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Three composite materials with different CaZrO3/MgO fractions (2/3, 1/2, 1/3) and two single-phase materials (CaZrO3 and MgO) were fabricated and their thermal conductivity was investigated. Complete thermal and mechanical characterizations (thermal expansion coefficient, thermal diffusivity, specific heat, hardness and toughness) of the materials were performed. Values of the thermal conductivity up to 480 °C of the composites were compared with those calculated with the main analytical models. From the real microstructures of the three composites, representative volume elements (RVE) were built and used for finite element modelling (FEM) of thermal conductivity using conductivities of the single-phase materials as inputs. The FEM results showed no differences for the 3 spatial directions of the RVE, nor for the different edge lengths (11, 14 and 17 μm). Results of all analytical models are statistically different from the experimental ones, being those from the Bruggeman model the closest. Results of the proposed FEM are statistically coincident with the experimental ones, showing sensitivity to temperature variation.

A water treatment sludge (WTS) was characterized in order to evaluate if its properties would be suitable for use as liner of earthworks or for strengthening a clay soil. A WTS and a clayey soil was characterized in terms of granulometry, cumulative volumes, specific surface, density, plastic limit, liquid limit, water content, hydraulic conductivity, and characteristics of compaction (optimal water content and dry density). This study aimed to exhibit and evaluate these investigated parameters of WTS, soft soil and mixed proportions between the materials for liners’ material production while evaluating soft soils’ reinforcement feasibility. The results have shown WTS’s contribution with its fine granulometry and compaction characteristics, indicating filling properties and possible feasibility as soft soils additions for liners’ material production while being applicable for soils‘ reinforcements, corroborating with existing literature on the subject. Thus, the currently developed investigation has exposed WTS as a potential addition for these applications while also attending society’s new demands towards a more sustainable future.

Starting from synthetic raw materials (CaZrO3 and MgO), microstructural and mechanical properties were optimised in order to obtain dense multiphasic ceramic, then finite element method (FEM) of an equimolar (1:1) CaZrO3-MgO composite was performed in order to obtain the effective elastic modulus. Composite presents two main phases of orthorhombic CaZrO3 (81.5 wt.%) and cubic MgO (18.5 wt.%); For 1500 °C, relative density of 99.9%, characteristic strength of 168 MPa, hardness of 7.8 MPa and toughness of 2.5 MPa.m1/2 were obtained. FEM simulation was performed using two representative volume elements (RVE’s) with edge lengths of 14 μm (933 grains) and 17 μm (1670 grains), using isotropic elastic model, and anisotropic on specific set of crystallographic planes. The results of FEM using isotropic approach for the two RVE’s are perfectly aligned with the experimental (245 GPa), while the anisotropic model shows a difference of 6.5%.

The article presents the process of welding of steel movable platform supports. There is a growing demand for the welding of difficult-to-weld fine grain steels used in civil engineering and transport. An example of this could be the use of high-strength movable platform supports. The recently used material in the production of movable platform supports are fine-grained steels due to their high tensile strength of 1000 MPa. The joints formed using them, however, are characterized by much lower strength than the native material. In this article, the most appropriate parameters were selected for welding the movable platform supports made of difficult-to-weld fine-grained steel S960 MC.

In this work a methodology to reconstruct three-dimensional microstructures, representative of real biphasic ceramics using Neper free software is proposed. Finite element analysis in Ansys was implemented in order to calculate the effective elastic modulus of the simulated microstructures. Fine grained and dense zirconia toughened alumina (ZTA) materials with 5 and 40 vol.% of Yttria Stabilized Zirconia (YTZP) have been chosen to validate the proposed methodology. First, the effects of the size of the representative volume elements (RVEs) and the characteristics of the grain shapes are analysed. Second, the compliance with the isotropic condition is also verified. Agreement between the numerical and experimental values of the elastic modulus of the considered ZTA materials has been found. For these materials, zirconia fractions higher than 10 vol.% lead to bi-continuous microstructures which make the elastic properties deviate from the Voigt limit due to the increased number of contacts between zirconia grains.

