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Öğe Cellular response to calcium phosphate cements(Elsevier, 2020) Cecen, Berivan; Kalemtaş, Ayşe; Topates, Gulsum; Kozaci, Leyla DidemCalcium 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.Öğe Gözenekli Kordiyerit Küre Üretim ve Karakterizasyonu(Afyon Kocatepe Üniversitesi, 2019) Kalemtaş, AyşeBu çalışmada milimetre boyutlarında küre formunda gözenekli kordiyerit seramiklerinin üretimi ve karakterizasyon çalışmaları gerçekleştirilmiştir. Kordiyerit küre üretiminde CC31, manyezit ve silika kullanılmıştır. Üretilen kürelere % 0, 5 ve 10 oranında nişasta ilave edilerek kürelerin farklı oranlarda gözenek içerecek şekilde üretilmesi sağlanmıştır. Tasarlanan bileşimler 1150 ve 1250C’de 1 saat süreyle atmosfer koşullarında 10C/dakika ısıtma ve soğutma hızı uygulanarak sinterlenmiştir. Sinterleme sonrası elde edilen kürelerin içyapı incelemeleri taramalı elektron mikroskobu ve faz analizleri x−ışını kırınım yöntemi ile gerçekleştirilmiştir. Taramalı elektron mikroskobu incelemeleri nişastanın yapıdan uzaklaşması sonucunda büyük gözeneklerin oluştuğunu göstermiştir. Ayrıca 1250C’de sinterlenen numunelerde kürelerin dışında ve iç kısmında oluşan içyapıların oldukça farklı olduğu gözlemlenmiştir. Ayrıca aynı sıcaklıkta sinterlenmesine rağmen nişasta ilavesinin de kürelerin dış kısmındaki içyapı gelişimine önemli ölçüde etki ettiği belirlenmiştir. Nişasta miktarı azaldıkça 1250C’de sinterlenen numunelerde kürelerin dışında oluşan kristallerin boy/en oranının arttığı ve daha ince kristallerin oluştuğu belirlenmiştir.Öğe Graphene oxide and zinc oxide decorated chitosan nanocomposite biofilms for packaging applications(Walter De Gruyter Gmbh, 2020) Terzioğlu, Pınar; Altin, Yasin; Kalemtaş, Ayşe; Bedeloğlu, AyşeRecently, 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 resulted in enhanced mechanical properties and thermal stability of chitosan biocomposite films. The graphene oxide- and zinc oxide-reinforced chitosan film showed 2527 MPa and 55.72 MPa of Young's modulus and tensile strength, respectively, while neat chitosan showed only 1549 MPa and 37.91 MPa of Young's modulus and tensile strength, respectively. Conversely, the addition of graphene oxide decreased the transmittance, notably in the UV region.Öğe Mechanical and antibacterial properties of ZnO/chitosan bio-composite films(WALTER DE GRUYTER, 2021) Kalemtaş, Ayşe; Koçer, Hasan Basri; Aydın, Ahmet; Terzioğlu, Pınar; Aydın, GülsümIn the current study, ZnO/chitosan bio-composite films were produced via solution-casting method. Two different ZnO powders, micrometer (d(50) approximately equal to 1.5 mu m) and nanometer sized (d(50) approximately equal to 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 pronounced for S. aureus and K. pneumoniae. Due to enhanced TS and imparted antibacterial activity of the produced ZnO/chitosan bio-composite films, these materials are promising candidates for applications such as food packaging, wound dressing, and antibacterial coatings for various surfaces.Öğe Natural calcium phosphates from fish bones and their potential biomedical applications(Elsevier Science Bv, 2018) Terzioğlu, Pınar; Öğüt, Hamdi; Kalemtaş, AyşeThe 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 presented in the light of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric-differential thermal analysis, bioactivity and biocompatibility investigations.