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CBS (CaO–B 2 O 3 –SiO 2 ) glass/cordierite (Mg 2 Al 4 Si 5 O 18 ) ceramic composites were prepared using standard ceramic process. Effects of cordierite on crystallization behavior of the CBS glass powder were investigated. Results showed that crystalline phases like pseudowollastonite (CaSiO 3 ) and quartz (SiO 2 ) were formed during the firing of glass alone. For the composites with ≥45 vol. % cordierite at 780–1200 °C, the above crystalline phases were completely prevented but new phase of anorthite (CaAl 2 Si 2 O 8 ) was formed. For all the composites, the intensity of peaks characterizing cordierite gradually decreases and that of characterizing anorthite synchronously enhances with increasing sintering temperature. Microstructural changes of all the samples with sintering temperature were in good agreement with the relative density and an optimum firing temperature for maximum densification existed for each glass/ceramic ratio. The thermal expansion coefficient (TEC) of the composites decreases with increase in cordierite ceramic volume percent. The TEC of all the composites was in the range of 2.2 × 10 −6 K −1 to 5.2 × 10 −6 K −1 . The dielectric constant of the fabricated composites was between 5.2 and 6.2. The precipitation of anorthite has no bad effect on the dielectric constant and the TEC of the resulting composites because anorthite has low dielectric constant (6.2) and low thermal expansion coefficient (4.82 × 10 −6 K −1 ). The prepared glass/ceramic composites were well suited for LTCC application. more...

A dated (1773) openwork basket labelled “PHILADELFIA” attributed to the Bonnin and Morris factory has a lead-bearing, silicious–aluminous–calcic (S-A-C) composition that contrasts with the phosphatic (bone ash) porcelains known to have previously been made during the mid-1760s to early 1770s in what is now the United States. The basket was underfired and so contains relics of a flint (Pb) glass flux, but kiln temperatures were nonetheless sufficient for subsolidus pseudowollastonite and anorthite to have been resorbed, implying that the duration of firing (soaking) near peak kiln temperatures was insufficient to ensure thorough vitrification. During cooling, liquidus pseudowollastonite and silica polymorphs (but not anorthite) formed, showing that the melt was confined to the tridymite–pseudowollastonite cotectic above the Trd–Wol–An eutectic (1170 °C) in the SiO 2 –Al 2 O 3 –CaO system. Rapid cooling is also indicated by quenched silica polymorphs in the relict glass particles. Although Bonnin and Morris employed some former Bow (London, c. 1743–74) workers, the S-A-C wares initially produced by this factory are compositionally distinct from the 1773 basket, which in this regard more closely resembles the body and glaze of a reputed Chelsea triangle-period (London, c. 1745–49) vessel. Regardless of how they obtained this technology, it is ironic that Bonnin and Morris chose to abandon phosphatic pastes in favour of what in Britain had become an obsolete formula. more...

Hybrid sono-aerogels in the CaO−SiO2−poly(dimethyl siloxane) (PDMS) system with low density and high surface area and pore volume were investigated to be used as biomaterials. Their in vitro bioactivity was monitored by soaking in a simulated body fluid (SBF). All the aerogels exhibited similar wetting and dissolution properties, but only the aerogel of composition 20 wt % PDMS−20 wt % CaO (S20Ca20) exhibited a bioactive response in SBF. To investigate the relationship between the different in vitro behaviours and the hybrids nanostructure, samples were studied by high-resolution transmission electron microscopy (HRTEM). All the aerogels showed similar basic microstructural features exhibiting amorphous Ca-free areas characterized by Si−O−Si distances of 0.23 nm. However, crystallized nanodomains containing calcium were also detected in S20Ca20. These domains, identified as pseudowollastonite and other Ca−Si−O phases, could explain the bioactive response of this material. Bioactivity and good textural and... more...

This document describes and discusses the non-isothermal devitrification process of the wollastonite-tricalcium phosphate (W-TCP) eutectic glass. This eutectic glass has been studied in situ, from room temperature up to 1375 °C, by Neutron Diffractometry (ND) in vacuum. The data obtained were complemented and compared with those performed on ambient atmosphere by Differential Thermal Analysis (DTA) and with those of samples fired in air, at selected temperatures, and then cooled down and subsequently studied by laboratory X-ray Powder Diffraction (LXRD) and Field Emission Scanning Electron Microscopy (FE-SEM) fitted with Energy X-Ray Dispersive Spectroscopy (EDS). Selected samples have been investigated by quantitative full-phase analysis (including the amorphous content) using the Rietveld method. The experimental evidence indicates that the devitrification of W-TCP eutectic glass, begins at ~870°C, with the crystallization of a Ca-deficient apatite phase (Ca9.92(P5.85O23.54)(OH)2.03 (H2O)2.194) followed by wollastonite-2M (-CaSiO3) crystallization at 1006°C. At 1375°C the bio glassceramic is comprised of quasi-rounded colonies formed by a homogeneous mixture of pseudowollastonite (-CaSiO3) and -tricalcium phosphate (-Ca3(PO4)2). This microstructure corresponds to irregular eutectic structures and is similar to that of Bioeutectic® W-TCP material obtained previously, via controlled slow solidification of the eutectic composition, by some of the present authors. It has also been found that from the eutectic composition of the wollastonite – tricalcium phosphate binary system is possible to obtain a wide range of bio glass-ceramics through appropriate design of thermal treatments. more...

Thermal treatment of bioactive glasses can affect their microstructure and thus their bioactivity. The aim of this study was the characterization of the thermally treated sol-gel-derived bioactive glass 58S at characteristic temperatures and the dependence of its bioactive behavior on the specific thermal treatment. The thermal behavior of the bioactive glass was studied by thermal analysis (TG/DTA). Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffractometry (XRD) were used for the characterization of the bioactive glass. The bioactive behavior in Simulated Body Fluid (SBF) was examined by Scanning Electron Microscopy (SEM-EDS) and FTIR. The major crystal phases after thermal treatment were Calcium Silicates, Wollastonite and Pseudowollastonite, while all thermally treated samples developed apatite after 48 hours in SBF. A slight enhancement of bioactivity was observed for the samples heated at the temperature range 910-970oC. more...

