Preparation and Water-Absorbing Capacity of Poly(Acrylic Acid)/Montmorillonite Composites

Poly (acrylic acid)/montmorillonite (PAA/MMT) superabsorbent composites was synthesized by high temperature rapid-induced solvent polymerization reaction. The structure of this composites was investigated by XRD. The relationship between reaction condition and water-absorbing capacity of this composites was researched. The result shows that, when montmorillonite content is less than 5 wt%, PAA/MMT composites is nanophase materials. With the increase of cross linker, neutralization degree of acrylic acid, or montmorillonite content, water-absorbing capacity of prepared composites first rises then decreases. When cross linker content is 0.225 wt%, neutralization degree is 70%, and montmorillonite content is 5 wt%, PAA/MMT composites possess microporous structure and its water-absorbing capacity is 511 times of the solid weight itself.

In situ monitoring magnetism and resistance of nanophase platinum upon electrochemical oxidation

Controlled tuning of material properties by external stimuli represents one of the major topics of current research in the field of functional materials. Electrochemically induced property tuning has recently emerged as a promising pathway in this direction making use of nanophase materials with a high fraction of electrode-electrolyte interfaces. The present letter reports on electrochemical property tuning of porous nanocrystalline Pt. Deeper insight into the underlying processes could be gained by means of a direct comparison of the charge-induced response of two different properties, namely electrical resistance and magnetic moment. For this purpose, four-point resistance measurements and SQUID magnetometry were performed under identical in situ electrochemical control focussing on the regime of electrooxidation. Fully reversible variations of the electrical resistance and the magnetic moment of 6% and 1% were observed upon the formation or dissolution of a subatomic chemisorbed oxygen surface layer, respectively. The increase of the resistance, which is directly correlated to the amount of deposited oxygen, is considered to be primarily caused by charge-carrier scattering processes at the metal–electrolyte interfaces. In comparison, the decrease of the magnetic moment upon positive charging appears to be governed by the electric field at the nanocrystallite–electrolyte interfaces due to spin–orbit coupling.

Nanophase Ceramics: Boon for Osseointegration

Traditional materials utilized for dental applications have been selected based on their mechanical properties and ability to remain inert in vivo; this selection process has provided materials that satifisfy physiological loading conditions but do not duplicate the mechanical, chemical, and architectural properties of bone. The less than optimal surface properties of conventional materials have resulted in clinical complications that necessitate surgical removal of many such failed bone implants due to insufficient bonding to juxtaposed bone. Due to unique surface and mechanical properties, as well as the ability to simulate the three-dimensional architecture of physiological bone, one possible consideration for the next generation of orthopedic and dental implants with improved efficacy are nanophase materials.

Drag Reduction With Superhydrophobic Riblets

Samples combining riblets and superhydrophobic surfaces are fabricated at University of Pittsburgh and their drag reduction properties are studied at the Center for Nanophase Materials Sciences (CNMS) in Oak Ridge National Laboratory with a commercial cone-and-plate rheometer. In parallel to the experiments, numerical simulations are performed in order to estimate the slip length at high rotational speed. For each sample, a drag reduction of at least 5% is observed in both laminar and turbulent regime. At low rotational speed, drag reduction up to 30% is observed with a 1 mm deep grooved sample. As the rotational speed increases, a secondary flow develops causing a slight decrease in drag reductions. However, drag reduction above 15% is still observed for the large grooved samples. In the turbulent regime, the 100 μm grooved sample becomes more efficient than the other samples in drag reduction and manages to sustain a drag reduction above 15%. Using the simulations, the slip length of the 100 μm grooved sample is estimated to be slightly above 100 μm in the turbulent regime.