Abstract: The centrifugal casting process was adopted to fabricate Al-30Si-8Mg composites tubes reinforced with in-situ particles, which was used to produce the cylinders used in 149cc engine by high pressure die casting. The relations between the microstructures along the radial direction and the hardness and wear resistance of the casting were researched. The internal surface of the cylinder was treated and a bench test for the engine was carried out. The results show that, 1) a large number of primary Si/Mg2Si particles are segregated and enriched in the inner layer of the Al-30Si-8Mg casting, while no particle is in the outer layer, and the maximum particle volume fraction is up to 31.9 vol. %; 2) the region which has more primary particles, the hardness value is higher, and the wear resistance is better as well in the casting; 3) the cylinder assembled on the air-cooled engine successfully passes through the endurance test for 200 hours, and the maximum output power and torque reach 8.18 KW and 10.77 N·m, respectively, while a slight scuffing occurs on the internal surface of the cylinder in the later phase of the test.
Abstract: Experiment investigation were conducted on square honeycomb structure made out of sugar palm reinforced polylactic acid (PLA). This paper investigate the compression and tensile properties of new and recycled sugar palm/PLA composite. Short fiber were obtain by crushing and then mix with PLA before being hot pressed at 180°C. The 3mm plate were then developed into sandwich square honeycomb structure. The result show small decrement in strength pattern.
Abstract: In this study, electro nickel coating was applied and its effect on the electrical conductivity and mechanical properties was investigated in Cu/Ni/Al/Ni/Cu clad composite after annealing at various temperature. After annealing at 300OC for 3hrs, the interface reaction layer at the Cu/Al interface was observed to be 3μm and no reaction layer was observed at the Ni/Al interface. After annealing above 400OC for 3hrs, the interface reaction layer at the Cu/Al interface in the absence of Ni layer was observed to grow more rapidly with increase of annealing temperature compared to that at the Ni/Al interface. The electrical conductivity increased after annealing up to 300OC for 3 hrs. possibly because of enhanced interface bonding and the recovery in the matrix. However, it was deteriorated after annealing above 400OC for 3 hrs. because of the formation of interface intermetallic. The more localized bending in the as-roll-bonded clad composite and that annealed at 200°C can be attributed to the near-zero and negative hardening rate in bending over the whole displacement. In this case, once bending occurs, bending continue to occur in the localized region because the work hardening due to the localized bending is negligible, leading to the localized fracture.
Abstract: Sharp V-notches with various angles often appear in engineering structures. When being loaded, the high stress at the apex could result in crack propagation on the structure and further fracture. For this reason, safety evaluation should be emphasized for products or engineering structures with such geometric characteristics. Sharp V-notches are regarded as wedge structures that the above situations seriously and often appear on brittle materials. Regarding the stress intensity factor K of the driving force for wedge structure failure, Chen, Dunn, and Seweryn, with numerical analysis for the fracture experiment, explained that the critical stress intensity factor Kc for single isotropic material fracture could be the intensity failure specification for wedge structures. Nevertheless, V-notched brittle materials are likely to receive great stress over the surface elastic energy of the structure when being loaded, causing brittle failure at the apex. When the high-strength and light-weight composite material is attached to reinforce the surface of brittle materials, the energy is reinforced to enhance the critical stress intensity factor of the overall structure, aiming to improve the failure of brittle materials resulted from stress singularity. This paper therefore tends to discuss the effects of the composite attachment, layer, and fiber reinforced direction on the critical stress intensity factor when the structure is being fractured.
Abstract: Bio-based and phosphorus-free coating was fabricated by layer-by-layer assembly method to obtain the flame retardant polyester-cotton fabric. For the first time, the modified polyester-cotton fabrics were prepared by utilizing positively charged polyethylenimine and negatively charged alginate together with subsequent crosslinking of calcium ion. Scanning electron microscopy and energy-dispersive X-ray demonstrated that the calcium ion crosslinked coating was successfully constructed on the substrate. The flame retardancy was investigated by horizontal flame test. The fire resistance of SA/PEI-Ca sample was enhanced significantly compared with the pure sample, as evidenced by the obvious reduction (16%) of flame spread rate and complete char residue.
Abstract: The microfluidic has been applied to the field of bio-medicine, micro fluidic electronic in recent years. In this paper we reported a simple methodology to fabricate PDMS microfluidic channels. The method consists of three main fabrication steps: (1) Direct write the micrometric PCL 2D or 3D pattern by the near-field melt-electrospinning. (2) Cast the PDMS on the printed PCL pattern. (3) Completely remove the embedded sacrificial PCL layer by soaking and flushing with acetone. Uniformity of the morphology of the micro channels and well-alignment could be easily achieved due to include the dimensions achievable using this method. We have also designed and fabricated a few micro fluidic channels. SEM and white-light interferometer images were taken to illustrate the characters of essential parts. This work demonstrated the potential utilization of this technique.
