Scanning Electron Microscope With An Energy Dispersive Spectrometer Research Articles

Trace Element Composition of Placer Gold Across the Okanagan Fault, Kelowna, British Columbia, Canada

For 100 years, placer gold has been important to the settlement, economic development, and, recently, recreational geology of the Kelowna, British Columbia, area. It is best-known to occur in modern-day, Mission Creek and Lambly Creek sedimentary rocks, as well as a paleoplacer occurrence in Miocene sediments of the historical Winfield mine. The Mission Creek and Winfield localities are east of the west-dipping, low-angle, normal Okanagan Fault, which has been active since the Eocene. Lambly Creek is west of the fault. Late Paleozoic to Eocene igneous and metasedimentary rocks occur in the Lambly Creek catchment but Eocene gneiss units, unroofed by the fault, occur on the Okanagan Valley’s east side. This study tests the hypothesis that native placer gold compositions vary across the Okanagan Fault reflecting different sources and histories for the gold. A modest number of Au and Ag analyses (23 analyses) in usefully representative placer gold samples were determined on a scanning electron microscope with an energy dispersive spectrometer (SEM-EDS). Spots analyzed for Au and Ag were also analyzed for 19 trace elements using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Mercury was semi-quantitatively determined in ‘unknown’ gold grains by first estimating its concentration (~3.69 ppm) in the AuRM2 external standard. Proportions of Au:Ag:Cu in grain cores indicate all the gold came from mesothermal/hypogene or possibly Au porphyry bedrock deposits though primary signatures may have been obscured by metamorphism or weathering. Winfield and Mission Creek grains tend to have higher siderophile Fe, Ni, Pd and Pt and chalcophile elements As, Se, Te, Hg, Pb and Bi but lower Cu and Sb concentrations than Lambly Creek gold. Mercury is distinctly higher in Winfield and Mission Creek gold than in Lambly Creek gold from the west side of the valley; the element appears particularly useful for ‘fingerprinting’ gold. Lambly Creek gold compositions indicate derivation from two orogenic/hypogene sources from greenstone and plutonic/hydrothermal rocks present in the catchment area. Modern day Mission Creek and Miocene paleoplacer Winfield grains have a similar hypogene trace element signature but there are no known local bedrock gold sources. The Mission Creek and Winfield gold grain cores are surrounded by < 10 µm, Au-rich, Ag- and trace element-poor, rims. Lambly Creek grains lack such rims. The Au-rich rims on modern day Mission Creek and Miocene Winfield gold may reflect prolonged near-surface exposure with surficial electrochemical dissolution of hypogene trace elements or the biological precipitation of gold. Low Ag and red colouration on the surface of grains support the biological precipitation hypothesis. The shared trace element signature, together with the Au-rich rims indicate that modern day placer gold in Mission Creek was multiply reworked from Miocene paleoplacers similar to the Winfield occurrence as a result of uplift and erosion of rocks on the east side of Okanagan Fault.

3D printed PLGA/MgO/PDA composite scaffold by low-temperature deposition manufacturing for bone tissue engineering applications

