Ayse Kalemtas | Bursa Technical University (original) (raw)

Papers by Ayse Kalemtas

Handbook of Biomaterials Biocompatibility

Abstract Calcium orthophosphate (COP) ceramics have been investigated as bone repair materials fo... more Abstract Calcium orthophosphate (COP) ceramics have been investigated as bone repair materials for many decades. The first in vivo application of these materials was accomplished in 1920 to test tricalcium phosphate performance as a bone substitute. Since this first attempt, various COPs were investigated on animals to shed light on their effect on the healing behavior of bones. Calcium phosphate cements are currently receiving a great deal of interest especially for the hard tissue repair, augmentation, and regeneration applications due to their attractive characteristics such as biocompatibility, ease of shaping, osteoconductivity, and biodegradability.

Türkiye Klinikleri Gıda Bilimleri - Özel Konular, 2021

Journal of Asian Ceramic Societies, 2020

ABSTRACT Si3N4 porous beads were produced from direct carbothermal reduction and nitridation of s... more ABSTRACT Si3N4 porous beads were produced from direct carbothermal reduction and nitridation of spheres composed of carbon+SiO2 mixtures. A simple one–step sol–gel templating technique was used to prepare carbon+SiO2 (molar ratio of carbon/SiO2 was set as 4) containing spheres with a diameter of 2 mm. A natural and abundant biopolymer, alginate, is used as a sacrificial template to produce porous Si3N4 ceramic beads. Carbothermal reduction and nitridation process was conducted at two different temperatures (1500 and 1550°C) and atmospheres (pure nitrogen and 5% hydrogen in nitrogen) to observe the effect of process parameters on the yield of Si3N4. Porous beads with a smooth shape and without any deformation were successfully obtained after the carbothermal reduction and nitridation process. X–ray powder diffraction studies showed that the use of H2 increased the amount of Si3N4 formed by accelerating the reduction and nitridation reactions. Microstructural investigations revealed oxide addition changed grain morphology from fiber–like to short, angular geometry. This microstructural development showed that the addition of oxide powder increased the amount of liquid phase formed during the heat treatment process and changed carbothermal reduction and nitridation mechanism from vapor–solid to vapor–liquid solid.

In this work, the production of light (∼2,9 g/cm3) and dense (> 99 %) AlN based ceramic metal ... more In this work, the production of light (∼2,9 g/cm3) and dense (> 99 %) AlN based ceramic metal composites was conducted by the pressureless melt infiltration method. These composites contain a high ceramic volume fraction (> 50 vol %) which is the result of the reaction between Si3N 4 and Al in the Si 3N 4-Al system. The production of the ceramic-metal composites was achieved via infiltrating 2024 Al alloys at different temperatures and holding times into the porous pellets which were prepared using α-Si 3N 4 powder. These experiments were conduced in two ways: (i) Infiltration at a constant holding time (1 h) in the temperature range of 900-1400°C at intervals of 100°C. (ii) Infiltration at a constant infiltration temperature (1200° C) with a holding time in the range of 1 - 5 h at intervals of 1 h. Qualitative phase analysis of the produced composites confirmed the exisitence of the AlN, Si, Al and CuAl 2 phases in the microstructure and revealed that the Si 3N 4 phase was co...

Journal of Polymer Engineering, 2021

In the current study, ZnO/chitosan bio-composite films were produced via solution-casting method.... more In the current study, ZnO/chitosan bio-composite films were produced via solution-casting method. Two different ZnO powders, micrometer (d50 ≅ 1.5 μm) and nanometer sized (d50 ≅ 100 nm), were used to investigate the effect of ZnO particle size and concentration (0, 2, and 8% w/w of chitosan) on the mechanical and antibacterial properties of the ZnO/chitosan bio-composite films. The incorporation of the ZnO powders into the chitosan film resulted in an increase in the tensile strength (TS) and a decrease in the elongation at break (EB) values. Mechanical test results revealed that TS and EB properties were considerably affected (p < 0.05) by the concentration and particle size of the ZnO reinforcement. Disc diffusion method demonstrated good antibacterial activities of bio-composite films containing high amount of ZnO (8% w/w of chitosan) against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Bacillus subtilis. The growth-limiting effect of the films was more ...

