Search

High-performance vanadium dioxide (VO2) thin films with high luminous transmittance and solar modulation ability were successfully fabricated on ZrxOy/glass substrate by pulsed laser deposition. By controlling the growth temperature of the buffer layer, the stoichiometry and crystal structure of ZrxOy buffer layer can be converted from cubic Zr2O phase to monoclinic ZrO2 phase. Through such a transformation, the luminous transmittance (Tlum), solar modulation ability (ΔTsol), the transition temperature and the width of thermal hysteresis loop have been tuned without diminishing the thermochromic property. It is found that the insertion of ZrO2 layer results in a remarkable enhancement of the luminous transmittance and the solar modulation ability when compared to single-layer VO2 film. The findings in the present work may provide some new strategies for the commercialization of VO2 films in the field of smart energy-efficient windows.

Vanadium dioxide (VO2) with reversible metal–insulator transition (MIT) is a promising energy-saving material for next-generation smart windows and infrared devices. However, the specific applications are largely limited by controllable preparation with different polymorphs on common glass substrates. Herein, VO2 thin films were prepared on transparent amorphous glass substrates by inserting TiO2 buffer layers using pulsed laser deposition (PLD) technique. The results showed that B-VO2 film would be formed on the amorphous glass substrate at 400 °C. While after inserting TiO2 buffer layer, pure M-VO2 films with clear phase transition properties were obtained. Based on the analysis of X-ray Diffraction (XRD) and Energy Dispersive Spectrometer (EDS) characterization, the crystalline transformation was attributed to the template effect of TiO2 layer and Ti ions diffusion. The characteristics of VO2/TiO2/glass thin films were closely associated with the thickness of TiO2 buffer layer. With 60 nm TiO2 buffer layer, the VO2/TiO2/glass film showed the sharpest resistance change with more than 2.5-order of magnitude across the MIT, and the T-vis value is as high as 53% with the ΔTsol up to 5.2%. Our current results demonstrated the importance of TiO2 buffer layer to the formation of M-VO2 film on amorphous glass substrate, which was very meaningful for the production of energy efficient smart windows in the future.

Zr50Cu50, Zr47Cu44Al9, Zr46.3Cu43.4Al8.3Nb2 and Zr41.2Ti13.8Cu17.5Ni5Be22.5 thin film metallic glasses (TFMGs) were prepared by pulsed laser deposition (PLD) on glass substrates at room temperature. The effect of thickness on the electrical and optical properties of the Zr-based TFMGs was investigated. It was found that the resistivity of the Zr-based TFMGs basically decreased as the thickness varied from 10 nm to 40 nm. Interestingly, while the transmittance in the visible region decreased significantly with the increase of thickness, the transmittance in the near-infrared range still remained at a high level of larger than 80%. Through the characterization of electrical properties, the high transmittance of the Zr-based TFMGs in the near-infrared range was attributed to their rather low carrier concentration. Our findings provided the possibility for TFMGs to be used as transparent electrodes in the field of near infrared sensors and solar cells. Keywords: Thin film metallic glass, Zr-based alloys, Transmittance, Near infrared

Vanadium dioxide (VO2) thin films with pure Monoclinic phase could be transformed from B-phase by inserting TiO2 buffer layers on transparent amorphous glass substrates at the low temperature of 400 °C. This crystalline transformation might be ascribed to oxygen-deficient environment induced by the TiO2 buffer layer and the template effect of TiO2 layer for M-VO2 phase. The simplicity in phase regulation of the present method and the superior optical and electrical properties of the films may allow its wide applications in thermo-opto-electro sensing devices. Keywords: Vanadium dioxide, TiO2 buffer layers, Photoelectric properties

We reported here the studies of a series of Zr20Ti20Hf20M20Be20 (M = Cu, Ni and Co) quinary high entropy bulk metallic glasses. Glasses with critical diameters (Dc) of 3 mm, 8 mm and 5 mm, respectively has been successfully fabricated by copper mold casting. Strikingly, a plastic strain of 11.6% is achieved in the Zr20Ti20Hf20Cu20Be20 metallic glass. The dynamic fragility the Zr20Ti20Hf20Cu20Be20 alloy is determined from calorimetric measurements. The excellent plasticity is explained to be attributed to relatively higher fragility. Keywords: High entropy alloys, Bulk metallic glasses, Glass forming ability, Mechanical property and fragility

In this work, the conventional combustion in O2/Ar and O2/CO2 atmospheres at temperatures of 700–1000 °C and isotopic tracing experiments at 700–800 °C were conducted respectively in a micro fluidized bed reactor to clarify the conversion characteristics of lignite char and influence mechanism of elevated CO2 concentrations. The isotopic method employing C18O18O provides an intuitive insight into the CO2 gasification behavior by tracking the evolution of the 18O atom throughout the oxy-fuel combustion. The results reveal that char conversion rate significantly reduces when the atmosphere is switched from O2/Ar to O2/CO2 at low temperature range (e.g. 700–800 °C), primarily caused by thermo-physical properties of CO2. However, at higher temperature range (e.g. 950–1000 °C), the C-O2 reaction is limited by the external O2 diffusion and the C-CO2 reaction contributes to the carbon consumption, resulting in a higher combustion rate, especially at O2-deficient conditions. The presence of the atomic 18O in the product C18O16O originating from C18O18O confirms that CO2 is indeed involved in the whole oxy-fuel combustion process and the overall reaction could be described as C + C18O18O+16O16O → 2C18O16O. Besides, total contributions to carbon conversion by the C-CO2 reaction decrease as O2 concentrations and particle sizes increasing.

In this study, high-quality thermochromic vanadium dioxide (VO2) thin films were grown on ZrO2/glass by pulsed laser deposition and were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), double beam spectrophotometry and Hall Effect measurement system. Based on XRD results, it can be inferred that the crystal structure of ZrO2 buffer layer can be transformed between monoclinic and tetragonal structures with the increase of buffer layer thickness. Photoelectric performance tests showed that the introduction of ZrO2 buffer layer considerably reduced the phase transition temperature (Tc) and hysteresis loop width (ΔH) of the VO2 films and allowed the visible light transmittance (Tlum) and solar modulation ability (ΔTsol) of the films to be tuned effectively. Especially, when the thickness of the ZrO2 buffer layer was 50 nm, the Tc of the VO2 films reached the minimum value of 48 °C. When the ZrO2 buffer layer thickness increased to 125 nm, the sheet resistance change of the VO2 film attained two orders of magnitude, and their Tlum-90°C and ΔTsol were as high as 50.01% and 7.88%, respectively. These results showed that the ZrO2 buffer layer considerably affected the growth of VO2 films on amorphous glass substrates and was beneficial for the application of VO2 in energy-saving smart windows.