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1

Investigation of Infrared and Raman Spectra of TeO_2-Nb_2O_5-TiO_2 Glasses

100%

Kabalci İ., Gökçe H.

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vol. 125

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issue 4

877-881

EN

X-ray diffraction, infrared (IR), Raman spectroscopy and scanning electron microscope techniques have been used to investigate the microstructural properties of the glass materials. In this work, a new type of tellurite based optical glasses with TeO_2/Nb_2O_5/TiO_2 for different xNb_2O_5 (x = 5, 10, 15, and 20 mol.%) glass compositions at constant 5 mol.% TiO_2 ratio were prepared. The effect of Nb_2O_5 contents on the structural unit of (95-x)TeO_2-(x)Nb_2O_5-5TiO_2 glass network, and the intensity ratios of the Raman peaks were investigated. The results indicate that for different Nb_2O_5 content 5 to 20 mol.% in the glass system, three vibrational peaks around 650, 800, and 920 cm^{-1} which correspond to the structural bonding of the glass were observed in the range of 500-2000 cm^{-1} for the IR spectra. Furthermore, from the Raman results a structural evolution was determined with the number of structural units such as [NbO_6]^{7-}, TeO_{3+1} (polyhedra), TeO_4 (trigonal bipyramids), TeO_3 (trigonal pyramids) or TeO_{3+1} (polyhedra), and [NbO_4]^{3-} for this ternary glass system.

2

Investigation of Indentation Fracture Toughness (KIC) and Weibull Parameters of 0.25Li2O.2SiO2-0.75BaO.2SiO2 Glass-Ceramic

71%

Ertuğ B., Nilgün Çetiner B., Gökçe H., Engin Erkmen Z., Lütfi Öveçoğlu M.

Archives of Metallurgy and Materials

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2017

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vol. 62

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issue 4

3

Effect of Different Phosphorus Precursors on Biomimetic Hydroxyapatite Powder Properties

71%

Karakaş A., Hazar Yoruç A., Gökçe H., Karabulut A., Ceylan Erdoğan D.

Acta Physica Polonica A

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2013

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vol. 123

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issue 2

418-420

EN

Hydroxyapatite is the main component of natural hard tissues, such as teeth and bone. It has been studied extensively as a candidate biomaterial for its use in prosthetic applications. Hydroxyapatite was formulated as Ca_{10}(PO_4)_6(OH)_2 and it has a high stability under physiological conditions. Also hydroxyapatite can be synthesized using different calcium and phosphorus precursors. In this study, biomimetic hydroxyapatite powder has been synthesized simulating physiological conditions. Synthetic body fluids which have the same composition as human blood plasma instead of pure water were used as precipitation media to obtain biological conditions. Recent research involved the effect of different Ca-precursors however aim of this study is to determine the effect of phosphorus resources. In this study, the synthesis of hydroxyapatite powder is carried out by using biomimetic method in synthetic body fluids. Calcium acetate [Ca(CH_3COO)_2, CA] and diammonium hydrogen phosphate [(NH_4)_2HPO_4, DAHP], ammonium dihydrogen phosphate [NH_4H_2PO_4, ADHP], dipotassium hydrogen phosphate [K_2HPO_4, DPHP] and orthophosphoric acid [H_3PO_4, OPA] were used as Ca- and P-precursors. Chemical structures of synthesized powders have been examined by Fourier transform infrared and X-ray diffraction. Results showed that synthesized powders have a pure hydroxyapatite structure. However, ADHP precursors have an unfavorable effect on sintered hydroxyapatite powders. Using ADHP phase transition was caused in pure hydroxyapatite structure and apatite and whitlockite were observed as secondary phases. Their particle size, surface area determination and morphological structures have been characterized by Zeta-Sizer, biomimetic hydroxyapatite the Brunauer-Emmett-Teller analysis and scanning electron microscopy images, respectively. As a result different starting materials have affected the structure, particle size and morphological properties of biomimetic hydroxyapatite.

