Advanced Materials Research Vols. 1044-1045

Abstract: Helical monosubstituted polyacetylene@CdSe quantum dots (HPA@CdSe QDs) nanocomposites were fabricated by grafting helical HPA polymers onto the surface of semiconductor QDs through ester linkage. Optically active HPA derived from chiral serine was polymerized by a rhodium zwitterion catalyst, and evidently proved to adopt a predominately single-handed helical conformation. The HPA@QDs nanocomposites were characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The results indicate that the HPA matrix exhibits an enhancement in thermal stability after hybridization with CdSe QDs, while the QDs can maintain their original crystalline structure during the grafting process. The infrared emissivity property of the HPA@QDs nanocomposites at 8-14 μm was further investigated. These data demonstrated that the HPA@QDs composite film with doped CdSe QDs possesses an infrared emissivity value of 0.393, which was much lower than pristine HPA and QDs. This might be attributed to the incorporation of optically active helical HPA and semiconductor QDs in a hybrid phase and their strengthened interfacial interaction.

Abstract: Uniform and well-dispersed photoluminescent semiconductor ZnSe (zinc selenium) QDs (Quantum dots) were in-situ prepared stabilized by G4.0-NH₃⁺ PAMAM(polyamidoamine) dendrimers in methanol. The properties of ZnSe QDs encapsulated in PAMAM dendrimers were characterized by UV-Vis absorption spectra and photoluminescence (PL) emission spectra. The results were: ZnSe/PAMAM NCs (nanocomposites) with molar ratio 15 emitted strongest fluorescence.

Abstract: In this work, uniform mesoporous SnO₂ microspheres have been prepared via a facile and scalable method using tin tetrachloride pentahydrate (SnCl₄·5H₂O) and resorcinol-formaldehyde gel (RF gel) as starting materials. Furthermore, the structure and morphology of the as-prepared product were characterized by scanning electron microscope (SEM), Transmission electron microscope (TEM) and X-ray diffractometer (XRD). The results revealed that as-synthesized microspheres were around 500 nm in size and composed of large amount of SnO₂ nanoparticles with diameters of 10-20 nm. Gas sensors based on mesoporous SnO₂ microspheres were fabricated, and their gas sensing properties were tested for response to methane, butane, H₂ and CO gas. The sensor exhibited better sensitivity and selectivity to H₂ vapors at 300 °C than that of the conventional SnO₂ materials. The enhancement in gas sensing properties was attributed to their unique nanostructures.

Abstract: Teeth is the most hard tissue in human body, and its component contains over 96 wt.% inorganic mineral. When the teeth were destroyed by chewing, whiten, etched and friction, etc., ceramic materials are one of the most widely used materials for dental defect repairing or replacement [1-3]. Stress distribution of teeth is necessary to evaluate due to bearing the heavier load, especially the mandibular first molar. But its structure is so complex as not to measure the stress distribution accurately. With the development of CAD/CAM technology, some new technology and equipments occurrence may supply for good methods to evaluate the characteristics of complex structures [4-7]. Since Farah introduced a finite element analysis method into the field of oral medicine in 1973, the method was widely used to research the teeth mechanics, which is most suitable and efficient tools compared with other technologies [8]. In this paper, molar stress distributions were analyzed. By three-dimensional optical scanner and computer 3D design software such as solidworks, Geomagic Studio, CATIA V5, a molar model was built with accuracy and effectiveness, further the mechanical properties of ceramics denture was achieved.

Abstract: Plasma sheath that seriously impacts the propagation of electromagnetic waves will be produced when an aircraft flying in the atmosphere at very high speed. This thesis concentrates on the study of the attenuation characteristic of electromagnetic waves in plasma sheath. Through discussing the formation mechanism of plasma sheath and analyzing the propagation characteristic of electromagnetic waves, the scope of communication outage will be learned. The plasma sheath is segmented into plentiful subshells which are considered as uniform layers. Ultimately the factors which affect the attenuation of electromagnetic waves will be known.

