Talks by Prof.Dr. İbrahim USLU
Dielectric Properties of Electrospun Nanofibers PVA, PVP and Their Mixtures
Polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) polymers are commonly used solvents for p... more Polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) polymers are commonly used solvents for producing nanofibers by Electrospinning method. Dielectric properties of PVP, PVA and their blends that are prepared by electrospinning were determined as a function of concentration in order to explore the possibility of using them as dielectric materials in different industrial applications. For this purpose, electrospun nanofibers are pressed into pellets with a hydraulic press. These samples of nanofibers were placed between two parallel Au electrode plates to read the admittance values of them. Measuremets were performed at 1 kHz - 13 MHz frequency range and at room temperature. The characterizations of nanofibers were carried out by a scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). It was discussed how to change the dielectric properties by mixing PVP.
The aim of the present work is to develop wound dressings which are innovative in terms of the wo... more The aim of the present work is to develop wound dressings which are innovative in terms of the wound healing rate and performance. The incorporation of drugs into the dressings make these dressings antimicrobial and help in control of infection around the wound. We have designed and developed wound dressing materials based on PVA/PAA, ciprofloxacin and aloe vera so that the wound undergoes proper healing where scar formation is the minimum. FT-IR analysis revealed that all characteristics and diameters of nanofibers was observed with SEM images.
The goal of this study is to produce wound dressing materials which prevent adherence of microorganism and provide quick wound healing. In terms of efficient use a wound dressing material it should have oxygen and humidity permeability by means of porous or fibrous structure and release drug for wide range area. It's possible to produce a material which has all of these properties by using nanotechnological methods. These type of materials can be produced via electro spinning technique. Poly(vinyl alcohol) (PVA) and Poly(acrylic acid) (PAA) have been frequently used in the preparation of various membranes due to their good biocompatibility and high swelling capability coupled with relatively good mechanical properties [1]. Ciprofloxacin is a broad spectrum antibiotic and has been used as component of wound dressings [2]. Aloe vera whose therapeutic effect is known for many years was added in order to provide quick wound healing. In this study ciprofloxacin and aloe vera was added one by one and together to observe differences between them. The fibrous wound dressing materials were prepared by the use of electro spinning technique. The electro spinning equipment uses a variable high voltage power supply from Gamma High Voltage Research (USA) [3]. The syringe needle was used as the electrode connected to the power source. The following operative parameters were chosen: a flow rate of 0.8 ml/h and an applied voltage of 15 kV [4]. Finally nanofibers were detached from Al foil collector and dried in the furnace at 80 °C overnight under vacuum [5]. Obtained nanofibers was characterized using SEM (Scanning Electron Microscopy) and FT-IR (Fourier transform infrared spectroscopy). SEM images show that, adding aloe vera makes nanofibers stronger and more linear than the others. FT-IR graphic show one another link up substances present of nanofibers and enable to investigate the structure of produced substance.
Release of ciprofloxacin was measured in ciprofloxacin and aloe vera doped nanofibers. In releasing experiment Pseudomonas aeruginosa and Staphylococcus aureus bacteria were used. Bacteria were inoculated to their suitable mediums. Then nanofibers were placed on medium with bacteria. Release ciprofloxacin from nanofiber prevent the bacterium growth and a clear zone occurs around nanofiber. Zone diameter around ciprofloxacin doped nanofibers is about 6 cm, zone diameter around ciprofloxacin and aloe vera doped nanofibers is about 5.5 cm. This shows that, when aloe vera added, ciprofloxacin slightly decrease it’s activity. According to adherence tests, electrospun nanofiber sample which contains aloe vera and ciprofloxacin has the least bacterial adherences. The highest bacterial adherence was observed at the sample which has no aloe vera and ciprofloxacin.
*Corresponding author: h_serincay@hotmail.com
[1] H. Bodugöz et al., O. Radiat. Phys. Chem. 55, 667, (1999).