IntroductionBones are easily damaged. Biomimetic scaffolds are involved in tissue engineering. This study explored polydopamine (PDA)-coated poly lactic-co-glycolic acid (PLGA)-magnesium oxide (MgO) scaffold properties and its effects on bone marrow mesenchymal stem cells (BMSCs) osteogenic differentiation. MethodsPLGA/MgO scaffolds were prepared by low-temperature 3D printing technology and PDA coatings were prepared by immersion method. Scaffold structure was observed by scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS), fourier transform infrared spectrometer (FTIR). Scaffold hydrophilicity, compressive/elastic modulus, and degradation rates were analyzed by water contact angle measurement, mechanical tests, and simulated-body fluid immersion. Rat BMSCs were cultured in scaffold extract. Cell activity on days 1, 3, and 7 was detected by MTT. Cells were induced by osteogenic differentiation, followed by evaluation of alkaline phosphatase (ALP) activity on days 3, 7, and 14 of induction and Osteocalcin, Osteocalcin, and Collagen I expressions. ResultsThe prepared PLGA/MgO scaffolds had dense microparticles. With the increase of MgO contents, the hydrophilicity was enhanced, scaffold degradation rate was accelerated, magnesium ion release rate and scaffold extract pH value were increased, and cytotoxicity was less when magnesium mass ratio was less than 10%. Compared with other scaffolds, compressive and elastic modulus of PLGA/MgO (10%) scaffolds were increased; BMSCs incubated with PLGA/MgO (10%) scaffold extract had higher ALP activity and Osteocalcin, Osteopontin, and Collagen I expressions. PDA coating was prepared in PLGA/MgO (10%) scaffolds and the mechanical properties were not affected. PLGA/MgO (10%)/PDA scaffolds had better hydrophilicity and biocompatibility and promoted BMSC osteogenic differentiation. ConclusionLow-temperature 3D printing PLGA/MgO (10%)/PDA scaffolds had good hydrophilicity and biocompatibility, and were conducive to BMSC osteogenic differentiation.

Deep insight into reactive chemical structures of Class F fly ash

Reactive amorphous aluminum silicates dominate the reactivity of fly ash in alkali cement; however, the quantitative characterization of valid chemical compositions and structures information is highly challenging due to the heterogeneity and complexity of these phases. To acquire this information, in this work, Class F fly ash was treated with 1% hydrofluoric acid, followed by step-by-step analysis using a scanning electron microscope with an energy dispersive spectrometer (SEM-EDS), solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR), and Fourier transform infrared (FT-IR) spectroscopy. Based on the acidolysis method, along with SEM-EDS statistical analysis, four amorphous aluminum silicate phases with relatively higher reactivity were successfully separated and quantitatively showcased, along with their respective average atomic percentage compositions (i.e., Si, Al, Ca, Fe, Na, K, and Mg%). In addition, the use of MAS-NMR and FT-IR analyses allowed for further quantitative insight into the reactive chemical structures and their associations with reactivity. The proposed characterization techniques have unique advantages for acquiring detailed reactive amorphous chemistries, which are difficult to obtain using conventional analysis procedures in alkali systems.

Sorption properties of groundwater treatment residuals containing iron oxides

Drinking water treatment produces groundwater treatment residuals (GWTRs), which can be used as mineral sorbents. GWTRs, sometimes referred to as water treatment sludge or waterworks sludge, are by-products produced by drinking water treatment plants. Their disposal is problematic and costly due to environmental constraints and has provided the impetus for research into their reuse as mineral sorbents. The main constituents of the sludge are iron and manganese oxyhydroxides, with calcium carbonate and detrital quartz (Q) in minor amounts. In this study, we investigated the sorption capacity of GWTRs toward Cd(II), Cu(II), Pb(II), Zn(II), and Cr(III), determining the effects of contact time, temperature, initial metal concentration, and pH on metal sorption efficiency. GTWRs are very effective metal sorbents, sorbing from tens to up to 230 g of metal/kg of sorbent, depending on the metal. Optimal conditions for sorption are pH 5–8, a reaction time of 4–5 h, and temperature 298 K. Investigations of the material after sorption by X-ray diffraction (XRD), infrared spectroscopy (FTIR), photoelectron spectroscopy (XPS), scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS) have provided insight into the nature of the interaction of metals with GWTRs and described the reaction mechanism. Metals are removed from the solution through the processes of inner-sphere adsorption on the surface of the precipitate, coprecipitation with iron compounds and incorporation into the ferrihydrite (Fh) structure or precipitation in the form of their mineral phases, such as carbonates, metal oxides or hydroxides. The results obtained from the experiments show that GWTRs effectively remove metal cations from aqueous solutions and can be used as sorbents for pollutants from wastewater or liquid industrial waste. The next step should be to test the ability against anionic forms of metals and organic compounds.