The specific features of the separate crystallization of pseudowollastonite (the α phase) and β-wollastonite from an X-ray amorphous iron-free aluminosilicate melt are considered in respect to different methods used for cooling of the melt. It is shown that the phase transition from the amorphous state to the crystalline state is accompanied by the propagation of the heat wave front. more...

This work describes the evaluation of a glass ceramic (55S41C4P-1300) as a potential substrate for bone tissue engineering. For that purpose, the capacity of mesenchymal stem cells (MSCs), isolated from rabbit bone marrow, to adhere, proliferate and differentiate into osteoblast (OBs) with or without 55S41C4P-1300 was investigated. Two types of culture medium, i.e. growth medium (GM) and osteogenic medium (OM), were evaluated. The bioactive 55S41C4P-1300, containing pseudowollastonite, wollastonite, tricalcium phosphate and crystoballite as crystalline phases, was obtained by heat treatment of a sol-gel glass (55SiO(2), 41CaO, 4P(2)O(5) (mol.%)) at 1300 degrees C. The results showed that the MSCs adhered, spread, proliferated and produced mineralized extracellular matrix on 55S41C4P-1300 regardless of the culture medium used. As the same time, they showed an osteoblastic phenotype, and this phenomenon was accompanied by the gradual diminution of the marker CD90 expression. The 55S41C4P-1300 was able to induce the differentiation of MSCs into OBs in the same way as OM without glass ceramic. This effect increased with the combination of 55S41C4P-1300 with OM. The glass ceramic evaluated in this work is bioactive, cytocompatible and capable of promoting the differentiation of MSCs into OBs. For that reason, it could be regarded as a suitable matrix in tissue engineering for bone tissue regeneration. more...

In the present work bioactive powders of the ternary SiO 2 ·CaO·P 2 O 5 systems, which differ in the Ca/P molar ratio, were synthesized by means of a sol–gel route, using tetraethyl orthosilicate (TEOS, Si(OC 2 H 5 ) 4 ), calcium nitrate tetrahydrate (Ca(NO 3 ) 2 ·4H 2 O) and triethyl phosphate (TEP, OP(OC 2 H 5 ) 3 ) as precursors of SiO 2 , CaO and P 2 O 5 , respectively. In order to investigate the influence of the relative amount of each phase (in this study: SiO 2 , CaO and P 2 O 5 ) the thermal properties of the synthesized gel-glass materials were studied as a function of the Ca/P molar ratio using thermogravimetric and differential thermal analysis (TG/DTA). After dehydration (in a single step), described from a kinetic point of view as a simple water evaporation without rupture of chemical bonds, all gels undergo a complex multi-step decomposition with endo and exothermic effects, followed by crystallization of calcium silicate phases at about 950 °C. Furthermore, Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning Electron Microscopy, coupled with energy dispersive spectroscopy (SEM/EDS), allowed us to detect the chemical modifications induced by modifying the Ca/P molar ratio and the sintering. This process is obtained by thermal treatment of the gel-glass precursors after analyzing their thermal behavior in the temperature range 600–1000 °C, with the aim to convert them into ceramic powders, suitable for their applications. The results revealed that when temperature is up to 900 °C, crystallization occurs and pseudowollastonite and wollastonite were formed. Finally, the amount of pseudowollastonite decreased with increasing the sintering temperature, while that of wollastonite increased. more...

Wollastonite-based ceramic (CaSiO 3) is found to be bioactive and therefore could be considered as hard tissue replacement material. Generally, wollastonite-based ceramic could be produced either by melting of suitable raw chemicals followed by controlled crystallization of the glasses or by sol-gel method. The main drawbacks of melting method are multistep preparation procedure (melting, grinding, forming and sintering) and relatively high processing temperatures (about 1500 o C). The solgel method offers lower processing temperatures (they do not exceed 1200 o C), however is expensive and has low efficiency. New and very promising way that could be applied for obtaining of wollastonitecontaining ceramic is controlled heat treatment of silicon-containing polymeric precursor with suitable ceramic active fillers. Heat treatment of such mixtures, depending from the type of polymer precursor, type of active fillers and final heat treatment temperature, leads to formation of wollastonite-containing ceramic material already at about 1000 o C [1, 2]. This is a relatively inexpensive and efficient method and enables to obtain complex shapes. The aim of this work was to obtain wollastonite-based materials and to determine their bioactive features. The materials were obtained by thermal treatment of ceramic active fillers-containing polysiloxane polymeric precursor. As active fillers, commercially available Ca(OH) 2 and silica nanopowders were used. The phase composition of ceramic products were analysed by the means of Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD). The microstructure ceramic products were studied by scanning electron microscopy (SEM) with EDS point analysis. The bioactivity was determined in “in vitro” conditions, by immersing of ceramic samples in simulated body fluid (SBF). The results presented in this work indicate that heat treatment of active fillerscontaining polysiloxane precursor is alternative method for receiving of wollastonitecontaining materials. Such obtained samples demonstrate bioactivity in “in vitro” conditions. more...

The manufacturing of a composite made of a synthetic bioactive ceramic, pseudowollastonite (psW), and a bioresorbable copolymer ethylmethacrylate–vinylpyrrolidone (EMA/VP) is presented in this article. psW porous blocks were produced by dipping an open porous polyurethane foam in a psW containing slurry. A 40/60 wt % EMA/VP monomers mixture was poured on the blocks, and free radical polymerization initiated by azobis(isobutyronitrile) at 50°C. Disks of 1 mm height were obtained by cutting the composite with a diamond saw, and bioresorption and bioactivity of the specimens were tested by immersion of the disks into SBF. A ceramic/polymer weight ratio of 72/28, greater than the usually achievable ratio by polymeric solidification of slurries of monomers charged with a powdered solid component, has been obtained. The system is bioactive and does not change the pH of the medium during the degradation test. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res 80A:, 2007 more...

