An Introduction on the Laser Cladding Coatings on Magnesium Alloys

Magnesium alloys are a promising structural material to be used as a substitute for metals traditionally used in the automotive and aircraft sector. However, magnesium alloys have poor mechanical properties and corrosion resistance. These handicaps can be overcome through the application of coatings with improved properties. Laser cladding is a potential coating fabrication process. Furthermore, the low vaporization temperature of magnesium and the coating-substrate dilution problems increase the difficulty to coat magnesium substrates. The aim of this research is to analyze the state of art in magnesium laser cladding and investigate the effect of the most important fabrication parameters on the interaction of the different coating-substrate systems used on the mechanical properties and corrosion resistance. In addition, this work provides a guidance on laser cladding best practices for these alloys. Knowledge of how the different coating manufacturing parameters affect the final surface properties of magnesium alloys is essential for the implantation of these materials in applications for which they are currently limited.

PROSES PEMURNIAN FRAKSI KAYA RHODINOL MINYAK SEREH WANGI MENGGUNAKAN SPINNING BAND DISTILLATION

Indonesia, as one of the biggest countries which supplies citronella oil, has a high potential to produce natural rhodinol. Recent studies on rhodinol purification using fractional and mollecular distillation showed the difficulty of obtaining high purity and yield. The objective of this study was to determine the method of spinning band distillation to purify rhodinol regarding reflux ratio and vaporization temperature. Citronella oil was divided into three fractions according to its boiling points. The volume of each fraction was estimated by its ratio (according to GC analysis) to the feed volume: F1 (components before rhodinol) 21.73%, F2 (rhodinol) 61.7%, and residue 15.82%. Initial research established the best conditioning before the purification process was 3 mmHg of pressure, equilibration started at 160oC in 30 minutes, and 18–17% of heat rate, as these created the stability of the vapor temperature. The levels of reflux ratio were 3:1 and 5:1, while the evaporation temperatures of rhodinol were 230oC and 235 oC. Reflux ratio of 5:1 at 230oC obtained the highest purity (81.30%) and the highest yield (72.94%). Equilibration and reflux ratio allowed rectification inside the column because the spinning band homogenized the vapour molecules by its downwards flow and wiped the reflux on the inner surface, which in turn caused the molecules with a lower boiling point to evaporate gradually. Meanwhile the other yields were 79.81% (3:1 at 230 oC), 80.53% (3:1 at 235 oC), and 80.21% (5:1 at 23oC) with yields of 71.82%, 70.31%, and 68.23%. Keywords: citronella oil, purification, rhodinol, spinning band distillation

Rapid Electrical Heating of Aluminum-Boron Nano-Laminates

ABSTRACTRapid or explosive heating of electrically conductive films has several applications, and the use of reactive laminates to increase output energy is an intriguing concept. Past studies have shown electrically heated aluminum/nickel (Al/Ni) nano-laminate films to augment this energy by an amount approximately equivalent to the expected heat of mixing between the two elements, which for most intermetallics is a significant fraction of the total heat of reaction (86% for Al/Ni). In this study, we investigate the use of sputtered aluminum/boron (Al/B) laminates to determine whether a similar increase, as measured by the velocity of an ejected flyer layer, occurs. However, observed velocities in any samples containing boron were 38% to 45% lower than samples without boron, despite much higher heats of reaction reported in the literature for Al/B. We attributed this reduction to the vaporization temperature of boron being much higher than that of Al, and because Al electrical resistivity at elevated temperatures was still much lower than boron, boron heating was less efficient as vaporized Al expanded and drove the ejected flyer. These results and analysis give insight into other reactive material combinations in which one of the constituents is an electrical insulator.

Direct determination of trace mercury and cadmium in food by sequential electrothermal vaporization atomic fluorescence spectrometry using tungsten and gold coil traps

On the basis of vaporization temperature difference, a novel solid sampling AFS was developed for the sequential determination of trace Hg and Cd in food samples.

Numerical Simulation of Magnetic Field-Assisted Material Removal in Micro-EDM

In the present paper, a two dimensional numerical model has been developed using the finite element method (FEM) for predicting the material removal mechanism in micro EDM process in single spark with the assistance of magnetic field. The work piece material selected for the present study is grade 5 titanium material. The model developed by not considering magnetic field, first calculates the temperature distribution in the work piece material using the commercial software ANSYS. The crater shape is developed using the simulated temperature profiles to estimate the volume of material removed in a single spark, by considering the melting point and vaporization temperature. The model has been validated by comparing the theoretical MRR with the experimental results which is already established. The use of magnetic field which can provide an additional Lorentz force in the melt pool could aid in ejection of material from the discharge crater, thereby improving MRR. This concept is established through the coupling of magnetic and structural fields.

Synthesis of Cu2ZnSnSe4 Compounds Using Solvo-Thermal Method

We reported a fabrication of Cu2ZnSnSe4 (CZTSe) via an elemental solvo-thermal method. To suppress the sublimation of Se, we made use of binary compounds of high vaporization temperature by first converting solid Se into a liquid-like alloy. Single-phase CZTSe compounds with the band gap of 1.32 eV were successfully synthesized and characterized. The effect of synthesizing temperature on the formation of CZTSe was also investigated.

Surface Modification of Silicon Carbide Powder with Silica Coating by Rotary Chemical Vapor Deposition

The surface of silicon carbide (SiC) powder was modified by coating with amorphous silica (SiO2) using (C2H5O4)Si (tetraethyl orthosilicate: TEOS) as a precursor by rotary chemical vapor deposition (RCVD). With increasing deposition time from 0.9 to 14.4 ks, the mass content of SiO2 coating increased from 1 to 35 mass%. The SiO2 mass content had a linear relationship with deposition time from 2.7 to 7.2 ks. The effects of O2 gas flow, deposition temperature (Tdep), total pressure (Ptot) and precursor vaporization temperature (Tvap) on the SiO2 yield by RCVD were investigated. At O2 gas flow of 4.2 × 10-7 m3 s-1, Tdep of 948 K, Ptot of 400 Pa and deposition time of 7.2 ks, the maximum SiO2 yield of 1.82 × 10-7 kg/s with SiC powder of 4.5 × 10-3 kg by RCVD was obtained.