Advanced Materials Research Vols. 79-82

Abstract: This paper aims at providing a preliminary understanding in biomechanics with respect to the effect of FPC dental implants on bone remodelling. 2D multi-scale finite element models are created for a typical dental implantation setting. Under a certain mastication force (<200N), a global response from a macro-scale model (without considering coated surface morphology details) is first obtained and then it is transferred to the micro-scale models (with coated surface morphology details and various particle sizes) for micro-scale analysis. A strain energy density (SED) obtained from 2D micro-scale Finite Element Analysis (FEA) is used as a mechanical stimulus to determine the bone remodeling in term of the change in apparent bone densities for cancellous and cortical bones. The change in bone densities is examined as a result of bone remodelling activities over a period of 48 months.

Abstract: This research is concentrated on the effect of concentration of silane-69 used for surface modification on precipitated silica (PSi), on cure characteristic and mechanical properties of PSi filled NR. The PSi content in this study was fixed at 20 phr in order to reveal the effect of silane used to modify PSi, on NR compound and vulcanizate. Moving Die Rheometer (MDR) was used to characterize cure characteristic of rubber compounds. Generally, scorch and cure time of NR would increase with the addition of PSi due to the absorption of accelerator on its surface whereas the addition of Si-69 modified PSi would reduce both scorch and cure time. It was found in this research that the excess amount of Si-69 used increased scorch and cure time of rubber compounds. This was thought to be that the excess of Si-69 led to the formation of polysiloxane clusters which could absorb accelerator in rubber compound and resulted in a prolonged scorch and cure time. In term of vulcanized rubber, it was found that maximum torque increased with the concentration of Si-69 up to 6 %. The polysiloxane formed during the cure characterization test was responsible for the slightly decreased torque after 6% of Si-69 treatment. Nonetheless, even with high concentration of Si-69 used, torque was still higher than that of untreated PSi filled NR. This is widely understood that sulfur atoms in Si-69 molecule are able to participate in the bonding between rubber and silane molecules resulted in the enhancement of crosslink density of the vulcanizate rubber. The increased of modulus at 200 % elongation, tensile strength under tension, with the silane concentration, was evidence of the crosslink enhancement. Tear strength and hardness of the vulcanizates exhibiting the increment, with the silane used, also clearly confirmed the bonding between Si-69 and rubber molecules. It was elucidated from the research that excess of Si-69 would lead to polysiloxane formation, cluster form of silane and crosslinking density. Scanning Electron Microscope (SEM) micrographs and swelling test are also presented to confirm the phenomena.

Abstract: The performance of epoxy thermosets was greatly influenced by the curing agent and curing temperature. It was known that epoxy thermosets cured under high temperature would have high normal forces which could cause fracture of the structure and then decrease the mechanical properties of the material. It was accepted that epoxy curing system should be cured under low temperature with the thermosets had the same properties as those cured under high temperature. It was important to choose proper curing agent to reach the above goal. Latent epoxy curing agent whose main component was the hyperbranched polyester (HBP) with tertiary amine as the end group was prepared and was used to diglycidyl ether of bisphenol A (DGEBA) in this work. The properties such as tensile intensity, bending intensity, impact resistance and dynamic mechanic properties of the resulting epoxy thermosets were evaluated. It was found that the resulting epoxy thermosets cured under low temperature had better mechanical properties than those cured under high temperature. The latent epoxy curing agent whose main component was the hyperbranched polyester with tertiary amine as the end group was adaptive to be used in the epoxy base of composite.

Abstract: In this paper, the in-situ exposure tests of 15 kinds of copper and its alloys were carried out in seawater at Zhanjiang Harbor for 12 months in order to study their anti-fouling abilities and anti-corrosion properties. In the same way, the in-situ anti-fouling tests of copper and bronze were performed in Qingdao for 8 years. Successively, the anti-fouling properties were analyzed combining with the electrochemical process of copper alloy corrosion and biology process of the adhesion. The chemical, physical and biological factors influencing the fouling properties of copper alloys were also investigated. The results showed that the coppers can equip themselves with antifouling performance by producing some toxic substances during the processes of chemical and electrochemical reaction. In addition, the antifouling ability was proved to relate to the exfoliation effect, which was the result of interaction between stain layer adhesion and spalling force of the attachments.

