Silver Epoxy Research Articles

Longitudinal (α33) and transverse(α31) dynamic magnetoelectric hysteretic response for CoFe1.88Dy0.12O4–K0.5Na0.5NbO3 lead-free multiferroic laminates

The magnetoelectric (ME) laminate structures of CoFe1.88Dy0.12O4 (CFDO, Ferrite) and K0.50Na0.50NbO3 (KNN, ferroelectric/piezoelectric) phases were fabricated by silver epoxy bonding technique and tested the ME response in longitudinal and transverse mode. The CFDO reveals the cubic spinel structure while KNN reveals the perovskite orthorhombic crystal structures having dense microstructure. The CFDO confirms the phase segregation of the DyFeO3ortho-ferrite phase, while the KNN lead-free ceramic showed the Curie temperature of 416 °C, 13µC/cm2 maximum polarization, 25,296 × 10-15 m2/N figure of merit, piezoelectric charge coefficient d33 of 47 pC/N. The longitudinal (α33) and transverse (α31) dynamic magnetoelectric response is studied to figure out the effective magnetic field direction to get better values of magnetoelectric voltage sensitivity i.e. αME. Both modes revealed the hysteretic behavior i.e. lagging of ME voltage response to an applied magnetic field which evidences a true multiferroic character of CFDO/KNN laminates. Remarkably, the (CFDO /KNN/ CFDO) structure demonstrated a substantial magnetoelectric coefficient in LT (α31) mode of approximately 38.5 mV/cm·Oe at a magnetic field of 400 Oe and −37.55 mV/cm·Oe at a magnetic field of −400 Oe. Thus, here we present the magnetoelectric laminate structure of CFDO /KNN/ CFDO phases beneficial for magnetic field sensors.

A system for bioelectronic delivery of treatment directed toward wound healing

The development of wearable bioelectronic systems is a promising approach for optimal delivery of therapeutic treatments. These systems can provide continuous delivery of ions, charged biomolecules, and an electric field for various medical applications. However, rapid prototyping of wearable bioelectronic systems for controlled delivery of specific treatments with a scalable fabrication process is challenging. We present a wearable bioelectronic system comprised of a polydimethylsiloxane (PDMS) device cast in customizable 3D printed molds and a printed circuit board (PCB), which employs commercially available engineering components and tools throughout design and fabrication. The system, featuring solution-filled reservoirs, embedded electrodes, and hydrogel-filled capillary tubing, is assembled modularly. The PDMS and PCB both contain matching through-holes designed to hold metallic contact posts coated with silver epoxy, allowing for mechanical and electrical integration. This assembly scheme allows us to interchange subsystem components, such as various PCB designs and reservoir solutions. We present three PCB designs: a wired version and two battery-powered versions with and without onboard memory. The wired design uses an external voltage controller for device actuation. The battery-powered PCB design uses a microcontroller unit to enable pre-programmed applied voltages and deep sleep mode to prolong battery run time. Finally, the battery-powered PCB with onboard memory is developed to record delivered currents, which enables us to verify treatment dose delivered. To demonstrate the functionality of the platform, the devices are used to deliver H^+ in vivo using mouse models and fluoxetine ex vivo using a simulated wound environment. Immunohistochemistry staining shows an improvement of 35.86% in the M1/M2 ratio of H^+—treated wounds compared with control wounds, indicating the potential of the platform to improve wound healing.

Effects of silver epoxy reinforcement on graphene nanoplatelets functionalized surface in pool boiling heat transfer enhancement

Silver Epoxy reinforcement is pivotal to enhance the adhesive strength of Graphene nanoplatelets (GNP) on the substrate. This experimental study seeks to scrutinize the effects of Silver Epoxy reinforced GNP functionalized surface on the heat transfer of pool boiling. Three different GNP-based coatings are analyzed: simple GNP, uncured GNP reinforced with Silver Epoxy, and cured GNP reinforced with Silver Epoxy, all applied to copper substrate. For each coating, the surface morphology, chemical bonding, and wettability are examined. Under a heat flux of 550 kW/m2, the experimentally derived heat transfer coefficient improves by 194%, 36%, and 77% respectively on pristine GNP, uncured GNP/Epoxy, and cured GNP/Epoxy compared to the bare copper surface. The epoxy reinforcement weakens the exceptional boiling improvement achieved by a GNP functionalized surface. Although the thermal curing process turns the GNP/epoxy coating from hydrophobic to hydrophilic and recovers partly the level of boiling enhancement, the biphilicity of GNP tends to dominate boiling heat transfer enhancement by enhancing the bubble dynamics. The hydrophilicity has a subordinate effect by re-wetting the dry spots and preventing the vapour blanket. Silver Epoxy reinforcement significantly enhances the adhesive strength of GNP on a substrate but at the expense of boiling heat transfer enhancement.

