• Journal of Powder Materials
• /
• v.28 no.2
• /
• pp.164-172
• /
• 2021

Titanium is the ninth most abundant element in the Earth's crust and is the fourth most abundant structural metal after aluminum, iron, and magnesium. It exhibits a higher specific strength than steel along with an excellent corrosion resistance, highlighting the promising potential of titanium as a structural metal. However, titanium is difficult to extract from its ore and is classified as a rare metal, despite its abundance. Therefore, the production of titanium is exceedingly low compared to that of common metals. Titanium is conventionally produced as a sponge by the Kroll process. For powder metallurgy (PM), hydrogenation-dehydrogenation (HDH) of the titanium sponge or gas atomization of the titanium bulk is required. Therefore, numerous studies have been conducted on smelting, which replaces the Kroll process and produces powder that can be used directly for PM. In this review, the Kroll process and new smelting technologies of titanium for PM, such as metallothermic, electrolytic, and hydrogen reduction of TiCl₄ and TiO₂ are discussed.

• Journal of Korea Foundry Society
• /
• v.32 no.6
• /
• pp.261-268
• /
• 2012

The effects of thickness, base element and additive to inoculant on the number of eutectic cells and chill depth of thin-section gray cast iron were investigated. Meanwhile the number of eutectic cells increased by inoculation, chill depth decreased. The former decreased and the latter increased by holding the melt at the temperature range between 1,450 and $1,500^{\circ}C$. The former was more for the thinner casting with the thickness of 5 mm than the other. The result of thermal analysis coincided well with the change of macrostructure. The former increased and the latter decreased with the increased contents of carbon, silicon and the silicon content by inoculation. The former decreased and the latter increased with increased manganese content. The number of eutectic cells decreased as the amounts of rare earth and the bismuth added to this inoculant increased. With the addition of sulfur of 0.10 wt% of the weight of this inoculant, the maximum number of eutectic cells was obtained.

• Advances in materials Research
• /
• v.4 no.4
• /
• pp.227-233
• /
• 2015

We present a method, supported by theoretical analysis, for optimizing the usage of the critical rare earth element dysprosium in $Nd_2Fe_{14}B$ (NdFeB)-based permanent magnets. In this method, we use Dy selectively in locations such as magnet edges and faces, where demagnetization factors are largest, rather than uniformly throughout the bulk sample. A200 nm thick Dy film was sputtered onto a commercial N-38, NdFeB magnets with a thickness of 3 mm and post-annealed at temperatures from $600-700^{\circ}C$. Magnets displayed enhanced coercivities after post-annealing and as much as a 5 % increase in the energy product, while requiring a total Dy content of 0.06 wt. % - a small fraction of that used in the commercial grade Dy-NdFeB magnets. By assuming all Dy diffused into NdFeB magnets, the improvement in energy product corresponds to a saving of over 1% Dy (critical element). Magnets manufactured using this technique will therefore be higher performing which would potentially broaden the application space of these magnets in the traction motors of hybrid and pure electric vehicles, and wind generators.

• Analytical Science and Technology
• /
• v.20 no.6
• /
• pp.468-473
• /
• 2007

The chemical composition distribution of the surface samples collected from the loess plateau in China were estimated. Major elements concentration distribution difference between 10 different sampling site were not found except sample 3. This sample had higher contents of Ca, Mg, LOI and lower contents of Si, Fe, P, Na, Ti. And also, minor element contents such as Ba, Cr, Nb, Pb, Rb, Zr, V were lower than other samples. UCC-normalized abundances of the most elements were within $0.5-1.5{\times}UCC$ and Cr showed enrichment aspect. Rare-earth element (REE) analysis results showed light REE enriched pattern compared to heavy REE with negative Eu anomaly in condrite-normalized REE pattern.

• Journal of the Mineralogical Society of Korea
• /
• v.25 no.4
• /
• pp.295-304
• /
• 2012

Ilmenite mine was developed in the anorthosites which intruded Precambrian Jirisan gneiss complex in Wolheongri, Okjong-myeon, Hadong. Ti-ore bodies are confined to the intercumulated type anorthosites, where REE-bearing allanite occurred as veins. The chemistry of allanites shows relatively low in CaO (11.02~12.81 wt%), but high in ${\Sigma}R_2O_3$ (R = Ce, La, Nd) (17.21~21.58 wt%), respectively. Abnormally high radioactive detection ascribes to the presence of small particles of thorium mineral known as thorite ($ThSiO_4$). Thorite shows 65~72.78 wt% ($ThO_2$) and 5.49~12.78 wt% ($UO_2$) in composition. The radioactive prospecting could be a strong tool to find REE-bearing allanite which is closely associated with Ti-ore deposits.

• Journal of the Korean earth science society
• /
• v.24 no.4
• /
• pp.337-345
• /
• 2003

Surficial sediments from the northern coastal area of Jeju Island, southeastern Yellow Sea (South Sea of Korea) were analyzed for grain-size texture, some geochemical characteristics and clay mineralogy in order to assess their provenance. Rare-earth element compositions and some geochemical discrimination diagrams, especially of Ti/Al, Nb/Al and Rb/Al ratios, were revealed to be useful indices for identifying the origin of sediments. These indices, together with clay mineral compositions, suggest that the coarse-grained sediments originate from the volcanic rocks of Jeju Island, whereas the fine-grained sediments are derived from Chinese rivers, especially the Changjiang River. The oceanic circulation pattern and the physical-chemical properties of seawater in the Yellow and East China seal support the possibility that the fine-pained Changjiang (Yangtze River) sediments can reach the coastal area of Jeju Island (southeastern Yellow Sea).

