• Journal of the Korean Ceramic Society
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• v.45 no.5
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• pp.268-275
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• 2008

In high temperature ceramic glazes, a stable range of pink-red colors producing $Cr_2O_3-SnO_2-CaO-SiO_2$ pigments are factored by Cassiterite and Malayaite relationship with $Cr_2O_3$. The experiment described the effect of $CrCl_3$ by adding $H_3BO_3$ as a mineralizer to increase the formation of Malayaite crystal, substituting $CrCl_3$ instead of $Cr_2O_3$ in pigment as a chromophore. Synthesized pigments were analyzed by XRD, FT-IR, Raman Spectroscop, UV and UV-vis. The result shows the differences in amount of crystal phases and oxidation state of Cr ion, which causes the color change. The melting point of $CrCl_3$ is lower than $Cr_2O_3$ which act as a mineralizer and makes the pigment synthesized in lower temperature at $1200^{\circ}C$. Holding 3 h firing at $900^{\circ}C$ where the synthesize forms shows better effect of Malayaite crystal phases and increasing engaged effect of $CrCl_3$ where the color pigmentation is more defined then in $Cr_2O_3$.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.2
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• pp.251-264
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• 2000

Organic removal from synthetic wastewater by electrochemical methods was investigated with various operating parameters, such as current density, retention time, electrode gap and $Cl^-/COD_{Cr}$ ratio. In electrolysis, dioxide iridium coated titanium ($IrO_2/Ti$) and stainless steel plate were used for anode and cathode respectively. The $COD_{Cr}$ removal efficiencies between plate type anode and net type anode were about same effect, but electrolytic power using net type anode is low than plate type anode. The $Cl^-/COD_{Cr}$ ratio was about $1.3kgCl^-/kgCOD_{Cr}$ when organic removal obtained 70 %, $Cl^-/COD_{Cr}$ ratio needs $2.2kgCl^-/kgCOD_{Cr}$ so as to organic completely remove. The removal efficiency of organics increased with current density, retention time and $Cl^-/COD_{Cr}$ ratio, but decreased with increasing electrode gap. The relationship of operating conditions and $COD_{Cr}$ removal efficiencies are as follows. $$COD_{Cr}(%)=80.0360(Current\;density)^{0.4451}{\times}(HRT)^{0.8102}{\times}(Gap)^{-0.4915}{\times}(Cl^-/COD_{Cr})^{0.5805}$$ There existed a competition between the removals for $COD_{Cr}$ and ammonium during electrolysis, the removal of ammonium was shown to be dominant and $COD_{Cr}$ removal was low. But $COD_{Cr}$ removal was raised as addition of alkalinity.

• Journal of the Korean Ceramic Society
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• v.46 no.4
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• pp.405-412
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• 2009

In high temperature ceramic glazes, a stable range of pink-red colors that produced $Cr_2O_3-SnO_2-CaO-SiO_2$ pigments were factored by Cassiterite($SnO_2$) and Malayaite($CaSnSiO_5$) by $Cr_2O_3$. The experiment examined the influence of $CrCl_3$, a Sn-Cr substitution added with a mineralizer ($H_3BO_3$), as a chromophore in pigments. The experiment also studied the effect of $H_3BO_3$ (2 wt%) when added to malayaite($CaSnSiO_5$) to see if the crystalline reaction will increase. $Cr_2O_3$ was also substituted with $CrCl_3$ in order to prove how much influence $CrCl_3$ had on the $H_3BO_3$. Malayaite and cassiterite were the basic compound materials and the experiment was conducted both with and without mineralizers (2 wt% of $H_3BO_3$). Each compound was synthesized at 800, 1000, 1200, 1300, 1400, $1500^{\circ}C$ for 2 h. Synthesized pigments were analyzed by XRD, FT-IR and UV-Vis. The temperature variation produced two crystal phases that showed the different engaging effects of Cr oxidation. $CrCl_3$ produced a better effect on the malayaite crystal phase, resulting in a more defined pigmentation of the pink-red coloration compared to $Cr_2O_3$.