Öğe Nişastayla Konsolidasyon Yöntemiyle Gözenekli Silika Esaslı Seramiklerin Üretimi(2016) Kalemtaş, AyşeBu çalışmada, nişastayla konsolidasyon yöntemi kullanılarak hazırlanan gözenekli kristobalit esaslı seramiklerin göreceli olarak düşük sıcaklıkta üretilmiştir. Başlangıç tozu olarak Si3N4 tozu, sinterleme ilavesi olarak ise boraksdekahidrat ile ticari bir kaolen kullanılmıştır. Gözenek oluşturucu olarak ise mısır nişastası kullanılmıştır. Sinterleme koşullarına bağlı olarak (1000-1200?C'de 1 saat sinterleme) oldukça düşük yığınsal yoğunluk (0,83-1,08 g/cm3) ve yüksek gözenekliliğe sahip seramiklerin üretildiği belirlenmiştir. Sinterleme hava atmosferinde gerçekleştirilmiş ve uygulanan ısıl işlem esnasında Si3N4tozunun oksidasyona uğraması sonucunda yapıda ana faz olarak kristobalit fazının oluştuğu XRD analizleriyle belirlenmiştir. Mikroyapı incelemelerinde nişastayla konsolidasyon yöntemiyle üretilen seramiklerin yüksek oranda gözeneğe sahip olduğu ve yapıda ortalama 80-100 µm ile birkaç µm ile sınırlı iki farklı boyut dağılımına sahip gözeneğin oluştuğu belirlenmiştir.Öğe Preparation and characterization of a novel ionizing electromagnetic radiation shielding material: Hematite filled polyester based composites(Pergamon-Elsevier Science Ltd, 2015) Belgin, E. Eren; Aycik, G. A.; Kalemtaş, Ayşe; Pelit, A.; Dilek, D. A.; Kayak, M. T.Isophthalic polyester (PES) based and natural mineral (hematite) filled composites were prepared and characterized for ionizing electromagnetic radiation shielding applications. Density evaluation and microscopic studies of the composites were carried out. Shielding performances of the composites were investigated for three different IEMR energy regions as low, intermediate and high. The mass attenuation coefficient of the prepared composites reached 98% of the elemental lead. In addition, the studied composites were superior to lead by virtue of their non-toxic nature. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Processing and applications of ceramic microspheres(Elsevier, 2021) Geçim, Gözde; Kalemtaş, AyşeThis chapter is focused on processing techniques for dense, porous, and hollow ceramic microspheres and their applications. A large number of studies focused on modeling and observations from nature revealed that complex pore networks have many advantages. However, fabrication of the designed pore architecture remains a challenge, notably for the porous microspheres. Newly developed hierarchically porous microstructure design possibilities by optimizing the ceramic spheres’ processing conditions via numerous processing techniques, such as templating, solvothermal, sol-gel, spray-drying, and emulsion processes, are discussed in this chapter. The important characteristics, such as type, diameter, thickness, and surface area, of the microspheres developed by various processes are also given.Öğe Processing of in-situ SiC reinforced AlN based composites(Korean Assoc Crystal Growth, Inc, 2018) Kalemtaş, Ayşe; Arslan, Gursoy; Kaya, Pinar; Turan, Servet; Kara, FerhatIn 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 alpha-Si3N4, alpha-Si3N4 + 4 wt. % carbon and alpha-Si3N4 + 8 wt. % carbon preforms at 1400 degrees C for 4 hours under an argon gas atmosphere. X-ray diffraction and transmission electron microscopy analysis of the designed alpha-Si3N4-Al and alpha-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 alpha-Si3N4 powder, which in turn consumes the liberated metallic Si phase in the system via chemical reactions leading to the formation of SiC ceramic phase. Formation of in-situ SiC, AlN and metallic Si were also confirmed by analytical transmission electron microscopy investigations.Öğe Processing of layered porous mullite ceramics(Springer, 2018) Kalemtaş, Ayşe; Ozey, Nigar; Aydin, Meryem Turkay AytekinIn the current study, layered porous mullite ceramics with different pore sizes were produced via polymeric sponge method by using CC31 commercial-grade kaolin as starting raw material. Polyurethane sponges with three different pore sizes (10, 20, and 30 ppi) changing from coarse to fine pores were physically assembled and then prepared ceramic slurry was impregnated into this structure to achieve the designed layered porous structure. After drying the polymeric sponges impregnated with the slurry, binder burnout and sintering studies were carried out. Phase composition and microstructure evolution of the porous samples, sintered at 1300 degrees-1600 degrees C for 1 and 3 h