摘要: Polypropylene (PP), a versatile polymer finds application in many sectors. However, it has low impact strength.To overcome this draw back elastomer is added, which results in improved impact property at the expense of decreased tensile strength. To improve this fillers are added. However some fillers also improve impact strength. In this work only fillers have been used to get balance of properties in PP. Knowledge of crystallization of PP is important for processing of PP. In this work the effect of hybrid fillers on PP has been studied on the isothermal and non-isothermal crystallization kinetics of PP. The fillers used are coir and talc.
摘要: This work aims to investigate the effect of SiC addition on structural, microstructural and mechanical properties of developed Al-Sic nanocomposites. Al metal matrix composites reinforced by nanosized SiC particles were fabricated using high energy ball milling and microwave sintering process followed by hot extrusion. The XRD analysis indicated that the dominant components were Al and SiC. SEM/EDX micrographs showed homogenous distribution of SiC nanoparticles in Al matrix. Mechanical characterizations revealed that the addition of nanosize SiC particulates to a simultaneous increase in microhardnes, yield strength, ultimate compressive/tensile strength and reduction in ductility of the matrix. This improvement in mechanical properties can be attributed to the homogeneous distribution of reinforcement (SiC particles) and dispersion strengthening mechanism.
摘要: Aluminium reinforced with different volume fractions of milled carbon fibres (MCFs) were manufactured via advanced powder metallurgy processing method. Composites containing 5, 10, 15 and 20 % volume fraction of MCFs were prepared using the Uniball magneto milling technique. Full density cylindrical compacts were produced by uniaxial hot pressing (UHP) at 600°C for a dwelling time close to 15 minutes. Characterization was done using x-ray diffractometry (XRD) and Field Emission Scanning Electron Microscopy (FSEM). The mechanical and physical properties were determined by compression testing, Vickers hardness, and Archimedes density. Unniball milling of blends resulted in decrease of aspect ratio of the MCFs and refinement of the Al grain size. Results show slight uniform distribution of MCFs in Al matrix for higher volume fractions without discernible porosity. In samples containing low volume fractions of MCFs (5% and 10%) fibres tended to be pushed towards grain boundaries during grain growth. In samples with higher volume fraction of MCFs (15 and 20% a more uniform distribution of MCFs in the product was obtained. The compressive strength of the composites was enhanced by the fibres, attributable to good interface bonding and wetting between the matrix and the reinforcement fibres. The combination of controlled ball milling and UHP techniques has facilitated the development of Al-MCFs composites potentially to be used in automobile industries.
摘要: In this study 1% Ag (silver), Cu (copper), CNT (carbon nanotube) and graphene nanoribbon (GNR) nanoparticle reinforced PAN fibers were prepared and the effects of nanoparticle reinforcements upon electrical conductivity were investigated. In experimental study, graphene nanoribbon powders were produced from multiwalled carbon nanotube (MWCNT) through using the chemical approach of Hummers method. Fiber layer was dissolved at room temperature in magnetic mixer with Polyacrylonitrile (PAN) and Dimethil Formamide (DMF) which was at the rate of 10 % by mass. Thus, a viscou gel solution was obtained then nanoparticles were added to the PAN/DMF solution and the solution was vigorously stirred for one hour at room temperature. After stirring that solution was continued for 15 m in ultrasonic bath. The polymeric solution was first transferred to a 5 mL syringe, which was connected to a capillary needle with an inside diameter of 0,8 mm. A copper electrode was attached to the needle, a DC power supply produces 25 kV against a grounded collector screen distant 15cm. With the syringe pump set at 2 mL/h, the electric force overcomes the surface tension of the solution at the capillary tip, and a jet emerges. Produced fibers were collected on the rotary collector which spins at 250 rpm. Nanofiber was dried at 60 °C for 12 h in vacuum oven. Eventually, nanofiber of polyacrylonitrile (PAN) reinforced by metallic nanoparticles and graphene nanoribbon (GNR) were prepared by electro spinning process. Electrical conductivity of the obtained nanofiber were studied by measuring the electrical resistance thanks to home-made plate electrodes.
