A theoretical assessment of surface defect machining and hot machining of nanocrystalline silicon carbide

In this paper, a newly proposed machining method named “surface defect machining” (SDM) [Wear, 302, 2013 (1124-1135)] was explored for machining of nanocrystalline beta silicon carbide (3C-SiC) at 300K using MD simulation. The results were compared with isothermal high temperature machining at 1200K under the same machining parameters, emulating ductile mode micro laser assisted machining (µ-LAM) and with conventional cutting at 300 K. In the MD simulation, surface defects were generated on the top of the (010) surface of the 3C-SiC work piece prior to cutting, and the workpiece was then cut along the <100> direction using a single point diamond tool at a cutting speed of 10 m/sec. Cutting forces, sub-surface deformation layer depth, temperature in the shear zone, shear plane angle and friction coefficient were used to characterize the response of the workpiece. Simulation results showed that SDM provides a unique advantage of decreased shear plane angle which eases the shearing action. This in turn causes an increased value of average coefficient of friction in contrast to the isothermal cutting (carried at 1200 K) and normal cutting (carried at 300K). The increase of friction coefficient however was found to aid the cutting action of the tool due to an intermittent dropping in the cutting forces, lowering stresses on the cutting tool and reducing operational temperature. Analysis shows that the introduction of surface defects prior to conventional machining can be a viable choice for machining a wide range of ceramics, hard steels and composites compared to hot machining.

Modelling and characterization of ultrasonic consolidation process of Aluminium alloys

Ultrasonic consolidation process is a rapid manufacturing process used to join thin layers of metal at low temperatures and low energy consumption. In this work, finite element method has been used to simulate the ultrasonic consolidation of Aluminium alloys 6061 (AA-6061) and 3003 (AA-3003). A thermomechanical material model has been developed in the framework of continuum cyclic plasticity theory which takes into account both volume (acoustic softening) and surface (thermal softening due to friction) effects. A friction model based on experimental studies has been developed, which takes into account the dependence of coefficient of friction upon contact pressure, amount of slip, temperature and number of cycles. Using the developed material and friction model ultrasonic consolidation (UC) process has been simulated for various combinations of process parameters involved. Experimental observations are explained on the basis of the results obtained in the present study. The current research provides the opportunity to explain the differences of the behaviour of AA-6061 and AA-3003 during the ultrasonic consolidation process. Finally, trends of the experimentally measured fracture energies of the bonded specimen are compared to the predicted friction work at the weld interface resulted from the simulation at similar process condition. Similarity of the trends indicates the validity of the developed model in its predictive capability of the process. © 2008 Materials Research Society.

Validation of an ultra high performance liquid chromatography-tandem mass spectrometry method for detection and quantitation of 19 endocrine disruptors in milk

An endocrine disruptor (ED) is an exogenous compound that interferes with the body's endocrine system. Exposure to EDs may result in adverse health effects such as infertility and cancer. EDs are composed of a vast group of chemicals including compounds of natural origin such as phytoestrogens or mycotoxins and a wide range of man-made chemicals such as pesticides. Synthetic compounds may find their way into the food chain where a number of them can biomagnify. Additionally, processing activities and food contact materials may add further to the already existing pool of food contaminants. Thus, our diet is considered to be one of the main exposure routes to EDs. Some precautionary legislation has already been introduced to control production and/or application of some persistent organic pollutants with ED characteristics. However, newly emerging EDs with bioaccumulative properties have recently been reported to appear at lower tiers of the food chain but have not been monitored at the grander scale. Milk and dairy products are a major component of our diet, thus it is important to monitor them for EDs. However, most methods developed to date are devoted to one group of compounds at a time. The UHPLC-MS/MS method described here has been validated according to EC decision 2002/657/EC and allows simultaneous extraction, detection, quantitation and confirmation of 19 EDs in milk. The method calibration range is between 0.50 and 20.0 μg kg with coefficients of determination above 0.99 for all analytes. Precision varied from 4.7% to 23.4% in repeatability and reproducibility studies. Established CCα and CCβ values (0.11-0.67 μg kg) facilitate fast, reliable, quantitative and confirmatory analysis of sub μg kg levels of a range of EDs in milk.

