Myung-Chan Jo

INVESTIGATION OF THE EFFECT OF AGGREGATE PRETREATMENT WITH ANTISTRIPPING AGENTS ON THE ASPHALT-AGGREGATE BOND

ABSTRACT Addition of Chemical antistripping agents (ASA)to asphalt has inherent disadvantages such as reduction of the effectiveness of ASA in hot asphalt and formation of relatively weak bond with the aggregate surface. To circumvent such problems, a novel approach of aggregate pretreatment with ASA was investigated in this study. The aggregate was pretreated with aqueous emulsions/solutions of different organic surface modifiers. The effectiveness of this aggregate pretreatment procedure was evaluated to ascertain the asphalt-aggregate bond strength using the boiling water test. Boiling water test was selected for its rapidity and simplicity. The

A study on resistance of PECVD silicon nitride thin film to thermal stress-induced cracking

Abstract A potentiostatic method was used to investigate the ability of Plasma-Enhanced Chemical Vapor Deposited (PECVD) silicon nitride thin films to protect aluminum bonding areas of integrated circuit chips. Four different films in thicknesses of about 5 kA were deposited on 0.9-mm-thick stainless steel substrate and CERDIP test chips by varying deposition variables. Ultimate strain of the films was measured by controlled strain apparatus and was constant at about 0.2%. Thermal shock and cycling test was conducted to investigate the resistance of the films to thermal stress-induced cracking.. After the test, the number of cracked bondpads on the CERDIP test chips was counted and corrosion current through cracks of the films on the stainless steel substrate was measured. The results showed that more tensile films were more susceptible to crack-induced failure.

Adsorption and Thermal Desorption Behaviour of Asphalt-like Functionalities on Silica

The adsorption and thermal desorption behaviours of seven model compounds containing asphalt-like functionalities were studied on silica. Adsorption isotherms of the model compounds were examined at 25°C and analyzed via the Langmuir isotherm. A series of temperature-programmed desorption (TPD) experiments was also conducted on the silica samples, the activation energy for desorption (Ed) being determined by conventional TPD analysis. The adsorption and thermal desorption behaviours were correlated in terms of the activation energy (Ed tot) for complete desorption. Dimethyl sulphoxide showed the strongest adsorption and the largest value for Ed tot, implying that the high energy consumption necessary to desorb such functionalities plays a key role in the durability of asphalt–aggregate bonding.

A Study on the Increase in the Durability of Asphalt Paving Mixtures

Abstract A novel approach of increasing the durability of the asphalt-paving mixtures was attempted in this study by pretreatment of the aggregate surface with styrene butadiene rubber (SBR) latex as an antistripping additive (ASA). The boiling water test showed that the pretreatment method could increase the asphalt–aggregate bond strength effectively. This result was confirmed by the indirect tensile test and the stiffness index measurement of the asphalt-paving mixtures. Even though the conventional method of direct addition of ASA to the asphalt could also improve the asphalt–aggregate bond strength compared to the asphalt paving mixtures without ASA, the performance was poorer than the pretreatment method because of its inherent disadvantages of losing the effectiveness of ASA in hot asphalt. Increase of pretreatment drying time, drying temperature, and ASA concentrations could improve the asphalt–aggregate bond strength confirmed by the boiling water test. Increase in pH of the contacting water showed a detrimental effect on the asphalt paving mixtures by dissociation of the acidic functionalities of the asphalt to disrupt the asphalt–aggregate bond.

Investigation of feedpipe backmixing in an agitated vessel

Feedpipe backmixing in an agitated vessel was investigated using a newly developed conductivity technique. By this technique, the onset of feedpipe backmixing could be detected and the penetration depth of the vessel fluid into a feedpipe was determined. For a given feedpipe flowrate. critical agitator speeds to eliminate feedpipe backmixing were determined using Rushton six-bladcd disk turbine impeller (6BD) and high efficiency, axial-flow type 3-bladed impeller (HE-3) of 8.89 and 12.70 cm diameters in 11.2 liter reactor. The ratio of the feedpipe velocity to the critical agitator speed (vf/vi) was determined as a function of feedpipe Reynolds number (NR,T). The conductivity technique was successful either in the laminar regime, the transitional regime, or in the turbulent regime in the feedpipe.