Abstract: Silica has been widely used as non-black reinforcing filler, however, the filler-filler interaction has been an important issue. Cure characteristic and mechanical properties of the rubber compound and rubber vulcanizate were affected both by filler-rubber interaction and filler-filler interaction. There have been, presently, a number of natural fillers which are also used as fillers for the rubber, i.e. fly ash, sawdust and zeolite. This work therefore will study the effect of second filler added into the 13% Si-69 treated precipitate silica (PSi) filled natural rubber compounds. It was revealed that the scorch and cure time of the rubber compound increased with the content of treated PSi. This was the effect of excess of the silane treated onto PSi which would agglomerate and form the cluster of polysiloxane and would then be able to absorb vulcanizing accelerator resulting in extending the scorch and cure time of the rubber compounds. However, this effect was over ruled with the reinforcing effect as could be seen by the increasing, with the contents of PSi, of maximum torque and mechanical properties of the vulcanizates. The NR compounded with treated PSi content of 20 phr selected to study the effect of excess silane on the cure characteristic of hybrid fillers NR composite. The addition of sawdust led to longer scorch time and cure time but not much change of the maximum torque. As expected, the modulus of the rubber vulcanizate increased with the sawdust content whereas the tensile strength and elongation at break decreased with the sawdust content. The incorporation of zeolite could accelerate the cure reaction therefore both scorch time and cure time decreased. The maximum torque also increased with the content of zeolite. Both modulus and tensile strength increased with the content of the zeolite whereas elongation at break tended to be unchanged. In the case of using fly ash as the second filler, the cure time tended to be unchanged. However, the maximum torque tended to be increased with the content of fly ash. It was found that the modulus, tensile strength increased but elongation at break decreased. Interestingly, the excess of Si-69 used effect pronouncedly for the addition of zeolite and fly ash cases as the excess silane could promote the interaction between fillers surface and rubber molecule accept for sawdust

Abstract: AMP-activated protein kinase (AMPK) is a metabolite- sensed protein kinase in various eukaryotes. The activated AMPK regulates important proteins which cause diabetes, obesity, metabolic aberrant, and also breast cancer. In this study, the yeast AMPK structure was used as a template to model the human AMPK structure. By homology modeling, the reliable AMPK structure was built, and the active binding site was defined corresponding to X-ray crystal structure of yeast AMPK By virtual screening the database., All the potent ligands had the H-bond interaction in the key residues, same as the control. Thus, we suggested the phenylamide derivates might be the potent AMPK agonists.

Abstract: The behavior of plastic deformation of Cu-15Cr-0.1Zr in-situ composite under different degree of cold drawing deformation was analyzed by using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results show that both Cu and Cr phases are elongated along cold drawn direction and appear a fibrous morphology; However, Cu phase shows a thread-like fibrous morphology and Cr phase shows a band-like fibrous morphology. The two phases have a coherent relationship of (111)Cu //(011)Cr; When the degree of deformation(ε)is equal to 6.43, the relationship shows// [111]Cu // [110]Cr //cold drawn direction. Furthermore, forming two different morphologies of Cu and Cr phases during cold drawing is also analyzed.

Abstract: As the electrode structure has a great effect on the performance of the benthic microbial fuel cell (BMFC), several graphite electrodes with different shapes (column, plane disk and tubular shape for example) are designed in this paper. The maximum power density (Pm) of BMFC-c and BMFC-d are 20.2 mW•m-2 and 14.9 mW•m-2 respectively, and the internal resistances are 333 Ω and 598 Ω respectively. Three cells are composed of three different sizes of graphite tubes, and their internal diameter of these electrodes are 2.5 cm (called it as BMFC-I for short); 1.0 cm (BMFC-II) and 0 cm (column shape for comparison, BMFC-III) respectively. Test results show that the Pm of BMFC-I, BMFC-II and BMFC-III are 13, 11 and 16 mW•m-2 respectively, and their internal resistances are 435 Ω, 488 Ω and 419 Ω respectively. Results show that the column structure electrode has a lower internal resistance and a higher power density than the disk and tubular structure electrode.

Abstract: The piston pin contact in a typical automotive engine is an example of a highly loaded. Therefore, for piston pin design several aspects are important. Among them are function, cost, NVH, fuel economy, durability, and impact on other design aspects of the engine. Continuously contacting with piston pin, the face of connecting rod, brings about abnormal wear such as unfairwear or earlywear. because the engine get more powered and one requirement for a good fuel economy is to achieve a low level of mechanical friction. In this study, modern low friction coatings and treatment at the piston pin interface aimed to investigate the potential. The profile of coated specimens were observed by non-contact type optical surface measuring system and the friction-wear behaviors of coated specimens were investigated by using piston pin wear tester. Piston pin wear test was performed to analyze the friction and wear behavior. The results showed that the application of low friction coatings and treatment effectively improved tribological performance of the piston pin

Abstract: Starve feed and semi-continuous seed emulsion polymerization were used to control the morphology of core shell latex particles with a vinyl acetate (VAc)/vinyl ester of versatic acid 10(VeoVa10) copolymer core surrounded by a poly(glycidyl methacrylate) (PGMA) shell. Pure core and core-shell structures were confirmed by TEM. The results suggest that core-shell morphology of the two stage emulsion was favoured by higher concentration of emulsifier in the seed latex: the particle size distribution of core-shell latex was broader than that of the core latex, and the average particle size of core-shell latex was larger than that of the core latex. The core-shell structure was not produced using seed emulsion with emulsifier concentration at or below the critical micelle concentration. The core shell emulsion containing epoxy functional group with added ethylene diamine showed an abrupt increase in dynamic shear moduli, G' and G'' and complex viscosity η* (several orders of magnitude) at about 35oC, during temperature ramps, over a wide range of angular frequencies. The time ramps showed that the crosslinking reaction did not occur at 15oC for the core-shell emulsion/amine system. The time for gel formation decreased with increase in temperature.