Interface processes between iron containing aluminosilicate systems and simulated body fluid enriched with protein

The behaviour of iron containing aluminosilicate samples in Kokubo’s simulated body fluid (SBF) and in SBF enriched with bovine serum albumin (BSA) has been investigated. Crystalline samples of (80–x)SiO₂·20Al₂O₃·xFe₂O₃ system, with x = 5, 10 or 15 mol%, obtained by sol–gel method and heat treated at 1200°C in air for 24 h. Data on electrical conductivity, calcium, phosphorous and potassium concentrations in simulated body fluids after samples soaking in static regime at 37°C, for several periods up to 14 days, were used to estimate the dynamics of these cations on the interface of aluminosilicate samples with SBF, and with SBF containing BSA. The UV-visible and fluorescence spectra recorded from the simulated body fluids after immersion of the investigated aluminosilicate samples evidence changes function on immersion time and Fe₂O₃ content.     

A study of the formation of amorphous calcium phosphate and hydroxyapatite on melt quenched Bioglass® using surface sensitive shallow angle X-ray diffraction

Melt quenched silicate glasses containing calcium, phosphorous and alkali metals have the ability to promote bone regeneration and to fuse to living bone. These glasses, including 45S5 Bioglass^® [(CaO)_26.9(Na₂O)_24.4(SiO₂)_46.1(P₂O₅)_2.6], are routinely used as clinical implants. Consequently there have been numerous studies on the structure of these glasses using conventional diffraction techniques. These studies have provided important information on the atomic structure of Bioglass^® but are of course intrinsically limited in the sense that they probe the bulk material and cannot be as sensitive to thin layers of near-surface dissolution/growth. The present study therefore uses surface sensitive shallow angle X-ray diffraction to study the formation of amorphous calcium phosphate and hydroxyapatite on Bioglass^® samples, pre-reacted in simulated body fluid (SBF). Unreacted Bioglass^® is dominated by a broad amorphous feature around 2.2 Å^?1 which is characteristic of sodium calcium silicate glass. After reacting Bioglass^® in SBF a second broad amorphous feature evolves ~1.6 Å^?1 which is attributed to amorphous calcium phosphate. This feature is evident for samples after only 4 h reacting in SBF and by 8 h the amorphous feature becomes comparable in magnitude to the background signal of the bulk Bioglass^®. Bragg peaks characteristic of hydroxyapatite form after 1–3 days of reacting in SBF.     

Surface modification of zirconium by anodisation as material for permanent implants: in vitro and in vivo study

The potential use of anodised zirconium as permanent implant has been investigated. Zirconium was anodised at constant potential between 3 and 30 V in H₃PO₄. Electrochemical assays were conducted in simulated body fluid solution (SBF) in order to evaluate the effect of the surface oxide on the corrosion resistance in vitro after 30 days of immersion. The rupture potential increases when increasing thickness of the anodic surface film. The increase in the barrier effect when increasing anodising potential is also verified by EIS. Anodisation in H₃PO₄ proved to increase the apatite formation capability of zirconium in a single step. In vivo bone formation was also analysed by implanting the modified materials in Wistar rats. Anodised Zr presents higher corrosion resistance in SBF in all the studied immersion times when compared with non anodised Zr. Additionally, in vivo experiments evidence bone generation and growth in contact with zirconium implants both in the as-received and anodised condition.     

Conversion of melt-derived microfibrous borate (13-93B3) and silicate (45S5) bioactive glass in a simulated body fluid