4

Characterization Investigations of W-Ni Matrix Composites Reinforced with TiB_2 and La_2O_3

61%

Gökçe H., Balcı Ö., Ağaoğulları D., Demirkan Ö., Genç A., Öveçoğlu M., Duman İ.

Acta Physica Polonica A

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2013

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vol. 123

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issue 2

309-312

EN

W-1 wt% Ni (W1Ni) matrix composites reinforced with TiB_2 and La_2O_3 particles were fabricated via mechanical alloying and activated sintering methods. Powder blends with compositions of W1Ni-2 wt% TiB_2-x wt% La_2O_3 (x = 0.5, 1) were mechanically alloyed for 6 and 12 h. The results showed that increase in mechanical alloying duration to 12 h causes the decline of grain sizes of the W-Ni matrix to nanoscales. TiB_2/La_2O_3 particles have a significant effect on the density/microhardness values and wear amounts of the sintered samples.

5

The Effect of Mechanical Alloying on the Microhardness and Fracture Toughness of BaTiO_3

61%

Ertuğ B., Çetiner B., Sadullahoğlu G., Gökçe H., Erkmen Z., Öveçoğlu M.

Acta Physica Polonica A

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2013

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vol. 123

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issue 2

188-190

EN

In this work, the effects of mechanical alloying on the mechanical properties of BaTiO_3 were investigated. In order to examine the milling conditions and sintering parameters on the solid state formation of BaTiO_3, X-ray diffraction technique was used. After mechanical alloying process, nanosized powder mixtures were produced. Sintering temperatures were 600, 700, 800, 900, 1000, and 1200C and sintering duration was 1 h. Besides X-ray diffraction examinations, mechanical properties of the BaTiO_3 samples were determined by Vickers microhardness test.

6

The Effect of Milling Time and Sintering Temperature on Crystallization of BaFe₁₂O₁₉ Phase and Magnetic Properties of Ba-Hexaferrite Magnet

52%

Sadullahoğlu G., Ertuğ B., Gökçe H., Altuncevahir B., Öztürk M., Topkaya R., Akdoğan N., Öveçoğlu M., Addemir O.

Acta Physica Polonica A

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2015

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vol. 128

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issue 3

377-382

EN

Barium hexaferrite samples were prepared by mechanical alloying using the stoichiometric amounts of BaCO₃ and Fe₂O₃ precursors followed by heat treatment applied in the temperature range 700-1150°C. It was found that the high energy ball mill with a milling rate enabled to obtain powders with the finer particles at the reduced milling time mechanical alloying of the initial powders linked to the formation of barium hexaferrite phase. The exothermic reaction peaks corresponding to the formation of BaFe₁₂O₁₉ phase shift from 928°C to 793°C for the increased milling time up to 6 h. This was resulted in improved magnetic properties that the Mₛ value of the as-blended sample sintered at 800°C rised from 31.16 emu/g to 53.46 emu/g after milling for 6 h. The saturation magnetization and remanence values of the samples mechanically alloyed for 3 h and sintered at 1150°C also increased to 63.57 emu/g and 31.26 emu/g, respectively, more than for 800°C and 900°C. The increase in the annealing temperature favours the formation of BaFe₁₂O₁₉ phase in the samples.

7

Bioceramic Production from Sea Urchins

52%

Ağaoğullari D., Kel D., Gökçe H., Duman I., Öveçoğlu M., Akarsubaşi A., Bılgıç D., Oktar F.

