Influence of high-intensity ultrasonic treatment on the phase morphology of a Mg-9.0wt.%Al binary alloy

The effect of ultrasonic treatment on the β-phase （Mg17Al12） morphology of an Mg-9.0wt.%Al alloy was studied. The result shows that with high-intensity ultrasonic vibration employed during the solidifying of Mg-9.0wt.%Al, the β-phase in the entire cross section of the billet is significantly refined and also changed from continuous to discontinuous morphology. Spherical β-phase is formed during the solidification of the billet treated with high-intensity ultrasonic vibration.

EFFECT OF COMPATIBILITY ON PHASE MORPHOLOGY AND ORIENTATION OF ISOTACTIC POLYPROPYLENE (IPP) BLENDS OBTAINED BY DYNAMIC PACKING INJECTION MOLDING

The effect of compatibility on phase morphology and orientation of isotactic polypropylene （iPP） blends under shear stress was investigated via dynamic packing injection molding （DPIM）. The compatibility of iPP blended with other polymers, namely, atactic polypropylene （aPP）, octane-ethylene copolymer （POE）, ethylene-propylene-diene rubber （EPDM） and poly（ethylene-co-vinyl acetate） （EVA）, have first been studied using dynamic mechanical analysis （DMA）. These blends were subjected to DPIM, which relies on the application of shear stress fields to the melt/solid interfaces during the packing stage by means of hydraulically actuated pistons. The phase morphology, orientation and mechanical properties of the injection-molded samples were characterized by SEM, 2D WAXS and Instron. For incompatible iPP/EVA blends, a much elongated and deformed EVA particles and a higher degree of iPP chain orientation were observed under the effect of shear. However, for compatible iPP/aPP blends, a less deformed and elongated aPP particles and less oriented iPP chains were deduced. It can be concluded that the compatibility between the components decreases the deformation and orientation in the polymer blends. This is most likely due to the hindering effect, resulting from the molecular entanglement and interaction in the compatible system.

Research on fractal characteristics of primary phase morphology in semi-solid A356 alloy

Semi-solid slurry of A356 alloy was prepared by low superheat pouring and slightly electromagnetic stirring, and the fractal characteristics of morphology in semi-solid primary phase was researched. The fractal dimensions of primary phase morphology in the semi-solid A356 alloy were calculated by the program written to calculate the fractal dimensions of box-counting in the image of solid phase morphology in semi-solid metal slurry. The results indicated that the morphology of primary phase in semi-solid A356 prepared by low superheat pouring and slightly electromagnetic stirring is characterized by fractal dimension, and the primary phase morphology obtained by the different processing parameters has different fractal dimensions. The morphology of primary phase at the different position of ingot has different fractal dimensions, which reflected the effect of solidified conditions at different positions in the same ingot on the morphology of semi-solid primary phase. Solidification of semi-solid alloy is a course of change in fractal dimension.

Phase Morphology Evolution in AISI301 Austenite Stainless Steel under Different Cooling Rates

Quenching experiments were performed at different cooling rates under non-directional solidification by differential thermal analysis, and the morphologic variation of primary phase, phase transition temperature and hardness change at the same quenching temperature were investigated. The experimental results show that, with the gradual decrease of the cooling rate from 25 K/min, the morphology of ferrite starts to transform experiencing the dendrite, radial pattern, Widmanstatten-like and wire-net. Sample starts to present the Widmanstatten-like microstructure at 10 K/min which does not exist at higher or lower cooling rates, and this microstructure is detrimental to the mechanical property. Except 10 K/min, the hardness decreases with decreasing cooling rate.

A Robust Self-healing Polyurethane Elastomer Enabled by Tuning the Molecular Mobility and Phase Morphology through Disulfide Bonds

Elastomers with outstanding strength,toughness and healing efficiency are highly promising for many emerging fields.However,it is still a challenge to integrate all these beneficial features in one elastomer.Herein,an asymmetric alicyclic structure adjacent to aromatic disulfide was tactfully introduced into the backbone of polyurethane(PU)elastomer.Specifically,such elastomer(PU-HPS)was fabricated by polycondensing polytetramethylene ether glycol(PTMEG),isophorone diisocyanate(IPDI)and p-hydroxydiphenyl disulfide(HPS)via one-pot method.The molecular mobility and phase morphology of PU-HPS can be tuned by adjusting the HPS content.Consequently,the dynamic exchange of hydrogen and disulfide bonds in the hard segment domains can also be tailored.The optimized sample manifests outstanding tensile strength(46.4 MPa),high toughness(109.1 MJ/m^(3)),high self-healing efficiency after fracture(90.3%),complete scratch recovery(100%)and good puncture resistance.Therefore,this work provides a facile strategy for developing robust self-healing polymers.