Microfibrous bioactive glasses are showing a considerable capacity to heal soft tissue wounds, but little information is available on the mechanism of healing. In the present study, the conversion of microfibrous borate bioactive glass (diameter = 0.2–5 μm) with the composition designated 13-93B3 (5.5 Na₂O, 11.1 K₂O, 4.6 MgO, 18.5 CaO, 3.7 P₂O₅, 56.6 B₂O₃ wt%) was evaluated in vitro as a function of immersion time in a simulated body fluid (SBF) at 37 °C using structural and chemical techniques. Silicate 45S5glass microfibers (45 SiO₂, 24.5 Na₂O, 24.5 CaO, 6 P₂O₅ wt%) were also studied for comparison. Microfibrous 13-93B3 glass degraded almost completely and converted to a calcium phosphate material within 7–14 days in SBF, whereas >85 % of the silica remained in the 45S5 microfibers, forming a silica gel phase. An amorphous calcium phosphate (ACP) product that formed on the 13-93B3 microfibers crystallized at a slower rate to hydroxyapatite (HA) when compared to the ACP that formed on the 45S5 fibers. For immersion times >3 days, the 13-93B3 fibers released a higher concentration of Ca into the SBF than the 45S5 fibers. The fast and more complete degradation, slow crystallization of the ACP product, and higher concentration of dissolved Ca in SBF could contribute to the capacity of the microfibrous borate 13-93B3 glass to heal soft tissue wounds.     

Fretting wear behavior of calcium phosphate-mullite composites in dry and albumin-containing simulated body fluid conditions

In a recent work, it has been shown that it is possible to achieve a better combination of compressive strength, flexural strength and toughness properties in calcium phosphate (CaP) composites containing 20 and 30 wt% mullite (3Al₂O₃·2SiO₂). In view of their potential application as load bearing implants, the present work reports the friction and wear properties of the newly developed composites against zirconia under dry ambient as well as in simulated body fluid (SBF) containing bovine serum albumin (BSA) protein. For comparison, experiments were also conducted on monolithic hydroxyapatite (HAp, Ca₁₀(PO₄)₆(OH)₂) and mullite under identical conditions. Under the investigated fretting conditions, the mullite-containing composites exhibited higher coefficient of friction (COF) of 0.4–0.6, compared to pure HAp (COF ~ 0.25–0.3). Although the wear resistance of the composites containing 20 or 30 wt% mullite was better in dry conditions, higher wear rate was measured in SBF conditions. The difference in tribological properties has been analyzed in reference to the difference in phase assemblage and mechanical properties. A comparison with some competing biomaterials reveals good potential of the investigated CaP-mullite composites for application as wear resistant implants.     

Bioactivity potential of calcium alumino-silicate glasses and glass–ceramics containing nitrogen and fluorine

Calcium alumino-silicate glasses of general composition (in eq.%) 28Ca:57Si:15Al:[100 ? (x + y)]O:xN:yF (x = 0 or 20 and y = 0, 3 or 5) and their glass–ceramic counterparts were immersed in simulated body fluid (SBF) at 37 ± 0.5 °C for 28 days to assess their potential bioactivity. The glasses showed no Ca release or surface calcium phosphate deposition due to their high network connectivities (>2.55). The glass–ceramics all showed potential bioactivity, as the SBF became enriched in Ca and calcium phosphate deposits formed on their surfaces. This was a result of Ca release from crystalline phases (predominantly wollastonite in the case of CaSiAlOF glass–ceramics and gehlenite in the case of CaSiAlONF glass–ceramics). No aluminium was leached from the glass–ceramics into the SBF, due to its pH always exceeding 7.0.     

Prediction model of lifetime for copper pillar bumps under coupling effects of current and thermal cycling

Considering the current induced voids flow will accelerate the creep strain rate and lower the strength of the solder, a current induced activation energy change, ΔQ_e is added in the Anand model. A lifetime prediction model was constructed based on linear damage rule for the current-thermal cycling coupling test. To verify the accuracy of the model, mean-time-to-failure (MTTF) of copper pillar has been experimentally and analytically investigated under the combination of thermal cycling with temperature range of ?40 to 125 °C and a superimposed electric current with current densities of 17.4–22.4 × 10⁴ A/cm². The experimental results reveal that the MTTF sharply decreases with the increasing current density. The acceleration factors are calculated, which is consistent well with the prediction model.     

