Mechanical properties improvement of silica aerogel through aging: Role of solvent type, time and temperature

Omranpour, Hosseinali; Dourbash, Alireza; Motahari, Siamak

doi:10.1063/1.4873786

Cited by 15 publications

(8 citation statements)

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“…Four additional aerogel cylinders were used around the outside perimeter of the coldfinger base to laterally secure the assembly. No mechanical degradation of the aerogel cylinders was observed under these conditions, which is consistent with the compressive strength of silica aerogels, for which values of 1 MPa (0.25 g/cm 3 ) 26 and 0.047–0.11 MPa (0.1 g/cm 3 ) 27 have been reported.…”

Section: Resultssupporting

confidence: 88%

First demonstration of an all-solid-state optical cryocooler

et al. 2018

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Solid-state optical refrigeration uses anti-Stokes fluorescence to cool macroscopic objects to cryogenic temperatures without vibrations. Crystals such as Yb3+-doped YLiF4 (YLF:Yb) have previously been laser-cooled to 91 K. In this study, we show for the first time laser cooling of a payload connected to a cooling crystal. A YLF:Yb crystal was placed inside a Herriott cell and pumped with a 1020-nm laser (47 W) to cool a HgCdTe sensor that is part of a working Fourier Transform Infrared (FTIR) spectrometer to 135 K. This first demonstration of an all-solid-state optical cryocooler was enabled by careful control of the various desired and undesired heat flows. Fluorescence heating of the payload was minimized by using a single-kink YLF thermal link between the YLF:Yb cooling crystal and the copper coldfinger that held the HgCdTe sensor. The adhesive-free bond between YLF and YLF:Yb showed excellent thermal reliability. This laser-cooled assembly was then supported by silica aerogel cylinders inside a vacuum clamshell to minimize undesired conductive and radiative heat loads from the warm surroundings. Our structure can serve as a baseline for future optical cryocooler devices.

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Section: Resultssupporting

confidence: 88%

First demonstration of an all-solid-state optical cryocooler

et al. 2018

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“…As equivalence ratio increases, the dry film thickness increases, possibly due to the change in mixing properties of Mg and MnO 2 that are affected by their differing particle morphologies. Shrinkage of sol-gel films has been shown to be a function of porosity, with low liquid loadings leading to high capillary forces which collapse the film structure and produce denser films [28], [29]. The same trend is apparent in these films, as dry film thickness increases with solids loading, and deposition density is highest for high solids loadings.…”

Section: Deposition Characteristicsmentioning

confidence: 97%

Effects of rheological properties on reactivity of energetic thin films

Meeks

Clark

Cano

et al. 2015

Combustion and Flame

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Magnesium (Mg) and manganese dioxide (MnO 2) powders were mixed with polyvinylidene fluoride (PVDF) binder and n-methyl pyrrolidone (NMP) solvent and blade cast onto stainless steel foil. The rheological properties of these mixtures were investigated to quantify the mixing condition. Parameters including wet film thickness, equivalence ratio and solids loading were varied. Flame speed and calorific output were investigated for each of these parameters. Results show energy propagation rates increased as a function of dry film thickness, although calorific output remained relatively constant. Stoichiometriclly fuel rich compositions were selfquenching, demonstrating the necessity of available oxygen for reaction propagation. A 0.45 solids-liquid mixing ratio resulted in up to an order of magnitude higher energy propagation rate for both open and confined configurations. Rheometry measurements and physical characterizations of the films reveal that the solids loadings resulting in the most stable suspensions also produced the highest energy propagation. Changing solids loading affects the density of the film, which in turn affects energy propagation. Capillary drying forces at high liquid loadings result in higher porosity leading to reduced deposition density and thickness. Very high solids loading results in films with dilatant properties and poor mixing. These results show solids loading affects mixing and energy propagation and could impact slurry cast energetic materials as in additive manufacturing processes.

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“…The effect of aging and drying time on the physical properties of alumina aerogels [4].…”

Section: öZetmentioning

confidence: 99%

“…Yeni çapraz bağların oluşması, büzülme küçülmesine sebep olur bu da jelin viskozitesini arttırır. Yaşlandırma işlemi jel omurgasını güçlendirir ve kuruma sırasında meydana gelecek olan büzülmeyi azaltır [4].…”

Section: Introductionunclassified