Multistage Gold Mineralization at The Wanagon Gold Prospect, Ertsberg District, Mimika Regency, Papua Province, Indonesia

DOI:10.17014/ijog.9.3.279-290The Wanagon Gold prospect area located in the Ertsberg District, Papua Province, the eastern part of Indonesia, is predominantly underlain by Upper Mesozoic to Cenozoic sedimentary rocks intruded by the Wanagon Sill monzodiorite-diorite and andesite intrusion (Wanagon Dike). The study by previous researchers at Wanagon Gold prospect was based on pre-2005 exploration data and did not contain extensive additional drillings in 2007-2011. This paper aims to elucidate the genesis of the Wanagon Gold deposits based on the latest exploration data. The mineralogy was determined by using thin section and polish section analyses, a scanning electron microscope with an energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), and Near-Infrared spectroscopy (NIR). The chemical composition of the rock was identified using an X-ray fluorescence spectrometer (XRF). Gold mineralization is associated with pyrite, of which there are three types of gold-bearing pyrite: (1) massive pyrite, (2) disseminated pyrite, and (3) fine-grained pyrite associated with clay minerals. Only massive pyrite contains visible gold-bearing minerals such as native gold, electrum, and gold-telluride minerals, while in nonmassive pyrite, gold is only detected by the assay. The deposit is interpreted as structurally controlled distal gold skarn. Instead, its local association of gold with arsenic also indicates a minor component of more-distal sediment-hosted type gold mineralization.

Effect of Fe2O3 on the crystallization behavior, microstructure and properties of glass-ceramics prepared from the modified tailings after reduction of copper slag

The modified tailings containing Fe2O3 after reduction of copper slag were used as the raw materials for the preparation of gehlenite-based glass-ceramics. The effect of Fe2O3 content on the crystallization behavior, microstructure and mechanical properties of glass-ceramics were investigated by Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS). The results show that when the Fe2O3 content increases from 0 wt% to 4 wt%, the crystallization peak temperature of base glass decreases and the crystallization activation energy of base glass decreases firstly and then increases. The minimum crystallization activation energy is 237.71 kJ/mol when the Fe2O3 content in base glass is 1 wt%, resulting from the highest content of glass modifier [FeO6]-octahedral in the glass. The crystallization index indicates that the crystallization method of base glass is surface crystallization, irrespective of the Fe2O3 contents of the base glass. Although the crystallization rate is slow resulting from the limited crystallization sites provided by Fe2O3, the glass-ceramics with 2 wt% Fe2O3 has a good comprehensive performance. When the nucleation process is at 850 ℃ for 120 min and the crystallization process is at 980 ℃ for 120 min, the flexural strength, microhardness, volume density and water absorption of the glass-ceramics with 2 wt% Fe2O3 are 138.26 MPa, 872.19 HV, 2.81 g/cm3 and 0.16%, respectively.

Removal of Aqueous Cu2+ by Amorphous Calcium Carbonate: Efficiency and Mechanism

Crystalline calcium carbonate (CaCO3, such as calcite) could scavenge aqueous metals via adsorption and coprecipitation. As a precursor to crystalline CaCO3, amorphous calcium carbonate (ACC) is poorly understood on metals removal. Herein, we synthesized silica-stabilized ACC and investigated its Cu2+ removal efficiency and mechanism. The results showed that the Cu2+ removal efficiency by ACC is controlled by the initial solution pH, initial Cu2+ concentration, contacting time, and ACC dosage. The maximum Cu2+ removal capacity was 543.4 mg/g at an ACC dosage of 1 g/L, an initial pH of 5.0, an initial Cu2+ concentration of 1000 mg/L, and an equilibrium time of 20 h. X-ray powder diffraction (XRD) and scanning electron microscope with an energy dispersive spectrometer (SEM-EDS) revealed that Cu2+ precipitated as paratacamite (Cu2(OH)3Cl, space group: R3¯) at an ACC dosage of 1 g/L, whereas botallackite (Cu2(OH)3Cl, space group: P21/m) was the Cu-bearing product for crystalline calcite using the same dosage as ACC. However, Cu2+ preferred to incorporate into calcite, which is transformed from ACC at high ACC loading (such as 4 g/L). Our results demonstrated that the crystallinity and dosage of CaCO3 could control the Cu2+ removal mechanism.