The effect of phosphate content on the bioactivity of soda-lime-phosphosilicate glasses

We report on the bioactivity of two series of glasses in the SiO₂–Na₂O–CaO–P₂O₅ system after immersion in simulated body fluid (SBF) after 21 days. The effect of P₂O₅ content was examined for compositions containing 0–9.25 mol.% phosphate. Both series of glasses degraded to basic pH, but the solutions tended towards to neutrality with increasing phosphate content; a result of the acidic phosphate buffering the effect of the alkali metal and alkaline earth ions on degradation. Bioactivity was assessed by the appearance of features in the X-ray diffraction (XRD) traces and Fourier transform infrared (FTIR) spectra consistent with crystalline hydroxyl-carbonate-apatite (HCAp): such as the appearance of the (002) Bragg reflection in XRD and splitting of the P–O stretching vibration around 550 cm^?1 in the FTIR respectively. All glasses formed HCAp in SBF over the time periods studied and the time for formation of this crystalline phase occurred more rapidly in both series as the phosphate contents were increased. For P₂O₅ content >3 mol.% both series exhibited highly crystalline apatite by 16 h immersion in SBF. This indicates that in the compositions studied, phosphate content is more important for bioactivity than network connectivity (NC) of the silicate phase and compositions showing rapid apatite formation are presented, superior to 45S5 Bioglass^® which was tested under identical conditions for comparison.     

Poly(D,L-lactide) (PDLLA) foams with TiO2 nanoparticles and PDLLA/TiO2-Bioglass® foam composites for tissue engineering scaffolds

Porous poly(D,L-lactide) PDLLA foams containing 0, 5 and 20 wt% of TiO₂ nanoparticles were fabricated and characterised. The addition of Bioglass^® particles was also studied in a composite containing 5 wt% of Bioglass^® particles and 20 wt% of TiO₂ nanoparticles. The microstructure of the four different foam types was characterised using scanning electron microscopy (SEM) and their mechanical properties assessed by quasi-static compression testing. The in vitro behaviour of the foams was studied in simulated body fluid (SBF) at three different time points: 3, 21 and 28 days. The degradation of the samples was characterised quantitatively by measuring the water absorption and weight loss as a function of immersion time in SBF. The bioactivity of the foams was characterised by observing hydroxyapatite (HA) formation after 21 days of immersion in SBF using SEM and confirmed with X-ray diffraction (XRD) analysis. It was found that the amount of HA was dependent on the distribution of TiO₂ nanoparticles and on the presence of Bioglass^® in the foam samples.     

Ferroelectric properties of pulsed laser deposited PZT (92/8) thin films

The effect of pulse amplitude on the ferroelectric and switching properties of pulsed laser deposited PZT (92/8) thin films has been studied. The structural analysis revealed that the films had a well crystallized perovskite phase without secondary phases. The atomic force microscopy has been employed to estimate the grain size and surface roughness of the film. A well-saturated P–E hysteresis loop was observed with average values of remnant polarization (P_r) ≈ 16.0 μC/cm², saturation polarization (P_s) ≈ 21.7 μC/cm² and coercive field ≈138 kV/cm. The P–E loops were very stable with frequency, confirming that the contribution of the leakage current and/or mobile free charges to the polarization is minimum. The polarization current exhibits the exponential dependence on the pulse amplitude and the leakage current seems to be governed by the hopping mechanism which is generally associated to structural defects.     

The Design and Tests of Battery Power Supply System for Pulsed Flat-Top Magnets in WHMFC

A capacitor bank power supply of 14.8 MJ is built in Wuhan National Pulsed High Magnetic Field Center (WHMFC). Another pulse generator power supply of 100 MJ/100 MVA is expected to be finished by the end of August, 2012. These power supplies can drive pulsed magnets with a magnetic field of 50 T to 80 T and a pulse duration of 15 ms to 1000 ms (Li et al. in IEEE Trans. Appl. Supercond. 18:596, 2008). In addition to that, a new battery bank power supply system is also designed. This system can output a maximum voltage of 1000 V, a maximum current of 40 kA and a pulse duration of 2 s to feed pulsed flat-top magnets of 40 T/2 s. This power supply consists of battery bank and its charger, thyristor DC switch and its forced commutation, DC breaker, control system, Crowbar, PWM controller and magnet. The battery bank uses 945 lead-acid batteries and its modular design makes it easy to modify the voltage and current of the power supply by changing the connections of the batteries based on the requirement of single-coil, double-coil and triple-coil magnets. The design and primary tests of the battery power supply system will be introduced in this paper (Schillig et al. in IEEE Trans. Appl. Supercond. 10:526, 2000).     

