• Journal of the Korean Ceramic Society
• /
• v.47 no.2
• /
• pp.99-105
• /
• 2010

The electrical transport properties of mayenite ($Ca_{12}Al_{14}O_{33}$ or $12CaO{\cdot}7Al_2O_3$; mostly abbreviated as $C_{12}A_7$) can be controlled in a wide range by varying the oxygen deficiency: At high temperatures mayenite becomes either an oxygen solid electrolyte, a mixed ionic/electronic conductor or an inorganic electride with metal-like properties upon chemical reduction (removing oxygen). The underlying defect chemistry can be understood on the basis of a relatively simple model-despite the complex cage structure: A point defect model based on the assumption that the framework $[Ca_{12}Al_{14}O_{32}]^{2+}$ acts as a pseudo-donor describes well the high temperature transport properties. It accounts for the observed conductivity plateau at higher oxygen activities and also describes the experimentally observed oxygen activity dependence of the electronic conductivity with -1/4 slope at temperatures between 800 and $1000^{\circ}C$. Doping effects in mayenite are still not well explored, and we review briefly the existing data on doping by different elements. Hydration of mayenite plays a crucial role, as Mayenite is hygroscopic, which may be a major obstacle for technical applications.

• Korean Journal of Chemical Engineering
• /
• v.35 no.11
• /
• pp.2191-2197
• /
• 2018

To remove tar and produce environment-friendly $H_2$, one of the promising routes is the sorption-enhanced steam reforming (SESR) process, in which the $CO_2$ sorbent is a key element. We prepared the $CO_2$ sorbents with $Ca_{12}Al_{14}O_{33}$ as carrier with various methods. Their characterizations were examined, and the sample prepared by solgel (SG) method showed the strongest CaO and $Ca_{12}Al_{14}O_{33}$ phases and the most excellent pore structure among all the samples. Then, a thermogravimetric experiment was conducted, and the results showed that the sample prepared by sol-gel (SG) method had the best $CO_2$ adsorption capacity and excellent long-term cyclic stability. Finally, the sorbent was used into the steam reforming experiments of tar. Under the action of the sorbent, the reforming reaction was enhanced in-situ, with the $H_2$ yield and concentration improved obviously, and especially, $H_2$ concentration can reach over 98.85%.

• Resources Recycling
• /
• v.29 no.6
• /
• pp.65-72
• /
• 2020

Black dross is a dark gray dross generated during the aluminum recycling process that uses flux, and contains NaCl, KCl, Al2O3, MgO, etc. Black dross is separated into soluble substances (NaCl, KCl) and insoluble substances (Al2O4, MgO) through the dissolution process. Soluble materials can be reused as salt flux, and Al2O3 and MgO can be upcycled to various ceramic materials through the synthesis process. In this study, Mayenite was synthesized using Al2O3 and MgO recovered from black dross, and the synthesis was performed according to the mixing ratio and reaction temperature. It was confirmed that when Mayenite was synthesized using black dross (spinel) and CaCO3, precursors were changed to Mg0.4Al2.4O4 and CaO at 700 ℃, and to Ca12Al14O33 (Mayenite) after 800 ℃. In the mixing conditions experiment, it was confirmed that the Mayenite XRD peak increased with increase of the CaCO3 content, and the Mg0.4Al2.4O4 XRD peak decreased. As a result of the BET analysis of the synthesized powder, the surface area decreased as the fine particles were grown and agglomerated in the process of generating mayenite.

• Journal of the Korean Ceramic Society
• /
• v.47 no.1
• /
• pp.19-25
• /
• 2010

Traditional Kr$\ddot{o}$ger-Vink (K-V) notation defines sites in ionic crystals as interstitial or belonging to host ions. It enables description and calculations of combinations of native and foreign defects, including dopants and substituents. However, some materials exhibit inherently disordered partial occupancy of ions and vacancies, or partial occupancy of two types of ions. For instance, the high temperature disordered phases of $Bi_2O_3$, $Ba_2In_2O_5$, $La_2Mo_2O_9$, mayenite $Ca_{12}Al_{14}O_{33}$, AgI, and $CsHSO_4$ are all good ionic conductors and thus obviously contain charged point defects. But traditional K-V notation cannot account for a charge compensating defect in each case, without resorting to terms like "100% substitution" or "Frenkel disorder". the former arbitrary and awkward and the latter inappropriate. Instead, a K-V compatible nomenclature in which the partially occupied site is defined as the perfect site, has been proposed. I here introduce it thoroughly and provide a number of examples.