Tracking silver in the Lappberget Zn-Pb-Ag-(Cu-Au) deposit, Garpenberg mine, Sweden: Towards a geometallurgical approach

The complex mineralogy and low concentration of silver in polymetallic ores makes mineralogical characterization and extraction challenging. In this study, quantified mineralogical characterization of the flotation products from batch flotation tests was undertaken for a silver-rich zinc-lead ore using QEMSCAN® (Quantitative Evaluation of Minerals by Scanning Electron Microscope), scanning electron microscope with an energy dispersive spectrometer (SEM-EDS), and electron probe microanalysis (EPMA). Ten major silver minerals were identified and their behavior during flotation was discussed based on their different mineralogical and textural characteristics. Results from this study also showed the variability in the composition of some silver minerals (e.g., tetrahedrite and electrum), the presence of structurally bound silver in galena, and the formation of sulfur-based silver coating on chalcopyrite, galena, and tetrahedrite. A metallurgical balance generated using the QEMSCAN® data shows a very strong linear correlation (R2 = 0.99) against the chemical assay derived using inductively coupled plasma mass spectrometry (ICP-MS). This suggests that the quantification of mineralogical data produced using automated mineralogy is possible even for tracking trace minerals. The effectiveness of this methodology lies upon the creation of a robust mineral library based on a comprehensive mineralogical study, which can be used for tracking of by-product metals during the flotation of complex ores.

Comparative Study of Thermal-Oxidative Aging and Salt Solution Aging on Bitumen Performance.

The aging of bitumen is detrimental to the durability and service life of asphalt pavement. Previous studies found that bitumen was suspected to be aged by not only thermal oxidation but also solution immersion. This research aims to compare the effect of thermal-oxidative aging and salt solution aging on bitumen performance. For this purpose, a thin film oven test (TFOT) and pressure aging vessel aging (PAV) were selected as thermal-oxidative aging, and 10% NaCl aging and 10% CaCl2 aging were selected as salt solution aging. The morphology, oxygen content, physical properties, low-temperature properties, and high-temperature properties of bitumen were analysed by employing scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS), physical tests, a bending beam rheometer (BBR), and a dynamic shear rheometer (DSR). Test results show that both thermal-oxidative aging and salt solution aging had similar influencing trends in the oxygen content, physical, low-temperature, and high-temperature properties of bitumen but had different changes in morphology. The aging degrees caused by four kinds of aging methods were obtained based on the summed values of the absolute aging factor of all parameters: PAV > 10% NaCl > TFOT > 10% CaCl2. The conclusions could provide a theoretical basis to establish a standard for the solution aging of bitumen.

Characterization of Fe5(AsO3)3Cl2(OH)4·5H2O, a new ferric arsenite hydroxychloride precipitated from FeCl3–As2O3–HCl solutions relevant to arsenic immobilization

Tooeleite (Fe6(AsO3)4SO4(OH)4·4H2O) is widely precipitated for direct As(III) removal from sulfate-rich industrial effluents. However, whether or not Fe(III)–As(III)–Cl(-I) precipitate is produced in chloridizing leaching media for As immobilization is almost unknown. This work founded the existence of ferric arsenite (hydroxy)chloride as a new mineral for As(III) removal. Its chemical composition and solid characterization were subsequently studied by using scanning electron microscope with an energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), infrared (FT-IR), Raman spectroscopy and thermogravimetric (TG) curve. The results showed the formation of a yellow precipitate after 3-days reaction of Fe(III)/As(III) with molar ratio ≈ 1.7 in chloride solution at pH 2.3 neutralized with NaOH. Compared with tooeleite, chemical analysis and solid characterization indicated that Cl(-I) replaces SO4(-II) producing ferric arsenite hydroxychloride with formula Fe5(AsO3)3Cl2(OH)4·5H2O. This new plate shaped solid showed better crytallinity than tooeleite, although it has similar morphology and characteristic bands to tooeleite. The FT-IR bands at 628, 964 cm−1 and the Raman bands at 448, 610, 961 cm−1 were assigned to Fe–O or As(III)–O–Fe or As(III)–O bending/stretching vibration, indicating that both arsenite and chloride substituted for the position of sulfate for ferric arsenite hydroxychloride produced due to the lack of the SO42− vibrations. Cl-(I) also contributed to increase As removal efficiency in aqueous sulfate media under acidic pH conditions via the probable formation of sulfate-chloride ferric arsenite.

