ASEAN Journal on Science and Technology for Development

Influence of Nitrogen Gas Flow Rate on the Microstructural and Mechanical Properties of Tin Deposited Carbon Steel Synthesized by CAE PVD Technique

A Mubarak, E Hamzah, MRM Toff — Tue, 29 Apr 2008 05:14:21 +0700

This paper reports on the preparation of titanium nitride (TiN) thin films on carbon steel plates, using cathodic arc evaporation CAE PVD technique. We studied and discussed the effect of various nitrogen gas flow rates on microstructural and mechanical properties of TiN-coated carbon steel plates. The coating properties investigated in this work included the surface morphology, thickness of deposited coating, adhesion between the coating and substrate, coating composition, coating crystallography, hardness and surface characterization using a field emission scanning electron microscope (FE-SEM) with energy dispersive X-ray (EDX), Xray diffraction (XRD) with glazing incidence angle (GIA) technique, scratch tester, hardness testing machine, surface roughness tester and atomic force microscope (AFM). SEM analyses showed that all the films had columnar and dense structures with clearly defined substrate-film interfacial layers. The hardness of TiN-coated carbon steel was noted six times more than the hardness of uncoated one. An increase in nitrogen gas flow rate showed; decrease in the formation of macro-droplets, average roughness (Ra) and root-mean-square (RMS) values in CAE PVD technique. During XRD-GIA studies, it was observed that by increasing the nitrogen gas flow rate, the main peak [1,1,1] shifted toward the lower angular position. Microhardness of TiN-coated carbon steel showed about six times increase in hardness than the uncoated one. Scratch tester results showed an average adhesion between the coating material and substrate. Thanks to the high resolution power could be observed that by increasing nitrogen gas flow rate there was percentage increase in the bearing ratio while percentage decrease in histogram. Keywords: TiN, PVD, carbon steel, microstructure, hardness, surface roughness, adhesion AJSTD Vol. 23 Issue 4 pp. 239-251 (2006)

A New Triterpene Glycoside from the Sea Cucumber Holothuria Scabra Collected in Vietnam

Tue, 29 Apr 2008 05:40:15 +0700

Bioassay guided fractionation led to the isolation of a new triterpene glycoside, holothurinogenin B (1) along with three known compounds, holothurin B (2), holothurin A (3), and holothurin A₂ (4), from the methanol extract of the Vietnamese sea cucumber Holothuria scabra. Their structures were deduced from the spectral analysis (1D-NMR, 2D-NMR, MS) and chemical evidences. Keywords: Triterpene glycosides, Sea cucumber, Holothuria scabra, Holothurinogenin B. AJSTD Vol. 23 Issue 4 pp. 253-260 (2006)

Characteristics of Solid-State Calcium Ion Sensors Based on Photocurableand Selfplasticising Polyacrylate Matrices

Lee Yook Heng, Elizabeth AH Hall — Tue, 29 Apr 2008 06:28:38 +0700

New membrane materials based on cross-linked poly(n-butyl acrylate) (nBA), have been used successfully as calcium ion-selective membranes. These membrane materials possess selfplasticising property and hence do not require plasticisers. The photocurability and good adhesion characteristics of these polymer matrices enable workable solid-state calcium ion sensors to be fabricated by simple photocure procedures employing the calcium ionophore ETH5234 and a lipophilic additive as ion sensing components. The calcium ion-selectivity of the sensors can be controlled by varying the chemical composition of the photocured membrane. An optimum amount of the cross-linker 2,2-hexanedioldiacrylate (HDDA) and the incorporation of n-heptyl acrylate (nHA) led to improvement in the calcium ion-selectivity. The best calcium ion-selectivity was obtained from a copolymer membrane with composition: nBA = 74 wt-%, nHA = 20 wt-% and HDDA = 0.1 wt-%. The selectivity coefficients of calcium over major cations were: LogK_{Ca Na}^Pot, = -4.4, LogK_{Ca K}^Pot, = -3.6, Log _{Ca Li}^Pot = -5.9, LogK_{Ca Mg}^Pot , = -4.4 with a Nernstian slope (29.1 ± 0.8 mV/decade) under buffered conditions. This potentiometric performance is comparable to other solid-state calcium ion sensors with various plasticised polymer membranes. AJSTD Vol. 23 Issue 4 pp. 261-273 (2006)