• Journal of the Korean Chemical Society
• /
• v.43 no.4
• /
• pp.384-385
• /
• 1999

Two anhydrous crystal structures of fully dehydrated, $Ca^{2+}$- and $Tl^+$-exchanged zeolite X, TEX>$Ca_{18}Tl_{56}Si_{100}Al_{92}O_{384}($Ca_{18}Tl_{56}$-X;\alpha=24.883(4)\AA)$ and TEX>$Ca_{32}Tl_{28}Si_{100}Al_{92}O_{384}($Ca_{32}Tl_{28}$-X;\alpha=24.973(4)\AA)$ per unit cell, have been determined by single-crystal X-ray diffraction techniques in the cubic space group Fd3 at $21(1)^{\circ}C.$ $Ca_{18}Tl_{56}-X$ was prepared by ion exchange in a flowing stream of 0.045 M aqueous $Ca(NO_3)_2$ and 0.005 M $TlNO_3$. $Ca_{32}Tl_{28}-X$ was prepared similarly using a mixed solution of 0.0495 M $Ca(NO_3)_2$ and 0.0005M $TlNO_3$. Each crystal was then dehydrated at 360 $^{\circ}C$ and $2{\times}10^{-6}$ Torr for 2 days. Their structures were refined to the final error indices, $R_1=0.039\;and\;R_2=0.036$ with 382 reflections for $Ca_{18}Tl_{56}-X$ , and $R_1=0.046\;and\;R_2=0.045$ with 472 reflections for $Ca_{32}Tl_{28}$-X for which $/>3\sigma(I).$ In the structures of dehydrated $Ca_{18}Tl_{56^-}X\;and\;Ca_{32}Tl_{28}$-X, $Ca^{2+}\;and\;Tl^+$ ions are located at six crystallographic sites. Sixteen $Ca^{2+}$ ions fill the octahedral sites I at the centers of double six rings ($Ca_{18}Tl_{56}$-X:Ca-O=2.42(1) and O-Ca-O=93.06(4)$^{\circ}$; $Ca_{32}Tl_{28}$-X Ca-O=2.40(1) $\AA$ and O-Ca-O=93.08(3)$^{\circ}$). In the structure of $Ca_{18}Tl_{56}$-X, another two $Ca^{2+}$ ions occupy site II (Ca-O=2.35(2) $\AA$ and O-Ca-O=111.69(2)$^{\circ}$) and twenty six $Tl^+$ ions occupy site II opposite single six-rings in the supercage; each is 1.493 $\AA$ from the plane of three oxygens $(Tl-O=2.70(8)\AA$ and O-Tl-O=92.33(4)$^{\circ}$). About four $Tl^+$ ions are found at site II',1.695 $\AA$ into sodalite cavity from their three oxygen plane (Tl-O=2.81 (1) and O-Tl-O=87.48(3)). The remaining twenty six $Tl^+$ ions are distributed over site III'(Tl-O=2.82 (1) $\AA$ and Tl-O=2.88(3)$^{\circ}$). In the structure of $Ca_{32}Tl_{28}$-X, sixteen $Ca^{2+}$ ions and fifteen $Tl^+$ ions occupy site III' (Ca-O=2.26(1) $\AA$ and O-Ca-O=119.14(4)$^{\circ}$; Tl-O=2.70(1) $\AA$ and O-Tl-O=92.38$^{\circ}$) and one $Tl^+$ ion occupies site II'. The remaining twelve $Tl^+$ ions are distributed over site III'. It appears that $Ca^{2+}$ ions prefer sites I and II in that order and $Tl^+$ ions occupy the remaining sites.