In a previous study, a new ceramic material (Bioeutectic ® ), prepared by slow solidification through the eutectic temperature-composition region of the wollastonite-tricalcium phosphate system, was found to be bioactive in static-simulated body fluid. The eutectic material reacts by dissolving the pseudowollastonite phase and forming a hydroxyapatite-like porous structure by a pseudomorphic transformation of the tricalcium phosphate lamellae, which in turn mimics porous bone. Later, a hydroxyapatite-like layer is formed by precipitation on the surface of the material. In the present study, the bioactivity of the Bioeutectic® material was assessed in dynamic simulated body fluid in order to improve the ingrowth of new bone into implants (osteointegration). Samples of the material were soaked for 2 weeks in a dynamic simulated body fluid (1 mL/min) at 37°C. The experiment showed that there is no precipitation of hydroxyapatite-like layer on the surface of a the material. Otherwise, a complete transformation of the eutectic material takes place, giving rise to a hydroxyapatite artificial porous bone. The dynamic model used in this study may be better than the usual static immersion model in imitating the physiological condition of bone-like apatite formation. more...

Raw glazes are well suited for glazes fired traditionally at high top temperatures. Final phase composition of these glazes is assumed to be controlled by nucleation and growth of crystals in the melt. At shorter firing cycles the phase composition of glazes is likely to be restricted by the limited reaction time. In this work the influence of firing cycle and glaze composition on final glaze phase composition was studied. Fifteen experimental raw glazes were fired at short, intermediate and long cycles. Crystalline phases developed in the surfaces were identified with X-ray diffraction and SEM/EDXA. Sintering behaviour of the glazes was studied with hot stage microscopy. Compositional dependence for two typical temperatures from sintering curves was established. The results indicate that the phase composition strongly depends on the firing cycle. Crystalline phases in fast-fired glazes were intermediate products of first raw material reactions, diopside, wollastonite and pseudowollastonite. Traditional firing favours feldspar formation. more...

Glass and glass-ceramic coatings on ceramic tiles have been manufactured by plasma-spraying high-performance CAS (in wt%—SiO 2 , 60%; Al 2 O 3 , 15%; CaO, 23%; others, traces) and CZS (in wt%—SiO 2 , 50%; CaO, 31%; ZrO 2 , 16.5%; Al 2 O 3 , 2%; others, traces) glass frits. The CZS system has a surface crystallization at about 1050 °C. Such behaviour would not easily allow to obtain a fully crystalline bulk glass-ceramic, but the defectiveness of the plasma-sprayed coating supplies many nucleation sites. Thus, it becomes completely crystalline and well sintered after a 850 °C for 30 min + 1050 °C for 15 min treatment. The CAS frit, designed not to produce significant crystallization, is well sintered after a 850 °C for 30 min + 950 °C for 30 min thermal treatment, but remains too brittle due to its glassy nature. A 1050 °C treatment allows a few pseudowollastonite crystals to form in a glassy matrix; their formation also hinders sintering. Thus, mechanical properties are inferior to heat-treated plasma-sprayed CZS. more...

Pseudowollastonite ceramics (beta-CaSiO3) from synthetic and natural sources were assessed with regard to their properties relevant to biomedical applications. Synthetic and natural CaSiO3 powders, with average particle size of 1.6 and 13.2 microm, respectively, were first employed. Powders were pressed and sintered at 1400 degrees C for 2 h. Pseudowollastonite was the only crystalline phase in sintered materials. Glassy phase, eight times more abundant in sintered natural wollastonite (SNW) than in the synthetic one (SSW), was observed in grain boundaries and in triple points. Larger grains and bigger and more abundant pores were present in SNW, resulting in lower diametral tensile strength (26 MPa), than in SSW (42 MPa). However, by milling the natural wollastonite starting powder to a particle size of 2.0 microm and sintering (SNW-M), the microstructure became finer and less porous, and diametral tensile strength increased (48 MPa). Weibull modulus of SNW and SNW-M samples was twice that of the SSW. All the samples released Si and Ca ions, and removed phosphate ions from simulated body fluid in similar amounts and were completely coated by apatite-like spherules after soaking in simulated body fluid for 3 wk. The aqueous extracts from all samples studied were not cytotoxic in a culture of human fibroblastic cells. No differences in fibroblast-like human cells adhesion and proliferation were observed between samples. According to the obtained results, properly processed pseudowollastonite bioceramics, obtained from the natural source, exhibit the same in vitro behavior and better performance in terms of strength and reliability than do the more expensive synthetic materials. more...

Single crystals of the SrGeO3 high-pressure phase are prepared by hot pressing of the polycrystalline pseudowollastonite SrGeO3 (BN anvil press, 6 GPa, 1223 K, 1 h).

Cobalt alloy samples were bioactivated during investment casting. The cavities of the investment mold were previously coated with wollastonite. Additionally, be- fore coating with wollastonite, some mold cavities were filled out with graphite rods to avoid a chemical reaction between the wollastonite powder and the investment mate- rial. Half of the cast samples were heat treated at 1220°C for 1 h. To perform the in vitro bioactivity assessment, the cast and heat-treated samples were immersed in a simulated body fluid solution (SBF) for a period of 21 days. The surface of the samples before and after immersion in SBF was char- acterized by SEM, EDX, and XRD analyses. During the casting, particles of pseudowollastonite were embedded on the metallic surface. After immersion of the samples in SBF, a ceramic layer was formed on both the alloy obtained by using the investment mold and the alloy obtained by using the graphite-filled cavity. The ceramic layer was thicker on the alloy cast in the investment mold. The layer was identi- fied as hydroxyapatite by XRD analysis, in all the cases. The heat-treated samples after immersion in SBF showed the formation of a thin homogeneous layer consisting of fine grains of apatite. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res 78A: 34 - 41, 2006 more...

The possibility of using wollastonite as one of the main components in non-fritted opacified glazes for sanitary ceramics is demonstrated. The main physicochemical properties of synthesized coatings are determined, the specifics of their structure and phase composition are analyzed. more...

This paper provides the results of studies on the characteristics of novel material derived from pyrolysis/melting treatment of municipal solid waste in Japan. Slag products from pyrolysis/melting plants were sampled for the purpose of detailed phase analysis and characterization of heavy metal-containing phases using optical microscopy, electron probe microanalysis (EPMA), XRF and XRD. The study revealed that the slag material contains glass (over 95%), oxide and silicate minerals (spinel, melilite, pseudowollastonite), as well as individual metallic inclusions as the major constituents. A distinct chemical diversity was discovered in the interstitial glass in terms of silica content defined as low and high silica glass end members. Elevated concentrations of Zn, Cr, Cu, Pb and Ba were recorded in the bulk composition. Cu, Pb and Ba behave as incompatible elements since they have been markedly characterized as part of polymetallic alloys and insignificantly sulfides in the form of spherical metallic inclusions associated with tracer amounts of other elements such as Sb, Sn, Ni, Zn, Al, P and Si. In contrast, an appreciable amount of Zn is retained by zinc-rich end members of spinel and partially by melilite and silica glass. Chromium exhibits similar behavior, and is considerably held by Cr-rich spinel. The intense incorporation of Zn and Cr into spinel indicates the very effective enrichment of these two elements into phases more environmentally resistant than glass. There was no evidence, however, that Cu and Pb enter into the structure of the crystalline silicates or oxides that may lead to their easier leachability upon exposure to the environment. more...

