Advanced Materials Research Vol. 705

Abstract: A novel cheap macromolecular intumescent flame retardants (Cu-MIFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus-copper characterized by IR. Epoxy resins (EP) were modified with Cu-MIFR to get the flame retardant EP, whose flammability and burning behavior were characterized by UL 94, limiting oxygen index (LOI), dilatation, char yield, smoke density rating (SDR) and maximum smoke density (MSD). The epoxy resins were obtained for the UL 94 V-0 rating at low Cu contents of 3.0 % get a LOI of 27.0% and char yield of 19.4%. Dilatation, SDR and MSD of EP/Cu-MIFR decreased. The degradation behavior of the EP/Cu-MIFR was studied by TG and EDX analysis. The experimental results exhibited that the initial decomposition temperature (IDT) was decreased, integral procedure decomposition temperature (IPDT) and amounts of Cu and P at the residue were increased.

Abstract: Hemp was treated with guanidine carbonate to impart flame retardance. The thermal degradation of the samples were studied by thermogravimetry (TG) and differential thermal analysis (DTA). The flame retardance was determined by LOI. Morphology of the char structure was studied by SEM to obtain information concerning the thermal degradation mechanism. For hemp treated with guanidine carbonate, which has higher LOI and char yield values, the oxidative decomposition stages include a decomposition stage at lower temperatures (172-210°C) , leading to more carbonaceous residue and small amount of flammable products to get the good flame retardance. The SEM of the chars of hemp treated with guanidine carbonate also indicate the structure of the charring layer may increase heat insulation, and protect inner matrix materials.

Abstract: Numerical simulation of small-scale explosion in dry sand using two sand material models including the Sand model and the LA model were carried out in the present study. Three cases were considered which the depths of burial (DOB) of the explosive C4 charge were 0, 30 mm and 80 mm, respectively. The time arrival of the blast-wave front and the maximum overpressure of fixed measuring locations were studied using a two dimensional axisymmetric model in hydrocode ANSYS/AUTODYN. Furthermore, the crater diameters and the heights of detonation product cloud respect to the time were also studied by comparing with the test data. The simulation results indicate that the both sand material models were hardly predict the test data exactly which proves that the sand properties and the material model should be more carefully studied and defined.

Abstract: The well-defined block copolymer PMMA-b-PS was prepared by two-step ATRP in emulsion system. GPC results indicate that M_n increased linearly with conversion and polydispersity remained relatively narrow. It presents the characteristics of living polymerization in emulsion system. FT-IR demonstrated that block copolymer PMMA-b-PS could be successfully synthesized by ATRP with macroinitiator PMMA-Cl in emulsion system. The morphological characteristic of the self-assembly depends on the block copolymer concentration and transforms between spheres and rodlike micelles. The property indicates a perfect potential application in drug delivery materials.

Abstract: .A series of vertically aligned ZnO nanorod-array films are grown on fluorine-doped tin oxide (F: SnO2, FTO) coated glass substrates by the solution-based chemical process. The effect of polyethyleneimine (PEI) adding in seed and growth solution on the structure, morphology, UV-Vis absorption spectra and photovoltaic properties of ZnO nanorod array films, has been analyzed. The XRD and SEM results showed that the ZnO nanorod have the hexagonal wurtzite structure with the (002) direction normal to the substrate. It was observed that with the addition of PEI in growth solution, the ZnO nanorods become smaller in diameter and longer in length i.e. greatly enhance their surface area, leading to improve dye adsorption and photovoltaic performance of DSSCs. The efficiency of ZnO nanorod-based DSSC with PEI in growth solution was on average 1.18 % for film A4, which is 84 % higher than for ZnO nanorod-based DSSC without PEI in growth solution.

Abstract: Graphene/spacer nanoparticle composites were prepared by reducing graphene oxide with hydrazine in the presence of different contents of polyaniline nanoparticles. In-situ cryo-TEM image of GO-spacer solution shows that spacer nanoparticles are anchored on GO sheets. During the reduction, as-adsorbed spacer nanoparticles were sandwiched between layers of graphene. These spacer nanoparticles act as spacers to create gaps between neighboring graphene sheets, resulting in higher surface area. Graphene/spacer nanocomposites exhibited highest specific surface area of 1500 m²/g. Utilizing this composite material, a supercapacitor with specific capacitance of 267 F/g at a current density of 0.1 A/g was achieved.

Abstract: In this study, vacuum brazing of diamond grit was performed using an Ni-10Sn-28Cr alloy in order to examine the interfacial behaviors. In order to study the wettability between diamond grit and the brazing alloy, a graphite was used instead of diamond grit. The contact angle of Ni-10Sn-28Cr alloy and graphite decreased with increasing holding time and temperature. The shear strength between graphite and Ni-10Sn-28Cr filler alloy showed the best value of 29.8 MPa at 1100°C brazing temperature. It was shown that the shear strength was decreased significantly due to the increase of the thickness of brittle reaction layer and interface residual stress, as the brazing temperature increased up to 1200°C. In regards to the thermal stability evaluation of diamond grits, the graphitization of diamond grit was observed to occur at 1300°C brazing temperature after 60 minutes. Beyond 1100°C brazing temperature, diamond grit exhibited ideal setting in the brazing filler alloy, whereas process diamond grit was observed to be fully embedded in the brazing alloy and damaged at 1200°C temperature. The results of interface analysis of the diamond grit joints brazed by the brazing alloy showed that the chromium carbides played an important role in high strength bonding and as the brazing temperature increased, existing angular chromium carbide transformed into acicular chromium carbide.

Abstract: We use molecular dynamics simulations method to investigate the behavior characteristics of AB diblock copolymers that are adsorbed on a planar surface. Adsorption density has been distinguished, depending on the adsorption manner of A-block on the (100) surface and formation of brushes. It is examined in detail that conformational behavior of the brushes affects the adsorption density. In addition, we make a comparison of linear brush with length ratio of the A-block to the chain, in the cases of the fixed length of chain and the fixed length of A-block, respectively. The result shows that the adsorption density is strongly affected by the length ratio of the A-block to the chain. And our findings can be used as a guide for fabrication and preparation of actual synthetic polymer brushes on a solid surface by the approach of physical adsorption.

Abstract: Development of a single bubble in free space under the canonical ensemble was studied by using molecular dynamics simulation method. The detailed dynamic characteristics in the evolution process were analyzed by calculating the displacement of molecules, density, diffusion coefficient, pressure and potential energy of bubble. The results indicate that the evolution is divided into three stages according to the change of bubble potential energy, which are expansion, compression and balance state respectively. The temperature and density have significant influences on the final state of bubbles. The bubble in the liquid with larger density has a higher transition rate. The collapsing speed of bubble becomes faster with temperature increasing.

Abstract: Objective: to exam the impact of the gass relative humidity on the dielectric barrier discharge. Method: high voltage AC power supply and wire-cylinder reactors are used to observe the discharge characteristics of empty reactors and reactors with the ceramic filler respectively under different relative humidity circumstances. Results: in the empty reactors,the discharge current decreases with the increase of the gas relative humidity; in the reactors with ceramic filler,with the increase of the gas relative humidity, the discharge current first decreases slowly and then increases immensely. Conclusion: Relative humidity has a significant impact on gas discharge. By comparing the experimental results of the two groups, the conclusion is: when RH< 47%, the discharge current of the empty reactors is greater than that of the reactors with ceramic filler,and when RH > 47%,the result is just the opposite.