A thermochromic low-emittance coating: Calculations for nanocomposites of In2O3:Sn and VO2 Appl. Phys. Lett. 99, 131907 (2011); 10.1063/1.3641869 Mg doping of thermochromic VO 2 films enhances the optical transmittance and decreases the metal-insulator transition temperature Vanadium(IV) oxide (VO 2 ) is a unique material that undergoes a reversible phase transformation around 68 C. The material could potentially be used as an energy-efficient coating for windows since its reflectance in the infrared (IR) increases significantly more than in the visible region. Currently, VO 2 is limited by a transition temperature ðs c Þ that is too high, luminous transmittance that is too low or both. In this study, a transition temperature of 45 C is achieved for a reactively sputtered, undoped film by restricting grain size to approximately 30 nm. It is concluded that a higher density of grain boundaries (smaller grain size) provides a greater number of nucleating defects which in turn reduces s c . Similarly, a higher density of grain boundaries may reduce the hysteresis width (difference between transition temperatures in heating and cooling). Also in this study, a new set of optical performance metrics is proposed in which the solar spectrum is divided into the ultraviolet (UV), visible and near infrared (NIR) regions. This approach is more closely aligned with the goals of limiting UV, allowing luminous and modulating NIR transmission. Using these metrics, the optical properties of the low-s c sample were: 2% UV transmittance, 47% luminous transmittance, and 23% NIR modulation (decrease from 43 to 33%). This study demonstrates that the grain size of VO 2 should be viewed as an important parameter for controlling the transition temperature of the material. V C 2015 AIP Publishing LLC. [http://dx.

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A new class of silicone polymer matrix composites was evaluated using a simulated solid rocket motor test apparatus. Conversion of this organic silicone polymer to a ceramic (i.e. silica) structure on exposure to flame impingement or high temperature, accounts for its outstanding thermal stability. A research program was aimed to develop and evaluate this new class of thermal protection materials for military applications. This article presents the effects of the type and form of reinforcements on the thermal performance of a novel class of silicone polymer matrix composites. Reinforcement types such as glass, silica, quartz, NextelTM, and NicalonTM were used. Reinforcement forms such as random continuous-fiber mat, chopped-fiber mat, 2-D fabric, 3-D fabric, chopped roving, and broadgood tapes with different ply angles were tested. Detailed microstructural, mass loss, and peak erosion analyses were conducted on the phenolic-based matrix composite (control) and silicone-based matrix composites to understand their protective mechanisms.

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