Penetration Depth Dp Research Articles

Effect of surface burnishing process with different strain paths on the copper microstructure

The single strain path (SSP) and the reciprocating strain path (RSP) machining are performed on the sample surface with a multi-ball surface burnishing tool to study the effect of different deformation modes on the microstructure. The samples are characterized mechanically and metallographically via a microhardness tester, an optical microscope, and a backscattered scanning electron microscope. The effect of the two strain paths on the plastic strain in the material is explored by developing a numerical simulation model. The characterization and simulation results show that the deformation layer thicknesses are 79 μm, 208 μm, and 290 μm for the SSP treated samples and 108 μm, 191 μm, and 305 μm for the SSP models at penetration depths Dp of 30 μm, 60 μm, and 90 μm, and meantime, 195 μm, 249 μm and, 390 μm for the RSP treated samples and 146 μm, 248 μm, and 396 μm for the RSP models. Moreover, the RSP treated samples are harder than the SSP treated samples at the same penetration depth Dp, attributed to the smaller grain size and longer total length of grain boundaries of the RSP treated samples. The simulation results show that the RSP machining, with the assistance of the Bauschinger effect, further increases the strain degree and the machining influence depth in the sample compared with the SSP machining. The RSP machining disintegrates the dislocation cells in collaboration with the Bausinger effect, which causes the shielding effect of long-range stress to be significantly reduced, further transferring machining stress to the sample interior. It is the main reason why the RSP machining leads to deeper affecting depth. Furthermore, the grain boundaries in the fine-grain layer of the RSP and SSP treated samples are mainly dominated by high angle grain boundaries, supplemented by low angle grain boundaries, with a smaller percentage of twin boundaries, while in the coarse-grain layer are mainly twin boundaries, supplemented by high angle grain boundaries, with a smaller percentage of low angle grain boundaries. The micro-textures of the samples machined by the two strain paths are minor differences, but the grains in the subsurface layers produced different grain rotations.

Preparation of high solid loading and low viscosity ceramic slurries for photopolymerization-based 3D printing

In this study, high solid loading and low viscosity cordierite slurries are successfully developed for the first time for photopolymerization-based additive manufacturing. The processability of the slurries is mainly determined by their rheological properties and photocuring parameters. The slurry preparation involves the orthogonal optimization of compositions in order to achieve suitable viscosity, stability and homogeneity. The photocuring parameters of the as-prepared slurries, including penetration depth Dp and critical exposure Ec, are also determined experimentally. Results show that viscosity increases with reduction in particle size. A higher solid-volume fraction also results in an exponential growth in viscosity. As for the dispersant amount, a concentration of 5 wt% leads to the lowest viscosity. Particle size also play an important role in the solid loading capacity of the slurries, as results suggest that smaller particles improve performance. In terms of the photocuring behaviors, the addition of 2 wt% photoinitiator generates an optimal curing process. 40 vol% solid loading leads to the thickest curing depth for all slurries with different types of particle sizes. Finally, a cordierite part with a complex hollow structure and a fine resolution is successfully fabricated. The present study offers a material basis for the polymerization-based 3D printing of porous cordierite structures.

Activation of kaolin with minimum solvent consumption by microwave heating

AbstractA kaolin clay was activated with 1.0 M H2SO4 solution at minimum liquid to solid ratio (L/S) using microwave heating. The optimum experimental conditions for activation were L/S ratio 3.0 mL 1 M H2SO4 per gram kaolin, microwave input power 500–600 W, and heating time 5–10 min. Activation at L/S < 3.0 mL/g using 1.0 M H2SO4 was not efficient, indicating the influence of solvent for absorbing microwaves more intensively and thus improving activation. Significant physicochemical changes were observed by the proposed procedure with smaller volumes of activator compared to the conventional heating method. Microwave input power and heating time have a strong influence on the quality of the final material; activation at high input power (>700 W) and longer heating times (>10 min.) are not recommended since they cause dissolution of kaolinite structure. Microwave-heated kaolin manifested better adsorption for tartrazine dye due to improvements in textural and chemical properties of kaolinite. Moreover, irradiation of used kaolinite has significantly improved dye desorption, increasing the importance of microwaves in regeneration/recycling studies. Detailed dielectric measurements of kaolin-acid mixtures recorded at frequencies much lower than 2.45 GHz revealed that absorption of radiation is highly dependent on the activator solution in the mixture. For 3.0 mL/g mixtures, high dielectric constant ε’ 5223, dielectric loss factor ε” 5083, tangent loss tan d 1.30, penetration depth dp 0.57 cm at (103 Hz), and AC-conductivity σ 0.032 Om–1 were determined at 105 Hz. Filling the pores of kaolin by acid solution increased the microwave absorption and hence de-alumination of kaolinite.

Fast activation of natural biomasses by microwave heating

Microwave was effectively applied as a fast heating tool for activating two natural biomasses, pine wood and Arabica coffee residues. The heated biomasses were tested for removing four food dyes: Allura Red E129, Sunset Yellow E110, Tartrazine E102, and Brilliant Black E151 from solution. The biomasses were heated by 2.45GHz microwaves at different input powers 200–1000W for 8min. The results indicated that heating at high input powers is necessary to activate biomasses and to enhance dyes adsorption. Dielectrical properties (dielectric constant ɛ′, dielectric loss ɛ″, tangent loss tanδ, and penetration depth dp) indicated that Arabica coffee is a better microwave absorber leading to significant structural damage when heating at high input powers. Microwave-heated pine wood showed a better performance for dyes removal compare to coffee residue. Heating at 1000W is not recommended for both biomasses where oxidation reactions destroyed the structure of the materials. Moreover, microwave heating for long times had a bad influence on dyes removal. %Removal–adsorption capacity plot indicated that 0.8 and 1.0g/100mL is the optimum adsorbent dosage for E110 and E129, respectively. Analysis by Langmuir equation revealed that saturation values were 9.3 and 7.2mg/g for E110 and E129 at pH 2.0 and 25°C, receptively. Dyes removal by microwave-heated wood was a fast process and more than 90% of adsorbent's capacity was utilised within 30min.

