Search

The current study reports on the relaxation behaviour of lithium silicate based glasses as probed by NMR spectroscopy. A total of four glass compositions were studied with the parent composition being 28Li2O-72SiO2, and added dopants of Al and B. All the compositions showed significant differences in the NMR spectra of both annealed and non-annealed glasses demonstrating the structural relaxation behaviour. We extended our binary statistical mechanical model to these complex compositions to study the relaxation behaviour. By the combined use of the extended statistical mechanical model and broken ergodicity, we shed light on the mechanism of structural relaxation as understood by NMR spectroscopy. We studied the crystallization behaviour of the glasses and reported on the variations of the residual glass composition changes in the crystallization fraction.

AC Popa,1,2 GE Stan,1 MA Husanu,1 I Mercioniu,1 LF Santos,3 HR Fernandes,4 JMF Ferreira4 1National Institute of Materials Physics, Măgurele, 2Army Centre for Medical Research, Bucharest, Romania; 3Centro de Química Estrutural, Instituto Superior Técnico (CQE-IST), University of Lisbon, Lisbon, 4Department of Materials and Ceramics Engineering, Centre for Research in Ceramics and Composite Materials (CICECO), University of Aveiro, Aveiro, Portugal Abstract: Synthetic physiological fluids are currently used as a first in vitro bioactivity assessment for bone grafts. Our understanding about the interactions taking place at the fluid–implant interface has evolved remarkably during the last decade, and does not comply with the traditional International Organization for Standardization/final draft International Standard 23317 protocol in purely inorganic simulated body fluid. The advances in our knowledge point to the need of a true paradigm shift toward testing physiological fluids with enhanced biomimicry and a better understanding of the materials’ structure-dissolution behavior. This will contribute to “upgrade” our vision of entire cascades of events taking place at the implant surfaces upon immersion in the testing media or after implantation. Starting from an osteoinductive bioglass composition with the ability to alleviate the oxidative stress, thin bioglass films with different degrees of polymerization were deposited onto titanium substrates. Their bio­mineralization activity in simulated body fluid and in a series of new inorganic–organic media with increasing biomimicry that more closely simulated the human intercellular environment was compared. A comprehensive range of advanced characterization tools (scanning electron microscopy; grazing-incidence X-ray diffraction; Fourier-transform infrared, micro-Raman, energy-dispersive, X-ray photoelectron, and surface-enhanced laser desorption/ionization time-of-flight mass spectroscopies; and cytocompatibility assays using mesenchymal stem cells) were used. The information gathered is very useful to biologists, biophysicists, clinicians, and material scientists with special interest in teaching and research. By combining all the analyses, we propose herein a step forward toward establishing an improved unified protocol for testing the bioactivity of implant materials. Keywords: biomaterials, bioglass, in vitro biomimetic assays, proteins

Epoxy Gel Casting (EGC) was recently coined to designate a setting mechanism based on the in situ polymerization of epoxy resins dissolved in the aqueous dispersion media of ceramic powder suspensions upon adding suitable amine-based crosslinking agents. The specific interactions between the surface of the powder particles and the processing additives are likely to determine different partitions of the crosslinking species, dissolved in the bulk solution, or adsorbed at the surface of the particles, and affect the EGC process. The present work aims at evaluating the influence of surface chemistry on the extent of the specific interactions at the solid/liquid interface and how it affects the polymerization kinetics and the properties of ceramic green bodies consolidated by EGC. Three different ceramic oxides (alumina, zirconia and fused silica) having similar particle size distributions were used. Stable colloidal suspensions with 45 vol.% solids were prepared by dispersing the powders in aqueous solutions containing a fixed amount of a common dispersant and various dissolved amounts of an epoxy resin. Zeta potential, theological measurements and calorimetry were used to assess the specific interactions and their effects on the consolidation kinetics upon adding a polyamine hardener, and on the final properties of consolidated parts. With the isoelectric point of the naked particle surface decreasing, there were noticeable decreases in gelation time, shrinkage, green density, and flexural strength of the green ceramic body's properties. An interaction model is proposed to explain the observed differences. The potential of EGC to consolidate ceramic microneedles cast in soft rubber moulds was demonstrated. (C) 2016 Elsevier Ltd. All rights reserved.

Heterogeneous ceramics made of cordierite (55-56 wt%), mullite (22-33 wt%) and alumina (23-11 wt%) were prepared by sintering non-standard raw materials containing corundum, talc, alpha-quartz, K-feldspar, kaolinite and mullite with small amounts of calcite, cristobalite and glass phases. The green specimens prepared by PVA assisted dry-pressing were sintered within the temperature range of 950-1500 degrees C for different dwelling times (2-8 h). The effects of sintering schedule on crystalline phase assemblage and thermomechanical properties were investigated. The sintered ceramics exhibited low coefficients of thermal expansion (CTE) (3.2-4.2 x 10(-6) degrees C-1), high flexural strength (90-120 MPa and high Young modulus (100 GPa). The specimens sintered at 1250 degrees C exhibited the best thermal shock resistance (Delta T similar to 350 degrees C). The thermal expansion coefficients and thermal shock resistance were studied using Schapery model, the modelling results implying the occurrence of non-negligible mechanical interactions between the phases in bulk. The dielectric properties characterized from room to high temperature (RT-HT, up to 600 degrees C) revealed: (i) noticeable effects of sintering schedule on dielectric constant (5-10) and dielectric loss factor (similar to 0.02-0.04); (ii) stable dielectric properties until the failure of the electrode material. The thermomechanical properties coupled with desirable dielectric properties make the materials suitable for high density integrated circuitry or high temperature low-dielectric materials engineering. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

The high alkali content bioactive glasses commonly used to regenerate bone in dental, orthopedic, and maxillofacial surgeries induce some cytotoxicity in surrounding tissues. The present study aims the ability of some alkali-free bioactive glasses compositions, recently developed by our research group, to stimulate human mesenchymal stem cells (hMSCs) differentiation into osteoblasts in comparison to 45S5 Bioglass® . The obtained results demonstrated that alkali-free bioactive glasses possess higher stimulating towards differentiation of hMSCs in comparison to the control 45S5 Bioglass® . The von Kossa assay demonstrated that all bioactive glasses studied were able to induce the appearance of calcium deposits even when the cells were cultured in DMEM, proving that these biomaterials per se induce hMSCs cell differentiation. It was also observed that in both cell culture medium used (DMEM, and osteogenesis differentiation medium) alkali-free bioactive glasses clearly induced the appearance of more calcium deposits than the 45S5 Bioglass® , indicating their greater ability to induce cell differentiation. In summary, these results indicate that alkali-free bioactive glasses are a safe and valid alternative to 45S5 Bioglass® . © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2360-2365, 2017.

