MCBÜ Açıkerişim Sistemi :: Browsing by Author "Koç, M"

Browsing by Author "Koç, M"

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Fabrication and Characterization of High Performance PVDF-based flexible piezoelectric nanogenerators using PMN-xPT (x:30, 32.5, and 35) particles
Parali, L; Koç, M; Akça, E
Flexible piezoelectric nanogenerators based on polyvinylidene difluoride (PVDF) and lead magnesium niobatelead titanate Pb(Mg1/3Nb2/3)O3-PbTiO3(PMN-xPT compositions for x between 30 and 35) particles with various filler ratios from 10 to 30 vol% were fabricated through the electrospinning method. The phase and microstructural characterizations revealed that the homogenous and continuous fiber-shaped composite structure with good interfacial interaction between the PMN-PT particles and the PVDF matrix was achieved. It was found that the diameter of the neat PVDF fibers was approximately 354 nm, whereas the PVDF/PMN-35PT fibers with ceramic particle concentrations of 10, 20, and 30 vol% had average diameters of 317, 249, and 163 nm, respectively. The piezoelectric performance tests indicated that the 30 vol%PVDF/PMN-35PT nanogenerator had a 3 times greater electrical power efficiency (10.59 mu W) at 20 Hz compared to that of the pure PVDF nanogenerator (3.56 mu W) at 15 Hz under the same resistance load of 1 M omega. All in all, the incorporation of PMNT-PT particles into the PVDF appears to be a good approach for the fabrication of high-performance flexible piezoelectric nanogenerator applications for biomechanical energy harvesting of devices converting the mechanical movements of organs such as cardiac and lung into electrical energy.
Physicochemical Characterization of Whole Egg Powder Microencapsulated by Spray Drying
Koç, M; Koç, B; Yilmazer, MS; Ertekin, FK; Susyal, G; Bagdatlioglu, N
Physical characterization and oxidative stability of egg powder microencapsulated by spray drying were studied in this work. The wall material (gelatin, lactose, pullulan, and their mixtures) and liquid egg mixtures were prepared by homogenization at 22,000 rpm for 60s. The spray drying was carried out at pilot-scale spray dryer (Niro Mobile Minor, Soborg, Denmark). The spray-dried egg powders were analyzed for moisture content, water activity, peroxide value, total cholesterol oxidation products (TCOPs), particle properties, and bulk properties. Using gelatin as wall material resulted in a significant increase in the moisture content and water activity of egg powder during storage and it improved flowability. Egg powders containing pullulan as wall material showed a fibrous structure and had the lowest bulk density. Adding lactose as wall material increased the oxidative stability, which was indicated with lowest peroxide value and TCOPs level of egg powder.
2D/3D Direct Writing of Thermoplastics through Electrohydrodynamic Printing
Parali, L; Koç, M; Yildiz, Z
This paper describes a novel electro hybrid mechanical system which consists of the following components: electrohydrodynamic printing combined with the fused deposition modeling, electrospinning, and electrospray. The electrohydrodynamic printing section with the fused deposition modeling of the electro hybrid mechanical system was used to obtain fibers from thermoplastics such as polylactic acid, thermoplastic polyurethane, polyethylene terephthalate-glycol, acrylonitrile-butadiene-styrene copolymer, and high impact polystyrene. This study reports the changes in the 2D array and the 3D scaffold structure of the samples and exhibits their characteristics and performance evaluations by comparing them under the same production conditions.
The effect of marble waste in the production of low-temperature porous material from alkali-activated fly ash
Cengizler, H; Koç, M
The production of low-cost open-pore ceramic materials from fly ash (FA) and marble waste (MW) was investigated. The effect of MW (5-40 wt.%) on the open porosity was determined. To reduce the sintering temperature and improve the properties of porous materials, the mixtures were activated with an alkali solution. Samples pressed from FA and FA+MW mixtures were sintered at low temperature (900 degrees C), but sufficient strength could not be obtained. However, when these mixtures were subjected to alkali activation, pressed and sintered at 900 degrees C, sufficient strength and porosity values were reached. The open porosity of the MW neat specimen was 12.70%, but it increased up to 39.91% at 40 wt.% MW, which was the highest ratio used in the literature. The main phase structure was nepheline at 0-20 wt.% MW, but gehlenite became the dominant phase at 40 wt. % MW. The compressive and flexural strength values of 40 wt.% MW added specimen was determined to be 12 and 5.35 MPa, respectively. The openpore ceramic of high MW ratio, produced by this new alternative route, has the potential for use in water purification membranes for macro filtration purposes.
