In this study, the nanostructural vacancy behavior of bovine derived hydroxyapatite (BHA) doped w... more In this study, the nanostructural vacancy behavior of bovine derived hydroxyapatite (BHA) doped with powder zirconmullite (ZM) contents of 5, 7.5, 10 and 12.5 wt.% were presented at sintering temperatures of 1000, 1100, 1200 and 1300°C. ZM‐doped BHA (ZM‐BHA) was characterized by X‐ray diffraction and positron annihilation lifetime spectroscopy (PALS). Density and hardness behavior were measured with respect to increasing sintering temperature. PALS results indicate that the longest lifetime component τ3 of ortho‐positronium (o‐Ps) localized at open spaces is attributed to the vacancy site and almost constant with the ZM contents and the sintering temperatures to have a mean value of 0.680 ns (corresponding to the radius of 0.997 nm). This average value is ascribed to the OH group defects along the main crystalline line. On the other hand, the o‐Ps intensity attributed to the number of vacancy sites increases almost linearly with ZM additives and sintering temperatures. The intensity...
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.
International Journal of Thermophysics, Nov 1, 2015
The non-Newtonian viscosity behavior of atactic and syndiotactic polystyrenes (aPS and sPS), at t... more The non-Newtonian viscosity behavior of atactic and syndiotactic polystyrenes (aPS and sPS), at temperatures from $$200\,{}^{\circ }\hbox {C}$$200∘C to $$300\,{}^{\circ }\hbox {C}$$300∘C and pressures up to 30 MPa, was studied using the recently proposed Yahsi–Dinc–Tav model, in particular, the Cross-like model. Viscosity data with shear rates of $$0.01\,\hbox {s}^{-1}$$0.01s-1 to $$5000\,\hbox {s}^{-1}$$5000s-1 were taken from literature at ambient pressure and were reproduced from the Cross-Vogel model at elevated pressures. The viscosities were predicted using the Yahsi–Dinc–Tav model with average absolute deviations of 4.37 % at ambient pressure and 9.63 % at high pressures for aPS and 2.54 % at ambient pressure and 4.79 % at high pressures for sPS. We extended this work to relate the zero shear and the constant shear rate viscosities in terms of the temperature- and pressure-dependent hole fraction using the thermo-occupancy function. The hole fraction (h) was computed from Simha–Somcynsky hole theory. Analytical relationships of specific density and hole fraction in terms of scaled temperature and pressure were constructed for practical purposes. The effects of tacticity of polystyrenes were discussed in terms of the thermo-occupancy function in detail. In particular, the derivative of the logarithm of the viscosities (viscoholibility) was found to decrease with an increasing hole fraction.
The elongational flow behavior of polyethylene, polypropylene, polystyrene, poly(methyl methacryl... more The elongational flow behavior of polyethylene, polypropylene, polystyrene, poly(methyl methacrylate), and polycarbonate, temperatures from 70 to 290 ∘ C and pressures up to 70 MPa, is examined with the Yahsi-Dinc-Tav (YDT) model and its particular case known as the Cross model. The viscosity data employed in the range of 3-405 s-1 elongational rates were acquired from the literature at ambient and elevated pressures. The predictions and the fitting results of the proposed YDT model with the same measurement data are compared with the Cross model. The average absolute deviations of the viscosities predicted by the YDT model range from 0.54% to 9.44% at ambient and 1.95% to 6.28% at high pressures. Additionally, the linear formulations derived from the YDT model are employed to relate the viscosity with temperature and hole fraction ("thermooccupancy" function) at zero level of elongational rate and constant elongational rate along with constant elongational stress. The effects of the four viscosity parameters (such as transmission and activation energy coefficients in these equations) on the elongational viscosity are analyzed in detail and some conclusions on the structural differences for the polymers are discussed.
Journal of the Chemical Society, Faraday Transactions, 1995
We have analysed the equation of states (eos) data for five series of compounds in terms of the S... more We have analysed the equation of states (eos) data for five series of compounds in terms of the Simha-Somcynsky hole theory and, in this manner, obtained graph-averaged temperature, volume and pressure scaling parameters. The eos data were obtained some time ago, when ...
