Papers by Keyword: Morphology

Abstract: To clarify the relationship between the glandular density and the glandular trichome secretion content of different varieties of flue-cured tobacco,the trichome density of 5 kinds of flue-cured tobacco species was analyzed by electron microscope,and glandular secretion was analyzed by GC/MS.The results showed that:the trichome density of flue-cured tobacco is not proportional with the content of glandular secretions,and the morphology of glandular trichome were approximately same in five tobacco varieties.The content of cembrenoids are the highest in the glandular trichome secretion components of flue-cured tobacco,which is the main ingredient.Through regulating metabolism terpenoids to improve diterpene content is the key element to improve the content of tobacco glandular secretions.

Abstract: The radial sand ridges located in the southern Yellow Sea off the Jiangsu coast, are unique sand ridges. They are characterized by radical current field and radical arrangement. The formation and maintenance mechanism of the radial sand ridges have always been a focus of attention of scholars for a long time. The formation is related to the unique convergent-divergent tidal currents. In this paper, a numerical model is constructed to answer the two following questions. Firstly, can the radial sand ridges be formed with radical tidal current field Secondly, can this be simulated by a numerical model The radial tidal current can shape the radial sand ridges. Numerical simulations show that the radial sand ridges can be formed on present radical tidal current field and the formation and evolution of the radial sand ridges can be simulated by a numerical model.

Abstract: This paper investigates the effects of polysaccharide additive agent on the morphological and thermal properties of thermosetting polymer. The weight percentage (wt%) of Diglycidyl Ether of Bisphenol A (DGEBA) epoxy resin to Hexamethylenediamine (HMDA) hardener were kept constant while a varying wt% of chitosan, ranging from 0 to 10 wt% was introduced. The chitosan filled epoxy hardener mixture was allowed to cure at 40°C for a period of 12 hours. Dynamic Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were conducted on the specimens to analyse the effects of chitosan loading on thermal stability and transition temperature while Atomic Force Microscopy (AFM) was used to investigate the changes to its morphological property. At chitosan loading of 2.5 wt% and below, good dispersion of the additive was observed. Apparent agglomeration and phase separation were formed when chitosan content increases above 7.5 wt%. The formation of bulky chitosan agglomeration was found capable of enhancing the thermal stability of the thermoset polymer. The diamine acted as the co-reactants with DGEBA as well as spacer which decrease the effect of material brittleness due to addition of chitosan.

Abstract: Polyimide-Al₂O₃ nanocomposite films were prepared via simple mechanical blending of Polyimide and surface modified Al₂O₃, and Polyimide-TiO₂ nanocomposite films were prepared by the polymerization process of adding tetrabutyl orthotitanate (TBOT) and the coupling agent isocyanatopropyltriethoxysilane (ICTOS) in polyimide. The three layers nanocomposite films were characterized by scanning electron microscope (SEM). The homogeneous dispersion is observed by the SEM when the concentration of Al₂O₃ is low. The electrical properties of the nanocomposite films were investigated as a function of the concentration of the Al₂O₃ nanoparticles. The results show that the dielectric constant and the dielectric loss (tan δ) of these films increased with the increase of the content of silica particles.

Abstract: Polyimide nanocomposite insulating materials are widely used in electrical and electron engineering owing to their outstanding electrical, mechanical, thermal, and wear-resistance properties. Polyimide/silica (PI/SiO₂) nanocomposites have been prepared by the polymerization process of adding tetraethoxysilane (TEOS) and the coupling agent isocyanatopropyltriethoxysilane (ICTOS) in polyimide. The effects of SiO₂ addition on the microstructure and the dielectric property of nanocomposite films were investigated. It was found that the silica particles were well dispersed in PI matrix and the sizes of SiO₂ particles in the hybrid films range from 20 nm to 30 nm for 5-15 wt% SiO₂ loading in the matrix. The dielectric constant and the dielectric loss (tan δ) of these films increased with the increase of the content of silica particles.

Abstract: Polyimide (PI) films filled with K0.5Na0.5NbO3 particles at different weight 0wt%,5wt%,10wt%,15wt% and 20wt% had been prepared by in-situ dispersion polymerization process in this article. then we measured morphology and dielectric properties. when the mass fraction of KNN reach 20%, its dielectric constant achieve 4.9(100Hz) with the dielectric loss tangent value is less than 0.025 (100 Hz).it Shows the good insulating properties.

Abstract: Calcium carbonate (CaCO₃) was mineralized in N,N-dimethylformamide (DMF)-H₂O mixed solvents in the presence of polystyrene-b-poly (vinyl pyrrolidone) (PS-b-PNVP) block copolymer. The morphologies of PS-b-PNVP micelles and CaCO₃ crystals were characterized by TEM and SEM. By varying the volume ratio of DMF-H₂O, the CaCO₃ crystals with different morphologies and phases were obtained. It was convinced that the morphology of crew cut micelles played a key role in the morphological formation of CaCO₃.

Abstract: In this study, PVDF membranes were prepared by solution-cast method. The effects of evaporation temperature on the morphology, polymorph and mechanical properties of such prepared membranes were studied. It was found that perfect spherulites were observed in the solution-cast membranes. FESEM photomicrographs of the membranes showed dense structure. PVDF mainly crystallized into α phase. In the solution-cast process, the spherulite size increased as evaporation temperature was increased from 120 °C to 150 °C, when the evaporation temperature was 165 °C, spherulite size decreased. And the tensile strength increased with the decrease in spherulite size.

Abstract: Polysulfone (PSf) membrane is catogorized as hydrophobic membrane that easily fouled during membrane operation process. The presence of second hydrophilic polymer which added into membrane casting solutions plays a crucial role in adjusting the membrane properties. This hydrophilic polymer was employed in hydrophobic polymer membranes in order to improve hydrophilicity and performance as well as formed antifouling ultrafiltration (UF) membranes. In this study, a hydrophilic polymer, cellulose acetate phthalate (CAP) was added into polysulfone (PSf) membrane casting solutions by blending technique to produce PSf/CAP blend membranes. Flat sheet asymmetric PSf/CAP blend membranes were prepared by wet phase inversion method. The results revealed that an increase in CAP increased the hydrophilicity properties of PSf/CAP blend membranes compared to pure PSf membrane. The significant changes in size and numbers of microvoids and macrovoids in the morphological structures of PSf/CAP blend membranes were due to CAP promote the instantaneous liquid-liquid demixing during phase inversion process.

Abstract: Membranes can be defined as a barrier that separates two phases and is widely applied in industrial separation processes. The development of membrane separation processes (PSM) has the major advantage of phase change without separation of components, besides selectivity and simplicity of operation. The addition of mineral fillers in polymers is intended for the cost reduction and increase in rigidity of the materials. When these loads have sizes of nanometric dimensions, this system is called nanocomposites, which exhibit improved properties compared to the pure polymers or conventional composites. Microporous membranes were obtained from polyamide 6.6 nanocomposites of varying amounts of regional montmorillonite clay through the immersion-precipitation process. In general, the membranes showed a filter skin, which contains very small pores and a porous layer, with variations in microstructure, detected by scanning electron microscopy (SEM).