Acoustic measurements in low-density gases

Abstract

Resonant acoustic measurements in a half-inch tube, in the neighbourhood of 2000 Hz, were carried out in argon, nitrogen and air when the mean gas pressure was varied from 30 mm Hg up to atmospheric. The variation of the sound pressure levels (SPL) with mean gas pressure can be expressed as SPL=58 lg (p(M/Mair)12/), where p is the mean gas pressure and M is the molecular weight of the gas. The sound field was traversed by a 2 mm damped probe whose attenuation was found to be dependent on the type of gas, the mean gas pressure and the strength of the sound field.

Shrinkage Volume, Compressive Strength, and Surface Roughness Y-TTRIA Stabilized Tetragonal Zirconia Polycrystal (Y-TZP) Using Binders Variation PVA:PEG as an Alternative Dental Implants Materials

“…PEG has a low Tg, whereas a polymer with a low Tg (more elastic chains) has a lower density. 12 13 Using too much binder can decrease the density of material so that the result becomes easy to shrink when sintering. 17…”

“…Binder must remove to avoid defects such as black discoloration, closed porosity, bloating, and defects in the final shape of the ceramic. 13 In ceramics, sintering is carried out at 1200°C. Binder removal usually occurs at 600 to 700°C for pure polymers and can be higher for ceramic powders.…”

“…Based on research by Mohanty, adding PVA binder concentrations of 2, 3, and 4% in alumina will increase the material's porosity after sintering. 13 It is due to removing the binder (binder burnout). The increase in porosity due to the loss of this binder will increase the surface roughness of a material.…”

“…The binder acts as a granule binder to maintain the shape and increase the density of the ceramic after going through the sintering process. 13 Polyvinyl alcohol (PVA) and polyethylene glycol (PEG) are organic binders commonly used to form ceramics. PEG combined with PVA reduces the glass transition temperature (Tg) of PVA so that the plastic properties of ceramics can be increased.…”

Gasdichtemessung mittels Akustischer Methode / Gas density measurement by an acoustic method

“…Kompliziert und aufwendig ist die Ermittlung der Dichte von Gasen und Gasgemischen. Die meisten Geräte, die für diesen Zweck im Laufe der Jahre entwickelt wurden, lassen sich nach ihren Meßprinzipien wie folgend einteilen: -Frequenzänderung schwingender mechanischer Elemente [1], -Absorption von Strahlungen verschiedener Wellenlän-gen [3; 4], -Änderung des Stromes in einer Ionisationskammer [5], -Frequenzänderung von akustisch abgestimmten Hohlräumen [6], Der Großteil der nach diesen Prinzipien gebauten Meßge-räte ist technisch aufwendig, und die meisten sind nur für sehr begrenzte Werte von Dichte, Druck oder Temperatur anwendbar. Die hier beschriebene Methode beruht auf der Messung des Wechseldruckes in einem Schallfeld.…”