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991.
Muhammad Saif Ullah Khan Zareen Akhter Touseef Naz Arshad Saleem Bhatti Humaira M Siddiqi Mohammad Siddiq Abbas Khan 《Polymer International》2013,62(2):319-334
Some novel ferrocene‐containing polyamide‐based block copolymer materials with telechelic polydimethylsiloxane oligomer and their organic analogues were prepared by solution‐phase polycondensation of ferrocene‐based organometallic and terephthaloyl‐ as well as isophthaloyl‐based organic acyl chlorides with a series of semi‐aromatic diamines having ether linkages together with variable aliphatic character. The corresponding polyamides of the synthesized materials, without polydimethylsiloxane segment, were also prepared for comparison of physicochemical properties. None of the synthesized organometallic and organic block copolymers along with their respective polyamides melted below 300 °C and their structural features were confirmed by their physical properties and spectroscopic studies. The weight‐average molecular weights and molecular parameters of all these materials were determined by the static laser light scattering technique. The materials were soluble in sulfuric acid and partially soluble in common organic solvents, and yet became readily soluble upon N‐trifluoroacetylation. The synthesized materials were further characterized by their water absorption characteristics, X‐ray diffraction studies and surface morphology (SEM and AFM) and thermal (DSC and TG) analyses, and their structure–property relationships were elucidated from these studies. The energies of pyrolysis for these materials were calculated by the Horowitz and Metzger method. © 2012 Society of Chemical Industry 相似文献
992.
The thermomechanical fracture and interface delamination of thermal barrier coatings (TBCs) in a high-heat-flux environment is the result of large surface temperature and thermal gradient across the coating thickness and the resulting viscoplastic deformations induced in the ceramic material. The maximum coating surface temperature has been used as the key loading parameter in previous studies. The current study explores the effects of several other thermal loading parameters on thermomechanical response and fracture behavior of TBCs with or without preexisting surface cracks. Results show that for a constant maximum surface temperature, the thermal fracture of the coating is increased by (i) an increased temperature difference across the coating, (ii) longer heating duration, and (iii) more aggressive coating surface cooling after heating. These results provide insights into TBC thermal fracture mechanisms and can potentially improve the design of the morphology of preexisting cracks in the coating to reduce fatal interface fracture. 相似文献
993.
The spherulitic structure and morphology of poly(3‐hydroxybutyrate) (PHB) thin films crystallized from the melt were observed with a polarizing optical microscope. Depending on the thickness of the PHB thin film and crystallization temperature, banded and nonbanded spherulites could form. Reducing the thin‐film thickness and crystallization temperature was favorable for the formation of the banded structure. The morphology transition from banded spherulites to nonbanded spherulites was related to the ratio of the crystallization rate to the diffusion rate. The formation mechanism of the banded structure was examined with the discontinuity growth theory. A depletion zone was considered to appear periodically at the crystal growth front because of the slow diffusion rate, and this may have resulted in the banded spherulites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
994.
Polyacrylonitrile nascent fibers were prepared via the wet-spinning technique and a dimethyl sulphoxide/H2O coagulation bath system was adopted. The objective of this study was to investigate the influence of dope extrusion rates
on formation and characterization of nascent fibers. Nine different dope extrusion rates were adopted when other technique
parameters were kept steady. The surface morphology of nascent fibers was observed by field emission scanning electron microscopy.
The results showed that the dope extrusion rates played significant effects on the cross-section structure, surface morphology,
degree of crystallization, and sound velocity of the nascent fibers. With an increase of dope extrusion rate, the surface
roughness increased, and the sound velocity had a point of inflexion. Moreover, the degree of crystallization had a maximum
when the dope extrusion rate was 5.92 m/min. 相似文献
995.
水玻璃激发矿渣制备纳米地质聚合物研究 总被引:1,自引:0,他引:1
采用扫描电镜(SEM)、结合能量散射X-射线能谱分析(EDXA)、场发射扫描电镜(FESEM),对水玻璃激发矿渣细粉水化产物的生成及发展进程中的微观形貌进行了系统的研究.在水化早期,矿渣玻璃体快速解体,形成大量的硅溶胶和铝溶胶覆盖于矿渣表面;随着龄期的延长,硅铝溶胶之间发生缩聚反应,生成相互搭接的树枝状网络结构的地质聚合物凝胶体,表明矿渣玻璃体的解体是一个形成溶胶的过程.而缩聚反应是一个形成凝胶的胶凝过程.纳米地质聚合物结构密实,抗压强度从1d的26.5MPa增至28d的60.IMPa.地质聚合物是由20nm左右的颗粒搭建成的网络结构所组成. 相似文献
996.
