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K0.5Na0.5NbO3 (KNN) of 4‐μm average particle size was flash sintered in parallel plate capacitor configuration (PPCC) under 100 V/mm (0.8 mA/mm2 cut‐off) with 10°C/min heating rate in air. Precipitous densification occurred from Tf = 662–670°C (Tf–furnace temperature) in 60 s with 55 mW/mm3 peak power absorption at Tf = 667°C, resulting in 98% dense ceramic of < 5‐μm grains size. No grain growth was observed. A cubic grain morphology was inherited from the starting KNN powder. No sign of liquid phase formation on grain boundaries (GBs) was detected. A 147°C rise above Tf = 667°C due to Joule heating is predicted. At 25°C and 1 kHz, relative permittivity (εr) and dielectric loss (tan(δ)) are 4096 and 2.9%, respectively. From 0.1 to 100 kHz, εr and tan(δ) undergo relaxation, reaching εr = 577 and tan(δ) = 0.2% at 1000 kHz. Variation of εr with temperature revealed Amm2 → P4mm and P4mm → Pm3m transitions at ∼204°C and 409°C, respectively. As per Curie–Weiss analysis, Curie temperature and Curie–Weiss constant are θ = 375°C and C = 3.1 × 10−5°C for the P4mm → Pm3m transition, respectively. The transition is first order as Ttr > θ with a diffusiveness exponent γ = 1.04, indicating normal ferroelectric behavior. The low‐frequency dielectric relaxation is attributed to the space charge in the vicinity of GBs, which is a remnant of flash sintering. Joule heating cannot alone account for the densification in 60 s, which we substantiate within the framework of phase equilibrium and diffusion kinetics. We conjecture that oxygen vacancies start ionizing at Tf = 662°C, couple with the applied electric field via the Lorentz force, and increase their electrochemical potential, causing ultrafast densification. The effects of sample shape, size, and PPCC contributing to high sintered density are also discussed. [ABSTRACT FROM AUTHOR]

Nonisothermal densification in 8% yttria doped zirconia (8YSZ) particulate matter of 250 nm median particle size was studied under 215 V/cm dc electric field and 9 °C/min heating rate, using time-resolved in-situ high temperature energy dispersive x-ray diffractometry with a polychromatic 200 keV synchrotron probe. Densification occurred in the 876-905 °C range, which resulted in 97% of the theoretical density. No local melting at particle-particle contacts was observed in scanning electron micrographs, implying densification was due to solid state mass transport processes. The maximum current draw at 905 °C was 3 A, corresponding to instantaneous absorbed power density of 570 W/cm3. Densification of 8YSZ was accompanied by anomalous elastic volume expansions of the unit cell by 0.45% and 2.80% at 847 °C and 905 °C, respectively. The anomalous expansion at 905 °C at which maximum densification was observed is characterized by three stages: (I) linear stage, (II) anomalous stage, and (III) anelastic recovery stage. The densification in stage I (184 s) and II (15 s) was completed in 199 s, while anelastic relaxation in stage III lasted 130 s. The residual strains ([variant_greek_epsilon]) at room temperature, as computed from tetragonal (112) and (211) reflections, are [variant_greek_epsilon](112) = 0.05% and [variant_greek_epsilon](211) = 0.13%, respectively. Time dependence of (211) and (112) peak widths (β) show a decrease with both exhibiting a singularity at 905 °C. An anisotropy in (112) and (211) peak widths of {β(112)/β(211)} = (3:1) magnitude was observed. No phase transformation occurred at 905 °C as verified from diffraction spectra on both sides of the singularity, i.e., the unit cell symmetry remains tetragonal. We attribute the reduction in densification temperature and time to ultrafast ambipolar diffusion of species arising from the superposition of mass fluxes due to Fickian diffusion, thermodiffusion (Soret effect), and electromigration, which in turn are a consequence of a superposition of chemical, temperature, and electrical potential gradients. On the other hand, we propose defect pile-up at particle-particle contacts and subsequent tunneling as a mechanism creating the 'burst-mode' discontinuous densification at the singularities observed at 847 and 905 °C. [ABSTRACT FROM AUTHOR]