Effect of Carbonitriding on Corrosion Resistance of Steel 30MnB5 in Two Acidic Environments
Yazici, A; Zeybek, MS; Güler, H; Koç, M; Pekytkan, FG
Corrosion resistance of steel 30MnB5 is studied after carbonitriding, after conventional quenching, and without treatment. Corrosion tests are performed for from 24 to 168 h in two acidic environments (in a hydrochloric acid solution with 10% mole fraction and in fertilizer-containing soil). It is shown that the rate of corrosion of the steel in both environments after carbonitriding is lower than after quenching).
Production of ceramic glass foam of low thermal conductivity by a simple method entirely from fly ash
Cengizler, H; Koç, M; San, O
Ceramic glass foam/foams (CGF) from two different F-class fly ashes were produced via a well-known simple conventional sintering method using sodium silicate (Na2SiO3) as a foaming and fluxing agent. The research aimed to understand the effects of each fly ash, Na2SiO3 ratio, and sintering conditions on the properties and microstructure to produce a commercial CGF of low thermal conductivity. The chemical composition of fly ash from the thermal power plants of Tuncbilek and Seyitomer were quite similar but had different melting temperatures and microstructures. While the foam structure was successfully obtained at 1100 degrees C with 30 wt.% Na2SiO3 from Tuncbilek fly ash, a similar structure was obtained at 1150 degrees C from the Seyitomer fly ash. The effects of Na2SiO3 content and sintering temperature on the properties and microstructure of the CGF from the Tuncbilek fly ash of a lower melting point, in particular, were investigated systematically. The optimal sintering temperatures were determined to be 1200, 1150, and 1100 degrees C at the highest fly ash ratios of 90, 80 and 70 wt.%, respectively. The CGF were produced with 69.76-75.43% porosity, 0.55-0.69 gr/cm(3) bulk density, 3.2-5.35 MPa compressive strength and 0.10-0.21 W/(m K) of low thermal conductivity. XRD results showed that optimal CGF samples mainly contained spinel, quartz and hematite crystal phases and amorphous phase. In this research, a thermal insulation material was successfully produced using an industrial waste completely with a well-known simple method. It is thought that this will contribute beneficially to the environment and the economy.
Affordable and customizable electrospinning set-up based on 3D printed components
Skoumal, V; Pechousek, J; Parali, L; Koç, M
The widespread use of electrospinning, a technique widely used for fabricating micro/nanofibrous materials, has been limited by the high acquisition costs of commercial equipment. This study introduces an accessible alternative by leveraging 3D-printing technology, providing detailed insights into the design and functionality of each component. Specifically, a cost-effective syringe pump, a rotating collector that allows fiber orientation control, and a user-friendly control unit are described. The affordability and customizability of the proposed setup are emphasized, demonstrating its versatility in accelerating material research. Experimental results on polyvinyl difluoride (PVDF) showcase successful electrospinning, validating the efficacy of the 3D-printed electrospinning device. This innovative solution aims to increase the method's availability and broader utilization in research and development applications.
The piezoelectric response of electrospun PVDF/PZT incorporated with pristine graphene nanoplatelets for mechanical energy harvesting
Parali, L; Tatardar, F; Koç, M; Sari, A; Moradi, R
Flexible nanogenerators based on electrospun piezoelectric polyvinylidene fluoride (PVDF)/lead zirconium titanate (PZT) incorporated with unmodified graphene nanoplatelets (GNP) were fabricated via the electrospinning method. The microstructural and phase characterizations demonstrated a continuous and homogeneous fiber-shaped composite structure with good interfacial interaction between the GNP and the PVDF/PZT matrix. It was found that the diameter of the PVDF/PZT fibers was on average 270 nm, while the PVDF/PZT/GNP fiber with GNP content of 1.5wt.% had a diameter of approximately 236 nm. The piezoelectric performance evaluations of all nanogenerator devices indicated that the PVDF/PZT/GNP with GNP content of 1.5wt.% nanogenerator had an almost 6 times higher electrical output (8.68 mu W) compared to that of the PVDF/PZT-based nanogenerator (1.51 mu W) at 20 Hz within the same resistance of 2.5 M ohm. Considering its simple and low-cost fabrication technology, high performance, and stable electrical power efficiency, the introduced flexible nanogenerator based on the PVDF/PZT/GNP offers a promising capability of powering portable and wearable electronics.