Polypyrrole (PPy) was prepared from different mixed‐surfactant solutions with ammonium persulfate as an oxidant. Three types of combinations were selected, including cationic/anionic, cationic/nonionic, and anionic/nonionic mixed‐surfactant solutions. The surfactants used in the experiments included cetyltrimethylammonium bromide (cationic surfactant), sodium dodecyl sulfate (anionic surfactant), sodium dodecyl sulfonic acid salt (anionic surfactant), poly(vinyl pyrrolidone) (nonionic surfactant), and poly(ethylene glycol) (nonionic surfactant). The morphology, structure, and conductivity of the resulting PPy were investigated in detail with scanning electron microscopy, Fourier transform infrared spectra, and the typical four‐probe method, respectively. The results showed that the interaction between the different surfactants and the interaction between the surfactants and the polymer influenced the morphology, structure, and conductivity of the resulting polymer to different degrees. The cationic surfactant favored the formation of nanofibers, the addition of anionic surfactants produced agglomeration but enhanced the doping level and conductivity, and the presence of a nonionic surfactant weakened the interaction between the other surfactant and the polymer in the system. In comparison with the results for monosurfactant solutions, the polymerization of pyrrole in mixed‐surfactant solutions could modulate the morphologies of PPy, which ranged from nanofibers of different lengths to nanoparticles showing various states of aggregation. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1987–1996, 2007 相似文献
997.
A discussion about phase morphology and interphase is presented taking into account the influence of the epoxidation on NR/SBR blends. Unfilled blends were examined in a broad composition range to investigate the morphology by TEM (transmission electron microscopy) and to estimate the volume fraction of the interphase by means of DMA (dynamic mechanical analysis). It was observed that the domain sizes and the volume fraction of the interphase depend on the difference in polarity of rubbers caused by the presence of the epoxidized phase and the polarizability caused by the difference on the vinyl content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2377–2384, 2007 相似文献
998.
Nylon 11 samples were filled with metal (Zn) fillers of two different concentrations (1 and 5% w/w) each. The samples in the form of disc were obtained by using hot press molder. The structural properties have been investigated using density measurement and wide angle X‐ray diffraction (WAXD) technique. The morphology of pure and Zn‐filled samples has been studied using scanning electron microscopy. Glass transition (Tg) temperature was determined using dynamic mechanical thermal analyzer (DMTA). The result shows that there is slight crystal modification due to the addition of metal fillers (Zn), and the crystallinity has improved. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3094–3098, 2007 相似文献
999.
M. M. Abou-Krisha F. H. Assaf S. A. El-Naby 《Journal of Coatings Technology and Research》2009,6(3):391-399
The present work is directed at collecting the properties of Zn–Ni and Zn–Fe alloys in one alloy via the electrodeposition
of Zn–Ni–Fe ternary alloy. Electrodeposition of ternary Zn–Ni–Fe alloy was investigated and compared with the characteristics
of Zn–Ni electrodeposits. The electrodeposition was performed from a sulfate bath onto a steel substrate. Structural analysis
by X-ray diffraction (XRD) method revealed that the Zn–Ni–Fe alloys consisted of a mixture of zinc, and (γ-Ni2Zn11) and (Fe3Ni2) phases. The study was carried out using electrochemical methods such as cyclic voltammetry and galvanostatic for electrodeposition,
while anodic linear polarization resistance and anodic linear sweeping voltammetry techniques were used for the corrosion
study. Surface morphology and chemical composition of the deposits were also examined by using scanning electron microscopy
and atomic absorption spectroscopy, respectively. It was found that the obtained Zn–Ni–Fe alloy exhibited more preferred surface
appearance and better corrosion resistance without adding any organic brighteners to the plating bath in comparison to Zn–Ni
alloy that electrodeposited at similar conditions. Results obtained revealed that the increase in corrosion resistance of
ternary deposits is not only attributed to the formation of (γ-Ni2Zn11) phase, but also to iron codeposition and formation of (Fe3Ni2) phase. 相似文献
1000.