Advanced Materials Research Vol. 773

Abstract: The synthesis of hexafluoropropylene oxide in fixed-bed reactor using HFP as raw materials and molecular oxygen as oxidant is studied in the present paper. The selectivity of HFPO on the Ag/γ-Al₂O₃ catalyst prepared by impregnation can get 41.8%. The influence of the Ag/γ-Al₂O₃ catalyst modified by impregnation-sedimentation method and first group metal salts on synthesis reaction was investigated, as well as process conditions.

Abstract: Flax fibres surface were treated by different treatment in order to enhance the interfacial bonding force between flax natural fibres and vinyl resin matrix. The experiment of contact angle and mechanical property were done to characterize the surface topography and bonding force and choose the best modification. What’s more, the morphology behaviour of the flax fibre surface were charact- erized using SEM.

Abstract: The civil and construction industry is the basis of industries, it has always been known as the "leading industry" and in such industry the basic material is reinforced concrete. Even in this 21st century materials science and engineering methods have developed perfectly, reinforced concrete still is the main structure material in civil and construction industry. Formwork activity is one of indispensable matters during concrete forming and hardening processes. Once the forming process has defect, it might cause the formwork collapse during the concrete placing procedure. Such damage will result in pecuniary loss or workers life. This illustrating that the formwork is one of the most important materials in theconstruction industry. In general, formwork is mainly usedtimberas its rawmaterial. Therefore, the wooden formworkwill naturallydestruct and discard after repeating four to six times. But the remaining nail and chemicals treatment on the timber surface of the waste formwork always make the subsequent activity not easily. Such process does not echo todays trend of emphasis on the energy conservation and environmental protection. Besides, in order to keep the progress of the industry, all kinds of civil and construction industries are still continuous without considering the global temperature is getting warmer. But the timber,asaformwork rawmaterial,thespeedof deforestation is far behind the progress of forestation. Timber material will bedeforested somedaywith such vicious cycle. Therefore, if there is any appropriate material to replace wooden formwork, it will be a valuable issue for further research. The subject of this research is using value analysis to compare function and cost between plastic formwork plate and wooden formwork plate. For the study analysis, due to thelife cycleoftheplastic formwork plate andwooden formwork plate are notthe same, so this research developstheconceptoflife cost for doing the performance comparison between plastic formwork and wooden formwork with workability, cost, flat surface and environment. The study result shows the plastic formwork is full with potential to develop.

Abstract: A progressive damage method of predicting the fatigue life of mechanically fastened joints in fiber-reinforced plastics was established, which is integrated fatigue material property degradation models. The equations of virtual work based on the theory of time increment were deduced to analyze stress-strain states under fatigue loading conditions. The three-dimensional Hashin-type fatigue failure criteria were introduced into the method to detect damage for diverse damage modes. The criteria of the structure catastrophe and the sudden material property degradation rules including the correlation among four basic damage mechanisms were also established. A software module of progressive damage analyses for bolted composite laminates is compiled, which is convenient for the application in engineering. The fatigue life, failure initiation, propagation and catastrophic failure of composite bolted joints under tension-tension fatigue loading conditions are predicted by using the fatigue progressive damage method established in the paper. An excellent agreement is found between data obtained from this study and the experiment.

Abstract: The effect of volume fraction of SiC nanoparticles on the corrosion resistance of the SiC_p/Al metal matrix composites (MMCs) in 3.5 wt.% NaCl aqueous solution were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy. The results show that pitting susceptibility is about the same for the nanocomposites and the correspondingly unreinforced matrix metal Al, and the corrosion potentials of the MMCs are about 50 mV-60 mV more positive than that of the unreinforced Al, and is independent of the volume fraction of SiC nanoparticles. The corrosion resistance for the nanocomposite slightly decreases when the volume fraction increases due to both SiC nanoparticle agglomeration and promoting galvanic corrosion between SiC and Al.

Abstract: The poly (acrylic acid)/Bentonite composites (PAA/Bent) was prepared by in-situ polymerization. The structure of PAA/Bent was characterized by FT-IR, XRD and SEM, which indicated that AA intercalated into the interlayers of bentonite, and composite was formed between Bent and PAA. The PAA/Bent was used as a polymer adsorbent to remove methylene blue, a typical cationic dyes. Some important influencing factors on removing MB by PAA/Bent were investigated. The optimum adsorption conditions were obtained as following: the PAA/Bent dosage is 0.08 g, contacting 20 min at room temperature (25 °C), the pH value had little effect on MB adsorption, PAA/Bent can be used to treat wastewater with a broad range of pH value. The removal ratio of MB got to 99.4 %, and the adsorption capacity was 310.7 mgg-1. The removal mechanism is also investigated. It was charge neutralization and physical adsorption. In summary, the results indicated that PAA/Bent is an effective adsorbent and can be used to treat high concentration of MB wastewater.

Abstract: PBO fiber is the most excellent high performance fiber. But it is a kind of photosensitive material and is prone to degrade under ultraviolet (UV) radiation, which results in the changes of the fiber mechanical properties, finally affects the using of the material. In present paper, Titanium tetrabutoxide was used as solgel precursor of a nanosized TiO₂ coating to improve the photostability of PBO fibers. The nanosized TiO₂ coating was characterized by XRD. The influence of the coating on UV-durability of PBO was investigated by an accelerated UV-ageing method. Results of mechanical measurement showed that after exposing to UV light for 160 h, the fibers without TiO₂ coating degraded sharply, 7.01% of strength and 11.42% of break extension only remained, whereas 45.61% of strength and 68.56% of break extension still remained for the TiO₂ coated fibers. SEM analysis showed no significant surface morphological change on the coated fibers after the exposure, while some latitudinal crack fractures appeared on the uncoated PBO fibers.

Abstract: Mesoporous inorganic alumina with framework walls has been synthesized using a new and simple non-supercritical drying method. As a substitute solvent, hexamethyl disilylamine (HMDS) plays a definitive part for synthesis of the mesoporous alumina due to its special characters. The resulting alumina product shows high BET surface area, concentrated distribution of diameter and high porosity. The pore size distribution of alumina we prepared is concentrated around 11nm. Its structure still maintained stable and the BET surface area could reach up to 413.4593m²/g after being calcined at 800°C.

Abstract: Cellulose hydrogel was prepared by using the NaOH/ Thiourea/ H₂O as solvent system, cellulose aerogels were obtained by freeze-drying technology. The results showed that cellulose aerogel had porous network structure. Freeze-drying method was an effective way to prepare cellulose aerogel, and the volume shrinkage was 20.41%-28.36%. Bulk cellulose aerogel had low density, high porosity and fine mechanical strength. The density was low to 0.233g/cm³, and the porosity was up to 84.88%. The compressive strength was 5.7-8.2MPa. Cellulose aerogel had good heat insulation performance and thermal conductivity could be as low as 0.029 W/ (m·K). This work provided a foundation for the possibility of applying cellulose aerogels in the insulating material field.

Abstract: New macroporous carbons are prepared using phenolic resin foam as a carbon precursor. The synthesis scheme consisted of: (a) preparation of the phenolic resin foams, (b) carbonization of the phenolic resin foams. The synthesized phenolic resin foams were modificated by the hybrid SiO₂ nanomaterials for the first. The obtained macroporous carbons with better air tightness have potential application in catalyst support. Moreover, the shape of the macroporous carbons could be controlled by simply adjusting the phenolic resin foams.