In this work, X-ray diffraction analysis and optical properties of pure and Ba-doped ZnO nanoparticles prepared by the precipitation method were investigated. X-ray analysis was employed to evaluate the micro structural parameters of ZnO nanoparticles in terms of crystallite sizes and lattice strain by the Williamson-Hall method. The average crystallite size of Ba-doped ZnO nanoparticles estimated by the Williamson-Hall method varied as the doping concentration increased. The effect of Ba doping on the photoluminescence (PL) emission spectrum of ZnO was also investigated. The temperature dependence of the PL emissions was also studied, and it was found that at low temperature, the samples show stronger emissions than those at room temperature in both UV and visible regions. As a final point, the FT IR reflection spectrum along with Kramers-Kronig (K-K) method and classical dispersion theory was applied to obtain optical properties of the samples at low frequency infrared regime. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

The effects of three functional ions (yttrium Y3+, fluorine titanium Ti4+) on the glass forming ability, sintering, crystallization, and thermo-physical properties of glasses and glass-ceramics were studied in a diopside-calcium pyrophosphate (90% CaMgSi2O6-10% Ca2P2O7) system. Three different percentages (1, 3 and 5 wt%) for each additive were tested. The structural features of glasses were assessed through FT-IR (Fourier Transform infra -red spectroscopy) and Si-29 and P-31 NMR (nuclear magnetic resonance), showing that the silicate network in all the investigated glasses is predominantly coordinated in Q(2) (Si) units, while phosphorus tends to remain in the orthophosphate (Q) environment. All glasses exhibited fast rates of biomineralization, making them promising candidates for biomedical applications. The sintering and crystallization behaviours of the glass powders were studied by differential thermal analysis (DTA), while the coefficient of thermal expansion (CTE) was determined by dilatometry. Glass transition temperature (Tg) values of all doped glasses were lower than the parent glass, while CTE values decreased with initial addition (1 wt%), of dopants before exhibiting an increase with further addition. In Y-doped glasses, a gradual increase was seen in the values of maximum crystallization peak temperature, Tp, up to 3 wt%, while an opposite trend was observed in Ti-doped glasses, showing an enhancement of the stability of the Y-doped glasses against devitrification. F-doped glasses exhibited a similar trend. Crystalline phase evolution was analysed by X-ray diffraction (XRD), and amorphous glass were obtained by sintering powder compacts from all the glasses at 800 degrees C for 1 h. (C) 2016 Elsevier B.V. All rights reserved.

Injectable bioglass (BG) pastes were produced using a melt-quenched glass based on CaO–MgO–SiO2–Na2O–P2O5–CaF2 and two organic carriers, namely polyethylene glycol (PEG) and glycerol (Gly). The interactions between the organic carriers and the surface of the BG particles were assessed by spectroscopic methods (Fourier Transform Infrared, Raman, as well as 29Si and 13C solid-state NMR spectroscopy) in order to understand their effects on the viscoelastic properties of the biocomposites. While pure physical interactions were detected between PEG and the surface of the BG particles, chemical bonding was observed between glycerol and BG, enhancing the network cross-linking degree. Accordingly, the BG network of Gly-BG pastes was more condensed (higher fraction of Q [3] units detected by Raman spectroscopy) in comparison to that of PEG-BG and bare BG. Such chemical interactions between the organic carrier and BG were shown to negatively affect the viscoelastic behaviour of the resulting pastes. Thus, the PEG-based biocomposite exhibited improved flowability in comparison to its analogous Gly-BG biocomposite. Keywords: Injectable biocomposites, Bioglass, PEG, Glycerol, Pastes

In this work, we purposefully reported a simple yet efficient carbothermal synthesis strategy to prepare micro-scale spherical AlN granules just by using CaF2 as promoting additive. The effects of synthesis parameters, such as CaF2 content, N-2 gas pressure, reaction temperature, upon the nitridation rate, surface morphology and particle size were comprehensively investigated. It was established that elevated N-2 gas pressure, high reaction temperature and abundant Ca-aluminates liquid synergistically promoted the formation of micro-scale spherical AlN granules. Additionally, the reduction and nitridation of intermediate Ca-aluminates played a significant role in improving the nitridation rate, increasing the particle size and forming the smooth spherical appearance. More significantly, the underlying reaction mechanism in the carbothermal synthesis of spherical AlN with CaF2 additive was also tentatively proposed. (C) 2015 Elsevier B.V. All rights reserved.

Silica-based bioactive glasses (SBG) hold great promise as bio-functional coatings of metallic endo-osseous implants, due to their osteoproductive potential, and, in the case of designed formulations, suitable mechanical properties and antibacterial efficacy. In the framework of this study, the FastOs&reg, BG alkali-free SBG system (mol%: SiO2&mdash, 38.49, CaO&mdash, 36.07, P2O5&mdash, 5.61, MgO&mdash, 19.24, CaF2&mdash, 0.59), with CuO (2 mol%) and Ga2O3 (3 mol%) antimicrobial agents, partially substituting in the parent system CaO and MgO, respectively, was used as source material for the fabrication of intentionally silica-enriched implant-type thin coatings (~600 nm) onto titanium (Ti) substrates by radio-frequency magnetron sputtering. The physico-chemical and mechanical characteristics, as well as the in vitro preliminary cytocompatibility and antibacterial performance of an alkali-free silica-rich bio-active glass coating designs was further explored. The films were smooth (RRMS &lt, 1 nm) and hydrophilic (water contact angle of ~65&deg, ). The SBG coatings deposited from alkali-free copper-gallium co-doped FastOs&reg, BG-derived exhibited improved wear performance, with the coatings eliciting a bonding strength value of ~53 MPa, Lc3 critical load value of ~4.9 N, hardness of ~6.1 GPa and an elastic modulus of ~127 GPa. The Cu and Ga co-doped SBG layers had excellent cytocompatibility, while reducing after 24 h the Staphylococcus aureus bacterial development with 4 orders of magnitude with respect to the control situations (i.e., nutritive broth and Ti substrate). Thereby, such SBG constructs could pave the road towards high-performance bio-functional coatings with excellent mechanical properties and enhanced biological features (e.g., by coupling cytocompatibility with antimicrobial properties), which are in great demand nowadays.

