Smart Building and Construction Materials

Advances and innovations in materials science and engineering have always played a substantial role in civil engineering, building structural design, and construction. In recent years, extensive effort has been devoted to the applications of stimuli-responsive smart materials and nanostructures in buildings. These smart materials used in the built environment can be defined as those offering specific functional and adaptable properties in response to thermal, optical, structural, and environmental stimuli. Not only do these materials enhance the overall performance of new building construction but also promise safer structures, longer durability of building elements, efficient building energy savings, greater environmental sustainability, and even higher indoor user comfort. Given the increasing imperatives for the above, we have organized this themed special issue that focuses on smart buildings and construction materials. The main aim of this special issue is to encapsulate the current interest and state of research related to the smart materials in building and construction applications, underpinning current and future challenges in building energy, environmental sustainability, and structural safety and durability. In this special issue, after rigorous peer-review processes, the original research papers and review papers accepted cover a wide range of topics that address the critical issues in the development and implementation of smart materials for building design and construction. A total of ten papers in this special issue are listed

Optical thermal insulation via solar-energy harvesting photothermal nano coatings

The current technological advancement has enabled glass-based building facades with double- or triple-glazed transparent panels. However, the conventional glazing technologies cannot effectively reduce building thermal energy loss especially for large area transparent building skin. According to a report by the U.S. Department of Energy, building heating, ventilation, and air conditioning (HVAC) accounted for 14.0 % of primary energy consumption in the United States. Heat loss through windows in cold weather consumes about 3.9 quads, which is estimated to encompass 28.7 % of total HVAC energy consumption. [1] We have developed a novel concept of Optical Thermal Insulation (OTI) without any intervening medium (Fig. 1). Instead of applying a thermal insulator, a transparent photothermal (PT) film can selectively absorb photons near the UV and NIR regions and efficiently convert them to heat, therefore raising the window surface temperature (via free energy). As the inner surface temperature is raised relative to room temperature, the heat transfer at the window inner surface can be effectively reduced via the so-called OTI, especially in winter. It must be noted that the PT films are spectral selective with high absorptions near UV and IR, while allowing high visible transmittance, therefore transparent and ideal for façade engineering. Based on this concept, a so-called “Green Window” has been designed for single-pane applications that meet the U-factor specifications of Department of Energy for colder regions of the United Sates. The “Green Window” is composed of chlorophyll (Chl) retrieved from natural greens (by which the name “Green Window” is derived). [2] A thin film window coating of naturally occurring chlorophyll exhibits strong near UV and NIR absorptions and pronounced photothermal effect, while remaining highly transparent (Fig. 2). Upon collecting solar light, considerable heat is created, effectively raising the window surface temperature, leading to a reduced U-factor less than 1.7 W m-2 K-1, even below the values of double-panes. Based on these experimental results, we demonstrate of a new concept of “optical thermal insulation” that lifts the dependence on insulating materials making single-pane window highly possible. Fig. 2 shows the change in temperature (ΔTg) induced by simulated solar light as a function of time for the multilayer samples of chlorophyll. Consistently, thicker films (each layer is ~ 2 mm) gave greater ΔTg as expected. Conversely, the thicker films exhibit lower visible transmittance (VT). As shown in this figure, the temperature plateaus can be observed after 2 min.-irradiation by solar simulator. Fig. 2b shows ΔTg,max vs. VT for thin films of different layers (a maximum of 6 layers). ΔTg,max vs. VT displays a linear relationship extending to the point where no Chl film was applied (highest VT). Please click Additional Files below to see the full abstract

Deposition of YBCO thin films on silver substrate via a fluorine-free sol-gel synthesis

To further develop grain-textured YBCO thin films for conductor development, we deposited, via a fluorine-free sol-gel synthesis, YBCO thin films on non-textured silver substrate. The interface structures were studied by both x-ray diffraction (XRD) and transmission electron microscopy (HRTEM). XRD data indicated that the YBCO films on silver substrate exhibited c-axis grain orientations. Experimental details are reported on the sol-gel synthesis chemistry and XRD and HRTEM characterization of the YBCO thin films. © 2002 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87877/2/654_1.pd

