• Journal of the Korean Ceramic Society
• /
• v.25 no.6
• /
• pp.685-693
• /
• 1988

From leaching of Korean native halloysite with hot sulfuric acid, active species of siliceous aluminosilicate are obtained as residue, which gives the mole ratio of SiO2/Al2O3 10 and substantially removes most acid-soluble impurities. By dissolving the residue in sodium hydroxide at an ambient temperature sodium silicate solution is prepared, this is used for zeolite synthesis as one of starting materials. In order to prepare zeolite Type 4A thereform, addition of a proper aluminum source is made so that the composition of the reactant materials may be of the following mole ratios : Na2O/SiO2=1.2-1.5, SiO2/Al2O3=1.8-2.0 and H2O/Na2O=34-45 By careful control of ageing time and temperature, subsequent crystal growth is induced into microfine zeolite 4A, which gives optimum particle size distributjion being suitable for detergent builder. The zeolite products thus obtained and highly competitive with those from the use of the refined clay in comparison of their calcium exchange capacity, whiteness and particle size distribution. The present method shows a marginal advantage over the existing procedures requiring neitherseparate purification nor calcinating otherwise necessary for the raw clay ores in use.

• YAKHAK HOEJI
• /
• v.29 no.4
• /
• pp.176-182
• /
• 1985

As a part of the studies on adsorptive properties of Korean halloysite clays, Hadong white clays of premium grade were examined for geometric pore structured by mercury porosimetry and for specific surface areas by nitrogen adsorption according to the BET procedure. Three size fractions of the native clay sample were derived from passage BS #100, #200 and #325 meshes, respectively. Several parameters lhus observed in relation to the pore structures are shown below: 1. The size fraction of BS #100, #200 and #325 show internal pore volumes of 25.3, 30.2 and $35.0m^2g^{-1}$, respectively. 2. In the distribution curves of the cumulative pore volume against pore diameter, it has been shown that the larticle sizes, the steeper the distribution over the larger ranges of pore diameters. The converse is true the smaller particles. 3. Internal pore areas increase with decrease in pore sizes. It follows that the pores having diameters of $\leq$0.1$\mu\textrm{m}$ are responsible for more than 90% of the total pore area. 4. The behaviour of nitrogen adsorption can be best described by BET type IV isotherm. Further, the hysteresis loops of the adsorptiondesorption curves become narrower with decresing particle sizes. 5. The specific surface areas observed for the fractions of BS #100, BS #200 and BS #325 are 34.6, 35.4 and 43.2m $^2g^{-1}$, respectively. and the calcined clay of BS #325 has a specific surface area near $30.4m^2g^{-1}$.

• Journal of the Mineralogical Society of Korea
• /
• v.3 no.1
• /
• pp.44-57
• /
• 1990

Mineralogy of clay(Napseok) deposits in Yangsan area has been studied by the methods of field investigation and laboratory works including the polarizing microscopy, X-ray diffraction, infrared spectroscopy, thermal analysis, chemical analysis by electron micro-probe and atomic absorption spectrophotometer, and electron microscopy(SEM and TEM). The Napseok ores in both the Cheonbulsan and Yongcheon deposits consist mainly of sericite, pyrophyllite and quartz, with more or less tourmaline. The high temperature minerals such as corundum and dumortierite are found in the Cheonbulsan deposit, but not in the Yongcheon deposits. Dickite, nacrite, and halloysite are found in the Yongcheon deposit, but not in the Cheonbulsan deposit. The Napseok ores of the Yukwang deposit consist of sericite posits in the Yangsan area. Occurrence, chemistry and structural features of important minerals are described. Mineralogical data of sericite such as intensity raios and chemistry also support that the Napseok deposits of both the Chenobulsan and Yongcheon mines were formed at the higher temperature than those of the Yukwang mine. Presence of sericite-dickite-pyrophyllite ores in the Yongcheon deposit also suggests the lower temperautre than in the Cheonbulsan deposit.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.30 no.1
• /
• pp.43-51
• /
• 2024

The addition of oxygen scavengers to food products helps to reduce oxygen exposure, thereby mitigating deterioration, including changes in taste, odor, and color, as well as inhibiting microbial growth. Despite the advantages of the existing non-metallic oxygen removal materials in terms of safety for the human body and suitability for use in microwave ovens, their utilization has been limited due to their slow reaction initiation speed. Therefore, in the current study, sodium metabisulfite was impregnated into various porous media, including halloysite nanoclay, activated carbon, montmorillonite, and silica gel. The oxygen scavenger, produced by impregnating silica gel with sodium metabisulfite, demonstrated a 425% improvement in the initial oxygen removal rate compared to pure sodium metabisulfite. Additionally, sachets containing an oxygen-removing composition with an enhanced oxygen removal rate effectively decreased the oxygen concentration to less than 0.5% on the third day of storage in apple packaging, without elevating carbon dioxide levels. Moreover, it proved effective in preventing the browning of the apple surface. Therefore, the SM/SG oxygen-removal composition can be effectively applied to active food packaging by controlling the oxygen concentration within the packaging.

