Influence ofβ-nucleating Compound Agents on the Mechanical Properties and Crystallization Behavior of Polypropylene Random Copolymer

A novel polypropylene random(PPR)composite materials with optimized properties was developed by addingβ-nucleating compound agents(rare earth complex WBG-2 and aryl amide derivative TMB-5)and ternary compound modifier(TPE/WBG-2/CaCO_(3)).The effects of differentβ-nucleating agents and ternary compound modifier on the mechanical properties and crystallization behavior of PPR were analyzed.The results show that,compared with pure PPR materials,both WBG-2 and TMB-5 could significantly improve the impact strength of PPR.The crystallization temperature of PPR increased with the addition ofβ-nucleating agent.The modified PPR prepared with ternary compound modifier showed the most excellent comprehensive properties.

A 3–5μm broadband YBCO high-temperature superconducting photonic crystal

Photonic crystal structures have excellent optical properties,so they are widely studied in conventional optical materials.Recent research shows that high-temperature superconducting periodic structures have natural photonic crystal features and they are favourable candidates for single-photon detection.Considering that superconductors have completely different properties from conventional optical materials,we study the energy level diagram and mid-infrared 3μm–5μm transmission spectrum of two-dimensional superconducting photonic crystals in both superconducting and quenched states with the finite element method.The energy level diagram of the circular crystal column superconducting structure shows that the structure has a large band gap width in both states.At the same fill factor,the circular crystal column superconducting structure has a larger band gap width than the others structures.For lattice structures,the zero transmission point of the square lattice structure is robust to the incident angle and environmental temperature.Our research has guiding significance for the design of new material photonic crystals,photon modulation and detection.

Emergence of High-Temperature Superconducting Phase in Pressurized La_(3)Ni_(2)O_(7)Crystals

The recent report of pressure-induced structural transition and signature of superconductivity with T_(c)≈80 K above 14 GPa in La_(3)Ni_(2)O_(7)crystals has garnered considerable attention.To further elaborate this discovery,we carried out comprehensive resistance measurements on La_(3)Ni_(2)O_(7)crystals grown in an optical-image floating zone furnace under oxygen pressure(15 bar)using a diamond anvil cell(DAC)and cubic anvil cell(CAC),which employ a solid(KBr)and liquid(glycerol)pressure-transmitting medium,respectively.Sample 1 measured in the DAC exhibits a semiconducting-like behavior with large resistance at low pressures and gradually becomes metallic upon compression.At pressures P 13.7 GPa we observed the appearance of a resistance drop of as much as~50%around 70 K,which evolves into a kink-like anomaly at pressures above 40 GPa and shifts to lower temperatures gradually with increasing magnetic field.These observations are consistent with the recent report mentioned above.On the other hand,sample 2 measured in the CAC retains metallic behavior in the investigated pressure range up to 15 GPa.The hump-like anomaly in resistance around~130 K at ambient pressure disappears at P≥2 GPa.In the pressure range of 11–15 GPa we observed the gradual development of a shoulder-like anomaly in resistance at low temperatures,which evolves into a pronounced drop of resistance of 98%below 62 K at 15 GPa,reaching a temperature-independent resistance of 20μΩbelow 20 K.Similarly,this resistance anomaly can be progressively shifted to lower temperatures by applying external magnetic fields,resembling a typical superconducting transition.Measurements on sample 3 in the CAC reproduce the resistance drop at pressures above 10 GPa and realize zero resistance below 10 K at 15 GPa even though an unusual semiconducting-like behavior is retained in the normal state.Based on these results,we constructed a dome-shaped superconducting phase diagram and discuss some issues regarding the sample-dependent behaviors on pressure-induced hightemperature superconductivity in the La_(3)Ni_(2)O_(7)crystals.

