The martensitic transformation plasticity and effect of stress on the martensitic transformation kinetics were investigated by means of dilatometric experiments under different applied tensile and compressive stress on Cr5 steel used for backup rolls. Results show that the martensitic transformation coefficient α of Cr5 steel is almost the same under different stress, in other word, the influence of stress is negligible; Besides, the martensitic transformation coefficient α decreases with the increasing temperature, the relation of which with temperature can be described approximately as a cubic polynomial. The martensite transformation point (MS) increases with the increasing equivalent stress. The k-values of transformation plasticity coefficient under different stress may be acquired as ca 4.32×10-5 according to the Greenwood-Johnson equation.
Cathode materials of LiNi0.5Mn0.5-xCoxO2(0<x≤0.12) were synthesized via simple co-precipitation and high-temperature solid-state reaction processes. The prepared materials were characterized by SEM, XRD, EDS and XPS. Their electrochemical performance was examined by galvanostatic charge-discharge tests, electrochemical impedance spectroscopy. Results show that all of the doped samples have a typical α-NaFeO2 layered structure with partial substitution of Co-atom for Mn-atom in the crystal lattice. XPS analysis showed that there is oxygen deficiency in the doped materials and the valence states of Ni, Mn and Co were mainly +2, +4 and +3, respectively. It has been found that the Co-doped LiNi0.5Mn0.5O2 shows better cycling stability, rate capacity and low-temperature property than LiNi0.5Mn0.5O2 without Co doping. For cycled at 25oC in the voltage range of 2.75~4.35 V, the LiNi0.5Mn0.5-xCo0.12O2 delivered initial discharge specific capacity of 180.8 mAh·g-1 and kept capacity retention rate of 92.3% after 100 cycles. The discharge specific capacity for the corresponding electrode cycled at -20oC is about 66.3% of its initial discharge specific capacity cycled at 25oC.
Carbon nanotubes (CNTs)-grafted carbon fibers, which can significantly improve the tensile strength of carbon fibers, were successfully prepared via chemical vapor deposition (CVD) process. It was found that the metal catalyst composition had a little influence on the morphology of catalyst particles and tensile strength of carbon fibers after the reduction of catalyst precursor, but significantly affected the growth rate of CNTs and the corresponding tensile strength of CNT-grafted carbon fibers. High catalyst activity not only contributes to the high-efficiency for the synthesis of CNTs, but also facilitate the healing of damages on surface and strengthening of carbon fibers. Fe-Cu and Ni-Cu catalysts were found to be high efficient catalyst for CNTs growth. Therewith, the tensile strength of the CNTs grafted carbon fiber prepared in the presence of catalysts of Fe-Cu and Ni-Cu increased by 12.26% and 12.80% respectively.
Composite coatings of double-layered Al2O3/PTFE and single-layered Al2O3-PTFE were prepared via atmospheric plasma spraying (APS) process. The morphology, phase composition, roughness, hardness, hydrophobic property and wear resistance of the composite coatings were characterized by scanning electron microscope (SEM), 3D topography tester, micro-hardness tester, contact angle tester and friction and wear tester respectively. The influence of Al2O3 bond coat, Al2O3 hard particle filling and different process parameters on the hydrophobic property and wear resistance of the composite coatings were assessed. Results show that the wear resistance of the single PTFE coating were improved significantly by inducing Al2O3 ceramic as a bond coat or as hard particle filling phase into the composite coatings; The wear resistance property of Al2O3-PTFE composite coatings was superior to that of the Al2O3/PTFE composite coatings, correspondingly the wear rate of which was 2.84×10-5 mm3/N·m and 9.97×10-5 mm3/N·m respectively, the friction coefficient is 0.51 and 0.38 respectively; While the surface of the two composite coatings showed good hydrophobic properties with static contact angle of 155.4° and 148.9° respectively, which may be attributed to the compacted micro-nano convex structure on the rough surface and the synergistic effect of fluoride with low surface energy distributed on the composite coating surface. After the friction and wear test, the surface structure of the two composite coatings was damaged, hence the hydrophobicity of the coatings degraded, even so, the Al2O3/PTFE composite coating still exhibits super-hydrophobicity.
Microstructure and characterization of hydrothermally synthesized fly ash-based tobermorite doped with Al (FA-T) was investigated in comparison with the counterpart of hydrothermal product (T-A) synthesized from pure reagents. The results show that the interplanar spacing of (002) plane of FA-T was larger than that of T-A, correspondingly the ratio of Ca/(Si+Al) increased and the Si-content reduced. Because certain part of the doped Al was involved in the reconstruction of tobermorite structure and the rest part of Al existed in interlamellar spaces of the tobermorite structure . The wave-numbers of two absorption peaks, which belong to the bending vibration of Si-O (Q1) and Si-O-Si for FA-T, were larger than those for T-A. These mean that the chains of [SiO4]4- for FA-T were shorter than those for T-A, and the degree of polymerization of FA-T was poor. The SEM results reveal that the T-A presents as thin foils, whilst the FA-T as spherical particles wound with fibrous and lamellar tobermorite.
