Ratchatee Techapiesancharoenkij

Development of a Kraft Paper Box Lined with Thermal-Insulating Materials by Utilizing Natural Wastes

This research studied the feasibility of using natural fibers extracted from natural wastes as a thermal-insulating material lined in a Kraft paper box packaging. The natural fibers were extracted from natural waste of rice straws using NaOH solutions. The extracted fibers were then formed as a porous thermal-insulating pad by a spray lay-up method using natural rubbers as binders. The thermal conductivities, specific heat capacities and temperature-rise time of the natural fiber insulation and other thermal-insulating materials including polystyrene foam, a polyethylene foam, and a glass fiber insulation were studied and compared. The glass fiber insulation showed the highest thermal conductivity, while the thermal conductivities of the other studied insulating materials were found to be similar. Moreover, the polymeric and natural-fiber insulations show better temperature-rise resistance than the glass fiber insulation. The temperature rises for different insulating materials were estimated using the analytical analysis of heat transfer. The calculated temperature-rise times were compared with the empirical results; both results are in the same order of magnitude. Consequently, a Kraft paper box lined with natural-fiber pads was constructed and compared with a Kraft paper box (without insulation lining) and a polystyrene box of equal sizes. The boxes were packed with an equal amount of ice and left under room temperature for 24 hours. The results show that, after 24 hours, the temperatures inside the natural-fiber lined box and the polystyrene box were contained below 15 °C, while the temperature inside the Kraft paper box increase to room temperature only after 16 hours. The observation shows that a natural fiber pad can potentially be used as an alternative insulating material in packaging industries, which can enhance environmental-friendly packaging products.

The Thermal-Aging Effect on the Microstructure Evolution and Shear Strength of the Sn-Rich Au-Sn Soldering between Altic and Si Substrate in Microelectronics

The Au-Sn soldering alloys are commonly used in microsoldering process for microelectronic industry due to fluxless process and relatively low melting temperature with good eutectic microstructures. This study investigated the microstructures of Au-Sn soldering between AlTiC and Si substrates with Ti/Pt/Au under bump metallization (UBM). The microstructures of the solder samples under three conditions: before bonding, after bonding and after thermal-cycle aging, were investigated. The shear strength values of pre-aging and post-aging soldering were compared. The thermal-cycling temperatures were ranged from -40 to 125 °C for 300 cycles. The intermetallic compounds (IMCs) of the AuSn solders consist of AuSn, AuSn2, and AuSn4. After thermal-cycle aging, the bonding strength was increased due to the improved IMC bonding between solders and UBM; the shear surfaces were rougher due to the growth of AuSn and AuSn2.

Effects of Sn Concentration on Chemical Composition, Microstructure and Photocatalytic Activity of Nanoparticulate Sn-Doped TiO2 Powders Synthesized by Solution Combustion Technique

Utilization of photocatalytic properties of materials can be perceived through a wide range of applications, such as anti-bacterial, water treatment, and self-cleaning materials. It has been established that doping can result in alteration of photocatalytic activities. This study aimed at studying effects of tin concentration on chemical composition, microstructure, band gap energy, and photocatalytic activities of tin-doped titanium dioxide powder synthesized by solution combustion technique. Experimental results revealed that concentration of tin significantly influenced chemical composition of the powders. A semi-quantitative analysis indicated that tin oxide secondary phase increased from 11 to 23 wt%, as the Sn increased from 2.5 to 10 mol%, respectively. Tin concentration, nevertheless, did not significantly influence microstructure of the powders. All powders had average particle size ranging from 13.1 to 13.4 nm, which agglomerated into clusters with average sizes ranging from 103 to 140 nm. A slight increase of band gap energy was observed at higher tin concentration. The most prominent photocatalytic activities, determined from decomposition of methylene blue, was found in the titanium dioxide powder with 2.5 mol% Sn.

The Alloying and Aging Effects on the Wettability and Intermetallic Bonding of the Sn-Zn-Cu-Bi Soldering Alloy on a Cu Substrate

The soldered bonding between the Sn-Zn-Cu-Bi system and a Cu substrate was studied and reported herein. The alloying compositions were varied to investigate the effects of Zn, Cu, Bi contents on the solders’ melting temperature (Tm), microstructures, wettability and the intermetallic-compound (IMC) bonding with a Cu substrate. The Sn-7Zn and Sn-9Zn exhibited low Tm (198 °C), but poor wettability on the Cu substrates. Both Cu and Bi additions significantly improved the solder wettability. However, the Tm of the Sn-Zn-Cu series increased sharply to about 225 °C by the addition of 4-wt% Cu. The addition of 3-wt% Bi lowered Tm of the Sn-Zn-Cu alloys by 5 °C. The thickness of the IMC layers between solder and substrate was maximum for Sn-9Zn and significantly decreased with the Cu addition. With the addition of Bi to Sn-Zn-Cu, the IMC thickness increased. The aging of 150 °C for 150 hours minimally affected the IMC-bonding thicknesses of most samples; however, micro crack could be observed along the aged IMC layers.