This study brokes new ground to understand the insulation and permeability performances of rigid ... more This study brokes new ground to understand the insulation and permeability performances of rigid polyurethane foams (RPUFs) containing the different contents of micron-sized turkey feather powders (TFPs) depending on the free volume change for the first time. The effects of TFPs loading on the RPUFs were investigated by the examination of their structural and chemical features (particle size and ATR-FTIR analyses), free volume property (PALS analysis), insulation features (thermal conductivity and sound absorption tests), permeability performance (air and water vapor permeability tests) and cellular topology (SEM). PALS analysis results revealed that the addition of TFPs into the foams led to the sharp decrease in all free volume parameters since TFPs caused the formation of the disordered cells by occupying the holes in the matrix. Furthermore, both thermal conductivity and acoustic performance of the resulting foams get worse when compared to unfilled RPUF. This results were attri...
Neodymium-doped Y2Si2O7 nanopowders were synthesized by sol-gel and annealed under varying anneal... more Neodymium-doped Y2Si2O7 nanopowders were synthesized by sol-gel and annealed under varying annealing temperature conditions. The phase transformation of Y2Si2O7 and the crystalline size change were observed with annealing temperature. Photoluminescence and the decay patterns of the 4F3/2→ 4I9/2, 4I11/2, and 4I13/2 transitions were examined to reveal the spectroscopic characteristics of the powders. The spectral outputs of Nd3+:Y2Si2O7 phosphors remain strongly connected to the phase properties of Y2Si2O7. The positron lifetimes (τ 2, τ 3, and τ 4) and intensities (I 2, I 3, and I 4) obtained by positron annihilation lifetime spectroscopy were discussed for neodymium-doped Y2Si2O7 phosphors to relate the structural and boundary changes in terms of the phases and molar contents of the Nd3+ ions. The τ 2 and I 2 components were related to the structural open space in the grain, the τ 3 and I 3 components were correlated with vacancy-like defects in the grain boundaries, and the τ 4 and...
The monomer, p-benzophenoneoxycarbonylphenyl methacrylate (BPOCPMA) the polymer of which exhibit ... more The monomer, p-benzophenoneoxycarbonylphenyl methacrylate (BPOCPMA) the polymer of which exhibit mesomorphic behavior as side chain LCP has been graft copolymerized onto high density polyethylene (HDPE) in order to improve its properties. The PALS analysis of the products displayed that the graft copolymerization, while led to relatively small increase in the free volume size at low percentages of poly(BPOCPMA), resulted in decreases in the size and fraction of the free volume with the increase of poly(BPOCPMA) content. The graft copolymerization gave rise to remarkable improvements in the mechanical properties, especially in tensile strength and modulus, and the improvements were accompanied by the decreases in the free volume fraction. SEM analysis of the fracture surfaces of the mechanical test samples displayed a gradual transition from ductile fracture at low graft contents to brittle nature dominated at high percentages of poly(BPOCPMA). The XRD analysis showed significant expansions in the lateral dimensions (a and b parameters) of the orthorhombic unit cell in the crystalline domains of HDPE matrix, in consistence with poly(BPOCPMA) content. The grafting also gave rise to noteworthy increases in the crystalline melting temperature of the HDPE.
Journal of the Turkish Chemical Society, Section A: Chemistry, Jan 30, 2015
The non-Newtonian viscosity of atactic and syndiotactic polystyrenes from 200 to 300˚C temperatur... more The non-Newtonian viscosity of atactic and syndiotactic polystyrenes from 200 to 300˚C temperature range at various pressures is described well using our recently proposed YDT (Yahsi-Dinc-Tav) and the Cross models [1]. The Pressure-Volume-Temperature (PVT) data of atactic and syndiotactic PSs are fitted to the Simha-Somcynsky equation of state (SS) [2],
A suspension of ultrasonically agitated Titanium dioxide micrometer-sized powder has been introdu... more A suspension of ultrasonically agitated Titanium dioxide micrometer-sized powder has been introduced into a poly(methyl methacrylate) (PMMA) matrix by solvent (CHCl3) mixing under slow mechanical stirring, and the resulting suspension was used to cast free-standing PMMA/TiO2 composite films. Filler contents from 0 wt% to 7.5 wt% were selected, since TiO2 particles could not be previously suspended in chloroform at higher concentrations by ultrasonic agitation. Optical and dielectric properties of composites were determined by ultraviolet (UV)-visible and dielectric spectrometry. In the UV region, 450% improvement of UV absorption was achieved in the TiO2/PMMA composite compared with neat PMMA. The structural properties and hole-free volume of the composites were determined by X-ray diffractometry and positron annihilation lifetime spectroscopy, respectively. The particle size and homogeneous dispersion of the particles in the polymer matrix were related to the hole-free volume of th...
