• Fibers and Polymers
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• v.3 no.1
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• pp.1-7
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• 2002

Cellulose carbonate was prepared by the reaction of cellulose pulp and $CO_2$ with treatment reagents, such as aqueous $Zncl_2$ (20-40 wt%) solution, acetone or ethyl acetate, at -5-$0^{\circ}C$ and 30-40 bar ($CO_2$) for 2 hr. Among the treatment reagents, ethyl acetate was the most effective. Cellulose carbonate was dissolved in 10% sodium hydroxide solution containing zinc oxide up to 3 wt% at -5-$0^{\circ}C$. Intrinsic viscosities of raw cellulose and cellulose carbonate were measured with an Ubbelohde viscometer using 0.5 M cupriethylenediamine hydroxide (cuen) as a solvent at $20^{\circ}C$ according to ASTM D1795 method. The molecular weight of cellulose was rarely changed by carbonation. Solubility of cellulose carbonate was tested by optical microscopic observation, UV absorbance and viscosity measurement. Phase diagram of cellulose carbonate was obtained by combining the results of solubility evaluation. Maximum concentration of cellulose carbonate for soluble zone was increased with increasing zinc oxide content. Cellulose carbonate solution in good soluble zone was transparent and showed the lowest absorbance and the highest viscosity. The cellulose carbonate and its solution were stable in refrigerator (-$5^{\circ}C$ and atmospheric pressure).

• Journal of the Korean Ceramic Society
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• v.52 no.6
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• pp.467-472
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• 2015

The effect of $SrCO_3$ content on the microstructure, porosity, flexural strength, and pore size distribution of clay-based membrane supports was investigated. Green compacts prepared from low cost materials such as kaolin, bentonite, talc, sodium borate, and strontium carbonate were sintered at $1000^{\circ}C$ for 8 h in air. It was possible to control the porosity of the clay-based membrane supports within the range of 33% to 37% by adjusting the $SrCO_3$ content. The flexural strength of the clay-based membrane supports was found to strongly depend on their porosity. In turn, the porosity was affected by the $SrCO_3$ content. The average pore size and flexural strength of the clay-based membrane supports containing 4 wt% $SrCO_3$ were $0.62{\mu}m$ and 33 MPa at 34% porosity.

• Korean Journal of Materials Research
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• v.26 no.7
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• pp.359-362
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• 2016

Mineral filler is used for resin compounds, because it increases the stiffness and thermal stability of a resin compound, and it also cuts down the cost. Calcium carbonate, silica, magnesium oxide, and others are used as filler materials in general, and the type of filler material, the size, and content can affect the physical properties of compounds. Those factors also influence the viscosity of resin mixtures and the workability, and should be adjusted by changing the contents of the filler, which depends on the size. In this study, five kinds of ground calcium carbonate, which were different in size, were used to produce polyester compounds ; the physical properties were compared with the filler size and contents. The mechanical properties were measured by bending strength and tensile strength, and the heat deflection temperature was obtained for thermal stability.

• Journal of the Korean Applied Science and Technology
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• v.10 no.1
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• pp.49-55
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• 1993

Ground Calcium Carbonate, among paper coating pigments, will influence less dispersant demand, less binder demand, increase coating solids from 58% to 70%, which means high speed coating, less shrinkage during drying, less energy consumption, more uniform coverage of fibers. The quality point of view of Ground Calcium Carbonate, brightness, particle size, Particle size distribution, hardness, impurities content are important. More important factors of Ground Calcium Carbonate which influence the paper coating process are dispersion mechanisms and their effects. The study was made to investigate the effect of Ground Calcium Carbonate dispersion by sodium salt of polyacrylate dispersant composition and dispersion condition. Basic tests such as physical, optical and chemical were perfumed, and dispersion effects were investigated by different conditions. The results showed that the type of dispersant affected the dispersion effects, and the Ground Calcium Carbonate has critical dispersant demand.

• The Journal of Natural Sciences
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• v.4
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• pp.95-102
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• 1991

The influences of various concentrations of thallium carbonate on the hydration of tricalcium silicate which is widely used to the inorganic materials have been studied using an isothermal microcalorime-ter. The experimental results indicate that the hydration of tricalcium silicate is accelerated in the presence of thallium carbonate, namely the concentration of thallium carbonate is increased, the rate of hydration is also increased. The x-ray diffraction analysis shows that the concentration of tricalcium silicate decreases rapidly in the presence of thallium carbonate. Differential thermal analysis of tricalcium silicate hydrated in the persence of thallium carbonate indicates the presence of calcium carbonate. The nonevaporable water content and the degree of hydration of tricalcium silicate show that the accelerating action of thallium carbonate is more pronounced only during the early period of hydration. Analytical results of the liquid phase in contact with the tricalcium silicate paste indicate that the concentrations of calcium and hydroxyl ions are changed considerably in the presence of thallium carbonate.

