•Very simple bridged siloxane molecules are investigated as potential consolidant for ancient Qin Shihuang’s Terracotta.•The bridged siloxanes show excellent cohesion ability due to the extra crosslinking groups.•The bridged siloxanes show overall better performance than unbridgedsiloxanes, including tetraethoxysilane.Comparing to the research work on the polychromy protection of Qin Shihuang’s Terracotta Army, the protection of the terracotta body itself is somewhat being overlooked. But a very recent survey organized by the State Administration of Cultural Heritage of China shows that the water erosion and salt damage of ancient potteries, including terracotta, are more obvious than previous thoughts. In this work, the protective performances on simulated Qin terracotta samples of two bridged siloxanes with various alkyl bridge groups, bis(triethoxysilyl) ethane and bis(triethoxysilyl) octane, are investigated and compared with tetraethoxysilane and triethoxyoctylsilane. Influences on the porosity and pore size distribution, morphology, physical properties, color alteration and capillary water absorption of untreated and treated terracotta samples are carefully examined. The accelerated freeze-thaw and salt crystallization aging tests are further carried out to evaluate the resistance to aging after protection treatment. The results indicate that both bridged siloxanes show great potential in terracotta consolidation.

Tetraethoxysilane (TEOS) is the most commonly used silicon-based stone consolidant in art conservation. However, it is known that the resulting silica gel phase tends to develop cracks inside the stone as the gel shrinks during aging and drying. Such phenomenon may lead to severe damage to the protected objects. By introducing silica nanoparticles into TEOS, a so-called particle modified consolidant (PMC), may minimize such shrinkage by reducing the volume loss and forming mesoporous structure to weaken the capillary forces. But many previous results show significant color changes on the surface of PMC-treated stones which can not be tolerated in the conservation treatments of cultural heritage. In this work, we designed a three-component composite consolidant which consists of 15 nm silica particles, α,ω-hydroxyl-terminated polydimethylsilane (PDMS-OH) and TEOS. Among the three components, TEOS provides the consolidation function, silica nanoparticles prevent the cracking and increase the salt resistance and PDMS-OH further reduces cracking, decreases the color alteration and increases the resistance to wetting of the stone. Experimental results show that the three components have significant synergistic effect, which makes the material exhibiting best overall performance in terms of cultural heritage protection.

Progress in the development of energy-efficient coatings on glass has led to the study of smart glass with special functional coatings that can regulate solar energy in response to an external stimulus. Thermochromic smart windows are considered attractive because they are visibly transparent and can intelligently control the amount of solar heat (mainly in the near-infrared region) in response to changes in ambient temperature. Discovered over 50 years ago, VO2 is the most promising thermochromic material; however, related materials have not been commercialized because of problems related to cost-efficient preparation, stability and performance. To date, gas-phase deposition methods, such as sputtering and chemical vapor deposition, are the most common methods for the fabrication of VO2 films, but these methods are still dependent on innovative technologies to meet the requirements of practical applications and are excluded from the topic of the current paper. This paper reviews the state-of-the-art solution processes used to prepare VO2 films, with a special emphasis on polymer-assisted deposition methods. The VO2 films prepared by these methods show controllable morphology and thickness and complex optical properties compared with those prepared by gas-phase methods. In fact, single-layered films exhibit the highest integrated visible transparency (43%) and solar-energy modulation ability (14%). These studies suggest that chemical preparation is inexpensive, easy to scale up, and best suited for the practical applications of the fabricated materials.Graphical abstractVO2 films with the Mott phase transition show unique properties including adsorption of ultra-violet light, visible transparency and temperature-responsive modulation ability to near-infrared light, and are key materials for energy-efficient smart windows of the next generation. This review discusses the state-of the art of solution processing of VO2 films.Highlights► Thermochromic VO2 is a promising material for energy-saving smart windows. ► Visible transparency and solar energy modulation ability limit application. ► Solution-based process increases the performance and lowers the cost. ► A series of concepts for the improvement of performance are reviewed.

Nanoporous thermochromic VO2 films with low optical constants and tunable thicknesses have been prepared by polymer-assisted deposition. The film porosity and thickness change the interference relationship of light reflected from the film−substrate and the air−film interfaces, strongly influencing the optical properties of these VO2 films. Our optimized single-layered VO2 films exhibit high integrated luminous transmittance (Tlum,l = 43.3%, Tlum,h = 39.9%) and solar modulation (ΔTsol = 14.1%, from Tsol,l = 42.9% to Tsol,h = 28.8%), which are comparable to those of five-layered TiO2/VO2/TiO2/VO2/TiO2 films (Tlum,l = 45%, Tlum,h = 42% and ΔTsol = 12%, from Tsol,l = 52% to Tsol,h = 40%, from Phys. Status Solidi A2009, 206, 2155−2160.). Optical calculations suggest that the performance could be further improved by increasing the porosity.Keywords (keywords): optical property; porosity; thermochromic property; vanadium dioxide

Free-standing La2Zr2O7 coatings were obtained by plasma spraying, using an amorphous La-O-Zr precursor as the feedstock. The La-O-Zr precursor powder was prepared by coprecipitation. During thermal spraying, the formation of coatings can be regarded as a joint process of melting-solidification, thermal decomposition, and crystallization. The time required for crystal growth was significantly shortened during spraying. Consequently, the average grain size of coatings was approximately 200 nm, with a narrow distribution (100-500 nm). Coatings prepared by this method show better thermophysical properties than those prepared with crystalline La2Zr2O7 powder as the feedstock. The thermal conductivity of the as-sprayed coating was approximately 0.36-0.47 W/m K and the average coefficient of thermal expansion (CTE) is 11.1 × 10−6/K.