Browsing by Subject "Aerogel"

Now showing 1 - 3 of 3

Open Access
Fluorescent aerogel films for TNT sensing
(2009) Yıldırım, Adem
Silica aerogels are unique materials with extraordinary properties such as, high porosity, large surface area and low refractive indices. Due to these properties, they can be applied to a wide range of areas including, insulation, catalyst support, sensors and dielectric materials. However, until know because of their poor mechanical properties and costly production a few applications of aerogels were realized. Ambient pressure drying method is a promising way to produce low cost aerogels and thus expanding the realized application areas of aerogels. This method is based on lowering the surface tension on the gel network, in order to minimize the collapse of the gel during drying. For this purpose gel surface can be modified to make it hydrophobic. In the first part of this work, ambient pressure production of fluorescent aerogel thin films are described. The produced fluorescent films were characterized to identify their morphological, optical and surface properties. The gel was produced by using methlyltrimethoxysilane (MTMS) to produce hydrophobic gel. A porphyrin derivative (TCPPH2) was simply mixed with the sol before gelation for the fluorescence property. After gelation and aging the produced gels are homogenized and spin coated on glass substrates. The produced films were found to be highly porous (60.3-77.1%), fluorescent and transparent in visible region (82-89%). In the second part, sensing performances of the films were examined by using the common explosive trinitrotoluene (TNT). All films show fluorescence quenching based sensing against TNT exposure. The quenching efficiency of the films is highly thickness dependent. For the thinnest film (120 nm) the quenching efficiency was found to be 8.6% in 10 seconds and for the thickest film (1100 nm) film 2.1% in 10 seconds.
Open Access
Highly transparent, flexible, and thermally stable superhydrophobic ORMOSIL aerogel thin films
(American Chemical Society, 2011) Budunoglu, H.; Yildirim, A.; Güler, Mustafa O.; Bayındır, Mehmet
We report preparation of highly transparent, flexible, and thermally stable superhydrophobic organically modified silica (ORMOSIL) aerogel thin films from colloidal dispersions at ambient conditions. The prepared dispersions are suitable for large area processing with ease of coating and being directly applicable without requiring any pre- or posttreatment on a variety of surfaces including glass, wood, and plastics. ORMOSIL films exhibit and retain superhydrophobic behavior up to 500 °C and even on bent flexible substrates. The surface of the films can be converted from superhydrophobic (contact angle of 179.9°) to superhydrophilic (contact angle of <5°) by calcination at high temperatures. The wettability of the coatings can be changed by tuning the calcination temperature and duration. The prepared films also exhibit low refractive index and high porosity making them suitable as multifunctional coatings for many application fields including solar cells, flexible electronics, and lab on papers. © 2011 American Chemical Society.
Open Access
Production of aerogel-modified expanded perlite aggregate and clay (AEP/C) board and investigation of physical and mechanical properties
(2021-08) Mercan, Elif
Expanded perlite aggregate (EPA) is an inorganic insulation material preferred because of its low thermal conductivity. In other respects, it has disadvantages in buildings because of its high moisture retention, sintering in case of fire, and fragility. This study aims to produce a clay-based insulation board by eliminating these disadvantages of EPA with aerogel modification. The sol-gel method was chosen, allowing low-cost aerogel synthesis in a laboratory and permitting the control of parameters throughout the process. The optimum synthesis process was designed by examining the acid and base variables in the process. The recipe obtained at the aerogel synthesis was used to constitute aerogel-modified expanded perlite aggregate (AEP). AEP particles were prepared with clay matrix under determined process conditions, and characterization tests were carried out. According to the results, aerogel modification prevents high-temperature sintering of EPAs. The AEPs and the aerogel-modified expanded perlite aggregate and clay (AEP/C) composites' density remained almost unchanged compared to the EPA and expanded perlite aggregate and clay (EP/C) control samples. Thus, this can be offered that the prepared boards are lightweight and can maintain low thermal conductivity. The results showed that the mechanical strength of the boards was slightly higher than the control samples and the aerogel modification has almost no effect on mechanical strength.