Adsorption of CO2+ by stylene‐g‐polyethylene membrane bearing sulfonic acid groups modified by radiation‐induced graft copolymerization

Cation‐exchange hollow fiber membrane was prepared by radiation‐induced grafting polymerization of styrene onto polyethylene hollow fiber membrane and its sulfonation. Adsorption characteristics for the cation‐exchange membranes are examined when the solution of Co²⁺ permeates across the cation‐exchange fiber membrane. The maximum grafting peak was obtained from 70% styrene concentration at 50°C. The degree of grafting (%) was enhanced with additives such as H₂SO₄ and divinylbenzene. The content of  SO₃H groups ranged from 2 to 5 mmol g⁻¹ with chlorosulfonic acid (ClSO₃H) in dichloroethane, from 0.5 to 6 mmol g⁻¹ with ClSO₃H in H₂SO₄, respectively. The adsorption of Co²⁺ by the cation‐exchange membranes increased with increasing  SO₃H content. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 2227–2235, 1999     

Surface reaction on polyvinylidenefluoride (PVDF) irradiated by low energy ion beam in reactive gas environment

Polyvinylidenefluoride (PVDF) was irradiated by a keV Ar⁺ ion in O₂ environment for improving adhesion between PVDF and Pt, and reaction between PVDF and the ion beam has been investigated by X‐ray photoelectron spectroscopy (XPS). The adhesion test between Pt and the modified PVDF was carried out by boiling test, in which the specimens were kept in boiling water for 4 h. Two failure modes (buckling up due to weak adhesion and crack formation due to strong adhesion) of Pt films have been observed in the system. Contact angle of PVDF was reduced to 31 from 75° by the irradiation of 1 × 10¹⁵ Ar⁺ ions/cm² with oxygen flow rate of 8 sccm. The surface of the irradiated PVDF became more rough as ion dose increased. The improved adhesion mechanism and identification of newly formed chemical species have been confirmed by Carbon 1s and Fluorine 1s X‐ray photoelectron core‐level spectra. The main reaction occurred at the irradiated PVDF surface is an ion‐beam‐induced oxidation accompanied with preferential sputtering of fluorine. Newly formed chemical species at interface are regarded as ester and carboxyl groups. Adhesion of the Pt–PVDF interface was improved by ion irradiation in O₂ environment. This improvement is originated from the presence of carbon—oxygen bonds on the irradiated PVDF surface. Comparison of failure modes on the irradiated PVDF at various conditions after the boiling test shows that adhesion of Pt film is largely affected by the product of ion‐assisted reaction. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 41–47, 1999     

Graft copolymerization of mixtures of acrylic acid and acrylamide onto polypropylene film

Liquid phase ultraviolet irradiation in the presence of benzophenone as a photosensitizer and barium hydroxide as a pH controller were used to graft the mixtures of acrylic acid and acrylamide to a polypropylene surface. The surface of the grafted polypropylene samples were characterized by Fourier transform infrared spectroscopy‐attenuated total reflectance, electron spectroscopy for chemical analysis, scanning electron microscopy, and a contact angle meter. The pH value of the reaction medium that produced the graft with equal molar ratio was found to be ∼ 3.77. The optimal reaction condition was found at a monomer feed of 25%, a reaction time of 30 min, and a benzophenone concentration of 1%. Surface tension of the samples increased to a value of 40 dyn cm⁻¹ due to the graft of the hydrophilic monomers. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 251–256, 1999     

Numerical analysis for a proposed hybrid system with single HAWT,double HATCT and vertical oscillating wave energy converters on a single tower

South Korea has huge renewable energy potential that has been to some extent and can be further extracted to reduce its heavy reliance on fossil fuels. This project focuses on ocean and coastal wind resources available in the south-western regions of Korea that are currently being monitored and found to have huge potential. The project will propose a new concept of wind, tidal current and wave energy converting systems combined together that can boost output power capacity at a single location also making it easier for grid connection. Wind turbines nowadays have been quite efficiently developed and implemented throughout the world both onshore and offshore. However, tidal current and wave energy have yet more room for improvement. The current study will combine the offshore wind turbine (HAWT) system with two tidal current turbines (HATCT) both in horizontal axis classification on a single tower. It will further discuss on adding a wave energy converter in between the wind and tidal current turbines. Optimization of the tower is also a minor part of this study. The structural analysis of the main tower, which is the main focus of the study, is investigated by dynamic response analysis to check its feasibility for combining the three types of renewable energy converters on one support. Actual extreme conditions of the wind, ocean currents and waves are simulated using ANSYS CFX fluid flow analysis. The results are used for conducting a one way FSI analysis assuming a rigid structure to verify the safety of the system.

     

Morphological analysis and classification of types of surface corrosion damage by digital image processing

This paper examines a new concept of corrosion surface damage analysis by using the digital image processing. Corrosion phenomena are analyzed using a digital value for morphological surface damages instead of electrochemical methods. Initial images are characterized by three categories: color, texture and shape features. To calculate corrosion surface damages color we use the interpretation of HIS model. For the texture attributes, the method of co-occurrence matrix is used. Five types of corrosion damage are examined. Multidimensional scaling procedure is used to define the classification plane. This study suggests a probabilistic method of decision-making. This analysis develops a method for automated identification system of corrosion damages and is supposed to be more advantageous than that of electrochemical techniques.     