Effect of yttrium on thermal stability and crystallization behavior of Nd_(60)Fe_(20)Al_(10)Ni_(10) amorphous alloys

The effect of yttrium on the thermal stability and crystallization behavior of Nd-Fe-Al-Ni amorphous alloys was investigated using X-ray diffraction （XRD）, differential scanning calorimeter （DSC）, and transmission electron microscopy （TEM）.The results indicated that the as-cast Nd60Fe20Al10Ni10-xYx（X=-0, 2） amorphous alloys were fabricated with some quenched-in crystals, which could be restrained by Y. With the effect of yttrium, both the crystallization temperature and exothermic peak shifted to higher temperatures, illustrating that the thermal stability could be improved. The addition of Y changed the crystallization process and final crystallization results. Moreover, the crystallites in the amorphous matrix became more homogeneous and smaller. Meanwhile, Y was useful for the passivation of oxygen in chemistry and restrained the negative effect of oxygen. The activation energies of the start of crystallization and peaking were 1.21 and 1.16 eV, respectively, according to the Kissinger equation.

Miscibility, Crystallization, and Rheological Behavior of Solution Casting Poly（3-hydroxybutyrate）/poly（ethylene succinate） Blends Probed by Differential Scanning Calorimetry, Rheology, and Optical Microscope Techniques

The miscibility and crystallization of solution casting biodegradable poly（3-hydroxybuty- rate）/poly（ethylene succinate） （PHB/PES） blends was investigated by differential scanning calorimetry, rheology, and optical microscopy. The blends showed two glass transition temperatures and a depression of melting temperature of PHB with compositions in phase diagram, which indicated that the blend was partially miscible. The morphology observation supported this result. It was found that the PHB and PES can crystallize simultaneously or upon stepwise depending on the crystallization temperatures and compositions. The spherulite growth rate of PHB increased with increasing of PES content. The influence of compositions on the spherulitic growth rate for the partially miscible polymer blends was discussed.

Dynamic mechanical behavior of a Zr-based bulk metallic glass during glass transition and crystallization

The dynamic mechanical behaviors of the Zr41Ti14Cu12.5Ni8Be22.5Fe2 bulk metallic glass （BMG） during continuous heating at a constant rate were investigated. The glass transition and crystallization of the Zr-based BMG were thus characterized by the measurements of storage modulus E′ and internal friction Q^-1. It was found that the variations of these dynamic mechanical quantities with temperature were interre-lated and were well in agreement with the DSC trace obtained at the same heating rate. The origin of the first peak in the internal friction curve was closely related to the dynamic glass transition and subsequent primary crystallization. Moreover, it can be well described by a physical model, which can characterize atomic mobility and mechanical response of disordered condense materials. In comparison with the DSC trace, the relative position of the first internal friction peak of the BMG was found to be dependent on its thermal stability against crys-tallization.

FRACTAL BEHAVIOR OF DEVELOPMENT OF PHASE SEPARATION AND CRYSTALLIZATION IN BLENDS OF NYLON-6 WITH SODIUM SALT OF ETHYLENE /METHACRYLIC ACID COPOLYMER

Phase separation was studied by the optical microscopy in blends of nylon 6 (PA6) with sodium salt of ethylene/methacrylic acid copolymer (PEMA).The image collecting technology was used to keep track of the development of blends at a certain temperature.The fractal dimension of phase separation was calculated by the image solving technology according to the fractal theory and the self similarity behavior of the process was proved.The relationship of the fractal behavior with composition and experimental temperature was discussed.The fractal behavior of the crystallization development of the crystal phase of PA6 in blends was also discussed and the fractal behavior calculated.

Influence of Carbon Nanofiber Addition on Mechanical Properties and Crystallization Behavior of Polypropylene

Carbon nanofiber （CNF）-reinforced polypropylene （CNF/PP） composites with different CNF contents were prepared by melt mixing, and the mechanical properties and crystallization behavior of the CNF/PP composites obtained were investigated. It was found that the tensile modulus of the composites was increased with the addition of CNFs, but their elongation at break and fracture strain energy were decreased, while the tensile strength of the composites was firstly increased and then decreased due to the agglomeration of CNFs at higher loading. Nonisothermal crystallization analysis showed that the CNFs played a role as nucleating agent in PP matrix, which led to increment in the crystallization rate and the degree of crystallinity of PP. Moreover, X-ray diffraction studies showed that the CNFs incorporated in the PP matrix favored the growth of （040）-oriented PP crystals. With the increase in the CNF content, the nucleating and orientation roles of the CNFs were obviously enhanced.