• Economic and Environmental Geology
• /
• v.45 no.6
• /
• pp.643-659
• /
• 2012

The Chungju Fe-REE deposit is located in the Kyemyeongsan Formation of the Ogcheon Group. The Kyemyeongsan Formation includes meta-volcanic rocks and pegmatite hosted REE deposit which show different kind of REE-containing minerals. The meta-volcanic rocks hosted REE deposits' main REE minerals are allanite, zircon, apatite, and sphene, whereas the pegmatite hosted REE deposits is mainly composed of fergusonite, and karnasurtite, zircon, thorite. The meta-volcanic rock hosted major REE mineral is allanite as the form of aggregation and contains 23.89-29.19 wt% TREO (Total Rare Earth Oxide), 4.71-9.92 wt% $La_2O_3$, 11.30-14.33 wt% $Ce_2O_3$, 0.11-0.29 wt% $Y_2O_3$, 0.15-0.94 wt% $ThO_2$, as a formula of (Ca, Y, REE, Th)$_{2.095}$(Mg, Al, Ti, Mn, $Fe^{3+})_{2.770}(SiO_4)_{2.975}(OH)$. Accompanying REE in a coupled substitution for $Ca^{2+}$ (M1 site) and $Al^{3+}-Fe^{2+}$ (M2 site) leads to a large chemical variety. Due to the allanite's high contents of Fe, it belongs to Ferrialanite. The pegmatite hosted deposit's domi-nant REE mineral is fergusonite as prismatic or subhedral grains associated with zircon, fluorite and karnasurtite. Geochemical composition of the fergusonite($YNbO_4$) suggests substitution of Y-REE and Y-Th in A-site, and Nb-Ta-Ti in B-site, furthermore the proportion of $Y_2O_3$ and $Nb_2O_5$ is oddly 1:1.5 comparing to the ideal ratio 1:1 and Nb is higher than Y, also A-site Y actively substitutes with REE. Karnasurtite in pegmatite variously ranges 9.16-22.88 wt% $Ce_2O_3$, 2.15-9.16 wt% and $La_2O_3$, 0.44-10.8 wt% $ThO_2$, as a calculated formula (Y, REE, Th, K, Na, Ca)$_{1.478}(Ti, Nb)_{1.304}$(Mg, Al, Mn, $Fe^{3+})_{0.988}$(Si, P)$_{1.431}O_7(OH)_4{\cdot}3H_2O$. Firstly the 870-860 Ma is the initial age of the supercontinent Rhodinia dispersal and subsequent A-1 type volcanism, which contains Fe, REE, and HFS(High Field Strength elements; Nb, Zr, Y etc.) elements in Fe-rich meta-volcanic rocks dominant Kyemyeongsan Formation, might mineralized allanite. Another synthesis is that regional metamorphism at late Paleozoic 300-280 Ma(Cho et al., 2002) might cause allanite mineralization. Also pegmatite REE mineralization highly related to the granite intrusion over the Chungju area in Jurassic(190 Ma; Koh et al., 2012). Otherwise above all, A-1 type volcanism at the same time of the Kyemyeongsan Formation development, regional metamorphism and pegmatite, might have caused REE mineralization. Although REE ore bodies display a close spatial association, each ore bodies display temporal distinction, different mineral assemblage and environment of ore formation.

