and chemical characteristic of the films achieved by oxalic acid addition.

Research paper thumbnail of Characterization of designed, transparent and conductive Al doped ZnO particles and their utilization in conductive polymer composites

Powder Technology, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Research paper thumbnail of Microstructural stability, defect structures and deformation mechanisms in a Ag3Sn/Cu3Sn alloy

Journal of Materials Science, 2016

Ag 3 Sn and Cu 3 Sn are important intermetallic compounds formed in lead-free solders and dental ... more Ag 3 Sn and Cu 3 Sn are important intermetallic compounds formed in lead-free solders and dental amalgams. In this paper, we present a study on the microstructural stability in a Ag 1.5 Cu 1.5 Sn alloy using a combination of scanning and transmission electron microscopy experiments. The as-cast microstructure comprises the D0 a phases h-Ag 3 Sn and e 1-Cu 3 Sn, plus a small amount of g-Cu 6 Sn 5. There is topotaxial precipitation of Ag 3 Sn within the Cu 3 Sn phase, which coarsens with heat treatment at 450°C. For extended low-temperature aging (1000 h at 100°C), there is also precipitation of Cu 3 Sn within the Ag 3 Sn phase. All the heat-treatments result in the formation of secondary defects in the near-surface region. These defects are dislocations in the Ag 3 Sn and {011}-type twins in the Cu 3 Sn. The same defect types are observed in these phases for as-cast samples deformed in compression suggesting that different deformation mechanisms are operating in these isostructural phases.

Research paper thumbnail of Extended Aging of Ag/W Circuit Breaker Contacts: Influence on Surface Structure, Electrical Properties, and UL Testing Performance

Journal of Materials Engineering and Performance, 2015

Samples of 120 V, 30 A commercial circuit breakers were subjected to various aging treatments and... more Samples of 120 V, 30 A commercial circuit breakers were subjected to various aging treatments and the resulting microstructures at the surfaces of the Ag/W contacts were studied using a combination of x-ray diffraction, scanning electron microscopy, and energy-dispersive x-ray spectroscopy techniques. Breakers aged naturally in a hot, humid climate were compared to those subjected to accelerated aging in dry and humid environments. The most extensive oxidation was observed for contacts from breakers subjected to accelerated humid aging; these contacts exhibited thick surface layers consisting of Ag 2 O, Ag 2 WO 4 , Cu(OH) 2 •H 2 O, and WO 3 phases. Far less surface degradation was observed for dry-aged contacts. Naturally aged contacts showed variations in degradation with more oxidation at the surface regions outside the physical contact area on the contact face. A correlation was found between the contact resistances measured from these samples following ASTM standard B 667-97 and the observed surface microstructures. To evaluate the effects of the surface oxides on breaker performance, humid-aged breakers were subjected to standardized UL overload/temperature-rise, endurance, and short-circuit testing following UL489. The contacts in these breakers exhibit similar microstructural and property changes to those observed previously for as-manufactured contacts after UL testing. These data illustrate the robust performance of this contact technology even after being subjected to aggressive artificial aging.

Research paper thumbnail of Surface Degradation of Ag/W Circuit Breaker Contacts During Standardized UL Testing

Journal of Materials Engineering and Performance, 2015

The near-surface microstructure of Ag/W contacts from 120 V, 30 A commercial circuit breakers in ... more The near-surface microstructure of Ag/W contacts from 120 V, 30 A commercial circuit breakers in the asmanufactured condition and after standardized UL overload/temperature-rise, endurance, and short-circuit testing have been investigated using a combination of x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy, focused ion beam milling, and transmission electron microscopy. The as-manufactured contacts comprised three constituents: sintered Ag/W composite particles with finegrained Ag and coarse-grained W, coarse-grained pockets of Ag infiltrate, and a nano-crystalline surface Ag layer. There are also WO 3 and Ag 2 O phases at the surface. After UL overload/temperature-rise testing, there is Ag loss giving a porous W-rich layer at the contact surface. In addition to binary oxides, we observe the formation of Ag 2 WO 4. After UL endurance testing, material is swept across the surface by the breaker action giving a W-rich eroded porous surface on one side and a build-up of mixed oxides on the other. After UL short-circuit testing, a W crust forms due to melting and re-solidification of W and vaporization of Ag, and mid-plane cracks form due to the severe thermal gradients. There is a strong correlation between the observed microstructural features and the contact resistance measurements obtained from these samples.

Research paper thumbnail of Pyroelectric response of lead zirconate titanate thin films on silicon: Effect of thermal stresses

Journal of Applied Physics, 2013

Ferroelectric lead zirconate titanate [Pb(ZrxTi1-xO)3, (PZT x:1-x)] has received considerable int... more Ferroelectric lead zirconate titanate [Pb(ZrxTi1-xO)3, (PZT x:1-x)] has received considerable interest for applications related to uncooled infrared devices due to its large pyroelectric figures of merit near room temperature, and the fact that such devices are inherently ac coupled, allowing for simplified image post processing. For ferroelectric films made by industry-standard deposition techniques, stresses develop in the PZT layer upon cooling from the processing/growth temperature due to thermal mismatch between the film and the substrate. In this study, we use a non-linear thermodynamic model to investigate the pyroelectric properties of polycrystalline PZT thin films for five different compositions (PZT 40:60, PZT 30:70, PZT 20:80, PZT 10:90, PZT 0:100) on silicon as a function of processing temperature (25–800 °C). It is shown that the in-plane thermal stresses in PZT thin films alter the out-of-plane polarization and the ferroelectric phase transformation temperature, with ...

Research paper thumbnail of Indium tin oxide thin films elaborated by sol-gel routes: The effect of oxalic acid addition on optoelectronic properties

Thin Solid Films, 2013

ABSTRACT Single layer indium tin oxide (ITO) thin films were deposited on glass using modified so... more ABSTRACT Single layer indium tin oxide (ITO) thin films were deposited on glass using modified sol-gel formulations. The coating sols were prepared using indium (InCl3 center dot 4H(2)O) and tin salts (SnCl4 center dot 5H(2)O). The stable sols were obtained using ethanol (C2H5OH) and acetylacetone (C5H8O2) as solvents and by the addition of oxalic acid dihydrate (C2H2O4 center dot 2H(2)O) in different amounts. The effect of oxalic acid content in the sol formulation and post-coating calcination treatment (in air at 300-600 degrees C) on electrical/optical properties of ITO films have been reported. It was shown that film formation efficiency, surface coverage and homogeneity were all enhanced with oxalic acid addition. Oxalic acid modification also leads to a significant improvement in electrical conductivity without affecting the film thickness (45 +/- 3 nm). ITO films exhibiting high transparency (approximate to 93%, visible region) with a sheet resistance as low as 3.8 +/- 0.4 k Omega/sqr have been formed by employing coating sols with optimized oxalic acid amount. The mechanisms and factors affecting the functional performance of oxalic acid-modified films have been thoroughly discussed and related to the microstructural and chemical characteristic of the films achieved by oxalic acid addition.