[2] S. Çalangu, Klimik Dergisi 3, 115, 1990.
[3] I. Uslu and A. Aytimur, J. Appl. Polym. Sci. DOI: 10.1002/app.35525
[4] I.Uslu et al., Hacettepe J. Biol. Chem, 38, 19, (2009).
[5] I. Uslu et al., Hacettepe J. Biol. Chem, 36, 117, (2008).
Synthesis of Polymer Derived Boron-Doped Rare Earth Stabilized Bismuth Oxide Nanocomposites for S... more Synthesis of Polymer Derived Boron-Doped Rare Earth Stabilized Bismuth Oxide Nanocomposites for SOFC Applications
İbrahim USLU
Nanoscale composite materials in the form of nanopowders, nanowires, nanofibers and nanorods constitute a rapidly growing field, in terms of both scientific interest and potential technological applications [1-4]. Recently, polymer derived nanocomposites has become increasingly important in for numerous technological applications such as solid oxide fuel cells (SOFCs) [5].
Solid oxide fuel cells (SOFC) are based on the concept of oxygen ion conducting electrolyte through which the oxide ions (O2-) migrate from the air electrode (cathode) side to the fuel electrode (anode) side where they react with the fuel (H2, CH4, etc.) to generate an electrical voltage. [6] One major issue in the development of SOFC is the development of electrolyte materials with sufficiently high ionic conductivity at temperature below 800 °C. Lowering the operation temperatures would lessen the materials constraints and reduce the cost to fabricate the cell.
Bismuth oxide (Bi2O3) is an interesting transition metal oxide, with a large energy gap, dielectric permittivity [7,8] with low toxicity and low melting temperature (824 °C), has been identified to be the best ionic-conductive oxide at temperatures higher than 730 °C. Therefore, it is a potential electrolyte for solid oxide fuel cell (SOFC) [9]. However, bismuth oxide tends to be unstable and its conductive characteristics are not retained over longer periods of time, but cubic δ-Bi2O3 phase attracts particular attention. Unfortunately, the δ-Bi2O3 is only stable in a temperature range varying between 730–825 °C. When cooler, the δ-Bi2O3 phase transforms to metastable forms and the conductivity drops over three orders of magnitude [9,10]. When hotter, the δ-Bi2O3 phase can be retained at lower temperatures by doping Bi2O3 with the rare earth
The δ-Bi2O3 with 25% of oxygen vacancies also exhibits very high O2- ion conductivity with respect to other phases of Bi2O3 namely α, β and γ phases. A large number of studies has shown that the high conductivity δ-phase in Bi2O3 could be stabilized at lower temperatures, the addition of rare earth dopants (for example, Yb2O3, Er2O3, Dy2O3, Gd2O3) [11].
The addition of boron oxide to the composite materials as a dopant is very beneficial. It is an effective sintering aid because of its low melting point (460 °C), which could help during the sintering process. In this study, boric acid was chosen as the cheapest and nontoxic source of boric oxide [12-14].
The polymer precursor technique (PPT) has been proven to be one of the suitable techniques for the preparation of composite oxide which employs of complexing of metal acetate/nitrate precursor in a polymer solution for example PVA. Formation of low cost resultant polymeric product is calcined at a high temperature to remove the polymer and obtain homogeneous and unagglomerated crystalline ceramic powders. The main advantages of polymeric precursor techniques are the homogeneity of the precursors on a molecular level, the low processing temperatures. In this study, boron doped rare earth stabilized bismuth oxide nanocomposites were produced using PPT technique and PVA as a precursor polymeric material. Nanofibers were obtained using electrospinning technique, and then obtained nanofibers were turned into ceramic powders via calcination process. Nanofibers and ceramic powder samples were characterized by FT-IR, XRD and SEM techniques. Crystallite sizes of the samples were evaluated using Scherrer’s equation. Surface area and porosity of the powders was evaluated using BET technique.