dwell time at a 3 degrees C/minute constant heating rate, were investigated. In situ mullite phase formation was achieved at all sintering conditions. It was determined that mullite grain morphology development strongly depends on the sintering temperature and time. Sintering at 1300 degrees C for 1 h resulted in the formation of equiaxed mullite grains. When the sintering temperature was increased to 1400 degrees C, first elongated fine mullite grains were achieved. Increasing dwell time at this temperature from 1 to 3 h resulted in more elongated mullite grain development. It was observed that aspect ratio of the mullite grains was significantly increased when the sintering temperature was increased to 1500 and 1600 degrees C. Scanning electron microscopy investigations demonstrated that the mullite needles do not reveal a significant preferred orientation and all porous mullite samples have uniform microstructure. It was determined that highly porous (60-70%) and light weight (0.7-1.1 g cm(-3)) layered mullite ceramics were fabricated.Öğe Production of Si3N4 porous beads via carbothermal reduction and nitridation technique(Taylor & Francis Ltd, 2020) Topates, Gulsum; Kalemtaş, AyşeSi(3)N(4)porous beads were produced from direct carbothermal reduction and nitridation of spheres composed of carbon+SiO(2)mixtures. A simple one-step sol-gel templating technique was used to prepare carbon+SiO2(molar ratio of carbon/SiO(2)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 Si(3)N(4)ceramic beads. Carbothermal reduction and nitridation process was conducted at two different temperatures (1500 and 1550 degrees 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 H(2)increased the amount of Si(3)N(4)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.Öğe Production, characterization, and cytotoxicity of calcium phosphate ceramics derived from the bone of meagre fish,Argyrosomus regius(Springer, 2021) Aydin, Gulsum; Terzioğlu, Pınar; Öğüt, Hamdi; Kalemtaş, AyşeHydroxyapatite ceramics derived from organic materials have similar physical properties and chemical content to stoichiometric hydroxyapatite ceramics produced via synthetic routes. The focus of the current study is to produce hydroxyapatite ceramics from meagre fish bones via calcination method. To the knowledge of the authors, this is the first report in which the meagre fish bones are used to produce hydroxyapatite. The effect of calcination temperature on the phase content, chemical composition, microstructure, and cytotoxic properties of hydroxyapatite ceramics produced from the bones of meagre fish,Argyrosomus regius, was investigated. Thermogravimetric-differential thermal analysis of the raw fish bones was performed over a temperature range of 20-1100 degrees C under air atmosphere with a heating rate of 10 degrees C/min. The total mass loss at this temperature range was about 59% for the fish bone. Thermal analysis of the sample exhibited a three major weight change stage. Calcination was performed in an air atmosphere at different calcination temperatures ranging from 800 to 1100 degrees C for 1 h. XRD analyses of the calcined fish bones revealed that the hydroxyapatite and whitlockite phases were formed at all calcination temperatures. Significantly marked alterations were observed at the microstructure of the samples depending on the calcination temperature. Scanning electron microscopy investigations revealed that nanocrystalline hydroxyapatite particles were achieved at 800 degrees C. As the calcination temperature was increased, particle size of the calcium phosphate phase was also increased and reached to approximately 1 mu m for the sample calcined at 1100 degrees C. Cytotoxicity evaluation of the hydroxyapatite carried out using XTT assay demonstrated that the materials are non-cytotoxic at concentrations up to 100 mg/ml.