Hegzagonal WO3 nano parçacılarının PEG Destekli Hidrotermal Sentezi

Üstün yarı iletken özelliklere sahip olan tungsten oksit ($WO_3$) elektrokromik cihazlarda, gaz sensörlerinde ve fotokatalitik uygulamalarda ile dikkat çekmektedir. Gelecekteki kullanım alanları için kontrollü morfoloji ve kristal yapıya sahip parçacık, levha, tel, çubuk, tüp ve küre olmak üzere $WO_3$ nano yapısının hazırlanması önemlidir. Kristal yapısı ve boyutunun, spesifik gözenek alanı, gözenek hacmi ve parçacık boyut dağılımı $WO_3$’ün kimyasal aktivitesi üzerine önemli etkiye sahip olduğu bilinmektedir. Sonuç olarak, iyi kontrol edilmiş bir morfolojide ve kristal yapıda sentezlenebilmesi için üretim koşullarının etkilerinin sistematik olarak araştırılması gerekmektedir. Bu çalışmada, hegzagonal $WO_3$ nano boyutlu parçacıklar, substrat içeriğinin ağırlık oranı ve poli etilen glikol (MA:1500, PEG-1500) yüzey aktif kimyasalının eklenmesi ile kontrollü bir hidrotermal yöntem ile sentezlenmiştir. $N_2$ sorpsiyon, partikül morfolojisi ve kristal yapı özellikleri ile tanımlanan $WO_3$ örneklerinin karakteristiği; hacimsel yüzey analizi, taramalı elektron mikroskobu (SEM) ve X-ışını kırınımı (XRD) ile incelenmiştir. $WO_3$örnekleri iyi kontrol edilen koşullar altında 200 ${}^textdegree C$ ve 24 saat boyunca hidrotermal yöntem ile PEG-1500’ün ajan olarak eklenmesi veya eklenmemesi koşullarında üretildiği gösterilmiştir. Tungsten oksit nano yapılarının 63.02 nm kristal boyutu ile (002) ekseni boyunca büyüme gerçekleştiği belirlenmiştir. SEM analizi sonuçlarına göre çubuk yapısı yerine hegzagonal ve mezopor $WO_3$ nano partiküllerinin oluştuğu tespit edilmiştir. Bununla beraber son ürün $WO_3$ nano partiküllerini hidrojen gazı altındaki en etkili indirgenme sıcaklıkları sıcaklık programlı indirme (TPR) analizi ile incelenmiştir. İndirgenme sonrası elde edilen nano boyutlu metalik tungsten (W) özellikleri ise XRD ve SEM teknikleri ile araştırılmıştır.

PEG Assisted Hydrothermal Synthesis of Hexagonal $WO_3$ Nanoparticles

Tungsten oxide ($WO_3$) displays superior semiconductor properties which renders it attractive for utilization in the electrochromicdevices, gas sensors and photocatalytic applications. Preparation of $WO_3$ nanostructures including particles, plates, wires, rods, tubeand spheres with controlled morphology and crystal structure for the future application is gaining attention. It has been known thatcrystal structure and size, specific surface area, pore volume and particle size distribution of $WO_3$ have a significant effect on chemicalactivity. As a result, it is necessary to investigate systematically the effects of preparing conditions in synthesis of well-controlledmorphology and crystal structure. In the present study, hexagonal WO3 nano sized powders have been synthesized via hydrothermalmethod by controlling the weight ratio of substrate and addition of poly ethylene glycol (MW: 1500, PEG-1500) as surfactant agent.The characterization of $WO_3$ samples is complemented with $N_2$sorption, particle morphology and crystalline properties are investigatedby volumetric surface analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD). It has been shown that $WO_3$ samplescan be achieved by adding or not PEG-1500 as the agent in hydrothermal process at 200 °C for 24 h under well controlled conditions.The growth direction of the tungsten oxide nanostructures is determined along (002) axis with 63.02 nm crystal size. SEM analysesresults indicate that by addition of PEG-1500, hexagonal and mesoporous nanoparticles of $WO_3$ are formed instead of rods. Moreover,most effective reduction temperatures of the final $WO_3$ nano particles under hydrogen gas have been studied by using temperatureprogrammed reduction (TPR). Characteristics of nano-sized metallic tungsten (W) obtained after the reduction process are investigatedby XRD and SEM techniques.

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