Vol 2 , No 2 (Published)

DOI: http://dx.doi.org/10.18063/msmr.v2i2


Table of Contents

Original Research Articles

by Nguyen Phuc Quan 1,2, Tran Quoc Vinh 1, Kieu Thi My Yen 1, Le Vu Khanh Trang 2, Nguyen Minh Ly 2, Tran Cong Khanh 1
1518 Views, 294 PDF Downloads

The synthesis of silver nanoparticles (Ag NPs) has been carried out using different methods, mainly by biological and chemical methods; however, comparing antibacterial activity of Ag NPs synthesized by these methods has not been conducted before. In this study, silver nanoparticles (Ag NPs) were synthesized by methods using reducing agent NaBH4/carboxymethyl cellulose (CMC) and fungal strain Trichoderma asperellum (T.asperellum). The formation of silver nanoparticles was observed visually by color change and identified by Ultraviolet-visible (UV – vis) spectroscopy. The transmission electron microscopy (TEM) image illustrated almost nanoparticles with spherical shape and average diameter of 4.1 ± 0.2 nm and 2.1 ± 0.2 nm of samples produced from chemical reduction and biosynthesis respectively. Both samples after 180 days storing have been separated lightly, but the agglomeration and absorbance peak shifting were not observed which proved the high stability of synthesized Ag NPs. Antimicrobial activity against human bacterial pathogen Escherichia coli (E. coli) showed that the inhibition zone produced by “biosynthesis” and “chemical reduction” Ag NPs were 3.17 cm and 2.42 cm respectively. With nanoparticles size smaller than 2 mm, antibacterial activity of “biosynthesis” Ag NPs against E. coli was 31 % higher than “chemical reduction” Ag NPs, although the concentration of Ag NPs produced by biosynthesis was about 10-fold less.

Original Research Articles

by Bui Dai Phat 1, Tran Hong Huy 1, Cao Minh Thi 2, Pham Van Viet 1
422 Views, 174 PDF Downloads

In this study, TiO2 nanotubes (TNTs) were synthesized via a hydrothermal process and characterized by high-resolution transmission electron microscopy (HR-TEM) images, selected area electron diffraction (SAED) pattern, and photoluminescence (PL) analysis. The NO removal photocatalytic activity of the hydrothermally synthesizedTNTs was surveyed systematically. The hydrothermally synthesizedTNTs have shown an efficient NO photodegradation which is approximately 4 times higher than that of P25 and an excellent photostability under visible light after 5 cycles. Furthermore, reactive radicals mainly involved in the photocatalytic reaction were identified by electron spin resonance (ESR) study, leading to a better understanding of the photocatalytic mechanism of the hydrothermally synthesized TNTs. 

Original Research Articles

by O. G. Edema1, O. M. Osiele2, S. I. Otobo1, A. O. Akinbolusere1
246 Views, 132 PDF Downloads

In this paper the modified Landau theory of Fermi Liquids was used to compute the thermal expansion and thermal conductivity of quasi-particles in metals. The result revealed that as temperature increases the thermal expansion of quasi-particles in metals increases in all the metals investigated. It is also observed that as the electron density parameter increases the thermal expansion of quasi-particles increases. This shows that at low density region the thermal expansion of quasi-particles is large.  The result obtained for the thermal conductivity of quasi-particles in metals revealed that for all the metals computed the thermal conductivity of quasi-particles decreases as temperature increases. This seems to suggest that as temperature increases the separation between quasi-particles increases because they are not heavy particles hence, the rate of absorbing heat decreases. The computed thermal expansion and thermal conductivity of quasi-particles are in better agreement with experimental values. This suggests that the introduction of the electron density parameter is promising in predicting the contribution of quasi-particles to the bulk properties of metals. This study revealed the extent to which quasi-particles contribute to the bulk properties of metals, which assisted their potential applications in materials science and engineering development.

Original Research Articles

by Patrice BERTHOD, Zahra Himeur, Lydia Toubal, Ouarda Abed, Mélissa Léglise
375 Views, 170 PDF Downloads

Many of the cast superalloys chosen for specific applications at high temperatures, such as tools devoted for shaping molten glass, are based on nickel or cobalt. They contain chromium and carbon to achieve good resistances against both mechanical stresses and hot oxidation/corrosion, by favoring the formation of reinforcing carbides at solidification and the development of a protective oxide scale of chromia during service. In presence of tantalum or titanium in the chemical composition of the alloys, high performance MC carbides may be obtained but this depends on the base element. One recently observed how the respective proportions of nickel, cobalt and chromium may promote the formation of TiC or TaC at the expense of chromium carbides. The ratings chosen for No, Co and Cr may have high influence on the oxidation of the alloys at high temperature this is what was studied in this work.

Original Research Articles

by Lei Che1,2, Wenlei Sun1, Guan Zhang1,3, Jiaxin Han1
374 Views, 227 PDF Downloads
Laser cladding technology is highly suitable for the remanufacturing of thin-walled and easily deformable parts due to its concentrated energy density. Due to the high temperature and high pressure corrosion environment, the valve sealing surface is prone to corrosion, wear and other failures. A nickel-based tungsten carbide alloy layer was prepared on the valve sealing surface substrate material by laser cladding process. By designing orthogonal experiments, the effects of laser power (P), scanning speed (Vb), powder feeding rate (Vf), and WC content (wt%) on the alloy layer were investigated. A fuzzy comprehensive evaluation method including macroscopic quality, microstructure, microhardness, anti-wear performance, oxidation resistance, compactness and corrosion resistance was proposed. The experimental results showed that the hardness, oxidation resistance and corrosion resistance of the laser alloy layer are significantly improved compared with the matrix; the optimum process parameters and the addition ratio of WC powder are laser power (P) of 1.1 kW and scanning speed (Vb) of 800 mm/min. The powder feeding rate (Vf) was 20%, and the WC content was 20% by weight.