Functional and physicochemical properties of whole egg powder: effect of spray drying conditions
Koç, M; Koç, B; Susyal, G; Yilmazer, MS; Ertekin, FK; Bagdatlioglu, N
Pasteurized liquid whole egg was subjected to spray drying to determine the effect of spray drying conditions on moisture content, water activity, peroxide value, emulsion stability, gel texture, foaming stability and colour change of the powder product. Drying process was carried out in a pilot scale spray dryer (Mobile Minor Niro-Atomizer, Denmark). The inlet (165-195 degrees C) and outlet air temperatures (60-80 degrees C) and the atomization pressure (196-392 kPa) were investigated as spray drying process variables. Perturbation and 3-D graphs revealed that outlet air temperature and atomization pressure had more effect than inlet air temperature, on the properties of whole egg powder. Optimum spray drying conditions of whole egg powder were determined according to the specific end-product requirements (bakery foods, omelette and mayonnaise and salad dressing) targeting to obtain the desired value of functional properties, i.e.; emulsion stability, gel texture, foaming stability and colour change.
Production of porous ceramic from clinoptilolite incorporating aluminum powder
San, O; Koç, M; Cengizler, H
In this study, production of porous ceramic from clinoptilolite incorporating aluminum powder at various sintering temperatures was investigated. The mixtures were sintered at 1150, 1200, 1250 and 1300 degrees C for 1 h in air atmosphere. SEM and XRD analyzes were conducted to observe the microstructural evolution and the phase composition, respectively. The DSC/TG analyzes of the clinoptilolite and aluminum powder mixture indicated that 1150 degrees C was a significant temperature at which oxidation of molten aluminum enhanced and the softening of the clinoptilolite began. The progress in oxidation of aluminum with increasing temperature led to corundum phase crystallization while the amount of cristobalite decreased. Aluminum distribution in the ceramic matrix began at 1200 degrees C but pore channels with very smooth surfaces were obtained at 1250 degrees C. At this temperature, the pores interconnected to each other had narrow pore size distribution (4-180 pm) with low friction coefficient of 0.64 resulting from enhanced corundum phase formation in the structure. Results showed that the porous ceramic sintered at 1250 degrees C with 32.8% apparent porosity and a pure water permeability of similar to 2050 L/ (m(2).hr.bar) promises great potential for use as a filtering media and/or support.
Fabrication and vibrational energy harvesting characterization of flexible piezoelectric nanogenerator (PEN) based on PVDF/PZT
Koç, M; Parali, L; San, O
In this study, polyvinylidene difluoride (PVDF) is doped with different volume levels (10, 20, 30 vol %) of lead zirconate titanate (PZT), and neat PVDF (undoped) electrospun nanofibres are prepared by aligning them through the electrospinning process with a rotating drum collector. All of the produced nanofibres are characterized by X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared spectroscopy (FTIR). The piezoelectric nanogenerator (PEN) devices are fabricated by placing the PVDF/PZT electrospun nanofibres as the dielectric material between two conductive plates. The vibrational energy harvesting analyses of the PEN are defined by taking measurements under various resistive loads. At 15 Hz excitation frequency, the maximum output power of PEN with PVDF+10 vol %PZT reaches 6.35 mu W by increasing the power to 85% under a resistive load of 1M Omega, while the PEN with beta-PVDF has the electrical power of 3.44 mu M at the same load. The PEN based energy generation is a promising source of clean energy generation from mechanical vibrations for powering portable microelectronic applications without an external power supply.