Structural and optical properties of antimony-containing sodium borate glasses were studied and their ultrafast third-order nonlinear optical (NLO) properties have been evaluated using Z-scan measurements with femtosecond (fs) pulses (?150 fs, 80 MHz) at 750, 800, and 880 nm wavelengths. Glasses in the (mol ) 20Na 2 O-(80 - x)B 2 O 3 -xSb 2 O 3 (where x = 0, 10, 20, and 30) system have been fabricated via melt quench technique. The structural modifications were analyzed using the Raman and magic angle spinning (MAS)-nuclear magnetic resonance (NMR) ( 11 B MAS-NMR and 23 Na MAS-NMR) techniques. The optical absorption spectra revealed that the absorption edge was red-shifted, suggesting the decrease in band gap energy with increase of antimony content in the glasses. Raman scattering results revealed that the boroxol rings are depressed with the incorporation of Sb 2 O 3 for replacing B 2 O 3 . 11 B MAS-NMR results showed a progressive increase of B 4 units at the expense of B 3 units. The Raman and 11 B MAS-NMR results support the formation of Sb 5+ ions due to oxidation of Sb 3+ that played the role of charge compensation. 23 Na MAS-NMR spectra revealed a decreasing trend in the average of bond lengths of Na-O with increasing Sb 2 O 3 contents. This suggested that sodium changed its role from charge compensator to modifier cation. The antimony-containing glasses demonstrated a reverse saturable absorption in open-aperture Z-scan mode due to two-photon absorption, while closed-aperture Z-scan signatures depicted positive nonlinear refraction due to self-focusing effect. The NLO coefficients were found to increase with Sb 2 O 3 due to the increased nonbridging oxygens and also due to the hyperpolarizability of Sb 3+ and Sb 5+ ions. The observed NLO data clearly suggest that the investigated glasses are beneficial for optical limiting applications.

We show the influence of two functional ions (Cu2+ and La3+ ), incorporated into a quaternary (Si, Ca, Na, P) sol-gel derived bioactive glass system, on its particle size, cytotoxicity, and bioactivity. By doping the parent glass with the two ions in singular or combined forms, 15 doped glasses were prepared by a rapid sol-gel technique. The influence of the combined doping on the particle size and cell viability was successfully evaluated by the aid of signal-to-noise-ratio (S/N), using Taguchi analysis. This allowed us to analyze the complex interplay of effects between these ions, and the marked differences in biocompatibility between the three cell types studied. Cu addition had a significant effect on reducing the glass particle size, while both increased density. Cell viability was significantly improved for some doping combinations, demonstrating that while combined Cu-La doping was beneficial for biocompatibility with lymphoblasts, individual high-Cu or low-La doping was better with fibroblasts, and either high-Cu or low-La doping, or certain combined Cu-La combinations, were the optimum for osteoblasts. However, the bioactivity of doped samples was generally similar to that of the parent glass, although both La, and particularly Cu, did appear to aid dissolution of ions when immersed in SBF, act as glass modifiers, and encourage HAp crystallization. The results reveal that potential synergistic benefits can be obtained by combining the effects on the mean particle size, density, cytotoxicity, and bioactivity of the glasses. The greatly improved biocompatibility of some of the doped glasses makes them promising candidates for biomedical applications.

The present work aims at evaluating the potential gains derived from partially replacing calcium in resorbable &beta, tricalcium phosphate (&beta, TCP) by two different molar percentages of strontium (5, 10) and zinc (1, 2), concomitantly with a fixed molar percentage (0.5) of manganese. Synthetic granular composite bone filling grafts consisting of doped &beta, TCP and an alkali-free bioactive glass were prepared and implanted in ~4 mm diameter bone defects drilled in the calvaria of Wistar rats used as animal models. The animals were sacrificed after 9 weeks of implantation and the calvaria was excised. Non-manipulated bone was used as positive control, while empty defects were used as a negative control group. The von Kossa staining revealed an enhanced new bone formation with increasing doping levels, supporting the therapeutic effects exerted by the doping elements. The percentage of newly formed bone was similar when the defects were filled with autologous bone, BG (previous results) or 3TCP2/7BG, which indicates that the latter two are excellent candidates for replacement of autologous bone as bone regeneration material. This finding confirms that doping with suitable doses of therapeutic ions is a good strategy towards transposing the bone graft materials to biomedical applications in humans.

High-performance bioceramics are required for preventing failure and prolonging the life-time of bone grafting scaffolds and osseous implants. The proper identification and development of materials with extended functionalities addressing socio-economic needs and health problems constitute important and critical steps at the heart of clinical research. Recent findings in the realm of ion-substituted hydroxyapatite (HA) could pave the road towards significant developments in biomedicine, with an emphasis on a new generation of orthopaedic and dentistry applications, since such bioceramics are able to mimic the structural, compositional and mechanical properties of the bone mineral phase. In fact, the fascinating ability of the HA crystalline lattice to allow for the substitution of calcium ions with a plethora of cationic species has been widely explored in the recent period, with consequent modifications of its physical and chemical features, as well as its functional mechanical and in vitro and in vivo biological performance. A comprehensive inventory of the progresses achieved so far is both opportune and of paramount importance, in order to not only gather and summarize information, but to also allow fellow researchers to compare with ease and filter the best solutions for the cation substitution of HA-based materials and enable the development of multi-functional biomedical designs. The review surveys preparation and synthesis methods, pinpoints all the explored cation dopants, and discloses the full application range of substituted HA. Special attention is dedicated to the antimicrobial efficiency spectrum and cytotoxic trade-off concentration values for various cell lines, highlighting new prophylactic routes for the prevention of implant failure. Importantly, the current in vitro biological tests (widely employed to unveil the biological performance of HA-based materials), and their ability to mimic the in vivo biological interactions, are also critically assessed. Future perspectives are discussed, and a series of recommendations are underlined.

Bone is a vascularized and connective tissue. The cortical bone is the main part responsible for the support and protection of the remaining systems and organs of the body. The trabecular spongy bone serves as the storage of ions and bone marrow. As a dynamic tissue, bone is in a constant remodelling process to adapt to the mechanical demands and to repair small lesions that may occur. Nevertheless, due to the increased incidence of bone disorders, the need for bone grafts has been growing over the past decades and the development of an ideal bone graft with optimal properties remains a clinical challenge. This review addresses the bone properties (morphology, composition, and their repair and regeneration capacity) and puts the focus on the potential strategies for developing bone repair and regeneration materials. It describes the requirements for designing a suitable scaffold material, types of materials (polymers, ceramics, and composites), and techniques to obtain the porous structures (additive manufacturing techniques like robocasting or derived from marine skeletons) for bone tissue engineering applications. Overall, the main objective of this review is to gather the knowledge on the materials and methods used for the production of scaffolds for bone tissue engineering and to highlight the potential of natural porous structures such as marine skeletons as promising alternative bone graft substitute materials without any further mineralogical changes, or after partial or total transformation into calcium phosphate.

A quaternary bioactive sol-gel glass of high silica content was heat treated at different temperatures, and then wet ball milled under different balls-to-powder ratios. A total of sixteen experiments were performed to study in detail the effects of both experimental variables on the structure, morphology, particle size distributions and nitrogen adsorption isotherms. The balls–to–powder ratio exerts a tremendous influence on the final particle size distribution of the powders, while its effects on the pore volume and morphology are minimal. These structural features are mostly governed by the changes in calcination temperature. Therefore, understanding the specific roles of each experimental parameter is of paramount importance towards achieving optimum powders with the desired properties. This work sheds light on the importance of using a suitable combination of these two parameters for tuning the morphology and the granulometry of the sol-gel derived bioactive glass powders.