The feasibility of using near infrared and Raman spectroscopic techniques to detect fraudulent adulteration of chili powders with Sudan dye

Chili powder is a globally traded commodity which has been found to be adulterated with Sudan dyes from 2003 onwards. In this study, chili powders were adulterated with varying quantities of Sudan I dye (0.1-5%) and spectra were generated using near infrared reflectance spectroscopy (NIRS) and Raman
spectroscopy (on a spectrometer with a sample compartment modified as part of the study). Chemometrics were applied to the spectral data to produce quantitative and qualitative calibration models and prediction statistics. For the quantitative models coefficients of determination (R2) were found to be
0.891-0.994 depending on which spectral data (NIRS/Raman) was processed, the mathematical algorithm used and the data pre-processing applied. The corresponding values for the root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) were found to be 0.208-0.851%
and 0.141-0.831% respectively, once again depending on the spectral data and the chemometric treatment applied to the data. Indications are that the NIR spectroscopy based models are superior to the models produced from Raman spectral data based on a comparison of the values of the chemometric
parameters. The limit of detection (LOD) based on analysis of 20 blank chili powders against each calibration model gave 0.25% and 0.88% for the NIR and Raman data, respectively. In addition, adopting a qualitative approach with the spectral data and applying PCA or PLS-DA, it was possible to discriminate
between adulterated chili powders from non-adulterated chili powders.

Barrier characteristics of PtSi/p-Si schottky diodes as determined from I-V-T measurements

The current-voltage-temperature characteristics of PtSi/p-Si Schottky barrier diodes were measured in the temperature range 60-115 K. Deviation of the ideality factor from unity below 80 K may be modelled using the so-called T-0 parameter with T-0 = 18 K. It is also shown that the curvature in the Richardson plots may be remedied by using the flatband rather than the zero-bias saturation current density. Physically, the departure from ideality is interpreted in terms of an inhomogeneous Schottky contact. Here we determine a mean barrier height at T = 0 K, phi(b)(-0) = 223 mV, with an (assumed) Gaussian distribution of standard deviation sigma(phi) = 12.5 mV. These data are correlated with the zero-bias barrier height, phi(j)(0) = 192 mV (at T = 90 K), the photoresponse barrier height, phi(ph) = 205 mV, and the flatband barrier height, phi(fb) = 214 mV. Finally, the temperature coefficient of the flatband barrier was found to be -0.121 mV K-1, which is approximately equal to 1/2(dE(g)(i)/dT), thus suggesting that the Fermi level at the interface is pinned to the middle of the band gap.

The use of handheld near-infrared reflectance spectroscopy (NIRS) for the proximate analysis of poultry feed and to detect melamine adulteration of soya bean meal

The use of handheld near infrared (NIR) instrumentation, as a tool for rapid analysis, has the potential to be used widely in the animal feed sector. A comparison was made between handheld NIR and benchtop instruments in terms of proximate analysis of poultry feed using off-the-shelf calibration models and including statistical analysis. Additionally, melamine adulterated soya bean products were used to develop qualitative and quantitative calibration models from the NIRS spectral data with excellent calibration models and prediction statistics obtained. With regards to the quantitative approach, the coefficients of determination (R2) were found to be 0.94-0.99 with the corresponding values for the root mean square error of calibration and prediction were found to be 0.081-0.215 % and 0.095-0.288 % respectively. In addition, cross validation was used to further validate the models with the root mean square error of cross validation found to be 0.101-0.212 %. Furthermore, by adopting a qualitative approach with the spectral data and applying Principal Component Analysis, it was possible to discriminate between adulterated and pure samples.

Development of a rapid multiplexed assay for the direct screening of antimicrobial residues in raw milk