Optimal Use of Calcined Boron Waste as a Flux in the Production of Low-Temperature-Sintered Floor Tiles
Cengizler, H; Koç, M
Abstarct-This study focused on the recycling and optimal use of colemanite waste (CW) in floor tile/tiles (FT) production. Experimental compositions were prepared with various concentrations of CW calcined at 800 degrees C and FT body. The sinterability at low temperatures (1000-1100 degrees C) and the effect of calcined CW on FT properties were investigated. The physical-mechanical properties of the tiles were characterized by linear shrinkage, water absorption and bending strength tests. The microstructure and the phase development of the tiles were determined by SEM-EDX and XRD, respectively. The optimal tile compositions in conformity with the related standards were obtained at 1050 degrees C (30 wt % CW) and 1100 degrees C (5 and 10 wt % CW). The tiles produced with high ratio CW (30 wt %-1050 degrees C) additions had 0.32% water absorption, 5.70% linear shrinkage, and 52.43 MPa bending strength values. The CW calcined at 800 degrees C was favourably used in FT production to lower the sintering temperature with a new possibility to recycle this waste and conserve natural resources.
Effects of Formulation on Stability of Spray-Dried Egg
Koç, B; Koç, M; Güngör, Ö; Sakin-Yilmazer, M; Kaymak-Ertekin, F; Susyal, G; Bagdatlioglu, N
Moisture adsorption isotherms of spray-dried whole egg, microencapsulated with gelatin (G), lactose (L), pullulan (P), and their mixtures at equal ratios (gelatin+lactose [GL] and gelatin+pullulan [GP]), were determined using the standard static-gravimetric method at 25 degrees C. The data were fitted to the various sorption models and the constants were estimated by nonlinear regression analysis. Among the sorption models tested, the Guggenheim-Andersen-de Boer (GAB) and Ferro Fontan equations were recommended for characterizing the adsorption behavior of spray-dried whole egg, either microencapsulated or unencapsulated, in the water activity range of 0.11-0.84. It was indicated that all of the egg powders were stable up to a water activity of 0.43. The oxidative stability of microencapsulated powders was investigated under storage conditions of 20 degrees C and 50% relative humidity (RH). The microencapsulation process resulted in a decrease in the cholesterol oxidation level of egg powder during storage, where it followed a zero-order reaction kinetics and the trej value representing the time required to reach total cholesterol oxidation products (TCOP) 384.2 mu g/g egg fat as the upper limit of acceptability for fat oxidation was calculated as 1,124 days at 20 degrees C for egg powder microencapsulated with lactose. The relations among glass transition temperatures, oxidation rate constants, and monolayer moisture content values obtained by the GAB model are also highlighted.
Improving Functionality of Whole Egg Powder by the Addition of Gelatine, Lactose, and Pullulan
Koç, M; Koç, B; Susyal, G; Yilmazer, MS; Bagdatlioglu, N; Kaymak-Ertekin, F
The addition of gelatine (G), lactose (L), pullulan (P), and their mixtures at equal ratios (gelatine + lactose [GL] and gelatin + pullulan [GP]) to whole egg prior to drying was studied. Their effects on the functional properties (emulsion and gelling ability, water holding capacity of gel, foaming, color) and soluble protein content of spray dried egg powder during the 6 mo of storage at 20 degrees C and 50% relative humidity were investigated. It was demonstrated that the emulsion and foaming stability, water holding capacity of gel, and color change were significantly affected by the storage time, whereas storage time did not affect the strength of gel texture prepared by egg powders. Gelatine and pullulan improved the foaming stability and water holding capacity. Lactose caused a decrease in emulsion and foaming stability values. The maximum color change was observed for the plain egg powder, showing that mixing whole egg with carbohydrate- and/or protein-based additives before the drying process preserved the color of egg powder. Adding carbohydrate and/or protein caused significant changes in functional properties of egg powder.