Crystallization behavior of Fe_(78)Si_(13)B_9 metallic glass under high magnetic field

The effects of high magnetic field on the crystallization behavior of the Fe78Si13B9 metallic glass ribbon were studied. The samples were isothermal annealed for 30 min under high magnetic field and no field,respectively. Microstructure transformation during crystallization was identified by X-ray diffraction and transmission electron microscopy. It was found that the crystallizations of Fe78Si13B9 metallic glass processed under different conditions were that the precipitation of dendrite α-Fe（Si） and spherulite （Fe,Si）3B phases forms amorphous matrix and then the metastable （Fe,Si）3B phase transforms into the stable Fe2B phase. The grain size of the crystals is smaller and more homogeneous for the isothermal annealed samples under high magnetic field in comparison with that under no field indicating that the crystallization behavior of Fe78Si13B9 metallic glass is suppressed by high magnetic field.

Effect of Rare Earth on the Crystallization Behavior of Li_2O-Al_2O_3-SiO_2 Glass-ceramic

X-ray powder diffraction and Fourier transform infrared spectroscopy were applied for characterization of Li2O-Al2O3-SiO2 glass-ceramic powders doped with Eu2O3,Gd2O3 and Er2O3,respectively,in the conditions of different heat-treatment temperatures and with various amounts.The powders were derived from the polyacrylamide gel method.The results show that,the wet gels prepared by polyacrylamide perform a unique crystallization behavior in the process of drying,comparing with some customary preparation such as melt processing.The main crystal phase and crystallization sequence of Li2O-Al2O3-SiO2 micro-powders have no distinct with addition of Eu2O3,Gd2O3 or Er2O3,while the crystallization temperature of the β-spodumene decreased and the amount of the β-spodumene increased.

High-temperature Tensile Behavior of Laser Welded Ti-22Al-25Nb Joints at Different Temperatures

The high-temperature tensile behavior of laser welded Ti-22Al-25Nb (at%) joints was investigated at 500,650,800,and 1 000 ℃.The temperatures for tensile tests were selected according to the phase transformation sequence of Ti2AlNb-based alloys.At temperatures lower than the B2+O phase field (500 ℃) and higher than the B2+O phase field (1 000 ℃),the joints fracture in the base metal in ductile fracture mode.By contrast,the joints exhibit obvious high-temperature brittleness in the B2+O phase field (650 °C and 800 ℃).Heat treatments were conducted with respect to the thermal history of tensile specimens.Intergranular microcracks along the grain boundary of B2 phase are found in the fusion zone after the heat treatments at 650 ℃ and 800 ℃.The high-temperature brittleness at 650 ℃ and 800 ℃ is attributed to the B2→O transformation along the grain boundary.The stress concentration caused by the volume change of B2→O transformation also contributes to the high-temperature brittleness of laser welded Ti-22Al-25Nb joints.

Study on Morphology and Non-isothermal Crystallization Behavior of Poly(phenylene sulfide)/Poly(ethylene-co-cyclo-hexane 1,4-dimethanol terephthalate) Blend

A binary alloy consisting of poly（phenylene-sulfide） （PPS）/poly（ethylene terephthalate-co-l,4- cyclohexanedimethanol） （PETG） was prepared by the melt blending technology using a twin-screw extruder. The morphology and crystallization behavior of the alloy material were investigated by means of SEM, POM and DSC. The SEM study of the alloy samples revealed that PPS and PETG comprised an incompatible system and the interface structure of two phases could be observed distinctly when the composition of the binary alloy was being changed. The POM results had revealed that incorporation of PETG into PPS could lead to formation of larger spherulite crystals in the course of PPS crystallization, but small and grainy spherulite crystals appeared with further increase in the PETG concentration. The DSC analyses revealed that addition of PETG to the alloy composition could shift the PPS crystallization temperature towards the high-temperature region.