Hypereutectic 0.8MgO-0.2Y2O3 nanocomposites were studied using high pressure and high temperature in situ synchrotron energy dispersive x-ray diffractometry at 5.5 GPa and 1273 K. Polymorphic transformations in the Y2O3 phase, which resulted in a quadruple phase equilibria among cubic, hexagonal, and monoclinic phases with cubic MgO, were observed at 298 K under 5.5 GPa-a pressure much smaller than the pressures at which polymorphic transitions in macroscopic Y2O3. Time-resolved diffractometry at (1273 K, 5.5 GPa, 120 min) revealed a 0.87% expansive volumetric lattice strain in MgO, and is attributed to solid solution formation with Y2O3 which is otherwise absent at ambient conditions. The residual MgO unit cell volume expansion is 0.69% at 298 K, which is indicative that yttrium remained in solid solution. The macroscopic shrinkage due to densification at (1273 K, 5.5 GPa, 120 min) is 3.45% by volume. The partial molar volume of Y3+ in the solid solution is smaller than its molar volume in the pure state per thermodynamic considerations. The importance of repulsion among O2- ions in the immediate vicinity of a Mg2+ vacancy as well as misfit strain due to differences in ionic radii upon Y3+ substitution on Mg2+ sites is presented. A self-consistent model and explanation for the observed concomitant occurrence of cubic → monoclinic and cubic → hexagonal polymorphic transitions in Y2O3 and their stabilization at room temperature is proposed. [ABSTRACT FROM AUTHOR]

We study the temperature and pressure dependence of phase evolution in the 0.5MgO-0.5Y2O3 nanocomposite system using a diamond anvil apparatus in conjunction with in situ synchrotron energy dispersive x-ray diffraction at 7 GPa hydrostatic pressure. At (298 K, 7.0 GPa), structural transformations in the Y2O3 phase are observed, giving rise to the co-existence of its cubic, hexagonal, and monoclinic polymorphs together with cubic MgO. An increase in temperature to 1273 K causes the crystallinity of the Y2O3 hexagonal and monoclinic phases to increase. Isothermal and isobaric hold at (1273 K, 7.0 GPa) for 60 min results in yttrium dissolution in cubic MgO, causing ∼1.0% expansive volumetric lattice strain despite the large differences in the ionic radii of the cations. Cooling the nanocomposite to (298 K, 0 GPa) after a 60 min soak yields four phase co-existence among cubic MgO and cubic, hexagonal, and monoclinic Y2O3. The residual MgO unit cell volume expansion is 0.69% at 298 K, indicating solid solution formation at room temperature despite large differences in the ionic radii of Mg2+ and Y3+. The macroscopic shrinkage due to densification is 3% by volume. Thermodynamic considerations suggest that the relative molar partial volume of Y3+ in MgO is a negative quantity, indicating that the partial molar volume of Y3+ in the solid solution is smaller than its molar volume in the pure state. Aging of the nanocomposites for 240 h does not change the observed 4 phase co-existence. We propose a crystallographic model in which the observed volumetric expansion of the MgO unit cell is primarily attributed to two hydrostatic expansive strain components accompanying solid solution formation: (i) Coulomb repulsion among O2- ions in the immediate vicinity of Mg2+ vacancies, and (ii) misfit strain due to differences in ionic radii upon Y3+ substitution on Mg2+ sites. [ABSTRACT FROM AUTHOR]