Material Science Research India, 2019

In this study, a simple, innovative approach is applied to produce porous a-TCP-CeO2-Al2O3 compos... more In this study, a simple, innovative approach is applied to produce porous a-TCP-CeO2-Al2O3 composite beads via using bovine bone-derived hydroxyapatite, cerium oxide, and alumina ceramics. Bovine-bone derived hydroxyapatite was obtained via calcination of bones at 950°C for 3 hours. Hydroxyapatite is a thermally unstable biomaterial at high temperatures, and depending on its stoichiometry decomposes at 800-1200°C. Sodium alginate was successfully used as an in situ gelling templates for the production of the ceramic beads and starch, an environmentally friendly and economic pore-forming agent, is used to achieve interconnected, highly open porosity containing composite beads. Sintering of the ceramic−starch−alginate green composite beads at 1200°C for 1 hour resulted in the decomposition of the hydroxyapatite phase and formation of a-TCP. XRD analysis revealed that a-TCP-CeO2-Al2O3 composite beads were achieved. XRD analysis confirmed the formation of a-TCP phase in all composite co...

In this study, highly dense (>97%) in-situ SiC reinforced AlN based ceramic-metal composites w... more In this study, highly dense (>97%) in-situ SiC reinforced AlN based ceramic-metal composites were produced by pressureless reactive infiltration of 7075 aluminium alloys into porous α-Si3N4, α-Si3N4 + 4 wt. % carbon and α-Si3N4 + 8 wt. % carbon preforms at 1400 C for 4 hours under an argon gas atmosphere. X-ray diffraction and transmission electron microscopy analysis of the designed α-Si3N4-Al and α-Si3N4-C-Al composites revealed that Si3N4 was completely consumed during the infiltration process via reacting with the Al alloy and resulted in the formation of AlN and Si phases. The aim of the current work was to introduce a novel method to produce in-situ SiC reinforced AlN based ceramic-metal composites. Composites with relatively low metal contents were successfully fabricated through incorporating active carbon to the starting α-Si3N4 powder, which in turn consumes the liberated metallic Si phase in the system via chemical reactions leading to the formation of SiC ceramic phas...

Globally increased bivalve aquaculture production results in a vast amount of by-product discharg... more Globally increased bivalve aquaculture production results in a vast amount of by-product discharges such as scallop shells. Utilization of these wastes to produce new products such as antibacterial agents can cooperate to reduce environmental problems and provide a high value-added product at a lower cost. In this study, scallop shells are heat-treated at 800°, 900°, 1000°, and 1100°C for 4 hours at atmospheric conditions. X-ray diffraction analysis revealed that calcium carbonate is the only inorganic phase in the powdered scallop shells. Ten weeks after the thermal treatment of the scallop shells, the calcium hydroxide phase was the only crystalline phase determined by X-ray diffraction analysis for the samples calcined at 1000° and 1100°C. At lower calcination temperatures, calcium carbonate and calcium hydroxide phases were co-existing in the samples. Scanning electron microscopy investigations depicted that using scallop shells as a starting material to synthesize nanometer-siz...

Advanced Welding and Deforming

Journal of the Australian Ceramic Society

Journal of Water Process Engineering

Journal of Polymer Engineering

Recently, due to sustainable development and environmental protection policies, there is increasi... more Recently, due to sustainable development and environmental protection policies, there is increasing interest in the development of new biodegradable polymer-based multifunctional composites. Chitosan is one of the most remarkable and preferred biopolymers, which is environmentally friendly as well as renewable, biocompatible, and inexpensive. Though it has a wide range of potential applications, the major limitation of chitosan – the problem of poor mechanical performance – needs to be solved. In this work, graphene oxide was first produced and then used to manufacture a chitosan/graphene oxide/zinc oxide composite film through a casting method. The properties of the chitosan film and the chitosan/graphene oxide/zinc oxide composite film were investigated using Fourier transform infrared spectroscopy, mechanical, thermal gravimetric, and ultraviolet (UV)-visible spectroscopy analyses. The results showed that the incorporation of graphene oxide and zinc oxide into the chitosan matrix...

