Papers by Keyword: Calcium Sulphate

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Authors: Yu Long Wang, Huai Yu Zhan, Yan Xin Liu, Fei Fei Liu
Abstract: Calcium sulphate is rich in natural resources and by-product of many industrial processes. However, most calcium sulphate product was only used with low added value or treated as waste, harmful to environment. If the calcium sulphate can be used as papermaking filler, very high added value can be gained and also the environment problem can be solved. In this paper calcium sulphate from by product of industry was characterized by X-ray diffractometer (XRD) and scanning electron micrograph (SEM), and then used as papermaking filler. The influence of calcium sulphate filler on pulp suspension and paper properties was studies. The results showed that the calcium sulphate fillers were composed of three crystal forms, dihydrate, hemihydrate, anhydrite, and it was needle or fiber shape, hollow in the middle; calcium sulphate showed high brightness and high conductivity in water, compared with talc or ground calcium carbonate(GCC) filler. When calcium sulphate filler was used in papermaking process the filler retention was very small because of its high solubility in water. Calcination at high temperature can lower the solubility of calcium sulphate and slightly increase the retention, but the retention was still quite small. The future work should focus on controlling the solubility of calcium sulphate.
Authors: Jorge Sanjurjo-Sánchez, Juan Ramón Vidal Romaní, Carlos Alves
Abstract: Lime mortars have been commonly used in historical buildings since ancient times. The progressive deterioration of these mortars by air pollution and other environmental causes hinders the assessment of the original composition. The weakening of the mortar structure is due to dissolution and formation of calcium sulphate layers because of the interaction with SOx gaseous pollutants. Also, pollution particles can be incorporated to the mortar because of dissolution by rainwater or runoff. Scanning Electron Microscopy (SEM) studies allow us to distinguish allochthonous and autochthonous micro- and nanoparticles in order to identify original intact plasters. By comparing these intact to deteriorated mortars from both air polluted and non-polluted areas it is possible to indentify and preserve the original mortar composition as a key step to project future façade cleaning and restorations.
Authors: K.J. Lilley, Adrian J. Wright, David Farrar, J.E. Barralet
Abstract: Brushite cement is more soluble than apatite cement in physiological conditions and therefore may be more resorbable in vivo. Brushite cement has been formed previously by mixing β-tricalcium phosphate, water and an acidic source of phosphate ions. However, brushite cement may be formed by the mixture of H3PO4 solution and poorly crystalline precipitated hydroxyapatite (HA). Several additives have been used to alter the physicochemical properties of brushite cement. In this study sulphate ions where added to the cement system by addition of ammonium sulphate to HA during HA preperation. Sulphate ions were found to alter the structure, composition and mechanical performance of cement.
Authors: Ishikawa Kunio, Shigeki Matsuya, Yumiko Suzuki, Koh-ichi Udoh, Masaharu Nakagawa, Kiyoshi Koyano
Abstract: Present study evaluated the feasibility of apatite monolith preparation from calcium sulfate monolith using ammonium phosphate solution. We found that calcium phosphate monolith transforms to apatitic monolith without changing its original morphology when a proper temperature and a proper phosphate solution was selected. Prepared apatite was B-type carbonate apatite with low crystallinity. Although mechanical strength of the apatite monolith was lower than original calcium sulphate monolith, we concluded present method may be useful for the fabrication of apatite monolith since we can prepare different shape of apatite monoliths based on the setting reaction of calcium sulphate and compositional transformation to apatitic mineral.
Authors: Jian Sheng Wang, K.E. Tanner, Saba Abdulghani, Lars Lidgren
Abstract: Injectable bone substitutes (IBS) based on calcium phosphate (CaP) and/or calcium sulphate (CaS) are used as fillers in bone defects to stimulate bone integration and allow mechanical loading. Two types of IBS, IBS-1 is CaP+20%CaS and IBS-2 is CaS+40% hydroxyapatite, were investigated. The materials were injected into holes in the femur and tibia in rabbits. After 10 weeks the femora were subjected to indentation testing and tibiae were prepared for histology evaluation. IBS-1 lead to an higher indentation load compared to control, that is no material inserted, while IBS-2 showed no significant difference between material and control. Histology showed that with IBS-1, the bone penetrated into and integrated with the material in the defect. With IBS-2, new bone grew into the outer 0.5-1.0 mm. The materials could be used for different indications, such as to support fracture healing or in contained cavities.
Authors: C.P. Cleere, G.M. Insley, M.E. Murphy, P.N. Maher, A.M. Murphy
Authors: M. Nilsson, E. Fernández, S. Sarda, Lars Lidgren, Josep A. Planell
Authors: M. Dimanchev, A. Shofan, Troyo D. Troev, J. Serna
Authors: M. Nilsson, E. Fernández, Josep A. Planell, Ivana McCarthy, Lars Lidgren
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