Hegzagonal WO3 nano parçacılarının PEG Destekli Hidrotermal Sentezi

Öz

Üstün yarı iletken özellikler gösteren tungsten oksit (WO₃) elektrokromik cihazlarda, gaz sensörlerinde ve fotokatalitik uygulamarda ile dikkat çekmektedir. Gelecekteki uygulamaları için kontrollü morfoloji ve kristal yapıya sahip parçacık, levha, tel, çubuk, tüp ve küre olmak üzere WO₃ nano yapısının hazırlanması önemlidir. Kristal yapısı ve boyutunun, spesifik gözenek alanı ve gözenek hacmi ve parçacık boyut dağılımı WO₃’ün kimyasal aktivitesi üzerine 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 WO₃ nano boyutlu parçacıklar substrat içeriğinin ağırlık oranı ve poli etilen glikol (MA:1500, PEG-1500) yüzey aktif kimyasalının eklenmesi ile kontrol edilen bir hidrotermal yöntem ile sentezlenmiştir. N₂ sorpsiyon, partikül morfolojisi ve kristal yapı özellikleri ile tanımlanan WO₃ örneklerinin karakteristiği; hacimsel yüzey analizi, taramalı elektron mikroskobu (SEM) ve X-ışını kırınımı (XRD) ile incelenmiştir. WO₃ örnekleri iyi kontrol edilen koşullar altında 200° 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 WO₃ nano partikülllerinin oluştuğu tespit edilmiştir. Bununla beraber son ürün WO₃ 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. 

Anahtar Kelimeler

• Tungsten oksit
• Hegzagonal
• Mezopor
• H2-TPR

PEG Assisted Hydrothermal Synthesis of Hexagonal WO3 Nanoparticles

Abstract

Tungsten oxide (WO3) displays superior semiconductor properties which renders it attractive for utilization in the electrochromic devices, gas sensors and photocatalytic applications. Preparation of WO3 nanostructures including particles, plates, wires, rods, tube and spheres with controlled morphology and crystal structure for the future application is gaining attention. It has been known that crystal structure and size, specific surface area, pore volume and particle size distribution of WO3 have a significant effect on chemical activity. As a result, it is necessary to investigate systematically the effects of preparing conditions in synthesis of well-controlled morphology and crystal structure. In the present study, hexagonal WO3 nano sized powders have been synthesized via hydrothermal method by controlling the weight ratio of substrate and additing of poly ethylene glycol (MW: 1500, PEG-1500) as surfactant agent. The characterization of WO3 samples is complemented with N2 sorption, particle morphology and crystalline properties are investigated by volumetric surface analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD). It has been shown that WO3 samples can 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 analyses results indicate that by addition of PEG-1500, hexagonal and mesoporous nanoparticles of WO3 are formed instead of rods. Moreover, most effective reduction temperatures of the final WO3 nano particles under hydrogen gas have been studied by using temperature programmed reduction (TPR). Characteristics of nano-sized metallic tungsten (W) obtained after the reduction process are investigated by XRD and SEM techniques. 

Keywords

• Tungsten oxide
• Hexagonal
• Mesoporous
• H2-TPR

Kaynakça

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