摘要: In the present paper aluminum matrix composites were fabricated using base material AA6082-T6. SiC and B4C particulates were used as reinforcement to obtain hybrid and non-hybrid composites through the conventional stir casting process. AA6082-T6/SiC composites with 5, 10, 15 and 20 wt % of SiC; AA6082-T6/B4C composites with 5, 10, 15 and 20 wt % of B4C and AA6082-T6/(SiC+B4C) hybrid composites with 5, 10, 15 and 20 wt % of (SiC+B4C) taking equal fraction of SiC and B4C were made and the microstructure study was carried out. X-Ray diffraction (XRD) patterns revels the presence of reinforcement within the matrix along with some other compounds. The microstructure of the fabricated composites was examined with the help of Scanning electron microscope (SEM) and the micrographs revealed that the dispersion of reinforced particles was reasonably uniform at all weight percentages.
摘要: The microstructural properties and intermetallic (IMC) formation of Sn-Ag-Cu (SAC) through varying amounts of zinc were examined in this study while having tin held at constant composition. Samples were prepared and heated in a furnace for 168 hours to achieve complete solidification and homogenization. Results showed relatively fine microstructure primarily containing Sn dendrites, eutectic, and pro-eutectic phases. Microstructures for each alloy was similar for which majority of them formed copper-based IMCs and Sn dendrites. The alloy (0.7Sn-0.15Ag-0.1Cu-0.05Zn) containing minimal amount of zinc with high amount of Ag resulted to high Vickers hardness number. Structural analysis showed that these group of alloys composed mainly of β-Sn, Cu6Sn5, and Ag3Sn.
摘要: The pack-cementation is one of economical, efficient coating processes for Fe-base alloys. It can provide good protection against high-temperature oxidation and corrosion. In this study, the high-temperature corrosion behavior of the aluminized diffusion-coating on low-carbon T20 steel (Fe-2.0Cr-0.5Mo-0.8Mn-0.3S in at.%) was studied at 800 °C in N2/H2O/H2S-mixed gas. The aluminized coating consisted of Fe3Al. The aluminized T20 steel after corrosion at 800 °C for 10~100h in N2/H2O/H2S-mixed gases, the scale formed on the Fe3Al coating consisted primarily of α-Al2O3, Al2S3, FeAl2O4 and FeO, with relatively slow scaling rates. The Fe3Al intermetallics has reasonable corrosion-and oxidation-resistance, because it can form a protective alumina scale. Without the aluminized diffusion-coating, T20 steel corroded fast with serious scale failure. At the surface, coarse FeS grains with cracks formed. Since FeS has a very high concentration of cation vacancies, it grew fast through the outward diffusion of Fe2+ ions.
摘要: The size of equipments now a day reduced to microns and nanos. So, the wear characteristics play a dominating role in the proper working of equipments utilized in engineering and medical fields. NiTi alloys have different applications in medical and engineering field due to their unique characteristics of super-elasticity, corrosion resistance, shape memory and bio-compatibility. In the present research, Ni50Ti50 alloy have been fabricated by powder metallurgy method with polypropylene as a binder. During sintering process at 1150°C, organic binder evaporates and makes the alloy porous. The surface of NiTi alloy is covered by TiO2 layer, which increases its wear resistance, but with the increase of frictional heat (produced due to pin on disc apparatus experimentation) this layer, breaks and wear rate increases. The mean value of wear loss was investigated at 95% of confidence level and further experiments were performed to validate the predicted value.
摘要: We present results of defect formation energies and charge state thermodynamic transition levels of Mg and Te interstitials in MgTe wurzite structure. We use the generalized gradient approximation and local density approximation functionals in the framework of density functional theory for all calculations. The formation energies of the Mg and Te interstitials in MgTe for both the tetrahedral and hexagonal configurations were obtained. The Mg and Te interstitials in MgTe depending on the functional, introduced transition state levels that are either donor or acceptor within the band gap of the MgTe. The Te interstitial exhibit charge states controlled metastability, negative-U and DX centre properties. The Mg interstitial acts as deep or shallow donor and there is no evidence of acceptor levels found for the Mg interstitial.