Study on Friction Behavior of Ferroalloy and Wet Granulation Sulfur under Low Normal Load Conditions

To study the friction behavior of ferroalloy and wet granulation sulfur under low normal load conditions, a series of experiments were performed using a homemade rotating test apparatus. Scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD) were utilized to examine the friction products. The experimentally monitored friction coefficient data were used to develop a finite element model to simulate the temperature field and a theoretical model to calculate the flash temperature of the contact area of the friction surface. The experimental, simulation, and theoretical results showed that the flash temperature of the friction surface is much higher than the average temperature of the friction surface and allows the reaction of iron and sulfur to form iron–sulfide compounds.

Mineraloška in geokemična karakterizacija rimske žlindre z arheološkega najdišča pri Mošnjah (Slovenija)

Roman slag from the archaeological site near Mosnje (NW Slovenia) was studied with respect to its mineralogical and geochemical characteristics. Samples were analysed with light microscopy, X-ray powder diffraction (XRD), scanning electron microscopy with an energy dispersive spectrometer (SEM-EDS) and Raman microspectroscopy. A chemical investigation was carried out using inductively coupled plasma-atomic emission spectroscopy (ICP-ES) to determine the major elements. The investigated slags are recognized as iron slags, grouped into two main classes according to their chemical and mineralogical compositions. The first group is characterized by high Fe2O3 and low SiO2 contents and the second by high CaO and SiO2 and low Fe2O3 contents. The phase occurrence obviously depends on the chemical composition as the first group mainly consists of fayalite, wustite and magnetite, and the second one of augite, leucite, hedenbergite, monticellite and kirschsteinite.

Temporal variation of PM10 and metal concentrations in Tampico, Mexico

Concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V, and Zn in particulate matter (PM)10 ambient air samples were determined for the urban zone of Tampico, Mexico every 6 days during 2004. A Wedding and Associates PM10 high-volume sampler was used to collect the particles on quartz and glass fiber filters. A Thermo Jarrel Ash inductively coupled plasma-optical emission spectrometer (ICP-OES) was used to identify and quantify metals in PM10 according to the USEPA-IO 3.1 method. A scanning electron microscope with an energy dispersive spectrometer (SEM-EDS) was used to analyze the elemental composition, size, and morphology of atmospheric particles. Principal component factor analysis (PCFA) was used to study the sources of PM10 and metals. PM10 and Pb concentrations in Tampico did not exceed the Mexican standard value of 120 and 1.5 μg m−3 in 24 h, respectively. PM10 concentrations ranged from 12 to 47 μg m−3. The results for Cd, Cr, and Cu are associated to the presence of an industrial source near the sampling site. V and Zn and likely Pb and Ni are related to a refinery. Fe and Ti are associated to natural sources, whereas Cu, Fe, Ni, Pb, and Zn are associated to the storage and transportation of minerals near the sampling zone. Mn is associated to a ferromanganese manufacturing industry and to the refinery. The SEM-EDS micrographs show porous spherical particles rich in V and Ni and smooth spherical particles rich in C and O.

Mn(IV) promotion mechanism for the photocatalytic oxidation of arsenite by anatase-TiO2

Abstract A Ti–Mn hybrid oxide (Ti–Mn–HO) that simultaneously contained anatase-TiO 2 and Mn 3 O 4 was prepared and applied to arsenite photocatalytic oxidization (PCO) under UV irradiation. X-ray diffraction (XRD), scanning electron microscopy with an energy dispersive spectrometer (SEM/EDS), transmission electron microscopy (TEM) and a N 2 adsorption–desorption method were employed to characterize the morphology of the catalyst. Kinetics experiments indicated that Mn 3 O 4 promoted the PCO-adsorption process of arsenite [As(III)] better than either pure anatase-TiO 2 under UV irradiation or Ti–Mn–HO without UV exposure. The cause of this phenomenon was investigated using Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). Finally, a synergistic effect for the transformation of photoproduct holes and electrons between the TiO 2 and Mn 3 O 4 phases is assumed.

