Papers by Author: Ivan P. Parkin

Abstract: Theoretically thermochromic glazing has the potential to reduce energy consumption in buildings by allowing visible light for day lighting, reducing unwanted solar gain during the cooling season, while allowing useful solar gain in the heating season. In this study building simulation is used to predict the savings made by novel thermochromic glazing coatings compared to standard products, for locations with different climates. The results suggest that thermochromic glazing can have a significant energy saving effect compared to current approaches.

Abstract: Thermochromic glazing is a type of intelligent glazing; one where the properties of the glazing change according to some external stimulus. More particularly a thermochromic window is a device that changes its transmission and reflectance properties at a critical temperature (Tc). Atthis specific temperature the material undergoes a semi-conductor to metal transition. At temperatures lower than Tc the window lets all of the solar energy that hits it through. At emperatures above Tc the window reflects the infra-red portion of solar energy. In such a way thermochromic windows may help reduce air conditioning and heating costs leading to more energy efficient buildings. This review details the nature of the semi-conductor to metal transition and indicates how substitutional doping within a crystal lattice can be used to manipulate and fine tune the critical temperature. Also detailed is the underlying science and methodologies so far employed in the production of thermochromic thin films.

Abstract: A numerical model was developed which enables the calculation of the optical constants (refractive index, n and extinction coefficient, k) of thermochromic coatings based in undoped and doped vanadium dioxide thin coatings deposited on glass for use as an intelligent window - a window that can change the optical properties in response to the temperature. From experimental results it can be seen that the vanadium dioxide coating prepared by Atmospheric Chemical Vapour Deposition shows a switching efficiency of about 30% at 2500 nm. In the visible range the transmittance and the reflectance does not change with the temperature both for the undoped and Nb doped VO2. For the Nb doped vanadium dioxide coating the switching efficiency is about 20% at 2500 nm. From the numerical simulations a n=2.89 and k=1.33 above Tc and n=2.39 and k=0.52 below Tc (at wavelength of 2500 nm) were determined for the undoped vanadium dioxide coating. The Nb doped vanadium dioxide coating calculations results on n= 2.45 and k=1.56 above Tc and n=1.92 and k=0.88 below Tc.

Abstract: The results of a new potentiometric technique for in situ diagnostics of self-propagating high-temperature synthesis (SHS) of different complex oxides are presented. This technique is based on electrochemical processes. The characteristic peaks attributed to the electric responses from cation streams of alkali, alkaline-earth and some elements of group VI are discovered and the respective routes of the corresponding chemical reactions found.

Abstract: New experimental methods for investigations of phase formation during SHS have been established. First experiments using penetrating synchrotron radiation and energy dispersive detectors for different classes of complex inorganic materials were carried out at ESRF (Grenoble, France) and Daresbury (UK). A new and very sensitive thermal imaging method (Thermal Imaging Technique (TIT)) based on continuous registration of the whole combustion process by using highly sensitive IR-camera and software developed by MIKRON Instruments Co. (USA) was used for precise registration of the combustion parameters. SHS was performed on different types of pure and doped complex inorganic materials in pellet and powder form in a range of dc magnetic fields up to 20 T and in electrical field strengths up to ±220 kV/m. The dc magnetic field was applied during the reaction, supplied either by a permanent magnet (transverse, up to 1.1 T) or by an electromagnet (longitudinal, up to 20 T). The dc electrical field was applied along the direction of the combustion wave front propagation. The combined processes of SHS and SLS (Selective Laser Sintering) of 3D articles for different powdered compositions were optimized with laser irradiation power.