• Journal of the Korean Ceramic Society
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• v.46 no.4
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• pp.372-378
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• 2009

The coloring agents $Cr_2O_3$ and $CrCl_3$ were manipulated in this study to synthesize ZnO-$Al_2O_3-Cr_2O_3$ system pigments by changing their mixing ratio. The addition of varying amounts of mineralizer was also tested to obtain better color development of the pink pigment. In the synthesis of ZnO- $Al(OH)_3-Cr_2O_3-CrCl_3$ pigments, the best composition is $Cr_2O_3$-0.1 mole and $CrCl_3$-0.2 mole when $Cr_2O_3$ is partially substituted with $CrCl_3$ to synthesize them. Among the $ZnAl_{1.6-x}Cr_{0.2+x}O_4$ compositions to which a mineralizer was not added, ZnO-1mole, $Al(OH)_3$-1.7 mole, $Cr_2O_3$-0.075 mole, and $CrCl_3$-0.15 mole showed a desirable pink hue. The measurements of pigments $L^*$, $a^*$ and $b^*$, were $L^*$ 81.81, $a^*$ 16.65 and $b^*$ 0.45, and when the synthesized pigments were applied to a zinc glaze, the measurements were $L^*$ 60.41, $a^*$ 28.39, and $b^*$ 16.97. When adding a mineralizer, a 2 wt% addition resulted in the most favorable pink color. The composition for the most favorable result that included a mineralizer was $Al(OH)_3$-1.8 mole, $Cr_2O_3$-0.05 mole, and $CrCl_3$-0.1 mole, and the calcination temperature was $1250^{\circ}C$. The pigment color analysis showed $L^*$ 82.52, $a^*$17.14 and $b^*$-1.18, and the measurements of $L^*$, $a^*$ and $b^*$ in the glaze were $L^*$ 60.97, $a^*$ 28.77 and $b^*$ 13.72.

• Korean Journal of Materials Research
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• v.10 no.7
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• pp.471-477
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• 2000

Corrosion behavior of Fe-Ni-Cr alloy in molten salts of LiCl and LiCl-$Li_2O was investigated in the tempera-ture range of $650~850^{\circ}C$. In the molten salt of LiCl, and internal oxidation of Fe occurred in the KSA(Kaeri Superalloy)-1 alloy without containing Cr, while a dense protective oxide scale of $LiCrO_2$ was formed in the KSA-4, Incoloy 800H and KSA-5 alloys. In the mixed molten salt of LiCl-$Li_2O$, internal oxidation of Fe and Cr took place in the KSA-1 and KSA-4 alloys, respectively. Non-protective porous oxide scales consisting of $LiCrO_2$ and Ni were formed in the Incoloy 800H and KSA-5. The corrosion rate of the alloys increased with the increase in Cr content and the corrosion rate followed the parabolic law for the alloy containing Cr content less than 8%, and the linear law for the alloy containing Cr content more than 8%. Such a corrosion behavior of the alloy in the mixed molten salt of LiCl-$Li_2O$ was interpreted in terms of the basic fluxing mechanism of protective oxide scale of $Cr_2O_3$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.17 no.6
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• pp.264-271
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• 2007

The inorganic pigments of $Fe_2O_3-CoO-Cr_2O_3-MnO_2$ were synthesized by the co-precipitation method. $FeCl_3,\;CoCl_2,\;CrCl_3\;and\;MnCl_2$ are used for the starting raw materials, and 2 N-KOH for precipitator. $MnCl_2$ is secured with 10 mole%, and 6 composition ratios are used with three ingredients to synthesize the pigments. The samples were calcined at $1350^{\circ}C/1.5h$. The resulting pigments were characterized by using XRD, FT-IR, SEM, and UV spectrophotometer. 6wt% pigments were applied to lime glaze and lime-barium glaze respectively firing at $1260^{\circ}C$ for oxidation atmosphere and $1240^{\circ}C$ for reduction one. The results of color analysis by using UV spectrophotometer showed black, bluish black and dark grayish green.