REDWARES FROM GUBBACKA’S MEDIEVAL VILLAGE: REGIONAL AND INTER-REGIONAL VIEWS ON CERAMIC NETWORKS AND TECHNOLOGY (SEM-EDS)

The medieval village site of Gubbacka is situated in the today’s Vantaa, Finland. Archaeological investigations were conducted at the site in 2002–2003 and 2008–2010. The aim of this paper is to explore the social and trade contacts and networks the rural inhabitants of Gubbacka had within the Baltic Sea region. In order to examine how these relationships are reflected in the ceramic materials from the site, redware sherds were sampled for micro-structural and compositional characterization by a scanning electron microscope with an energy dispersive spectrometer (SEM-EDS) to study their provenance and technological properties. In addition, redwares from a nearby site Mankby and Tallinn were included in this study as regional and inter-regional parallels to examine possible shared origins of the pots and technological applications in redware manufacture. Redware is a very common archaeological find material in late medieval contexts, but rather difficult to investigate: the products of the different north European manufacturing centres are practically impossible to distinguish with the naked eye, and even the dating of redware finds is problematic. Hence, this study aims to offer new perspectives for the study of redwares, their technologies and distribution networks in northern Europe.

Tin amalgam mirrors: investigation by XRF, SEM-EDS, XRD and EPMA-WDS mapping

Ancient mirrors were constituted by a tin-mercury amalgam layer superimposed to a glass sheet. This was the only one method used until the nineteenth century, when the wet silvering process was invented. The tin amalgam is a binary alloy of tin and mercury constituted by two different phases: a mercury-rich liquid phase and a tin-rich solid phase. The amalgam alteration produces mercury loss and a general growth of the solid crystalline phase. In addition, tin dioxide and monoxide are formed with a consequent decrease of the amalgam adhesion to the glass. These degradation phenomena led to reduction or disappearance of the mirror reflective power. The aim of this study was the characterization of the amalgam layers of eight mirror samples dating during the seventeenth and nineteenth centuries. The samples were analyzed by X-ray diffraction and by a Scanning Electron Microscope with an Energy Dispersive Spectrometer (SEM-EDS), and for the first time on this type of alloy by X-ray Fluorescence and EPMA-WDS (Electron Probe Micro Analysis with Wavelength Dispersive Spectrometry) elemental mapping. The contents of tin, mercury, and some trace elements in the amalgam layers have been determined. The investigation of the superficial patterns of the amalgam by SEM, EPMA-WDS mapping, and SEM-EDS allowed a first understanding of some morphologies and processes of the degradation of the amalgam layer.

The effect of steel balls based on different standards on the anti‐wear properties of lubricants

PurposeThrough practical tests, it has been found that steel balls based on different standards could affect tribological performances of the same lubricant, but unfortunately, past researches in the field have been quite inadequate. The aim of this paper, therefore, is conscientiously to study the problem.Design/methodology/approachThe anti‐wear properties of four kinds of lubricants were evaluated by four‐ball tester using two kinds of steel balls based on different standards. The reason for different anti‐wear properties of the same lubricant was also discussed using hardness tester and scanning electron microscope with an energy dispersive spectrometer (SEM/EDS).FindingsIt was found that steel balls based on different standards could affect the tribological results for the same lubricant. The reason could lie in the surface chemical composition, surface roughness and hardness of steel balls which originated from the subtle difference of different standards.Originality/valueThe paper shows that, as far as evaluating anti‐wear properties is concerned, steel ball based on AISI Standard Steel No. E‐52100 is a better choice than that based on Chinese standard GB 308.