Development of Water Reusing System by Using Net3FM (Net Fit Fiber Filter Module)

This study was carried out to develop pilot plant Net3FM(Net Fit Fiber Filter Module) system and to suggest optimum operating condition for municipal wastewater reuse. SS concentration of biologically treated sewage effluent was reduced from 1.5~5.4mg/L to 0.4~1.0mg/L without coagulant injection in Net3FM system, and the SS removal efficiency was average 84.7%. And also, the removal efficiencies of COD and T-P were decreased slightly due to the SS removal by filtration. Coagulation-Filtration test was conducted to enhance the removal efficiencies of SS and T-P. The optimum dosage of coagulant was injected automatically by auto-controlling system, which is controlled by detecting value of turbidity of secondary sewage effluent. SS, COD and T-P concentrations in filtrated effluent were 0.21~0.57, 1.6~6.2 and 0.137~0.392mg/L with coagulant injection by in-line mixer in Net3FM system, respectively. The removal efficiencies of SS and T-P were highly increased to 92.8% and 89.8%, respectively. It was due to the combined the processes of coagulation and filtration. Net3FM system was evaluated that the removal efficiency of pollutants in secondary sewage effluent and the utilization potential as reclaimed water technology were very high.

Journal of the Environmental Sciences A Study on the Operating Conditions to Eliminate Feedpipe Backmixing for Fast Competitive Reactions

A novel conductivity technique was developed to detect penetration depth of the vessel fluid into the feedpipe. For a given reactor geometry, critical agitator speeds were experimentally determined at the onset of feedpipe backmixing using Rushton 6 bladed disk turbine (6BD) and high efficiency axial flow type 3 bladed (HE-3) impellers. The ratio of the feedpipe velocity to the critical agitator speed () was constant for either laminar or turbulent feedpipe flow regimes. Compared to the results of fast competitive reaction, feedpipe backmixing had to penetrate at least one feedpipe diameter into the feedpipe to significantly influence the yield of the side product. However, higher than that for L/d = 0 (position at the feedpipe end) of the conductivity technique is recommended to completely eliminate feedpipe backmixing in conservative design criteria. The conductivity technique was successful in all feedpipe flow conditions of laminar, transitional and turbulent flow regimes.

Characterization of Enhanced CO Oxidation Activity by Alumina Supported Platinum Catalyst

A novel pretreatment technique was applied to the conventional Pt/alumina catalyst to prepare for the highly efficient catalyst for the preferential oxidation of carbon monoxide in hydrogen-rich condition. Their performance was investigated by selective CO oxidation reaction. CO conversion with the oxygen-treated Pt/Alumina catalyst increased remarkably especially at the low temperature below . This result is promising for the normal operation of the proton exchange membrane fuel cell (PEMFC) without CO poisoning of the anode catalyst. XRD analysis results showed that metallic Pt peaks were not observed for the oxygen-treated catalyst. This implies that well dispersed small Pt particles exist on the catalyst. This result was continued by high resolution transmission electron microscopy (HRTEM) analysis. Consequently, it can be concluded that highly dispersed Pt nanoparticles could be prepared by the novel pretreatment technique and thus, CO conversion could be increased considerably especially at the low temperatures below .

Enhancement of Catalytic Activity of Pt/Alumina by a Novel Pretreatment Method for the CO Oxidation for Fuel Cell Applications

Hydrogen gas is used as a fuel for the proton exchange membrane fuel cell (PEMFC). Trace amount of carbon monoxide present in the reformate gas can poison the anode of the PEMFC. Therefore, preferential oxidation (PROX) of CO is essential for reducing the concentration of CO from a hydrogen-rich reformate gas. In this study, conventional Pt/ catalyst was prepared for the preferential oxidation of CO. The effects of catalyst preparation method, additive, and hydrogen on the performances of PROX reaction of CO were investigated. Water treatment and addition of Ce enhanced catalytic activity of the Pt/ catalyst at low temperature below .

A Study on the Effect of Polyamine on the Adsorption of Asphalt-Like Functionalities onto Silica Surface

The effect of precoating of silica with polyamine surfactants on the adsorption of five model compounds containing asphalt-like functionalities was studied. Hexadecyltrimethylammonium chloride (HDTMA) and 1-hexadecylamine were used for silica precoating. The model compounds representing five asphalt functionalities were benzoic acid, phenol, benzylbenzoate, benzophenone, and quinoline. All the adsorption isotherms conformed well to the Langmuir adsorption model. All the model compounds showed decreased adsorption with the HDTMA precoating. However, two acidic compounds, benzoic acid and phenol, showed enhanced adsorption on the silica precoated with 1-hexadecylamine. In aqueous solutions, the adsorption of the acidic compounds were in the following order: silica precoated with 1-hexadecylamine > silica precoated with HDTMA > uncoated silica.