Journal of Asian Ceramic Societies

Highly porous SiC ceramics containing borax decahydrate were produced by a starch consolidation m... more Highly porous SiC ceramics containing borax decahydrate were produced by a starch consolidation method in which corn starch was used as a shaping and pore-forming additive. Four different compositions were prepared with different SiC:borax decahydrate ratios and corn starch content. Mixtures with a solid ratio of 55 wt.% were cast in non-porous molds and heated at 80°C for shaping. The starch consolidation technique enabled the shaping of SiC ceramics with different forms and sizes. Simultaneous thermogravimetry and differential thermal analysis of the SiC-borax decahydrate mixture showed that melting took place at below 600°C, as a result of which sintering was carried out at the relatively low temperature, of 600°C in the air using borax decahydrate as a sintering additive. Phase analysis showed that oxidation of SiC did not take place, since no cristobalite phase was detected. Density measurement and mercury porosimetry studies showed that highly porous (70-89% porosity) SiC ceramics with pore size values ranging from 14 to 18 μm were produced. SEM microstructures of each composition revealed that a strong neck had been formed between the SiC particles in spite of the low sintering temperature.

Material Science Research India

In the current study, sodium borate-bonded highly open porous ceramics successfully produced by s... more In the current study, sodium borate-bonded highly open porous ceramics successfully produced by starch consolidation technique. Open porous ceramic production was carried out by using an economical grade a-Si3N4, corn starch, CC31 commercial-grade kaolin, and borax decahydrate (Na2B4O7.10H2O). Borax decahydrate was used as a sintering aid in the system and total ceramic (a-Si3N4 + CC31): borax decahydrate ratio was kept constant at 5:1. Sintering studies of the shaped samples carried out in an air atmosphere at a relatively low sintering temperature, 1100°C, for one hour. Scanning electron microscopy investigations of the porous ceramic samples revealed that due to the high amount of borax based sintering additive a significant amount of liquid phase formed during the sintering process of the designed ceramics. Highly open porous(~66-74%) and lightweight(~0.64-0.83 g/cm3) ceramics were produced via starch consolidation technique and low-temperature sintering at atmospheric conditions.

Material Science Research India

In this study, kaolin bonded alumina-alginate composite beads were fabricated via a facile one-st... more In this study, kaolin bonded alumina-alginate composite beads were fabricated via a facile one-step sol-gel process by using sodium alginate. In order to achieve sintering of the beads at lower sintering temperatures a limited amount of CC31 commercial-grade kaolin was used as a sintering additive (Al2O3:CC31 commercial-grade kaolin=14:1). Produced composite beads were heat treated at 1300°, 1400° and 1500°C for 1 hour to achieve partial densification of the beads. TG-DTA analysis of the CC31 commercial-grade kaolin showed that mullite phase formation took place approximately at 1000°C. However, XRD measurements revealed that there is only alumina phase in the sintered ceramic beads. Due to the low amount of CC31 commercial-grade kaolin, mullite formation was not detectable via XRD analysis. No significant grain growth was observed at the sintered samples depending on the increasing sintering temperature. However, when the sintering temperature was increased, densification ratio and...

Materials science & engineering. C, Materials for biological applications, 2018

The treatment and recovery of bio-wastes have raised considerable attention both from the environ... more The treatment and recovery of bio-wastes have raised considerable attention both from the environmental and economic point of view. Every year, a remarkable amount of fish processing by-products are generated and dumped as waste from all over the world. Fish bones can serve as a raw material for the production of high value-added compounds that can be used in various sectors including agrochemical, biomedical, food and pharmaceutical industries. The calcination of fish bones results in a single phase (hydroxyapatite) or bi-phasic (hydroxyapatite-tricalcium phosphate) bioceramics depending on the processing conditions as well as the content of the fish bones. This review summarizes the literature on the production of hydroxyapatite from fish bones and discusses their potential applications in biomedical field. The effect of processing conditions on the properties of final products including Ca/P ratio, crystal structure, particle shape, particle size and biological properties are pre...