Influence of oxidizer to fuel ratio on structural and magnetic properties of Mn–Zn ferrite nanoparticles

Nanoparticles of Mn_0.5Zn_0.5Fe₂O₄ are prepared using sol–gel auto-combustion method with a view to understand the role of oxidizer to fuel ratio [OFR (? _e)]. The selected ratios are categorized as fuel lean (? _e > 1), stoichiometric (? _e = 1), and fuel rich (? _e < 1), composition. Thermal study using TG–DTA on the samples confirm the impact of fuel on the decomposition process for three OFRs. X-Ray diffraction study unravels the formation of cubic ferrite with an enhancement of particle size from 30 to 46 nm. Fourier transform infrared spectroscopic spectra reveal the presence of tetrahedral and octahedral sites in the cubic spinel matrix and shift in the corresponding frequencies. The magnetic hysteresis parameters measured using vibrating sample magnetometer help to understand the increase of magnetic properties when OFR decreases. The magnetic domains change from multi to pseudo single domain and interestingly different spin canting as OFR is varied.     

Surface modification of a Ti–7.5Mo alloy using NaOH treatment and Bioglass® coating

The objective of this study was to propose a surface modification for a low-modulus Ti–7.5Mo alloy to initiate the formation of hydroxyapatite (HA) during in vitro bioactivity tests in simulated body fluid (SBF). Specimens of commercially pure titanium (c.p. Ti) and Ti–7.5Mo were initially immersed in a 15 M NaOH solution at 60°C for 24 h, resulting in the formation of a porous network structure composed of sodium titanate (Na₂Ti₅O₁₁). Afterwards, bioactive Bioglass^® particles were deposited on the surface of NaOH-treated c.p. Ti and Ti–7.5Mo. The specimens were then immersed in SBF at 37°C for 1, 7 and 28 days, respectively. The apatite-forming ability of the NaOH-treated and Bioglass^®-coated Ti–7.5Mo was higher than that of the c.p. Ti under the same condition. The X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) results indicated that the deposited amounts of calcium phosphate were much greater for the surface-treated Ti–7.5Mo than for the c.p. Ti, a finding attributable to or correlated with the higher pH value of the SBF containing surface-treated Ti–7.5Mo. Moreover, in the surface-treated Ti–7.5Mo, the pH value of the SBF approached a peak of 7.66 on the first day. A combination of NaOH treatment and subsequent Bioglass^® coating was successfully used to initiate in vitro HA formation in the surface of the Ti–7.5Mo alloy.     

Techno-economic analysis of green hydrogen production from biogas autothermal reforming

The development and deployment of energy mix hydrogen production technologies, and the prospect of supplying “green” hydrogen to fuel-cell cars are expected to play significant roles in the near future. The sustainability of the process is a key enabler for a hydrogen-including economy. A techno-economic analysis of the BioRobur technology, which involves the green hydrogen production of 100 N m³ H₂/h (5.0 grade), has been performed in this study to provide a basis for comparison between the final cost of the hydrogen and the European target. Moreover, a technology for its eventual implementation has been addressed, in which the weakness and strengths have been identified by means of a SWOT analysis. The cost and supply analysis of this biogas-to-hydrogen production system, via autothermal reforming, indicates that municipal solid waste (MSW) is an important source of the low-cost supply of biogas-derived hydrogen. As far as the market potential is concerned, this analysis suggests that MSW can provide about 286,607 kg/day at 5 €/kg H₂ (delivery cost). Additionally, after 10 years of amortization, the final cost to produce 100 N m³/h of H₂ would be 2.5 €/kg, which is far lower than the European target for the cost of obtaining H₂ through biogas reforming, that is, 5 €/kg of H₂.     

