Metal Disk Research Articles

Comparative evaluation of the masking ability of lithium disilicate ceramic with different core thickness on the shade match of indirect restorations over metallic substrate: An In vitro study

Purpose:The purpose of this in vitro study was to comparatively evaluate the masking ability of lithium disilicate ceramic with different core thickness on the shade match of indirect restorations over metallic substrate.Materials and Methods:A total of 30 heat pressed lithium disilicate ceramic discs of low translucency were fabricated with diameter 10mm and thickness of 1 mm, 1.3 mm and 1.6mm with each thickness consisting of 10 samples to be used in the study. Thirty Ni-Cr metal discs of diameter 10mm were used to simulate metallic substrates .The colour difference of the lithium disilicate ceramic disc before and after cementation were measured using CIE LAB system.Results:The mean colour difference (ΔE) of Group I,Group II, Group III before cementation with the Ni-Cr metal discs was 17.32,13.01 and 11.73 respectively. The mean colour difference (ΔE) of Group I,Group II, Group III after cementation with the Ni-Cr metal discs was 16.32,12.10, 11.05 respectively.Conclusion:The mean colour difference of the three groups were found to be more than the clinically acceptable perceptibility threshold (ΔE < 3.3) indicative of reduced masking ability of all the three groups of ceramic discs over metallic substrate used in this study.

Numerical modeling of induction heating systems with load of azimuthal periodicity

The paper presents developed numerical modelling methodology of induction heating problems of disks with a simple and complex profile in 3D for calculating the coupled electromagnetic and thermal tasks in the parametric design language (ANSYS APDL). We demonstrate that the developed tools can be used for products of various sizes, as well as for other metal engineering components using the example of local electromagnetic processing of a metal disk and a diaphragm spring. The authors used development for parametric research and design of induction heaters. The described methodology has particular specificity, due to which it is possible to expand the scope for a number of engineering units with azimuthal periodicity property.

Aluminium sheet metal scrap recycling through friction consolidation

Abstract In the last decades, several direct-recycling techniques have been developed and investigated in order to avoid material remelting, typical of the conventional aluminum alloys recycling processes. Moreover, the remelting step for aluminum recycling is affected by permanent material losses. Solid-state recycling processes have proven to be a suitable strategy to face such issues. Friction Consolidation is an innovative solid state-recycling technology developed for metal chips. During the process, a rotating die is plunged into a hollow chamber containing the material to be processed. The work of friction forces decaying into heat soften the material and, together with the stirring action of the die, enable solid bonding phenomena producing a consolidated metal disc. This technology has been successively applied to metal chips; in this paper, the feasibility of the process to recycle sheet metal scrap is investigated. The quality of the obtained billets is evaluated through morphological observation and hardness measurements.

Cross section measurements of 155,157Gd(n,$\gamma$γ) induced by thermal and epithermal neutrons

Neutron capture measurements on $^{155}$Gd and $^{157}$Gd were performed using the time-of-flight technique at the n\_TOF facility at CERN. Four samples in form of self-sustaining metallic discs isotopically enriched in $^{155}$Gd and $^{157}$Gd were used. The measurements were carried out at the experimental area (EAR1) at 185 m from the neutron source, with an array of 4 C$_6$D$_6$ liquid scintillation detectors. The capture cross sections of $^{155}$Gd and $^{157}$Gd at neutron kinetic energy of 0.0253 eV have been estimated to be 62.2(2.2) kb and 239.8(9.3) kb, respectively, thus up to 6\% different relative to the ones reported in the nuclear data libraries. A resonance shape analysis has been performed in the resolved resonance region up to 180 eV and 300 eV, respectively, in average resonance parameters have been found in good agreement with evaluations. Above these energies the observed resonance-like structures in the cross section have been tentatively characterised in terms of resonance energy and area up to 1 keV.

Model for confined Tamm plasmon devices

It is shown that cavities formed between a multilayer quarter-wave Bragg reflector and a metal mirror which support Tamm plasmons can be modelled by using a hard-mirror approximation including appropriate penetration depths into the mirrors. Results from this model are in excellent agreement with those found by numerical methods. In addition Tamm modes that are laterally confined by the presence of a metallic disc deposited on the Bragg reflector can be described by the effective index model that is commonly used for vertical-cavity surface-emitting lasers (VCSELs). This enables the lateral modes confined by a circular disc to be found from conventional weakly-guiding waveguide theory similar to that used for optical fibres. The resonant wavelengths of these linearly-polarised (LP) guided modes are calculated as functions of disc diameter and other parameters.