Crystallization behavior of electroless Co-Ni-B alloy plated in magnetic field in presence of cerium

The electrochemical property, chemical composition and crystal structure of electroless Co-Ni-B-Ce alloy plated in general state as well as in magnetic field were studied using potentiometer, plasma emission spectrometer, X-ray diffractometer, transmission electron microscope. The results show that the static potential and polarizability of electroless Co-Ni-B alloy are remarkably improved as the plating is carried out in magnetic field in the presence of a little amount of cerium in plating bath. Because of the action of magnetic field and rare earth element cerium, the boron content in alloy decreases, while cobalt and nickel contents increase. As a result, the amorphous Co-Ni-B alloy transforms to the microcrystalline Co-Ni-B-Ce alloy when the plating is in general state, and the Co-Ni-B alloy makes a crystalline transformation because of the action of magnetic field and rare earth element cerium.

Crystallization behavior of melt-spun NdFeB permanent magnets

The crystallization behavior of melt spun Nd 8.5 Fe 78 Co 5Cu 1Nb 1B 6.5 ribbons was investigated using dynamic differential scanning calorimetry (DSC) and X ray diffractometry (XRD). It was found that the as spun ribbons crystallize in two steps: at first the Nd 3Fe 62 B 14 + α Fe phases are formed and subsequently Nd 3Fe 62 B 14 transformed to Nd 2Fe 14 B and α Fe upon heating above 680?℃. The effective activation energy of two crystallization peaks are 332.0?kJ/mol and 470.5?kJ/mol, respectively. As the wheel speed increases, the magnetic properties of the magnet change obviously. When the wheel speed is 18?m/s, the best magnetic properties of the magnet was obtained after the sample was annealed at 690?℃ for 8?min: B r=0.74T, i H c=421.7?kA/m, ( BH ) max =64.5?kJ/m 3.

Isothermal Crystallization Kinetics and Melting Behavior of POE-g-MAH Compatibilized PA11/POE Blends

A new Nylon 11（PA11）/polyethylene-octene（POE） blends compatibilized by maleic anhydride grafted mixture polyethyleneocten（POE-g-MAH） was prepared through melt blending method.The isothermal crystallization kinetics and melting behaviors of PA11/POE blends were investigated in detail by differential scanning calorimetry（DSC） and polarized optical microscope.The n values of PA11 blending with POE or POE-g-MAH are almost similar with pure PA11,which indicates that the effect of POE and POE-g-MAH on nucleation and growth of PA11 crystal is slight.The overall crystallization rate of PA11/POE blends are higher than ones of pure PA11 at the same crystallization temperatures,but they decrease significantly when POE-g-MAH is added into PA11/POE blends.DSC heating curves of both PA11 and its blends exhibit two melting peaks,but the two melting peak become weaker when POE-g-MAH is add into PA11/POE blend systems.And the spherulite size is reduced significantly by the addition of POE-g-MAH compared with pure PA11 and PA11/POE blends.

STUDIES ON THE MECHANICAL PROPERTIES AND CRYSTALLIZATION BEHAVIOR OF POLYETHYLENE COMPOSITES

The effects of interfacial modifier on the mechanical, dynamic mechanical properties and crystallization behavior of the polyethylene composites were investigated in the present paper. It was found that the interfacial modifer significantly improved the mechanical properties, influenced the dynamic mechanical spectra and slightly changed the crystallization behavior. The results showed that the interfacial modifier changed the dispersion state of dispersed phase of the composites, resulting in different phase structure, which was the major reason leading to different mechanical and crystallization properties.