Composite powders with nanograin size were obtained from this study. Nanograins have greater ratios of surface area to volume, which means a greater ratio of grain boundary to dislocations. The more grain boundaries that exist, the higher the strength becomes. Thus, an easy way to improve the strength of a material is to make the grains as small as possible, increasing the amount of grain boundary
References
1] A. Gholami, H. Tavanai, A.R. Moradi: J. Nanopart. Res. 13 (2011) 2089.
[2] D. Parlevliet, P. Jennings: J. Nanopart. Res. 13 (2011) 4431.
[3] K.M. Sawicka, P. Gouma: J. Nanopart. Res. 8 (2006) 769.
[4] C.W. Blackledge, T. Tabarin, E. Masson, R.J. Forster, T.E. Keyes: J. Nanopart. Res. 13 (2011) 4659.
[5] D.J. Guo, S.K. Cui, H. Sun: J. Nanopart. Res. 11 (2009) 707.
[6] S.C. Singhal: Solid State Ionics 135 (2000) 305.
[7] L. Leontie, G.I. Rusu: J. Non-Cryst. Solids 352 (2006) 1475.
[8] D.F. Peng, H.Q. Sun, X.S. Wang, J.C. Zhang, M.M. Tang, X. Yao: J. Alloy. Compd. 511 (2012) 159.
[9] C.H. Weng, W.C.J. Wei: J. Am. Ceram. Soc. 93 (2010) 3124.
[10] A.M. Azad, S. Larose, S.A. Akbar: J. Mater. Sci. 29 (1994) 4135.
[11] M. Bosacka: Mater. Res. Bull. 41 (2006) 2181.
[12] M. Takeyama, C.T. Liu: Acta. Metall. Sin. 36 (1988) 1241.
[13] Z.W. Zhang, C.T. Liu, S. Guo, J.L. Cheng, G. Chen, T. Fujita, M.W. Chen, Y.W. Chung, S. Vaynman, M.E. Fine, B.A. Chin: Mat. Sci. Eng. A-Struct. 528 (2011) 855.
[14] J.M. Ting: J. Am. Ceram. Soc. 77 (1994) 2751.
Sodium cobalt oxide (Na1Co2O4) crystalline thermoelectric materials were obtained using polyvinyl... more Sodium cobalt oxide (Na1Co2O4) crystalline thermoelectric materials were obtained using polyvinyl alcohol (PVA) polymerized complex sol-gel solution. PVA was used as polymer solution with sodium acetate/cobalt acetate. The sodium cobalt oxide calcined crystal structures were characterized by X-ray diffraction (XRD), scaning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The sol-gel solution calcined at 800 oC and then calcined powder was pellet 12,5 t under pressure and sintered at the 850 oC. This pellets thermoelectric properties measured by Lot-Oriel PPMS.
Electrospinning process was utilized to fabricate lantanium doped bismuth ultrafine nanofibers. P... more Electrospinning process was utilized to fabricate lantanium doped bismuth ultrafine nanofibers. PVA was used as polymer solution with bismuth acetate/lantanium acetate, followed by calcination at 800 oC. The produced nanofibers and calcined crystal structures were characterized by using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that samples after calcination should be sintered more than one to obtain pure crystalline phase.
For the first time, sodium cobalt oxide (NaxCo2O4) crystalline thermoelectric materials were obta... more For the first time, sodium cobalt oxide (NaxCo2O4) crystalline thermoelectric materials were obtained using polyvinyl alcohol (PVA) polymerized complex sol-gel solution. PVA was used as polymer solution with sodium acetate/cobalt acetate, followed by calcination at 800 oC. The sodium cobalt oxide calcined crystal structures were characterized by X-ray diffraction (XRD). The sol-gel solution calcined at 800 oC and then sintered at the same temperature was single crystal and XRD results have an agreement with the literature values. The results indicated that the polymeric sol-gel method is a promising process for the synthesis of sodium cobalt oxide thermoelectric materials.
