• Journal of the Korean Ceramic Society
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• v.41 no.8
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• pp.610-617
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• 2004

For preparation $\alpha$-Al$_2$O$_3$ platelets having 20 $\mu$m in average diameter and 0.2∼0.3 $\mu$m in thickness, we have prepared aluminum hydroxides gel by using aluminum sulfate and sodium sulfate as starting materials. In this study, we investigated the effect of the amount of sodium phosphate on particle size, morphology and thickness of $\alpha$-Al$_2$O$_3$ platelets. When sodium phosphate was not added to aluminum hydroxides gel, most of $\alpha$-Al$_2$O$_3$ platelets had hexagonal shape but the thickness was over 1.0 $\mu$m, and this sample was not adequate for pearlescent pigment. On the other hand, introduction of sodium phosphate caused an increase of aspect ratio (particle diameter/thickness) with a decrease in $\alpha$-Al$_2$O$_3$ platelet thickness.

• Journal of Environmental Health Sciences
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• v.25 no.3
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• pp.23-28
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• 1999

Phosphate removal through adsorbent, such as activated alumina, powdered aluminum oxide, flyash, blasted furnace slag and other materials, is commonly and widely practiced. The purpose of this study was to improve the removal efficiency of phosphorus in waste sludge earned at seafood processing factories. To investigate the utility and the feasibility of this sludge disposal process, experiment was carried out with a batch process. As a result, phosphate removal appears to increase with increasing adsorbent does, but shows no changes at an adsorbent does over 5g/l. With increasing ratios of initial phosphate concentration to adsorbent does, the amount of removed phosphate is increased while phosphate removal(%) is decreased. Wasted sludge, treated with zinc chloride chemically, represented a better efficiency than the untreated activated sludge and zinc chloride itself, when they reacted with phosphate solution.

• Nuclear Engineering and Technology
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• v.54 no.11
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• pp.4062-4071
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• 2022

Long-term aluminum (Al) corrosion tests were designed to investigate the condition that would generate severe Al corrosion and precipitation. Buffer agents of sodium tetraborate (NaTB), trisodium phosphate (TSP) and sodium hydroxide (NaOH) were adopted. The insulation materials, fiberglass and calcium silicate (Ca-sil), were examined to explore their effects on Al corrosion. The results show that significant precipitates were formed in both NaTB/TSP-buffered solutions at high pH. The precipitates formed in NaTB solution raise more concerns on chemical effects in GSI-191. A passivation layer formed on the surfaces of coupon in solution with the presence of insulations could effectively mitigate Al corrosion. The Fe-enriched intermetallic particles (IPs) embedded in coupon appeared to serve as seeds to readily induce precipitation via providing extra area for heterogeneous Al hydroxide precipitation. X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analyses indicate that the precipitates are mainly boehmite (γ-AlOOH) and no direct evidence confirms the presence of sodium aluminum silicate or calcium phosphate.

• The Korean Journal of Ceramics
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• v.3 no.4
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• pp.269-273
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• 1997

Chemical composition of cement powder influences the setting time and early compressive strength development. The setting time increases as the amounts of zinc oxide and magnesium oxide are increased. For one day compressive strength development, a cement powder with a composition 90% ZnO, 8% MgO and 2% silica resulted in the highest strength (greater than 1, 090 kg/$\textrm{cm}^2$). Cement-forming liquids also need to be buffered, with both aluminum and zinc ions, for a good consistency and a higher strength of the zinc phosphate cement. These liquids control the setting reactions.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.6
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• pp.521-527
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• 2017

Phosphorus is one of the limiting nutrients for the growth of phytoplankton and algae and is therefore one of leading causes of eutrophication. Most phosphorous in water is present in the form of phosphates. Different technologies have been applied for phosphate removal from wastewater, such as physical, chemical precipitation by using ferric, calcium or aluminum salts, biological, and adsorption. Adsorption is one of efficient method to remove phosphates in wastewater. To find the optimal media for phosphate removal, physical characteristics of media was analysed, and the phosphate removal efficiency of media (silica sand, slag, zeolite, activated carbon) was also investigated in this study. Silica sand showed highest relative density and wear rate, and phosphate removal efficiency. Silica sand removed about 36% of phosphate. To improve the phosphate removal efficiency of silica sand, Fe coating was conducted. Fe coated silica sand showed 3 times higher removal efficiency than non-coated one.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.38 no.4 s.117
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• pp.61-67
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• 2006