In welding elements of the supporting structure of the means of transport, attention is paid to the high strength and good plastic properties of the welded joint. In the construction of transport means, DOCOL 1200M steel from the AHSS group is increasingly used due to their high tensile strength of steel at the level of 1200 MPa. The welds have much lower strength than the native material. In this paper, it was decided to check the weldability of DOCOL 1200M steel with the use of micro-jet cooling

This work aims to better comprehend the mechanical behaviour, including failure sequence and failure modes, of differently surface-treated CFRP T-joints when subjected to out-of-plane loadings. Specimens consisted in two CFRP adherends – skin and stiffener – adhesively bonded with a structural film adhesive. The adherends' untreated and treated (by peel ply or abrasion) surfaces were firstly characterized using scanning electron microscopy (SEM), profilometry and wettability measurements. Stiffener pull-off tests (SPOT) were then experimentally conducted under quasi-static loading. The fractured surfaces were analysed by fractography to identify the failure mechanisms. The peel ply treatment has led to the worst results in terms of maximum load, while the abrasion-treated specimens performed the best of the three series. Surface characterization and fractography analysis were properly correlated with the SPOT results. Fracture damage typically initiates as mode I within the tip of the stiffener's flange, but as the fracture extends along the stiffener's foot, it does it under predominant mode II.

The biofunctionalization of metal implants with bioactive ceramics arises as an appealing strategy for promoting their osseointegration, without impairing implants’ good mechanical resistance. In this work, biocomposites of hydroxyapatite - CaZrO3 were obtained by rate controlled sintering and their microstructure, mechanical properties, biological as well as the effect of stoichiometric calcium zirconate dopant on the decomposition of HA were analysed. The results obtained showed that the addition of CaZrO3 stabilizes the hydroxyapatite at least up to 1300 °C and inhibits the appearance of the α- and β-TCP phases. Moreover, the mechanical properties of the hydroxyapatite were improved with 10 wt% of CaZrO3, despite the increase of porosity. The in vitro assays demonstrated that the biocomposites were biocompatible, since they favoured human osteoblast cells adhesion and proliferation. All the data obtained emphasize the potential of these biocomposites for the aimed biomedical application.

Thermosetting polymers are very popular in the automotive and aeronautic industry, in particular epoxy resin is widely used as matrix thermoset in carbon and glass fibre reinforced composites. The properties of these epoxy-based polymers can be improved with the addition of particulate or small fibre materials in order to construct a lightweight material with enhanced mechanical and structural response. This work aimed to manufacture and characterize epoxy resin reinforced composites with iron (II, III) oxide (magnetite, Fe3O4) in amounts of 0.25, 0.5 and 1 wt%, and 2 and 4 wt% of fumed silicon dioxide (silica, SiO2). Mechanical properties were investigated by three-point bending flexural test, fracture toughness, flexural stress relaxation. In addition, apparent porosity, apparent density and Differential Scanning Calorimetry tests were performed. The results showed that the addition of Fe3O4 does not contribute significantly to the improvement of mechanical properties. However, fumed SiO2 promotes a considerable improvement in the mechanical properties. Keywords: Composite, epoxy resin, Fe3O4, SiO2, mechanical properties

The polymeric optical fibre technology can be successfully used for UV spectrum range radiation measurements.Anew type of fluorescent optical fibre optode is presented. The used fluorescent wave-shifter was used for UV-VIS conversion and radiation measurements. The linear characteristic with sensitivity 480 mW−1 is presented for UV range 7.2-13.6 mW. Presented optode construction advantages (small dimensions, low weight, high immunity to electromagnetic fields and distributed sensor architecture possibility) are attractive for numerous composite based engineering applications.

The demand for mixed joints of hard-welded steels used in civil engineering and transport is increasing. An example of this can be welding of pins of high-strength steel S690 QL (1.8928) with the arms of a movable platform made of DOCOL 1200M steel from the AHSS group. This joint is difficult to make properly, due to significant differences in the thickness of welded elements and different chemical composition of both steels. The thickness of the cylindrical pin is 40 mm, the diameter of the pin is 50 mm. The thickness of the metal sheet used for the mobile platform arm is 2 mm. . Joints of varying thickness and chemical composition may have cracks in the heat affected zone and in the weld. The purpose of the article is to determine the most appropriate welding parameters and the selection of filler materials that will allow to obtain the correct joint without welding defects.