Abstract: This paper comparatively study on fluidity, flexural strength, compressive strength and other mechanical properties of sisal fiber cement mortar and the base mortar. The results show that fluidity of sisal fiber makes sisal fiber cement mortar than that of the base group decreased about by 11.1%;When sisal fiber content is 4.5 kg/m³, water reducing agent is 2.78 kg/m³, the best mixing proportion of sisal fiber cement mortar for water: glue: sand = 0.45:1.:2.5, flexural strength improved by 52.4%, 54.3%, 20.1% respectively, compressive strength increased by-1.5%, 6.5% and-2.1%.And analyzed the mechanism of flexural and compressive from the chemistry of sisal fiber and cement.

Abstract: This work was a study of the preparation and properties of foam rubber from natural rubber ribbed smoked sheet 3 (RSS3) using synthesized salt of amino alcohol and carbonic acid as foaming agent. The synthesised salts were varied in the amount of 0.25, 0.4, 0.6, 0.8, 1, 3 and 5 phr to compare with 0.4 phr of the commercial foaming agent (azodicarbonamide). The foam rubbers prepared through conventional vulcanization with sulfur were compounded by using a two-roll mill and formed into cylinder by a compression molding machine at 170°C for 7 min. The specimens were characterized including compressive stress, shape deformation and cellular morphology. SEM micrographs showed that the pore or cell content in foam rubber is higher with increasing the amount of salt while cell shape is bigger and more shapeless. However, cell distribution is constancy for all conditions. For the mechanical properties, the compressive stress of foam rubber increases with incresing the salt up to 1 phr and then decreases as well as porosity increases. Whereas, the dimension of all foam rubbers is shrunk over time. Therefore, this study indicated that the synthesized salt of amino alcohol and carbonic acid could create the cells into rubber and provided the size and shape of cell and the good mechanical properties competitive with commercial foaming agent.

Abstract: In this paper, we report the experimental results on the synthesis of low-density tetraethoxysilane (TEOS)-based silica aerogels prepared under ambient pressure. The drying control chemical additive N, N-Dimethylformamide (DMF) was introduced to the experiments. Before dring, the water within alcogel was exchanged with ethanol and n-hexane. Trimethylchlorosilane (TMCS) was used to modify the hydrophilic gel surface to make sure the final aerogel is hydrophobic. The effects of solvent EtOH and DMF on the properties of the resulting aerogels were investigated. The microstructure, morphology and other properties of the aerogels were studied by FT-IR, TEM and BET measurement. The resulting aerogels have a well-developed mesoporous structure (mean pore size of ~15 nm) with low density (0.08g/cm³), a high specific surface area (1267m²/g) super hydrophobicity (Ө=165^o) and high transmissivity (~90%).

Abstract: A large amount of blast furnace slag, a by-product of the iron-making process, is generated annually. We attempted to convert blast furnace slag (BFS) into zeolitic materials using alkali fusion with ethylenediamine tetraacetate dihydrate (EDTA) chelation. Without addition of EDTA, a mixture of hydroxysodalite and calcite was synthesized. With EDTA addition, Ca²⁺ ions were trapped by chelation in solution during agitation, then the chelation was promoted by heating at synthesis, and zeolite-A, zeolite-X and hydroxysodalite were synthesized.

Abstract: To improve the compatibility of montmorillonite (MMT) with polymer. A kind of organic intercalation agent was applied in the intercalating organic modification of montmorillonite (OMMT) through ion exchange method, and a kind of silane coupling agent was further used to do the organic treatment. The SEBS/OMMTs composites were also prepared by melt blending. Structure and characterization of the modified MMTs were investigated by Fourier Transform infrared (FT-IR), wide angle X-ray diffraction (WAXRD), and the thermal stability were characterized by Thermogravimetric analysis (TGA). The dispersion status of MMTs were evaluated by scanning electron microscope (SEM) and the composites were tested by universal material testing machine. The FTIR results initial displayed that OMMTs had the absorption peak of organic functional groups. The XRD results showed that compared to Na⁺-MMT(1.47 nm), the layer spacing of H-OMMT increased to 3.27 nm, the above two results showed the organic modification of MMT had succeed. The results of TGA showed that OMMTs had a weight loss of organics. The SEM demonstrated that H-OMMT had the best dispersion status in SEBS matrix, and Na⁺-MMT was the worst.