Papers by Keyword: Thermal Stability

Abstract: Various modes of severe plastic deformation (SPD), such as high-pressure torsion (HPT) at cryogenic temperature, equal channel angular pressing (ECAP) and dynamic channel-angular pressing (DCAP), have been applied for nanostructuring of Ni, and the thermal stability of the structure obtained has been studied. The nanocrystalline structure with average grain sizes of 80 nm and the microhardness of 6200 MPa is produced by HPT in liquid nitrogen. DCAP and ECAP result in the submicrocrystalline structure of a mixed type, with ultra-fine grains separated by high-angle boundaries along with deformation bands and coarse cells with low-angle dislocation boundaries. The thermal stability of the structures obtained by ECAP and DCAP is approximately the same, and it is higher than after the HPT at cryogenic temperature.

Abstract: The Al-Cu-Mg alloys currently used at elevated temperature for aerospace applications, such as 2618 and 2219, were developed in the 1950s. Since then, not only have property requirements evolved significantly with the widespread introduction of damage tolerant design, but also the understanding and modelling capacity of the alloys' property-composition-processing relationships have developed beyond recognition. Moreover there is a renewed need for higher strength/toughness, higher temperature solutions in many aircraft's hot areas.A kinetic model has been developed to predict the strengthening capability and the thermal stability of hardening phases. It is based on a homogeneous nucleation, growth and coarsening model applied to S' (Al₂CuMg) and θ' (Al₂Cu); the yield strength is then calculated from the precipitates' size distribution. It suggests two areas of interest in the Al-Cu-Mg diagram.Three targeted compositions were then explored inside and outside the areas of interest and their thermal stability assessed up to 250°C. Different behaviours were observed and are explained by the strengthening potential and the coarsening resistance of S' and θ'. The two interesting areas for thermally stability are confirmed. An area of poorer thermal stability was also identified, associated with a high Cu content in solid solution which accelerates precipitate coarsening kinetics.

Abstract: Glass forming ability and crystallization kinetics of Al-Mg-Ni-La alloys have been investigated by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The maximum thickness achievable in glasses of Al₇₆Mg₁₁Ni₈La₅ and Al₆₉Mg₁₈Ni₈La₅ ribbons were 200 and 120 μm, respectively. The crystallization temperature and peak temperature indicated by DSC measurements displayed dependence on the heating rate during continuous heating, and were coincident with Lanoka’s relationship. The activation energies for the crystallization reaction E_x were obtained from the Kissinger’s equation. The results show the Mg addition is beneficial to the thermal stability of the amorphous phase.

Abstract: Sawdust/poly (lactic acid) (PLA) composites toughened with poly (butylene adipate-co-terephthalate) (PBAT) were prepared using a melt blending process. Mechanical, thermal and morphological properties of the composites were investigated. With the addition of PBAT into the sawdust/PLA composite, elongation at break and impact strength increased whereas tensile strength and tensile modulus decreased. In addition, thermal stability of the PLA composite improved with the presence of PBAT. Maleic anhydride grafted poly (lactic acid) (PLA-g-MA) was used as a compatibilizer to improve the compatibility of sawdust/PLA/PBAT composites. The compatibilized composites showed higher mechanical properties and thermal decomposition temperatures than that of the uncompatibilized composite due to improved interfacial adhesion between constituents of the composites. The optimum content of PLA-g-MA for sawdust/PLA/PBAT composites was 5 wt%. SEM micrographs revealed some features of ductile fracture in the composites toughened with PBAT and confirmed that PLA-g-MA improved the compatibility of the composites.

Abstract: Use polyurethane rubber composite modified asphalt.Through the Marshall test and rutting test, test of polyurethane rubber asphalt mixture high temperature stability, low temperature crack resistance and water damage resistance, verify the composite modification advantages.

Abstract: Polypropylene (PP)/Maleic anhydride grafted poly (ethylene-octene) (POEg) were prepared by melt blending method. The crystallization behavior and crystal morphology were studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarzing optical microscope (POM). Differential scanning colorimetry (DSC) experiments showed that the melting point and crystallization point decreased when POEg added to the blend. XRD results show that the POEg not change the crystal structure in the blends but only decrease the intensity of the diffraction peak. The spherulitic structure could also observed when added POEg to the matix of PP, but the shape of the spherulites distorted.

Abstract: A novel cement fluid loss additive P1402, which synthesized using the monomers of 2-acrylamido-2-methyl-propane sulphonic acid (AMPS), acrylic acid (AA), N,N dimethyl acrylamide (DMAM) and N-Vinyl-2-pyrrolidone (NVP) by the method of aqueous solution polymerization. The ratio of monomers AMPS:AA:DMAM:NVP at 2:1.5:1:1, reaction PH at 10.8, reaction temperature at 65°Cand reaction time about 5 hours. The IR spectrum of P1402 show that the polymer with the structure of all the monomers .The fluid loss performance testing show that the forpolymers P1402 has an excellent thermal stability. The fluid loss additive P1402 has an excellent tolerance to salt and high temperature.

Abstract: In present study drilling as a new Surface Sever Plastic Deformation technique (SSPD) has been applied to commercial CK60 steel plate to create a nanoCrystalline (NC) structured layer.The CK60 steel plate with tempered martensitic crystalline structure has been drilledusing hard titanium coated drilling bit under 20 m/min cutting speed. The formed surface nanocrystalline (NC) layers characterized by using field emission scanning electron microscope (FESEM) and microhardness tests. The results showed that the hardness of formed NC layer with almost 50nm grain sizes was more than twice of the martensitic base metal hardness. The thermal stability of NC layer has been studied in the range of 673 to 923K and the results showed that created fine grain structurehad higher thermal stabilitycompared to CK60 steel samples with coarse granular crystalline structure. The microhardness of NC layers reduced from 9.8 to 9.1 GPa after 1 hour tempering at923K.

Abstract: Thermal stability of total anthocyanin contents of an anthocyanin complex (AC) formed by extracts of Z. mays L. ceritina Kulesh (CC) and Clitoria ternatea L. (CT) at pH 5.5 was investigated by pH differential method. The AC shifted FTIR spectra of CC and CT from about 1,600 to 1,732 cm^-1 and about 1,000 to 1,106 cm^-1. Temperature-dependent degradation rates of AC of 0.4, 1.4 and 8.5 %h^-1 were determined upon storage at 50, 70 and 90°C, respectively. The degradation rates of total anthocyanins of AC were about 2 times lowered than those of CC and CT. Arrhenius plots of the AC showed a change in activation energy from those of the CT and CC extracts. The AC increased the microscopic dark areas of the white hair from 2% to about 65%. It leads to conclude that complexation of anthocyanins from 2 sources into the AC reduced degradation of the anthocyanins and mpotential hair dye.

Abstract: A dedicated experimental setup has been designed and built up for determining the reproducibility of a 1-DOF moving-scale measurement system. A 3-DOF moving-scale system would enable the measurement of the position of a workpiece table moving in three perpendicular directions with minimized Abbe-offset. This allows normal machine tools and CMMs to match or even surpass the accuracy of ultra-precision machines. An uncertainty budget indicates that the 1-DOF moving-scale system can obtain a measurement uncertainty of 18 nm. Thermal drift is the largest contribution to the measurement uncertainty and should be accurately determined.