Despite environmental pressures and intrinsic recycling potential, spent refractories waste is generally considered an economically unattractive waste stream. This work proposes an upgraded view of the debris recovered from dismantled spinel-bonded high-alumina linings of steel induction furnaces, demonstrating that it can be reused in the form of vibratable and self-flowing castable systems. The recovered material retains the microstructural distribution of in situ spinel formation without the corresponding disruptive expansion, mirroring the use of pre-formed spinel without the onus of a pre-firing. The mechanical performance after firing was found to be always best for the self-flowing system, which is also less affected by changes in added-water content. There is potential for large usages of cleaned waste (50–60 wt%), which helps reducing the supply risk for major refractory primary raw materials as well as landfilling costs.

An attractive way to obtain low cost calcium zirconate (CaZrO3) composites is mixing natural limestone or dolomite with zirconia. These CaZrO3 based ceramic composites were often investigated as a promising high refractory for casting metal alloys, cements, thermal and environmental barrier coating. In this study the sliding wear, fracture mechanism and friction properties of a CaZrO3-MgO-ZrO2 ceramic against ZrO2 and steel counter bodies was carried out. Wear and fracture surface mechanisms, influence of its impurities and individual phases are discussed. The composite presents a coefficient of friction higher in ceramic/metal than in ceramic/ceramic pair, but the specific wear it is significantly higher when tested with the ZrO2 ball. The fracture surfaces presenta dominant transgranular fracture when tested with steel and intergranular fracture against ZrO2. Fil: Silva, Abílio. Instituto de Cerámica y Vidrio de Madrid; España. Consejo Superior de Investigaciones Científicas; España Fil: Booth, Raul Fernando Nicolas. Instituto de Cerámica y Vidrio de Madrid; España. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina Fil: Garrido, Liliana Beatriz. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina Fil: Aglietti, Esteban Fausto. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina Fil: Pena, Pilar. Consejo Superior de Investigaciones Científicas; España. Instituto de Cerámica y Vidrio de Madrid; España Fil: Baudín, Carmen. Consejo Superior de Investigaciones Científicas; España. Instituto de Cerámica y Vidrio de Madrid; España

The compound of poly(lactic acid) (PLA) and cellulose was made by the emulsion-solvent evaporation technique in order to obtain spheres which are then compression molded to produce a biocomposite film. The effect of the dispersant (poly(vinyl alcohol)&mdash, PVA)/PLA ratio on the spheres yield was studied. Moreover, to evaluate the effect of cellulose particle size and surface chemistry on the process yield, unbleached eucalypt kraft pulp and microcrystalline cellulose (MCC), both unmodified and physically or chemically modified were used. PLA/cellulose spheres were characterized regarding its physical properties. It was found that the spheres yield is essentially determined by the PVA/PLA ratio and the percentage of cellulose incorporation is greatly affected by the surface chemistry of cellulose. Regarding the films, DSC runs showed a significant effect of the cellulose type incorporated into PLA matrix on the cold crystallization temperature and on the degree of crystallinity of the biocomposite films. The measurement of tensile properties of the biocomposite films revealed that the strength, elongation at break and toughness (tensile energy absorption at break) of the films incorporating unmodified and chemically modified MCC were substantially improved.

The aim of this work is to determine the values of the hardness and elastic modulus of the phases present in CaZrO3-MgO-ZrO2 composites and to analyse their contribution to the composite properties. Two materials previously developed with the same major phases (CaZrO3, MgO and c-ZrO2) present in different volume fractions and grain size have been analysed. The hardness and Young´s modulus of each phase determined by nanoindentation are independent from the specific composite and coincident with nanoindentation values for single phase bulk materials. The contribution of the individual phases to Young´s modulus of the multiphase materials is in agreement with calculations using the nanoindentation values and the Voight upper limit of the “rule of mixtures”. Scale dependence due to microcracking has been observed for microhardness values of the composites and differences between calculations and experimental values are related to this effect., This work was performed in the frame of the CYTEDnetwork HOREF(312RT0453)and was supported by the Spanish Government underprojectMAT2013-48426-C2-1-R.AbílioP.Silvaacknowledges thefinancialsupportofJECSTrustthroughmobilityContract201597 and Instituto de Cerámica y Vidrio–CSIC.