Antimicrobial residues found to be present in milk can have both health and economic impacts. For these reasons, the widespread routine testing of milk is required. Due to delays with sample handling and test scheduling, laboratory-based tests are not always suited for making decisions about raw material intake and product release, especially when samples require shipping to a central testing facility. Therefore, rapid on-site screening tests that can produce results within a matter of minutes are required to facilitate rapid intake and product release processes. Such tests must be simple for use by non-technical staff. There is increasing momentum towards the development and implementation of multiplexing tests that can detect a range of important antimicrobial residues simultaneously. A simple in situ multiplexed planar waveguide device that can simultaneously detect chloramphenicol, streptomycin and desfuroylceftiofur in raw dairy milk, without sample preparation, has been developed. Samples are simply mixed with antibody prior to an aliquot being passed through the detection cartridge for 5 min before reading on a field-deployable portable instrument. Multiplexed calibration curves were produced in both buffer and raw milk. Buffer curves, for chloramphenicol, streptomycin and desfuroylceftiofur, showed linear ranges (inhibitory concentration (IC)₂₀–IC₈₀) of 0.1–0.9, 3–129 and 12–26 ng/ml, whilst linear range in milk was 0.13–0.74, 11–376 and 2–12 ng/ml, respectively, thus meeting European legislated concentration requirements for both chloramphenicol and streptomycin, in milk, without the need for any sample preparation. Desfuroylceftiofur-contaminated samples require only simple sample dilution to bring positive samples within the range of quantification. Assay repeatability and reproducibility were lower than 12 coefficient of variation (%CV), whilst blank raw milk samples (n = 9) showed repeatability ranging between 4.2 and 8.1 %CV when measured on all three calibration curves.

Identification of Peptide Inhibitors of Enveloped Viruses Using Support Vector Machine

The peptides derived from envelope proteins have been shown to inhibit the protein-protein interactions in the virus membrane fusion process and thus have a great potential to be developed into effective antiviral therapies. There are three types of envelope proteins each exhibiting distinct structure folds. Although the exact fusion mechanism remains elusive, it was suggested that the three classes of viral fusion proteins share a similar mechanism of membrane fusion. The common mechanism of action makes it possible to correlate the properties of self-derived peptide inhibitors with their activities. Here we developed a support vector machine model using sequence-based statistical scores of self-derived peptide inhibitors as input features to correlate with their activities. The model displayed 92% prediction accuracy with the Matthew’s correlation coefficient of 0.84, obviously superior to those using physicochemical properties and amino acid decomposition as input. The predictive support vector machine model for self- derived peptides of envelope proteins would be useful in development of antiviral peptide inhibitors targeting the virus fusion process.

Modelling the fresh properties of self-compacting concrete using support vector machine approach

The main objective of the study presented in this paper was to investigate the feasibility using support vector machines (SVM) for the prediction of the fresh properties of self-compacting concrete. The radial basis function (RBF) and polynomial kernels were used to predict these properties as a function of the content of mix components. The fresh properties were assessed with the slump flow, T50, T60, V-funnel time, Orimet time, and blocking ratio (L-box). The retention of these tests was also measured at 30 and 60 min after adding the first water. The water dosage varied from 188 to 208 L/m3, the dosage of superplasticiser (SP) from 3.8 to 5.8 kg/m3, and the volume of coarse aggregates from 220 to 360 L/m3. In total, twenty mixes were used to measure the fresh state properties with different mixture compositions. RBF kernel was more accurate compared to polynomial kernel based support vector machines with a root mean square error (RMSE) of 26.9 (correlation coefficient of R2 = 0.974) for slump flow prediction, a RMSE of 0.55 (R2 = 0.910) for T50 (s) prediction, a RMSE of 1.71 (R2 = 0.812) for T60 (s) prediction, a RMSE of 0.1517 (R2 = 0.990) for V-funnel time prediction, a RMSE of 3.99 (R2 = 0.976) for Orimet time prediction, and a RMSE of 0.042 (R2 = 0.988) for L-box ratio prediction, respectively. A sensitivity analysis was performed to evaluate the effects of the dosage of cement and limestone powder, the water content, the volumes of coarse aggregate and sand, the dosage of SP and the testing time on the predicted test responses. The analysis indicates that the proposed SVM RBF model can gain a high precision, which provides an alternative method for predicting the fresh properties of SCC.

Effect of cation structure on the oxygen solubility and diffusivity in a range of bis{(trifluoromethyl)sulfonyl}imide anion based ionic liquids for lithium-air battery electrolytes

This paper reports on the solubility and diffusivity of dissolved oxygen in a series of ionic liquids (ILs) based on the bis{(trifluoromethyl)sulfonyl}imide anion with a range of related alkyl and ether functionalised cyclic alkylammonium cations. Cyclic voltammetry has been used to observe the reduction of oxygen in ILs at a microdisk electrode and chronoamperometric measurements have then been applied to simultaneously determine both the concentration and the diffusion coefficient of oxygen in the different ILs. The viscosity of the ILs and the calculated molar volume and free volume is also reported. It is found that, within this class of ILs, the oxygen diffusivity generally increases with decreasing viscosity of the neat IL. An inverse relationship between oxygen solubility and IL free volume is reported for the two IL families implying oxygen is not simply occupying the available empty space. In addition, it is reported that the introduction of ether-group into the IL cation structure promotes the diffusivity of dissolved oxygen but reduces the solubility of the gas.