Effect of Copper and Zinc on Microstructures, Melting Points and Corrosion Resistance of Sn-Zn-Cu-Bi Soldering Alloys

Sn-Zn alloy is one of the Pb-free systems that are promising because of its relatively low melting temperature and low cost. However, Zn exhibits poor corrosion and oxidation resistance that hinders its soldering applications. The objective of this research is to study the effect of Zn and Cu alloying contents on the Sn-Zn performance. Four compositions of Sn-Zn alloys were studied in this research including: Sn-7Zn, Sn-9Zn, Sn-9Zn-2Cu-Bi, and Sn-9Zn-4Cu-Bi. The microstructures were studied using Optical Microscope (OM) and Scanning Electron Microscope (SEM). The melting temperatures and corrosion resistance of the alloys were evaluated by Differential Scanning Calorimeter (DSC) and Potentiodynamic Polarization technique, respectively. The results showed that an increase in the Cu-to-Zn ratio led to better corrosion resistance. The selective corrosion of the Zn-rich phase could be visibly observed, with OM, on the post-corrosion samples. With the Cu alloying, the Cu and Zn formed an intermetallic compound resulting in a higher value of Ecorr. However, the higher Cu content caused a significant increase in the liquidus temperature due to the Cu-Zn intermetallic compound, of which the melting temperature is higher than 400 °C, resulting in an incomplete melting at low temperature.

Material Safety and Integrity of Water-Filled Low-Density Polyethylene Bags in an Accelerated Weathering Investigation for Applications in Solar Water Disinfection (SODIS)

In this work, the potential use of LDPE bags as containers in the SODIS application by simulated in an accelerated weathering tester (QUV), with respect to material safety and durability, was investigated. For the material integrity, a decrease in the elongation at break from 818% (at the beginning) to 21% (after 6 weeks of UV exposure) corresponded to the long UV exposure. A significant degree of mechanical degradation was evident during 2 to 4 weeks of UV exposure. The UV-Vis results showed that the UV transmittance of the bags, mostly in the UV-B region, decreased with longer duration of UV exposure. The FT-IR results showed a slight increase in carbonyl group, particularly observable in the bags exposed under UV for 3 weeks or longer. For the material safety, the amount of plastic additives that were leached into water was negligibily small and much lower than the limit of the safety standard. The results and analyses from this work provide insights into the feasibility of LDPE as an alternative material for SODIS containers and potentially be useful for future designs of SODIS containers to improve the disinfection and durability performances.

Electrochemical Codeposition of Ti-dispersed Ni-matrix Layers by Pulse-Form Current

The electrochemical codeposition is a process by which particle-dispersed metal-matrix coating is electroplated from a plating bath suspended with particles. The codeposition can be applied to produce an intermetallic-contained layer requiring subsequent heat treatment for intermetallic formation. In this research, the codeposition of a Ti-dispersed Ni-matrix layer is of interest; dispersed-Ti particles can potentially enhance the mechanical and chemical properties of the Ni-matrix coating. Moreover, with a proper composition control and heat treatment, the Ni-Ti layer can potentially transform into NiTi alloy. To enhance the coating uniformity and Ti composition, the pulsed current is applied to codeposit Ni-Ti layers. The studied parameters include the duty cycle and frequency of the pulsed current. The Ni-Ti layers are analyzed by X-Ray fluorescent and scanning electron microscope. The results show that the pulse form improves the coatings’ uniformity. The duty cycle significantly affects the coatings’ Ti contents, while the frequency exhibits minimal effect.

Microstructural and Corrosion Characterizations of Nickel‐Titanium Coatings Produced by Electrochemical Codeposition and Heat Treatment

The Ti-dispersed Ni-matrix composite coating on a copper substrate is prepared by the electrochemical codeposition process by which the coating is electroplated from a Ni-ion electrolytic solution suspended with Ti particles. The Ni-Ti coatings are subsequently heat-treated under Argon atmosphere to form intermetallic Ni-Ti phases. The polarization curves of pure Ni coating and as-codeposited Ni-Ti coatings are characterized by potentiostatic polarization measurement to investigate their corrosion-resistant behaviors. The phase composition and microstructures of the coatings are characterized by X-Ray diffractometer and scanning electron microscope. The as-codeposited Ni-Ti coatings show no sign of oxide impurities. The heat-treated coatings exhibit mixture of Ni-Ti intermetallic phases, oxide and nitride compounds. The equilibrium corrosion behavior of the Ni-Ti composite coatings is negatively affected by their rough surfaces and porosity. Both nickel coating and Ni-Ti composite coatings exhibit passivity and remain intact even after the corrosion test.