Characterization of altered mica from Sokli, northern Finland

Vermiculite is a mineral with many potential uses in various industrial areas, such as in insulation, horticulture, and environmental applications. The regolith of the Sokli carbonatite intrusion in northern Finland consists of weathered micas which reportedly contain vermiculite. The aim of the present study was to characterize the weathered mica in order to determine if the weathered regolith contains vermiculite. If so, the value of the apatite-rich Sokli intrusion may increase, because the vermiculite could be classified as an ore in Sokli. For the characterization, mica fractions were investigated using electron probe microanalysis (EPMA), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The EPMA results show that the potassium (K2O) content of the mica investigated varies between 6.20 and 0.31 wt.%. The XRD results provided evidence thatthe interlayer distances in the mica vary between 10.1 and 14.7 Å. The TGA shows that the dehydration of the samples varies between 6 and 12 wt.% for temperatures up to 170°C. Dehydroxylation takes place in three steps, as is characteristic for vermiculite. The results from this study revealed that mica in the weathered parts of the Sokli carbonatite is mostly vermiculite, and that the vermiculite was formed by the weathering of phlogopite. These results can be used to determine whether vermiculite is a possible future commodity at the Sokli carbonatite complex.</p

Grit blasted aggregates of hydroxyl apatite functionalized calcium carbonate in occluding dentinal tubules

ObjectivesThis study aimed to investigate the effects of using hydroxyl apatite functionalized calcium carbonate (FCC) particles on occluding dentinal tubules.MethodsDentine specimens extracted from eighteen human molars with exposed dentinal tubules were divided into three groups (n = 6/group): a) Cut surface with smear layer; b) EDTA (smear layer removed with 17% EDTA for 1 min); and c) Grit blasted functionalized calcium carbonate (FCC) with and air pressure of 280 kPa. Microscopic dentinal tubule occlusion, tubule diameter and tubule area were evaluated using scanning electron microscopy (SEM) before and after grit blasting. Biomineralization of specimens was carried out in a simulated body fluid (SBF). Elemental analysis of occluding materials was carried out using energy-dispersive X-ray spectroscopy (EDX). X-ray diffraction (XRD) analysis was performed to demonstrate the crystal structure of the biomineralized layer on dentine.ResultsFCC particles showed penetration into the dentinal tubules by breakage of their original particle shape and size. EDTA treated surface had higher number and larger size tubules than those with smear layer or grit blasted (p ConclusionsGrit blasted FCC particles initially occluded effectively the opened dentinal tubules and biomineralization occurred in tubules primarily occluded by the FCC particles. However, in the optimal in vitro conditions in SBF, no difference between biomineralization was found between the grit blasted surface and the control surface.Clinical significanceSeveral materials and methods have been established for treatment of dentinal hypersensitivity although a golden standard treatment has not been discovered. Grit blasted functionalized calcium carbonate has a potential to occlude and remineralize exposed dentinal tubules. This could offer a more biological approach on treatment of dentin hypersensitivity.<br /

Physicochemical and biological characterization of silica-coated alumina particles

ObjectivesA tribochemical silica-coating (TSC) method has been developed to improve the adhesion of dental resin composites to various substrates. The method utilizes airborne-particle abrasion using particles having a silica surface and an alumina core. The impact of the TSC method has been extensively studied but less attention has been paid to the characterization of the silica-modified alumina particles. Due to the role of silicate ions in cell biology, e.g. osteoblast function and bone mineralization, silica-modified alumina particles could also be potentially used as a biomaterial in scaffolds of tissue regeneration. Thus, we carried out detailed physicochemical characterization of the silica-modified alumina particles.MethodsSilica-modified alumina particles (Rocatec, 3 M-ESPE) of an average particle size of 30 µm were studied for the phase composition, spectroscopic properties, surface morphology, dissolution, and the capability to modify the pH of an immersion solution. The control material was alumina without silica modification. Pre-osteoblastic MC3T3-E1 cells were used to assess cell viability in the presence of the particles. Cell viability was tested at 1, 3, 7 and 10 days of culture with various particle quantities. Multivariate ANOVA was used for statistical analyses.ResultsMinor quantities of silica enrichment was verified on the surface of alumina particles and the silica did not evenly cover the alumina surface. In the dissolution test, no change in the pH of the immersion solution was observed in the presence of the particles. Minor quantities of silicate ions were dissolved from the particles to the cell culture medium but no major differences were observed in the viability of pre-osteoblastic cells, whether the cells were cultured with silica-modified or plain alumina particles.SignificanceCharacterization of silica-modified alumina particles demonstrated differences in the particle surface structure compared to control alumina. Dissolution of silica layer in Tris buffer or SBF solution varied from that of cell culture medium: minor quantities of dissolved Si were observed in cell culture test medium. The cell viability test did not shown significant differences between control alumina and its silica-modified counterpart.</p