The piezoelectric properties of three-phase electrospun PVDF/PZT/ Multiwalled Carbone Nanotube composites for energy harvesting applications
Koç, M; Tatardar, F; Musayeva, NN; Guluzade, S; Sari, A; Parali, L
In this study, the piezoelectric nanogenerators (PENs) based on the PVDF (polyvinylidene fluoride)/PZT (lead zirconate titanate, the particle size of <1 m) incorporated with MWCNT (Multiwalled Carbone Nanotube, Outer diameter: 10 nm, Inner diameter: 4.5 nm, and Length: 3-6 mu m) were produced using the electrospinning method. An 8- phase content of 96.56 % in PVDF electrospun composites was arrived at due to the synergistic effect of the PZT ceramics and the MWCNT nanoparticles. The experimental results showed that a PVDF/PZT/0.7 wt% MWCNT composite with a thickness of 145 mu m based on the PEN had an electrical power efficiency (0.16 mu W) approximately 1.3 times higher at a vibrational frequency of 20 Hz under a resistive load of 46 K Omega as compared to that of the PEN based on the PVDF/PZT composite (0.12 mu W). The PVDF/PZT/MWCNT-based PENs have promising potential for flexible energy transmission and structural health monitoring.
Spray drying encapsulation of essential oils; process efficiency, formulation strategies, and applications
Altay, Ö; Köprüalan, Ö; Ilter, I; Koç, M; Ertekin, FK; Jafari, SM
Essential oils (EOs) have many beneficial qualities, including antimicrobial, antioxidant, antiviral, and antifungal activities, along with good aroma, which have played a significant role in pharmaceutical, textile, and food industries. However, their high volatility and sensibility to external factors, as well as susceptibility to deterioration caused by environmental and storage conditions, or even common processing, and consequently limited water solubility, makes it difficult to incorporate them into aqueous food matrices and limits their industrial application. Spray-drying encapsulation has been proposed as a solution and a challenging research field to retard oil oxidation, extend EO's shelf life, improve their physicochemical stability, achieve controlled release, suggest novel uses, and therefore boost their added value. The objective of this review is to discuss various used wall materials, infeed emulsion properties, the main formulation and process variables affecting the physicochemical properties and release characteristics of the EOs-loaded particles obtained by spray-drying, the stability of EOs during storage, and the applications of encapsulated EOs powders in foods and nutrition, pharmaceuticals, and textile industries. The current review also summarizes recent advances in spray drying approaches for improving encapsulation efficiency, flavor retention, controlled release, and applicability of encapsulated EOs, thereby expanding their use and functionalities.
Bone marrow radiation dosimetry of high dose 131I treatment in differentiated thyroid carcinoma patients
Parlak, Y; Demir, M; Cavdar, I; Ereees, S; Gumuser, G; Uysal, B; Kaya, GC; Koç, M; Sayit, E
Background: Radiation absorbed dose to the red bone marrow, a critical organ in the therapy of thyroid carcinoma, is generally kept below 2 Gy for non-myeloablative therapies. The aim of this study was to calculate bone marrow radiation dose by using MIRDOSE3 package program and to optimize the safe limit of activity to be administered to the thyroid cancer patients. Materials and Methods: In this study, 83 thyroid cancer patients were divided into 3 groups based on the amount of activity administered into the body. In the groups, 3700 MBq, 5550 MBq and 7400 MBq activities were used respectively. The curves of time-activity were drawn from blood samples counts and effective half-life and residencetime were calculated. Correlations of bone marrow radiation dose and radioiodine effective half-life were determined as a function of administered activity via ANOVA test. Tg levels and tumour diameters were compared using Spearman's correlation. Results: The effective half-lives of I-131 for three groups of whole-body, receiving 3700 MBq, 5550 MBq and 7400 MBq were calculated as 20.57 +/- 5.4, 17.8 +/- 5.8 and 18.7 +/- 3.9 hours, respectively. The average bone marrow doses for 3 groups of patients were 0.32 +/- 0.08 Gy, 0.42 +/- 0.14 Gy and 0.60 +/- 0.24 Gy, respectively. Conclusion: It was concluded that, the bone marrow dose to the patients still remains within the recommended level even a 9 er administering an activity of 7400 MBq of I-131 to the patients.