Improvement in the Thermal Conductivity of Silver Epoxy Adhesive by Treating with Water Vapor.

With the miniaturization of electronic devices, electronic packaging has become increasingly precise and complex, which presents a significant challenge in terms of heat dissipation. Electrically conductive adhesives (ECAs), particularly silver epoxy adhesives, have emerged as a new type of electronic packaging material, thanks to their high conductivity and stable contact resistance. However, while there has been extensive research on silver epoxy adhesives, little attention has been paid to improving their thermal conductivity, which is a critical requirement in the ECA industry. In this paper, we propose a straightforward method for treating silver epoxy adhesive with water vapor, resulting in a remarkable improvement in thermal conductivity to 9.1 W/(m·K), three times higher than the sample cured using traditional methods (2.7 W/(m·K)). Through research and analysis, the study demonstrates that the introduction of H2O into the gaps and holes of the silver epoxy adhesive increases the path of electron conduction, thereby improving thermal conductivity. Furthermore, this method has the potential to significantly improve the performance of packaging materials and meet the needs of high-performance ECAs.

Investigation of time variations of redox reactions in SrRuO3 through interface-sensitive resistance measurements

We used an interface-sensitive resistance measurement technique to observe the time evolution of the early stages of redox reactions at the interface between the metallic oxide SrRuO3 and a silver epoxy electrode at around room temperature (∼280–320 K). On exposure to a reducing gas (CO or H2), the interface resistance gradually increased. The time variation functions of the resistance increases for CO and H2 were similar, although the magnitude was greater for H2 than for CO. After substitution of O2 for the reducing gas, the interface resistance decreased to almost the initial value, i.e., that before exposure to a reducing gas. The resistance variations can be well explained by the time variations of the oxygen deficiency at the SrRuO3 interface and subsurfaces as a result of reduction or oxidation. We regarded the reactions as pseudo-first-order reactions and evaluated the rate constants of the SrRuO3 redox reactions at a SrRuO3–Ag interface. For the reduction (resistance increase) process, a single exponential component was enough to fit the data, which suggests that the reduction proceeds successively from outside to inside the bulk. Adsorption of oxygen atoms in the oxidation (resistance decrease) process involved several rate constants, at least up to three exponential components, depending on the prior degradation by a reducing gas. The effective activation energy of each redox reaction was evaluated from an Arrhenius plot.

A conventional fixation volume electron microscopy protocol for plants.

Volume electron microscopy techniques play an important role in plant research from understanding organelles and unicellular forms to developmental studies, environmental effects and microbial interactions with large plant structures, to name a few. Due to large air voids central vacuole, cell wall and waxy cuticle, many plant tissues pose challenges when trying to achieve high quality morphology, metal staining and adequate conductivity for high-resolution volume EM studies. Here, we applied a robust conventional chemical fixation strategy to address the special challenges of plant samples and suitable for, but not limited to, serial block-face and focused ion beam scanning electron microscopy. The chemistry of this protocol was modified from an approach developed for improved and uniform staining of large brain volumes. Briefly, primary fixation was in paraformaldehyde and glutaraldehyde with malachite green followed by secondary fixation with osmium tetroxide, potassium ferrocyanide, thiocarbohydrazide, osmium tetroxide and finally uranyl acetate and lead aspartate staining. Samples were then dehydrated in acetone with a propylene oxide transition and embedded in a hard formulation Quetol 651 resin. The samples were trimmed and mounted with silver epoxy, metal coated and imaged via serial block-face scanning electron microscopy and focal charge compensation for charge suppression. High-contrast plant tobacco and duckweed leaf cellular structures were readily visible including mitochondria, Golgi, endoplasmic reticulum and nuclear envelope membranes, as well as prominent chloroplast thylakoid membranes and individual lamella in grana stacks. This sample preparation protocol serves as a reliable starting point for routine plant volume electron microscopy.

Electronic properties of BZT nano-ceramic grades at low frequency region

BZT ceramics was prepared by using fine powder mixture of BaCO3, TiO2 and ZrO2 in the respective molar ratio to form Ba(Zr0.10Ti0.90)O3 via solid state reaction at elevated temperature. The prepared BZT was milled in the planetary ball mill from 0-120 min to achieve different powder grades from micron to nano-sized particles. After the powder characterization by XRD and SEM the samples were pressed in disc shape and sintered at different temperatures from 1100-1350?C in the air. The sintered samples were characterized by SEM and their density and average grain size was determined and presented vs. sintering temperature and powder grades (milling time). After that the silver epoxy electrodes were deposited on sintered disc samples. The disc samples capacity and resistivity were measured at low frequency region from 1 Hz to 200 kHz using low frequency impedance analyzer. The sintering temperatures and powder grades were used as parameters. Finally the specific resistance ?, dielectric constant (?' + j?") and tg? where determined from the impedance measurements. The behavior of electronic properties where analyzed e.g. the relaxation effect of the space charge (inter-granular electric charges) vs. sintering temperature and ceramic grades. The results obtained were compared with best literature data for the losses in BZT ceramics at low frequencies.