Studies into the effect of temperature on the impact of model particles in co-melt granulation

In co-melt granulation, collisions occur between the particles to be agglomerated and the binder material. Depending on the stage of granulation, the binder material can be in the solid or liquid phase. The outcome of these collisions controls the dynamics of the granulation process and the fundamental physics of the impacts are of interest. This paper examines the impact of glass beads (model particles) and solid Poly Ethylene Glycol (PEG) flakes on a substrate of PEG as the temperature of the PEG layer is increased from below its melting point to above it. While the layer is in the solid state, the result of the impact can be quantified by the coefficient of restitution. When the layer is in the liquid state, the impact can be quantified by the immersion behaviour. The results obtained show that the coefficient of restitution between either glass beads and PEG flakes and the PEG layer is strongly affected by temperatures. As the PEG layer approaches its melting point, the coefficient of restitution falls to zero. Once the temperature of the PEG layer exceeds the melting point, the impact is characterised by a transient maximum indentation and then rebound to an equilibrium position. These too are strongly dependent on temperature.

Auditory cueing in Parkinson's patients with freezing of gait. What matters most: action-relevance or cue-continuity?

Gait disturbances are a common feature of Parkinson’s disease, one of the most severe being freezing of gait. Sensory cueing is a common method used to facilitate stepping in people with Parkinson’s. Recent work has shown that, compared to walking to a metronome, Parkinson’s patients without freezing of gait (nFOG) showed reduced gait variability when imitating recorded sounds of footsteps made on gravel. However, it is not known if these benefits are realised through the continuity of the acoustic information or the action-relevance. Furthermore, no study has examined if these benefits extend to PD with freezing of gait. We prepared four different auditory cues (varying in action-relevance and acoustic continuity) and asked 19 Parkinson’s patients (10 nFOG, 9 with freezing of gait (FOG)) to step in place to each cue. Results showed a superiority of action-relevant cues (regardless of cue-continuity) for inducing reductions in Step coefficient of variation (CV). Acoustic continuity was associated with a significant reduction in Swing CV. Neither cue-continuity nor action-relevance was independently sufficient to increase the time spent stepping before freezing. However, combining both attributes in the same cue did yield significant improvements. This study demonstrates the potential of using action-sounds as sensory cues for Parkinson’s patients with freezing of gait. We suggest that the improvements shown might be considered audio-motor ‘priming’ (i.e., listening to the sounds of footsteps will engage sensorimotor circuitry relevant to the production of that same action, thus effectively bypassing the defective basal ganglia).

An optimized reverse-phase high performance liquid chromatographic method for evaluating percutaneous absorption of glucosamine hydrochloride

A relatively simple, selective, precise and accurate high performance liquid chromatography (HPLC) method based on a reaction of phenylisothiocyanate (PITC) with glucosamine (GL) in alkaline media was developed and validated to determine glucosamine hydrochloride permeating through human skin in vitro. It is usually problematic to develop an accurate assay for chemicals traversing skin because the excellent barrier properties of the tissue ensure that only low amounts of the material pass through the membrane and skin components may leach out of the tissue to interfere with the analysis. In addition, in the case of glucosamine hydrochloride, chemical instability adds further complexity to assay development. The assay, utilising the PITC-GL reaction was refined by optimizing the reaction temperature, reaction time and PITC concentration. The reaction produces a phenylthiocarbamyl-glucosamine (PTC-GL) adduct which was separated on a reverse-phase (RP) column packed with 5 microm ODS (C18) Hypersil particles using a diode array detector (DAD) at 245 nm. The mobile phase was methanol-water-glacial acetic acid (10:89.96:0.04 v/v/v, pH 3.5) delivered to the column at 1 ml min-1 and the column temperature was maintained at 30 degrees C. Galactosamine hydrochloride (Gal-HCl) was used as an internal standard. Using a saturated aqueous solution of glucosamine hydrochloride, in vitro permeation studies were performed at 32+/-1 degrees C over 48 h using human epidermal membranes prepared by a heat separation method and mounted in Franz-type diffusion cells with a diffusional area 2.15+/-0.1 cm2. The optimum derivatisation reaction conditions for reaction temperature, reaction time and PITC concentration were found to be 80 degrees C, 30 min and 1% v/v, respectively. PTC-Gal and GL adducts eluted at 8.9 and 9.7 min, respectively. The detector response was found to be linear in the concentration range 0-1000 microg ml-1. The assay was robust with intra- and inter-day precisions (described as a percentage of relative standard deviation, %R.S.D.) <12. Intra- and inter-day accuracy (as a percentage of the relative error, %RE) was <or=-5.60 and <or=-8.00, respectively. Using this assay, it was found that GL-HCl permeates through human skin with a flux 1.497+/-0.42 microg cm-2 h-1, a permeability coefficient of 5.66+/-1.6x10(-6) cm h-1 and with a lag time of 10.9+/-4.6 h.