Vibration signatures of a rotor-coupling-bearing system under angular misalignment

Forces and moments arise in flexible couplings while accommodating misalignments. These efforts are exerted on the coupled shafts, influencing the rotor dynamics and giving rise to vibration patterns, which are of interest for investigations focusing on malfunction signatures and, consequently, on fault identification and diagnosis. This work proposes the comparison between two approaches for modeling the forces and moments generated by a metallic disc coupling under angular misalignment. The first is a well-established model based on the linear bending flexure of the disc packs, and assuming the misalignment efforts are the sum of the first four harmonic components. In the second approach, a structural analysis of the coupling is conducted through finite element method, where the cyclic nature of coupling efforts is captured by the application of consecutive shaft spin angles. Steady state responses are simulated and then both orbit shapes and displacements spectrum are analyzed in order to highlight harmonic components rising due to misalignment. Finally, test rig measurements are compared to predicted results by the theoretical approach presented in this work.

Dynamic Bipolar Electrode Array for Visualized Screening of Electrode Materials in Light-Emitting Electrochemical Cells.

Charge injection at a metal/semiconductor interface is of paramount importance for many chemical and physical processes. The dual injection of electrons and holes, for example, is necessary for electroluminescence in organic light-emitting devices. In an electrochemical cell, charge transfer across the electrode interface is responsible for redox reactions and Faradic current flow. In this work, we use polymer light-emitting electrochemical cells (PLECs) to visually assess the ability of metals to inject electronic charges into a luminescent polymer. Silver, aluminum, and gold microdisks are deposited between the two driving electrodes of the PLEC in the form of a horizontal array. When the PLEC is polarized, the individual disks functioned as bipolar electrodes (BPEs) to induce redox p- and n-doping reactions at their extremities, which are visualized as strongly photoluminescence-quenched growth in the luminescent polymer. The three metals initially generate highly distinct doping patterns that are consistent with differences in their work function. Over time, the doped regions continue to grow in size. Quantitative analysis of the n/p area ratio reveals an amazing convergence to a single value for all 39 BPEs, regardless of their metal type and large variation in the size of individual doped areas. We introduce the concept of a dynamic BPE, which transforms from an initial metal disk of a fixed size to one that is a composite of p- and n-doped polymer joined by the initial metallic BPE. The internal structure of the dynamic BPE, as measured by the n/p area ratio, reflects the properties of only the mixed conductor of the PLEC active layer itself when the area ratio converges.

Note: A disk-shaft shaped high-speed rotary ultrasonic motor.

We report a novel high-speed rotary ultrasonic motor, which works at the out-of-plane vibration mode (B11 mode). This motor contains one tapered rotor and one metal disk-shaft shaped stator. The stator's vibration mode B11 is excited by two pairs of piezoelectric ceramics attached to the bottom face of the disk. Through the traveling wave propagation at the contact faces, the shaft located at the center of the metal disk can effectively drive the rotor pressed onto it to rapidly rotate. One prototype motor with the appearance size of Φ 29 mm × 8 mm and a mass of 13 g is fabricated, and the experimental results show that it can rotate at a relatively high speed of up to 7000 rpm at the driving voltage of 350 Vp-p. The steady speed of the motor is 5000 rpm, and the maximum output torque is about 0.5 mN m. With merits of high speed revolution, a simple structure and a compact size, this motor is highly promising for many applications, such as precise instruments and miniaturized industrial robots.

A Directive Antenna Based on Conducting Disks for Detecting Unintentional EM Emissions at Large Distances

This paper proposes a novel high-gain planar antenna design that consists of conducting metallic disks suspended on air and operates at 1 GHz. The antenna is designed for receiving the unintentional electromagnetic emanations generated by one or multiple embedded, “smart” electronic systems. The antenna consists of two layers of slotted conducting metal disks suspended on air and placed above the ground plane using teflon screws. The circular disks are designed to operate in higher order ${TM}_{12}$ mode. The screws’ location is the electric field nulls along the disk radius. The upper layer is $2 \times 2$ array of slotted circular disks electromagnetically coupled by the lower identical disk which is fed directly by a single coaxial feed. The complete fabrication of the antenna is done using aluminum metal sheets and involves no use of the dielectric substrate. The antenna has a peak gain of 19 dBi with impedance bandwidth ( $S_{11}\le -6$ dB) of 6.7%. The simple and cost-effective design can be easily scaled to higher frequencies.

