Should the oxygen source be considered in the initiation of KCl-induced high-temperature corrosion?

The role of two oxygen sources, oxygen and water vapor, in the initiation of KCl-induced high-temperature corrosion was addressed by studying two high-alloyed commercial materials at 550 \ub0C. The differentiation between the two oxygen sources was implemented with 18O-enriched water and 16O2. Based on the results, the solid-solid reaction between KCl(s) and the protective oxide on the alloy surface appeared to be more responsible for corrosion than the gas-solid reaction between KCl(g) and the protective oxide. Water was more involved in the abovementioned reactions than O2: 18O was the main oxygen isotope found in the formed surface oxides and intermediates

Glass as a biomaterial: strategies for optimising bioactive glasses for clinical applications

Bioactive glasses were the first synthetic materials to bond to human body tissue, making them ideal for replacing and regenerating bone. Since their first development over half a century ago, many new bioactive glass compositions have been developed for medicine and dentistry. This paper looks at different design strategies employed over the years as well as aspects of glass structure relevant to optimising bioactive glass performance. Statistical compositional series allowed for getting an overview of various compositions and their properties. Since the improvement of structural analysis techniques, particularly solid-state NMR, we can directly relate several bioactive glass properties to the atomic structure, i.e. the spatial arrangement of atoms. Such detailed understanding of the impact of composition and structure on bioactive glass properties enables us to minimise the number of compositions in preclinical and clinical tests needed to confirm positive tissue responses

Glass as a biomaterial: strategies for optimising bioactive glasses for clinical applications

Bioactive glasses were the first synthetic materials to bond to human body tissue, making them ideal for replacing and regenerating bone. Since their first development over half a century ago, many new bioactive glass compositions have been developed for medicine and dentistry. This paper looks at different design strategies employed over the years as well as aspects of glass structure relevant to optimising bioactive glass performance. Statistical compositional series allowed for getting an overview of various compositions and their properties. Since the improvement of structural analysis techniques, particularly solid-state NMR, we can directly relate several bioactive glass properties to the atomic structure, i.e. the spatial arrangement of atoms. Such detailed understanding of the impact of composition and structure on bioactive glass properties enables us to minimise the number of compositions in preclinical and clinical tests needed to confirm positive tissue responses

Understanding the Interaction of Potassium Salts with an Ilmenite Oxygen Carrier under Dry and Wet Conditions

This study describes how potassium salts representative of those in bio ash affect the reactivity of the oxygen carrier ilmenite under moist and dry conditions. Ilmenite is a bench-mark oxygen carrier for chemical-looping combustion, a technique that can separate CO2 from flue gases with minimal energy penalty. Different potassium salts were mixed with ilmenite to a concentration of 4 wt % potassium. The salts used were K2CO3, K2SO4, KCl, and KH2PO4. Experiments were performed at 850 \ub0C under alternately oxidizing and reducing conditions in a dry atmosphere or in the presence of steam. Analyses of the oxygen carrier regarding changes in reactivity, structure, and composition followed the exposures. This study showed that salts such as K2CO3, K2SO4, and KCl increase the reactivity of the ilmenite. For the samples mixed with KCl, most of the salt was evaporated. KH2PO4 decomposed into KPO3, forming layers around the ilmenite particles that lead to agglomeration. Additionally, the KPO3 layer was more or less nonpermeable for CO and decreased the reactivity toward H2 significantly in both dry and wet conditions. This decreased reactivity indicates that the concentration of phosphorus in biofuel may have a significant effect on oxygen carrier degradation. It was also observed that the presence of steam changed the chemistry drastically for the nonphosphorus-containing salts. Alkali salts may react with steam, forming volatile KOH that evaporates partly. KOH may also form K-titanates by reaction with the oxygen carrier, leading to segregation of iron and titanium phases in the ilmenite. \ua

The Fast Silver Ion Conducting Solid-State Electrolytes for Deriving Thermodynamic Data

The electromotive force (EMF) method was described and some characteristic examples from the past and recent literatures were reviewed. The important experimental procedures for a successful measurement of an EMF of different galvanic cells at a certain temperature and determination of the thermodynamic properties of chemical compounds from the obtained EMF values were described. A typical galvanic cell arrangement in a furnace was presented. The two most common types of AgI-based solid electrolytes, AgI and RbAg4I5, were discussed in detail. The ionic conduction mechanisms and the application of the solid electrolytes in the EMF cells were described. In this work, we have also conducted EMF measurements using the fast Ag+ ion conducting solid-state electrolyte. The solid-state electrolyte Ag3GeS3I glass and the cathode material Ag4HgSe2I2 were synthesized and electrochemical cell (−)graphite|Ag|Ag3GeS3I glass|Ag4HgSe2I2|graphite(+) was assembled to measure the activity of Ag in the quaternary phase. The extremely low values of activity of silver in Ag4HgSe2I2 in the temperature range 412–482 K indicate that Ag4HgSe2I2 has superionic property. The obtained results and the determined thermodynamic values are presented and discussed

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The effect of fibrin sealant on bioactive glass S53P4 particles – pH impact and dissolution characteristics in vitro