Bone is a dynamic tissue with the capacity of repair and regeneration in specific conditions. Nevertheless, due to the increased incidence of bone disorders, the need of bone grafts has been growing over the past decades and the development of an ideal bone graft with optimal properties remains a clinical challenge. This review addresses the bone properties (morphology, composition and their repair and regeneration capacity) and puts the main focus on the potential strategies for developing bone repair and regeneration materials. It describes the requirements for designing a suitable scaffold material, types of materials (polymers, ceramics and composites) and techniques to obtain the porous structures (additive manufacturing techniques/robocasting or derived from marine skeletons) for bone tissue engineering applications. The main objective of this review is to gather the knowledge on the materials and methods for the production of scaffolds for bone tissue engineering and highlighting the potential of natural porous structures such as marine skeletons as promising alternative bone graft substitute materials without any further mineralogical changes, or after partial or total transformation into calcium phosphate. The suitability of the marine-derived porous bone graft substitutes for the intended applications will be also discussed.

Aluminosilicate glasses are considered to follow the Al-avoidance principle, which states that Al–O–Al linkages are energetically less favorable, such that, if there is a possibility for Si–O–Al linkages to occur in a glass composition, Al–O–Al linkages are not formed. The current paper shows that breaching of the Al-avoidance principle is essential for understanding the distribution of network-forming AlO4 and SiO4 structural units in alkaline-earth aluminosilicate glasses. The present study proposes a new modified random network (NMRN) model, which accepts Al–O–Al linkages for aluminosilicate glasses. The NMRN model consists of two regions, a network structure region (NS-Region) composed of well-separated homonuclear and heteronuclear framework species and a channel region (C-Region) of nonbridging oxygens (NBOs) and nonframework cations. The NMRN model accounts for the structural changes and devitrification behavior of aluminosilicate glasses. A parent Ca- and Al-rich melilite-based CaO–MgO–Al2O3–SiO2 ...

Advances on the fabrication of sintering-free biphasic calcium phosphate (BCP)/natural polymer composite scaffolds using robocasting as additive manufacturing technique are presented in the present work. Inks with high amounts of BCP powders (45 vol%) containing different HA/β-TCP ratios, in presence of crosslinked polymer, were successfully fine-tuned for extrusion by robocasting. The non-existence of sintering step opened the possibility to obtain drug loaded scaffolds by adding levofloxacin to the extrudable inks. The drug presence induced slightly changes on the rheological behaviour of the inks, more emphasized for the BCP compositions with higher amounts of β-TCP, and consequently, on the microstructure and on the mechanical properties of the final scaffolds. The strong interaction of β-TCP with chitosan difficult the preparation of suitable rheological inks for printing. Drug delivery studies revealed a fast release of levofloxacin with a high burst of drug within the first 30 min. Levofloxacin loaded samples also presented bacteria growth inhibition ability, proving that antibiotic was not degraded during the fabrication process and its bactericidal efficacy was preserved. From the results obtained, the composite scaffolds containing higher amounts of HA (around 80% HA/20% β-TCP) constitute a promising bi-functional synthetic bone substitute for simultaneous local bone regeneration and infection treatments.

This work reports on the unprecedented magnetron sputtering deposition of submicrometric hollow cones of bioactive glass at low temperature in the absence of any template or catalyst. The influence of sputtering conditions on the formation and development of bioglass cones was studied. It was shown that larger populations of well-developed cones could be achieved by increasing the argon sputtering pressure. A mechanism describing the growth of bioglass hollow cones is presented, offering the links for process control and reproducibility of the cone features. The composition, structure, and morphology of the as-synthesized hollow cones were investigated by energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), grazing incidence geometry X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM)-selected area electron diffraction (SAED). The in vitro biological performance, assessed by degradation tests (ISO 10993-14) and cytocompatibility assays (ISO 10993-5) in endothelial cell cultures, was excellent. This allied with resorbability and the unique morphological features make the submicrometer hollow cones interesting candidate material devices for focal transitory permeabilization of the blood-brain barrier in the treatment of carcinoma and neurodegenerative disorders.

Submitted by Bella Nolasco (bellanolasco@ua.pt) on 2017-07-26T14:52:11Z No. of bitstreams: 1 A new class of closed-cell aluminium foams reinforced with carbon nanotubes_10.1016j.ctmat.2016.06.003.pdf: 595912 bytes, checksum: f62f108e550e707ae7232423fbaee839 (MD5) Approved for entry into archive by Bella Nolasco(bellanolasco@ua.pt) on 2017-07-26T14:52:33Z (GMT) No. of bitstreams: 1 A new class of closed-cell aluminium foams reinforced with carbon nanotubes_10.1016j.ctmat.2016.06.003.pdf: 595912 bytes, checksum: f62f108e550e707ae7232423fbaee839 (MD5) Made available in DSpace on 2017-07-26T14:52:33Z (GMT). No. of bitstreams: 1 A new class of closed-cell aluminium foams reinforced with carbon nanotubes_10.1016j.ctmat.2016.06.003.pdf: 595912 bytes, checksum: f62f108e550e707ae7232423fbaee839 (MD5) Previous issue date: 2016

This paper reports on the preparation of cellular materials by different techniques. Bioactive and resorbable scaffolds based on biphasic calcium phosphate were produced by 3D-printing using extrudable pastes through fine nozzles, according to a pre-defined spatial arrangement considered suitable for bone regeneration and tissue engineering applications. Milled powders of cathode ray glass tubes and egg shell wastes were mixed and compacted to produce recycled glass foams via viscous flow sintering and thermal decomposition of the egg shell component that played the role of foaming agent. © 2016 Portuguese Society of Materials (SPM)

The sintering and crystallization behaviours of alkali-free bioactive glass compositions designed in the diopside (CaO center dot MgO center dot 2SiO(2))-tri-calcium phosphate (3CaO center dot P2O5) binary join by varying the Di/TCP ratios were investigated by hot-stage microscopy and differential thermal analysis, respectively. The effects of non-isothermal heating for 1 h at 900, 1000 and 1200 degrees C on the structural changes were assessed by solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) and crystalline phase assemblage. The influence of the heat treatment temperature on 3 point bending strength was also investigated. Diopside and hydroxyapatite formed as primary crystalline phases, accompanied by calcium silicate as secondary phase, in samples are sintered at 900 degrees C and 1000 degrees C. With further increase of the heat treatment temperature to 1200 degrees C, whitlockite that was stated appearing in some compositions at 1000 degrees C, appeared as main crystalline phase after diopside as a result of hydroxyapatite transformation. The data gathered was highly relevant towards setting the experimental conditions required for preparing well sintered and mechanically strong glass/glass-ceramic scaffolds for bone regeneration and tissue engineering applications. (C) 2015 Elsevier B.V. All rights reserved.