INFLUENCE OF SHEARING ON IMPACT POLYPROPYLENE COPOLYMER:PHASE MORPHOLOGY,THERMAL AND RHEOLOGICAL BEHAVIOR

The influences of shearing conducted by a Brabender behavior of a commercial impact polypropylene copolymer （IPC） rheometer on phase morphology, thermal and rheological were studied. The crystallization and melting traces show that short-time annealing at 210℃ is unable to completely erase the influence of shearing on the samples. When the samples which were treated at a rotation speed of 80 r/rnin crystallize at a cooling rate of 10 K/min, their Tcs and corresponding Tms obviously rise with the increase of shearing time. Furthermore, the POM results reveal that the shearing can lead to the formation of shish-kebab and the shish-kebab amount is proportional to shearing time. The rheological measurement results show that the treated samples exhibit different G＇-ω dependences. The ＇second plateau＇ appears when the sample is treated at a rotation speed of 60 r/min or 80 r/min for 10 min, and linear G＇-ω dependence is observed at other rotation speeds. In addition, it is found that the appearance of the ＇second plateau＇ depends on the shearing time when the rotation speed is fixed. According to SEM observations, it is proposed that the ＇second plateau＇ of IPC samples should be ascribed to the aggregation of dispersion particles.

Phase Morphology, Crystallization Behavior and Mechanical Properties of Poly(L-lactide) Toughened with Biodegradable Polyurethane: Effect of Composition and Hard Segment Ratio

Polyester-based biodegradable polyurethane （PU） with different hard segment ratios was selected to modify the impact toughness of poly（L-lactide） （PLLA）. The influence of blending composition and hard segment ratio of PU on the phase morphology, crystallization behavior and mechanical properties of PLLA/PU blends has been investigated systematically. The results showed that the PU particles were uniformly dispersed in PLLA matrix at a scale from sub- microns to several microns. The glass transition temperature of PU within these blends decreased compared to that of neat PU, but rose slightly with its content and hard segment ratio. The presence of PU retarded the crystallization ability of PLLA, whereas enhanced its elongation at break and impact resistance effectively. As the PU content reaches up to 30 wt%, the phenomenon of brittle-ductile transition occurred, resulting in a rougher fracture surface with the formation of fibril-like structure. Moreover, under the same concentrations, the elongation at break and impact strength of PLLA blends decreased slightly with the increase of hard segment ratio of PU.

Cellulose Nanocrystals-mediated Phase Morphology of PLLA/TPU Blends for 3D Printing

Incorporation of nanoparticles into polymer blend to obtain finely dispersed morphology has been considered as an effective strategy to prepare nanocomposites. Owing to the renewable and degradable characters, cellulose nanocrystals(CNCs) have been proposed to tailor the phase morphology of poly(L-lactic acid)(PLLA) blend for producing high-performance fused deposition modeling(FDM) consumables. However,the main challenge associated with the ternary systems is the dispersion of the highly hydrophilic CNCs in non-polar PLLA blend by industrial melt blending without involving solution. Herein, with poly(vinyl acetate)(PVAc) modified CNCs powder(a mixture of PVAc grafted from CNCs and PVAc homopolymer latex), the selective dispersion of CNCs in PLLA has been achieved by simple melt processing of PLLA/TPU(polyether polyurethane)/CNCs blend. This results in the ultra-fine TPU droplets at nanoscale in PLLA and improves the melt processibility of composites in FDM due to the decreased viscosity ratio of the dispersed/matrix and the enhanced melt elasticity of PLLA. Combined with the intensive shear and continuous stretch effect during FDM, aligned TPU nanofibers(TNFs) were in situ formed along the elongational flow direction during deposition, which in turn contributed to the improvement of PLLA/TPU/CNCs with 5 wt% filler loading in tensile ductility by 418%, inter-layer adhesion strength and notched impact toughness by 261% and 210%, respectively, as well as achieved good dimensional accuracy and very fine surface quality.