Microwave Power Absorption Characteristics of Ferrites

The microwave power absorption characteristics of five ferrites, BaFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sub> , SrFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">19</sub> , CuFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , CuZnFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> and NiZnFe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , have been studied by determining the average power absorption patterns of the ferrite slabs using the derived power equations with consideration of both microwave dielectric and magnetic losses. It is shown that microwave power dissipates rapidly in the ferrites with a thickness of microwave penetration depth <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Dp</i> . The magnetic loss <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">QH</i> , <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">av</i> is much larger than the dielectric loss <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">QE</i> ,av for these ferrites in the slab thickness range of 0-3 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Dp</i> . The ratio of <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">QH</i> ,av to <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">QE</i> ,av remains above 1.5 as the slab thickness varies from <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Dp</i> /4 to 3 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Dp</i> although the difference between losses decreases with increasing thickness. The power absorption patterns of these ferrites also demonstrate that microwave resonance caused by magnetic loss occurs within the materials having a thickness less than a half-wavelength in the medium λ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> /2 . It is anticipated that microwave magnetic field heating of ferrites with a thickness smaller than λ <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m</i> /2 can be accelerated by magnetic loss resonance which leads to a significant increase in the power absorption in these ferrites.

Influence of internal convection during microwave thawing of cylinders

AbstractNumerical simulations were carried out for microwave thawing of 2‐D cylinders of pure materials with internal convection in the liquid regions. Enthalpy formulation of the energy balance equation was used with a superficial mushy region around the melting point. Electric field, energy and momentum balance equations were solved using the Galerkin finite‐element method with the penalty finite‐element formulation of the momentum balance equation. Microwave power absorption, temperature, and stream functions were studied for various cases. For samples of diameter D, thawing was contrasted between samples for 0.032 &lt; D/Dp &lt; 3.73 and 0.10 &lt; D/λm &lt; 1.58. These ratios were computed based on the liquid‐phase penetration depth Dp and wavelength of microwave radiation in the medium λm. In all cases, Pr = 0.5 was used and the Rayleigh number varied from 1.067 × 103 for the smallest diameter to 1.33416 × 105 for the largest sample (D = 2 cm). Thawing was contrasted for MWs being incident from the top and bottom faces of the cylinder and with the thawing dynamics in the absence of convection in the liquid. Our simulations indicate that convection plays a small role for D/Dp ≪ 1 and thawing is independent of the direction of MWs. At intermediate values of D/Dp where a strong maximum occurs in the power, the influence of convection with primary and secondary cell formation in the liquid regions was a strong function of the direction of incident microwaves. In the presence of multiple connected thawed regions convection was suppressed.

Sample–tip coupling efficiencies of the photon-scanning tunneling microscope

The photon-scanning tunneling microscope is the photon analog to the electron-scanning tunneling microscope. It uses the evanescent field due to the total internal reflection of a light beam in a prism, modulated by a sample attached to the prism. The exponential decay of the evanescent field is characterized by the penetration depth dp and depends on the angle of incidence θ, the wavelength, and the polarization of the incident beam. The 1/e decay lengths range from 150 to 265 nm as deduced from the expression of the electric-field intensity in the rarer medium for θ = π/2. If we place another optically transparent medium near the surface, frustrated total reflection occurs. It is shown theoretically and experimentally that, if we choose an appropriate angle of incidence θ(θ ≠ π/2) and change the index of refraction of one of the media, the decay length of the electric field can be extremely small, so that images with an improved resolution can be produced.

Terminology and Notation of Microwave Power and Electromagnetic Energy

Proposals for standardization of terms and notations are presented. Electra heat terminology in the multilingualInternational Elec trote chni calVocabulary (IEV) published by the International Electrotechnical Commission (IEC) is used as a basis. However, some deviations and extensions are discussed and proposed, for adaptation to the usage in modern literature in the subject area. A list of selected terms and notation is given. Some main proposals are to use ε0ε = ε0(ε’ jε”), ε’ being the relative permittivity and ε” the loss factor; and to define the penetration depth dp, by the perpendicular plane wave case lie power density.

Quantitative Surface Analysis by Fourier Transform Attenuated Total Reflection Infrared Spectroscopy

The Fourier transform infrared spectroscopic ATR (FT-IR-ATR) method has been applied to quantitative determination of chemical composition of thin surface layers. The powerful capability of the FT-IR-ATR spectral subtraction method was proved to determine poly(dimethylsiloxane) content in the surface layer of Cardiothane 51, which consists of poly(urethane) and poly(dimethylsiloxane) as a minor component, showing the detection limit of 0.2% of the content. An absorbance ratio of a selected band of poly(dimethylsiloxane) relative to a selected band of poly(urethane) was determined by FT-IR-ATR measurements on the pure samples of each of the constituting components that have the same area contacted onto the internal reflection element of Ge. Consideration was also given to the thickness of the surface layer that can be analyzed by the present method, and one half of the penetration depth dp was considered to better represent the thickness of the surface layer measured than dp.