Submitted by Diana Silva (dianasilva@ua.pt) on 2017-05-31T09:14:07Z No. of bitstreams: 1 A novel approach to prepare aluminium-alloy foams reinforced by carbon-nanotubes_10.1016j.matlet.2015.07.115.pdf: 3592575 bytes, checksum: a9b815b567c028055262829eca6dbd79 (MD5) Approved for entry into archive by Diana Silva(dianasilva@ua.pt) on 2017-05-31T09:14:43Z (GMT) No. of bitstreams: 1 A novel approach to prepare aluminium-alloy foams reinforced by carbon-nanotubes_10.1016j.matlet.2015.07.115.pdf: 3592575 bytes, checksum: a9b815b567c028055262829eca6dbd79 (MD5) Made available in DSpace on 2017-05-31T09:14:43Z (GMT). No. of bitstreams: 1 A novel approach to prepare aluminium-alloy foams reinforced by carbon-nanotubes_10.1016j.matlet.2015.07.115.pdf: 3592575 bytes, checksum: a9b815b567c028055262829eca6dbd79 (MD5) Previous issue date: 2015

summary, Zn 1 x Ni x O nanopowders with different Nicontents ofx=0.0,0.04and0.08hasbeensuccessfullysynthesizedvia lowcostsonochemicalreactionmethod.TheeffectofNidopingon Energy structuralevolutionandopticalpropertiesofZnOnanopowdershave been systematically investigated. All the diffractions peaksobserved inXRD patternofpreparednanopowderssamples showspure wurtzite phase for Zn 1 x Ni x O nanostructures with noadditional impurity peaks. Raman spectra of prepared Zn 1 x Ni x Onanopowders reveal a strong peak at 438cm 1 corresponding tofirst order optical mode for wurtzite ZnO structure. The opticalband [31] gap (E g ) was found to decrease with increase in Ni contentfrom 3.33eV(x=0.0),3.26eV(x=0.04)to3.05eV(x=0.08),andthebehaviours was inconsistentwithopticalbehaviourobservedinPLspectra. Tuning of band gap with successful synthesis of ZnOnanopowders on Ni doping demonstrate that Zn 1 x Ni x O nano-powders are useful for various electronic and optical deviceapplications.AcknowledgementsAuthors, BudhendraSinghandAjayKaushalwouldliketothankFundacao para a Ciencia e a Tecnologia for the financial support(Funded by NSRF–POPH) under the grant nos. SFRH/BPD/76184/2011and SFRH/BPD/77598/2011, respectively. Authors are alsothankful to Dr. Suresh Kumar Jakka from Department of Physics,University of Aveiro for PL measurement of prepared samples.References

Although bioactive glasses are successfully used as bone substitutes, recent studies have revealed that the high alkali content in these glasses leads to fast in vivo degradation rates that may not match the rate of new bone ingrowth. This prompted us to design and develop novel bioactive glasses that are devoid of alkali but still demonstrate high bioactivity in vitro. This article describes the in vivo performance of an alkali-free bioactive glass with the following composition (Wt %): 13.03 MgO-33.98 CaO-13.37 P2 O5 -38.84 SiO2 -0.77 CaF2 (labelled as FastOs® BG). An animal model was used to assess the in vivo performance of FastOs® BG, using 45S5 Bioglass® as control. The evaluation was performed through implantation of FastOs® BG and 45S5 Bioglass® , during one month, in femoral bone defects in sheep. Subcutaneous implantation of both glasses was also performed in order to assess tissue response through a standardized method. Histological and scanning electron microscopy assessment of retrieved subcutaneous and bone samples demonstrated that FastOs® BG is biocompatible, osteoconductive, that it can be osteointegrated, and that it is more slowly resorbed than 45S5 Bioglass® . These features suggest that FastOs® BG is a potential candidate for bone grafting. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 30-38, 2017.

Bionanocomposite coatings with antimicrobial activity comprising polyvinyl alcohol (PVA)-capped silver nanoparticles embedded in chitosan (CS) matrix were developed by a green soft chemistry synthesis route. Colloidal sols of PVA-capped silver nanoparticles (AgNPs) were synthesized by microwave irradiating an aqueous solution comprising silver nitrate and PVA. The bionanocomposites were prepared by adding an aqueous solution of chitosan to the synthesized PVA-capped AgNPs sols in appropriate ratios. Uniform bionanocomposite coatings with different contents of PVA-capped AgNPs were deposited onto titanium substrates by \"spread casting\" followed by solvent evaporation. Nanoindentation and antimicrobial activity tests performed on CS and bionanocomposites revealed that the incorporation of PVA-capped AgNPs enhanced the overall functional properties of the coatings, namely their mechanical stability and bactericidal activity against Escherichia coli and Staphylococcus aureus. The coated specimens maintained their antimicrobial activity for 8 h due to the slow sustained release of silver ions. The overall benefits for the relevant functional properties of the coatings were shown increase with increasing contents of PVA-capped AgNPs in the bionanocomposites. (C) 2015 Elsevier Ltd. All rights reserved.

The present work is an amalgamation of computation and experimental approach to gain an insight into composition–structure–bioactivity relationships of alkali-free bioactive glasses in the CaO–MgO–SiO 2 –P 2 O 5 system. The glasses have been designed in the diopside (CaO·MgO·2SiO 2 ; Di)–tricalcium phosphate (3CaO·P 2 O 5 ; TCP) binary join by varying the Di/TCP ratio. The melt-quenched glasses have been investigated for their structure by molecular dynamic (MD) simulations as well as by nuclear magnetic resonance spectroscopy (NMR). In all the investigated glasses silicate and phosphate components are dominated by Q 2 (Si) and Q 0 (P) species, respectively. The apatite forming ability of the glasses was investigated using X-ray diffraction (XRD), infrared spectroscopy after immersion of glass powders in simulated body fluid (SBF) for time durations varying between 1 h and 14 days, while their chemical degradation has been studied in Tris–HCl in accordance with ISO 10993-14. All the investigated glasses showed good bioactivity without any substantial variation. A significant statistical increase in metabolic activity of human mesenchymal stem cells (hMSCs) when compared to the control was observed for Di-60 and Di-70 glass compositions under both basal and osteogenic conditions.