Bioactivity of calcium phosphate coatings prepared by electrodeposition in a modified simulated body fluid

The purpose of this study was to investigate bioactivity of calcium phosphate coatings prepared by electrodeposition in a modified simulated body fluid (SBF). Calcium phosphates were electrodeposited on commercially pure titanium substrates in the modified SBF at 60 °C for 1 h maintaining the cathodic potentials of − 1.5 V, − 2 V, and − 2.5 V (vs. SCE). Subsequently, the calcium phosphate coatings were transformed into apatites during immersion in the SBF at 36.5 °C for 5 days. The apatites consisted of needle-shaped crystallites distributed irregularly with different grain sizes. As the coatings were electrodeposited at higher cathodic potential, the crystallite of the apatites got denser and the grain sizes of the apatites became bigger during subsequent immersion in the SBF. However, as the coatings were electrodeposited at higher cathodic potential, the coatings were transformed into apatites with lower crystallinity and the Ca/P atomic ratio of the apatites got higher than 1.67, that of stoichiometric hydroxyapatite, after subsequent immersion in the SBF. In addition, CO₃²⁻ ions contained in the modified SBF were incorporated in the calcium phosphate coating during electrodeposition and had an influence on transforming the calcium phosphate into bonelike apatite during subsequent immersion in the SBF showing that CO₃²⁻ incorporated in the apatites disturbed crystallization of the apatites. These results revealed that the coating electrodeposited at − 2.0 V (vs. SCE) in the modified SBF containing CO₃²⁻ ions was the most bioactive showing transformation into carbonate apatite similar to bone apatite.     

Preparation of yolk–shell Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@N-doped carbon nanocomposite particles as anode in lithium ion batteries

The yolk–shell-structured Fe₃O₄ nanocomposite particles (Fe₃O₄@Void@C–N NPs) with Fe₃O₄ as the yolk and N-doped carbon as the shell were prepared by using melamine formaldehyde resin as the N and C sources. When used as anode material for lithium ion battery, the yolk–shell structure could not only afford adequate void to accommodate the large volume change during charge/discharge process but also improve structural stability and electrical conductivity. The anode material demonstrated superior long-term and high-rate performance because of the novel structure and the N-doped carbon shell with mesopore. Thus, Fe₃O₄@Void@C–N NPs exhibited a high reversible capacity of 1530 mAh g^?1 after 300 cycles at a current density of 500 mA g^?1, which were approximately 1.5 and 6 times higher than Fe₃O₄@C–N NPs and pure Fe₃O₄ particles, respectively. Even at the higher current density of 2000 mA g^?1, the reversible capacity remained at 651 mAh g^?1 after 500 cycles.     

Production of methanol and organic carbonates for chemical sequestration of CO2 from an NGCC power plant

Global economic development anticipates a growth in demand of the energy sector whose supply in the coming decades will remain achieved by burning fossil fuels. The need to stabilize the CO₂ atmospheric concentration requires technologies for capturing and reutilization of this greenhouse gas. Such scenario motivates feasibility analysis of power generation with post-combustion capture of CO₂ from the flue gas associated with its transformation into chemical commodities. Specifically, the economic performance of an integrated NGCC with post-combustion capture and utilization is evaluated to balance aggregated revenues with energy penalty. The proposed CO₂ reutilization is the production of methanol (MeOH), organic carbonates—dimethyl carbonate (DMC) and ethylene carbonate (EC), and ethylene glycol (EG). The study uses CO₂ capture with MEA (monoethanolamine), including compression of the captured gas followed by its conversion to methanol and organic carbonates, and separation of products with recycle of reactants. Three scenarios were evaluated corresponding to the capture of 30, 50, and 80 % of the CO₂ present in the flue gas. The comparative analysis includes definition of design premises followed by synthesis of process flowsheet, process simulation in the three scenarios, with sizing of the main pieces of process equipments for economic analysis—capital and operational expenditures (CAPEX and OPEX). Results indicated economic feasibility for the three scenarios. Furthermore, energy and mass balances showed that the emissions from energy demand to drive reactions and separations surpasses the proposed sequestration of CO₂ by chemical utilization in the scenarios of 30 and 50 % of CO₂ capture from NGCC emissions. In reality, CO₂ accounting for cases 1 and 2 reveals a “carbon debt” while for case 3 a net positive abatement of CO₂ occurs which increases process revenue by 1.7 % and reduces ROI in 1 year.     