2nd IET International Conference on Intelligent Signal Processing 2015 (ISP), 2015
Positron annihilation is a well-established technique for producing spectra which can be analyzed... more Positron annihilation is a well-established technique for producing spectra which can be analyzed for extracting physically meaningful parameters that characterize material defects and vacancies on an atomic scale. Mathematically, this is based on fitting a parameter-dependent model to the experimental data. Traditionally, this fit involves local nonlinear optimization routines that depend on a reasonable initial guess for the searched parameters. Therefore, very different sets of parameters may yield indistinguishably good fits for a given experimental spectrum but, give rise to ambiguities in data analysis. In order to alleviate them, a computer program has been developed for analyzing positron lifetime spectra by incorporating a global nonlinear optimization routine based on Simulated annealing (SA) into the Markov chain Monte-Carlo Bayesian inference algorithm (MCMC-BI) so that it provides a robust fitting tool and yields information on the reliability of the results. It is tested against experimental spectra, comparing the results with those from the well-established commercial programs.
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.
Radiation damage induced in Zircaloy-4 by 20 MeV Au ions was investigated using Grazing x-ray dif... more Radiation damage induced in Zircaloy-4 by 20 MeV Au ions was investigated using Grazing x-ray diffraction (GIXRD), positron annihilation techniques, micro-and nano-hardness techniques. The irradiations were performed at room temperature in the fluence range 1 × 1013–5 × 1014 ions cm−2 corresponding to 0.07–3.63 displacements per atom (dpa). The grazing incidence angle x-ray diffraction (GIXRD) revealed the presence of the hydride precipitates in the analyzed zircaloy-4. According to our experimental data it is found that the amount of these precipitates decreases after irradiation as emphasized by GIXRD and Positron Annihilation Lifetime Spectroscopy (PALS) results. The same data revealed also a zircaloy-4 swelling above a certain dose. From the combination of domain size/microstrain with the micro- and nano-hardness results, we conclude that the Zircaloy hardening is mainly due to the dislocation formation indicating the effect of the microstructure on the mechanical properties. Mo...
In this study, the nanostructural vacancy behavior of bovine derived hydroxyapatite (BHA) doped w... more In this study, the nanostructural vacancy behavior of bovine derived hydroxyapatite (BHA) doped with powder zirconmullite (ZM) contents of 5, 7.5, 10 and 12.5 wt.% were presented at sintering temperatures of 1000, 1100, 1200 and 1300°C. ZM‐doped BHA (ZM‐BHA) was characterized by X‐ray diffraction and positron annihilation lifetime spectroscopy (PALS). Density and hardness behavior were measured with respect to increasing sintering temperature. PALS results indicate that the longest lifetime component τ3 of ortho‐positronium (o‐Ps) localized at open spaces is attributed to the vacancy site and almost constant with the ZM contents and the sintering temperatures to have a mean value of 0.680 ns (corresponding to the radius of 0.997 nm). This average value is ascribed to the OH group defects along the main crystalline line. On the other hand, the o‐Ps intensity attributed to the number of vacancy sites increases almost linearly with ZM additives and sintering temperatures. The intensity...
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.
International Journal of Thermophysics, Nov 1, 2015
The non-Newtonian viscosity behavior of atactic and syndiotactic polystyrenes (aPS and sPS), at t... more The non-Newtonian viscosity behavior of atactic and syndiotactic polystyrenes (aPS and sPS), at temperatures from $$200\,{}^{\circ }\hbox {C}$$200∘C to $$300\,{}^{\circ }\hbox {C}$$300∘C and pressures up to 30 MPa, was studied using the recently proposed Yahsi–Dinc–Tav model, in particular, the Cross-like model. Viscosity data with shear rates of $$0.01\,\hbox {s}^{-1}$$0.01s-1 to $$5000\,\hbox {s}^{-1}$$5000s-1 were taken from literature at ambient pressure and were reproduced from the Cross-Vogel model at elevated pressures. The viscosities were predicted using the Yahsi–Dinc–Tav model with average absolute deviations of 4.37 % at ambient pressure and 9.63 % at high pressures for aPS and 2.54 % at ambient pressure and 4.79 % at high pressures for sPS. We extended this work to relate the zero shear and the constant shear rate viscosities in terms of the temperature- and pressure-dependent hole fraction using the thermo-occupancy function. The hole fraction (h) was computed from Simha–Somcynsky hole theory. Analytical relationships of specific density and hole fraction in terms of scaled temperature and pressure were constructed for practical purposes. The effects of tacticity of polystyrenes were discussed in terms of the thermo-occupancy function in detail. In particular, the derivative of the logarithm of the viscosities (viscoholibility) was found to decrease with an increasing hole fraction.