Bilgisayarların eğitim sürecine katkılarının incelenmesi sonucu daha verimli eğitim süreçlerinin ... more Bilgisayarların eğitim sürecine katkılarının incelenmesi sonucu daha verimli eğitim süreçlerinin oluşturulabileği düşünülmektedir.
Türkiye petrolde %40, doğalgazda %64 oranında Rusya’ya bağımlı olup buna diğer ülkeler ve enrji k... more Türkiye petrolde %40, doğalgazda %64 oranında Rusya’ya bağımlı olup buna diğer ülkeler ve enrji kaynakları dahil değildir. Bu nedenle ülkemizde nükleer enerji alternatif bir enerji kaynağı olarak devreye girmelidir. Ancak kurulacak reaktörün güvenli işletilmesi gereklidir. Tesisin güvenli işletilmesinde siyasi otoriteden bağımsız Nükleer Düzenleme ve Denetleme Kurumu (NDDK) kurulması son derece önemli ve Uluslar arası Atom Enerjisi Ajansı’nın (IAEA) güvenlik kriterlerine göre de gereklidir. Tesisin kullanacağı nükleer yakıt konusunda dışa bağımlılığı ortadan kaldıracak her türlü çalışma ve ARGE çalışmaları başta üniversitelerimiz olmak üzere başlatılmalı ve teşvik edilmelidir. Kullanılmış nükleer yakıtların derin bir şekilde depolanması ya da işletilmesi konusu da şimdiden ele alınması gerektiren konuların başında gelmektedir.
Nikel ve çinko oksit ince film seramik kompozitler elektronik ve kimya endüstrisinde yaygın olara... more Nikel ve çinko oksit ince film seramik kompozitler elektronik ve kimya endüstrisinde yaygın olarak kullanılmaktadır[1-5]. Nikel ve çinko oksit yapıların birlikte kullanıldığı da görülmektedir. Son yıllarda bu oksitler gaz duyarlı, yarı iletken ve yumusak ferrit malzemelerin eldesinde de kullanıldıgı görülmektedir [4-7]. Literatürde bu mallezemelerin birlikte üretiminde fiziksel ve kimyasal buhar çöktürme yöntemleri ,sol-gel yöntemi ve son yıllarda da elektrospinleme kullanıldıgı da görülmektedir[3].
Bu çalışmada nikel ve çinko asetat çözeltileri sulu ortamda çözdürülerek elektrospinleme ile nanofiber elde etmek için tasıyıcı olarak kullanılan polivinil alkol ile birlikta çözdürülmustur. Yukardaki çözeltilere degişik miktarlarda bor katkılayarak borun yarı iletken malzemelerin iletkenliğine, akışkanlığına , yapısına , termal dayanıklılığına etkisi viskosimetre ve kondaktometre, FTIR, SEM, DSC cihazları ile incelenmiştir.
Asetat çözeltilerinin akışkanlık ve iletkenlik parametrelerinde parallelik gözlenmiş olup bor katkısının çözeltinin akıskanlıgını arttırdığı iletkenliği ise azalttıgı gözlenmiştir. Dsc analizinde bor katkısının erime noktası yukselmesine ve maddelerin daha yüksek sıcaklıklarda parcalanmasına neden olmustur. Aynı zamanda FTIR ve SEM analizleri ile de maddenin karakterizasyonu
Literatürde ilk defa yapılan bu çalısmayla daha üstün özellikli Ni-Zn yarıiletken malzemelerin eldesi gerçeklestirilmiştir.
For the first time, nanofibers of PVA/Calix[4]arene nanofibers were prepared by using sol–gel pro... more For the first time, nanofibers of PVA/Calix[4]arene nanofibers were prepared by using sol–gel processing and electrospinning technique. In this study, we have prepared calixarene based nano fibers by using several p-sulfonated calixarenes via electro-spinning and examined their structures with some characterization methods such as FTIR, SEM.