A new type of polymer alloy of polypropylene/polybutene-1 was prepared by in-situ polymerization with spherical Ziegler-Natta as catalyst. The effect of butene-1 addition on the morphology, structure and the properties of polymer alloy was investigated. The polymers obtained were characterized by means of DSC, SEM XRD and 13C NMR. The results show that compared with the bulk polymerization of butene-1, the in-situ polymerization could improve the morphology of the product made from polybutene-1, and effectively reduce the adhesion between polymer particles. The catalytic activity, stacking density and particle size of the prepared polymer alloy are 10.4 kg/gCat, 0.44 g/cm3 and 500 μm, respectively. Moreover, the in-situ polymerization could effectively shorten the transition period of the polybutene-1 product from the unstable crystal form II to the stable crystalline form I. The mechanical property test revealed that with the rise of the content of the structural unit in propylene the tensile strength and flexural modulus of the polybutene alloys were increased, however, the density, impact strength and elongation at break were decreased.
In order to investigate the isothermal oxidation performance of CoCrAlY coatings prepared by EB-PVD after high energy shot peening process with different intensity, the CoCrAlY coatings on high temperature alloy DZ466 were surface shot peened with intensity of 0.1 N, 0.2 N, 0.3 N and 0.45 N. The shot peened coatings were characterized in terms of surface morphology, surface roughness, surface residual stress, thickness and cross-sectional hardness and phase composition, as well as isothermal oxidation behavior in air at 1050℃. Results show that the isothermal oxidation resistance of CoCrAlY coating prepared by EB-PVD is greatly improved after surface shot peening with intensity of 0.1 N. When the shot peening intensity is greater than or equal to 0.45 N, the coating is damaged, which degrades the isothermal oxidation performance of the CoCrAlY coating. The suitable shot peening intensity can decrease the surface roughness, whilst increase the density and change the phase composition of the CoCrAlY coating, and so that lead to the improvement of isothermal oxidation performance of the CoCrAlY coating. When the shot peening intensity is greater than or equal to 0.3 N, scale-shaped bulges formed on the surface of CoCrAlY coating, resulting in preferential growth of Al-oxide there. Because of the rupture of Al-oxide film induced by stress concentration in this place, the service life of coating is degraded.
Hydrogen permeation and embitterment behavior of hot-dip galvanized steel with different amount of sulphite deposits on surface exposed to stimulant marine atmospheric environment was investigated. The hydrogen embrittlement susceptivity of the steel in this environment was assessed through measuring the hydrogen permeation current by an improved Devanathan-Stachurski cell and the elongation of the galvanized steel at break, while observing the morphology of the fractured surface. Results indicated that the hydrogen permeation current gradually increased with the increasing amount of deposits. On the other hand, it was found that hydrogen absorption was accelerated by the synergistic effect of cathodic protection and the existed damage of zinc coating induced by scratching. The adsorbed hydrogen can reduce the elongation of the steel at break. This means that sulphite can reduce the toughness of hot-dip galvanized steel, resulting in hydrogen damage.
The effect of pre-aging processes on superplasticity and microstructure of TB8 Ti-alloy was investigated. Results show that after pre-aging at 520oC for 1 h, the superplasticity of the alloy can be the best, and the elongation is up to 362%, increased by 1.65 fold of that for the counterpart alloy; A certain amount of fine α phase precipitated at grain boundaries and in grains of the metastable β-phase after pre-aging; During the deformation process, the precipitated α phase can restrain the growth of recrystallization grains and break the dissolution phase structure, so that induce grain refinement and increase the superplasticity of TB8 alloy. In case of pre-aging at a desired pre-aging temperature, the grain size of the fractured surface decreases first and then increases with the increasing aging time, while the grain size is the smallest and the elongation is the highest by pre-aging for 1 h. In case of pre-aging for a desired period of time, the alloy aged at 520oC presents the highest elongation at break with the most uniform fracture microstructure.
Poly(lactic acid)/epoxy furan resin/poly (butylene succinate) (PLA/FER/PBS) blends with different epoxy furan resin (FER) content were prepared by melt blending, while the effect of FER content on the dynamic rheological behavior and compatibility of the PLA/PBS blends was investigated by means of rotary rheometer, scanning electron microscopy (SEM) and universal testing machine. Results show that when the strain (γ) is less than 10%, the dynamic modulus does not change with the change of γ and the blends show linear viscoelastic behavior; when γ is more than 10%, the dynamic modulus decrease obviously, showing the "Payne" effect; FER can improve the processing properties of PLA/PBS blends;PLA/PBS blends have two different relaxation processes, the relevant curves have two distinct half arc, PLA and PBS phase morphology changed with the addition of FER; the time- and temperature-superposition-curves show that for PLA/PBS blends with FER content of 0.3 phr, of which, the Han-curves and vGP-curves of the blends present good overlap, implying the compatibility between PLA and PBS is good; the interface adhesion between PLA and PBS is the best, and the PLA and PBS has the most ideal interfacial compatibility; the tensile strength and impact strength of the blends reached the maximum value of 56.9 MPa and 4.33 kJ/m2, which is 11.2% and 37% higher than that of the simple PLA/PBS blends, respectively.
One-dimensional α-AgVO3 nanostructures were synthesized at ambient temperature via in-situ reaction process using one-dimensional K2V6O16·1.5H2O as precursor template. Then one-dimensional β-AgVO3 nanostructures were obtained through heat-treatment of the α-AgVO3 nanostructures at 300℃ for 3 h. The as-prepared α-AgVO3 and β-AgVO3 nanostructures were characterized by means of X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS). Results of the electrochemical tests show that the β-AgVO3 nanostructures possess better rate capability and cycling performance, as well as smaller charge transfer and lithium ion transport resistance rather than that of the α-AgVO3 nanostructures.
