Shear strength and aging characteristics of 63Sn−37Pb solder bumps with various solder ball and pad sizes

The shear strength and aging characteristics of 63Sn–37Pb solder bumps were characterized with variation in solder ball and UBM pad sizes. The shear strength increased with shorter effective crack size,a _effs which was determined with the solder ball and pad sizes. The shear strength of the solder bumps on Au/Ni/Cu and Ni/Cu did not change significantly with reflow time. Substantial decrease in the shear strength occurred for the solder bumps formed on Au/Ni/Cu with aging treatment, and the shear strength after aging was also related to the bump shape which was determined with the solder ball and pad sizes.     

Economic comparison between coal-fired and liquefied natural gas combined cycle power plants considering carbon tax: Korean case

Economic growth is main cause of environmental pollution and has been identified as a big threat to sustainable development. Considering the enormous role of electricity in the national economy, it is essential to study the effect of environmental regulations on the electricity sector. This paper aims at making an economic analysis of Korea's power plant utilities by comparing electricity generation costs from coal-fired power plants and liquefied natural gas (LNG) combined cycle power plants with environmental consideration. In this study, the levelized generation cost method (LGCM) is used for comparing economic analysis of power plant utilities. Among the many pollutants discharged during electricity generation, this study principally deals with control costs related only to CO₂ and NO₂, since the control costs of SO₂ and total suspended particulates (TSP) are already included in the construction cost of utilities. The cost of generating electricity in a coal-fired power plant is compared with such cost in a LNG combined cycle power plant. Moreover, a sensitivity analysis with computer simulation is performed according to fuel price, interest rates and carbon tax. In each case, these results can help in deciding which utility is economically justified in the circumstances of environmental regulations.     

Studies on the surface chemistry based on competive adsorption of NOx-SO2 onto a KOH impregnated activated carbon in excess O2

This study identifies surface chemistry characteristics based on competitive behavior in the simultaneous adsorption behavior of NOx (NO rich) and SO2 using KOH impregnated activated carbon (K-IAC) in excess O2. The NOx and SO2 adsorption on K-IAC occurred mainly through the acid-base reaction. The high surface area with many pores of activated carbon acted as storage places of oxide crystal produced from NOx and SO2 adsorption. KOH, an impregnant, provided the selective adsorption sites to NOx and SO2, enabling simultaneous adsorption. However, larger amounts of SO2, with higher adsorption affinity to K-IAC compared to NOx, were adsorbed in a NOx/SO2 coexistent atmosphere. Oxygen was chemisorbed to K-IAC, which enhanced the selective adsorptivity for NO. In binary-component adsorption of NOx and SO2 on K-IAC, oxide crystals such as KNO, (x = 2,3) and K2SOx (x = 3,4) were dominantly formed through two different adsorption mechanisms by chemical reacton. Depending on the extent that oxide crystals blocked pores, compositions of oxide crystals were distributed differently according to depth.     

Adsorption characteristics of SO2 on activated carbon prepared from coconut shell with potassium hydroxide activation

The adsorption characteristics of SO2 were studied with KOH-impregnated granular activated carbon (K-IAC). To confirm selective SO2 adsorptivity of K-IAC using a fixed bed adsorption column, experiments were conducted on the effects of KOH and of linear velocity, temperature, and concentration. In addition, changes in features before and after adsorption were observed by utilizing FTIR, XRD, ToF-SIMS, and AES/SAM, examining the surface chemistry. K-IAC adsorbed 13.2 times more SO2 than did general activated carbon (GAC). The amount of SO2 adsorbed increased as linear velocity and concentration increased and as temperature decreased. At lower temperature, the dominant reaction between KOH and SO2 produces K2-SO3 and H2O. Any H2O remaining on the surface is converted into H2SO4 as SO2 and O2 are introduced. Then, the KOH and SO2 reaction produces K2SO4 and H2O. The surface characterization results proved that adsorption occurred through chemical reaction between KOH and SO2. The SO2 adsorbed K-IAC exists in the form of stable oxide crystal, K2SO3 and K2SO4, due to potassium. The basic feature given to the surface of activated carbon by KOH impregnation was confirmed to be acting as the main factor in enhancing SO2 adsorptivity.     

Effect of additional carbon source on naphthalene biodegradation by Pseudomonas putida G7

Addition of a carbon source as a nutrient into soil is believed to enhance in situ bioremediation by stimulating the growth of microorganisms that are indigenous to the subsurface and are capable of degrading contaminants. However, it may inhibit the biodegradation of organic contaminants and result in diauxic growth. The objective of this work is to study the effect of pyruvate as another carbon source on the biodegradation of polynuclear aromatic hydrocarbons (PAHs). In this study, naphthalene was used as a model PAH, ammonium sulfate as a nitrogen source, and oxygen as an electron acceptor. Pseudomonas putida G7 was used as a model naphthalene-degrading microorganism. From a chemostat culture, the growth kinetics of P. putida G7 on pyruvate was determined. At concentrations of naphthalene and pyruvate giving similar growth rates of P. putida G7, diauxic growth of P. putida G7 was not observed. It is suggested that pyruvate does not inhibit naphthalene biodegradation and can be used as an additional carbon source to stimulate the growth of P. putida G7 that can degrade polynuclear aromatic hydrocarbons.     