This study is related to the preparation of boron supported YBa2Cu3O7 (YBCO) superconducting mate... more This study is related to the preparation of boron supported YBa2Cu3O7 (YBCO) superconducting material. The first step was the preparation of composite by mixing yttrium, barium and copper acetates with polyvinyl alcohol (PVA) at a suitable temperature. The resulting composite polymer was then electrospun giving nano fibers and finally the resulting nano fibers were subjected to a thermal treatment to obtain superconducting material. The conductivity of the nano fibers obtained was measured with four probe technique. Scanning Electron Microscopy (SEM) were used for the characterization of the nanofibers.
"Bu çalışmada bor katkılı YBa2Cu3O7 (YBCO) malzemesi elde edilmiştir. YBCO elde etmek için önce s... more "Bu çalışmada bor katkılı YBa2Cu3O7 (YBCO) malzemesi elde edilmiştir. YBCO elde etmek için önce sol-jel yöntemiyle itriyum, baryum ve bakır asetat sulu çözeltisini, polivinyl alkol (PVA) ile uygun sıcaklıklarda karıştırılarak hazırlanan kompozit polimerin elektrospinlenerek nanofiber yapılar elde edilmiş, nanofiberlerin ısıl işlemden geçirerek süperiletken malzemeler elde etmişlerdir.
Çalışmada elde edilen nanofiberlerin iletkenliği dört nokta probu ile ölçülmüş ve bor katkılı polimerin daha fazla iletkenliğe sahip olduğu saptanmıştır. Nanofiberlerin Diferansiyel Tarama Kalorimetresi (DSC) analizinde bor katkısın fiberlerin ısıya karşı dayanıklılığını artırdığı görülmüştür.
Taramalı elektron mikroskobu (SEM) görüntülerinden bor katkılı nanofiberlerin çok düzgün şekilde elektrospinlendiği ve fiberlerin üzerinde diğerinde olduğu gibi herhangi bir topaklanma yada boncuklanma olmadığı görülmüştür."
In this study the precursor solutions were prepared by dissolving various amounts (4, 8 and 12g) ... more In this study the precursor solutions were prepared by dissolving various amounts (4, 8 and 12g) of Zn acetate in distilled water. 15g PVA powder dissolved in water to obtain %10 wt solution and 40ml of this aqueous PVA solution was added slowly dropwise into the zinc acetate solution and it was stirred for 3h. Then they were kept in a constant temperature bath at 50 0C for 6h for the reaction occurs between PVA and Zn acetate solution. This precursor solution was taken into a syringe and spinned under 10-20kV with a distence of about 13 cm.
Bu çalışmada Konya'da Agaricus Bisporus üretimi yapanlardan üreticilerden temin edilen örnekler ü... more Bu çalışmada Konya'da Agaricus Bisporus üretimi yapanlardan üreticilerden temin edilen örnekler üzerinde ağır metal analizi yapılmıştır.
In recent years, the number of incidents with orphan sources has been constantly increasing, with... more In recent years, the number of incidents with orphan sources has been constantly increasing, with sources being found not only at customs border controls but also frequently in scrap and in other unexpected locations, thereby giving rise to growing social concern in view of the risks involved. The paper summarizes all phases in the management of orphan sources from detection to storage.
The legal infrastructure in Turkey for the management of low-level radioactive waste covers the l... more The legal infrastructure in Turkey for the management of low-level radioactive waste covers the liquid, solid and gaseous wastes. Management of these radioactive wastes is briefly described in this paper. Moreover, delay and decay tank systems that are used to collect and store the low level radioactive wastes as a part of low-level radioactive effluent discharge policy are introduced.