Öğe Review on extraction of polyhydroxyalkanoates and astaxanthin from food and beverage processing wastewater(Elsevier Ltd, 2021) Geçim, Gözde; Aydin, G.; Tavsanoglu, T.; Erkoç, Ertuğrul; Kalemtaş, AyşeThe recovery of value-added products from food and beverage processing wastewater, polyhydroxyalkanoates, and astaxanthin, via various chemical and microbiological extraction techniques has been summarized in this contribution. While wastewaters from several food industries like olive oil, brewery, starchy, and agro-cultural have been utilized to produce polyhydroxyalkanoates as an alternative to the petrochemical sources, seafood wastewaters such as mussel processing, shrimp cooking, and chitin production have been used to recover astaxanthin. In these studies, the wastewater's carbon content has been found as an essential parameter for the recovery of polyhydroxyalkanoates and astaxanthin. The type of additional nitrogen source, microorganism properties, ambient conditions, and polymer extraction methods were mostly examined parameters for the polyhydroxyalkanoate recovery. Olive oil mill wastewater has been presented as one of the most promising industries for the recovery of polyhydroxyalkanoate with the highest polymer yield of 4.93 g L?1. Shrimp cooking wastewaters provide one of the highest astaxanthin yields as 10–13 ?g mL?1. In addition to summarizing polyhydroxyalkanoates and astaxanthin yields from various wastewaters, technological obstacles and solutions regarding efficient extraction and large scale production have been discussed in this review. © 2020 Elsevier LtdÖğe Sodyum Borat Bağlı Gözenekli SiC-Si3N4 Kompozitlerin Üretim ve Karakterizasyonu(2016) Kalemtaş, Ayşe; Topateş, Gülsüm; Özey, Nigar; Bilgiç, OkanBu proje çalışması ile sodyumdekahidratın düşük sıcaklıkta akışkanlık özelliği kullanılarak saf SiC, Si3N4 ve SiC-Si3N4 kompozitler üretilmiştir. Yüksek miktarda gözenek elde edilmesi amacıyla nişasta kullanılmıştır. Malzemeler nişasta döküm veya presleme ile şekillendirilmiş ve sinterleme ise hava ortamında 575-1200?C arasında gerçekleşmiştir. SiC 600-700?C, Si3N4 1000-1200?C ve kompozit malzemeler ise 800-900?C arasında sinterlenmiştir. Sinterleme sonrasında yüksek açık gözeneğe ve yapısal bütünlüğe sahip numuneler elde edilmiştir. Üretilen numunelerin yoğunluk ve gözenek boyutu ölçülmüş, XRD ve SEM çalışmaları ile faz ve içyapı analizleri yapılmıştır. Nişasta döküm ile üretilen SiC numunelerinde ortalama gözenek boyutu 15-16 ?m olarak ölçülmüştür. XRD çalışmaları sonucunda SiC ve Si3N4 numunelerinde kristobalit fazı oluştuğu görülmüş, üç farklı yaklaşım ile bu fazın oluşumunun önüne geçilebilmiştir.Öğe Starch consolidation of SiC ceramics: processing and low-temperature sintering in an air atmosphere(Taylor & Francis Ltd, 2020) Kalemtaş, Ayşe; Topates, Gulsum; Aydin, M. Turkay Aytekin; Ozey, NigarHighly 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 degrees 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 degrees C, as a result of which sintering was carried out at the relatively low temperature, of 600 degrees 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 mu m 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.Öğe Usability of natural titanium-iron oxide as filler material for ionizing electromagnetic radiation shielding composites; preparation, characterization and performance(Springer, 2016) Belgin, E. Eren; Aycik, G. A.; Kalemtaş, Ayşe; Pelit, A.; Dilek, D. A.; Kavak, M. T.In the study, usability of natural titanium-iron oxide filler for ionizing electromagnetic radiation (IEMR) shielding composites with isophthalic polyester (PES) matrix was investigated for the first time. Shielding performances of the composites were also investigated for three different IEMR energy regions as low, intermediate and high for the first time, too. Mass attenuation coefficient of prepared composite with the best shielding performance reached 80 % of elemental lead's performance at low energy regions while it had higher mass attenuation coefficient at intermediate and high energies.
