Key Engineering Materials Vols. 602-603

Abstract: Layered Molybdenum trioxide M_OO₃, with a two-dimensional (2D) structure was successfully delaminated into colloidal nanosheets in n-butanol via a soft-chemical process involving intercalation of dodecylamine. X-ray diffration (XRD) showd that: after intercalation spacing of the layered material expend from 1.38nm to 2.69nm. Furthermore, stable nanosheet sol was obtained after exfoliation under ultrasonic condition, Characterizations by transmission electron microscopy (TEM) and scan electron microscopy (SEM) confirmed the formation of unilamellar 2D nanosheet crystallites with an average lateral size of 400 nm, those also suggests that the samples we got is Lamellar structured. Selected Area Electron Diffraction (SEDA) indicates that the obtained nanosheets were crystalline. And the obtained nanosheets exhibited photo-catalytic decolorization properties. Which was evaluated by monitoring the degradation of Methylene Blue, after 40 minutes 90% methylene blue was degradated.

Abstract: Hollow-spherical WO₃ nanocrystals were obtained by calcining an organic-inorganic W-C precursor containing C and W in a microwave oven or in a conventional muffle furnace, and the W-C precursor hybrid precursor was synthesized via a hydrothermal method. The samples were characterized by XRD, TG-DTA, FTIR and SEM. The morphologies of the WO₃ samples obtained by conventionally heating (C-WO₃) and microwave-assisted heating (M-WO₃) were compared. The average diameter and shell thickness of C-WO₃ hollow spheres is about 450 and 200 nm, respectively. The average diameter and shell thickness of M-WO₃ hollow spheres is about 500 and 50 nm, respectively. The M-WO₃ has a loose and multilayered shell, and their nanoparticles are smaller than those of C-WO₃. The improved structure of M-WO₃ is due to shorter heating time and the unique heating style in a microwave oven. The gas-sensing performances of the WO₃ sensors were investigated. The M-WO₃ sensor has better response to ethanol vapors than the C-WO₃.

Abstract: WO₃ has been widely applied in many fields such as electrochromic window, photocatalyst, and gas-senor. In this paper, WO₃/S core/shell nanoparticles were synthesized in high density and large scale on silicon substrates via simple thermal evaporation of WO₃ and S powders at 950 °C in a tube furnace. The morphology, composition and structure of the nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, and energy dispersive X-ray spectroscopy. The results indicate that the nano-particles have a uniform morphology with a diameter in the range of 150-250 nm and well crystalline structure. The growth mechanism of the nanoparticles was also proposed.

Abstract: To develop a kind of gastrointestinal timed-release preparation for Metoprolol Tartrate, nanostructured silica particles were chose for the purpose. Briefly, MCM-41 type mesoporous silica nanospheres with a size of 100-200 nm were synthesized through the reaction of tetraethyl orthosilicate (TEOS) in the water medium at 353 K, with introducing some cetyltrimethyl ammonium bromide (CTAB) as porogens. Various analytical methods, including FT-IR, XRD, TEM, N₂ physisorption and thermal analysis, were applied to characterize the final products. Metoprolol Tartrate was then loaded into the mesoporous silica nanospheres by soaking. Results of the release of the drug in simulated gastric juice indicated that the drug can release up to 24 h and its maximum released amount was 4.5%. In the simulated intestinal juice the maximum cumulative released amount of metorprolol was 10.8%.In vitro release behavior revealed that the mesoporous silica were appropriate used as drug delivery system.

Abstract: In this paper, the monodisperse TiO₂ particles and TiO₂ coated SiO₂ core-shell particles were prepared by the method of microemulsion, and the phase and morphology of TiO₂ and TiO₂ coated SiO₂ core-shell structure particles were analyzed by using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). At the same time, the phase changes and morphology changes of the two different kinds of structural particles as the changes of sintering temperature were compared. The results show that when the TiO₂ particles were prepared by the method of microemulsion, the content of anatase TiO₂ decreased gradually and the rutile TiO₂ increased gradually as the sintering temperature increases from 550 °C to 650 °C; the core-shell particles of TiO₂ coated SiO₂ prepared were anatase when the sintering temperature increases from 600 °C to 800 °C; all of the particles size were about 1μm, the monodispersity of the particles were optimal and the particles were coated evenly, smoothly. Keywords: TiO₂; SiO₂; core-shell structure