The effect of several inorganic flame-retardants such as ammonium phosphate, ammonium sulfate, aluminum hydroxide and antimony trioxide on the flame-retardant property and tensile strength of paper has been investigated. Flame-retardants were used preferably as a dry powdered mixture and added to the furnish. Both dipping and coating treatments were employed to apply flame-retardants to paper Flame-retardant paper was manufactured by treatment of $5{\sim}30%$ flame-retardants by weight of the paper on a dry weight. Paper's flame-retardant property and tensile strength were examined by comparison of char length and tensile index. As dosages of flame-retardant chemicals increased, flame-retardant property was improved but tensile index was decreased.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.6
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• pp.663-671
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• 2016

Coagulation/precipitation process has been widely used for the removal of phosphate within domestic wastewater. Although Fe and Al are typical coagulants used for phosphate removal, these have some shortages such as color problem and low sedimentation velocity. In this study, both Fe and Al were used to overcome the shortages caused by using single one, and anionic polymer coagulant was additionally used to enhance sedimentation velocity of the precipitate formed. Batch experiments using a jar test were conducted with real wastewater, which was an effluent of the second sedimentation tank in domestic wastewater treatment plant. Response Surface Methodology was used to examine the responsibility of each parameter on phosphate removal as well as to optimize the dosage of the three coagulants. Economic analysis was also done on the basis of selling prices of the coagulants in the field. Phosphate removal efficiency of Fe(III) was 30% higher than those of Fe(II). Considering chemical price, optimum dosage for achieving residual phosphate concentration below 0.2 mg/L were determined to be 18.14 mg/L of Fe(III), 2.60 mg/L of Al, and 1.64 mg/L of polymer coagulant.

• Corrosion Science and Technology
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• v.6 no.4
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• pp.206-210
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• 2007

Aerospace aluminum alloys such as Al alloy 2024-T3 and 7075-T6 are subject to localized corrosion due the existence of intermetallics containing Cu, Mg or Zn. Chromate is currently widely used in the aerospace industry as the corrosion inhibitor for these alloys. However, chromate needs to be replaced due to its strong carcinogenicity. In this study, an extensive pigment screening has been performed to find replacements for chromates. Different categories of inhibitors were evaluated by immersion tests, DC polarization tests and other methods. Phosphates, zinc salts, cerium salts, vanadates and benzotriazole were found to be effective inhibitors for AA7075. Among those inhibitors, zinc phosphate was found to be the most effective in our novel, silane-based, one-step aqueous primer system. The performance of this primer is comparable to that of currently used chromate primers in accelerated corrosion tests, while it is completely chromate-free and its VOC is about 80% less than that of current primers. Studies by SEM/EDS showed that the unique structure of the superprimer accounts for the strong anti-corrosion performance of the zinc phosphate pigment. The self-assembled stratified double-layer structure of the superprimer is characterized by a less-penetrable hydrophobic layer at the top and a hydrophilic layer accommodating the inhibitors underneath. The top layer functions as the physical barrier against water ingress, while the lower layer functions as a reservoirfor the inhibitor, which is leached out only if the coating is damaged by a scratch or scribe. The presence of a silane in the primer further improves the adhesion and anti-corrosion performance of the primer.

• Journal of the Korean Electrochemical Society
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• v.11 no.3
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• pp.184-189
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• 2008

Inhibitive effects of chromate, phosphate, sulfate, and borate on chloride pitting corrosion of Al have been investigated using cyclic voltammetry. During the anodic oxide growth, the critical concentration of chloride for pit initiation decreased in the order: chromate > phosphate > sulfate > borate, and the maximum pitting current density increases in the reverse order: chromate < phosphate < sulfate < borate. The decreasing pitting current density was observed in the successive polarization cycles, which was attributed to the aging of Al oxides and field relaxation at oxide/solution interface.

• Journal of the Korean institute of surface engineering
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• v.28 no.5
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• pp.289-299
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• 1995

The effects of phosphate coating have been studied on physical properties and corrosion resistance of painted aluminum alloy sheet for automobile body. The physical properties (surface roughness, paint adhesion, impact resistance and pencil hardness) and corrosion resistance(cyclic corrosion and filiform corrosion) were investigated. Phosphate coatings enhanced the physical properties of painted Al alloy sheet, especially paint adhesion after the 240hours water immersion test. Phosphate coating also markedly improved the resistance for cyclic corrosion and filiform corrosion of painted cold rolled steel and Zn-Ni plated steel sheet as well as painted Al alloy sheet. The corrosion resistance of painted Al sheets was varied with the concentration of free fluoride ion and metal additives like Ni and Mn in the phosphating bath. A maximum corrosion resistance was obtained at about 300ppm of fluoride ion and additives of Ni and Mn obviously increased the corrosion resistance of painted specimens.