Formation of a carbonaceous film on the surface of Cu in a bovine serum albumin solution

The tribochemical reaction between metal ions and proteins can result in the formation of a carbonaceous tribo-layer on the surface of metal-on-metal (MOM) artificial joints. This carbonaceous film can lubricate the tribo-pair and reduce the corrosion of the metal. The purpose of this work is to investigate the catalysis efficiency of Cu and Co ions in the formation of carbonaceous films at the contact regions. A ball-on-disc (Al2O3-on-Cu and Al2O3-on-Co alloy) friction mode in bovine serum albumin (BSA) solution was chosen for the wear test experiments. After the wear test, the tribo-layer formed on the wear spot (on Al2O3 ball) and wear track (metal disc) were collected and characterized. The results show that the Cu ions released upon friction promoted the adsorption of BSA on the wear track of Cu to give a protein film which was further transformed into a carbonaceous tribo-layer under the shear force between the Al2O3-Cu tribo-pair. When the Al2O3 ball and Co alloy were chosen as the tribo-pair, however, a carbonaceous tribo-layer was not observed on the Co alloy after the wear testing. This means that the catalysis efficiency of the Cu ion for the formation of a carbonaceous tribo-layer is stronger than that of the Co ion.

Dewetted nanostructures of gold, silver, copper, and palladium with enhanced faceting

At the foundation of nanoscience and nanotechnology is the ability to shape-engineer nanometric objects so as to exert control over their physical and chemical properties. Architectural control is achieved by manipulating thermodynamic and kinetic factors that are able to guide reactions along pathways that lead to the formation or elimination of particular crystal facets. While the dewetting of ultrathin metal films provides a straightforward method for generating substrate-based metallic nanostructures, the ability to shape-engineer these structures is limited to such an extent that even the formation of highly faceted equiaxed structures often proves challenging. This, however, is not the case for colloidal syntheses where the exquisite chemical controls and synthetic ease offered by liquid-phase chemistry has led to the generation of a diverse library of nanostructure architectures. Here, it is demonstrated that the faceting of dewetted structures of gold, silver, copper, and palladium can be enhanced by subjecting them to a liquid-phase chemical environment in which metal ions are reduced to a neutral state and deposited on the nanostructure surface in manner that leads to facet formation. The faceting procedure, which can be carried out in minutes, is also shown to be amenable to a templated dewetting approach in which lithographically-defined metal discs formed in an array each agglomerate to form a single nanostructure. The work has the potential to increase the functionality of dewetted nanostructures by enabling facet-dependent chemical reactivity and plasmonic hot spots.

Laser technique in diaphragm cum rupture disc for defence oriented silver oxide zinc reserve batteries

ABSTRACTThis paper deals with a novel method of forming a score mark to develop silver based metal diaphragm cum rupture disc using laser micro machining technique. Defense oriented primary reserve type silver oxide zinc batteries utilize metallic diaphragm cum rupture disc with controlled indentation in the battery activation system. The criticality of the score mark to meet the activation parameters calls for a precise and controlled technique for “scoring” like micro machining using laser. The study of laser machining involves various metals, which act as a safety pressure relief system. The uniqueness of the work relates to devising a process for the making of diaphragm, which bursts at a pre-set pressure to allow flow of electrolyte, to activate a battery and not as a mere safety pressure relief system. Detailed analysis of silver diaphragm is performed through dynamic and destructive tests. Investigations through white light interferometer (WLI) and scanning electron microscope (SEM) have confirmed the repeatability of process. A novel method of making diaphragm catering to the requirements is established in this work and full description of the process including various process parameters is presented.

