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Effects of annealing parameters on phase, structure and thermochromic properties of VO2 (M) derived from nanostructured VO2(B)

Barra Hamdi Muhyuddin, Chen Soo Kien, Tamchek Nizam, Talib Zainal Abidin, Lee Oon Jew, Tan Kar Ban

Materials Science Poland

2020

Vol. 38, No. 4

661--666

Synthesis of thermochromic VO2 (M) was successfully done by annealing hydrothermally-prepared VO2 (B) at different temperatures and times. Conversion of the metastable VO2 (B) to the thermochromic VO2 polymorph was studied using thermogravimetric analyzer (TGA) under N2 atmosphere. Moreover, the phase and morphology of the synthesized samples were studied using X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM), respectively. Accordingly, the XRD scans of all the annealed samples exhibited the presence of monoclinic VO2 (M), while the FE-SEM images of the samples showed the formation of nanorods and nanospheres, particularly those heated at high temperatures (650 °C and 700 °C). Meanwhile, differential scanning calorimetry (DSC) was used to measure the phase transition temperature (tc), hysteresis, and enthalpy of the prepared VO2. Based on these results, all samples displayed a tc of about 66 °C. However, the hysteresis was high for the samples annealed at lower temperatures (550 °C and 600 °C), while the enthalpy was very low for samples heated at lower annealing time (1.5 h and 1 h). These findings showed that crystallinity and nanostructure formation affected the thermochromic properties of the samples. In particular, the sample annealed at 650 °C showed better crystallinity and improved thermochromic behavior.

Nanostructured flexible functional films for energy conversion and management CSIRO manufacturing flagship

Gutowski Wojciech S., Casey Phil S., Li Sheng, Yang Weidong

Journal of Machine Construction and Maintenance - Problemy Eksploatacji

2019

no. 1

31--38

Understanding and controlling the capture and conversion of energy and the flow of electrical charges within the bulk and/or across surfaces of materials and interfaces is a focus of significant scientific and technological pursuit. Our paper focuses on nanomaterials and hybrid systems targeting the management of IR, UV, and RF radiation by absorption or reflection mechanisms. It is assisted by engineering the structure of certain nanomaterials and by charge transfer along functional interphases imparting surface conductivity to the originally non-conductive materials such as flexible polymeric films. The latter constitute principal scaffolds for a variety of advanced technology applications such as: energy harvesting, conversion and storage, e.g., solar cells, lithium ion batteries, supercapacitors, or hydrogen storage.

Zrozumienie i kontrolowanie wychwytywania i konwersji energii oraz przepływu ładunków elektrycznych w masie i/lub w poprzek powierzchni materiałów i międzyfazy jest przedmiotem znaczących osiągnięć naukowych i technologicznych. Nasz artykuł koncentruje się na nanomateriałach i systemach hybrydowych ukierunkowanych na wykorzystanie promieniowania IR, UV i RF za pomocą mechanizmów absorpcji lub odbicia. Pomaga mu w tym inżynieria struktury niektórych nanomateriałów i przenoszenie ładunku wzdłuż funkcjonalnych miedzyfaz, które nadają przewodność powierzchni pierwotnie nieprzewodzącym materiałom, takim jak elastyczne folie polimerowe. Te ostatnie stanowią główne rusztowania dla szeregu zaawansowanych zastosowań technologicznych takich, jak: zbieranie, przekształcanie i przechowywanie energii, np. ogniwa słoneczne, akumulatory litowo-jonowe, superkondensatory lub akumulatory wodoru.

A facile synthesizing method of vanadium dioxide by pyrolyzing ammonium metavanadate

Qi J., Ning G., Hua R., Tian M., Liu S.

Materials Science Poland

2012

Vol. 30, No. 2

151--157

A facile process was developed for synthesizing vanadium dioxide (VO2) by pyrolyzing ammonium metavanadate (NH4VO3) in nitrogen flow. The process was designed on the base of thermodynamic modeling of chemical reaction and thermal analyzing of NH4VO3 pyrogenation in N2 gas, and optimized by experiments. X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were applied to characterizing the product VO2. Thermo-gravimetric analysis (TG) and DSC were used for analyzing the process of NH4VO3 pyrogenation. The experimental results indicated that VO2 microcrystal particles were successfully synthesized. The product VO2 presents two kinds of micro morphologies, torispherical and pentagonal prism. The phase transition mainly takes place at 338.4 K and 341.9 K. The average enthalpy of the phase transition is 28.82 J/g.