One-step hydrothermal synthesis and characterization of Mg/Mo co-doped VO2 nanorods (original) (raw)
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Nanocrystalline vanadium dioxide: synthesis and mid-infrared properties
2020
This work describes the ®rst successful synthesis of nanocrystalline thermochromic VO 2 powder using the low temperature irreversible structural transformation of the metastable VO 2 (B). At this step, the transformation is associated with a total rearrangement of VO 6 octahedra, and a strong increasing of density. The reversible metal±insulator phase transition (MIPT) of vanadium dioxide (T t 68°C) is associated with strong changes in electrical, magnetic and optical properties. The contrast of the optical transition in mid-infrared (MIR) region and the optical transparency are remarkably increased for these nanosized particles. Modi®cations in coloration are also observed. Ó
Journal of Physics and Chemistry of Solids, 2001
The reversible metal insulator phase transition of VO 2 (T c 688C) is associated with strong changes in electrical, magnetic and optical properties. Recently, nanopigments were synthesized using the low temperature irreversible structural transformation of the metastable VO 2 (B). Thin ®lms were deposited under radio-frequency sputtering conditions. The optical transparency is remarkably increased for these nanosized particles and thin ®lms. The VO 2 transition is characterized in the mid-infrared (MIR) region, using transmittance, re¯ectance and normal integrated emissivity measurements. Emissivity and re¯ectance are analyzed from two independent experimental techniques.
Synthesis and characterization of vanadium oxides nanorods
Vanadium oxides nanorods with high crystallinity and high surface area were synthesized by hydrothermal method using laurylamine hydrochloride, metal alkoxide and acetylacetone. The samples characterized by XRD, nitrogen adsorption isotherm, SEM, TEM, and SAED. Uniformly sized B phase VO 2 nanorods had widths about 40-80 nm and lengths reaching up to 1 mm. V 2 O 5 rodlike structured with the widths about 100-500 nm and the lengths of 1-10 mm were obtained by calcination at 400 1C for 4 h. This synthesis method provides a new simple route to fabricate one-dimensional nanostructured metal oxides under mild conditions. r 2005 Elsevier Inc. All rights reserved.
Journal of The Korean Chemical Society, 2019
Nb, Mo-doped and Nb/Mo-codoped VO2(M) nanocrystallites with various doping levels were synthesized for the first time by a hydrothermal and post thermal transformation method. The reversible phase transition characteristics of those doped VO2(M) was comparatively investigated. Nb-doping of VO2(M) by this method resulted in a very efficient lowering of the transition temperature (Tc) with a rate of -16.7 C/at.% that is comparable to W-doping, while Mo-doping did not give a serious reduction of Tc with only a rate of -5.1 C/at.%. Nb/Mo-codoping gave a similar result to Nb-doping without a noticeable difference. The thin films of Nb-doped and Nb/Mo-codoped VO2(M) with a thickness of ca. 120 nm were prepared by a wet-coating of the nanoparticle-dispersed solutions. Those films showed a good thermochromic modulation of near infrared radiation with 30-35% for Nb-doped VO2(M) and 37-40% for Nb/Mo-codoped ones. Nb/Mo-codoped VO2(M) film showed slightly enhanced thermochromic performance com...
Journal of the Korean Chemical Society, 2017
Monoclinic VO2(M) nanoparticles codoped with 1.5 at. % W and 2.9 at. % Mg were synthesized by the hydrothermal treatment and post-thermal transformation method of V2O5-H2C2O4-H2O with Na2WO4 and Mg(NO3)2. The composite thin film of the W/Mg-codoped VO2(M) with a commercial acrylic block copolymer was also prepared on PET substrate by wet-coating method. The reversible phase transition characteristics of the codoped VO2(M) nanoparticles and the composite film were investigated from DSC, resistivity and Vis-NIR transmittance measurements compared with the undoped and Wdoped VO2(M) samples. Mg-codoping into W-doped VO2(M) nanoparticles synergistically enhanced the transition characteristics by increasing the sharpness of transition while the transition temperature (Tc) lowered by W-doping was maintained. The codoped composite film showed the prominently enhanced NIR switching efficiency compared to only W-doped VO2(M) film with a lowered Tc.
A Novel Route for the Easy Production of Thermochromic VO 2 Nanoparticles
Chemistry – A European Journal, 2021
In this work, a simple, fast and dry method for the fabrication of a thermochromic product with a high load of VO 2 (M1) consisting of the controlled heat treatment of pure vanadium nanoparticles in air is presented. After a complete design of experiments, it is concluded that the most direct way to attain the maximum transformation of V into VO 2 (M1) consists of one cycle with a fast heating ramp of 42°C s À 1 , followed by keeping 700°C for 530-600 seconds, and a subsequent cooling at 0.05°C s À 1. Careful examination of these results lead to a second optimum, even more suitable for industrial production (quicker and less energy-intensive because of its lower temperatures and shorter times), consisting of subjecting V to two consecutive cycles of temperatures and times (625°C for 5 minutes) with similar preheating (42°C s À 1) but a much faster postcooling (8°C s À 1). These green reactions only use the power for heating a tube open to atmosphere and a vanadium precursor; without assistance of reactive gases or catalysts, and no special vacuum or pressure requirements. The best products present similar thermochromic properties but higher thermal stability than commercial VO 2 particles. These methods can be combined with VO 2 doping.
The Effect of Alkali Metal (Na, K) Doping on Thermochromic Properties of VO 2 Films
This work reports the synthesis of undoped and alkali metal doped thermochromic vanadium dioxide thin films by sol-gel spin coating and subsequent low-temperature annealing at 450 °C in N 2-H 2 atmosphere. The effect of sodium and potassium on the phase transition temperature as well as on the solar modulations were investigated. A dopant concentration of 0.3 at% resulted in a reduction of the critical transition temperature (T c) from 62 °C to 57 °C and 47 °C for the sodium and potassium doped films, respectively. Moreover, both dopants improved the solar modulations (ΔT sol) of the undoped VO 2 films from 3.81 to 9.44 and 5.43 %, respectively.