Computational and Experimental Investigation of Mechanical and Thermal Contacts of Ceramic Blades with the Metal Disk in Gas Turbine Engines

Models of thermal and mechanical contacts of ceramic and metal parts in lock joints of turbines of aircraft gas turbine engines have been developed which take account of the character of operating loads in them. Experimental data on the strength and thermal conductance of a ceramics–metal contact joint have been presented. The investigations were carried out with ceramic specimens based on hot-pressed silicon nitride and silicon carbide reinforced with diamond particles.

Elastoplastic Flexure of Round Steel Beams. 2. Residual Stress

Residual stress in metals may lead to shaping defects and the failure of metal structures in prolonged operation. It may arise on account of plastic metal flow on shaping (as in forging) or slow irreversible creep at elevated temperature, under the prolonged action of loads. In viscoelastic media, it may be due to ductile strain accumulating when a body is in a deformed state for a long time. Residual stress also affects the microstructure of metals and may be present within and around crystalline grains as residual microstress, sometimes known as latent elastic stress. Residual stress is also described as eigenstress, by analogy with the eigenfunctions introduced by mathematicians to denote functions corresponding to specific parameters (eigenvalues) in a differential equation with specified boundary conditions. The concept of internal stress has been proposed as a general term for stress created by the body itself. Residual stress is then confined to cases in which the internal stress is due to irreversible deformation. Besides the creation of a favorable residual stress system, local increase in strength will be noted in forged metal disks with pronounced strain hardening, as long as the Bauschinger effect does not cancel out such benefits. In the present work, extremal values of the residual stress in a straight cylindrical steel rod (beam) are studied, in the case of flexure.

Design and measure of a high-loss transmission band metamaterial filter based on vertical coupling effect between localized surface plasmon modes

A broad band high-loss metamaterial filter with stacked metal–dielectric disks is designed and manufactured. The hybrid plasmonic structure includes two stacked metal disks, a dielectric disk, and a dielectric substrate. A 48 THz high-loss band is obtained in experiments. The vertical coupling effect between localized surface plasmon (LSP) resonant modes excited on the edges of two stacked metal disks leads to the 18 THz high-loss band. It is found that the effective impedance is mismatched to the free space based on the effective medium parameters calculation results. The experimental study also reveals that the high-loss bandwidth is nearly linear increased and the central frequency is nearly linear reduced with the diameter of particles increasing. An equivalent LC circuit model is proposed to explain the changes in bandwidth and central frequency.

Nickel deposition and penetration into the stratum corneum after short metallic nickel contact: An experimental study.

Knowledge about the skin deposition and penetration of nickel into the stratum corneum (SC) after short contact with metallic items is limited. To quantify nickel skin deposition and penetration into the SC after short contact with metallic nickel. Sixteen nickel-allergic participants and 10 controls were exposed to 3 pure nickel discs and 1 aluminium disc on each volar forearm for 3 × 10 minutes. Before exposure, 1 forearm was irritated with 0.5% sodium lauryl sulfate under 24-hour occlusion. Immediately, as well as 24 and 72 hours after metallic disc exposure, outer SC layers were removed with adhesive tapes and the nickel content was measured. Nickel deposition and SC penetration capable of eliciting allergic nickel dermatitis were found immediately and after 24 hours. Significantly higher nickel amounts were found on normal skin and in the SC of nickel-allergic participants than in controls both immediately and after 24 hours, and on irritated skin immediately after exposure. Nickel deposition and SC penetration is considerable after nickel skin exposure of 3 × 10 minutes. Combined with the allergic responses resulting from the same exposures reported previously, this study highlights that short skin exposure to nickel-releasing items may cause allergic nickel dermatitis.

Comparison of two-dimensional arrays of gold disks and holes for plasmonic enhancement of Ge/Si quantum dot mid-infrared photodetectors

We analyze and compare two complementary 2D plasmonic structures, a gold film perforated with a subwavelength hole array and a periodic lattice of gold disks, for infrared detector applications and argue that the former gives the best results when integrated on top of a Ge/Si quantum dot mid-infrared photodetector (QDIP). The periodicity of both metasurfaces is the same and equal to 1.2 µm. The QDIP coupled with the metal disk array exhibits about 3.7 times plasmonic responsivity enhacement as compared to a conventional Ge/Si device and displays an over 11 times enhacement when integrated with the holey Au film. At 78 K, the quantum efficency of about 2% and photovoltaic peak detectivity of 4.5 × 1012 cm·Hz1/2/W are determined at a wavelength of 4.2 µm in a hybrid QDIP with the perforated gold film.

