Papers by Keyword: Wollastonite

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Authors: Ourania Menti Goudouri, Eleana Kontonasaki, Nikolaos Kantiranis, Xanthippi Chatzistavrou, Lambrini Papadopoulou, Petros Koidis, Konstantinos M. Paraskevopoulos
Abstract: Melt derived bioactive glass- porcelain system is reported to be bioactive but with a slow rate of bioactivity. The aim of this work is to fabricate and characterize bioactive glass/dental porcelain composites produced by the sol-gel method. Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and X-ray Diffractometry (XRD) were used to characterize the fabricated materials. The FTIR spectra and the XRD patterns confirm the presence of both constituents in the mixtures, while the dominant crystal phases in bioactive glass/dental porcelain specimens are leucite and wollastonite.
Authors: Marko Hyvärinen, Svetlana Butylina, Timo Kärki
Abstract: In general, wood-polymer composites are vulnerable to weathering factors such as UV radiation, moisture, freeze-thaw action. Weathering can cause discoloration, chalking, dimensional change, and loss of mechanical properties of wood-polymer composites. This comparative study was focused on weatherability of wood–polypropylene composites made with and without pigments. Two types of inorganic pigments were applied: carbon black master-batch and synthetic iron oxide. Wood-polypropylene composite made without pigment was used as a reference. Also, composites prepared with addition of wollastonite were tested. The composite samples were exposed to outdoor weathering and in a parallel the accelerated UV weathering was conducted in xenon weathering chamber for the 2000 hours. The colour change was estimated by spectrophotometric method, and the change of Charpy impact strength after weathering was determined. The surface morphology was studied with scanning electron microscopy (SEM). The addition of pigments decreased the lightness of non-weathered composites. The change of lightness and total colour change of weathered composites were affected a lot by type of pigment and method of weathering. As, expected wood-polypropylene composite made with carbon black showed the best results in colour stability of composites exposed to weathering. SEM showed that accelerated weathering in the xenon chamber caused more significant changes in the morphology of the polymer surface layer of the composites than outdoor weathering. Charpy impact strength of all studied composites was found to retain after 2000 hours of outdoor weathering, although accelerated weathering caused significant reduction of Charpy impact strength of these composites.
Authors: Lin Chun Zhang
Abstract: In this paper, we choose heat resistant material wollastonite and corundum to get the concrete which has heat resistance up to 600 centigrade. SEM reveals that at the temperature of 400 centigrade and 600 centigrade, the material is very dense. But when the temperature gets 800 centigrade and 1000 centigrade, the SEM reveals cracks. The refractory concrete made by magnesium potassium phosphate as the binder and wollastonite and corundum as aggregate has short setting time, early strength and rapid hardening. And it is suitable for emergency repair materials for the kiln.
Authors: Xuan Yong Liu, Lian Fu Deng, Chuan Xian Ding
Authors: Ana Maria Minarelli Gaspar, Sybele Saska, R. García Carrodeguas, A.H. De Aza, P. Pena, P.N. De Aza, S. De Aza
Abstract: The biological response following subcutaneous and bone implantation of β-wollastonite(β-W)-doped α-tricalcium phosphate bioceramics in rats was evaluated. Tested materials were: tricalcium phosphate (TCP), consisting of a mixture of α- and β-polymorphs; TCP doped with 5 wt. % of β-W (TCP5W), composed of α-TCP as only crystalline phase; and TCP doped with 15 wt. % of β-W (TCP15), containing crystalline α-TCP and β-W. Cylinders of 2x1 mm were implanted in tibiae and backs of adult male Rattus norvegicus, Holtzman rats. After 7, 30 and 120 days, animals were sacrificed and the tissue blocks containing the implants were excised, fixed and processed for histological examination. TCP, TCP5W and TCP15W implants were biocompatible but neither bioactive nor biodegradable in rat subcutaneous tissue. They were not osteoinductive in connective tissue either. However, in rat bone tissue β-W-doped α-TCP implants (TCP5W and TCP15W) were bioactive, biodegradable and osteoconductive. The rates of biodegradation and new bone formation observed for TCP5W and TCP15W implants in rat bone tissue were greater than for non-doped TCP.
Authors: Hyun Seung Ryu, Jun Hyuk Seo, Hwan Kim, Kug Sun Hong, H.J. Park, Dae Joon Kim, Jae Hyup Lee, D.H. Lee, Bong-Soon Chang, C.K. Lee
Authors: Xuan Yong Liu, Chuan Xian Ding, Paul K. Chu
Abstract: In-vitro evaluation of plasma sprayed wollastonite and dicalcium silicate coatings was carried out by SBF soaking test and osteoblasts seeding test. Apatite layers were formed on the surfaces of the two coatings indicative of the excellent bioactivity. The formation rate of apatite is higher on dicalcium silicate than on wollastonite. The cause is believed to be the presence of orthosilicate species in the dicalcium silicate coating promoting easier leaching by exchanging H3O+ ions from the solution with calcium ions concentrated in the orthosilicate positions. At the same time, loss of soluble silicon occurs, and it is supposed to enhance the repolymerization of the silica gel layer and provide the active sites for the nucleation of apatite. The outcome is that apatite forms faster on dicalcium silicate than on wollastonite. The data obtained from the osteoblasts seeding test indicate that the wollastonite and dicalcium silicate coatings promote the proliferation of osteoblasts and possess excellent biocompatibility.
Authors: Ana Maria Minarelli Gaspar, Sybele Saska, L.R. da Cunha, P.D.A. Bolini, R. García Carrodeguas, A.H. De Aza, P. Pena, P.N. De Aza, S. De Aza
Abstract: Wollastonite bioceramics prepared from synthetic and natural precursors were implanted in rats in bone and subcutaneous tissues. The implant sites were excised after 7, 30 and 120 days, fixed, dehydrated, embedded in paraffin wax for serial cutting and examined under transmitted light microscope. It was found a very similar behavior for both wollastonite bioceramics. They were biocompatible, bioactive and biodegradable when implanted in rat bone. The synthetic ceramic was more reabsorbable than the one from natural powder. When implanted in subcutaneous rat tissue, both materials elicited a mild initial inflammatory reaction that practically disappeared after 120 days. Both materials were encapsulated with a very thin fibrous capsule and slightly reabsorbed at their surfaces. None of the materials induced ectopic osteogenesis. According to the results, the studied materials seem to be able for manufacturing reabsorbable bone implants.
Authors: Hosein Naderpour, Masoomeh Mirrashid
Abstract: Mortar can be defined as a material which is used to hold building blocks that include bricks, stone or concrete together. In this paper, a special type of mortar which is mixed with Wollastonite and also micro-silica is considered and the goal was predicting the compressive strength of mortar in terms of artificial neural networks. For this purpose, the input parameters were assumed to be: the weight of microsilica, wollastonite, ordinary Portland cement, high-range water reducer, and also age of the mortar. Finally based on a sensitivity analysis, the relative importance of input parameters were determined.
Authors: A.F. Gualtieri, E. Mazzucato, C.C. Tang, Robert J. Cernik
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