Numerical investigation of the effects of partial metallization at the pore surface on the effective properties of a porous piezoceramic composite

This paper presents a numerical homogenization analysis of a porous piezoelectric composite with a partially metalized pore surface. The metal layers can be added to the pore surfaces to improve the mechanical and electromechanical properties of ordinary porous piezocomposites. Physically, constructing that composite with completely metalized pore surfaces is a challenging process, and imperfect metallization is more expected. Here, we investigate the effects of possible incomplete metallization of pore surfaces on the composite’s equivalent properties. We applied the effective moduli theory, which was developed for the piezoelectric medium based on the Hill–Mandel principle, and the finite element method to compute the effective moduli of the considered composites. Using specific algorithms and programs in the ANSYS APDL programming language, we constructed the representative unit cell element models and performed various computational experiments. Due to the presence of metal inclusion, we found that the dielectric and piezoelectric properties of the considered composites differ dramatically from the corresponding properties of the ordinary porous piezocomposites. The results of this work showed that piezocomposites with partially metallized pore surfaces can have a higher anisotropy, compared to the pure piezoceramic matrix, due to the defects in metal coatings.

Non-Layered Gold-Silicon and All-Silicon Frequency-Selective Metasurfaces for Potential Mid-Infrared Sensing Applications

We report simulations on the spectral behavior of non-layered gold-silicon and all-silicon frequency-selective metasurfaces in an asymmetric element configuration in the mid-infrared spectral window of 5–5.8 μm. The non-layered layout is experimentally feasible due to recent technological advances such as nano-imprint and nano-stencil lithography, and the spectral window was chosen due to the multitude of applications in sensing and imaging. The architecture exhibits significant resonance in the window of interest as well as extended tunability by means of variation of cell element sizes and relative coordinates. The results indicate that the proposed metasurface architecture is a viable candidate for mid-infrared absorbers, sensors and imaging systems.

The Electrochemical Stability of Starch Carbon as an Important Property in the Construction of a Lithium-Ion Cell

This paper shows use of starch-based carbon (CSC) and graphene as the anode electrode for lithium-ion cell. To describe electrochemical stability of the half-cell system and kinetic parameters of charging process in different temperatures, electrochemical impedance spectroscopy (EIS) measurement was adopted. It has been shown that smaller resistances are observed for CSC. Additionally, Bode plots show high electrochemical stability at higher temperatures. The activation energy for the SEI (solid–electrolyte interface) layer, charge transfer, and electrolyte were in the ranges of 24.06–25.33, 68.18–118.55, and 13.84–15.22 kJ mol−1, respectively. Moreover, the activation energy of most processes is smaller for CSC, which means that this electrode could serve as an eco-friendly biodegradable lithium-ion cell element.

Single / Dual-Band Frequency and Polarization Switching Using Frequency Selective Surfaces for Terahertz Applications

This paper presents reconfigurable frequency and polarization FSS-based with photoconductive switches in a single and dual-band operation for antenna applications at the terahertz band. The single band FSS unit-cell element exhibits frequency reconfigurability between 0.62 THz and 0.7 THz. It also converts the LP waves into CP over a frequency band ranging from 0.59 THz to 0.8 THz (30 % 3-dB BW). The dual-band FSS unit-cell element exhibits frequency reconfigurability between (0.42 THz and 1.03 THz) when the switches are turned ON and (0.51 THz and 0.865 THz) when the switches are turned OFF. Moreover, it exhibits polarization conversion over two bands from 0.46 THz to 0.56 THz (20% 3-dB B.W) and from 0.82 THz to 0.91 THz (12 % 3-dB B.W). The dual-band FSS unit-cell element is arranged in a 7 x 7 array and used as a reflector for two dipole antennas (A and B) operating at 0.82 THz and 0.5 THz, respectively. The same dual-band FSS-based surface enhances their gain to about 8.4 dBi and converts their polarization from LP to CP at 0.82 THz and 0.5 THz, respectively.

A wideband, single layer reflectarray antenna with cross loop and square ring slot loaded patch elements

This paper presents the design and analysis of a wideband X/Ku and Ku band reflectarray antenna. The proposed unit cell of the reflectarray antenna comprises a patch loaded with two distinct slots, viz. a square ring and a cross loop, printed on a low loss substrate, which is backed by a foam-loaded ground plane. The unit cell element offers a linear and large dynamic reflection phase range, which is achieved by optimizing the shape, location, and geometrical parameters of the two slots loaded on the patch. A 324 element microstrip reflectarray antenna of size 200 × 200 mm2 is constructed and analyzed for its radiation characteristics by simulation and measurement. The reflectarray offers a 3 dB gain bandwidth of 50.75% with the operating frequency range of 10–16.8 GHz. It offers a peak gain and aperture efficiency of 25.4 dB and 40% at 12.6 GHz, respectively. The cross-polarization level is below −40 dB over the entire operating frequency range.

Dual resonance element for broadband reflectarray antenna

<span>A dual resonance reflectarray unit cell element has been proposed which evolved from a square patch element to enhance its bandwidth performance. A bend in the width of the element is used to modify its dimensions and surface currents for broadband operation. The results have been analyzed in the frequency band of 24 GHz to 28 GHz. Two different combinations of its dimensions are selected for the investigating of its various performance parameters. A maximum static phase range of 432° and 255° have been obtained with selected dimensions. The wide-band features of proposed unit cell element can be used particularly to design a broadband reflectarray antenna for future fast communication systems.</span>

Mutual Coupling Reduction between Asymmetric Reflectarray Resonant Elements

A physically asymmetric reflectarray element has been proposed for wide band operations. The dual resonant response has been introduced by tilting one side of the square path element. The numerical results have been analyzed in the frequency band between 24GHz to 28GHz where a reflection phase range of more than 600° has been achieved. The proposed asymmetric element can produce mutual coupling with adjacent elements on a reflectarray. This effect has been monitored by placing the elements in a mirror configuration on the surface of reflectarray. The single unit cell element results have been compared with conventional 4 element unit cell and proposed mirroring element configuration. The proposed mirroring element technique can be used to design a broadband reflectarray for high gain applications.

Integrating MTJ Devices into a 130nm CMOS Process Flow

A Magnetic Random Access Memory (MRAM) device was successfully embedded into TowerJazz’s 130nm CMOS platform. The fabricated devices are stand-alone 4Mbit and 1Mbit MRAM memories and Multi-MLU magnetic sensors. This paper will describe the process development challenges in adapting a standard 130nm Cu BEOL to incorporate the magnetic cell element, and the device sensitivities to processing.The main process challenges to be discussed are 1) formation of shallow damascene Cu contacts to the lower electrode; 2) patterning of the 150nm magnetic cell both lithography and etching of the magnetic stack; 3) planarization of the topography from the magnetic cell; 4) formation of dual damascene VIA’s to both the magnetic cell upper electrode and to the CMOS. Some electrical yield results of the stand-alone MRAM memory and magnetic sensors will be presented. This project was a collaborative effort between TowerJazz and Crocus Technology