The wear behaviour of a fine grained and dense CaZrO3-MgO composite is presented. Un-lubricated Pin-on-disc tests at room temperature have been performed using 10 N as normal force and 0.10–0.15 ms-1 as sliding rate and ZrO2 and steel counterparts. The coefficient of friction versus the sliding distance and the specific wear, together with a complete microstructural analysis of the worn surfaces by field emission scanning electron microscopy is reported. The composite presents a wear resistance similar to other ceramics under ceramic/ceramic sliding contact and improved wear resistance in contact with steel. Initial wear is dominated by abrasion independently of the chemical nature of the counterpart. The second stage wear depends on the characteristics of the third body formed. Zirconia leads to a brittle particulate third body with little protective capability. Steel forms a strongly bonded and plastic cermet third body that protects the material limiting the level of further wear. Fil: Silva, Abílio. Instituto de Ceramica y Vidrio de Madrid; España. Universidade Beira Interior; Portugal Fil: Booth, Raul Fernando Nicolas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina. Instituto de Ceramica y Vidrio de Madrid; España Fil: Garrido, Liliana Beatriz. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina Fil: Aglietti, Esteban Fausto. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina Fil: Pena, Pilar. Instituto de Ceramica y Vidrio de Madrid; España Fil: Baudín, Carmen. Instituto de Ceramica y Vidrio de Madrid; España

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A new type of luminescent optical fibre sensor for structural health monitoring of composite laminates (CFRP) is proposed. The Nd3+ doped multi-core doubleclad fibre incorporated in composite structure was used as a distributed temperature sensor. The change of luminescence intensity (Nd3+ ions) at the wavelength of 880 nm (4F3/2 → 4I9/2) and 1060 nm (4F3/2 → 4I11/2) was used for internal temperature monitoring. The special construction of optical fibre was used as it assures an efficient pumping mechanism and, at same time, it increases the measuring sensitivity. The linear response with relative sensitivity 0.015 K−1 was obtained for temperature range from 30 up to 75ºC. The manufacturing process of CFRP with embedded optical fibre sensor is also discussed.

Processing and properties of two fine grain and dense CaZrO3-MgO based composites obtained by reaction sintering of pure ZrO2 and dolomite (CaMg(CO3)2) are described. Two dolomites with different levels of impurities were used to fabricate the materials: high purity (impurity content ≈1.2 wt.%, material DBZ) and impure dolomite (impurity content ≈6.12 wt.%, material DNZ). Mixtures (molar 1:1) were attrition milled and the reaction and sintering processes were studied using dynamical techniques (DTA-TG and dilatometry). Adequate sintering schedule was selected using the controlled sintering technique. The role of impurities on the physical characteristics, microstructure and mechanical properties of the obtained composites was analysed. Noticeable changes in microstructure, porosity, grain size and phases, were observed as function of final sintering temperature at 1350, 1400, 1450 °C, and impurity content. The obtained microstructures are discussed on the basis of the phase equilibrium relationships. Fil: Booth, Raul Fernando Nicolas. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina. Instituto de Ceramica y Vidrio de Madrid; España Fil: Garrido, Liliana Beatriz. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina Fil: Aglietti, Esteban Fausto. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Tecnología de Recursos Minerales y Cerámica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Tecnología de Recursos Minerales y Cerámica; Argentina Fil: Silva, Abílio. Instituto de Ceramica y Vidrio de Madrid; España. University of Beira Interior; Portugal Fil: Pena, Pilar. Instituto de Ceramica y Vidrio de Madrid; España Fil: Baudín, Carmen. Instituto de Ceramica y Vidrio de Madrid; España

The design and production of scaffolds for bone tissue regeneration is yet unable to completely reproduce the native bone properties. In the present study new alginate microparticle and microfiber aggregated scaffolds were produced to be applied in this area of regenerative medicine. The scaffolds' mechanical properties were characterized by thermo mechanical assays. Their morphological characteristics were evaluated by isothermal nitrogen adsorption and scanning electron microscopy. The density of both types of scaffolds was determined by helium pycnometry and mercury intrusion porosimetry. Furthermore, scaffolds' cytotoxic profiles were evaluated in vitro by seeding human osteoblast cells in their presence. The results obtained showed that scaffolds have good mechanical and morphological properties compatible with their application as bone substitutes. Moreover, scaffold's biocompatibility was confirmed by the observation of cell adhesion and proliferation after 5 days of being seeded in their presence and by non-radioactive assays.