Elastic and plastic strain evolution under four-point bending has been studied by synchrotron energy dispersive x-ray diffraction. Measured strain profiles across the specimen thickness showed an increasing linear elastic strain gradient under increasing four-point bending load up to ∼2 kN. The bulk elastic modulus of Ti–6Al–4V was determined as 118 GPa. The onset of plastic deformation was found to set in at a total in-plane strain of ∼0.008, both under tension and compression. Plastic deformation under bending is initiated in the vicinity of the surface and at a stress of 1100 MPa, and propagates inward, while a finite core region remains elastically deformed up to 3.67 kN loading. The onset of the plastic regime and the plastic regime itself has been verified by monitoring the line broadening of the (100) peak of α-Ti. The effective compression/tension stress-strain curve has been obtained from the scaling collapse of strain profile data taken at seven external load levels. A similar multiple load scaling collapse of the plastic strain variation has also been obtained. The level of precision in strain measurement reported herein was evaluated and found to be 1.5×10-5 or better. [ABSTRACT FROM AUTHOR]

We examine the electromechanical displacement of piezoelectric-electrostrictive monolithic bilayer composites with various piezoelectric volume percentage obtained by cosintering piezoelectric 0.65Pb(Mg1/3Nb2/3)O3-0.35PbTiO3 and electrostrictive 0.9Pb(Mg1/3Nb2/.3)O3-0.1PbTiO3 under unipolar and bipolar electric field excitation up to 10 kV/cm experimentally. It is shown that the effective d33 of the composites is limited by the electrostrictive layer, which acts as a capacitor in series to the piezoelectric layer, causing incomplete poling. We show that by controlling the volume content of the piezoelectric layer and constraining it with an electrostrictor, substantial strain amplification (15 μm for bipolar excitation) can be achieved while inducing asymmetry to the displacement with respect to the polarity of the applied field, which we discuss in the context of symmetry superposition. [ABSTRACT FROM AUTHOR]

We report the growth of single-phase (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrRuO3 coated <001> oriented SrTiO3 substrates by using pulsed laser deposition. Films grown at 600 °C under low laser fluence exhibit a <001> textured columnar grained nanostructure, which coalesce with increasing deposition temperature, leading to a uniform fully epitaxial highly stoichiometric film at 750 °C. However, films deposited at lower temperatures exhibit compositional fluctuations as verified by Rutherford backscattering spectroscopy. The epitaxial films of 400–600 nm thickness have a room temperature relative permittivity of ∼750 and a loss tangent of ∼6% at 1 kHz. The room temperature remnant polarization of the films is 4 μC/cm2, while the saturation polarization is 7.1 μC/cm2 at 24 kV/cm and the coercive field is ∼7.3 kV/cm. The results indicate that approximately 50% of the bulk permittivity and 20% of bulk spontaneous polarization can be retained in submicron epitaxial KNN-LT-LS thin film, respectively. The conductivity of the films remains to be a challenge as evidenced by the high loss tangent, leakage currents, and broad hysteresis loops. [ABSTRACT FROM AUTHOR]

It is thought that upper body dynamic strength and shoulder isokinetic parameters are related with freestyle swimming performance. The purpose of this study was to investigate relationships of freestyle swimming performance with dynamic strength parameters and shoulder isokinetic parameters. Nine male swimmers of Anadolu University Swimming Team [age (year)= 22.9±2.7, body height (cm)= 170.0±5.25, body weight (kg)= 74.1±7.0, BMI= 22.0±2.62 (kg/m²); body fat percent (%)= 12.4±4.9] voluntary participated to the study. Freestyle swimming performances (25m and 50m) were tested by a touchpad chronometer system for a semi-Olympic swimming pool (25m). One repetition maximal test for bench press, clean, and push press was used as upper body dynamic strength parameters. Shoulder isokinetic parameters at 60, 180, and 300°.s-1 angular velocities were extension peak torque, flexion peak torque, and flexion/extension peak torque rate of shoulders. Relationships of freestyle swimming performance with upper body dynamic strength parameters and shoulder isokinetic parameters were analysed with Pearson Correlation Coefficient. Probability level was ≤0.05. The results of this study showed that there were no statistically correlations of freestyle swimming performance with upper body dynamic strength parameters and shoulder isokinetic parameters at 60, 180, and 300°.s-1 angular velocities. In conclusion, there are more studies about different angular velocities of shoulder isokinetic parameters and maximal strength of upper body parameters. [ABSTRACT FROM AUTHOR]