Power generation from a biocathode microbial fuel cell biocatalyzed by ferro/manganese-oxidizing bacteria

The abiotic cathodes usually require a catalyst such as Pt to enhance power production, increasing the cost and lowering the operational sustainability. In this paper, the performance of a biocathode microbial fuel cell biocatalyzed by ferro/manganese-oxidizing bacteria was investigated. A scanning electron microscopy with an energy-dispersive spectrometer (SEM-EDS) was used to characterize the cathode and analyze the element of cathode. The amount of ferro/manganese-oxidizing bacteria in the biocathode was examined. In batch-fed systems, the maximum open circuit voltage (OCV) was between 700 and 800 mV and the maximum cell potential difference was higher than 600 mV with an external resistance of 100 Ω. The maximum power density was 32 W m −3 MFC for batch-fed systems (20–40% Coulombic yield) and 28 W m −3 MFC for a continuous system with an acetate loading rate of 1.0 kg COD m −3 day −1. The results of SEM-EDS clearly showed that cathode was impregnated with iron and manganese. The amount of ferro/manganese-oxidizing bacteria was (7.5–20.0) × 10 5 MPN mL −1 in the biocathode. Biocathodes alleviate the need to use noble catalysts for the reduction of oxygen, which step forward towards large-scale application of MFCs.

Nucleation and growth of needle-like fluorapatite crystals in bioactive glass–ceramics

The nucleation behaviors of glass–ceramics with different Ca–mica (Ca 0.5Mg 3AlSi 3O 10F 2)/fluorapatite ratios were investigated. By using differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscope with an energy dispersive spectrometer (SEM/EDS), the effect of CaO and P 2O 5 addition on the nucleation behaviors was studied. Results showed that the addition of CaO and P 2O 5 promoted nucleation process and led to the formation of different nucleation phases. After further heat treatment, Ca 5(PO 4) 3F crystals were of needle-like morphology, instead of particle-like reported in previous studies. This can be attributed to the one-dimensional rapid growth of fluorapatite along the c-axis. The values of the Avrami parameter, n, and the dimensionality of crystal growth, m, are found to be 2 and 1, respectively, which indicated that the bulk nucleation is the dominant mechanism in crystallization, and one-dimensional growth of fluorapatite is preferred. Since needle-like fluorapatite crystals are of the same morphology to hydroxyapatites in human bones, the glass–ceramics thus prepared show excellent bioactivity in vivo.

Preparation of mica-based glass-ceramics with needle-like fluorapatite

Objectives The aim of this study was to prepare mica-based glass-ceramics containing needle-like fluorapatites, and to understand the relationship between the composition, the microstructure and mechanical properties. Methods The specimens were prepared by casting and subsequent heat treatment. The crystalline phases in the specimens were determined by X-ray diffraction (XRD). The microstructures of the fractured surface were examined by using a scanning electron microscope with an energy dispersive spectrometer (SEM/EDS). The Vickers hardness and fracture toughness were determined by the indentation method. Statistical analysis of the results was performed by one-way analysis of variance (ANOVA) and Tukey's test. The bioactivity of the glass-ceramics was evaluated by soaking the polished specimens in the simulated body fluid (SBF). Results Needle-like fluorapatite crystals were successfully obtained in mica-based glass-ceramics by controlling the heat treatment process. The formation of needle-like fluorapatite crystals, instead of particle-like crystals reported in previous studies, can be attributed to the one-dimensional rapid growth of fluorapatite along the c-axis. The mechanical properties of the glass-ceramics are related to the fluorapatite content. The higher the fluorapatite content, the higher the Vickers hardness and the fracture toughness ( p < 0.01). The bioactivity test showed that the needle-like fluorapatite-containing glass-ceramics possess very good bioactivity. Significance As the needle-like fluorapatite crystal has the same morphology as human bones, it endows the mica-based glass-ceramics with good bioactivity. Moreover, the needle-like fluorapatite crystal toughens the base glass-ceramics. Therefore, the mica-based glass-ceramics with needle-like fluorapatite have the potential for the restoration of bone defects and implants.