Advanced Materials Research Vol. 510

Abstract: Melamine formaldehyde (MF) foam is a kind of fire-retardant material, which has many excellent properties. In this paper, the effect of foaming agent on foam-cell structure of MF foam was discussed, along with the compressive property, the water absorption and its thermo gravimetric behavior as well as its fire-retardant property behaved by limited oxygen index (LOI). Through the analysis of different factors affected on MF foam and its properties we hope to get practical products with good properties. Keywords: melamine foam; foaming agent; foam-structure; thermal property; fire-retardancy;

Abstract: Polymer microstructures are used more and more in many fields. Hot embossing is one of molding processing to achieve micro polymer components. In this paper, bulk metallic glass was selected as mold material to fabricate mold insert of micro hot embossing. Traditional UV-lithography and ICP-etching were used to achieve micro features on silicon wafer. And then, micro features were transferred from silicon wafer to bulk metallic glass mold insert above its glass transition temperature. Finally, applied bulk metallic glass mold insert to replicate polymer microstructure with hot embossing. Three commonly used thermoplastic polymers: high-density polyethylene (HDPE), polypropylene (PP) and polycarbonate (PC) were selected in this study. Experiments show that microstructures can have a good replication from bulk metallic glass mold insert to the thermoplastic polymer using hot embossing.

Abstract: Ternary titanium aluminum carbide powder was prepared by pressureless sintering at different temperature using elemental powder mixture of Ti, Al, and active carbon whose molar ratios was 3Ti/1.1Al/1.8C and effects of doping Si were discussed from 3.0Ti/1.0Al/0.1Si/1.8C and 3.0Ti/0.9Al/0.2S/1.8C. X-ray diffractions (XRD) patterns were used to detect the phase composition and scanning electron microscope (SEM) patterns were observed to investigate the microstructure of samples respectively. Results showed that Ti₂AlC and Ti₃AlC₂ which had obvious layered structure were synthesized by pressureless sintering of 3Ti/1.1Al/1.8C at 1300°C-1500°C. However, the samples doping Si were made of Ti₂AlC, Ti₃AlC₂ and Ti₃SiC₂. When the amount of Si-doped increased and Al/Si decreased, the amount of Ti₃AlC₂ and Ti₃SiC₂ went up with Ti₂AlC going down. Interestingly, the character of layered structure became unconspicuous at same temperature. Moreover, the mechanism that doping Si was not helpful to form Ti₂AlC but Ti₃AlC₂ was explained.

Abstract: Effects of different components, autoclaving temperature and autoclaving time on the microstructure features and mechanisms of hydrothermal reactions of activated saline soil were investigated by using XRD, DAT and other microstructural analytical methods. Collected from Tianjin Binhai New District, the mainly raw materials used in this study are the saline soil ( 65%) supplemented with calcareous materials. The results demonstrate that with an increasing calcium to silicon ratio, the diffraction peaks of C₂SH(A) and tobermorite fluctuate; the peaks increase initially, then dip down slightly before rising up again. With increasing autoclaving time, the order of generated hydration products is as following: C₂SH(A) tobermorite gyrolite. Specifically, once autoclaving time reaches 3h, the changing trend of C₂SH(A) to tobermorite becomes obvious, and the conversion from tobermorite to gyrolite can also be observed easily. The hydration products of autoclaved saline soil include mainly C₂SH(A) and tobermorite, along with a small amount of CSH(B). Microscopic analysis observed by us reveals that a number of scattered, small and white tobermorite crystals are closely attached to quartz surface, which might play a key role in increasing the strength of the system.