Hydroxyapatite (Ca5(PO4)3(OH)) forms on pseudowollastonite (psW) (α-CaSiO3) in vitro in simulated body fluid, human parotid saliva and cell-culture medium, and in vivo in implanted rat tibias. We used crystallographic constraints with ab initio molecular orbital calculations to identify the active site and reaction mechanism for heterogeneous nucleation of the earliest calcium phosphate oligomer/phase. The active site is the planar, cyclic, silicate trimer (Si3O9) on the (0 0 1) face of psW. The trimer has three silanol groups (>SiOH) arranged at 60° from each other, providing a stereochemical match for O atoms bonded to Ca2+ on the (0 0 1) face of hydroxyapatite. Calcium phosphate nucleation is modeled in steps as hydrolysis of surface Ca–O bonds with leaching of Ca2+ into solution, protonation of the surface Si–O groups to form silanols, calcium sorption as an inner-sphere surface complex and, attachment of HPO42−. Our model explains the experimental solution and high resolution transmission electron microscopy data for epitaxial hydroxyapatite growth on psW in vitro and in vivo. We propose that the cyclic silicate trimer is the universal active site for heterogeneous, stereochemically promoted nucleation on silicate-based bioactive ceramics. A critical active site-density and a point of zero charge of the bioceramic less than physiological pH are required for bioactivity. more...

The potential of an inexpensive and simple method to control the solubilities of hazardous heavy metals such as Pb and Cr from CaO rich melting furnace fly ash (MFFA) by addition of silica and alumina with preceding heat-treatment was demonstrated. The addition of SiO2 and Al2O3 to melting furnace fly ash with preceding heat-treatment at 700°C resulted in a decrease in the pHs of the leachates from 12.4 to 11.2 and in a remarkable reduction of leachabilities of heavy metals although the leachability of Cd was below the ICP-AES detection limit (0.04 mg/l) even without the addition. In the CaO-SiO2-Al2O3 system the solubilities of Pb, Cr and Cu were much lower in the area where 3CaO·Al2O3, gehlenite, CaO·Al2O3 and anorthite deposit. The solubility of Zn was also much lower in the area where pseudowollastonite, rankinite and 3CaO·SiO2 as well as the above-mentioned minerals deposit. The leachabilities were fairly well correlated with practical parameters of CaO/(CaO + SiO2 + Al2O3) (or (SiO2 + Al2O3)/CaO) and Al2O3/(CaO + SiO2 + Al2O3) (or Al2O3/CaO) for Pb and CaO/(CaO + SiO2 + Al2O3) (or (SiO2 + Al2O3)/CaO) for Cu in the range of the present study. For Cr and Zn the leachabilities were very low in the range of the present study and no particular correlations were found. The significant reduction in their solubilities was confirmed not being caused by their volatilization during heat-treatment. more...

The devitrification kinetics and mechanism of a low-dielectric, low-temperature, cofirable K2O–CaO–SrO–BaO–B2O3–SiO2 glass-ceramic have been investigated. Crystalline phases including cristobalite (SiO2) and pseudowollastonite ((Ca,Ba,Sr) SiO3) are formed during firing. Activation energy analysis shows that the nucleation of the crystalline phases is controlled by phase separation of the glass. The crystallization kinetics of both cristobalite and pseudowollastonite obey Avrami-like behavior, and the results show an apparent activation energy close to that of the diffusion of alkaline and alkali ions in the glass, suggesting that diffusion is rate limiting. The above conclusion is further supported by analysis of measured growth rates. more...

Secondary Ca,Fe-rich minerals (CFM; diopside-hedenbergite, andradite, wollastonite, kirschteinite) are widespread in the Allende carbonaceous chondrite. About 90 vol% of the total CaO content of the Allende matrix is concentrated in CFM. The conditions and environment (solar nebular or asteroidal) of this alteration are still matters of controversial scientific discussion. Here we present evidence for late-stage, high-temperature processes recorded in Ca,Fe-rich rims around Allende dark inclusions 3529 and IV-1 studied using scanning (SEM) and transmission electron microscopy (TEM), and electron probe microanalysis. The rims show a multilayered structure, with the outermost layer intergrown with the matrix olivines and chondrule fragments of the Allende host, indicative of in situ formation. The central portion of the rim around IV-1 contains several wollastonite polytypes (a polysynthetically twinned polytype of pseudowollastonite, wollastonite-2M, and wollastonite-1T) and an intergrowth of hedenbergite-PM (primitive monoclinic) and augite-hedenbergite ss . These findings require temperatures above 1000 °C and fast cooling rates after formation of the central part of the rim. The close occurrences of three different polymorphs of wollastonite suggest that this process was highly localized and may have resulted from shock metamorphism. more...

Pseudowollastonite ceramic (psW) is a bioactive ceramic that binds to bone when implanted in vivo and may be useful for the treatment of skeletal defects. However, there have been no studies that examined the interaction between psW and osteoblastic cells in vitro. This study investigated the suitability of psW as a substratum for cell attachment and the ability of the material to effect osteoblasts at a distance from the material surface. Fetal rat calvarial cells were plated onto the ceramic and examined by scanning electron microscopy. The findings reported show that cells attached and proliferated on the surface to the ceramic. Attachment by cells to the material can be enhanced by preincubation of psW in serum or media containing fibronectin. The adhesion of cells can be inhibited by addition of GRGDS peptides suggesting that adhesion to psW is mediated by integrin binding to adsorbed proteins. To study the effects of psW at a distance, cells were cultured in the presence but not in direct contact with the material. Subsequent changes in proliferation, alkaline phosphatase expression, and bone nodule formation were assessed. Cells grown in wells containing psW demonstrated an increase in both the rate and total numbers of bone nodules formed, although there were no differences in proliferation or alkaline phosphatase expression. Overall, these results suggest that psW is biocompatible and osteoconductive. more...