The experimental investigation has been carried out to evaluate process stability for two rutile types of electrode supplied with two types of DC power sources: traditional 3 phase thyristor and inverter type. Initially to understand the maximum range of outcomes high quality and defective electrodes, with lower arc stability, were selected for both. During welding tests current and voltage signals were recorded separately with the aid of A/D converter and 5 kHz of sampling frequency. On the basis of digital signals obtained from each electrode type and power sources, a number of statistical indicators have been computed. Furthermore voltage and current histograms have been determined (defined as a density distribution of welding arc voltage and current values). Statistical indicators of voltage signals have proved to be more useful for process stability evaluation, particularly mean voltage (Uśr) and histograms as well as voltage coefficient of variation (KvU).

Alumina, with high melting point (2050°C), high hardness and mechanical strength, and excellent abrasion resistance, is one of the most common raw materials used in self-flow refractory castables (SFRC) for monolithic linings and is commercially available in various fine to coarse size classes. However, the performance of the refractory lining depends not only on the properties of its ingredients but also on its easy installation (good flowability). The aim of this work was to evaluate the relationship between the flowability index (FI) of fresh castable and the specific surface area (SSA) of its particles, which is mostly determined by the finer particles content. The results obtained showed that, by controlling the proportion between matrix and aggregate, it is possible to control the SSA of the refractory castable and find a mathematical relationship between the specific surface area and the minimum flowability index required to obtain a self-flow refractory castable. It is, thus, possible to optimize the refractory castable size composition and obtain an estimate for FI as a function of SSA. Using a minimum 45 wt.% matrix content in the castable mixture, a SSA value above 2.215 m2/g is obtained, which leads to FI ≥ 80%, the recommended value for self-flow.

The goal of this research is to choose the proper method of car body welding. Properties of weld metal deposits depend on many conditions. First of all, this paper attempts to study the role of oxide inclusion sites on the transformation of austenite to acicular ferrite in steel weld metal deposits and their toughness. Safety and exploitation conditions of welded steel structure depend on many factors. The most significant of those factors are connected with materials, welding technology, state of stress and temperature. Because of that a good selection of steel and welding method is crucial to obtain proper steel structure. Car body elements of higher durability are made of low carbon and low alloy steel, very often with small amount of carbon and the amount of alloy elements such as Ni, Mn, Mo, Cr and V in low alloy steel and their welds. In the terms of the kind of steel it is used a proper welding method and adequate filler materials. In the present paper the influence of Mn, Ni, Mo, in WMD on the behaviour of steel structure for low temperature service was tested.

The success of a refractory castable is largely due to the quality of its properties and ease of application. Self-flow refractory castables (SFRC), with high flowability index (>130%), can be easily accommodated in a mould without the application of external energy, being ideal for the manufacture of monolithic linings. SFRC castables without cement require a matrix of very fine particles, which guarantees improved rheological behaviour and performs the role of the binder in the absence of the refractory cement. The presence of the aggregate (coarse particles) hinders the flowability index, but improves the castable mechanical strength and reduces firing shrinkage, and also contributes to the reduction of the castable costs. The control of the maximum paste thickness (MPT) allows the reduction of the coarse particles interference, minimizing the number of contact points among the grains and avoiding the formation of an aggregate skeleton that impairs the flowability of the mixture. In the present work, 100% alumina SFRCs without cement were produced with a fixed matrix of fine particles, whose particle size distribution was optimized using statistical techniques (mixtures design and triangular response surfaces). Different aggregate particle size distributions were used, with several MPT values, with the objective of evaluating which was the mean distance that maximized the flowability index, simultaneously ensuring good mechanical strength for the refractory castable. Ensuring a minimum surface area of 2.22m2/g, the mixtures reach the self-flow turning point with a minimum water content and the maximum flowability is obtained for an aggregate particle size distribution modulus of q=0.22, and consequently an optimized MPT value. SFRC with high mechanical strength (>60MPa) were obtained.