Abstract: The effects of different components, autoclaving temperature and time on the mechanical properties of saline soil bricks were investigated. The autoclaved curing schedule is optimized at autoclaving time of 3h and autoclaving temperature of 175. The optimal material formula consists of water-binding ratio 0.2, CaO 15%, finely grinded quartz powder 20 % and sand 20%, under which the compressive and flexural strengths of saline soil bricks reaches 31.9 Mpa and 7.8Mpa, respectively. Reducing water-binding ratio will effectively promote density, while increasing the amount of CaO will enhance the hydrothermal reaction products, density and the mechanical strength. In addition, adding finely grinded quartz powder and sand will further increase the hydrothermal reaction products and restrict volume shrinkage. Furthermore, elevating autoclaving temperature and extending autoclaving time are favorable to increase density and to improve mechanical properties. But autoclaving time exceeds 3h, the compressive strength will be reduced.

Abstract: The U-ring reciprocating seal structure with high pressure was taken as research object; the nonlinear contact characteristics and failure mechanism of U-ring seal were analyzed. Finite element model was build through segmentation and sweep methods, Mooney-Rivlin model was selected to characterize the rubber material, the Generalized Lagrange Multiplier Method were designed as contact algorithm. Based on LS-DYNA software, the 3D nonlinear dynamic simulations of U-ring seal structure were realized under different conditions. The results shows that the maximum contact stress steady increased with the growth of medium pressure, relative velocity, and friction coefficient, the top of inner lip and the circle of bottom hole were the main sites of contact stress concentrated on, the reverse velocity of valve stem is the main factor impact too large contact stress and seal damage. The simulation conclusions were verified by comparing the characteristics of actual seal failure.

Abstract: This article established 3D FE model of dual-radius arc finishing groove and tangent expansion angle finishing groove using ANSYS / LS-DYNA software for Wuhan Iron and Steel plant Ф16 hot continuous bar, and analyzed metal flow pattern, stress and strain distribution of two types finishing grooves. The results show that surface stress and strain distribution of dual-radius arc finishing groove have better uniform than them of tangent expansion angle finishing groove, and dual-radius arc finishing groove ensures the stability of the rolled piece in finishing groove, improve the dimensional accuracy and surface quality of rolled finishing product.

Abstract: The blend films were fabricated via blending sodium hyaluronate (SH) and Konjac glucomannan (KGM). Lactic acid was applied as modifier and the mixture of Ammonia and anhydrous alcohol as cross-linker. The influencing factors were analyzed via the orthogonal experiment L16(4,5). It was shown that the water absorption of the blend films was around 151%~608%. Tensile strength and elongation of the blend film samples reached about 11.3~20.7MPa and 10.8~20.2% respectively. The degradation rate declined obviously compared with the simple use of the SH. XRD and IR spectra indicated that crystallinity of the blend films was enhanced slightly after cross-linking. The blend films were co-cultured with bone mesenchymal stem cells. It was demonstrated that the films could support the growth of cells and were non-toxicity and good biocompatibility.

Abstract: The microstructure and the mechanical properties of welding joint with the material of R60702 have been studied in this paper with the specimens made with the method of argon-arc welding, and the according mechanical properties of the weld joint have been compared with the annealed microstructure at the temperature of 600.Conclusions have been obtained as follows: The organizations of the welding joint include base material, normalizing zone, overheated area, fusion zone and the weld zone; the hardness tendency of the weld joint is depicted as W-shape with the hardest point located at the center, and the softest points is located at the normalizing zone; the annealing treatment can improve the ductility and soften the weld joint mainly at the center.

Abstract: The ultra-zeolite is an important research topic at present. Using ultra-zeolite 4A to treat wastewater has the advantage that traditional methods do not have, so it has been concerned by many experts and scholars. This subject adopts microwave method to synthesize ultra-zeolite 4A. Then using the prepared ultra-zeolite 4A to adsorb Cr³⁺ in wastewater. Study on the effect factors such as pH value, adsorption temperature, etc. The conclusion shows that ultra-molecular sieve 4A has been successfully synthsized by microwave method. In experiment of absorption wastewater containing Cr^{3 +} we has found when the concentration of solution containing Cr^{3 +} is 400mg / L, pH =4, temperature is 25 and adsorption time is10 minutes, which ultra-zeolite 4A removes Cr³⁺ is better.