Development of a Tunable Ultrashort Dye Laser System by Using Molecular Photonic Processes and a Nanosecond Pumping Laser

Tue, 29 Apr 2008 06:36:15 +0700

The paper presents the physical processes and operational characteristics of an original subpicosecond dye laser system which is designed and successfully developed at our laboratory basing on the combination use of three photonic processes of dye molecules: 1) Fast spectrotemporal evolutions in the broadband dye laser emissions; 2) Generation of a chain of ultrashort pulses (spikes) from low-Q micro-cavity dye lasers; and 3) Non-linear resonant interaction between ultrashort laser pulses and highly-saturated dye media. Such a laser system provides a stable generation of single 500 fs pulses with a peak power of 300 MW at 606 nm. Particularly, the whole sub-picosecond laser system is pumped by a single nanosecond laser (Q-switched Nd:YAG laser). The spectral and time processes involved in these pulse-shortening methods are analyzed with a rate-equation model extended to wavelengths. A white light continuum generation was obtained by focusing the 500 fs pulses into 2 cm water cell. As a result, it enables us to produce widely tunable ultrashort laser pulses with a spectral selection and amplification of the supercontinuum spectrum. AJSTD Vol. 23 Issue 4 pp. 275-284 (2006)

Synthesis and Characterization of Pure-Silicazeolite- Beta Membrane

Yeong Yin Fong, Subhash Bhatia, Subhash Bhatia — Tue, 29 Apr 2008 06:54:04 +0700

The semiconductor industry needs low dielectric constant (low k-value) materials to more advance microprocessor and chips by reducing the size of the device features. In fabricate this context, a new material with lower k value than conventional silica ( k = 3.9 - 4.2 ) is needed in order to improve the circuit performance. As per the recent International Semiconductor Technology plan, a low-k material with a k = 1.6 will be needed by 2010. The choice of the inorganic zeolite membrane is an attractive option for low k material and suitable for microprocess application. In the present study, a pure silica zeolite beta membrane coated on the non-porous stainless steel support was synthesized using in situ crystallization of a gel with the composition of SiO₂ : 0.6 TEAOH : 0.6 HF : 10.1 H₂O. The crystallization was carried in the presence of tetraethylammonium hydroxide TEA(OH) as structure directing agent, fumed silica, HF and deionized water at pH value of 9. The crystallization under hydrothermal conditions at 130°C was carried out for the time period of 14 days. The membrane was characterized by X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Nitrogen Adsorption and Scanning Electron Microscope (SEM). SEM micrographs show highly crystalline, truncated square bipyramidal morphology of pure silica zeolite beta was coated on the non-porous stainless steel support. The membrane dielectric constant, k-value was measured as 2.64 which makes it suitable for the microprocessor applications. Keywords: Zeolite membrane, zeolite BETA and microprocessor AJSTD Vol. 23 Issue 4 pp. 285-293 (2006)

The Safety of Building Structures Subject to Unusual Natural and Man-Made Disasters

Nguyen Van Pho, Nguyen Dinh Xan — Tue, 29 Apr 2008 07:59:11 +0700

Previously, we often use the statistical data on natural disasters and mathematical tools such as probabilistic theory, mathematical statistics and random processes to express and analyze natural disasters' phenomena when dealing with the safety problem of building structures subject to natural disasters. However, due to unusual change of the global climate, natural disasters have changed essentially the intensity, frequency and the appearing time so we cannot rely on the statistical data on natural disasters in the past to do that. Therefore, renovation of the thought on selection of plans, calculation, design, and evaluation of safety of building structures to accommodate to natural disasters and man-made disasters is a required task. This paper presents some points of view of the authors, including: (i) Why should we renovate our thought on selection of plans, calculation, design, and evaluation of safety of existing structures? (ii) What are the old thought and the new thought on the safety of building structures? (iii) How to renovate the selection of building plan, calculation, design and evaluation of the safety of building structures? and (iv) How were some building structures in Vietnam decided according to the new thought? Some specific examples on the selection of building plan given in this paper are to illustrate the authors' opinions. AJSTD Vol. 23 Issue 4 pp. 295-306 (2006)