Abstract: A kind of new hollow silica microspheres were proposed in experiment, which are fabricatted by a fast hydrolysis and condensation of tetraethyl orthosilicate taking place around multi-lamellar octylamine vesicles. The morphology of the vesicles is then fixed by a quick gelation process, resulting in hollow organo-silica spheres. After the removal of the template by calcination, nanopores are formed in the hollow shells. The results show that the synthesized hollow silica microspheres have smooth surface and dispersed well£®There are bimodal nanopores in the hollow silica microspheres, with a diameter of 2.1 nm and 0.62nm for the mesopores and micropores respectively, giving a specific surface area of 1123m² /g and a pore volume of 0.6291mL/g£®

Abstract: Mesoporous silica nanoparticles (MSNs) is an attractive candidate as a drug delivery carrier due to their large surface area, high pore volume and t intrinsic biocompatibility. Here, MSNs were synthesized by the hydrolysis and condensation of tetraethyl orthosilicate (TEOS) with cetyltrimethylammonium bromide (CTAB) acting as structural directing agent. A large mesopore with diameter of 3.8 to 5.5 nm of MCM-41style can be obtained via the addition of 1,3,5-trimethylbenzene. Metoprolol tartrate as a selective β1 receptor blocker was embedded on MSNs by the incipient wetness impregnation. The delivery profiles were collected in vitro in SBF at pH 7.4. A close correlation can be observed between the drug release kinetic and the mesopore size and specific surface area of MSNs.

Abstract: Zeolite P was synthesized for hydrothermal route at crystallization temperature of 95°C and crystallization time of 7h, using“acid-treated stellerite-NaOH-NaAlO₂-H₂O” as precursor, with different molar ratios n (SiO₂/Al₂O₃), n (Na₂O/SiO₂) and n (H₂O/Na₂O). The as-fabricated samples were characterized by scanning electron microscopy, X-ray diffraction, FT-IR techniques. The result shows that: the crystal structure of zeolite P has been determined in the tetragonal crystal system, lattice constants are 10.049Å,10.047 Å and the crystallinity of zeolite P is 97%. Influences of synthetic parameters were investigated systematically to achieve high quality pure zeolite P phases. Moreover, this morphology and high crystallinity control approach might be further extended to the synthesis of other zeolite and used in industry, agriculture, environmental protection and biotechnology industries.

Abstract: To obtain low-Si/Al-ratio geopolymers and overcome the disadvantage of impure raw materials, amorphous Al₂O₃-SiO₂ powder was first prepared using a sol-gel method in accordance with specially designed chemical compositions. The composition of the geopolymers was designed according to the NaA zeolite composition (Si/Al/Na atom ratio is 1:1:1), and the zeolite crystal structure was obtained by geopolymers with high Na/Al ratios through hydrothermal processing at 90oC for 6 h. The geopolymers with Si/Al ratios ranging from 0.9 to 1.05 exhibited amorphous structures after being cured at 60oC for 24 h; however, the geopolymer sample with a Si/Al ratio of 1.1 exhibited crystallization. After the hydrothermal treatment of these geopolymers , the XRD, SEM and NMR results show that the phase structure of the geopolymers may transform into a crystalline structure under appropriate compositions and external conditions. Hence, the alkalinity, Si/Al ratio and hydrothermal conditions determined the crystallinity of the geopolymers that were synthesized.

Abstract: In this work, the geopolymer based inorganic membranes, as a kind of new inorganic membranes, were synthesized with water-glass, metakaolin and deionized water. The resulting membranes were characterized by SEM, water flux and pore size. The results show that the membranes have high strength and water flux when these membranes were fabricated under the preparation condition: water-glass modulus of 1.1, Na/Al molar ratio of 0.8 and H₂O/Na₂O molar ratio of 18. Keywords:Geopolymer; Inorganic membranes; Preparation; Characterization