Journal of Material Science & Engineering

Handbook of Biomaterials Biocompatibility

Abstract Calcium orthophosphate (COP) ceramics have been investigated as bone repair materials fo... more Abstract Calcium orthophosphate (COP) ceramics have been investigated as bone repair materials for many decades. The first in vivo application of these materials was accomplished in 1920 to test tricalcium phosphate performance as a bone substitute. Since this first attempt, various COPs were investigated on animals to shed light on their effect on the healing behavior of bones. Calcium phosphate cements are currently receiving a great deal of interest especially for the hard tissue repair, augmentation, and regeneration applications due to their attractive characteristics such as biocompatibility, ease of shaping, osteoconductivity, and biodegradability.

Türkiye Klinikleri Gıda Bilimleri - Özel Konular, 2021

Journal of Asian Ceramic Societies, 2020

ABSTRACT Si3N4 porous beads were produced from direct carbothermal reduction and nitridation of s... more ABSTRACT Si3N4 porous beads were produced from direct carbothermal reduction and nitridation of spheres composed of carbon+SiO2 mixtures. A simple one–step sol–gel templating technique was used to prepare carbon+SiO2 (molar ratio of carbon/SiO2 was set as 4) containing spheres with a diameter of 2 mm. A natural and abundant biopolymer, alginate, is used as a sacrificial template to produce porous Si3N4 ceramic beads. Carbothermal reduction and nitridation process was conducted at two different temperatures (1500 and 1550°C) and atmospheres (pure nitrogen and 5% hydrogen in nitrogen) to observe the effect of process parameters on the yield of Si3N4. Porous beads with a smooth shape and without any deformation were successfully obtained after the carbothermal reduction and nitridation process. X–ray powder diffraction studies showed that the use of H2 increased the amount of Si3N4 formed by accelerating the reduction and nitridation reactions. Microstructural investigations revealed oxide addition changed grain morphology from fiber–like to short, angular geometry. This microstructural development showed that the addition of oxide powder increased the amount of liquid phase formed during the heat treatment process and changed carbothermal reduction and nitridation mechanism from vapor–solid to vapor–liquid solid.

In this work, the production of light (∼2,9 g/cm3) and dense (> 99 %) AlN based ceramic metal ... more In this work, the production of light (∼2,9 g/cm3) and dense (> 99 %) AlN based ceramic metal composites was conducted by the pressureless melt infiltration method. These composites contain a high ceramic volume fraction (> 50 vol %) which is the result of the reaction between Si3N 4 and Al in the Si 3N 4-Al system. The production of the ceramic-metal composites was achieved via infiltrating 2024 Al alloys at different temperatures and holding times into the porous pellets which were prepared using α-Si 3N 4 powder. These experiments were conduced in two ways: (i) Infiltration at a constant holding time (1 h) in the temperature range of 900-1400°C at intervals of 100°C. (ii) Infiltration at a constant infiltration temperature (1200° C) with a holding time in the range of 1 - 5 h at intervals of 1 h. Qualitative phase analysis of the produced composites confirmed the exisitence of the AlN, Si, Al and CuAl 2 phases in the microstructure and revealed that the Si 3N 4 phase was co...

Journal of Polymer Engineering, 2021

In the current study, ZnO/chitosan bio-composite films were produced via solution-casting method.... more In the current study, ZnO/chitosan bio-composite films were produced via solution-casting method. Two different ZnO powders, micrometer (d50 ≅ 1.5 μm) and nanometer sized (d50 ≅ 100 nm), were used to investigate the effect of ZnO particle size and concentration (0, 2, and 8% w/w of chitosan) on the mechanical and antibacterial properties of the ZnO/chitosan bio-composite films. The incorporation of the ZnO powders into the chitosan film resulted in an increase in the tensile strength (TS) and a decrease in the elongation at break (EB) values. Mechanical test results revealed that TS and EB properties were considerably affected (p < 0.05) by the concentration and particle size of the ZnO reinforcement. Disc diffusion method demonstrated good antibacterial activities of bio-composite films containing high amount of ZnO (8% w/w of chitosan) against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Bacillus subtilis. The growth-limiting effect of the films was more ...