Study of Thermal,Phase Morphological and Mechanical Properties of Poly(L-lactide)-b-Poly(ethylene glycol)-b-Poly(L-lactide)/Poly(ethylene glycol)Blend Bioplastics

A poly(L-lactide)-b-poly(ethylene glycol)-b-poly(L-lactide)(PLLA-PEG-PLLA)block copolymer has great potential for use as a flexible bioplastic.Highly flexible bioplastics are required for flexible packaging applications.In this work,a PEG was incorporated into block copolymer as a plasticizer by solvent casting.PLLA-PEG-PLLA/PEG blends with different blend ratios were prepared,and the plasticizing effect and miscibility of PEG in block copolymer were intensively investigated compared to PLLA/PEG blends.The results indicated that the PEG was an effective plasticizer for the block copolymer.The blending of PEG decreased glass-transition temperature and accelerated the crystallization of both the PLLA and PLLA-PEG-PLLA matrices.The PEG was completely miscible when blended with block copolymer and it improved thermal stability of the block copolymer matrix but not of the PLLA matrix.Film extensibility of PLLA-PEG-PLLA/PEG blends steadily increased as the PEG ratio increased.These non-toxic and highly flexible PLLA-PEG-PLLA/PEG bioplastics are promising candidates for several applications such as biomedical devices,tissue scaffolds and packaging materials.

Microstructure and mechanical properties of TC21 titanium alloy by near-isothermal forging

Microstructure and tensile properties of TC21 titanium alloy after near-isothermal forging with different parameters plus solution treatment and aging were investigated. It is found that the residual β matrix, which was strengthened by fine secondary α platelets forming during aging, exists in all the samples; while primary equiaxed α phase, bent lamellar α phase and α plates are simultaneously or individually present in one sample. The strength of alloy increases proportionally with increasing the content of residual β matrix, which is the result of increasing α/β interphase boundary. The plasticity of alloy has a downward trend as the content of residual β matrix increases. This attributes to the increase of fine secondary α platelets, which are cut by dislocations during the deformation. Additionally, coarse α plates with long axis parallel to the maximum resolved shear stress（MRSS） also reduce the plasticity of TC21 alloy.

Synthesis of TiO_2 visible light catalysts with controllable crystalline phase and morphology from Ti-bearing electric arc furnace molten slag

TiO_2 visible light catalysts with different crystalline phases and morphologies were synthesized from titanium-bearing electric arc furnace molten slag（Ti-bearing EAF slag）by using a simple acidolysis process.The effects of the p H of the HCl solution,liquid to solid ratio（RL/S,HCl solution to the residue ratio,m L/g） and acidolysis time on the micro-morphology and crystalline phase of as-prepared TiO_2 photocatalysts were systematically investigated.The results indicated that with decreasing p H in the HCl solution and increasing RL/S,the crystalline phase and micro-morphology of the obtained TiO_2 nanostructures tended to transform from anatase type TiO_2 with spherical nanoparticle structures to rutile type TiO_2 with needle-like nanorod structures.The acidolysis time had little influence on the crystalline phase but great impact on the size of the obtained TiO_2.The growth mechanism of TiO_2 from Ti-bearing EAF slag during the acidolysis process was also discussed.In addition,the influence of RL/Son the photocatalytic properties of the synthesized nanostructured TiO_2 was studied.The results showed that the photodegradation efficiency for Rhodamine B solution could reach 91.00% in 120 min when the RL/Swas controlled at 50：1.

Variant selection of nanocrystalline a phase in metastableβTB8 titanium alloy via electric pulse treatment

In this paper,the metastableβTB8 titanium alloy with nanocrystallineαphase is achieved by electric pulse treatment.The morphology evolution and variant selection of nanocrystallineαphase in metastableβTB8titanium alloy were investigated by using scanning electron microscope(SEM),electron backscattered diffraction(EBSD)and transmission electron microscope(TEM)analysis.The results indicated that the morphologies of the nanocrystallineαphase were mainly triangular clusters and needle-like at the pressure of 0 MPa.With increasing pressure from 20 to 50 MPa,the volume fraction of needlelikeαphase decreased,and a large amount of V-shapedαphase formed in the interior ofβgrains.Based on the EBSD data,the parentβphase was reconstructed by MTEX software.In the interior of theβgrains,12 variants can form for the samples electric pulse treated at 0 and20 MPa,while only 3 and 6 variants can form for the samples electric pulse treated at 30 and 50 MPa.In the grain boundary of theβgrains,one or more grain boundaryαvariants can be generated for the samples electric pulse treated at different pressures as long as one of the neighborβgrains follows the Burgers orientation relationship.