Fibrin glue, a two-component tissue adhesive, has a range of clinical indications. Bioactive glass (BG) S53P4 has been approved for clinical use in several craniomaxillofacial and orthopedic applications. Although sometimes used simultaneously, there is no data available regarding the possible interaction of these two biocompatible substances. In this in vitro study, using a BG particle concentration of 4 mg/ml, a 0.4 unit pH increment (p<0.001) was observed in simulated body fluid (SBF) after a 7-day incubation period. The addition of fibrin glue (0.13 g, SD 0.04; or 3.7 mg/ml) on top of the BG particles raised further the pH by 0.5 units (p<0.001). The difference between these groups was statistically significant (p=0.008). With a BG concentration of 25 mg/ml and a fibrin glue concentration of 18 mg/ml during a 14-day incubation period, a pH increment of 0.6 units and SBF ion concentration change of Ca, K, Mg, Na, P and Si ions was seen. Moreover, a penetration depth between 4 and 6 mm was observed when fibrin glue was applied on top of a bed of BG particles. Conclusions: Fibrin glue is not likely to have a distracting effect on BG-induced pH increase of the SBF although it might delay early BG surface reactions based on ion concentration measurements. Fibrin glue penetrated to the interparticle space to some extent, binding the particles together for easy clinical use of BG. </p

Effect of bioactive glass air-abrasion on Fusobacterium nucleatum and Porphyromonas gingivalis biofilm formed on moderately rough titanium surface

This aim of this study was to investigate the effects of three types of air-abrasion particles on dual-species biofilms of Fusobacterium nucleatum and Porphyromonas gingivalis, both of which were cultured on sandblasted and acid-etched (SA) titanium discs. Out of 24 SA discs with biofilm, 18 were exposed to either air-abrasion using Bioglass 45S5 (45S5 BG; n = 6), novel zinc (Zn)-containing bioactive glass (Zn4 BG; n = 6), or inert glass (n = 6). The efficiency of biofilm removal was evaluated using scanning electron microscopy (SEM) imaging and culturing techniques. Air-abrasion using 45S5 BG or Zn4 BG demonstrated a significant decrease in the total number of viable bacteria compared to discs air-abraded with inert glass or intact biofilm without abrasion. Moreover, P. gingivalis could not be detected from SEM images nor culture plates after air-abrasion with 45S5 BG or Zn4 BG. The present study showed that air-abrasion with 45S5 or Zn4 bioactive glasses can successfully eradicate dual-biofilm of F. nucleatum and P. gingivalis from sandblasted and acid-etched titanium discs.</p

Effect of bioactive glass air-abrasion on the wettability and osteoblast proliferation on sandblasted and acid-etched titanium surfaces

The aim of this study was to evaluate the hydrophilicity, surface free energy, and proliferation and viability of human osteoblast-like MC3T3-E1 cells on sandblasted and acid-etched titanium surfaces after air-abrasion with 45S5 bioactive glass, zinc-containing bioactive glass, or inert glass. Sandblasted and acid-etched titanium discs were subjected to air-abrasion with 45S5 bioactive glass, experimental bioactive glass (Zn4), or inert glass. Water contact angles and surface free energy were evaluated. The surfaces were studied with preosteoblastic MC3T3-E1 cells. Air-abrasion with either type of glass significantly enhanced the hydrophilicity and surface free energy of the sandblasted and acid-etched titanium discs. The MC3T3-E1 cell number was higher for substrates air-abraded with Zn4 bioactive glass and similar to that observed on borosilicate coverslips (controls). Confocal laser scanning microscopy images showed that MC3T3-E1 cells did not spread as extensively on the sandblasted and acid-etched and bioactive glass-abraded surfaces as they did on control surfaces. However, for 45S5- and Zn4-treated samples, the cells spread most at the 24 h time point and changed their morphology to more spindle-like when cultured further. Air-abrasion with bioactive glass and inert glass was shown to have a significant effect on the wettability and surface free energy of the surfaces under investigation. Osteoblast cell proliferation on sandblasted and acid-etched titanium discs was enhanced by air-abrasion with 45S5 bioactive glass and experimental Zn4 bioactive glass compared with air-abrasion with inert glass or no air-abrasion

Antibacterial properties of bioactive glass particle abraded titanium against Streptococcus mutans

The purpose of this study was to evaluate effects of titanium surfaces air-abraded with particles of Bioglass® 45S5 and three-ZnO and SrO doped compositions on the viability, adhesion and biofilm formation of Streptococcus mutans. A statistically significant decrease in the viability of S. mutans was observed for all titanium discs air-particle abraded with the BAGs (p S. mutans adhesion on titanium surfaces treated with different glasses (p = 0.964). Static SBF immersion experiments showed that after 2 and 48 h the BAG doped with 4 mol% ZnO demonstrated the highest Zn2+ ion concentration released into SBF (0.2 mg L−1). 45S5 BAG demonstrated the highest statistically significant increase in the pH throughout the 120 min of static immersion (p S. mutans and they suppressed S. mutans biofilm formation. The antimicrobial activity of 45S5 BAG was attributed to high pH whereas for the Zn-containing BAGs antimicrobial activity was due to steady release of Zn2+ into the interfacial solution.</p