Effects of alumina on the devitrification kinetics and mechanism of a low-dielectric K2O–CaO–SrO–BaO–B2O3–SiO2 glass powder have been investigated. Crystalline phases including cristobalite (SiO2) and pseudowollastonite [(Ca, Ba, Sr)SiO3] are formed during the firing of the pure glass. With added alumina content greater than a critical value, e.g., 10–20 vol% at 900–1000°C, the above crystalline phases are completely prevented but anorthite [(Ca, Sr, Ba)Al2Si2O8] is formed. This result is attributed to the dissolution of alumina into the glass. The dissolution changes the composition of the glass to become aluminum-rich, and the dissolution kinetics of alumina into the glass is far too rapid compared with the formation of cristobalite and pseudowollastonite. The crystallization kinetics of anorthite follows the analysis of the Avrami equations, and the results show an apparent activation energy close to that of the Al–O bond strength, suggesting a reaction-controlled kinetics. more...

This study aimed to evaluate the cytotoxicity of substances leached by pseudowollastonite (CaSiO(3)). It has been previously shown that calcium (Ca(2+)) and silicate (SiO(3)(-)) ions are released from pseudowollastonite into biological solutions. Both of these ions are known to influence the biological metabolism of osteoblastic cells essential in the mineralization process and bone-bonding mechanism. The indirect toxicity evaluation was performed by extraction method, according to International Standard Organization (ISO). Pseudowollastonite pellets obtained by solid-state reaction were incubated, in culture medium, during 24, 48, 72 or 168 h at different concentrations (5, 10, 15, 50, 100, 200 mg/ml). The cytotoxicity of each extract in presence of human osteoblastic cell line (SaOS-2) was quantitatively assessed by measuring the viability (succinate dehydrogenase activity, MTT), the membrane integrity (the uptake of the neutral red by viable cells, NR) as well as the cell necrosis by measuring the lactate dehydrogenase (LDH) released in the culture medium. No significant alteration of membrane integrity or cell suffering was detectable. However, increased cell metabolism was observed for cells exposed to pseudowollastonite extract with longest extraction time (168 h). In conclusion, mineral elements leached by pseudowollastonite do not significantly affect the metabolism of osteoblastic cells. more...

The pseudoternary section “FeO”-ZnO-(CaO + SiO2) with a CaO/SiO2 weight ratio of 0.71 in equilibrium with metallic iron has been experimentally investigated in the temperature range from 1000 °C to 1300 °C (1273 to 1573 K). The liquidus surface in this pseudoternary section has been determined in the composition range of 0 to 33 wt pct ZnO and 30 to 70 wt pct (CaO + SiO2). The system contains primary-phase fields of wustite (FexZn1−xO1−y), zincite (ZnzFe1−zO), fayalite (FewZn2−wSiO4), melilite (Ca2ZnuFe1−uSi2O7), and pseudowollastonite (CaSiO3). The phase equilibria involving the liquid phase and the solid solutions have also been measured. more...

Phase-equilibrium data and the liquidus for the system “MnO”-CaO-(Al2O3-SiO2) at a manganese-rich alloy saturation have been determined in the temperature range from 1423 to 1723 K. The results are presented in the form of a pseudoternary section “MnO”-CaO-(Al2O3 + SiO2) with an Al2O3/SiO2 weight ratio of 0.41. The following primary phases are present in the range of conditions investigated: 3Al2O3·2SiO2; SiO2; MnO·Al2O3·2SiO2; (Mn,Ca)O·SiO2; 2(Mn,Ca)O·SiO2; MnO·Al2O3; (Mn,Ca)O; α-2CaO·SiO2; α′-2CaO·SiO2; 2CaO·Al2O3·SiO2; CaO·SiO2, and CaO·Al2O3·2SiO2. The presence of alumina in this system is shown to have a significant effect on the liquidus compared to the system “MnO”-CaO-SiO2, leading to the stabilization of the anorthite and gehlenite phases. more...

The pseudoternary sections FeO-ZnO-(CaO + SiO2) with CaO/SiO2 weight ratios of 0.33, 0.93, and 1.2 in equilibrium with metallic iron have been experimentally investigated in the temperature range from 1000 degreesC to 1300 degreesC (1273 to 1573 K). The liquidus surfaces in these pseudoternary sections have been experimentally determined in the composition range from 0 to 33 wt pct ZnO and 30 to 70 wt pct (CaO + SiO2). The sections contain primary-phase fields of wustite (FexZn1-xO1+y), zincite (ZnzFe1-zO), fayalite (Fu(w)Zn(2-w)SiO(4)), melilite (Ca2ZnuFe1-uSi2O7), willemite (ZnvFe2-vSiO4), dicalcium silicate (Ca2SiO4), pseudowollastonite and wollastonite (CaSiO3), and tridymite (SiO2). The phase equilibria involving the liquid phase and the solid solutions-have also been measured. more...

Crystallization and reaction kinetics of a crystallizable K2O–CaO–SrO–BaO–B2O3–SiO2 glass powder with 17–40 vol% titania powder were investigated. The initially amorphous K2O–CaO–SrO–BaO–B2O3–SiO2 glass powder formed cristobalite (SiO2) and pseudowollastonite [(Ca, Ba, Sr)SiO3] during firing. The above crystalline phases were completely replaced by a crystalline phase of titanite [(Ca, Sr, Ba)TiSiO5] when the amount of added titania was greater than a critical value, e.g., 10 vol%, at 99–1100 °C. A chemical reaction taking place at the interface between titania and the glass was attributed to the above observation. The dissolved titania changed the composition of the glass, and the dissolution kinetics was much faster than the formation of cristobalite and pseudowollastonite. Activation energy analysis showed that the crystallization of titanite [(Ca,Sr,Ba)TiSiO5] was controlled by a reaction-limiting kinetics of formation for the Ti–O bond. more...

