Silicon elastic modulus

The elastic modulus of laminated composite plate in which an ER silicone gel of carbonaceous particles is sandwiched between two PVC sheets also changed under the influence of an electric field. It was found that an electric field of 1.17 kV/mm caused a gain in the elastic modulus of the gel of 13% [57]. 

Armor. Silicon carbide is used as a candidate in composite armor protection systems. Its high hardness, compressive strength, and elastic modulus provide superior ballistic capability to defeat high velocity projectile threats. In addition, its low specific density makes it suitable for applications where weight requirements are critical (11). 

More detailed calculations of the elastic properties of model networks have confirmed Phillips model. The coordination dependence of the elastic modulus is shown in Fig. 2.12 (He and Thorpe 1985). Both the modulus Cn and the number of zero frequency vibrational modes, /, drop to zero at the critical coordination of 2.4, as predicted by Eq. (2.17). The properties are explained in terms of percolation of rigidity. The coordination of 2.4 represents the lowest network coordination for which locally rigid structmes are fully connected, so that the entire network is rigid, but only just so. The elastic modulus is therefore non-zero and continues to increase as the network becomes more connected. The four-fold amorphous silicon network is far from the critical coordination and is very rigid. 

Fig. 23. Changes of crosslinking density n,. in netformation from a low-molecular-weight silicone rubber at 20 °C, calculated from the elastic modulus (1) and equilibrium swelling in toluene (2) [46]...

Fig. 6. Tapping Mode (left) versus force modulation mode (right) picture with the corresponding height and elasticity modulus profiles of a solution-cast 20wt% silicone thin copolymer film.

The most stable, adhesive and hydrophobic silicalite-1 films can be obtained by in situ crystallization on the silicon substrate, followed by calcination to remove the organic template.[105] Their elastic modulus reaches 30-40 GPa, but the dielectric constant was measured to be 2.7-3.3. These findings suggest an inverse relationship between the mechanical strength of the films and the lowest achievable dielectric constant. 

Beta 21-S. The Beta 21-S alloy is a relatively new metastable beta alloy (Ref 1). It was designed to have good formability, similar to Ti-15-3, but also has improved oxidation resistance, creep resistance, and high-temperature strength relative to Ti-15-3. Composition ranges and room-temperature tensile properties for Beta 21-S are listed in Tables 7.1 to 7.3. The alloy contains approximately 15% Mo, 3% Al, and 2.8% Nb, with additions of silicon (Ref 1). It is normally provided in the beta solution-treated condition. Beta 21-S has an elastic modulus close to that of bone and hnds use in prosthetic application. It has excellent high-temperature stability and can be used at temperatures up to 290 °C (550 °F). 

The chemical and mechanical stability of poly(n-butyl acrylate)(PnBA) to weathering, especially to solar radiation, is of interest for possible use of this material as an encapsulant/ pottant for silicon cell solar energy arrays. This application requires that the material retain an acceptable level of its desirable properties, such as transparency, elastic modulus, etc., over several years of exposure to intermittent moisture, temperatures ranging from -10 to 50 C, solar radiation, and other norms and extremes of exposure conditions. Knowledge of the dependence of changes in properties and composition of the material on exposure conditions is a requisite for establishing reasonable estimates of its prospective performance lifetime characteristics. 

The elastic modulus of sintered silicon carbide with 5 % porosity is 468.9 GPa. What is the porosity of a specimen with an elastic modulus of 350 GPa ... 

Additional TMDSC study of other vinyl polysiloxane, polyether and polysulfide impression materials is important to verify if the polymer transitions shown in Figures 16 to 19 generally exist in different products and to investigate the effects of other temperature modulation conditions. Complementary research on correlations with clinically relevant mechanical properties of the elastomeric impression materials is needed to verify if these thermal analyses have useful predictive power. Interestingly, when compared at apparently similar viscosities, the reported values of the elastic modulus [3] are highest for the vinyl polysiloxane silicone impression materials, intermediate for the polyether impression materials, and lowest for the polysulfide impression materials, in reverse order to the relative values of Tg fovind in our thermal analyses [45]. Our X-ray diffraction and scanning electron microscopic study [47] of these impression materials has shown that they contain substantial amounts of crystalline filler particles in the micron size range, which are incorporated by manufacturers to achieve the clinically desired viscosity levels. Tliese filler particles should have considerable influence on the mechanical properties of the impression materials. 

A number of approaches have been explored for increasing the dielectric constant of elastomers for DEs. The most common approach involves the addition of high dielectric constant filler materials to an elastomer host. Silicone is of particular interest for this type of approach as it possesses good actuation properties to begin with, is readily available in gel form, and has a low dielectric constant. Results thus far do not appear particularly promising increases in dielectric constant have been met with concomitant increases in dielectric loss and reductions in dielectric breakdown strength [184—186]. It has also been shown that the elastic modulus is affected by the addition of filler [187]. 

Jung et al. have developed a synthetic elastomer composed of acrylonitrile butadiene rubber copolymer [211, 212]. The properties of the copolymer can be tuned by changing its composition. Reported data for dielectric constant, elastic modulus, and strain relaxation are promising (see Table 1.2). The synthetic elastomer provides some improvement over VHB and some silicone hlms under certain conditions however, the tests were limited to low prestrain (60% radial), where the performance of VHB hlms is poor. 

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