The prevention of microbial infections associated with implantable medical devices and superficial wounds represents one of the main research strategies in the field of biomaterials. The present study reports on the development of composite membranes of Chitosan (CS)-Polyethylene glycol (PEG) matrix, incorporating particles of biphasic calcium phosphate (BCP), zinc oxide (ZnO) and copper oxide (CuO). The properties that are relevant for intended applications in tissue regeneration and antibacterial coatings of implants were assessed. It was found that the addition of 1% (w/w - relative to the mass of CS) of each metal oxide promoted satisfactory bacteriostatic activity and exhibited no cytotoxic effects towards the Vero cell line. The formation of bonds between the CS/PEG matrix and ionic species from the powders enhanced the cross-linking degree and mechanical properties of composite membranes in comparison to the non-doped membrane with the same polymer matrix (CS/PEG = 70/30%). A gradual degradation of the composite membranes over the immersion time in simulated body fluid (SBF) was accompanied by a continuous surface deposition of uniform apatite layer.

The manuscript focuses on manufacturing of new in situ foam-filled tubes (in situ FFTs) of Al-alloys including the foaming stage and studying their mechanical behaviour under quasi-static and dynamic bending loadings. The composite structures were manufactured by the powder compact foaming technique. These structures are fabricated by heating foamable precursor material pieces above their solid temperature inside thin-walled tubes. Different manufacturing parameters were appropriately adjusted based on preliminary experiments. The mechanical crushing behaviour and failure mechanisms were assessed by three-point bending experiments supported by infrared thermography. The bending performance of in situ FFTs and ex situ foam-filled heat treated tubes (ex situ FFTTs) were compared with that of empty tubes subjected to heat treatment. The observed results have been explained in terms of the structural changes in the thermally treated tubes, the surface roughness derived from oxidation, and the dimensions of the interface gap between the two components in the composite structures. The in situ FFTs composite structures confirmed stable and controllable deformation and a promising energy absorption capability. (C) 2014 Elsevier Ltd. All rights reserved.

The aim of the present work is to investigate the effect of substituting B2O3 for Al2O3 in a non-stoichiometric lithium disilicate (Li2Si2O5, LS2) glass composition belonging to the system Li2O–K2O–Al2O3–SiO2. Addition of equimolar amounts of K2O and Al2O3 to binary lithium silicate glass compositions improves chemical resistance, sintering behaviour and mechanical properties of the glass-ceramics produced from sintered glass powder compacts. However, in bulk (monolithic) glasses Al2O3 addition hinders bulk nucleation. It also suppresses crystallization of LS2 and promotes formation of a meta-stable crystalline phase called lithium metasilicate (Li2SiO3, LS). The results showed that B substitution resulted in the depolymerisation of the glass network increasing the percentage of NBOs leading to decreasing viscosity, molar volumes, oxygen densities and glass transition temperatures. The simultaneous addition of Al and B into the glass composition resulted in decreased liquid–liquid phase segregation (LLPS) and lower crystal nucleation tendency when compared to Al pure or B pure compositions. Further, Al rich glasses featured lithium metasilicate crystallization at initial stages and then transformed into LS2 at higher temperatures, while with B addition glasses crystallize directly into LS2.

Novel quaternary (67Si-24Ca-10Na-8P) glass powders were successfully synthesised by sol-gel followed by two alternative drying schedules, conventional drying (CD) and an innovative fast drying (FD) process (200 times quicker). The glasses were thermally stabilised at 550 °C, and then characterised by different complementary techniques. The samples showed very similar silica network structures, with the FD one having slightly lower degree of polymerisation than the CD sample. This less polymerised, more open, network structure exhibited an improved bioactivity in simulated body fluid (SBF), probably also due to the apparent presence of poorly crystalline HAp in the stabilised glass powder. In contrast, the CD glass exhibited an unwanted secondary crystalline silica phase. Both glasses showed excellent biomineralisation upon immersion in SBF, being more pronounced in the case of FD with clear evidence of HAp formation after 4 h, while equivalent signs in the CD samples were only noticed after longer immersion periods between 8 h and 1 week.

The self-aggregation, surface properties and foamability of the catanionic surfactant mixture cetyltrimethylammonium bromide (CTAB)/sodium octyl sulfonate (SOSo) have been investigated to obtain insight on the relation between bulk nanostructures, surfactant packing, and foam stability and aging. Light microscopy, SANS, cryo-TEM, DLS, surface tension, rheometry and direct photography were used to characterize mixtures with varying CTAB molar fraction, xCTAB. In the bulk, self-assembly is richer in the excess CTAB region than in the excess SOSo one. Starting from neat CTAB micelles and on addition of anionic surfactant, there is a change from small ellipsoidal micelles (1 < xCTAB ≤ 0.80) to large rodlike micelles (0.65 ≤ xCTAB ≤ 0.55) and then to vesicles (0 < xCTAB ≤ 0.50), with coexistence regions in between; SOSo-rich mixtures are thus dominated by vesicles. High size polydispersity for the micelles and vesicles is an intrinsic feature of this system. Foam stability is concomitantly impacted by xCTAB. SOSo is a small mobile molecule and so it disrupts foam stability, irrespective of the presence of vesicles. Foams are thus only stable in the CTAB-rich regions, and SANS shows that the shape of micelles and vesicles is unchanged inside the foam. Foam drainage is thereby mostly controlled by the presence of the elongated micelles through the solution viscosity, whereas coarsening is influenced by dense surfactant packing at the gas–liquid interfaces.

The role of CaF2 on the structure, crystallization behaviour and properties of a relatively simple non-stoichiometric lithium disilicate (Li2Si2O5) based glass composition was studied. Different x amounts (x = 0, 1, 3 and 5 mol%) of CaF2 were added to (100 - x) of a parent glass (22.96Li(2)O-2.63K(2)O-2.63Al(2)O(3)-71.78SiO(2)) composition. The glasses were produced by conventional melt-quenching technique, whilst glass-ceramics were produced via crystallization of monolithic bulk glasses. A scanning electron microscopy (SEM) examination of as cast non-annealed monolithic glasses revealed precipitation of nanosize droplet phase in glassy matrices suggesting the occurrence of liquid phase separation in all investigated compositions. The extent of phase segregation, as judged from the mean droplet diameter and the packing density of droplets, decreased with increasing CaF2 content in the glasses. A slight depolymerisation of the glass network was observed according to magic angle spinning nuclear magnetic resonance (MAS-NMR) and Fourier transform infrared (FTIR) spectroscopic studies, suggesting a network modifier role for CaF2. The presence of CaF2 enhanced the crystallization at lower temperatures in comparison to CaF2-free glass. (C) 2014 Elsevier B.V. All rights reserved.

The present paper reports on the successful fabrication of micro-sized pillar arrays of Ba0.6Sr0.4TiO3 (BST) electroceramics via cost effective epoxy gel casting (EGC) consolidation method based on the in situ polymerization of aqueous suspensions with added water soluble epoxy resin. The synthesized BST solid solution powder was fine milled and surface protected against hydrolysis to avoid its degradation in the aqueous environment. The micro patterning process was divided in the following steps: (i) production of high quality SU-8 master moulds by photolithography and of the respective negative replicas in PDMS (soft mould); (ii) casting of stable high solid loading BST suspensions in the soft moulds with added setting agents followed by de-moulding, drying and sintering. Patterned array of hexagonal shaped pillars with 320 mu m of height and side length similar to 40 mu m were obtained with smooth side wall features along height. Various structural, mechanical and electrical properties of BST material after sintering were also measured to demonstrate the feasibility of the proposed aqueous processing route. (C) 2014 Elsevier Ltd. All rights reserved.