The purpose of this study was to investigate a range of variables affecting the synthesis of a miserite glass-ceramic (GC).Miserite glass was synthesized by the melt quench technique. The crystallization kinetics of the glass were determined using Differential Thermal Analysis (DTA). The glasses were ground with dry ball-milling and then sieved to different particle sizes prior to sintering. These particle sizes were submitted to heat treatment regimes in a high temperature furnace to form the GC. The crystal phases of the GC were analyzed by X-ray diffraction (XRD). Scanning electron microscopy (SEM) was used to examine the microstructure of the cerammed glass.XRD analysis confirmed that the predominant crystalline phase of the GC was miserite along with a minor crystalline phase of cristobalite only when the particle size is20 μm and the heat treatment at 1000°C was carried out for 4h and slowly cooled at the furnace rate. For larger particle sizes and faster cooling rates, a pseudowollastonite crystalline phase was produced. Short sintering times produced either a pseudowollastonite or xonotolite crystalline phase.The current study has shown that particle size and heat treatment schedules are major factors in controlling the synthesis of miserite GC. more...

Silica aerogels have attracted increasingly more attention due to their extraordinary properties and their existing and potential applications in a wide variety of technological areas. Materials that promote bone-tissue formation at their surface and bond to osseous tissues when implanted are called bioactive, such as pseudowollastonite particles. In this work, the synthesis of aerogels with pseudowollastonite particles was performed. The synthesis involved the preparation of an alcogel by a two step sol-gel route followed by ambient pressure drying. To promote a higher bioactivity the obtained aerogels were then biomimetically treated using simulated body fluids, SBF and 1.5 SBF. A high bioactivity was demonstrated by FT-IR, SEM, EDS, and XRD. The in vitro biocompatibility was assessed by testing cytotoxicity using rat osteoblasts cultures. The results obtained indicate that these materials are highly potential aerogels for bone tissue regeneration. more...

There are approximately 35 million t of carbonate opoka and 21 million t of chalk marl in Lithuania. These materials are suitable for the production of various hydraulic binders. In this work, the influence of burning temperature (700 °C – 950 °C) and duration (0.5 h – 2 h) on the calcination of isomorphic Ca-Si rocks was investigated. The goal was to prepare a mixture of opoka and chalk marl that would be reactive enough for the hydrothermal synthesis of various calcium silicate hydrates, as this would suggest another potential use of these stocks. It was determined that the largest amount of free CaO (59.09 %) is obtained after burning opoka for 2 h at 750 °C and after burning chalk marl for 2 h at 800 °C (84.22 %). The remaining CaO is bound to the structure of poorly crystalline pseudowollastonite, which transforms to wollastonite when the temperature of the thermal treatment is increased. Because the calcination temperature of both materials is similar, they can be burned simultaneously; this would significantly simplify the preparation procedure of these mixtures. The optimal temperature for burning the opoka – chalk marl mixture with a molar ratio of CaO/SiO2 = 2 (62.8 % chalk marl and 37.2 % opoka) was determined to be 825 °C for 2 h. In this case, the amount of free CaO is the largest and the crystals of formed wollastonite are poorly crystalline. This blend was treated hydrothermally at 200 °C for 24 h. The dominant product of the synthesis was α-C2S hydrate, which in literature was reported to be the main constituent in the production of new hydraulic binder. DOI: http://dx.doi.org/10.5755/j01.ms.20.3.4426 more...

This paper reports on the structural morphology of the interface in vivo between implants composed of bioactive synthetic pseudowollastonite ceramic and bone in rat tibias. Thin sections of the interfaces were examined after 6 and 8 weeks of implantation period in a high resolution transmission electron microscope up to the lattice plane resolution level. The interfaces developed normal biological and chemical activities and remained reactive over the 8-week period. The regions showing direct bone tissue bonding to the implant contained nanocrystals of hydroxyapatite-like phase growing epitaxially across the interface in the [002] direction. The nanocrystals were also identified in the bone tissue formed in the interfacial area. The reactivity of the implant caused in the first instance formation of an amorphous woven type of bone, which transformed into a crystalline lamellar type containing collagen fibres. The Ca/P ratio of the interfacial region was found to be between 1.67 in the mature bone tissue formed about 5 microm from the interface, and 2.06 in the regions right at the interface. more...

The crystal structure of a synthetic two-layer polytype of CaSiO 3 pseudowollastonite was determined using single-crystal X-ray diffraction data. It is monoclinic with space group C2/c and unitcell parameters a = 11.8322(6), b = 6.8624(8), c = 10.5297(5) A, β = 111.245(8)°, and V = 796.9(1) A 3 . The material is isostructural with two-layer SrSiO 3 and SrGeO3 and has basic structural features similar to those found in four-layer CaSiO 3 pseudowollastonite, except for the stacking sequence of layers of CaO6 octahedra and Si3O9 ternary rings. The compressibility of the structure was measured up to 9.94 GPa and no phase transition was observed. With increasing pressure, all unit-cell parameters decrease nonlinearly with a positive curvature. The axial compression ratios at room pressure are βa:βb:βc = 2.25:2.36:1.00 and the bulk modulus, KT, is 86(1) GPa with K' = ∂KT/ ∂P = 3.8(4). more...

Diopside (CaMgSi2O6) and pseudowollastonite (CaSiO3) have been studied by X-ray powder diffraction and Raman spectroscopy up to their respective melting points. In agreement with previous unit-cell parameters determinations below 1100 K, thermal expansion of diopside along the a and c axis is much smaller than along the b axis. For pseudowollastonite, the axis expansivity increases slightly in the order b>a>c. For both minerals, the change in unit-cell angles is very small and there are no anomalous variations of the other unit-cell parameters near the melting point. With increasing temperatures, the main changes observed in the Raman spectra are strong increases of the linewidths for those bands which mainly represent Si−O−Si bending (near 600 cm−1) or involve Ca−O or Mg−O stretching, in the range 270–500 cm−1 for diopside, and 240–450 cm−1 for pseudowollastonite. At temperatures near the onset of calorimetric premelting effects, this extensive band widening results in a broad Raman feature that can no longer be deconvoluted into its individual components. No significant changes affect the Si−O streching modes. For both diopside and pseudowollastonite, premelting appears to be associated with enhanced dynamics of the alkaline-earth elements. This conclusion contrasts markedly with that drawn for sodium metasilicate in which weaker bonding of sodium allows the silicate framework to distort and deform in such a way as to prefigure the silicate entities present in the melt. more...

