http://hdl.handle.net/11508/11914 2026-04-29T12:55:45Z http://hdl.handle.net/11508/20984 Sodyum asetat trihidratlı güneş enerjili ısıtma sisteminin performans analizi Güngör, Sercan Gülce; Kabul, Ahmet Bu çalışmanın amacı, güneş enerjili ısıtma sisteminde termal enerji depolama ile ısıtma ihtiyacının sürekli karşılanmasıdır. Fosil yakıtlara çevresel ve ekonomik açıdan alternatif olarak yenilenebilir enerji kaynaklarının kullanımı artmaktadır. Yenilenebilir enerji kaynakları çevresel ve ekonomik olarak avantajlı olmalarına rağmen enerji devamlılığı gibi bazı konularda sıkıntıları bulunmaktadır. Bu amaçla güneş enerjisi, düşük sıcaklıklarda faz değiştiren sodyum asetat trihidrat maddesi üzerine depolanmıştır. Deneyler Isparta ilinde faz değiştiren maddeli ve faz değiştiren maddesiz sistemler için ayrı ayrı yapılmıştır. Sonuç olarak FDM üzerine depolanan enerji miktarı ve bulunduğu ortama etki süresi incelenmiştir. Faz değiştiren madde kullanımı ile birlikte güneş enerjisinden yararlanma süresi ortalama % 20 artmıştır. 2015-12-25T00:00:00Z http://hdl.handle.net/11508/9882 Nanopowder synthesis of aluminum doped cadmium oxide via sol–gel calcination processing Aydın, Cihat; El- Nasser, H. M.; Yakuphanoğlu, Fahrettin; Yahia, I. S.; Aksoy, M. The structural, optical and electrical properties of undoped and Al-doped CdO powder nanostructures prepared by sol–gel calcinations method have been investigated. X-ray diffraction (XRD) results revealed that pure and Al-doped CdO have the polycrystalline with face centered cubic (FCC) structure. The crystallite size for undoped and 5, 10, 15, 20% of Al-doped CdO samples were found to be 17.2, 15.9, 16.1, 16.3 and 16.8 nm, respectively. The optical band gap of the samples were determined from the diffused reflectance spectra and Eg values for undoped and 5, 10, 15, 20% of Al-doped CdO samples were found to be 1.89, 2.07, 2.03, 2.07 and 2.12 eV, respectively. The electrical conductivities of pure and Al-doped CdO were measured in the temperature range (290–420 K) and their temperature dependence was analyzed according to Arrhenius relation. The electrical conductivity results indicate that the electrical conductivity mechanism is controlled by thermally activated processes. The results showed that sol–gel calcinations technique can be effectively used to produce undoped and doped nanopowders. 2011-01-01T00:00:00Z http://hdl.handle.net/11508/9881 Controlling of crystal size and optical band gap of CdO nanopowder semiconductors by low and high Fe contents Aydın, Cihat; Al- Hartomy, Omar A.; Al- Ghamdi, A. A.; Al- Hazmi, F.; Yahia, I. S.; El- Tantawy, F.; Yakuphanoğlu, Fahrettin The CdO:Fe nanopowder semiconductors were synthesized by the sol–gel calcination for the first time. The structural properties of Fe doped CdO samples were analyzed by AFM and XRD measurements. XRD patterns of the pure and Fe-doped CdO samples reveal that the pure and Fe doped CdO nanopowders are polycrystalline of cubic CdO structure. The crystallite size of undoped and Fe-doped CdO samples is changed unsystematically with a regular increase of Fe content. The optical band gaps of Fe doped CdO samples were determined for the first time by diffused reflectance measurements. The optical band gap of the samples is increased with the increase of Fe dopant inside the host matrix (CdO) up to 15 % followed by a decrease in its value. It is evaluated that Fe doped CdO nanopowder semiconductors can be producted by sol–gel calcination for advanced technological applications 2012-01-01T00:00:00Z http://hdl.handle.net/11508/9865 Synthesis, diffused reflectance and electrical properties of nanocrystalline Fe-doped ZnO via sol–gel calcination technique Aydın, Cihat; M. S. Abd. El- Sadek; Zheng, Kaibo; Yahia, I. S; Yakuphanoğlu, Fahrettin The nanocrystalline ZnO:Fe semiconductor oxides were successfully synthesized via the sol–gel calcination method. Structural, optical and electrical properties of the investigated samples were characterized by various techniques such as atomic force microscopy (AFM), UV–vis absorption and electrical transport measurements. The optical band gap for undoped ZnO (3.19 eV) decreases (2.75 eV) with increasing Fe-doped ZnO (20%). The temperature dependences of the electrical conductivities of undoped ZnO and Fe-doped ZnO were measured and analyzed by Arrhenius equation. The electrical conductivity of the samples decreases with the increase of Fe doping ratio; hence, the electrical conductivity mechanism is controlled by thermally activated processes. To support the nanostructure of Fe-doped ZnO, AFM micrographs were performed. 2012-12-18T00:00:00Z