Functionalization of single-walled carbon nanotubes using isotropic plasma treatment: Resonant Raman spectroscopy study

Functionalization of single-walled carbon nanotubes sSWNTsd by isotropic plasma treatment was studied using resonant Raman spectroscopy. It was shown that plasma-induced functionalization results in the uniaxial isotropic constriction of the nanotubes but preserves their overall structural integrity. It was demonstrated that NH3 ·H2O and hexamethyldisiloxan plasmas yield various types of conductivity for semiconducting SWNTs

Functionalization of single-walled carbon nanotubes using isotropic plasma treatment: Resonant Raman spectroscopy study

Functionalization of single-walled carbon nanotubes sSWNTsd by isotropic plasma treatment was studied using resonant Raman spectroscopy. It was shown that plasma-induced functionalization results in the uniaxial isotropic constriction of the nanotubes but preserves their overall structural integrity. It was demonstrated that NH3 ·H2O and hexamethyldisiloxan plasmas yield various types of conductivity for semiconducting SWNTs

Magnetic Relaxation And Intrinsic Pinning In A Single Crystal Of Bi2sr2cacu2ox

Magnetic-relaxation experiments were performed on Bi2Sr2CaCu2Ox single crystals with the direction of the field parallel to the ab plane. Based on the relaxation data, we have obtained relationships between the activation energy U and the current density j by an approach we developed previously. We found that the activation energy has a logarithmic dependence on j in a wide regime of driving force. It has been reported that CuO2 planes in high-Tc superconductors can act as strong intrinsic pinning centers and that the relation U∼U0ln(jc/j) may describe such a pinning mechanism. Our experimental results have shown good agreement with such a physical model of intrinsic flux pinning. © 1993 The American Physical Society.4795414541

Luminescent hydroxylapatite nanoparticles by surface functionalization

Hydroxylapatite (HA) nanoparticles were functionalized by depositing rare-earth-doped Y2O3Y2O3 nanoparticles on the surface, and the structural evolutions of both HA and Y2O3Y2O3 phases at different annealing temperatures were investigated by x-ray diffraction and transmission electron microscopy. Laser spectroscopy indicated that the surface functionalized HA nanoparticles exhibited strong visible emissions. No visible emissions were observed from rare-earth-doped Y2O3Y2O3 without any substrate, suggesting a doping-induced environmental change of optically active rare-earth elements in the functionalized HA nanoparticles. The luminescent hydroxylapatite nanoparticles may find important applications as a biodegradable substrate for biomarking and drug delivery.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87791/2/183106_1.pd

Interface structure of YBa2Cu3Ox thin films prepared by a non-fluorine sol–gel route on a single-domain substrate

In our previous work, we have shown that a single-domain YBa2Cu3Ox (YBCO) exhibits a low surface resistance. However, the second phase Y2BaCuO5 (211) precipitates inevitably as a result of peritectic reaction. These 211 particles are potential sources of RF losses, which need to be eliminated. In this study, a non-fluorine sol–gel synthesis was developed to deposit a YBCO thin film on the surface of single-domain YBCO. The deposited YBCO thin film entirely covered the 211 particles. The interface structure was studied by high-resolution transmission electron microscopy. The experimental results on sol–gel synthesis and thin film characterization are reported. Also discussed is the underlying mechanism of film growth on single-domain YBCO.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48990/2/u20504.pd

Plasma coating of carbon nanofibers for enhanced dispersion and interfacial bonding in polymer composites

Ultrathin films of polystyrene were deposited on the surfaces of carbon nanofibers using a plasma polymerization treatment. A small percent by weight of these surface-coated nanofibers were incorporated into polystyrene to form a polymer nanocomposite. The plasma coating greatly enhanced the dispersion of the nanofibers in the polymer matrix. High-resolution transmission-electron-microscopy (HRTEM) images revealed an extremely thin film of the polymer layer (∼3 nm) at the interface between the nanofiber and matrix. Tensile test results showed considerably increased strength in the coated nanofiber composite while an adverse effect was observed in the uncoated composites; the former exhibited shear yielding due to enhanced interfacial bonding while the latter fractured in a brittle fashion. © 2003 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71001/2/APPLAB-83-25-5301-1.pd