Material Science Research India, 2019

In this study, a simple, innovative approach is applied to produce porous a-TCP-CeO2-Al2O3 compos... more In this study, a simple, innovative approach is applied to produce porous a-TCP-CeO2-Al2O3 composite beads via using bovine bone-derived hydroxyapatite, cerium oxide, and alumina ceramics. Bovine-bone derived hydroxyapatite was obtained via calcination of bones at 950°C for 3 hours. Hydroxyapatite is a thermally unstable biomaterial at high temperatures, and depending on its stoichiometry decomposes at 800-1200°C. Sodium alginate was successfully used as an in situ gelling templates for the production of the ceramic beads and starch, an environmentally friendly and economic pore-forming agent, is used to achieve interconnected, highly open porosity containing composite beads. Sintering of the ceramic−starch−alginate green composite beads at 1200°C for 1 hour resulted in the decomposition of the hydroxyapatite phase and formation of a-TCP. XRD analysis revealed that a-TCP-CeO2-Al2O3 composite beads were achieved. XRD analysis confirmed the formation of a-TCP phase in all composite co...

In this study, highly dense (>97%) in-situ SiC reinforced AlN based ceramic-metal composites w... more In this study, highly dense (>97%) in-situ SiC reinforced AlN based ceramic-metal composites were produced by pressureless reactive infiltration of 7075 aluminium alloys into porous α-Si3N4, α-Si3N4 + 4 wt. % carbon and α-Si3N4 + 8 wt. % carbon preforms at 1400 C for 4 hours under an argon gas atmosphere. X-ray diffraction and transmission electron microscopy analysis of the designed α-Si3N4-Al and α-Si3N4-C-Al composites revealed that Si3N4 was completely consumed during the infiltration process via reacting with the Al alloy and resulted in the formation of AlN and Si phases. The aim of the current work was to introduce a novel method to produce in-situ SiC reinforced AlN based ceramic-metal composites. Composites with relatively low metal contents were successfully fabricated through incorporating active carbon to the starting α-Si3N4 powder, which in turn consumes the liberated metallic Si phase in the system via chemical reactions leading to the formation of SiC ceramic phas...

Globally increased bivalve aquaculture production results in a vast amount of by-product discharg... more Globally increased bivalve aquaculture production results in a vast amount of by-product discharges such as scallop shells. Utilization of these wastes to produce new products such as antibacterial agents can cooperate to reduce environmental problems and provide a high value-added product at a lower cost. In this study, scallop shells are heat-treated at 800°, 900°, 1000°, and 1100°C for 4 hours at atmospheric conditions. X-ray diffraction analysis revealed that calcium carbonate is the only inorganic phase in the powdered scallop shells. Ten weeks after the thermal treatment of the scallop shells, the calcium hydroxide phase was the only crystalline phase determined by X-ray diffraction analysis for the samples calcined at 1000° and 1100°C. At lower calcination temperatures, calcium carbonate and calcium hydroxide phases were co-existing in the samples. Scanning electron microscopy investigations depicted that using scallop shells as a starting material to synthesize nanometer-siz...

Advanced Welding and Deforming

Journal of the Australian Ceramic Society

Journal of Water Process Engineering

Journal of Polymer Engineering

Recently, due to sustainable development and environmental protection policies, there is increasi... more Recently, due to sustainable development and environmental protection policies, there is increasing interest in the development of new biodegradable polymer-based multifunctional composites. Chitosan is one of the most remarkable and preferred biopolymers, which is environmentally friendly as well as renewable, biocompatible, and inexpensive. Though it has a wide range of potential applications, the major limitation of chitosan – the problem of poor mechanical performance – needs to be solved. In this work, graphene oxide was first produced and then used to manufacture a chitosan/graphene oxide/zinc oxide composite film through a casting method. The properties of the chitosan film and the chitosan/graphene oxide/zinc oxide composite film were investigated using Fourier transform infrared spectroscopy, mechanical, thermal gravimetric, and ultraviolet (UV)-visible spectroscopy analyses. The results showed that the incorporation of graphene oxide and zinc oxide into the chitosan matrix...