Effects of Annealing Processes on CuxSi(1-x) Thin Films

The CuxSi（1-x） thin films have been grown by pulsed laser deposition（PLD） with in situ annealing on Si（001） and Si（111）,respectively.The transformation of phase was detected by X-ray diffraction（XRD）.The results showed that the as-deposited films were composed of Cu on both Si（001） and Si（111）.The annealed thin films consisted of Cu ＋η ＂-Cu3Si on Si（001） while Cu ＋η＇-Cu3Si on Si（111）,respectively,at annealed temperature（Ta）= 300-600℃.With the further increasing of Ta,at Ta= 700℃,there was only one main phase,η＂-Cu3Si on Si（001） while η＇-Cu3Si on Si（111）,respectively.The annealed thin films transformed from continuous dense structure to scattered-grain morphology with increasing Ta detected by field emission scanning electron microscope（FESEM）.It was also showed that the grain size would enlarge with increasing annealing time（ta）.

Morphology and Mechanical Properties of Immiscible Polyethylene/Polyamide12 Blends Prepared by High Shear Processing

In this work, completely immiscible polyethylene/polyamidel2 （PE/PA12） blends were prepared by high shear extruder. The morphology and mechanical properties of the blends were investigated as a function of rotation speed. It was found that the high shear processing is an effective method to improve the dispersion of the PAl2 phase in PE matrix when PA 12 contents are 5 wt% and 10 wt%, and the dispersed phase particle size is reduced with the increase of rotation speed from 100 r/min to 500 r/min. However, with further increase of PAl2 content to 20 wt%, high shear processing has no effect on the phase morphology of the blends. Accordingly, a largely increased elongation at break and impact strength are observed for PE/PAl2/95/5 and PE/PA12/90/10 blends obtained at high rotation speeds but no effect on the property of PE/PAI2/80/20. Annealing experiment demonstrated that the obtained phase morphology is not stable thus compatibilizer should be introduced in the future work. This work could provide a guideline for the application of high shear processing in the preparation of polymer blends with huge polarity difference.

Size Distribution and Anisotropy of the Minor Phase Droplets in Polypropylene/Ethylene-Octene Copolymer Blends: Effects of Shear and Component Miscibility

In this work, polypropylene （PP）/octene-ethylene copolymer （POE） blends were injection-molded using the so- called dynamic packing injection technique, which imposed oscillatory shear on the gradually cooling melt during the packing solidification stage. In this way, the effect of shear on the size distribution and anisotropy of the minor phase droplets could be investigated. Besides, by using two kinds of POE with different octene contents, the effect of component miscibility was also studied. The results show that the droplet size is mainly determined by composition and miscibility, and droplet anisotropy is mainly determined by droplet size and shear. Most importantly, under the same processing condition, droplet anisotropy increases with droplet size, and there seems a linear fit between them, disregarding the miscibility factor. These results may provide guidance for preparing polymer blends with desired properties by tailoring their phase morphologies.

Reconstruction of Core-Shell Dispersed Particles in Impact Polypropylene Copolymer during Extrusion

We reported an approach to reconstruct the complex phase morphology of impact polypropylene copolymer （IPC） with core-shell dispersed particles and to optimize its toughness in approximate shear condition. The molten-state annealing results indicate that the phase structure with core-shell dispersed particles is unstable and could be completely destroyed by static annealing, resulting in the degradation of impact strength. By using a co-rotating twin screw extruder, we found that the dispersed particle with core-shell structure could be rebuilt in appropriate condition with the recovery of excellent impact strength due to both the huge interfacial tension during solidification and the great difference in viscosity of components. Results reveal that almost all the extruded IPCs show the impact strength 60%-90% higher than that of annealed IPCs at room temperature. And the twice-extruded IPC shows the highest impact strength, 446% higher than that of IPC annealed for 30 min. As for low temperature tests, the impact strength of extruded IPCs also increases by 33%-58%. According to adjusting the processing conditions including extrusion speed, extrusion frequency and temperature, an optimization of toughness was well established.

Design and properties of calcium copper titanate/poly(dimethyl siloxane) dielectric elastomer composites

The high phase content of inorganic dielectric fillings will give a strong electric driving force and hard matrix. That is a contradiction in enhancing the electrodeformation of dielectric elastomers(DEs). Therefore, in this paper, by focusing on how to approach a balance between these and finding an effective way to tune the electric response of the DEs, the theoretical calculation and experimental investigation based on calcium copper titanate(CCTO)/poly(dimethyl siloxane)(PDMS) were carried out. It is found that CCTO with a smaller particle size shows a larger dielectric parameter. With smaller CCTO particle as the fillings, the fabricated elastomer composite would approach to a low modulus by a proper CCTO phase morphology in the matrix.