Characteristics of laser aided direct metal/material deposition process for tool steel

Laser aided direct metal/material deposition (DMD) process builds metallic parts layer-by-layer directly from the CAD representation. In general, the process uses powdered metal/materials fed into a melt-pool, creating fully dense parts. Success of this technology in the die and tool industry depends on the parts quality to be achieved. To obtain designed geometric dimensions and material properties, delicate control of the parameters such as laser power, spot diameter, traverse speed and powder mass flow rate is critical. In this paper, the dimensional and material characteristics of directed deposited H13 tool steel by CO₂ laser are investigated for the DMD process with a feedback height control system. The relationships between DMD process variables and the product characteristics are analyzed using statistical techniques. The performance of the DMD process is examined with the material characteristics of hardness, porosity, microstructure, and composition.     

Correlation of microstructure and high temperature oxidation resistance of plasma sprayed NiCrAl, NiCrAlY, and TiAlO composite coatings on Ti−6Al−4V

In the present study Ni−18Cr−6Al, Ni−22Cr−10Al−1Y and TiAlO composite powders were coated on Ti−6Al−4V substrates by atmospheric plasma spraying, and the coated specimens were evaluated by isothermal and cyclic oxidation resistance tests at 800°C. The oxidation kinetics of the plasma sprayed NiCrAl, NiCrAlY, and TiAlO composite coated specimens obey a parabolic rate law. The oxidation resistance of the plasma sprayed NiCrAl and NiCrAlY coatings is superior to that of plasma sprayed TiAlO composite coating. The best oxidation resistance was observed in the plasma sprayed NiCrAlY coatings. This is mainly attributed to the formation of Y−Al−O complex oxides and Ni₃Al with higher thermal stability on the coatings.     

Characterization of oxide scales formed on low carbon steel between 1100 and 1250 °C in air

A low carbon steel was oxidized isothermally at temperatures of 1100–1250 °C for up to 2 h in air, and the oxide scales were examined. Several hundred micrometer-thick scales formed owing to poor oxidation resistance at high temperatures. Scales consisting mainly of Fe₂O₃, Fe₃O₄, and FeO spalled easily, owing to the formation of voids and cracks in the scales. All the alloying elements were also oxidized and incorporated in the iron oxide scales, depending on their local concentration in the matrix.     

Corrosion performance of high pressure die-cast Al-6Si-3Ni and Al-6Si-3Ni-2Cu alloys in aqueous NaCl solution

The corrosion performance of high pressure die-cast Al-6Si-3Ni (SN63) and Al-6Si-3Ni-2Cu (SNC632) alloys in 3.5% (mass fraction) NaCl solution was investigated. X-ray diffraction (XRD) and microstructural studies revealed the presence of single phase Si and binary Al₃Ni/Al₃Ni₂ phases along the grain boundary. Besides, the single Cu phase was also identified at the grain boundaries of the SNC632 alloy. Electrochemical corrosion results revealed that, the SNC632 alloy exhibited nobler shift in corrosion potential (?_corr), lower corrosion current density (J_corr) and higher corrosion resistance compared to the SN63 alloy. Equivalent circuit curve fitting analysis of electrochemical impedance spectroscopy (EIS) results revealed the existence of two interfaces between the electrolyte and substrate. The surface layer and charge transfer resistance (R_ct) of the SNC632 alloy was higher than that of the SN63 alloy. Immersion corrosion test results also confirmed the lower corrosion rate of the SNC632 alloy and substantiated the electrochemical corrosion results. Cu addition improved the corrosion resistance, which was mainly attributed to the absence of secondary Cu containing intermetallic phases in the SNC632 alloy and Cu presented as single phase.     

Photoreaction of gold ions from potassium gold cyanide wastewater using solution-combusted ZnO nanopowders

Photoreduction of gold ions from potassium gold cyanide wastewater was tried using the ZnO nanopowder which was synthesized by a unique solution combustion method (SCM). The SCM produced instantaneous high pressure and high temperature (1500–1800 °C) conditions which are desirable to obtain high quality ZnO nanopowders, even though it was not intentionally heated at higher than 100 °C during the synthesis reaction. The high crystalline quality of the ZnO nanopowder seemed to result in high efficiency of gold recovery compared to other commercial photocatalysts such as P-25 TiO₂ nanopowder (Degussa). The wastewater contains many kinds of ions such as K, P, Au, Na, Ni, Cu and Zn ions. Only the gold ions were selectively recovered out of these ions. The gold recovery efficiency of the SCM ZnO nanopowder was about 8.6 folds higher than that of the P-25 TiO₂ nanopowder. The very high selectivity of Au³⁺ ions could be explained by the reduction potential which is placed near the edge of valence band.