SHORT-TERM EFFECTS OF SALINITY ON SOME PHYSIOLOGICAL PARAMETERS OF YOUNG OLIVE TREES OF ARBEQUINA, COBRANÇOSA AND GALEGA VARIETIES

SHORT-TERM EFFECTS OF SALINITY ON SOME PHYSIOLOGICAL PARAMETERS OF YOUNG OLIVE TREES OF ARBEQUINA, COBRANÇOSA AND GALEGA VARIETIES Ana Elisa Rato1,4, Renato Coelho1, Margarida Vaz1, Teresa Carola2, Dália Barbosa2, Nádia Silva1, José dos Santos2, Lourenço Machado2, João Godinho2, Luzia Ruas2, Margarida Barradas2, Hernani Pereira2, Sara Porfírio4 1 ICAAM, Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal 2 Master students, Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal 3 Ph.D. student, Universidade de Évora, Apartado 94, 7002-554 Évora, Portugal 4 aerato@uevora.pt Due to the desertification in some regions, the interest in plant’s tolerance to salinity has been increasing, as this response is determining for plant survival in stress conditions. This work reports the investigation of tolerance to salt in two year-old olive trees (Olea europaea L.) of three varieties, Arbequina, Cobrançosa and Galega vulgar. Plants were grown in 10 L plastic pots containing approximately 9 Kg of a sandy granitic soil, on a greenhouse. For 3 months (from the beginning of February to the end of April 2012), they were subjected to three levels of salinity in the irrigation water, 0 mM, 80 mM and 200 mM NaCl (6 plants per salinity level in a total of 18 plants of each variety),. Stomatal conductance (gs) and relative leaf chlorophyll content were assessed on each plant in February, March and April. Mid-day leaf water potential () and soil salinity were measured at the end of the experiment (April). On average, concerning all treatments and dates of determination, stomatal conductance of Arbequina and Galega vulgar was quite similar, around 40 mmol m-2 s-1, but Cobrançosa had a value of gs 36% higher, almost 50% higher (61 mmol m-2 s-1) when compared with the controls (0 mM salt) of the other two varieties. In percentage of controls, there was little difference in gs between varieties and between salinities during February and March. In contrast, in April, after about 90 days of exposure to salt, there was a clear decrease in gs with salt irrigation, proportional to salt concentration. Compared with controls, plants irrigated with 200 mM salt showed around 80% (Arbequina) or 85% (Cobrançosa and Galega vulgar) decrease in gs. Chlorophyll content of leaves showed less than 5% difference between varieties on the average of all treatments and dates of determination. During the course of this experiment, the salinity levels used did not show any relevant effect on chlorophyll content. Overall, at the end of the experimental period (April), leaf water potential () at midday was significantly higher in Cobrançosa (-1,4 MPa) than in Galega vulgar (-1,7 MPa) or Arbequina (-1,8 MPa), and salt decreased  of control plants (-1,25 MPa) by an average 30% (with 80 mM) and 65% (with 200 mM). At the end of the experiment, salinity in the soil irrigated with 0 mM, 80 mM or 200 mM NaCl was, on average of all varieties, 0,2 mS, 1,0 mS or 2,0 mS, respectively. Soil salinity was quite similar in Arbequina and Galega vulgar but about 35% lower in the pots of Cobrançosa, on average of all salt-irrigation levels. Plants of Cobrançosa had higher stomatal conductance, however they showed higher water potential and lower salinity in the soil. These apparently contradictory results seem to suggest that Cobrançosa responds to salt differently from the other two varieties. This issue needs further investigation.