We report on the effect of sodium on the structure, chemical degradation and bioactivity of glasses in the CaO-MgO-SiO2-P2O5-CaF2 system. The Si-29 and P-31 magic angle spinning-nuclear magnetic resonance spectroscopy of melt-quenched glasses with varying Na2O/MgO ratios exhibit a silicate glass network with the dominance of Q(2)(Si) units and phosphorus mainly forming orthophosphate species. Sodium incorporation in the glasses did not induce a significant structural change in the silicate network, while it did influence the phosphate environment due to its lower ionic field strength in comparison with that of magnesium. The apatite forming ability of glasses has been investigated by immersion of glass powders in simulated body fluid (SBF) for time durations varying between 1 h and 7 days while their chemical degradation has been studied in Tris-HCL in accordance with ISO-10993-14. Increasing Na+/Mg2+ ratio caused a decrease in the chemical durability of glasses and in the apatite forming ability especially during initial steps of interaction between glass and SBF solution. The cellular responses were observed in vitro on bulk glass samples using mouse-derived pre-osteoblastic MC3T3-E1 cell line. The preliminary study suggested that the increasing alkali-concentration in glasses led to cytotoxicity in the cell culture medium. (C) 2014 Elsevier B.V. All rights reserved.

ZnO-ZnS-Ag2S ternary nanostructures were prepared by a simple and low-cost chemical precipitation method. The sample was characterised by X-ray diffraction, energy-dispersive X-ray, UV-Vis-NIR, Raman and Fourier transform infrared spectroscopy. Morphology of the sample was studied by scanning electron microscopy and it was observed that ZnO nanoplates were covered with ZnS and Ag2S nanoparticles. A high resolution transmission electron microscope was used to obtain further information about the crystalline domains of the prepared ternary nanostructure. The Kramers-Kronig method and classical dispersion theory were utilised to study the optical properties of the sample in the far-infrared region. Photocatalytic activity of the prepared samples was also attained in the gas solid phase by using a solar lamp (simulating outdoor lighting) and monitoring NOx degradation.

In the Azores archipelago, a significant proportion of buildings are infested with the urban exotic drywood termite Cryptotermes brevis (Walker), causing major economical and patrimonial losses. This work aims to understand the potential spread of this termite species in the Azores and estimate the costs for both treatment and reconstruction of infested buildings in the entire archipelago. A maximum entropy niche modeling process was used to determine the potential occurrence of the species on each island. Different scenarios were built using independent global and regional incidence and environmental data. Both projections reveal the same pattern. Generally, the probability of occurrence is higher near the coast line, where, in Azores, the majority of the towns and villages are located. We also predict that the infestation has potential to spread to yet unaffected towns and islands. It is estimated that the cost of treating all currently infested buildings in the archipelago is 51 million, while reconstruction of the same buildings would rise the costs to 175 million. We predict that the absence of a control strategy will cause a further expansion of the pest to more localities in the Azores. An estimate to future scenarios implies higher costs, with treatment and rebuilding values rising up to eight times the current values.

Er, Er-Ag and Er-Mg co-doped ZnO nanopowders were prepared by wet chemical precipitation method. The structure and morphology of the prepared samples were studied by XRD and SEM, respectively. The effect of Ag and Mg on visible and IR emission properties of Er doped ZnO nanopowders have been systematically investigated. We found that Mg did not change the visible and IR emission properties of Er doped ZnO nanopowders. But, addition of Ag drastically decreases the visible emission and enhances the IR emission at 1536 nm. (C) 2014 Elsevier B.V. All rights reserved.

Cuttlefish bone (CB) has been explored as biomaterial in the bone tissue-engineering field due to its unique porous structure and capacity of the aragonite mineral to be hydrothermally converted into calcium phosphates (CaPs). In the present study, undoped and ion (Sr2+, Mg2+ and/or Zn2+) doped biphasic calcium phosphate (BCP) scaffolds were prepared by hydrothermal transformation (HT, 200 °C, 24 h) of CB. The obtained scaffolds were sintered and then coated with two commercial polymers, poly(e-caprolactone) (PCL) or poly(DL-lactide) (PDLA), and with two synthesized ones, a poly(ester amide) (PEA) or a poly(ester urea) (PEU) in order to improve their compressive strength. The scaffolds were characterized by X-ray diffraction (XRD) coupled with structural Rietveld refinement, Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The results demonstrate that CB could be entirely transformed into BCPs in the presence or absence of doping elements. The initial CB structure was preserved and the polymeric coatings did not jeopardize the interconnected porous structure. Furthermore, the polymeric coatings enhanced the compressive strength of the scaffolds. The in vitro bio-mineralization upon immersing the scaffolds into simulated body fluid (SBF) demonstrated the formation of bone-like apatite surface layers in both uncoated and coated scaffolds. Overall, the produced scaffolds exhibit promising properties for bone tissue engineering applications.

Bioactive glasses are osteoproductive-type inorganic materials possessing the highest indices of bioactivity in both bulk and thin film forms. The prerequisites for reliable implant-type coatings are both their biological and mechanical performances. Whilst the bioglass films' structural, chemical and biological properties have been studied extensively, information about their mechanical performance is scarce. Here, transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nanoindentation and pull-out measurements were employed to assess the morphological, chemical, structural and mechanical properties of the bioglass films deposited onto Ti substrates by radio-frequency magnetron sputtering (RF-MS). The biological safety of the thin bioglass films was evaluated preliminarily in vitro by investigating the adherence, proliferation and cytotoxicity of fibroblast cells cultivated on their surface. Our study emphasize the versatility of RF-MS, showing how bioglass films' features such as composition, structure, bonding strength, hardness, elastic modulus and biological response can be conveniently adapted by tuning the RF-MS working conditions, and therefore demonstrating the unexplored potential of this deposition technique for preparing quality biomimetic glass coatings. (C) 2013 Elsevier B. V. All rights reserved.

