• Korean Journal of Metals and Materials
• /
• v.50 no.10
• /
• pp.745-751
• /
• 2012

The Kroll process for magnesium reduction of titanium tetrachloride is used for mass production of titanium sponge. The present study was conducted in a lab scale reactor to develop a better understanding of the mechanism of titanium sponge formation in the Kroll reactor with respect to reaction degrees and the feeding rate of $TiCl_4$. The $MgCl_2$ produced during the initial stage of the reaction was not sunk into the molten magnesium, but covered the surface of the molten magnesium. As a result, subsequently fed $TiCl_4$ reacted with Mg exposed on the edge of molten $MgCl_2$ in the crucible. Therefore, titanium sponge grew toward the center of the crucible from the edge. The temperature of the molten magnesium increased remarkably with the increasing feeding rate of $TiCl_4$. Consequently, fed $TiCl_4$ reacted at the upper side of the crucible with evaporated Mg, and produced titanium on the upper surface of the crucible wall, which increased considerably with the feeding rate of $TiCl_4$.

• Resources Recycling
• /
• v.26 no.5
• /
• pp.54-60
• /
• 2017

In this study, we investigated the effect of $TiCl_4$ injection time on the Kroll reaction at a given weight ratio of $TiCl_4$ and Mg. The reduction reaction was investigated by measuring the temperature change according to $TiCl_4$ injection time and observing the cross section and appearance of the Ti sponge after the reaction. The temperature increment due to Kroll reaction heat generation was found to be linearly proportional to the $TiCl_4$ feed rate. In the graph of $TiCl_4$ injection time and reduction tank temperature, initial temperature peaks were observed irrespective of the injection conditions. This is interpreted to mean a temporary interruption of reaction due to $MgCl_2$ formation after the initial Kroll reaction. In addition, when the cross section of the sponge was observed, a large amount of spherical Mg particles was observed in $MgCl_2$. We can infer that this is the process of continuously feeding the unreacted Mg surface, so that a continuous Kroll reaction takes place. The sponge appearance showed that the coalescence or growth of the Kroll reacted Ti particles can be controlled by the cooling rate.

• Membrane Journal
• /
• v.7 no.4
• /
• pp.191-198
• /
• 1997

Membrane formation mechanism by the phase inversion has been investigated in order to control the membrane morphology. It was found that finger-like structures were obtained when the heat of mixing between the solvent and non-solvent is exothermic, while sponge-like structures were obtained when they are endothermic in polystyrenes as well as in polyimides (Torlon and polyimide made frorn 3,3'4,4'-benzophenontetracarboxylic diahmydride and 1,4-phenylene diarnine) membranes. This concept was applied to control the morphology of polysulfone membranes simply by adding a solvent additive by adjusting the heat of mixing. A crude, but simple, relationship between the heat of mixing and the exchange rate of the solvent with non-solvent has been also developed.

• Archives of Plastic Surgery
• /
• v.39 no.4
• /
• pp.317-321
• /
• 2012

Background Many topical hemostatics are widely applied for bleeding control. They can be classified into two categories according to their mechanism of action on the clotting cascade in a biologically active or passive manner. Passive hemostatics include cellulose and gelatin. We performed an experimental study to compare the effect of passive hemostatics in wound healing by applying them to a rectus abdominis muscle defect of white mice. Methods Surgicel is a sterile absorbable knitted fabric prepared by the controlled oxidation of regenerated cellulose. Spongostan is an absorbable hemostatic gelatin sponge. In 30 mice, a $1{\times}1$ cm defect was created on the rectus abdominis muscle and the materials were applied in three ways: control group, cellulose (Surgicel) group, gelatin (Spongostan) group. For the histologic analysis, biopsies were performed at 3 and 28 days. Results After 3 days, the cellulose group showed limited granulation formation with acute inflammatory reactions similar to the control group. At the 28th day, moderate amounts of granulation tissue formation was observed with milder inflammatory reactions than the control group. In the gelatin group, after 3 days, gelatin remnants were observed surrounded by severe inflammatory changes. After 28 days, the same quantity of gelatin remnants could be still observed. Conclusions This study suggests that cellulose is associated with minimal morbidity in wound healing, while the use of gelatin shows severe adverse tissue reactions with delayed wound healing. Consequently, cellulose is better than gelatin when considering wound healing.