Microstructure design of Titanate-based electroceramics

Electrocerâmicos são uma classe de materiais avançados com propriedades eléctricas valiosas para aplicações. Estas propriedades são geralmente muito dependentes da microestrutura dos materiais. Portanto, o objectivo geral deste trabalho é investigar o desenho da resposta dieléctrica de filmes espessos obtidos por Deposição Electroforética (EPD) e cerâmicos monolíticos, através do controlo da evolução da microestrutura durante a sinterização de electrocerâmicos à base de titanatos. Aplicações sem fios na indústria microelectrónica e de comunicações, em rápido crescimento, tornaram-se um importante mercado para os fabricantes de semicondutores. Devido à constante necessidade de miniaturização, redução de custos e maior funcionalidade e integração, a tecnologia de filmes espessos está a tornar-se uma abordagem de processamento de materiais funcionais cada vez mais importante. Uma técnica adequada neste contexto é EPD. Os filmes espessos resultantes necessitam de um passo subsequente de sinterização que é afectada pelo substrato subjacente, tendo este um forte efeito sobre a evolução da microestrutura. Relacionado com a miniaturização e a discriminação do sinal, materiais dieléctricos usados como componentes operando a frequências das microondas em aplicações na industria microelectrónica de comunicações devem apresentar baixas perdas dieléctricas e elevadas permitividade dieléctrica e estabilidade com a temperatura. Materiais do sistema BaO-Ln2O3- TiO2 (BLnT: Ln = La ou Nd), como BaLa4Ti4O15 (BLT) e Ba4.5Nd9Ti18O54 (BNT), cumprem esses requisitos e são interessantes para aplicações, por exemplo, em estações de base para comunicações móveis ou em ressonadores para telefones móveis, onde a miniaturização dos dispositivos é muito importante. Por sua vez, o titanato de estrôncio (SrTiO3, STO) é um ferroeléctrico incipiente com constante dieléctrica elevada e baixas perdas, que encontra aplicação em, por exemplo, condensadores de camada interna, tirando partido de fronteiras de grão altamente resistivas. A dependência da permitividade dieléctrica do campo eléctrico aplicado torna este material muito interessante para aplicações em dispositivos de microondas sintonizáveis. Materiais à base de STO são também interessantes para aplicações termoeléctricas, que podem contribuir para a redução da actual dependência de combustíveis fósseis por meio da geração de energia a partir de calor desaproveitado. No entanto, as mesmas fronteiras de grão resistivas são um obstáculo relativamente à eficiência do STO para aplicações termoeléctricas. Para além do efeito do substrato durante a sinterização constrangida, outros factores, como a presença de fase líquida, a não-estequiometria ou a temperatura de sinterização, afectam significativamente não apenas a microestrutura dos materiais funcionais, mas também a sua resposta dieléctrica. Se adequadamente compreendidos, estes factores podem ser intencionalmente usados para desenhar a microestrutura dos electrocerâmicos e, desta forma, as suas propriedades dieléctricas. O efeito da não-estequiometria (razão Sr/Ti 0.995-1.02) no crescimento de grão e resposta dieléctrica de cerâmicos de STO foi investigado neste trabalho. A mobilidade das fronteiras de grão aumenta com a diminuição da razão Sr/Ti. A resistividade do interior dos grãos e das fronteiras de grão é sistematicamente diminuída em amostras não-estequiométricas de STO, em comparação com o material estequiométrico. O efeito é muito mais forte para as fronteiras de grão do que para o seu interior. Dependências sistemáticas da não-estequiometria foram também observadas relativamente à dependência da condutividade da temperatura (muito mais afectada no caso da contribuição das fronteiras de grão), à capacitância do interior e fronteiras de grão e à espessura das fronteiras de grão. Uma anomalia no crescimento de grão em cerâmicos de STO ricos em Ti foi também observada e sistematicamente analisada. Foram detectadas três descontinuidades na dependência do tipo Arrhenius do crescimento de grão relativamente à temperatura com diminuições no tamanho de grão a temperaturas em torno de 1500, 1550 e 1605 °C. Além disso, descontinuidades semelhantes foram também observadas na dependência da energia de activação relativamente à condutividade das fronteiras de grão e na espessura das fronteiras de grão, avaliadas por Espectroscopia de Impedância. Estas notáveis coincidências suportam fortemente a formação de diferentes complexos de