Journal of Asian Ceramic Societies

Highly porous SiC ceramics containing borax decahydrate were produced by a starch consolidation m... more Highly porous SiC ceramics containing borax decahydrate were produced by a starch consolidation method in which corn starch was used as a shaping and pore-forming additive. Four different compositions were prepared with different SiC:borax decahydrate ratios and corn starch content. Mixtures with a solid ratio of 55 wt.% were cast in non-porous molds and heated at 80°C for shaping. The starch consolidation technique enabled the shaping of SiC ceramics with different forms and sizes. Simultaneous thermogravimetry and differential thermal analysis of the SiC-borax decahydrate mixture showed that melting took place at below 600°C, as a result of which sintering was carried out at the relatively low temperature, of 600°C in the air using borax decahydrate as a sintering additive. Phase analysis showed that oxidation of SiC did not take place, since no cristobalite phase was detected. Density measurement and mercury porosimetry studies showed that highly porous (70-89% porosity) SiC ceramics with pore size values ranging from 14 to 18 μm were produced. SEM microstructures of each composition revealed that a strong neck had been formed between the SiC particles in spite of the low sintering temperature.

Material Science Research India

In the current study, sodium borate-bonded highly open porous ceramics successfully produced by s... more In the current study, sodium borate-bonded highly open porous ceramics successfully produced by starch consolidation technique. Open porous ceramic production was carried out by using an economical grade a-Si3N4, corn starch, CC31 commercial-grade kaolin, and borax decahydrate (Na2B4O7.10H2O). Borax decahydrate was used as a sintering aid in the system and total ceramic (a-Si3N4 + CC31): borax decahydrate ratio was kept constant at 5:1. Sintering studies of the shaped samples carried out in an air atmosphere at a relatively low sintering temperature, 1100°C, for one hour. Scanning electron microscopy investigations of the porous ceramic samples revealed that due to the high amount of borax based sintering additive a significant amount of liquid phase formed during the sintering process of the designed ceramics. Highly open porous(~66-74%) and lightweight(~0.64-0.83 g/cm3) ceramics were produced via starch consolidation technique and low-temperature sintering at atmospheric conditions.

Material Science Research India

In this study, kaolin bonded alumina-alginate composite beads were fabricated via a facile one-st... more In this study, kaolin bonded alumina-alginate composite beads were fabricated via a facile one-step sol-gel process by using sodium alginate. In order to achieve sintering of the beads at lower sintering temperatures a limited amount of CC31 commercial-grade kaolin was used as a sintering additive (Al2O3:CC31 commercial-grade kaolin=14:1). Produced composite beads were heat treated at 1300°, 1400° and 1500°C for 1 hour to achieve partial densification of the beads. TG-DTA analysis of the CC31 commercial-grade kaolin showed that mullite phase formation took place approximately at 1000°C. However, XRD measurements revealed that there is only alumina phase in the sintered ceramic beads. Due to the low amount of CC31 commercial-grade kaolin, mullite formation was not detectable via XRD analysis. No significant grain growth was observed at the sintered samples depending on the increasing sintering temperature. However, when the sintering temperature was increased, densification ratio and...

Materials science & engineering. C, Materials for biological applications, 2018

The treatment and recovery of bio-wastes have raised considerable attention both from the environ... more The treatment and recovery of bio-wastes have raised considerable attention both from the environmental and economic point of view. Every year, a remarkable amount of fish processing by-products are generated and dumped as waste from all over the world. Fish bones can serve as a raw material for the production of high value-added compounds that can be used in various sectors including agrochemical, biomedical, food and pharmaceutical industries. The calcination of fish bones results in a single phase (hydroxyapatite) or bi-phasic (hydroxyapatite-tricalcium phosphate) bioceramics depending on the processing conditions as well as the content of the fish bones. This review summarizes the literature on the production of hydroxyapatite from fish bones and discusses their potential applications in biomedical field. The effect of processing conditions on the properties of final products including Ca/P ratio, crystal structure, particle shape, particle size and biological properties are pre...

Journal of Material Science & Engineering