Mechanistic Study of the Synergy between Iron and Transition Metals for the Catalysis of the Oxygen Evolution Reaction.

A comprehensive study of the synergy between Fe and six transition metals (M=Ti, Co, Ni, Cu, Ag, Au), and how their M-Fe oxides electrocatalyze the oxygen evolution reaction (OER) was undertaken. Measurements were made using metal disks as the working electrodes and the addition of Fe3+ ions to the 1 m KOH electrolyte. The surfaces of the metal disks were oxidized after the OER. Interestingly, Fe interacted synergistically with all metal oxide layers except for that of Ti, resulting in enhanced catalytic activity for the OER. At an overpotential (η) of 400 mV, the current densities of the Ni and Ag disks in the Fe3+ ions-spiked electrolyte increased by 253 and 132 times, respectively, whereas it was only 20-30 times for the Co and Cu disks (compared with the OER in pure KOH at η=400 mV). The Tafel slopes of the Fe, Co, Ni, Cu, and Ag disks in 1 m KOH+Fe3+ electrolyte were in the range of 29-42 mV dec-1 . The surface morphology and post-OER concentration of Fe in the catalysts could not be used to account for differences in the OER activities. Cyclic voltammetry showed that improvements in the OER performance were accompanied by changes in the redox features of the metal disk electrodes, which indicated the presence of electronic interactions between them and the Fe3+ . Strikingly, this was not observed between Ti and the Fe3+ ions, which could explain the lack of synergy between Ti and Fe3+ towards the OER catalysis. Electrochemical impedance spectroscopy indicated that the charge-transfer resistances of all the electrodes (except Ti) decreased after the addition of Fe3+ ions. Fe plays an important role in all these observed phenomena and we propose that the surface-adsorbed Fe species serve as the main active sites for OER in these synergistic M-Fe combinations.

An approach for fabrication of Al-Cu composite by high pressure torsion

The method utilizing high-pressure torsion (HPT) processing followed by annealing to fabricate Cu-Al in situ composite with enhanced mechanical properties is presented. The initial sample consists of three metal discs Cu/Al/Cu was processed by HPT (5 GPa, 5 turns). The analyses of the microstructure after HPT carried out by transmission electron microscopy and scanning electron microscopy equipped with energy dispersive spectrometry (EDS). After HPT, the development of nanostructure with the mean crystallite size of about 100 nm in the produced sample was revealed with the small presence of the intermetallic phases. Investigation of the kinetics during subsequent annealing at 450 °C/30 min showed the in situ formation of intermetallic Al2Cu, AlCu, Al3Cu4, Al2Cu3 and Al4Cu9 phases in the copper matrix which was detected by EDS. The formation of intermetallic phases after annealing was also confirmed by X-ray diffraction. The results showed that microhardness of the composite considerably increases from an initial value of ∼380 for HPT sample to a saturation value of ∼900 after annealing.

Does clinical testing support the current guidance definition of prolonged contact for nickel allergy?

BackgroundThe European Chemical Agency (ECHA) definition of prolonged contact was introduced in 2014 and has not been evaluated clinically.ObjectivesTo assess whether nickel‐sensitized individuals react on patch testing with high nickel‐releasing metal discs for short and repetitive periods.Materials and methodsWe patch tested 45 nickel‐sensitized individuals double‐blind with 2 different types of high nickel‐releasing discs for 10, 30 and 60 minutes on 3 occasions over a period of 2 weeks, and for 1 longer period. Discs were tested for nickel release.ResultsNickel release from both discs significantly exceeded the 0.5 μg Ni/cm2/week limit of the EU REACH nickel restriction. However, only 1 individual tested had a largely dose‐dependent allergic reaction.ConclusionsThe majority of nickel‐allergic subjects did not react to nickel discs after 2 hours or after repetitive exposures of up to 30 minutes on 3 occasions over a period of 2 weeks. The length of time needed to cause nickel allergic contact dermatitis in most nickel‐allergic individuals is longer than the ECHA guidance definition. Longer test times are needed to define the time required to cause dermatitis in most nickel‐allergic individuals. As a limitation, the test conditions did not adequately assess real‐life factors such as friction, which is relevant for some uses of nickel.