Investigation of a colloidal damper.

A novel application of nanotechnology in the field of mechanical engineering, called colloidal damper (CD), is investigated. This device is complementary to the hydraulic damper (HD), having a cylinder-piston construction. Particularly for CD, the hydraulic oil is replaced by a colloidal suspension, which consists of a mesoporous matrix and a lyophobic fluid. In this work, the porous matrix is from silica gel modified by linear chains of n-alkylchlorosilanes and water is considered as an associated working fluid. A design solution from a practical point of view of the CD test rig and the measuring technique of the hysteresis are described. A brief review of the water physical properties relative to the CD concept is presented. Influence of the bonding density, length of the grafted molecule, pore diameter, and particle diameter on the CD hysteresis is investigated for distinctive types and mixtures of silica gels. Temperature variation during functioning is recorded and the CD cycle is interpreted from a thermodynamic standpoint. Variation of the CD dissipated energy and efficiency with pressure, water quantity, and relaxation time is illustrated. Experimental results are justified by the analysis of the water flow into the porous matrix, CD thermodynamics, and the mechanism of the energy dissipation. Our findings agree with the previously published data.

TEM Investigation and Electron Diffraction Study on Dispersion of Gold Nanoparticles into a Nylon 11 Thin Film during Heat Treatment.

We have investigated the effect of heat treatment on the changes in the microstructure of nylon 11 thin films containing nanosized Au particles by means of lateral and cross-sectional transmission electron microscopy. It was observed that, on heat treatment, the Au islandlike particles initially deposited on the nylon 11 surface penetrated into the polymer layer to form a composite film consisting of nanosized spherical Au particles dispersed in a polymer matrix, while the initially amorphous nylon 11 matrix crystallized to the alpha-crystalline form. The surface stress coefficient of the Au particles, calculated from the lattice constant determined by the electron diffraction patterns, decreased as the Au particles penetrated into the polymer matrix, which can be due to both coalescence of the particles to a spherical shape and reduction of the surface free energy of the particles by embedding in the matrix. The molecular chain motion of the nylon 11 matrix during the crystallization process is suggested to be responsible for the dispersion of Au particles into the polymer matrix. Copyright 1999 Academic Press.

Novel Method for Preparation of a Nanosized Gold Catalyst Supported on TiO2.

A TiO2 surface was readily modified with nanosized gold particles prepared by the thermal relaxation technique. Adsorption of the gold particles was very rapid, and the adsorbed gold particles distributed independently. By the two-step calcination of the modified TiO2, the nanosized gold particles were immobilized on the TiO2 surface without size growth or coagulation. The supported gold particles showed low-temperature catalytic activity on CO oxidation. The preprepared nanosized gold particles interacted with TiO2. Copyright 1999 Academic Press.