Self-biased characteristics of NZCF/BCZT layered magnetoelectric composites: A novel coupling paradigm in magnetoelectricity

Here, we investigate room temperature magnetoelectric (ME) behavior of ferroelectric Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) and ferrimagnetic Ni0.75Zn0.20Co0.05Fe2O4 (NZCF) layered composites. The ferroelectric ceramics (thickness, t, ∼0.6, 0.8, and 1.0 mm) are stacked at magnetic specimen of fixed t ∼ 1 mm, coupled with conducting silver epoxy. The phase formation, surface morphology, dielectric, magnetic, magnetoelectric and magnetodielectric characteristics of bilayer composites have been studied in the present work. The maximum value of magnetoelectric (ME) coupling coefficient (αME) is found to be 70, 90, and 110 mVcm−1Oe−1 for composite having ferroelectric layer thickness t ∼ 1, 0.8, and 0.6 mm, respectively. More importantly, αME(H→0) remains finite for composite (t ∼ 0.8, and 0.6 mm) in zero magnetic field, which is a clear evidence of self-biasing phenomenon in NZCF/BCZT layered composite. For closer insight about underlying mechanism, we estimate magnetodielectric (MD) coefficient for the layered composite. The MD coefficient is found to be significantly high ∼6.32% for the thickness 0.6 mm. MD% vs magnetic field, H, curves exhibit steeper field dependence in low field region and for H≥2kOe MD possess saturation characteristics. The high saturation characteristics suggest that the magnetoelectricity in layered composite is driven by magnetostriction mechanism and causes robust ME coupling. Further, we obtain electrical signal ∼143 mV with the Hdc ∼250 Oe, as a consequence of interplaying nature of magneto(striction)- piezo(electricity). Such a sizeable response will improve the underlying intimacy between technology and practical application. The study reveals that the pellet based layered composites may be a proven strategy for the realization of self-biased ME devices.

Investigation of Adhesive's Material in Hermetic MEMS Package for Interfacial Crack between the Silver Epoxy and the Metal Lid during the Precondition Test.

A hermetic Micro-Electro-Mechanical Systems (MEMS) package with a metal lid is investigated to prevent lid-off failure and improve its reliability during the precondition test. While the MEMS package benefits from miniaturization and low cost, a hermetic version is highly sensitive to internal pressure caused by moisture penetration and the reflow process, thus affecting its reliability. In this research, the finite element method is applied to analyze the contact stress between the metal lid and the silver epoxy by applying the cohesive zone model (CZM). Moreover, the red dye penetration test is applied, revealing a microcrack at the metal lid/silver epoxy interface. Further analyses indicate that the crack is caused by internal pressure. According to the experimental testing and simulation results, the silver epoxy material, the curing process, the metal lid geometry, and the bonding layer contact area can enhance the bonding strength between the metal lid and the substrate.

Stiffness degradation in fatigue life of composites using dielectric state variables

Composite materials are widely used in aerospace and automotive structures for decades and over the years the community has gained a better understanding of the damage and failure modes of composites under fatigue. In this article, a dielectric characterization methodology for in-situ monitoring of composites under fatigue environments is proposed. A novel method of measuring the dielectric state variables in Broadband Dielectric Spectroscopy (BbDS) using Extremely Conductive Silver Epoxy Adhesive (ECSEA) paste is presented. These dielectric state variables serve to identify the precursor of the beginning of the end of life of the composite material under fatigue loading. The reliability of using this method for in-situ monitoring to provide fatigue life estimates and to indicate the immediate need for maintenance, repair and/or replacement of the structural component is discussed.