We propose a new type of flextensional actuator comprised of an electcomechanically active element which is a piezoelectric-electrostrictive monolithic bi-layer composite (PE-MBLC) capped by truncated thin brass sheets. The PE-MBLC contains equal amounts of 0.65 {Pb(Mg1/3Nb2/3) O3}-0.35PbTiO3 and 0.9{Pb(Mg1/3Nb2/3)O3}-0.1PhTiO3 by volume, and is obtained by a co-sintering process. With applied Emax = 10 kV/cm unipolac drive, the maximum axial displacement (u33) produced by the uncapped and capped PE-MBLC is 11 and 21 μm, empectively. The hysteresis in unipolar u33 at 0.5 Emax is 4.6% for the uncapped PE-MBLC, while that for the capped one is 11%. Under bipolar excitation, the maximum u33 for uncapped is 11.6 μm at +Emax and 6.6 μm at -Emax with as asymmetry factor (ξ) of 1.75 for which u33 < 0 for all E < 0. Under bipolar exsitation, the maximum u33 at +Emax for the capped PE-MBLC is 19 μm while that for -Emax is 8 μm with ξ = 2.4, for which u33 > 0 at -Emax but is smaller than the u33 at +Emax. The origins of the observed asymmetry in u33 are discussed in the context of symmetry superposition and deformation mechanics of the endcaps. [ABSTRACT FROM AUTHOR]

Oxygen partial pressure (PO2) in pulsed laser deposition significantly influences the composition, microstructure, and electrical properties of epitaxial misfit strain-relieved 450 nm <001> oriented epitaxial (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrRuO3 coated SrTiO3. Films deposited at 400 mTorr exhibit high remnant and saturated polarization of 7.5 and 16.5 μC/cm2, respectively, which is ∼100% increase over the ones grown at 100 mTorr. The dielectric constant linearly increases from 220 to 450 with increasing PO2. The observed changes in surface morphology of the films and their properties are shown to be due to the suppression of volatile A-site cation loss. [ABSTRACT FROM AUTHOR]

Oxygen partial pressure (PO2) in pulsed laser deposition significantly influences the composition, microstructure, and electrical properties of epitaxial misfit strain-relieved 450 nm <001> oriented epitaxial (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films on SrRuO3 coated SrTiO3. Films deposited at 400 mTorr exhibit high remnant and saturated polarization of 7.5 and 16.5 μC/cm2, respectively, which is ∼100% increase over the ones grown at 100 mTorr. The dielectric constant linearly increases from 220 to 450 with increasing PO2. The observed changes in surface morphology of the films and their properties are shown to be due to the suppression of volatile A-site cation loss. [ABSTRACT FROM AUTHOR]

Single phase, epitaxial, <001> oriented, undoped and 1 mol % Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films of 400 nm thickness were synthesized on SrRuO3 coated SrTiO3. Such films exhibit well saturated hysteresis loops and have a spontaneous polarization (Ps) of 10 μC/cm2, which is a 150% higher over the Ps of the undoped composition. The coercive field of 1 mol % Mn doped films is 13 kV/cm. Mn-doping results in three orders of magnitude decrease in leakage current above 50 kV/cm electric field, which we attribute to the suppression of intrinsic p-type conductivity of undoped films by Mn donors. [ABSTRACT FROM AUTHOR]

Single phase, epitaxial, <001> oriented, undoped and 1 mol % Mn-doped (K0.44,Na0.52,Li0.04)(Nb0.84,Ta0.10,Sb0.06)O3 thin films of 400 nm thickness were synthesized on SrRuO3 coated SrTiO3. Such films exhibit well saturated hysteresis loops and have a spontaneous polarization (Ps) of 10 μC/cm2, which is a 150% higher over the Ps of the undoped composition. The coercive field of 1 mol % Mn doped films is 13 kV/cm. Mn-doping results in three orders of magnitude decrease in leakage current above 50 kV/cm electric field, which we attribute to the suppression of intrinsic p-type conductivity of undoped films by Mn donors. [ABSTRACT FROM AUTHOR]