• Journal of the Mineralogical Society of Korea
• /
• v.13 no.1
• /
• pp.1-14
• /
• 2000

알루나이트는 포항지역의 제3기 연일층군의 이암 층내의 탄산염 결핵체 주변에서 할로이사이트와 함께 극미립 변질물 (1-2 $\mu\textrm{m}$)로서 산출된다. 알루나이트는 정육면체와 유사한 능면체 결정형을 이루고 침상 내지 단주상의 할로이사이트와 밀접한 공생관계를 이룬다. X-선회절 분석에 의해서 이 알루나이트는 a=6.9897(1) $\AA$, c=17.2327(4)$\AA$, V=728.75(3) $\AA$3의 격자상수값을 갖는 것으로 밝혀졌다. X-선형광된 이 알루나이트의 화학식은 (K0.94N0.06)(Al2.55Fe3+0.45)(SO4)2(OH)6 으로서, 나트로알루나이트 단성분을 6-7 mole%정도 함유하는 것으로 분석되었다. 또한 시차열분석 (TG-DTG-DTA)을 통해서 알루나이트의 승화성 성분들 (H2O와 SO3)의 존재와 함유 정도를 조사하였고, 고온X-선회절분석을 병행하여 이 광물의 OH기의 이탈 반응 (52$0^{\circ}C$)과 고온상으로의 전이 반응 ($600^{\circ}C$ 및 $700^{\circ}C$)을 감정 하였다. K/Ar 법으로 측정된 알루나이트의 생성 연대 ($0.342\pm$0.008 Ma)와 안정동위원소들의 분석 결과 ($\delta$18Oso4=-1.7, $\delta$DSMOW=-31, $\delta$34S=-10.8)는 이 알루미늄 황산염 광물이 연일충군의 융기 이후에 야기된 민물의 유입에 의한 표성기원의 변질작용의 결과로 생성되었음을 지시한다. 알루나이트+할로이사이트 공생군의 침전은 이암 내에서 조성된 강산성 (pH=2-3)의 알루미늄 황산염 용액이 탄산염 결핵체를 만나 반응하여 pH가 국지적으로 증가되어 (pH=4) 과포화되는 과정에 의해서 야기되었다. 컴퓨터를 이용한 Al3+의 포화지수에 관한 화학적 평형 모델링 실험 결과, 알루미늄 황산염 용액으로부터의 알루나이트와 할로이사이트의 침전은 pH=4 및 \ulcornerSO42-=10-4M 조건에서 K+과 Si(OH)4의 농도가 10-4M 이상 유지되어야 가능한 것으로 밝혀졌다.

• Journal of the Korean Chemical Society
• /
• v.10 no.2
• /
• pp.67-75
• /
• 1966

Four kinds of clays from Sinyewon mine which is located in Chungchoungnam-Do district and two kinds of Japanese clays (Gairome, Kibushi) were selected and studied on the fundamental properties of these clays and those which are refined by the elutriation method. Chemical analysis, grading analysis such as refractoriness, specific gravity, color, fired color and plasticity, particle size distribution, various thermal tests, X-ray diffraction analysis and electron microscopic survey were carried out on these clays. The comparison of domestic clays with Japanese clays was made. 1. In chemical composition and physical properties, these four kinds of Sinyewon clays are almost similar to each other and also to Gairome and Kibushi clays. In refractoriness, Gairome and Kibushi clays have relatively high value such as SK 34 and 35, while Sinyewon clays have the value of about SK 32. Especially Sinyewon clay B has the low refractoriness (SK 18) and plasticity. Refined clays have the tendency of somewhat higher value than crude ones in refractoriness. 2. When burnt up to $900^{\circ}C$, the coefficients of contraction of Sinyewon clays were under 1.5%, Gairome under 1.3%, Kibushi under 3.0%. Only Sinyewon clay B showed expansion (1.0%) instead of contraction. 3. X-ray diffraction analysis and electron micrography showed that all of four Sinyewon clays and two Japanese clays are mainly composed of poorly crystallized kaolin, containing small amount of halloysite, sericite and considerable amount of quartz and feldspar. Sinyewon clay B contains especially large amount of quartz and feldspar. In general, it has been found out that the refined clays were free from large amount of iron oxide, quartz and feldspar.