Antibacterial and bioactive calcium titanate layers formed on Ti metal and its alloys

An antibacterial and bioactive titanium (Ti)-based material was developed for use as a bone substitute under load-bearing conditions. As previously reported, Ti metal was successively subjected to NaOH, CaCl₂, heat, and water treatments to form a calcium-deficient calcium titanate layer on its surface. When placed in a simulated body fluid (SBF), this bioactive Ti formed an apatite layer on its surface and tightly bonded to bones in the body. To address concerns regarding deep infection during orthopedic surgery, Ag⁺ ions were incorporated on the surface of this bioactive Ti metal to impart antibacterial properties. Ti metal was first soaked in a 5 M NaOH solution to form a 1 μm-thick sodium hydrogen titanate layer on the surface and then in a 100 mM CaCl₂ solution to form a calcium hydrogen titanate layer via replacement of the Na⁺ ions with Ca²⁺ ions. The Ti material was subsequently heated at 600 °C for 1 h to transform the calcium hydrogen titanate into calcium titanate. This heat-treated titanium metal was then soaked in 0.01–10 mM AgNO₃ solutions at 80 °C for 24 h. As a result, 0.1–0.82 at.% Ag⁺ ions and a small amount of H₃O⁺ ions were incorporated into the surface calcium titanate layers. The resultant products formed apatite on their surface in an SBF, released 0.35–3.24 ppm Ag⁺ ion into the fetal bovine serum within 24 h, and exhibited a strong antibacterial effect against Staphylococcus aureus. These results suggest that the present Ti metals should exhibit strong antibacterial properties in the living body in addition to tightly bonding to the surrounding bone through the apatite layer that forms on their surfaces in the body.     

Effects of niobium content on electrical and mechanical properties of (Na0.85K0.15)0.5Bi0.5Ti(1-x)Nb x O3 thin films

(Na_0.85K_0.15)_0.5Bi_0.5Ti_(1-x)Nb _x O₃ (NKBT-N100x) thin films were deposited on Pt/Ti/SiO₂/Si(100) substrates by metal–organic decomposition method and annealed in oxygen atmosphere at 750 °C. The effects of niobium concentration on the microstructures, ferroelectric, piezoelectric, leakage current and mechanical properties of the NKBT-N100x (x = 0, 0.01, 0.03, 0.05) thin films have been investigated in detail. The NKBT-3N thin film has the largest remnant polarization (7 μC/cm²) and statistically averaged d _33eff (140 pm/V), the smallest leakage current, elasticity modulus (102.0 Gpa), hardness (5.1 Gpa) and residual stress (297.0 Mpa). The evaluation of residual stresses of these thin films will offer useful guidelines of safe working condition for their potential application in microelectromechanical system.     

New proposal for production of bioactive compounds by supercritical technology integrated to a sugarcane biorefinery

The construction of a supercritical fluid extraction (SFE) plant inside or in close proximity to a sugarcane biorefinery producing first and second generation ethanol demonstrated to be very promising, increasing the economic potential of the SFE process in up to 57 %, since the SFE plant could use directly the ethanol, CO₂, heat, and electricity already available, with lower prices. In this study, Brazilian ginseng roots were used as model bioactive compounds source and first the statistical influence of the extraction conditions including pressure (10–20 MPa), temperature (323–363 K), and CO₂/ethanol proportion ratio (90:10, 50:50, and 0:100 %, w/w) on the β-ecdysone content in the extracts was experimentally evaluated and compared with literature results. SFE process evaluated experimentally at the present study showed higher selective extraction for β-ecdysone from Brazilian ginseng roots, providing an extract with up to 2.16 times higher β-ecdysone than the results obtained in previous studies. Thermal integration of the SFE process diminished energy requirements of the process, resulting in a reduction of cold utility requirement of 87 % and a final electricity demand of 7.5 kWh/g of β-ecdysone in the extract. In a situation in which the Brazilian ginseng roots price was increased to 4.71 USD/g, only the SFE integrated with the biorefinery solution would be economically feasible. Finally, the selling of the ginseng roots leftover could be an interesting answer to increase the economical attractiveness of the integrated SFE process to the biorefinery.