The study investigated the morphology and structure of interfaces between a pseudowollastonite (psW) and α-tricalcium phosphate (α-TCP) eutectic ceramic material (Bioeutectic®) obtained by slow solidification (0.5 °C h−1) through the eutectic temperature region (1402 ± 3 °C) of the binary system. The eutectic material contained 60 wt% psW and 40 wt% α-TCP and was composed of spherical colonies formed by alternating radial lamellae of psW and α-TCP phases. Small quantities of impurities were found to affect the microstructure and ultrastructure of adjacent colonies. The observations showed the presence of dislocation loops and dislocation pairs in the psW phase away from the interfaces with α-TCP. The α-TCP phase remained defect-free. Two types of interface were identified between the triclinic high-temperature form of wollastonite (psW) and orthorhombic α-TCP. In single colonies, the phases were aligned with [011¯]psW and [001¯] α-TCP. High-resolution electron microscopy revealed differences in morphologies between the two interfaces, and showed that the lattice planes in the interfaces were defect-free. more...

Preliminary in vitro experiments revealed that wollastonite (CaSiO3) is a potentially highly bioactive material that forms a hyroxyapatite (HA) surface layer on exposure to simulated body fluid with an ion concentration, pH and temperature virtually identical with those of human blood plasma. The formation of the HA layer is an essential requirement for an artificial material to be used as bioactive bone substitute. This finding opens up a wide field for biomedical applications of wollastonite. Biomaterials used as implants in the human body require strict control of trace elements and of the toxic species specified in American Society for Testing and Materials F-1185-88 (As, Cd, Hg and Pb) in ceramic hydroxyapatite for surgical implantation. In this work, two types of pseudowollastonite, the high temperature form of wollastonite, were analysed by using cold vapour atomic absorption spectrometry and hydride generation atomic absorption spectrometry, in order to determine the elements stated in the above-mentioned norm, and inductively coupled plasma atomic emission spectrometry to establish the SiO2/CaO ratio of the two materials and analyse for all other impurities introduced by the raw materials and by the processes of synthesis, sintering and grinding. Barium and Mg were especially prominent in raw materials, and Zr, Y, Mg, W, Co and Ni come mainly from the processing. more...

A study of the CaO-SiO2-MgO-CaF2 system was undertaken to determine the effect of the various precipitated mineral species on slag rheology. Slags prepared included both basic and acid variations. Three mineralogical species were found in the basic slags; merwinite, monticellite and rankinite. Solidification behaviour was influenced by the concentration of each component, with the more basic slags containing more merwinite and monticellite; this resulted in higher solidification temperatures for these melts. The acidic slags examined contained several variations of impure pseudowollastonite as well as impure calcium fluoride. In selected slag mixtures, the fluorspar component was replaced with an alkalialuminosilicate tailings material to assess its suitability as a fluorspar substitute. The new slag system was slightly more viscous than comparable slags containing fluorspar; however, the shape of the temperature-viscosity profile was more favourable with respect to an industrial environment. Mineralogical phases encountered here were merwinite, monticellite and akermanite, precipitated from a complex calcia-mag-nesia-alumino-silicate melt. more...

We derived a thermodynamic dataset for the phases in the CaSiO3 system including the wollastonite polymorphs (wollastonite-I, wollastonite-II, and pseudowollastonite), larnite (β-Ca2SiO4), CaSi2O5 (titanite-like), CaSiO3 perovskite, and CaSiO3 liquid by using the available data on thermochemical, thermophysical, and volumetric properties of the phases and phase equilibrium relations. A relatively large amount of experimental information which became available recently on the enthalpy, entropy, heat capacity, and volumetric properties of the low-pressure solid phases and the CaSiO3 liquid was included in the evaluation. With the exception of the pressure-temperature-volume data for CaSiO3 perovskite, experimental measurements for the high-pressure phases CaSi2O5 titanite-like and CaSiO3 perovskite are entirely lacking. For these phases, we used estimates obtained with the method of quasiharmonic lattice dynamic simulation with a parameterized interatomic potential. Our thermodynamic assessment using all these data in combination with the published phase equilibrium data up to 16 GPa and 3000 K has resulted in a dataset which can be used to calculate the phase relations in the system up to 20 GPa and 3000 K. Our work represents the first attempt to evaluate a complete set of thermodynamic properties including enthalpy, entropy, and heat capacity for the high-pressure phases CaSi2O5 titanite-like and CaSiO3 perovskite. more...

The structures and physical properties of diopside, walstromite, wollastonite, parawollastonite, pseudowollastonite, wollastonite-II, and CaSiO3 perovskite were simulated by computational models using energy minimization technique. The potential energies of these crystals are approximated by the sum of Coulomb, van der Waals, and repulsion terms between atoms. Required potential energy parameters of Ca and Ba were determined by fitting the calculated crystal structures of diopside and walstromite, and calculated bulk modulus of diopside to the observed ones. Using the obtained potential parameters of Ca and Ba, together with those of Mg, Si, and O derived from Matsui (1988), crystal structures of wollastonite, parawollastonite, pseudowollastonite, wollastonite-II, and CaSiO3 perovskite were reproduced well. The elastic constants of diopside and the bulk modulus of CaSiO3 perovskite were also simulated, and the values are in agreement with experimental data. These potential parameters were applied to predicting the bulk moduli and linear compressibilities of interatomic bonds of these crystals. The results of these calculations show that bulk modulus and compressibilities of M(Mg,Ca,Ba)-O bonds are related with crystal structures. more...

Transposed-temperature-drop calorimetry performed in a Setaram HT 1500 calorimeter was used to study directly the melting of mixtures of crystalline diopside (CaMgSi 2 O 6 , anorthite (CaAl 2 Si 2 O 8 ), and pseudowollastonite (Wo, CaSiO 3 ) at 1773 K. Thermochemical cycles used completely avoid the glassy state by transforming crystals directly to melts. The results, zero or slightly negative enthalpies of mixing in Di-An-Wo melts at 1773 K, indicate that very small heat effects accompany any changes in melt structure upon mixing. Athermal mixing is prevalent in the diopside-rich region and along the Di-An join, whereas mixing is slightly exothermic in the rest of the Di-An-Wo system, especially in the Wo-rich region. Our data are consistent with an enthalpy of fusion of pseudowollastonite of 57 ± 5 kJ/mol at the melting point, 1827 K. more...