The elongational flow behavior of polyethylene, polypropylene, polystyrene, poly(methyl methacryl... more The elongational flow behavior of polyethylene, polypropylene, polystyrene, poly(methyl methacrylate), and polycarbonate, temperatures from 70 to 290 ∘ C and pressures up to 70 MPa, is examined with the Yahsi-Dinc-Tav (YDT) model and its particular case known as the Cross model. The viscosity data employed in the range of 3-405 s-1 elongational rates were acquired from the literature at ambient and elevated pressures. The predictions and the fitting results of the proposed YDT model with the same measurement data are compared with the Cross model. The average absolute deviations of the viscosities predicted by the YDT model range from 0.54% to 9.44% at ambient and 1.95% to 6.28% at high pressures. Additionally, the linear formulations derived from the YDT model are employed to relate the viscosity with temperature and hole fraction ("thermooccupancy" function) at zero level of elongational rate and constant elongational rate along with constant elongational stress. The effects of the four viscosity parameters (such as transmission and activation energy coefficients in these equations) on the elongational viscosity are analyzed in detail and some conclusions on the structural differences for the polymers are discussed.
Journal of the Chemical Society, Faraday Transactions, 1995
We have analysed the equation of states (eos) data for five series of compounds in terms of the S... more We have analysed the equation of states (eos) data for five series of compounds in terms of the Simha-Somcynsky hole theory and, in this manner, obtained graph-averaged temperature, volume and pressure scaling parameters. The eos data were obtained some time ago, when ...
This study brokes new ground to understand the insulation and permeability performances of rigid ... more This study brokes new ground to understand the insulation and permeability performances of rigid polyurethane foams (RPUFs) containing the different contents of micron-sized turkey feather powders (TFPs) depending on the free volume change for the first time. The effects of TFPs loading on the RPUFs were investigated by the examination of their structural and chemical features (particle size and ATR-FTIR analyses), free volume property (PALS analysis), insulation features (thermal conductivity and sound absorption tests), permeability performance (air and water vapor permeability tests) and cellular topology (SEM). PALS analysis results revealed that the addition of TFPs into the foams led to the sharp decrease in all free volume parameters since TFPs caused the formation of the disordered cells by occupying the holes in the matrix. Furthermore, both thermal conductivity and acoustic performance of the resulting foams get worse when compared to unfilled RPUF. This results were attri...
Neodymium-doped Y2Si2O7 nanopowders were synthesized by sol-gel and annealed under varying anneal... more Neodymium-doped Y2Si2O7 nanopowders were synthesized by sol-gel and annealed under varying annealing temperature conditions. The phase transformation of Y2Si2O7 and the crystalline size change were observed with annealing temperature. Photoluminescence and the decay patterns of the 4F3/2→ 4I9/2, 4I11/2, and 4I13/2 transitions were examined to reveal the spectroscopic characteristics of the powders. The spectral outputs of Nd3+:Y2Si2O7 phosphors remain strongly connected to the phase properties of Y2Si2O7. The positron lifetimes (τ 2, τ 3, and τ 4) and intensities (I 2, I 3, and I 4) obtained by positron annihilation lifetime spectroscopy were discussed for neodymium-doped Y2Si2O7 phosphors to relate the structural and boundary changes in terms of the phases and molar contents of the Nd3+ ions. The τ 2 and I 2 components were related to the structural open space in the grain, the τ 3 and I 3 components were correlated with vacancy-like defects in the grain boundaries, and the τ 4 and...