• Ocean and Polar Research
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• v.30 no.3
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• pp.215-224
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• 2008

A piston core (MR06-04 PC23A) collected from the northern continental slope in the central Bering Sea has recorded the high-resolution millennial-scale variation of calcium carbonate ($CaCO3$) content during the last 65 kyr. An estimation of the age of the core sediments was carried out by using the lithologic correlation of the deglacial laminated layers with a neighboring core (HLY02023JPC), complementing the last appearance datum of both Lychnocanoma nipponica sakaii (54 kyr) and Amphimelissa setosa (85 kyr). The probable age of core MR06-04 PC23A was approximately younger than 65 kyr. Two distinct events of a significant increase of $CaCO3$ in the deglacial laminated sediments clearly correspond to MWP1A and MWP1B in the Bering Sea (Gorbarenko et al. 2005) and to T1ANP and T1BNP in the North Pacific (Gorbarenko 1996). These pronounced peaks of $CaCO3$ contents result from the elevated carbonate production in the surface water and the subsequent weakened dilution due to terrestrial input, along with an enhanced oxygen minimum zone. The $CaCO3$ contents are low (${\sim}2%$) during the last glacial period mainly because of a low carbonate production caused by an expanded sea-ice cover and an increased dilution by terrigenous particles due to their closer distance to the continent during the sea-level low stand. The occurrence of seven distinct $CaCO3$ peaks in core MR06-04 PC23A is remarkable during MIS 3 and MIS 4, and they most likely correlate to the short-term millennial Dansgaard-Oeschger events.

• Korean Chemical Engineering Research
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• v.55 no.1
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• pp.1-6
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• 2017

More addition of calcium carbonate in printing paper allows savings of the wood fibers and the drying energy. Pre-flocculation of GCC (ground calcium carbonate) using functional polymers was known as the best available technology to make high loaded paper until now, and it allowed less reduction of the paper essential properties such as tensile strength and smoothness at higher GCC content. However, pre-flocculated GCC became unstable in size under the continued agitation in the mill. Therefore, pre-flocculation method was modified in such a way that the in-situ calcium carbonate was formed between the GCC particles of the pre-flocculated GCC, and the resultant became more stable in size, which we named as HCC (hybrid calcium carbonate). HCC turned out to make high tensile strength and smoothness as much as the pre-flocculated GCC and gave much better size stability against stirring. Furthermore, HCC gave high bulk that pre-flocculation could not make.

• Geomechanics and Engineering
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• v.17 no.5
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• pp.465-473
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• 2019

Biocementation due to the microbially induced calcium carbonate precipitation (MICP) process is a potential technique that can be used for soil improvement. However, the effect of biocementation may be affected by many factors, including nutrient concentration, bacterial strains, injection strategy, temperature, pH, and soil type. This study investigates mainly the effect of chemical concentration on the formation of calcium carbonate (e.g., quantity, size, and crystalline structure) and unconfined compressive strength (UCS) using different treatment time and chemical concentration in the biotreatment. Two chemical concentrations (0.5 and 1.0 M) and three different treatment times (2, 4, and 8 cycles) were studied. The effect of chemical concentrations on the treatment was also examined by making the total amount of chemicals injected to be the same, but using different times of treatment and chemical concentrations (8 cycles for 0.50 M and 4 cycles for 1.00 M). The UCS and CCC were measured and scanning electron microscopy (SEM) analysis was carried out. The SEM images revealed that the sizes of calcium carbonate crystals increased with an increase in chemical concentrations. The UCS values resulting from the treatments using low concentration were slightly greater than those from the treatments using high concentration, given the CCC to be more or less the same. This trend can be attributed to the size of the precipitated crystals, in which the cementation efficiency increases as the crystal size decreases, for a given CCC. Furthermore, in the high concentration treatment, two mineral types of calcium carbonate were precipitated, namely, calcite and amorphous calcium carbonate (ACC). As the crystal shape and morphology of ACC differ from those of calcite, the bonding provided by ACC can be weaker than that provided by calcite. As a result, the conditions of calcium carbonate were affected by test key factors and eventually, contributed to the UCS values.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.118-126
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• 2021

The experiments to produce the vaterite type calcium carbonate were conducted for using the waste oyster shell as the recycling resources. Firstly, the oyster shell were calcinated at 800 ℃ for 24 h. Calcinated oyster shell were reacted with the nitric acid solution, and were diluted to 0.1 M Ca(NO3)2 solution. This solution was mixed with 0.1 M Na2CO3 contained 0.1 mol lysine/1 mol CaO at 20 ℃ and 600 rpm mixing condition for 1 h. The reaction products were identified to vaterite type calcium carbonate (84.5% vaterite, 15.5% calcite) by XRD and SEM analysis. Mean particle diameter was 6.87 ㎛, and the lysine content in calcium carbonate was analyzed to 0.1%.

• Geomechanics and Engineering
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• v.29 no.1
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• pp.79-90
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• 2022

Soybean-urease induced carbonate precipitation (EICP), as an alternative to microbially induced carbonate precipitation (MICP), was employed for soil improvement. Meanwhile, soluble calcium produced from industrial waste carbide slag powder (CSP) via the acid dissolution method was used for the EICP process. The ratio of CSP to the acetic acid solution was optimized to obtain a desirable calcium concentration with an appropriate pH. The calcium solution was then used for the sand columns test, and the engineering properties of the EICP-treated sand, including unconfined compressive strength, permeability, and calcium carbonate content, were evaluated. Results showed that the properties of the biocemented sand using the CSP derived calcium solution were comparable to those using the reagent grade CaCl₂. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses revealed that spherical vaterite crystals were mainly formed when the CSP-derived calcium solution was used. In contrast, spherical calcite crystals were primarily formed as the reagent grade CaCl₂ was used. This study highlighted that it was effective and sustainable to use soluble calcium produced from CSP for the EICP process.