This work aims to contribute for the development of bioglass scaffolds to be used in bone tissue regeneration. Starting from the classic quaternarian composition of the bioglass 45s5 it was added potassium oxide and magnesium oxide in order to obtain the optimised system: SiO2-CaO-Na2O-MgO-K2O-P2O5, improving the mechanical resistance and the bioactivity behaviour. The mixture was reached by a fusion at 1500 ºC followed by thermal shock, the resulting bioglass was milled to get a particle size less than 40 µm and it was homogenised with a porogen agent (salt), resulting the pressed specimens at 100 MPa of 100, 60, 50, and 40 wt.% of bioglass. After sintering, bleaching and maturation, it was evaluated the mechanical behaviour, toxicity and bioactivity, proving the viability and potential of this simplified method of scaffold’s manufacture, also putting in evidence the advantages of the using salt as a porogen agent in the morphology and structure obtained.DOI: http://dx.doi.org/10.5755/j01.ms.22.2.8581

In this work, commercial alumina fine powders were used as raw materials, namely two tabular alumina fractions (–500 mesh and –230 mesh) and a reactive alumina. Statistical modelling and the Response Surface Methodology (Statistica, Mixtures Designs and Triangular Surfaces module) were applied to three-component mixtures and used to calculate the various property-composition surfaces. To that aim, the various mixtures were prepared, cast, dried, fired and characterised. The particle size distribution modulus, q, was determined for all mixtures using the software LISA. The various response surfaces were then combined, so that the water content in the mixture could be minimised and the matrix flowability maximised. The properties of the resulting test-bricks (linear shrinkage, mechanical strength, apparent density and porosity) were also modelled and response surfaces were obtained. Combined results enabled the definition of an optimised particle size composition range, which guarantees the presence of a low water flow-bed that enables the aggregate self-flow.

The purpose of this investigation is to evaluate quantitatively and comparatively the effect of embedding optical fibers (OF) on the mechanical behavior of a carbon fiber-epoxy composite in order to verify whether their presence can possibly degrade the mechanical performance of the host material. The existing literature on this subject is not conclusive about the nature and intensity of this effect. Adding more reliable data to our systematic study contributes to this discussion favoring the conclusion about a harmful influence as a consequence of optical fiber embedment. Three kinds of mechanical tests have been performed in this work: impact tests, static flexural tests, and fatigue tests. The results of some experiments point to a possible detrimental influence related to the presence of the OF, being it different in nature and intensity for each of these tests. The mechanical behavior in static loading conditions seems to be not significantly affected as a consequence of the presence of the OF, while that in impact and fatigue tests are strongly affected, even though this influence being physically distinct from each other. Based on these results, some discussion is made about the possible failure mechanisms that can explain the detected differences.

The regeneration of large bone defects remains a challenging scenario from a therapeutic point of view. In fact, the currently available bone substitutes are often limited by poor tissue integration and severe host inflammatory responses, which eventually lead to surgical removal. In an attempt to address these issues, herein we evaluated the importance of alginate incorporation in the production of improved and tunable β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) three-dimensional (3D) porous scaffolds to be used as temporary templates for bone regeneration. Different bioceramic combinations were tested in order to investigate optimal scaffold architectures. Additionally, 3D β-TCP/HA vacuum-coated with alginate, presented improved compressive strength, fracture toughness and Young's modulus, to values similar to those of native bone. The hybrid 3D polymeric-bioceramic scaffolds also supported osteoblast adhesion, maturation and proliferation, as demonstrated by fluorescence microscopy. To the best of our knowledge this is the first time that a 3D scaffold produced with this combination of biomaterials is described. Altogether, our results emphasize that this hybrid scaffold presents promising characteristics for its future application in bone regeneration.

This paper presents the results of the hygrothermal effect on the impact response of carbon/epoxy composites and the benefits gained from doping the epoxy resin with nanoclays previously subjected to a silane treatment appropriate for the resin. The nanoclay reinforcement increased the maximum load and the elastic recovery of the composites. The thermal degradation caused by exposure to 60°C for 10 days was insignificant, while the immersion in water at 60°C for 30 days led to a continuous reduction in the maximum load and the elastic recovery. Multiple impacts resulted in a continuous and nearly linear degradation of the impact response both of dry and environmentally assisted specimens.