A State should have a plan ready for response to the detection or suspicion of illicit traffickin... more A State should have a plan ready for response to the detection or suspicion of illicit trafficking in or loss of control of radioactive sources. The response to a radiological emergency may involve many organizations. Therefore, in order to be effective, the response to a radiological emergency must be well co-ordinated, and arrangements must be appropriately integrated with those for a conventional emergency. The regulatory body should require that the emergency arrangements be tested in an exercise before the commencement of operations.
The legal infrastructure established in Turkey covers the ways to manage low-level radiaoactive w... more The legal infrastructure established in Turkey covers the ways to manage low-level radiaoactive wastes including liquid, solid and gaseous wastes. The paper gives detailed information about the discharge policies and radioactive waste tank systems, and dose assessment. Liquid radioavtive waste tank systems, as best available technique, are used to collect and store the low level radioactive wastes and as a part of low level radioactive wastes
effluent dischared policy, this decay and delay systems are effectively used for biomedical radioactive wastes generated in hospitals. The decayed waste is then discharged to sewage system in accordance with the discharge limit given in the legislation. Dose assessment studies were also completed and the annual effective dose that would be received by the workers of the waste treatment facility was calculated and the results are presented
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Talks by Prof.Dr. İbrahim USLU
The goal of this study is to produce wound dressing materials which prevent adherence of microorganism and provide quick wound healing. In terms of efficient use a wound dressing material it should have oxygen and humidity permeability by means of porous or fibrous structure and release drug for wide range area. It's possible to produce a material which has all of these properties by using nanotechnological methods. These type of materials can be produced via electro spinning technique. Poly(vinyl alcohol) (PVA) and Poly(acrylic acid) (PAA) have been frequently used in the preparation of various membranes due to their good biocompatibility and high swelling capability coupled with relatively good mechanical properties [1]. Ciprofloxacin is a broad spectrum antibiotic and has been used as component of wound dressings [2]. Aloe vera whose therapeutic effect is known for many years was added in order to provide quick wound healing. In this study ciprofloxacin and aloe vera was added one by one and together to observe differences between them. The fibrous wound dressing materials were prepared by the use of electro spinning technique. The electro spinning equipment uses a variable high voltage power supply from Gamma High Voltage Research (USA) [3]. The syringe needle was used as the electrode connected to the power source. The following operative parameters were chosen: a flow rate of 0.8 ml/h and an applied voltage of 15 kV [4]. Finally nanofibers were detached from Al foil collector and dried in the furnace at 80 °C overnight under vacuum [5]. Obtained nanofibers was characterized using SEM (Scanning Electron Microscopy) and FT-IR (Fourier transform infrared spectroscopy). SEM images show that, adding aloe vera makes nanofibers stronger and more linear than the others. FT-IR graphic show one another link up substances present of nanofibers and enable to investigate the structure of produced substance.
Release of ciprofloxacin was measured in ciprofloxacin and aloe vera doped nanofibers. In releasing experiment Pseudomonas aeruginosa and Staphylococcus aureus bacteria were used. Bacteria were inoculated to their suitable mediums. Then nanofibers were placed on medium with bacteria. Release ciprofloxacin from nanofiber prevent the bacterium growth and a clear zone occurs around nanofiber. Zone diameter around ciprofloxacin doped nanofibers is about 6 cm, zone diameter around ciprofloxacin and aloe vera doped nanofibers is about 5.5 cm. This shows that, when aloe vera added, ciprofloxacin slightly decrease it’s activity. According to adherence tests, electrospun nanofiber sample which contains aloe vera and ciprofloxacin has the least bacterial adherences. The highest bacterial adherence was observed at the sample which has no aloe vera and ciprofloxacin.
*Corresponding author: h_serincay@hotmail.com
[1] H. Bodugöz et al., O. Radiat. Phys. Chem. 55, 667, (1999).
[2] S. Çalangu, Klimik Dergisi 3, 115, 1990.
[3] I. Uslu and A. Aytimur, J. Appl. Polym. Sci. DOI: 10.1002/app.35525
[4] I.Uslu et al., Hacettepe J. Biol. Chem, 38, 19, (2009).