Acta Physica Polonica A

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2012

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vol. 121

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issue 1

23-25

EN

Bioceramic nanopowders, currently one of the most demanding challenges for producing new biomaterials, have been tackled only when starting from chemical reagents. There are few studies aiming at producing hydroxyapatite nanopowders from naturally derived raw materials, such as nacre shells. Natural species of sea origin, such as corals and nacres, always attract special interest in biomaterials science and technology. Nacre shells are made up of pure aragonite crystallized in an organic matrix. The most common way to transform aragonite structures to hydroxyapatite is via hydrothermal transformation under very high pressure. However, such ways can be very dangerous if the equipment is worn. Ultrasonic and hotplate methods are apparently very safe. This work proposes a new approach for developing highly bioactive fine powders of Ca-phosphates (which can be used afterwards to build up hydroxyapatite-based bioceramic bone-scaffolds) from sea urchins via the above mentioned methods. The suspended raw powders were put on a hotplate (i.e. ultrasound). The temperature was set to 80C for 15 min and then, equivalent (to the amount of CaCO_3 in the sea urchins) amount of H_3PO_4 was added drop by drop into the solution. The reaction continued for 2 h. Then, to evaporate the liquid part, the mixture was put into an incubator at 100C for 24 h and the resultant dried sediment was collected. X-ray diffraction analysis identified various calcium phosphate phases, predominantly monetite, and tricalcium phosphate as a secondary phase. The worldwide availability and the low cost of all kinds of nacre and sea urchin shells, along with their biological-natural origin are attractive features conferring to them a high potential for preparing calcium phosphate materials for uses in biomedicine. Heart urchin, used in this study, can be an ideal candidate for producing bioceramic particles.

8

Nano-Bioceramic Synthesis from Tropical Sea Snail Shells (Tiger Cowrie - Cypraea Tigris) with Simple Chemical Treatment

52%

Şahin Y., Gündüz O., Bulut B., Özyeğin L., Gökçe H., Ağaoğulları D., Chou J., Kayalı E., Ben-Nissan B., Oktar F.

Acta Physica Polonica A

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2015

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vol. 127

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issue 4

1055-1058

EN

In this study several bioceramic materials (i.e. hydroxyapatite, whitlockite) were prepared by using chemical synthesis method from sea snail shells (Tiger Cowrie - Cypraea Tigris), originated from Pacific Ocean. Marine shells usually present aragonite-calcite structures and generally, complicated and pressurized equipment is necessary to convert these structures into bioceramics. Instead of using complicated systems, a basic ultrasonic equipment and simple chemical synthesis method was used in the process. DTA analysis was performed to calculate the required amount of H₃PO₄ solution in order to set the appropriate stoichiometric ratio of Ca/P equal to 1.667 for HA bioceramic or to 1.5 for β-TCP bioceramic in the titration. The prepared batches were sintered at 800°C and 400°C for hydroxyapatite (HA) and β-tri calcium phosphate (β-TCP) forms respectively. X-ray diffraction analysis, scanning electron microscopy (SEM) and infrared observations (FTIR) were implemented for both TCP and HA bioceramics. By applying the chemical synthesis with basic ultrasonic equipment, this study proposes a simple way of production for nano-HA /TCP powders from a natural marine sources.

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Investigation of Infrared and Raman Spectra of TeO_2-Nb_2O_5-TiO_2 Glasses

Investigation of Indentation Fracture Toughness (KIC) and Weibull Parameters of 0.25Li2O.2SiO2-0.75BaO.2SiO2 Glass-Ceramic

Effect of Different Phosphorus Precursors on Biomimetic Hydroxyapatite Powder Properties

Characterization Investigations of W-Ni Matrix Composites Reinforced with TiB_2 and La_2O_3

The Effect of Mechanical Alloying on the Microhardness and Fracture Toughness of BaTiO_3

The Effect of Milling Time and Sintering Temperature on Crystallization of BaFe₁₂O₁₉ Phase and Magnetic Properties of Ba-Hexaferrite Magnet

Bioceramic Production from Sea Urchins

Nano-Bioceramic Synthesis from Tropical Sea Snail Shells (Tiger Cowrie - Cypraea Tigris) with Simple Chemical Treatment