We study the temperature dependence of dielectric constant (K) and spontaneous polarization (Ps) in the range of -95–200 °C. Cubic (C)-tetragonal (T) and T-orthorhombic (O) transitions are observed at 264 and 25 °C, respectively. The Curie–Weiss temperature of C-T transition is 249 °C, indicating it is first order. X-ray data indicate T-O phase coexistence at 25 °C. A singularity in Ps at 25 °C and a T-O phase coexistence spanning 25–31 °C was observed, wherein Ps increases from 17×10-2 C/m2 at 31 °C to 23×10-2 C/m2 25 °C. The transition at 25 °C appears diffusionless and polymorphic with martensite start and finish temperatures of 31 and 25 °C, respectively. The maximum in d33 is 345 pC/N and is attributed to the instability at 25 °C, where Ps and K show singularity. [ABSTRACT FROM AUTHOR]

K0.5Na0.5NbO3 (KNN) of 4‐μm average particle size was flash sintered in parallel plate capacitor configuration (PPCC) under 100 V/mm (0.8 mA/mm2 cut‐off) with 10°C/min heating rate in air. Precipitous densification occurred from Tf = 662–670°C (Tf–furnace temperature) in 60 s with 55 mW/mm3 peak power absorption at Tf = 667°C, resulting in 98% dense ceramic of < 5‐μm grains size. No grain growth was observed. A cubic grain morphology was inherited from the starting KNN powder. No sign of liquid phase formation on grain boundaries (GBs) was detected. A 147°C rise above Tf = 667°C due to Joule heating is predicted. At 25°C and 1 kHz, relative permittivity (εr) and dielectric loss (tan(δ)) are 4096 and 2.9%, respectively. From 0.1 to 100 kHz, εr and tan(δ) undergo relaxation, reaching εr = 577 and tan(δ) = 0.2% at 1000 kHz. Variation of εr with temperature revealed Amm2 → P4mm and P4mm → Pm3m transitions at ∼204°C and 409°C, respectively. As per Curie–Weiss analysis, Curie temperature and Curie–Weiss constant are θ = 375°C and C = 3.1 × 10−5°C for the P4mm → Pm3m transition, respectively. The transition is first order as Ttr > θ with a diffusiveness exponent γ = 1.04, indicating normal ferroelectric behavior. The low‐frequency dielectric relaxation is attributed to the space charge in the vicinity of GBs, which is a remnant of flash sintering. Joule heating cannot alone account for the densification in 60 s, which we substantiate within the framework of phase equilibrium and diffusion kinetics. We conjecture that oxygen vacancies start ionizing at Tf = 662°C, couple with the applied electric field via the Lorentz force, and increase their electrochemical potential, causing ultrafast densification. The effects of sample shape, size, and PPCC contributing to high sintered density are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, it is intended to make the mechanical design of 3 axis Computer Numerical Control (CNC) router with linear joints, production of electronic control interface cards and drivers and manufacturing of CNC router system which is a combination of mechanics and electronics. At the same time, interface program has been prepared to control router via USB. The router was developed for educational purpose. In some vocational schools and universities, Computer Aided Manufacturing (CAM) courses are though rather theoretical. This situation cause ineffective and temporary learning. Moreover, students at schools which have the opportunity to apply for these systems can face with various dangerous accidents. Because of this situation, these students start to get knowledge about this system for the first time. For the first steps of CNC education, using smaller and less dangerous systems will be easier. A new concept CNC machine and its user interface suitable and profitable for education have been completely designed and realized during this study. To test the validity of the hypothesis which the benefits that may exist on the educational life, enhanced traditional education method with the contribution of the designed machine has been practiced on CAM course students for a semester. At the end of the semester, the new method applied students were more successful in the rate of 27.36 percent both in terms of verbal comprehension and exam grades.