[5] I. Uslu et al., Hacettepe J. Biol. Chem, 36, 117, (2008).
İbrahim USLU
Nanoscale composite materials in the form of nanopowders, nanowires, nanofibers and nanorods constitute a rapidly growing field, in terms of both scientific interest and potential technological applications [1-4]. Recently, polymer derived nanocomposites has become increasingly important in for numerous technological applications such as solid oxide fuel cells (SOFCs) [5].
Solid oxide fuel cells (SOFC) are based on the concept of oxygen ion conducting electrolyte through which the oxide ions (O2-) migrate from the air electrode (cathode) side to the fuel electrode (anode) side where they react with the fuel (H2, CH4, etc.) to generate an electrical voltage. [6] One major issue in the development of SOFC is the development of electrolyte materials with sufficiently high ionic conductivity at temperature below 800 °C. Lowering the operation temperatures would lessen the materials constraints and reduce the cost to fabricate the cell.
Bismuth oxide (Bi2O3) is an interesting transition metal oxide, with a large energy gap, dielectric permittivity [7,8] with low toxicity and low melting temperature (824 °C), has been identified to be the best ionic-conductive oxide at temperatures higher than 730 °C. Therefore, it is a potential electrolyte for solid oxide fuel cell (SOFC) [9]. However, bismuth oxide tends to be unstable and its conductive characteristics are not retained over longer periods of time, but cubic δ-Bi2O3 phase attracts particular attention. Unfortunately, the δ-Bi2O3 is only stable in a temperature range varying between 730–825 °C. When cooler, the δ-Bi2O3 phase transforms to metastable forms and the conductivity drops over three orders of magnitude [9,10]. When hotter, the δ-Bi2O3 phase can be retained at lower temperatures by doping Bi2O3 with the rare earth
The δ-Bi2O3 with 25% of oxygen vacancies also exhibits very high O2- ion conductivity with respect to other phases of Bi2O3 namely α, β and γ phases. A large number of studies has shown that the high conductivity δ-phase in Bi2O3 could be stabilized at lower temperatures, the addition of rare earth dopants (for example, Yb2O3, Er2O3, Dy2O3, Gd2O3) [11].
The addition of boron oxide to the composite materials as a dopant is very beneficial. It is an effective sintering aid because of its low melting point (460 °C), which could help during the sintering process. In this study, boric acid was chosen as the cheapest and nontoxic source of boric oxide [12-14].
The polymer precursor technique (PPT) has been proven to be one of the suitable techniques for the preparation of composite oxide which employs of complexing of metal acetate/nitrate precursor in a polymer solution for example PVA. Formation of low cost resultant polymeric product is calcined at a high temperature to remove the polymer and obtain homogeneous and unagglomerated crystalline ceramic powders. The main advantages of polymeric precursor techniques are the homogeneity of the precursors on a molecular level, the low processing temperatures. In this study, boron doped rare earth stabilized bismuth oxide nanocomposites were produced using PPT technique and PVA as a precursor polymeric material. Nanofibers were obtained using electrospinning technique, and then obtained nanofibers were turned into ceramic powders via calcination process. Nanofibers and ceramic powder samples were characterized by FT-IR, XRD and SEM techniques. Crystallite sizes of the samples were evaluated using Scherrer’s equation. Surface area and porosity of the powders was evaluated using BET technique.
Composite powders with nanograin size were obtained from this study. Nanograins have greater ratios of surface area to volume, which means a greater ratio of grain boundary to dislocations. The more grain boundaries that exist, the higher the strength becomes. Thus, an easy way to improve the strength of a material is to make the grains as small as possible, increasing the amount of grain boundary
References
1] A. Gholami, H. Tavanai, A.R. Moradi: J. Nanopart. Res. 13 (2011) 2089.