• Composites Research
• /
• v.30 no.1
• /
• pp.59-64
• /
• 2017

Eco-convivial composites with improved properties are essential to present polymer scenario and can be made easily by replacing partially/completely renewable materials either matrix or reinforcement along with few % of additives. In these investigations, Abaca fabric have been used as reinforcement for manufacturing of Vinyl ester composites through VARTM technique and study the effect of alkali surface treatment of abaca fabric and flame retardant additives i.e., ammonium polyphosphate (APP) with halloysite nano-clay (HNT) on mechanical and flame retardant properties. The results concluded that, surface treatment deceased the hydrophilic nature of fabric and enhanced the interfacial bonding with hydrophobic matrix and eventually increased mechanical properties slightly of developed composites. Similarly, the flame retardancy of the composites improved significantly and increases the burning time by varying the wt% of filler concentration.

• Economic and Environmental Geology
• /
• v.29 no.3
• /
• pp.269-279
• /
• 1996

Dehydroxylation and mullitization of primary and secondary kaolins were investigated in order to compare and understand the differences in thermal behaviours by DTA and TG up to $1,100^{\circ}C$. Chemical analyses and EPMA of the samples revealed nearly ideal unit-cell formulae of kaolins. The weight losses of dickite and halloysite are 14% and 12.5% on the average, respectively. The activation energies of dehydroxylation of kaolin minerals were calculated according to Kissinger's approach which uses various heating rates in DTA to estimate the activation energy of thermal reactions. The activation energies of dehydroxylation of halloysites from Daemoung and Buksam mines are about $163kJmor^{-1}$ (white), $168kJmor^{-1}$ (pink), and $176kJmor^{-1}$ respectively. The activation energies of dickites collected from Sungsan and Ogmae mines are about $166kJmor^{-1}$ and $387kJmor^{-1}$. The asymmetric shape of endothermic peak in DTA, the relative intensities of OH-stretching bands in FTIR spectroscopy and the existence of residual XRD peaks of the samples which were heated at $550^{\circ}C$ for 2 hours indicate that Sungsan dickite may be more disordered than Ogmae dickite. The new phase formed in thermally treated samples in the range of $900^{\circ}C$ to $1,100^{\circ}C$ was identified as mullite by XRD on the basis of disappearing of the characteristic peaks of kaolins and increasing of amorphous background upon heat treatment. On further heating, loss of more water from dehydroxylate resulted in the formation of mullite and the characteristic X-ray diffraction patterns of mullite began to appear at about $900{\sim}1,000^{\circ}C$ in kaolins.

• Journal of the Korean Chemical Society
• /
• v.35 no.4
• /
• pp.422-426
• /
• 1991

In order to synthesize high-purity alpha alumina fine powder, the aluminum hydroxide and ammonium aluminum sulfate(alum) precursor were prepared from natural alumino-silicate(halloysite). The thermal decomposition mechenism for both precursors was elucidated by DTA/TG, XRD and IR analysis. The microstructure, specific surface area and purity of ${\alpha}-Al_2O_3$ were characterized by SEM, and BET analysis. The particle size of ${\alpha}-Al_2O_3$ was determined to be ${\phi}$ = 0.1∼0.5 ${\mu}$m. However, the specific surface area for the alum derived ${\alpha}-Al_2O_3$(89.0 m$^2$/g) was extremely higher than that for the aluminum hydroxide derived one(7.3 m$^2$/g).

• Journal of the Korea Concrete Institute
• /
• v.13 no.2
• /
• pp.123-129
• /
• 2001

Pozzolan is to improve the strength and the durability of concrete as a result of the pozzolanic reaction, Broadly speaking, pozzolanic materials can be artificial materials, such as slica fume and fly ash, and natural material, such as rice husk ash, clay, volcanic ash, clayish pozzolan. Hwangtoh is a mineral which belongs to a group of matakaolin, especially halloysite, and the main elements is SiO$_2$, Al$_2$O$_3$, Fe$_2$O$_3$. The purpose of this study is to examine the application of Hwangtoh for the concrete admixtures, the composition of this study is shown as follows. Chapter I is analysis for properties of concrete as the kinds of admixture, and Chapter H is analysis for properties of concrete as the replacement ratio of activated Hwangtoh. As a result of this study, Hwangtoh is found to have high practical use as pozzolanic material, and the pertinent range of replacement ratios of Hwangtoh on cement are 10∼20 %.