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Much has been discussed about the advantages regarding the thermomechanical performance of self-flow refractory castables (SFRC), with very little or no addition of calcium aluminate cement (CAC) when compared to conventional composites with cement. Previous works demonstrated that a 100% alumina SFRC with optimized particle size distribution simultaneously results in high-flowability fresh paste and high mechanical strength. In this work, the thermomechanical behaviour of zero-cement ceramic matrix is compared to that of the equivalent composite with 1% CAC content. The results show that the differences in performance can be related to differences in hydration mechanisms, namely the formation sequence of calcium aluminate hydrates, which results in increased open porosity. With lower dried strength, the all-alumina castable presents lower porosity, higher mechanical strength and uncompromised thermal shock resistance, being a valuable option when fast drying or rough green handling can be avoided.

In this work, alumina powders in five different commercially available size ranges were used to prepare various refractory castable mixtures, defined using the statistical design of mixture experiments (STATISTICA, StatSoft Inc.) and the EMMA 3.3 software (Elkem Materials). Those mixtures were characterized for packing density, Andreasen particle size distribution modulus ( q ), flowability and after sintering properties, in order to investigate the relationships between these variables. The optimization of matrix and aggregate sizes and matrix-aggregate proportion, subjected to different property requirements, brought to light the relationships between q , specific surface area (SSA) and maximum paste thickness (MPT). Those relationships were investigated for three fundamental processing steps, namely, dry powders, fresh paste and consolidated dried and sintered bodies. The optimized all-alumina castable was found to require 47.5 wt.% of a fine size matrix with high flowability, which provides the necessary flow bed for 52.5 wt.% of coarse aggregates, resulting in a gap-sized particle size distribution, and presented a fresh paste flowability index above 130% with minimum added water (28 mg/m 2 ) and sintered modulus of rupture above 50 MPa.

A self-flow refractory castable (SFRC) without cement requires a matrix of fine particles and a broad size distribution of coarse particles (aggregate). The matrix ensures the rheological behaviour and performs the binding role of the absent refractory cement. The presence of the aggregate coarse particles hinders the flowability index (FI), but improves the castable mechanical strength and reduces firing shrinkage. A new methodology of SFRC particle distribution design was developed, using response surface statistical modelling and commercial alumina powders (reactive and tabular). First, the composition of the fine matrix was optimised, seeking minimum water content and maximum IF. To this matrix, various aggregate distributions, combining six tabular alumina size fractions and with different Andreasen distribution modulus, q, between 0.18 to 0.28, were added, to identify the composition with maximum FI. The results obtained show that a minimum specific surface area (SSA) of 2.22m2/g is necessary to reach the self-flow turning point, after which the largest FI requires the maximisation of the aggregate maximum paste thickness (MPT), corresponding to a distribution with q=0.22. The optimised castable composition presents high mechanical strength (>60MPa) and low shrinkage.

In the processing of any particulate system (including refractory castables), the finer sized particle fraction (matrix or filler) is mostly responsible for the final system properties. Alumina fine powders were used in this work as raw materials, namely two tabular alumina fractions (–500 mesh and –230 mesh) and a commercial reactive alumina. Statistical modelling and the Response Surface Methodology (Statistica, Mixtures Designs and Triangular Surfaces module) were used to optimise the particle size composition of the three-component mixtures leading to matrix maximum flowability. The mixing methodology, aimed at minimising the water content, was kept constant. No-cement alumina castables produced with the various fine size powder mixtures, were used to prepare test-pieces. After drying and sintering, their mechanical resistance (MoR), density, porosity, water absorption, thermal shock behaviour and microstructure were evaluated. The results obtained evidenced the relevance of variables such as the water content per unit specific surface area, needed to reach the self-flow “turning point”, and validated the statistical optimisation method used. Moreover those results showed the existence of a matrix composition range, which favours the formation of a flow-bed that enables the aggregate self-flow.

Purpose In this work, an alumina scaffold was produced through a new method to be used in a near future as a bone substitute. Methods In vitro and in vivo studies were performed in order to characterize the mechanical and biological properties of the scaffold. Results The results obtained showed that this scaffold has high mechanical resistance and a porous surface that allows human osteoblast cells to adhere and proliferate. The in vivo studies revealed no systemic reaction. Conclusions The alumina scaffold produced herein has the mechanical and biological properties that are compatible with its application in bone therapy.