The role of Sr/Ca ratio, which was varied from 3/6 to 9/0, on the structure, crystallization behavior and properties of diopside-based glass and glass-ceramic sealants targeted to solid oxide fuel cell (SOFC) applications was evaluated. The structural changes undergone by glass-powder compacts during isothermal heat treatment at 850 degrees C for 1-1000 h were investigated using XRD (X-ray diffraction) analysis, including quantitative Rietveld refinement, and MAS-NMR (magic angle spinning nuclear magnetic resonance) techniques. The tendency towards crystallization was retarded with increasing Sr/Ca ratio. Diopside-based phases, strontium akermanite and magnesium silicate were developed under various heat-treatment conditions. MAS-NMR analysis of glasses heat treated for 1000 h revealed that with increasing Sr/Ca ratio, Q(1) and Q(4) structural units were formed at the expenses of Q(2) units. The good thermal stability and chemical compatibility of the new glass-ceramic compositions coupled with their mechanical reliability and high electrical resistivity make them attractive for further experimentation as sealants for SOFCs. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Thermal stability of lanthanide (Ln = La, Nd, Gd, Yb) containing glass and glass-ceramics (GCs) was characterized for their application as sealants for solid oxide fuel cells (SOFCs). X-ray diffraction (XRD) in conjunction with the Rietveld-RIR and solid-state NMR techniques was employed to quantify the crystalline and amorphous fractions in the glasses sintered/heat treated at 850 degrees C in air for 1-1000 h. The structure and crystalline phase evolution of Ln containing aluminosilicate glasses depend markedly on the Ln(3+) cation field strength over both short and intermediate length scales. Along with diopside, Ln containing silicate apatites, with general formula Ln(9.33+2x)(Si1-xAlxO4)(6)O-2 (Ln = La, Nd and Gd; with x varying between 0 and 0.33), were observed in the GCs after the heat treatment periods of 1 to 1000 h at 850 degrees C, leading to moderately higher electrical conductivity. The substantial amount of the remaining glassy phase in Gd2O3-containing GC after 1000 h at 850 degrees C is likely to confer self-healing properties to this composition, in accord with the oxygen leakage measurements on thermal cycling. Si-29, Al-27 and B-11 magic-angle spinning (MAS) NMR spectra confirmed the results of the XRD RIR analysis. The values of Weibull characteristic strength and of average flexural strengths for all the GCs are higher than those reported for G-18 commercial glass (51 MPa), with Weibull modulus varying in the range 11.6-34.4 towards good mechanical reliability. Thermal shock resistance of model electrochemical cells made of yttria-stabilized zirconia (YSZ) was evaluated employing quenching from 800 degrees C in air and water. All the GC seals bonded well to YSZ and Sanergy HT metallic interconnects without gap formation. Suitable thermal expansion coefficient (9.7-11.1 x 10(-6) K-1), mechanical reliability, high electrical resistivity, strong adhesion to Sanergy HT interconnects and YSZ, and sufficient thermal shock resistance indicate good suitability of the lanthanide-containing sealants for SOFC applications.

We report on the successful aqueous processing of a lead free piezoelectric 0.5Ba(Zr0.2Ti0.8)O-3-0.5( Ba0.7Ca0.3)TiO3 (BZT-BCT) composition with the final functional properties of the materials unaffected by the various processing steps involved. X-ray diffraction results show a single tetragonal perovskite crystalline phase for the as-received sintered BZT-BCT powder. The purity of the perovskite phase for BZT-BCT powder was found to be controlled even after ageing the material in water for 24 h as a successful surface treatment against hydrolysis. An aqueous suspension of surface treated BZT-BCT powder with 50 vol% solid loading was successfully transformed into micro-sized granules via a freeze granulation (FG) method. Various structural, electrical and mechanical properties of sintered BZT-BCT-FG and BZT-BCT-NG ceramics consolidated from freeze granulated and non-granulated (NG) powders, respectively, were measured. The dielectric constant (epsilon(r)) values of the BZT-BCT-FG sample were found to be higher, with lower dielectric loss (tan delta) values in comparison with those of a sample prepared from the BZT-BCT-NG powder at all temperatures and with all frequency ranges tested. Nanoindentation results revealed that the ability to oppose deformation was nearly 10-fold higher for BZT-BCT-FG (6.93 GPa) than for BZT-BCT-NG ceramics (543 MPa). The functional properties of BZT-BCT- FG samples confirmed the benefits of the aqueous processing approach in comparison with traditional dry pressing.

We report on synthesis of rare earth Er doped ZnO nanoplates via low cost wet precipitation method. The effect of varying Er doping concentration in the range from 3, 5 to 7 wt% on structural, optical and electrical properties of ZnO nanoplates has been successfully investigated. X-ray diffraction (XRD) studies show hexagonal wurtzite phase structure of prepared Er doped ZnO nanoplates. Scanning electron microscopy (SEM) reveals the growth Of nanoplates like structures of the prepared samples. Further, the presence of Er ions doping in ZnO matrix has been confirmed by EDS measurement. A sharp and strong peak at around 435 cm(-1) was observed in Raman spectra of nanoplates which correspond to the high frequency branch of the E2 mode of ZnO. The frequency dependence of dielectric constant (epsilon(r)), dielectric loss (tan delta) and AC conductivity of ZnO nanoplates of different Er doping concentration were measured. The dielectric properties of pure and Er doped ZnO nanoplates follow a behavior based on Maxwell-Weigner model. The AC conductivity was found to decrease with Er doping. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

The present paper reports the overall benefits of freeze granulation for enhancing the properties of zirconium tin titanate Zr0.8Sn0.2TiO4 (ZST) ceramics in the total absence of sintering additives. The ZST powder was synthesized by solid state reaction and attrition milled in ethanol for 10 h. This starting non-granulated powder (NG-ZST), without and with 1 wt% ZnO as sintering additive, was used to consolidate green bodies by dry pressing. The pure ZST powder was also dispersed in aqueous media to obtain stable suspensions with high solid loadings. Free flowing spherical homogeneous granules were prepared by freeze granulation and used to consolidate ZST green bodies by dry pressing (FG-ZST). The effects of processing variables and sintering temperature (1300-1450 degrees C) on densification and on the structural, mechanical and electrical properties of ZST ceramics were systematically investigated. Our study clearly reveals the superior properties of FG-ZST ceramics, which derive from an enhanced sintering behaviour associated with the absence of sintering additives.

The sintering behaviour of an alkali-free bioactive glass with its chemical composition corresponding to 80 wt.% diopside (CaMgSi 2 O 6 )–20 wt.% fluorapatite [Ca 5 (PO 4 ) 3 F] has been reported in this article. Glass powders with different particle size distributions and mean particle sizes varying between 14 μm and 220 μm were used. The influence of particle size variation on sintering ability of glass powders was studied by using an array of complementary advanced characterization techniques including in situ high temperature scanning electron microscopy (HT-SEM), differential thermal analysis (DTA), hot stage microscopy (HSM), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The obtained results have been discussed with their implications on the development of glass–ceramic scaffolds for bone tissue engineering. Glass–ceramics consisting of dense glassy matrix with embedded diopside and fluorapatite crystals were obtained after sintering the glass powder compacts at 850 °C for 1 h.