Metal Composites Behaviour under Biaxial Stresses

J Jai, MN Berhan — Tue, 29 Apr 2008 08:09:56 +0700

For this study, different volume fraction (vol.%) of particulate alumina (Al2O3) reinforced aluminium alloy (Al 6061) with 5 vol.%, 15 vol.% and 25 vol.% are produced by powder metallurgy method. These samples were subjected to biaxial stresses in order to investigate the behaviour of the metal matrix composites (MMCs). Microstructure analysis on the individual sample before and after loading was performed under scanning electron microscopy. The small particles of 2 μm in size have exhibited strong interfacial bonding with the matrix. The particles of 5 μm in size have shown fractures and debonding interface. Large particles of above 20 μm in size have revealed severe fractures and particles pulled out. Behavior of the MMC was explained by relating the microstructures and displacement directions of the undeformed and deformed samples. Some understandings on the behaviour of the MMCs with different vol.% of Al₂O₃ due to biaxial stresses have been established. Keywords: Metal matrix composites, biaxial stresses, microstructures, displacement, fracture, debonding AJSTD Vol. 23 Issue 4 pp. 307-321 (2006)

Mapping QTLs Associated with Root Traits Related to Drought Resistance in Vietnamese Upland Rice

Tue, 29 Apr 2008 08:16:26 +0700

Upland rice grows on 19 million ha, about 15% of the world's rice plantation [2]. The production of upland rice is crucial to agricultural economy of many countries [15]. The yield of upland rice is very low with an average of about 1 t/ha. Drought is a major constraint to the productivity of upland rice. In this paper, we present the results on mapping QTLs for root traits related to drought resistance (maximum root length, root thickness, root weight to shoot and deep root weight to shoot ratios) in upland rice using a recombinant inbreed (RI) population derived from a cross between Vietnamese upland rice accessions. The first molecular linked of Vietnamese upland rice were constructed. The map consists of 239 markers (36 SSR and 203 AFLP markers) mapped to all 12 rice chromosomes. This map covered 3973.1 cM of rice genome with an average distance of 16.62 cM between the markers. Twenty three putative QTLs were detected. Among them, four QTLs for MRL, four QTLs for R/SR, four QTLs for DR/SR, two QTL for RN, two QTLs for RT, two for PH, and five QTLs for TN were recorded. There are several SSR markers such as RM250, RM270, RM263, RM242, RM221 linked to QTL regions. They could be very useful for drought resistant selection in rice. Some common QTLs for maximum root length and deep root weight to shoot ratio were observed in different genetic background (RDB09 × R2021 and IR64 × Azorean populations) and ecological locations (IRRI and Vietnam). These QTLs could be very useful for precise locating drought resistant gene(s) and marker-assisted selection. AJSTD Vol. 23 Issue 4 pp. 323-332 (2006)

Compact 3U as a Novel Artificial Lighting Source for Gloxinia (Sinningia spp.) and Potato (Solanum tuberosum) Micropropagation

Duong Tan Nhut, Mai Thi Ngoc Huong — Tue, 29 Apr 2008 08:25:12 +0700

An efficient lighting system (Compact 3U) was successfully applied to the micropropagation of gloxinia and potato plants. To compare the in vitro growth of plantlets under Neon and Compact 3U lighting systems, gloxinia and potato shoots were cultured on suitable media at different light intensities: (1) 45 μmol m^-2s^-1 (under Neon lighting system as a control); (2) 45 μmol m^-2s^-1, (3) 60 μmol m^-2s^-1, and (4) 75 μmol m^-2s^-1 (under Compact 3U lighting systems). The results obtained after 3 weeks of in vitro culture and 6 weeks of acclimatization in a greenhouse showed that the growth of plantlets cultured under the Compact 3U system was better than that under Neon lighting system. The Compact 3U lighting source had a highly significant effect on the growth and development of gloxinia and potato plantlets. Besides, the data in our study also indicated that gloxinia and potato plantlets adapted differently to different lighting sources and light intensities. Keywords: Compact 3U, gloxinia, Neon, potato AJSTD Vol. 23 Issue 4 pp. 333-341 (2006)