The monomer, p-benzophenoneoxycarbonylphenyl methacrylate (BPOCPMA) the polymer of which exhibit ... more The monomer, p-benzophenoneoxycarbonylphenyl methacrylate (BPOCPMA) the polymer of which exhibit mesomorphic behavior as side chain LCP has been graft copolymerized onto high density polyethylene (HDPE) in order to improve its properties. The PALS analysis of the products displayed that the graft copolymerization, while led to relatively small increase in the free volume size at low percentages of poly(BPOCPMA), resulted in decreases in the size and fraction of the free volume with the increase of poly(BPOCPMA) content. The graft copolymerization gave rise to remarkable improvements in the mechanical properties, especially in tensile strength and modulus, and the improvements were accompanied by the decreases in the free volume fraction. SEM analysis of the fracture surfaces of the mechanical test samples displayed a gradual transition from ductile fracture at low graft contents to brittle nature dominated at high percentages of poly(BPOCPMA). The XRD analysis showed significant expansions in the lateral dimensions (a and b parameters) of the orthorhombic unit cell in the crystalline domains of HDPE matrix, in consistence with poly(BPOCPMA) content. The grafting also gave rise to noteworthy increases in the crystalline melting temperature of the HDPE.
Journal of the Turkish Chemical Society, Section A: Chemistry, Jan 30, 2015
The non-Newtonian viscosity of atactic and syndiotactic polystyrenes from 200 to 300˚C temperatur... more The non-Newtonian viscosity of atactic and syndiotactic polystyrenes from 200 to 300˚C temperature range at various pressures is described well using our recently proposed YDT (Yahsi-Dinc-Tav) and the Cross models [1]. The Pressure-Volume-Temperature (PVT) data of atactic and syndiotactic PSs are fitted to the Simha-Somcynsky equation of state (SS) [2],
A suspension of ultrasonically agitated Titanium dioxide micrometer-sized powder has been introdu... more A suspension of ultrasonically agitated Titanium dioxide micrometer-sized powder has been introduced into a poly(methyl methacrylate) (PMMA) matrix by solvent (CHCl3) mixing under slow mechanical stirring, and the resulting suspension was used to cast free-standing PMMA/TiO2 composite films. Filler contents from 0 wt% to 7.5 wt% were selected, since TiO2 particles could not be previously suspended in chloroform at higher concentrations by ultrasonic agitation. Optical and dielectric properties of composites were determined by ultraviolet (UV)-visible and dielectric spectrometry. In the UV region, 450% improvement of UV absorption was achieved in the TiO2/PMMA composite compared with neat PMMA. The structural properties and hole-free volume of the composites were determined by X-ray diffractometry and positron annihilation lifetime spectroscopy, respectively. The particle size and homogeneous dispersion of the particles in the polymer matrix were related to the hole-free volume of th...
2nd IET International Conference on Intelligent Signal Processing 2015 (ISP), 2015
Positron annihilation is a well-established technique for producing spectra which can be analyzed... more Positron annihilation is a well-established technique for producing spectra which can be analyzed for extracting physically meaningful parameters that characterize material defects and vacancies on an atomic scale. Mathematically, this is based on fitting a parameter-dependent model to the experimental data. Traditionally, this fit involves local nonlinear optimization routines that depend on a reasonable initial guess for the searched parameters. Therefore, very different sets of parameters may yield indistinguishably good fits for a given experimental spectrum but, give rise to ambiguities in data analysis. In order to alleviate them, a computer program has been developed for analyzing positron lifetime spectra by incorporating a global nonlinear optimization routine based on Simulated annealing (SA) into the Markov chain Monte-Carlo Bayesian inference algorithm (MCMC-BI) so that it provides a robust fitting tool and yields information on the reliability of the results. It is tested against experimental spectra, comparing the results with those from the well-established commercial programs.
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.
Radiation damage induced in Zircaloy-4 by 20 MeV Au ions was investigated using Grazing x-ray dif... more Radiation damage induced in Zircaloy-4 by 20 MeV Au ions was investigated using Grazing x-ray diffraction (GIXRD), positron annihilation techniques, micro-and nano-hardness techniques. The irradiations were performed at room temperature in the fluence range 1 × 1013–5 × 1014 ions cm−2 corresponding to 0.07–3.63 displacements per atom (dpa). The grazing incidence angle x-ray diffraction (GIXRD) revealed the presence of the hydride precipitates in the analyzed zircaloy-4. According to our experimental data it is found that the amount of these precipitates decreases after irradiation as emphasized by GIXRD and Positron Annihilation Lifetime Spectroscopy (PALS) results. The same data revealed also a zircaloy-4 swelling above a certain dose. From the combination of domain size/microstrain with the micro- and nano-hardness results, we conclude that the Zircaloy hardening is mainly due to the dislocation formation indicating the effect of the microstructure on the mechanical properties. Mo...
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