• The Journal of the Petrological Society of Korea
• /
• v.8 no.2
• /
• pp.57-70
• /
• 1999

The volcanic rocks of Ulleungdo reveal very high alkali element abundances and most of them have high K20/Na20 ratios and belong to potassium-series. Ulleungdo volcanics show very wide range of variation in their composition from basalts to trachytic basalt, basaltic trachyandesite, trachyandesite, and finally to trachyte on total alkali-silica diagram. Such a general trend of compositional variation can be explained well by differentiation due to fractional crystallization of various minerals. Olivine, clinopyroxene, plagioclase, ilmenite, and apatite are suggested as the major fractionated minerals. Ulleungdo volcanics show Nb/U and PbICe ratios similar to oceanic volcanics such as MORB and OIB, but significantly different .from volcanic rocks of island arc environments, which suggest that they are not directly related with subduction along the Japanese arc. LREE abundances of Ulleungdo volcanics are highly enriched compared with HREE abundances ((La)N=193-420, (L~)~=7.5-19.5).O nly trachyte-1 show appreciable negative Eu anomalies among various rock types, which suggests significant amount of plagioclase were fractionated. However, trachyte-2, trachyte-3, phonolite, and pumice reveal quite different variation trend of trace and rare earth element abundances from trachyte-1, which suggest that they have originated from different magma batches and have experienced different differentiation processes. A prominent bimodal distribution, thus lacking of intermediate composition, is observed from the Ulleundo volcanics.

• Journal of the Korean earth science society
• /
• v.25 no.4
• /
• pp.251-264
• /
• 2004

The Charnockite in Sancheong region is quarzofeldspathic rock containing orthopyroxene and garnet with a color dark than common granitic rocks. The Chamockite are mostly massive and medium to coarse-grained with K-feldspar phenocryst, but reveal weak foliation. The rock consist mainly of quartz, K-feldspar, plagioclase and orhopyroxene, with biotite, garnet, and anthophyllite. In petrochemistry, the Chamockite has 61-65% $SiO_2$ contents, varying gradually into the margin contacted with orthogneiss, which have compositions of felsic igneous rocks. Major element show almost systematical variation with those of the marginal orthogneisses, except the hornblende gneiss and anorthosite. The Charnockite and orthogneisses show the tholeiitic differentiational trend. Trace and rare earth element abundance patterns in the Charnockite show remarkable negative Sr and Eu anomalies similar to orthogneisses, but different from the hornblende gneiss and anorthosite. Eu contents of the Charnockite are richer than that of orthogneisses. The metamorphic condition of the Charnockite were tested by an orthopyroxene-garnet geotherrnorneter and a plagioclase-garnet geobarometer. Estimated P-T conditions are about $761^{\circ}C$ and 7 kbar at peak metamorphism, but $653^{\circ}C$ and 6.4 kbar at retrograde metamorphism. This suggests that the Charnockite have from an early stage of high-grade metamorphism to represent the granulite facies and then to a late stage medium-grade metamorphism belonging to the amphibolite facies.

• The Journal of the Petrological Society of Korea
• /
• v.27 no.2
• /
• pp.97-104
• /
• 2018

The U-Pb isotopic and rare earth element compositions of zircon were measured using a SHRIMP from a tonalitic gneiss sample DE43 in Daeijak Island, central Korea. Zircon crystals, up to ${\sim}300{\mu}m$ in diameter, rarely contain thin overgrowth rims. In contrast to Paleoproterozoic cores, the $^{206}Pb/^{238}U$ ages of $256{\pm}23Ma(1{\sigma})$, and $221{\pm}7Ma(1{\sigma})$ were yielded from two spot analyses on the overgrowth rims of zircon. The rims are geochemically characterized by low Th/U ratios (<0.01) and strongly depleted light rare earth elements. The Permian-Triassic apparent ages of zircon are consistent with the $^{208}Pb/^{232}Th$ ages dated from allanite ($227{\pm}7Ma(t{\sigma})$) in the same sample within uncertainties, indicating an equilibrium growth of allanite and zircon at ~227 Ma. On the other hand, the younger $^{208}Pb/^{232}Th$ and $^{206}Pb/^{238}U$ ages ($213{\pm}4Ma(t{\sigma})$ and $186{\pm}9Ma(t{\sigma})$, respectively) of allanite may result from Pb loss due to the infiltration of alkali fluids from Late Triassic and Jurassic granitoids nearby.

• Journal of Conservation Science
• /
• v.35 no.5
• /
• pp.430-439
• /
• 2019

This study investigates the characteristics of ridge-end tiles excavated from temple sites in Sabi Baekje. Analyses were carried out to evaluate the chemical and mineralogical compositions of the excavated samples. All the samples except one from the Gunsu-ri temple exhibit a similar element distribution pattern in rare earth element contents. However, major and trace element contents differ because the mixing method used in each sample depends on the type of ridge-end tile. The mineral components of the tiles were grouped into three types, irrespective of the excavated areas. Group 2 and 3 were probably developed in high-temperature fires in comparison with Group 1; this is verified by the Fe₂O₃ content of more than 5 wt% in these samples. In conclusion, the raw materials utilized in each ridge-end tile are prone to have changed according to the time of use of the tile, regardless of the excavated site.