Structural and elemental characterization of glass and ceramic particles for bone surgery

AbstractObjectiveClinically used bioceramics have been characterized previously with different kinds of methods and comparison of results have proven to be difficult due to varieties of the material properties of interest. Therefore, in this study we compared clinically commonly used bioceramics of hydroxyapatite and carbonate apatite, two bioactive glasses 45S5 and S53P4, and alumina with respect of properties which according to the present knowledge are significant for bone biology.MethodsPhysicochemical properties of the materials were characterized by various methods. Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) was used to analyze the material vibrational features. X-ray Power Diffraction (XRD) was used to characterize the material crystal structure and scanning electron microscopy-energy-dispersive x-ray analysis (SEM-EDXA) was used to evaluate the morphology and size of the materials and to calculate their oxide content. The dissolution behavior of the materials, ion release and pH changes in Tris buffer in a continuous flow-through reaction for 24-hours were determined. The change of the surface of the bioactive glasses by interfacial reaction during the Tris immersion was examined and the thickness of the surface reaction layer of the materials was studied.ResultsSEM examination showed that the particle morphology of BG 45S5, BG S53P4 and alumina particle’s surface was smooth. The surface of HAP was porous, but also CAP showed some surface porosity. An increase in the pH of the immersion solution was observed especially for BG 45S5 and BG S53P4. HAP, CAP and alumina caused only a minor increase in pH. BGs 45S5 and S53P4 showed a rapid initial release of sodium and calcium ions, followed by the release of silicon species. Minor release of sodium ions was registered for HAP, CAP and alumina. Calcium ion release was low but constant over the experimental time while only a minor initial dissolution was measured for HAP.SignificanceThe in vitro study showed differences in the materials’ properties, which are considered to be important for biological suitability and in clinical applications, such as materials tomography, ion release and pH changes.</p

Hierarchically Porous Metal Oxide Monoliths Prepared by the Nanocasting Route

In this paper, successful preparations of hierarchically porous cobalt oxide (Co3O4), tin oxide (SnO2), and manganese oxide (MnO2 or Mn2O3) monoliths by the nanocasting route are described. The starting SiO2 monoliths used as molds were prepared through a straightforward sol−gel process and contain macropores with adjustable size in the range of 0.5−30 μm as well as mesopores which can be altered between 3 and 30 nm. In the nanocasting process, the silica monoliths are impregnated with a metal salt solution, which is subsequently decomposed to a metal oxide by heat treatments to form a SiO2/MeOx composite. Finally, the silica part can be removed by leaching in either NaOH or hydrofluoric acid. The composite and replica structures have been characterized by thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, nitrogen physisorption, and transmission electron microscopy. The nanocast monoliths are positive replicas of the silica structure on the micrometer scale, meaning that the replicas have the same macroscopic morphology and macropore structure as the starting silica monoliths. In contrast, on the nanometer scale the replicated structure becomes an inverse (or a negative replica) of the silica mesopore structure. Furthermore, all prepared metal oxide monoliths are fully crystalline. When the hierarchical structure of the monoliths is combined with the unique chemical or physical properties of the used metal oxides, these novel materials have great potential in application areas such as catalysis, HPLC, and sensor materials