Characterization of the Microstructure Changes of Polypropylene Induced by Pan-milling

The microstructure changes of polypropylene induced by a complex combination of shearing, friction, compression and stretching actions during pan-milling were revealed by spectroscopic techniques. X-ray diffraction analysis showed that the structure of polypropylene transferred from crystal into amorphous after undergoing enough milling operation. No transformation between crystal forms was observed. The study of the high-frequency region of the Raman spectrum between 2800 and 3100cm-1 of polypropylene indicated that molecular motion and chain deformation of PP led to amorphization and deterioration of packing regularity during pan-milling. By co-panmilling PP with bis-(2,2,6,6-tetramethyl-4-piperidinyl) sebacate under ambient condition, ESR signals of free radicals formed by mechanochemical scission of main chain were observed, and an increase of ESR intensity with milling was detected.

Method for Control of Particle Size and Morphology of Paraffin/Polystyrene-Divinylbenzene Microcapsules

Microencapsulation of phase change materials(Micro PCMs) has been paid special attention because of their extensive applications in saving and releasing energy. Micro PCMs containing paraffin with a melting point of 55 ℃ in polystyrene-divinylbenzene(P(St-DVB)) were prepared by suspension-like polymerization. The characterization of microcapsules by FTIR, DSC and TG proved that paraffin had been successfully encapsulated and the proportion of encapsulated paraffin was 49.8%—58.5%. The effects of polyvinylpyrrolidone(PVP) with different molecular weights serving as the suspension stabilizer were investigated in detail. The results illustrated that the type of PVP had a significant influence on the particle size of Micro PCMs. The average diameter of Micro PCMs decreased with an increasing molecular weight of PVP. Moreover, the crosslinker-postaddition method was adopted in this study to improve the morphology of P(St-DVB) Micro PCMs. SEM images showed that when the DVB was added at the 2nd hour of polymerization the morphology of obtained P(St-DVB) Micro PCMs exhibited good sphericity since it could avoid the influence of cross-linker agent during the nucleation period.

Microstructure change in deuterium implanted CLAM steel induced by electron irradiation

As Reduced Activation Ferritic/Martensitic (RAFM) steel is considered the primary candidate for use as a structural material in fusion power reactors,many countries are developing different kinds of RAFM.China is developing new CLAM (China Low Activation Martensitic) steel.The study investigates microstructural changes in CLAM steel implanted with deuterium ions induced by 1250 keV electron irradiation from R.T.to 873 K,and observes both the growth and shrinkage of the defect clusters produced by deuterium ion implantation under the electron irradiation.

Production of thick-walled hollow glass microspheres for inertial confinement fusion targets by sol-gel technology

To fabricate thick-walled hollow glass microspheres （HGMs） for inertial confinement fusion （ICF） targets by sol-gel technology, we investigated the effects of glass composition, blowing agent, refining temperature, pressure and composition of furnace atmosphere on the wall thickness of HGMs by numerical simulation and experiments. The results showed that the residence times of the thick-walled HGMs in the encapsulating and refining phases decreased with the increase of wall thickness of HGMs. As a response to this challenge, glass composition must be optimized with the object of high surface tension and low viscosity at refining temperature, and the blowing agents with high decomposition temperature should be used, furthermore the concentration of blowing agents in gel particles must also be precisely controlled. The higher volume fraction of argon gas in the furnace atmosphere, the thicker the wall of HGMs. Due to the limited operating range of furnace atmosphere pressure, changing furnace atmosphere pressure could not significantly increase the wall thickness of HGMs. Although increasing refin- ing temperature can improve the yield of high quality HGMs, a higher furnace atmosphere temperature may lead to a decrease in the wall thickness of HGMs. When the volume fraction of argon gas in the furnace atmosphere ranged from 80% to 95%, the furnace atmosphere pressure ranged from 1.0×l0^5 Pa to 1.25×105 Pa, and the refining temperature ranged from 1600℃ to 1800℃, we produced thick-walled （5-10 ktrn） HGMs with good sphericity, wall thickness uniformity and surface finish. However, the yield of high quality HGMs needs to be further improved. The compressive strength, tensile strength and permeation coefficient to deuterium gas of thick-walled HGMs at ambient temperature decreased with increase of the wall thickness.