High-temperature calorimetry experiments show that the isobaric heat capacity (C(p)) of minerals increases in an anomalously rapid way when the melting point is approached. These premelting effects can begin a few hundred degrees below the melting point, and they should also be observed for other physical properties such as the thermal expansion, compressibility and sound velocities. Premelting could thus affect the properties of partially molten rocks. In this study, new evidence for diopside (CaMgSi2O6), pseudowollastonite (CaSiO3), anorthite (CaAl2Si2O8), akermanite (Ca2MgSi2O7), Na2SiO3, L2SiO3 and CaMgGeO4 olivine obtained by means of calorimetry, electron microscopy and vibrational spectroscopy, demonstrates that premelting represents unquenchable configurational changes within phases remaining crystalline up to the reported melting points. The enthalpy and entropy effects of premelting are consistent with cation disordering over the various crystallographic sites of the structures. More generally, such temperature-induced cation disordering could be at the roots of intrinsic anharmonicity in oxide and silicate compounds. more...

This contribution reports on the elaboration of novel bioresorbable composites consisting of pseudowollastonite (psW) (a silicate-based polycrystalline ceramic (α-CaSiO(3))) and poly(L,L-lactide) as a valuable polymeric candidate in bone-guided regeneration. These composites were prepared by direct melt-blending to avoid the use of organic solvents harmful for biomedical applications. Amphiphilic poly(ethylene oxide-b-L,L-lactide) diblock copolymers synthesized by ring-opening polymerization were added to psW-based composites to modulate the bioactivity of the composites. The bioactivity of the composites was first evaluated by monitoring the release of bioactive Ca(2+) and (SiO(4))(4-) ions as well as the concomitant formation of hydroxyapatite on the material surface after soaking them in physiological fluid. Subsequently, the composites were studied in vitro to evaluate their cytotoxicity in the presence of SaOS-2 osteoblastic cells and in vivo to assess their osteoconductivity in an orthotopic rat tibia model. This study provides a first insight into the use of direct melt-blended psW-poly(L,L-lactide) composites for bone-regeneration applications. more...

Sterilization is required for using any material or device in contact with the human body. The aim of this work was to investigate the effect of four sterilization methods (steam autoclave, hydrogen peroxide plasma, ethylene oxide, and gamma sterilization) on the surface chemistry and in vitro bioactivity of pseudowollastonite (psW) coatings in titanium alloys substrates. psW coatings in Ti-6Al-4V substrates obtained by laser ablation technique were sterilized and immersed in Kokubo's simulated body fluid (SBF) up to 30 days. No changes in the chemical composition were noted after sterilization. However, a Ca/P-layer of different thickness, identified as hydroxyapatite (HA) like was developed on all the samples after soaking, although, the ethylene oxide sterilized samples present a nonhomogeneous and ∼55.9% thinner HA-like layer. © 2010 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2010. more...

Phase relations in the system CaO–chromium oxide–SiO2 were determined (a) in equilibrium with metallic chromium and (b) at various oxygen pressures in the range of ∼ 10−10 to 10−13 atm. Two ternary phases occur on the liquidus surface in equilibrium with metallic chromium, viz, the garnet Ca3Cr2Si3O12 (uvarovite), and CaCrSi4O10 of the gillespite-type structure and in which essentially all the chromium is present in the divalent state (Cr2+). Furthermore, a previously reported binary calcium chromite phase “X” of approximate composition (Ca0.4Cr0.6)Cr2O4 is stable also on the liquidus surface of the present system. The lowest liquidus and solidus temperatures in the system under these conditions (contact with metallic chromium) are significantly lower (by 100° to 200°C, depending on CaO/SiO2 ratios of the melts) than those for the same system in air. Furthermore, there is considerable solid solution of chromium oxide in lime (CaO) and the various crystalline calcium silicates (pseudowollastonite, CaSiO3; rankinite, Ca3Si2O7; dicalcium silicate, Ca2SiO4; tricalcium silicate, Ca3SiO5), presumably by partial substitution of Cr2+ for Ca2+ toward hypothetical chromium analogs of each CaO-containing phase, particularly in lime and Ca2SiO4. At the somewhat higher oxygen pressures imposed by the CO2─H2 gas mixtures of CO2/H2 ratios of 1/24 and 1/8.1, the phases containing most of the chromium in the divalent state (CaCrSi4O10 and (Ca0.4Cr0.6)Cr2O4) do not appear on the liquidus surface, the primary phase area of garnet (uvarovite) decreases, the lowest liquidus and solidus temperatures increase noticeably (−50° to 100°C), and the amounts of chromium substituting in lime and the various crystalline calcium silicate phases (CaSiO3, Ca3Si2O7, Ca2SiO4, and Ca3SiO5) decrease considerably from those observed for the system in equilibrium with metallic chromium. Combination of the data obtained under these reducing conditions with those previously reported for the system under more oxidizing conditions permits derivation of the general features of phase relations in the quaternary system CaO─CrO─Cr2O3─SiO2. more...

Results of studying the process of sintering of two similar-type ceramic mixtures made of three varieties of low-melting illite-containing clays with additives of nepheline sienite and synthetic pseudowollastonite are described. The expediency of using several varieties of similar-type clays with different mineralogical and granulometric compositions to expand the sintering interval is shown. more...

The aim of this work was to study the influence of the composition and thermal treatment of the in vitro bioactivity of wollastonite materials obtained by sol-gel method. For this purpose, gels in the system SiO(2)-CaO were obtained applying calcium nitrate and tetraethoxysilicate as precursors. The gels were heated to 700 °C and then sintered up to 1400 °C. The bioactivity of the gel-derived materials in simulated body fluid (SBF) was investigated and characterized. Additional changes in ionic concentration, using inductively couple plasma atomic emission spectroscopy (ICP-AES), were determined. The results showed that all materials obtained were bioactive and indicate that the absence of phosphorous in the material composition is not an essential requirement for the development of a Hydroxyapatite layer. The bioactivity was influenced by the thermal treatment, the different phases (glass-phase, wollastonite and pseudowollastonite) as well as the porous size. On the gel-derived materials the bioactivity decreased with the sintering temperature. more...