On the mechanical stability of mesoporous silica SBA-15

Endurance Tests on a Colloidal Damper Destined to Vehicle Suspension

“…9(d)]. Such results suggest that the fatigue fracture of silica gel grains occurs from the inside, explosion-like, oppositely to the, previously reported [37][38][39][40], implosionlike collapse of silica under wet pressurization. Difference of grain fracture mechanism may explain why [37][38][39][40] reported reduction of the specific pore volume and mean pore diameter, due to the formation of solely small pores at the expense of the original ones.…”

“…Since the distributions obtained before and after loading tests are almost superposed, one concludes that under few working cycles the silica gel particles and their coatings are not damaged by pressurizations up to 100 MPa. This result is remarkable since dry silica gel particles crush under compression at 20-30 MPa [37][38][39][40]. Thus, the uniform pressure distribution in the liquid surrounding the micro-grains seems to prevent them from premature fracture.…”

“…9(b)], but unexpectedly, it is much wider toward both smaller and larger grains, even larger than the initial maximum diameter of the silica gel particles. In order to explain this, note that an enhanced population of hydrophilic silanol groups occur at the fracture of silica gel particles [40], since new surfaces, uncovered by the water-repellent coating are generated during fragmentation. For a dispersion of such silica particles in water, adhesive bonds may be seen forming and fracturing between some of the particles to build doublets, triplets and larger aggregates; they exist even at small silica concentrations and even in ostensibly perfect colloidal suspensions [37].…”

“…On the other hand, the major sources of structural resonances and their frequency ranges are [29]: rigid body vibrations of bouncing, pitching and rolling on suspension systems and wheels (0.5-2 Hz), forced vibrations of the vehicle body due to the engine shake (11)(12)(13)(14)(15)(16)(17), bending and torsional vibration of the body as a whole (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40), ring mode vibration of the passenger compartment and bending vibration of driveline (50-150 Hz). Thus, structural resonances of various systems in a motor car are in the range of 0.5-150 Hz, but the resonances connected to suspension systems and wheels are in the domain of 0.5-2 Hz [28][29][30][31][32].…”

Asymmetric Catalysis in Confined Space Provided by l-Proline Functionalized Mesoporous Silica with Plugs in the Pore

“…The band at 480 cm -1 can be attributed to the symmetric stretching mode of Si-O-Si bond due to the motion of an oxygen atom in a plane perpendicular to the Si-O-Si bonds [40]. This band also could be interpreted as D1 vibration mode of (SiO 4 ) tetrahedra in the network with the one oxygen atom not bonded to another silicon atom [41]. While FTIR spectra (not shown here) indicated the presence of proline organocatalyst by showing bands at 3000 cm -1 , which were due to C-H stretching of alkyl chain.…”