Effect of cysteamine layer on the interaction between gold and ZrO 2 surfaces

The formation of cysteamine layer on gold surfaces may have an effect on the distribution of either gold particle adsorbed to the ZrO₂ surface or vice versa with the adjustment of the electrostatic interactions. The atomic force microscope (AFM) was used to measure the surface forces between the zirconia surface and the cysteamine surface s as a function of the salt concentration and pH value. With the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the forces were quantitatively analyzed to acquire the surface potential and charge density of the surfaces for each salt concentration and each pH value. The surface potential and charge density dependence on the salt concentration was described with the law of mass action, and the pH dependence was explained with the ionizable groups on the surface.     

Characterization of metal corrosion by aqueous amino acid salts for the capture of CO<Subscript>2</Subscript>

We investigated the absorption ability of potassium salts of amino acid solutions for carbon dioxide and compared the results with MEA. The corrosion and degradation behavior were investigated in a CO₂ absorption process using aqueous potassium salts of glycine and taurine. The experimental parameters varied were the concentration, amino acid type, temperature, CO₂ loading, piperazine, and the presence of corrosion inhibitors. The corrosion characteristics of carbon steel were measured with potassium glycinate and potassium taurate solutions over a wide range of concentrations (1.5 to 5.0 M) and temperatures (313.15 to 353.15 K). The corrosion rate was calculated using a weight loss method averaging the results of four specimens. The experimental results indicate that increases in the concentration of the aqueous amino acid salts, solution temperature, CO₂ loading, and piperazine concentration accelerate the corrosion rate. In addition, corrosion inhibitors were proven to be effective in controlling corrosion.     

Molecular-dynamics simulations of thermal accommodation of helium gas on a nanoparticle

Thermal accommodation of inert He gas atoms colliding on a nanometer-sized Ar or N₂ particle was analyzed using molecular dynamics simulations. The instantaneous values of apparent thermal accommodation coefficient (α_th) showed a distribution close to the normal distribution but with a longer tail toward lower values. The mean and standard deviation of α_th for Ar particle were about 0.39 and 0.54, respectively, and 0.44 and 0.56 for a N₂ particle. Those values were almost independent of gas temperature or pressure, with less than 10% variation over a three- or four-fold variation of the gas conditions. The thermal accommodation coefficient per collision (α₀), which was calculated from the apparent α_th and the average number of collisions on the particle surface, was about 0.18 on the Ar particle and 0.20 on the N₂ particle, both of which are in good agreement with theoretical predictions based on single interactions between free molecules.     

Melting treatment of waste asbestos using mixture of hydrogen and oxygen produced from water electrolysis

In this study, we melted four types of waste asbestos containing material such as spread asbestos, plasterboard asbestos, slate asbestos and asbestos 99 wt%, in a melting furnace at 1,450–1,550 that uses a mixture of hydrogen and oxygen (Brown’s gas) as a fuel. More volatile components (CaO, K₂O) are enriched in spread asbestos, plasterboard asbestos, and slate asbestos, while less volatile compounds (SiO₂, Fe₂O₃, MgO) remain in asbestos 99%. Through basicity of raw materials, spread asbestos, plasterboard asbestos, and slate asbestos were found to have more alkalinity, and asbestos 99% was found more acidic. SEM and EDX results revealed that all raw materials had various kinds of asbestos fiber. Spread asbestos, plasterboard asbestos, and slate asbestos were considered as tremolite asbestos, whereas asbestos 99% was considered as chrysotile asbestos. It was further confirmed by SEM and XRD studies that all waste materials contained some crystalline structures which transformed into amorphous glassy structure on melting. Also, in case of added glass cullet during the melting of spread asbestos, it transformed the raw material into a perfect vitrified product having more glassy surface and amorphous in nature     

Characterization and air pressure sensing of doubly clamped multi-walled carbon nanotubes

We report the fabrication and characterization of doubly clamped multi-walled carbon nanotubes (MWNTs). The devices were assembled by applying an electric field while the MWNTs were firmly clamped and suspended at both ends of a thick metal trench electrode in solution. The contacts were further processed using a focused ion beam. Final dimensions ranged from 100 to 150?nm in diameter and 1.5-4?μm in length. The fabricated devices were characterized by I-V curves, impedance measurements, and their mechanical deformation under a high pressure airflow. In the latter case, the resistance of a MWNT device varied linearly with the magnitude of the air pressure. These characteristics strongly suggest potential applications in fields such as nanoelectronics and sensors.