fronteira de grão com transições entre os regimes de crescimento de grão observados, que podem ser correlacionados com diferentes mobilidades de fronteira de grão e propriedades dieléctricas. Um modelo é sugerido, que se baseia na diminuição da fase líquida localizada nas fronteiras de grão, como o aumento da temperatura de sinterização, um cenário compatível com um fenómeno de solubilidade retrógrada, observado anteriormente em metais e semicondutores, mas não em cerâmicos. A EPD de filmes espessos de STO em substratos de folha de Pt e a sinterização constrangida dos filmes fabricados foram também preliminarmente tratadas. Filmes espessos de STO foram depositados com êxito por EPD sobre substratos de Pt e, depois de sinterizados, atingiram densidades elevadas. Um aumento da densificação e do tamanho de grão assim como o alargamento da distribuição de tamanho do grão foram observados com a diminuição da razão Sr/Ti, tal como anteriormente observado em amostras cerâmicas. Grãos equiaxiados foram observados para todas as composições, mas um certo grau de anisotropia na orientação dos poros foi detectado: os poros revelaram uma orientação vertical preferencial. Este trabalho focou-se também na sinterização constrangida do sistema BLnT (Ln = La ou Nd), nomeadamente de filmes espessos de BLT e BNT sobre substratos de folha de platina, e na relação do desenvolvimento de anisotropia microestrutural com as propriedades dieléctricas. As observações durante a sinterização constrangida foram comparadas com cerâmicos monolíticos equivalentes sinterizados livremente. Filmes espessos de BLnT (Ln = La ou Nd) com elevada densidade foram obtidos por EPD e subsequente sinterização constrangida. A anisometria cristalográfica do material em conjunto com um passo de sinterização constrangida resultou em grãos alongados e microestruturas anisotrópicas. O efeito do stress do substrato durante a sinterização constrangida originou graus mais elevados de anisotropia (grãos e poros alongados e orientação preferencial, bem como textura cristalográfica) nos filmes sinterizados relativamente aos cerâmicos equivalentes sinterizados livremente, não obstante o estado equivalente das amostras em verde. A densificação dos filmes de BLnT (Ln = La ou Nd) é retardada em comparação com os cerâmicos, mas depois de longos tempos de sinterização densidades semelhantes são obtidas. No entanto, em oposição a observações na sinterização constrangida de outros sistemas, o crescimento do grão em filmes de BLnT (Ln = La ou Nd) é favorecido pelo constrangimento causado pelo substrato. Além disso, grãos e poros alongados orientados paralelamente ao substrato foram desenvolvidos durante a sinterização constrangida de filmes espessos. Verificou-se uma forte correlação entre a evolução de grãos e poros, que começou assim que o crescimento do grão se iniciou. Um efeito da tensão do substrato no aumento do crescimento de grão, bem como um forte “Zener pinning”, origina microestruturas altamente texturizadas, o que também é observado a nível cristalográfico. Efeitos marcantes da anisotropia microestrutural foram também detectados nas propriedades dieléctricas dos filmes de BLnT (Ln = La ou Nd). Juntamente com o aumento da razão de aspecto dos grãos, do factor de orientação e do grau de textura cristalográfica, a permitividade relativa é ligeiramente diminuída e o coeficiente de temperatura da permitividade evolui de negativo para positivo com o aumento do tempo isotérmico de sinterização. Este trabalho mostra que a não-estequiometria pode ser usada para controlar a mobilidade das fronteiras de grão e, portanto, desenhar a microestrutura e as propriedades dieléctricas de electrocerâmicos à base de STO, com ênfase nas propriedades das fronteiras de grão. O papel da não-estequiometria no STO e dos complexos de fronteira de grão no desenvolvimento microestrutural é discutido e novas oportunidades para desenhar as propriedades de materiais funcionais são abertas. As observações relativamente à sinterização constrangida apontam para o efeito de tensões mecânicas desenvolvidas devido ao substrato subjacente no desenvolvimento da microestrutura de materiais funcionais. É assim esperado que a escolha adequada de substrato permitia desenhar a microestrutura de filmes espessos funcionais com desempenho optimizado. “Stress Assisted Grain Growth” (SAGG) é então proposto como uma técnica potencial para desenhar a microestrutura de materiais funcionais, originando microestruturas anisotrópicas texturizadas com propriedades desejadas.