• Economic and Environmental Geology
• /
• v.30 no.1
• /
• pp.35-49
• /
• 1997

The coal formation of the Deokpyeong area are interbedded along metapelites of the Ogcheon Supergroup, which are composed mainly of graphite, quartz, muscovite and associated with small amounts of biotite, chlorite, pyrite and barite. The ratios of $SiO_2/Al_2O_3$, $Al_2O_3/Na_2O$ and $K_2O/Na_2O$ of the coaly metapelite are variable and wide range from 1.80 to 10.21, from 27.8 to 388.8 and from 7.6 to 61.8, respectively. These coal formation were deposited in basin of marine environments, and the REE of these rocks are not influenced with metamorphism and hydrothermal alterations on the basis of $Al_2O_3$ versus La, La against Ce, the ratios of La/Ce (0.19 to 0.99) and Th/U (0.02 to 4.75). These rocks also show much variation in $La_N/Yb_N$ (1.19 to 22.89), Th/Yb (0.14 to 21.43) and La/Th (0.44 to 13.67), and their origin is explained by derivation from a mixture of sedimentary and igneous rocks. The wide range in trace and REE element characteristics as Co/Th (0.12 to 2.78), La/Sc (0.33 to 10.18), Sc/Th (0.57 to 5.73), V/Ni (8 to 2347), Cr/V (0.02 to 0.67) and Ni/Co (1.56 to 32.95) of these coaly metapelites argues for inefficient mixing of the various source lithologies during sedimentation. Deep to pale green barium-vanadium muscovites (vanadium-oellacherite) have been found in this coal formations. Modes of occurrence and grain size of muscovite are heterogeneous, but most of the barium and vanadium-bearing muscovites occur along the boundaries between graphite and quartz grains, ranging from 200 to $350{\mu}m$ in length and from 40 to $60{\mu}m$ in width. Results of X-ray diffraction data of the minerals characterized to be monoclinic system with $a=5.249{\AA}$, $b=8.939{\AA}$, $c=20.924{\AA}$ and ${\beta}=95.894^{\circ}$. Representative chemical formula of the muscovite was $(Na_{0.09}K_{1.44}Ba_{0.46})(Al_{2.75}Ti_{0.07}V_{0.56}Fe_{0.08}Mg_{0.50})(Si_{6.12}Al_{1.88})O_{22}$. The V possibly substitute octahedral Al, and the Ba is coupled substitution of $K^+Si^{4+}=Ba^{2+}Na^+Ca^{2+}$, which compositional ranges of V and Ba are from 0.42 to 0.69 and from 0.34 to 0.56 based on $O_{22}$, respectively. Formation mechanism of the barium-vanadium muscovites in the coaly metapelite is shown that the formed by high pressure and temperature from regional metamorphism origanated during diagenesis at the interface between a basinal brine and organic matter.

• Journal of the Speleological Society of Korea
• /
• no.74
• /
• pp.23-31
• /
• 2006

(1) Kaeusetgul Cave in Kimnyong-Ri, Jeju-Do, Korea. Kaeuset-gul Cave (KC) is situated in NNE area of the Manjang-gul cave (125m a.s.l.). Kaeuset-gul Cave lies at $126^{\circ}45'22"$ E in longitude and $33^{\circ}33'09"$ N in latitude. The coast belong Kimnyeong-Ri, Kujwa-eup, Jeju-Do. Altitude of the cave-entrance is 10m and length of the cave is 90m. Lava hand-specimens of KC are studied by X-ray fluorescence analysis (XRF). Average major chemical components of specimens from KC is as follows (wt.%); $SiO_2=47.03$, $TiO_2=3.16$, $Al_2O_3=18.41$, FeO*=13.53, MnO=0.14, MgO=5.05, CaO=8.66, $Na_2O=2.81$, $K_2O=0.67$, $P_2O_5=0.55$ in KC. Polarizing microscopic studyindicates that these specimens are described of alkali-basalt. (2) Tachibori Fuketsu (Cave) in Shizuoka Prefecture, Fuji Volcano, Japan Tachibori Fuketsu lies attoward the south in skirt of the Fuji volcano, $138^{\circ}42'04"$ east longitude and $35^{\circ}18'00"$ north latitude. The location of cave entrance is 2745, Awakura, Fujinomiya-shi, Shizuoka Prefecture. The above sea level and length of Tachibori Fuketsu are 1,170m and 82m. Average major chemical components of specimens from cave areas follows (Total 100 wt.%) ; ($SiO_2$=50.52, $TiO_2$=1.69, $Al_2O_3$=15.47, FeO*=13.13, MnO=0.20, MgO=5.97, CaO=9.17, $Na_2O$=2.52, $K_2O$=0.94 and $P_2O_5=0.40).$ Polarizing microscopic study indicates that these specimens may belong to tholeiite-basalt series. According to polarizing microscopic study, Au (Augite), P1 (Plagioclase), and O1 (Olivine) are contained as phenocryst minerals. (3) Gorely Cave in Kamchatka Peninsula, Russia Gorely caldera is located at the southeastern part of Kamchatka Peninsula, about 75km southwest of Petropavlovsk-Kamchatskiy.. Gorely lava caves are situated in NHE area of Mt. Gorely volcano (1829m a.s.1.). One of lava cave (Go-9612=K-1) lies at $158^{\circ}00'22"$ east longitude and $52^{\circ}36'18"$ north latitude. The elevation of cave entrance is about 990m a.s.1. and the main cave extends in the NNW direction for about 50m by 15m wide and 5m in depth. The cave of K-3is near the K-1 cave. "@Lava hand-specimens K-1 and K-3 caves are studied by X-ray fluorescence analysis and polarizing microscopic observation. Average major chemical components of specimens from these caves are as follows (wt.%) ;($SiO_2$=55.12, $TiO_2$=1.25, $Al_2O_3$=16.07, T-FeO* =9.41, MnO=0.16, MgO=5.01, CaO=7.21, $Na_2O$=3.39, $K_2O$=1.92, $P_2O_5$=0.45) and these values indicate that the Gorely basaltic andesite belong to high alumina basalt. Polarizing microscopic study indicates that these specimens are described of Augite andesite.

