Near-surface deformation under scratches in polypropylene blends Part I Microscopic characterization of deformation

A microstructural characterization approach has been developed to study the mechanisms of near-surface deformation under surface scratches in injection-molded polypropylene blends with over 20% rubber modifier (thermoplastic polyolefin or TPO). The near-surface microstructure of the material before and after scratching was characterized with different techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), optical microscopy and X-ray diffraction. It was observed that the TPO material plastically deformed by forming shear band structure under surface scratches. Materials inside shear band dilated and the extent of dilation could be measured from the characteristic angles between the shearband boundary and rubber particles. At a higher applied normal load (>200 g for the test in this study), evidence for surface fracture was observed. At even higher loads (>400 g), significant amounts of sub-surface voiding were observed, due to the delamination between the rubber phases and the polypropylene matrix. The observation of both the dilation of materials inside shearbands and the subsurface voiding at high normal loads advanced the understanding of scratching whitening mechanism in this kind of important materials. It was observed that the talc additives had no obvious influence on shear band nucleation and propagation. Results obtained in this study suggest that a strong interfacial adhesion between rubber phase and PP matrix is crucial to improving the scratching resistance of rubber modified polypropylene blends.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44774/1/10853_2004_Article_5118386.pd

Self Assembly and Optical Properties of Dendrimer Nanocomposite Multilayers

Ultrathin multilayers are important for electrical and optical devices, as well as for immunoassays, artificial organs, and for controlling surface properties. The construction of ultrathin multilayer films by electrostatic layer-by-layer deposition proved to be a popular and successful method to create films with a range of electrical, optical, and biological properties. Dendrimer nanocomposites (DNCs) form highly uniform hybrid (inorganic–organic) nanoparticles with controlled composition and architecture. In this work, the fabrication, characterization, and optical properties of ultrathin dendrimer/poly(styrene sulfonate) (PSS) and silver–DNC/PSS nanocomposite multilayers using layer-by-layer (LbL) electrostatic assembly techniques are described. UV-vis spectra of the multilayers were found to be a combination of electronic transitions of the surface plasmon peaks, and the regular frequency modulations attributable to the multilayered film structure. The modulations appeared as the consequence of the highly regular and non-intermixed multilayer growth as a function of the resulting structure. A simple model to explain the experimental data is presented. Use of DNCs in multilayers results in abrupt, flat, and uniform interfaces.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56176/1/1032_ftp.pd

Spatio-temporal distribution of granite-related rare metal deposits and W-Sn deposits in South China and their genetic relationship

The strategic mineral W-Sn deposits in China are mainly concentrated in South China, and many rare metal mineralizations, such as Li, Rb, Be, Nb, Ta, etc., are often coproduced with them. However, the genetic relationship between them is unclear. Based on the analysis of research data related to granite-related rare metals and W-Sn deposits in South China, we believe that the two types of mineralization have a close spatio-temporal relationship at multiple scales, such as metallogenic belts, ore fields, deposits, and minerals. In addition, the ore-forming material source, mineralization process, and ore-controlling structures are similar, indicating that they may have derived from a same granitic mass and the mineralization usually have close genetic relationship with the high evolved granite. Therefore, the exploration and research data of W-Sn deposits in South China can be used to explore and study rare metal deposits