Abstract: Polymer membranes with fixed pore size or narrow pore size distribution can be used for special separation. However, polymer membranes prepared by conventional method usually have wide pore size distribution and the pore size is hard to control. Here we prepared a porous polymer membrane with uniform pore size via spraying a blend of polystyrene (PS) and polyethylene oxide (PEO) on a filtration paper. Dissolving the water-soluble component (PEO) forms the pore and varying the ratios of PEO in the blend controls the pore size. The pore size and size distribution are also affected by processing parameters, such as the flow rate of solution and carrier gas, and gap length. The morphologies of the membrane are observed using scanning electron microscopy (SEM). The novel polymer membrane with controllable and uniform pore size will be used for the separation of solutes with predictable sizes.
Abstract: PVDF-HFP nanofibers are reinforced by (0, 10, 16 and 30wt% ) of butadiene rubber (BR) and are crosslinked by the UV curing during the electrospinning process. These electrospun clothes are soaked with 70wt% uptake of EMI-Tf ionic liquid for solid state electrolytes applications. These electrolytes are investigated by a broadband dielectric spectroscopy over a wide temperature range from-40 to 80 OC. It is found that the temperature dependence of conductivity of all the samples not only follow the VFT relation but also follow the Debye-Stokes-Einstein relation implying the coupling between the ionic conduction and the segmental motion of the polymer matrix. Also, the results indicated that the addition of butadiene rubber did not significantly affect the conduction behavior of the electrolyte. Moreover, the conductivity of all the electrospun cloth electrolytes is much higher than that of the solution casting film.
Abstract: Denture stomatitis is a common clinical disorder seen among denture wearers. Candida albicans is considered to be the major cause which can adhere to and colonize the surface of denture base material made of polymethyl methacrylate (PMMA) resin. This study aims to investigate the effect of vanillin-coated PMMA resin on the adhesion of C. albicans. Heat-polymerized PMMA resin (Vertex RS, Dentimex, Netherlands) samples were prepared and coated with vanillin at various concentrations of 7, 11, and 15 mM. Sterile distilled water and 0.2% chlorhexidine gluconate solution were used to coat the surfaces in negative and positive controls, respectively. The adhesion assay was performed with 3 strains of C. albicans based on the method described by Samaranayake and MacFarlane. The numbers of adherent yeast cells on PMMA resin surfaces were counted under microscope by random selection of 20 fields at 400x magnification. It was found that all vanillin-coated PMMA resin samples had significant decrease of candida adhesion (50-90% reduction) compared to the negative control. The effect was observed to be in a dose dependent manner (p<0.05). Chlorhexidine exhibited strong reduction effect (96-98% reduction). In conclusion, coating PMMA resin with 7-15 mM vanillin can inhibit candida adhesion to the surface. With further testing and development, vanillin may be used as coating agent for denture to prevent candida adhesion and reduce risk of denture stomatitis.
Abstract: Vanillin is a major constituent of vanilla seeds which is used as a flavoring agent in both food and non-food industries. Previous reports have showed that vanillin had antimicrobial properties against food spoilage bacteria, yeasts, and molds. However, investigations about its effect on oral pathogenic yeasts are scarcely found. Objective: This study aims to determine the effect of vanillin on candida biofilm formation in vitro. Method: Vanillin (Sigma-Aldrich, UK) was prepared in 99.7% ethyl alcohol and diluted to concentrations of 0.5-20 mM. Biofilms of Candida albicans (ATCC 10231 and 2 clinical strains) were grown on the bottom of 96-well plate with Yeast Nitrogen Base (YNB) medium supplemented with 100 mM glucose in a shaking incubator at 37oC for 24 h. After washing, each concentration of vanillin was added with YNB supplemented with 200 mM glucose. The plate was incubated in shaking incubator for another 24 h at 37oC. Evaluation of biofilm was assessed through the XTT reduction assay. A solution of 0.2% chlorhexidine gluconate solution and 99.7% ethyl alcohol were used as positive and negative controls respectively. Result: It was found that 75-80% candida biofilm reduction was demonstrated at concentrations of 10.5-20 mM vanillin whereas chlorhexidine exhibited 94% biofilm reduction. Conclusion: Our results indicate that vanillin is a promising agent that can be used to cure candida infection in the oral cavity. Further studies are required to evaluate its effect on other yeast strains and cytotoxicity before consideration for usage in patients.