Hongli Wang

Poly(amidoamine) and poly(propyleneimine) dendrimers show distinct binding behaviors with sodium dodecyl sulfate: insights from SAXS and NMR analysis.

We investigate the interactions of generation 3 (G3) poly(amidoamine) (PAMAM) and G3 poly(propylenimine) (PPI) dendrimers with sodium dodecyl sulfate (SDS) in aqueous solution. Size and structure of the dendrimer-SDS aggregates as a function of SDS/dendrimer molar ratio were revealed by SAXS and NMR. G3 PAMAM has a relatively open and dense-core structure, while G3 PPI with the same number of surface amine groups possesses a compact and uniform structure. Upon addition of SDS, much more SDS monomers were encapsulated in the interior of PPI rather than in PAMAM. More significant size increase in PAMAM-SDS aggregate is observed at low SDS concentrations, due to the binding of SDS on PAMAM surface and further assembly into larger supramolecular structures. Both noncooperative and cooperative binding of SDS on G3 PPI surface are observed, while only noncooperative binding is proposed on G3 PAMAM, due to its open surface and large surface group distance. The size of the PPI-SDS complex is larger than that of PAMAM-SDS at higher SDS concentrations. Within the investigated SDS concentrations, SDS exhibits much stronger interactions with G3 PPI than with G3 PAMAM. These results provide new insights into dendrimer-surfactant interactions and explain why PPI is much more cytotoxic than PAMAM.

The neutron texture diffractometer at the China Advanced Research Reactor

The first neutron texture diffractometer in China has been built at the China Advanced Research Reactor, due to strong demand for texture measurement with neutrons from the domestic user community. This neutron texture diffractometer has high neutron intensity, moderate resolution and is mainly applied to study texture in commonly used industrial materials and engineering components. In this paper, the design and characteristics of this instrument are described. The results for calibration with neutrons and quantitative texture analysis of zirconium alloy plate are presented. The comparison of texture measurements with the results obtained in HIPPO at LANSCE and Kowari at ANSTO illustrates the reliability of the texture diffractometer.

Necessity and Feasibility of Building a New Indsans at Carr

China advanced research reactor (CARR) is already critical in 2010 and constructed with three neutron guides. One small angle neutron scattering spectrometer (SANS) has almost finished. This paper introduces the characteristic, application and development situation of SANS at home and abroad. The necessity and favorable circumstance of building a new INDSANS at CARR as soon as possible is also analyzed. Advantage of SANS Small angle scattering (SAS) is a key tool in material study at the nanoscale, including small angle x ray scattering (SAXS), light scattering (LS) and small angle neutron scattering (SANS). SANS is a unique method because of the characterization of neutron [1-4]. The neutron source for SANS is from two kind of huge facility. The one is nuclear reactor, the other one is spallation source. These two source expense huge money, big volume. They are hard to maintain. So it’s impossible to use SANS in every lab just like SAXS. It can be found only in the country which has these two sources. The method to detect the structure of material by neutron developed fast after Chadwick found neutron in 1932. This method allows characterization, in a non-destructive way, of small particles (precipitates, cavities, etc.) ranging in size between 1 and 100 nm. It can be used in many areas, like polymers, biology macromolecular and colloid. Besides this technique, giving statistical data representative of the whole sample, is particularly adapted to the study of structure materials like metals, magnetic clusters, ODS and so on [5-9]. Complementary to X-Ray techniques, SANS is a powerful non-destructive method for the investigation of materials and samples from various fields of activity, such as nuclear industry, energy industry and so on. One example is showed friction stir welding (FSW) is a better method than electro-sparked deposition (ESD) welding for joining nanostructured ferritic alloy (NFA) MA957 by Transmission electron microscopy (TEM) and small angle neutron scattering (SANS)[10].Another one is studied MA957 produced with two microstructures characterized by different grain sizes (Tensile, creep and impact properties were found to be strongly dependent on the size of nano particle). The nano particles are around 1 to 30nm.The relation between structure and behavior can be get by the result of SANS and other techniques[11]. Other examples are showed about the study of reactor structure materials such as pressure vessel steel and so on[12-15].For example, the effect of hydrogen in irradiated reactor pressure vessel steels is studied by SANS. Because the cross section of hydrogen is totally different. So the relation between the content of hydrogen and the ability of creep can be get by SANS. The final experiment showed the structure of hydrogen can be studied even if the concentration of hydrogen is not more than 1-2ppm by SANS and the effect of hydrogen has relation with the type of steel. The nano structure in 8-20nm produced by hydrogen is good for improve embrittlement. SANS is the method to detect the nanostructure in total cm size samples in above examples. So it’s a unique method as others like TEM. Besides SANS is a better way when the nano structure in solution needs to be studied in industry [16-18]. Proceedings of the 3rd International Conference on Material Engineering and Application (ICMEA 2016) Copyright

X-ray analysis on crystal structures of crystalline polyimides

A high performance engineering plastic material based on crystalline polyimide was prepared by hot-press method after the resin was synthesized. The mechanical properties including tensile properties, compression properties, bending properties, impact toughness, shearing strength were first investigated. The material displayed excellent mechanical properties and could be used at high temperatures. Since the tensile experiment was operated at 25°C, 250°C and 280°C, respectively. So the progress of crystals grown was affected by load and temperature at the same time, and residual stress would be existed in the samples. X-ray diffraction experiments were then conducted to investigate the difference of crystal structures formed under different conditions. Results indicated that the main diffraction peaks were almost same, but the position of some week peaks changed a little. The material then isothermally crystallized at different temperatures and they displayed same crystal structures by X-ray diffraction experiment.