Crystallization behavior of Ti_3Al-Nb alloy laser beam welding joints

CO2 laser beam welding experiment of Ti3Al-Nb alloy was conducted by adopting overlay welding, the resulting special crystallization phenomenon of welding joint was analyzed. The joints have obvious crystallizing layer phenomenon with clear bond-like contours after laser welding. The results of X-spectrofluorimetry and energy spectrum analysis indicate that the non-uniform distribution of elements exists in crystallizing layer, because the temperature gradient is an important factor that impacts the alloy crystallization behavior. Furthermore, the effects of welding heat source, welding speed, pulse frequency and welding preheat on crystallizing layer distribution were investigated.

Crystallization Behavior and Thermal Properties of PP/MgAl LDH Nanocomposites Prepared in Non-polar Solution

Polypropylene（PP）/MgAl layered double hydroxide（MgAl LDH） nanocomposites were synthesized by refluxing PP and dodecyl sulfate-intercalated MgAI LDH[MgAI（DS）] in non-polar xylene. Their structure, thermal and crystallization properties were studied via X-ray diffraction（XRD）, transmission electron microscopy（TEM）, thermogravimetric analysis（TGA）, differential scanning calorimetry（DSC）, and polarized light microscopy（PLM）. The nanoscaled dispersion of MgAI（DS） nanolayeres in the PP matrix was verified by the disappearance of the d（003） XRD diffraction peak of MgAI（DS） and observation of TEM image. The DSC data show that the SDS/LDH inorganic components negatively affect the crystallization properties of PP and decrease the size of PP sphcrulites because the inorganic components act as additional nuclei. The PP/MgA1 LDH nanocomposites have a faster charring progress in a temperature range of 250--430 ℃ and a better thermal stability above 320℃ than pure PP.

Crystallization Behavior of Poly(Tetramethylene Oxide) Influenced by the Crystallization Condition of Poly(Butylene Succinate) in Their Copolymers

The effect of crystallization conditions of poly(butylene succinate)(PBS) component on the crystallization of poly(tetramethylene oxide)(PTMO) component in their segment block copolymer, with a higher PTMO content(PTMO mass fraction is 67%), was investigated by DSC and temperature-dependent FTIR. It is found that the isothermal crystallization time(tIC) of PBS has an effect on the crystallization behavior of PTMO component. Perturbation correlation move-window two-dimensional(PCMW2 D) correlation analysis and generalized 2 D correlation analysis(2 DIR) were performed to explore the origin of this phenomenon. The PCMW2 D and 2 DIR results show that the correlation intensity peak observed at around 20 ℃ for PTMO is due to the PTMO chains movements forced by the PBS chains folded movements. If tIC of PBS at temperature of 20 ℃ is prolonged, more PTMO components are incorporated in the region between PBS lamellae and the peak at-7.6 ℃(belonging to less-constricted PTMO chains) changes smaller and even disappears, while the peak at-16.3 ℃ belonging to more-constricted PTMO chains gets bigger. A crystallization model was also established in this study. The results of tensile testing showed that tensile strength slightly increased and elongation at break decreased with increasing heat treatment time at 40 ℃.

Regulation of Pore Structure and Hightemperature Fracture Behavior of CACbonded Alumina-Spinel Castables Based on Hydration Design

The lamellar hydrates of CAC were designed with the introduction of nano CaCO_(3)or Mg-Al hydrotalcite(M-A-H),and the effects on the green strength,pore structures,and high-temperature fracture behavior of alumina-spinel castables were investigated.The results show that nano CaCO_(3)or M-A-H stimulates rapidly the hydration of CAC and the formation of lamellar C_(4)AcH_(11)or coexistence of C_(2)AH_(8)and C_(4)AcH_(11)at 25℃.The formation of lamellar hydrates can contribute to a more complicated pore structure,especially in the range of 400-2000 nm.Meanwhile,the incorporation of well-distributed CaO or MgO sources from nano CaCO_(3)or M-A-H also regulates the distribution of CA_(6)and spinel(pre-formed and in-situ).Consequently,the optimized microstructure and complicated pore structure can induce the deflection and bridging of cracks,thus facilitating the consumption of fracture energy and enhancing the resistance to thermal stress damage.