• Journal of the Korean Ceramic Society
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• v.46 no.6
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• pp.615-620
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• 2009

The present research was performed to determine the optimal firing condition and holding time for malayaite crystal, which is responsible for the stable pink-red coloration in glaze at high temperatures, using Cr$Cl_3$ as chromophore for the synthesis of $Cr_2O_3-SnO_2-CaO-SiO_2$ system pigments. The malayaite crystal was influenced by the raw materials used for synthesis, firing temperature, and holding time. Thus there are differences in the crystal phase and in the coloration according to the condition of synthesis. When Cr$Cl_3$ was used as chromophore, the pigment could be synthesized at lower temperatures, because Cr$Cl_3$ melts at $1500{^{\circ}C}$, which is much lower than the temperature at which $Cr_2O_3$ melts (higher than $2435{^{\circ}C}$). And the employed Cr ion showed a change in oxidation state. When a mineralizer was used to improve the employment of malayaite and the Cr ion, and the low temperature was maintained at which the malayaite crystal is produced, the production of malayaite crystal was promoted and the employment of chromophore was also promoted in the oxidation state of Cr (IV). The results of the experiment showed that the optimal firing condition was 18 h of holding time at $800{^{\circ}C}$, using Cr$Cl_3$ as chromophore, followed by 2 h at the raised temperature of $1150{^{\circ}C}$. The change in coloration of the Cr (IV) employed by malayaite showed a very rich color of red. Thus it was possible to effectively synthesize sphene-pink pigments with more red tint at a low temperature.

• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.354-359
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• 2018

NaCl-induced hot corrosion behavior of ASTM T22 (Fe-2.25Cr-1Mo), T91 (Fe-9Cr-1Mo), T92 (Fe-9Cr-1.8W-0.5Mo), 347HFG (Fe-18-Cr-11Ni), and 310H (Fe-25Cr-19Ni) steels was studied after spraying NaCl on the surface. During corrosion at $600-800^{\circ}C$ for 50-100 h, thick, non-adherent, fragile, somewhat porous oxide scales formed. All the alloys corroded fast with large weight gains owing to fast scaling and destruction of protective oxide scales. Corrosion rates increased progressively as the corrosion temperature and time increased. Corrosion resistance increased in the order of T22, T91, T92, 347HFG, and 310H, suggesting that the alloying elements of Cr, Ni, and W beneficially improved the corrosion resistance of steels. Basically, Fe oxidized to $Fe_2O_3$, and Cr oxidized to $Cr_2O_3$, some of which further reacted with FeO to form $FeCr_2O_4$ or with NiO to form $NiCr_2O_4$.

• Journal of the Korean Chemical Society
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• v.33 no.1
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• pp.11-17
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• 1989

Pyrazinium chlorochromate and dipyrazinium trichromate which are pyrazinium salts were prepared by the each reaction of pyrazine with chromium trioxide under the presence of HCl and $CH_2Cl_2$. These compounds wese nonhygroscopic and were solved in water very well. Physical properties such as solubility, pH, electrical conductivity, and melting point were measured. These compounds were considered to be ionic ; $C_4H_4N_2H^+$, $CrO_3Cl^-$, $Cr_3O^{2-}_{10}$ by the measurement of electrical conductivity. It was found that CrO$_3$ was formed in the first decomposition process of salts and it was changed into $Cr_2O_3$ in the second process as its weight is decreased. It was also found that especially under the same condition dipyrazinium salt was in the form of isopoly ($Cr_2O^{2-}_{10}$)anion which has been thought to be in the form of $Cr_2O^{2-}_{7}$ obtained from pyridine.

• Journal of the Korean institute of surface engineering
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• v.26 no.3
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• pp.149-157
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• 1993

In the study of TAB(Tape Automated Bonding)technologies, Cu-Cr sputtered seed layer has been used to improve the adhesion between Polyimide and Cu film and electrical properties. But the Cu electrodeposit on Cu-Cr film had poor adhesion or powder-like form due to the surface Cr oxides on the Cu-Cr film. By means of activating the Cu-Cr film with the oxalic acid and phosphoric acid, the Cu film with the improved adhesion could be coated on the Cu-Cr sputtered film in CuSO4 solution. The etching rate was compared with increasing the Cr content of the sputtered Cu-Cr film, and anodic polarization curve in FeCl3 solution was investigated. With increasing the Cr content, the etching rate was reduced. The clean etching cross section could be obtained with increasing the concentration of FeCl3 solution. But above the 13 w/o Cr content, Cu-Cr sputtered film could not bed etched cleanly only with FeCl3 solution and additives were needed.