PATTERNS OF CARE FOR LUNG CANCER IN RADIATION ONCOLOGY DEPARTMENTS OF TURKEY
Demiral, AN; Alicikus, ZA; Ugur, VI; Karadogan, I; Yöney, A; Andrieu, MN; Yalman, D; Pak, Y; Aksu, G; Özyigit, G; Özkan, L; Kilçiksiz, S; Koca, S; Çaloglu, M; Yavuz, AA; Çaglar, HB; Beyzadeoglu, M; Igdem, S; Serin, M; Kaplan, B; Koç, M; Korkmaz, E; Karakoyun-Çelik, Ö; Dinçer, S; Kinay, M
Purpose: To determine the patterns of care for lung cancer in Turkish radiation oncology centers. Methods and Materials: Questionnaire forms from 21 of 24 (87.5%) centers that responded were evaluated. Results: The most frequent histology was non-small cell lung cancer (NSCLC) (81%). The most common postoperative radiotherapy (RT) indications were close/(+) surgical margins (95%) and presence of pN2 disease (91%). The most common indications for postoperative chemotherapy (CHT) were >= IB disease (19%) and the presence of pN2 disease (19%). In Stage IIIA potentially resectable NSCLC, the most frequent treatment approach was neoadjuvant concomitant chemoradiotherapy (CHRT) (57%). In Stage IIIA unresectable and Stage IIIB disease, the most frequent approach was definitive concomitant CHRT (91%). In limited SCLC, the most common treatment approach was concomitant CHRT with cisplatin+etoposide for cycles 1-3, completion of CHT to cycles 4-6, and finally prophylactic cranial irradiation in patients with complete response (71%). Six cycles of cisplatin + etoposide CHT and palliative thoracic RT, when required, was the most commonly used treatment (81%) in extensive SCLC. Sixty-two percent of centers did not have endobronchial brachytherapy (EBB) facilities. Conclusion: There is great variation in diagnostic testing, treatment strategies, indications for postoperative RT and CHT, RT features, and EBB availability for LC cases. To establish standards, national guidelines should be prepared using a multidisciplinary approach. (c) 2008 Elsevier Inc.
Piezoelectric and magnetoelectric evaluations on PVDF/CoFe2O4 based flexible nanogenerators for energy harvesting applications
Koç, M; Dönmez, CED; Parali, L; Sari, A; Aktürk, S
In this study, flexible PVDF/CoFe2O4 based nanogenerators were fabricated using composite fibers which were prepared by combining polyvinylidene difluoride (PVDF) and cobalt ferrite (CoFe2O4) nanoparticles (NPs: similar to 16 nm diameter) at a concentration of 1, 3, 5, 7, and 10 wt%. All of the flexible PVDF/ CoFe2O4 nanofibers were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The incorporation of CoFe2O4 NPs into the PVDF leads to the formation a rich electroactive beta-phase in the composite structure. The piezoelectric properties of nanogenerators indicate that the nanogenerator based on the PVDF/CoFe2O4 fibers containing CoFe2O4 NPs at a concentration of 3 wt% has a greater power efficiency of 27.2% at 20 Hz compared to that of the nanogenerator with the pure PVDF fibers at 10 Hz, under the same resistive load of 2.5 M Omega. The results also show the magnetoelectric properties of the nanogenerator with PVDF + 10 wt% CoFe2O4 reached the highest voltage value of 18.87mV at the same load resistive load (2.5 M Omega) for a low-level magnetic field frequency of 50 Hz. The specially improved nanogenerators which have capability of producing electrical signals at the same time from mechanical and magnetic stimulations hold promise for the development of wearable electronics devices.
Piezoelectric and magnetoelectric properties of PVDF/NiFe2O4 based electrospun nanofibers for flexible piezoelectric nanogenerators
Parali, L; Donmez, CED; Koç, M; Aktürk, S
In this study, flexible piezoelectric nanogenerators (PNGs) were fabricated using the composite fibers which were prepared by combining polyvinylidene difluoride (PVDF) and nickel ferrite (NiFe2O4) nanoparticles (NPs) at a concentration of 1, 3, 5, 7, and 10 wt%. The piezoelectric properties of PNG indicate that the PVDF/NiFe2O4 fibers containing NiFe2O4 NPs at a concentration of 10 wt% has a higher power efficiency of 5.4% at 20 Hz compared to that of the pure PVDF fibers at 10 Hz, under the same resistive load of 2.5 M omega. The magnetoelectric properties of PNG show that the PNG with PVDF+7 wt%NiFe2O4 supplied the highest electrical power of 0.40 mu W under a resistive load of 750K omega & nbsp;while it reached a maximum voltage value of 17.50 mV at the same load resistive load for a low-level magnetic field of 50 Hz frequency.

Browsing by Author "Koç, M"

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