• Economic and Environmental Geology
• /
• v.32 no.3
• /
• pp.227-236
• /
• 1999

The Daeyou pegmatite is located at the central westerm part of the peninsula. Geology of the mine area consists mainy of pre-Combrian granite gneiss and leucoratic gneiss which are intruded by Mesozoic granites. The pegmatite deposits occur within granite gneiss. Most of pegmatites contain quartz, perthite, microcline-perthite, microcline, sodic plagioclase and tourmaline as dominant minerals with accessory minerals of mica (muscovite, biotite, sericite)and pyrite. Tourmaline occurs as four types: 1) unaltered single crystals, 2) patially sericitized grains bordered by sericite assemblage, 3) tourmaline intergrown with feldspar and qurtz grains, and 4) tourmaline introduced veinlet/ On the basic of optical, X-ray diffraction and chemical analysis, the composition of tourmaline mostly falls on the schorl-elbaite join, in the composition of tourmaline mostly falls on the schorl-elbraite join, in the composition of schorl end member from 0 to about 50%. In spite of the different occurrences, chemical composition of tourmaline shows the limited ranges as follows: $SiO_{2}$ (34.53~35.01 wt.%), $Al_{2}O_{3}$ (33.58~34.26wt.%), FeO (13.73~14.17wt.%), $Na_{2}O$ (1.60~1.72wt.%), MgO (0.56~0.72wt.%), MnO (0.12~0.18wt.%), CaO (0.02~0.06wt.%), $K_{2}O$(0.02~0.03wt.%) $TiO_{2}$ (0.02~0.05wt.%) and $Cr_{2}O_{3}$ (0.02~0.03wt.%). K-Ar ages of the muscovite and sericite fall between 1010$\pm$15 and 1074$\pm$16Ma and between 161.56$\pm$3.09 and 161.67$\pm$Ma, respectivrly. This means that hydrothrmal alteration occurred during middle Jurassic, whereas the pegmatite was initally formed during the late proterozoic age.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.2
• /
• pp.152-160
• /
• 2021

Converter steel slag(BOF slag) is a vast amount of solid waste generated in the steelmaking process which has very low utilization rate in Korea. Due to the presence of free CaO which can derive bad volume stability in BOF slag, it usually land filled. For recycling BOF and identify its applicability as fine aggregate, this study investigates the fundamental characteristics of mortar with cement replaced ferronickel slag(FNS), which has the potential to be used as a binder. The results suggest that the mineral phases of BOF slag mainly include larnite(CaSiO₄), mayenite(Ca₁₂Al₁₄O₃₃) and wuestite(FeO) while olivine crystallines are shown in FNS. The results of flow and setting time reveals that the flowability and process of hardening increased when the amount of FNS and BOF slag incorporated was increased. The length change shows that the amount of change in the length of the mortar was almost constant regardless of mix proportion while compressive strength was reduced. Micro structure test results revealed that FNS or/and BOF slag mix took a long time to react in the cement matrix to form a complete hydration products. To achieve the efficient utilization of B OF slag as construction materials, proper replacement rate is necessary.