[2] D. Parlevliet, P. Jennings: J. Nanopart. Res. 13 (2011) 4431.
[3] K.M. Sawicka, P. Gouma: J. Nanopart. Res. 8 (2006) 769.
[4] C.W. Blackledge, T. Tabarin, E. Masson, R.J. Forster, T.E. Keyes: J. Nanopart. Res. 13 (2011) 4659.
[5] D.J. Guo, S.K. Cui, H. Sun: J. Nanopart. Res. 11 (2009) 707.
[6] S.C. Singhal: Solid State Ionics 135 (2000) 305.
[7] L. Leontie, G.I. Rusu: J. Non-Cryst. Solids 352 (2006) 1475.
[8] D.F. Peng, H.Q. Sun, X.S. Wang, J.C. Zhang, M.M. Tang, X. Yao: J. Alloy. Compd. 511 (2012) 159.
[9] C.H. Weng, W.C.J. Wei: J. Am. Ceram. Soc. 93 (2010) 3124.
[10] A.M. Azad, S. Larose, S.A. Akbar: J. Mater. Sci. 29 (1994) 4135.
[11] M. Bosacka: Mater. Res. Bull. 41 (2006) 2181.
[12] M. Takeyama, C.T. Liu: Acta. Metall. Sin. 36 (1988) 1241.
[13] Z.W. Zhang, C.T. Liu, S. Guo, J.L. Cheng, G. Chen, T. Fujita, M.W. Chen, Y.W. Chung, S. Vaynman, M.E. Fine, B.A. Chin: Mat. Sci. Eng. A-Struct. 528 (2011) 855.
[14] J.M. Ting: J. Am. Ceram. Soc. 77 (1994) 2751.
Bu çalışmada nikel ve çinko asetat çözeltileri sulu ortamda çözdürülerek elektrospinleme ile nanofiber elde etmek için tasıyıcı olarak kullanılan polivinil alkol ile birlikta çözdürülmustur. Yukardaki çözeltilere degişik miktarlarda bor katkılayarak borun yarı iletken malzemelerin iletkenliğine, akışkanlığına , yapısına , termal dayanıklılığına etkisi viskosimetre ve kondaktometre, FTIR, SEM, DSC cihazları ile incelenmiştir.
Asetat çözeltilerinin akışkanlık ve iletkenlik parametrelerinde parallelik gözlenmiş olup bor katkısının çözeltinin akıskanlıgını arttırdığı iletkenliği ise azalttıgı gözlenmiştir. Dsc analizinde bor katkısının erime noktası yukselmesine ve maddelerin daha yüksek sıcaklıklarda parcalanmasına neden olmustur. Aynı zamanda FTIR ve SEM analizleri ile de maddenin karakterizasyonu
Literatürde ilk defa yapılan bu çalısmayla daha üstün özellikli Ni-Zn yarıiletken malzemelerin eldesi gerçeklestirilmiştir.
Çalışmada elde edilen nanofiberlerin iletkenliği dört nokta probu ile ölçülmüş ve bor katkılı polimerin daha fazla iletkenliğe sahip olduğu saptanmıştır. Nanofiberlerin Diferansiyel Tarama Kalorimetresi (DSC) analizinde bor katkısın fiberlerin ısıya karşı dayanıklılığını artırdığı görülmüştür.
Taramalı elektron mikroskobu (SEM) görüntülerinden bor katkılı nanofiberlerin çok düzgün şekilde elektrospinlendiği ve fiberlerin üzerinde diğerinde olduğu gibi herhangi bir topaklanma yada boncuklanma olmadığı görülmüştür."
effluent dischared policy, this decay and delay systems are effectively used for biomedical radioactive wastes generated in hospitals. The decayed waste is then discharged to sewage system in accordance with the discharge limit given in the legislation. Dose assessment studies were also completed and the annual effective dose that would be received by the workers of the waste treatment facility was calculated and the results are presented