Supercritical CO2 for the Reactive Precipitation of Calcium Carbonate: Uses and Applications to Industrial Processing

2015 ◽  
pp. 251-290 ◽  
Keyword(s):  
Calcium Carbonate ◽  
Supercritical Co2 ◽  
Industrial Processing

A TEM study of the microstructure of avian eggshells

1992 ◽  
Vol 50 (2) ◽  
pp. 1102-1103
Author(s):  
S. Q. Xiao ◽  
S. Baden ◽  
A. H. Heuer
Keyword(s):  
Electron Microscope ◽  
Calcium Carbonate ◽  
Nucleation And Growth ◽  
Growth Mechanisms ◽  
Shell Surface ◽  
Thin Sections ◽  
Polycrystalline Metals ◽  
Transmission Electron ◽  
Nucleation And Growth Mechanisms

The avian eggshell is one of the most rapidly mineralizing biological systems known. In situ, 5g of calcium carbonate are crystallized in less than 20 hrs to fabricate the shell. Although there have been much work about the formation of eggshells, controversy about the nucleation and growth mechanisms of the calcite crystals, and their texture in the eggshell, still remain unclear. In this report the microstructure and microchemistry of avian eggshells have been analyzed using transmission electron microscope (TEM) and energy dispersive spectroscopy (EDS).Fresh white and dry brown eggshells were broken and fixed in Karnosky's fixative (kaltitanden) for 2 hrs, then rinsed in distilled H2O. Small speckles of the eggshells were embedded in Spurr medium and thin sections were made ultramicrotome.The crystalline part of eggshells are composed of many small plate-like calcite grains, whose plate normals are approximately parallel to the shell surface. The sizes of the grains are about 0.3×0.3×1 μm3 (Fig.l). These grains are not as closely packed as man-made polycrystalline metals and ceramics, and small gaps between adjacent grains are visible indicating the absence of conventional grain boundaries.

Anti-diabetic properties of non-polar Toona sinensis Roem extract prepared by supercritical-CO2 fluid

Planta Medica ◽  
2012 ◽  
Vol 78 (11) ◽  
Author(s):  
YH Tsai ◽  
TJ Hsieh ◽  
MC Liao ◽  
PJ Lien ◽  
CC Sun ◽  
...  
Keyword(s):  
Supercritical Co2 ◽  
Toona Sinensis ◽  
Supercritical Co2 Fluid

Scaling risk assessment in a closed circuit recycled board mill by speciation methods

TAPPI Journal ◽  
2012 ◽  
Vol 11 (5) ◽  
pp. 53-61 ◽  
Author(s):  
PATRICK HUBER ◽  
SYLVIE NIVELON ◽  
PATRICE NORTIER
Keyword(s):  
Calcium Carbonate ◽  
Volatile Fatty Acids ◽  
Inorganic Carbon ◽  
Stability Index ◽  
Closed Circuit ◽  
Critical Problem ◽  
Local Scaling ◽  
Water Analyses ◽  
Closed Water ◽  
Speciation Calculation

Calcium carbonate scaling often is a critical problem for recycled board mills that have closed water circuits. The objective of this study was to determine local scaling risks throughout the production process. To predict scaling potential, we calculated several saturation indexes, based on speciation determined from detailed water analyses. Calculated scaling trends are in accordance with observed dissolution and precipitation of calcium carbonate in the process, when considering local aeration phenomena. The importance of volatile fatty acids (resulting from anaerobic bacterial activity) in calco-carbonic equilibriums is discussed, and taken into account in the speciation calculation. We also demonstrate the need to measure inorganic carbon instead of alkalinity in such conditions. This makes typical scaling indexes, such as the Ryznar Stability Index, irrelevant to predict scaling risk in closed circuit conditions; thus, it is necessary to use general speciation methods, as described in this paper.

A method for measuring the in-plane compressive strength and the compression behavior of coating layers

TAPPI Journal ◽  
2011 ◽  
Vol 10 (7) ◽  
pp. 29-34
Author(s):  
TEEMU PUHAKKA ◽  
ISKO KAJANTO ◽  
NINA PYKÄLÄINEN
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Calcium Carbonate ◽  
Coating Layer ◽  
Test Methods ◽  
Coating Films ◽  
Precipitated Calcium Carbonate ◽  
Coating Color ◽  
Mineral Coatings ◽  
Styrene Butadiene

Cracking at the fold is a quality defect sometimes observed in coated paper and board. Although tensile and compressive stresses occur during folding, test methods to measure the compressive strength of a coating have not been available. Our objective was to develop a method to measure the compressive strength of a coating layer and to investigate how different mineral coatings behave under compression. We used the short-span compressive strength test (SCT) to measure the in-plane compressive strength of a free coating layer. Unsupported free coating films were prepared for the measurements. Results indicate that the SCT method was suitable for measuring the in-plane compressive strength of a coating layer. Coating color formulations containing different kaolin and calcium carbonate minerals were used to study the effect of pigment particles’ shape on the compressive and tensile strengths of coatings. Latices having two different glass transition temperatures were used. Results showed that pigment particle shape influenced the strength of a coating layer. Platy clay gave better strength than spherical or needle-shaped carbonate pigments. Compressive and tensile strength decreased as a function of the amount of calcium carbonate in the coating color, particularly with precipitated calcium carbonate. We also assessed the influence of styrene-butadiene binder on the compressive strength of the coating layer, which increased with the binder level. The compressive strength of the coating layer was about three times the tensile strength.

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