Development, fabrication and evaluation of passive interface gloves

Previously, glove-integrated communication based on gestures, hand movement and finger touch had a complex operating system and an active power source was needed. This paper introduces batteryless and maintenance-free interface gloves. Our solution is based on passive ultra-high frequency (UHF) radio frequency identification (RFID) technology, comprising four electro-textile antenna parts and three RFID microchips (each with a unique ID). The three RFID microchips have unique IDs, which can be activated by the gentle touch of the human finger and used to control the surrounding technology. The aim is to evaluate the reliability of different conductive materials and microchip attachment methods. The antennas are fabricated from two different materials: a stretchable and a non-stretchable commercial electro-textile. Further, two types of microchip attachment methods are used with both antenna materials: a conductive silver epoxy and embroidery with conductive multifilament silver-plated thread. The developed interface gloves are tested by six users in a home and in an office environment, where they achieve 93–100% success rates. Especially those glove interfaces with the antennas fabricated from the non-stretchable electro-textile and the antenna-microchip interconnections embroidered with conductive thread showed good read ranges (80–110 cm). The gloves also show practical functionality, when tested with a mobile reader in practical identification and access control application. These results are very encouraging, especially when considering that the interface glove, being maintenance-free and cost-effective, promises versatile and interesting applications for customizing user-friendly augmentative and alternative communication solutions, easy controlling of ambient assisted-living applications, and providing simple identification and access control for increased safety and comfort.

Nanofiltration Using Graphene-Epoxy Filter Media Actuated by Surface Acoustic Waves

We exploit the enhancement of liquid transport through a graphene-epoxy film actuated by surface acoustic waves to demonstrate effective and efficient nanoparticle filtration. Unlike previously reported findings using graphene films, the addition of silver epoxy to create a composite film allows higher excitation powers to be sustained over extended operation durations without disintegration of the film such that an increase in the liquid flow rate through the film by up to fourfold can be achieved. Counter to intuition that suggests that the epoxy would fill the interstitial voids between the layers that make up the graphene film so as to reduce the efficiency of liquid transport through the film, we show instead that the higher density and elastic stiffness of the composite film enhances the transmission of acoustic energy into the film that, in turn, leads to more efficient liquid transport through it. Filtration efficiencies above $99$% are obtained for 26-nm particles, decreasing to 99% for 10-nm and 5-nm particulates, which is a significant improvement compared to that obtained with a pure graphene film. While a decrease in filtration rate over time is observed (up to 50% over 3 h of continuous operation) typical to that of graphene and other filter media, the introduction of a simple backwash process allowed for up to 87% recovery of the initial filtration rate. The significant performance enhancement, namely the fourfold increase in throughput, filtration efficiencies of up to 99% for nanoparticles down to 5 nm, and the ability to sustain extended operation at higher powers without disintegration through such a facile and cost-effective modification to the film highlights its potential applicability in practical nanofiltration systems.

A Compact Wideband Planar Magic Tee for Monopulse Antenna Array Applications

This letter presents a compact, wideband, planar, E-arm folded magic tee at $Ku$ -band for monopulse slotted waveguide antenna array applications. A novel impedance matching structure, an L-shaped septum, is implemented at the magic tee junction, which results in wide impedance bandwidth at all ports. The height of this septum is the same as that of the waveguide height, which allows the design to be very compact. An impedance bandwidth of 22% is achieved for a return loss of 20 dB. The magic tee is manufactured using a high-precision electric discharge machining (EDM) process and followed by the integration of subparts using silver epoxy bonding. Simulation and measured results are compared. Measured amplitude balance of < 0.1 dB, phase balance of <2°, and isolation of better than −35 dB have been achieved. The proposed design is a good technique for the design of broadband, miniaturized monopulse comparators for monopulse antenna array applications.

Oxygen Sensors Based on Titanium Oxide Layers Produced By Plasma Electrolytic Oxidation

Introduction Plasma electrolytic oxidation (PEO) of titanium is a powerful technique for creating key materials, for instance, in photocatalytic devices, automotive components, biomedical prostheses and recently in gas sensors [1,2]. Graphite-platinum electrodes on top of PEO oxide layers on titanium foils led to gas sensors for H2, H2O and CO, depending on the applied detection principle [2]. In our study, we investigate the potential of PEO produced titanium oxide layers for detecting O2.In this context, the porous microstructure, layer thickness and crystal titanium dioxide phase composition is essential. The porous microstructure provides a high surface-to-bulk ratio which is beneficial for gas interaction. The thickness and phase composition affect the electronic resistivity. Recent studies show, that the titanium oxide layer may vary in its porosity, thickness and phase composition, depending on the fabrication parameters in PEO [3, 4]. For instance, the crystal phase, either anatase or rutile, can be adjusted intentionally by customizing the electrolyte in the process. Based on recent findings [3, 4], we optimize the titanium oxide layer and apply it as sensor material for detecting oxygen. Method Oxide layers on titanium foils were produced by galvanostatically controlled plasma electrolytic oxidation in concentrated sulfuric acid with small additions of phosphoric acid up to 3% mole fraction. Before and after PEO, the samples were analyzed for weight gain with a microbalance. Oxide surfaces and cross sections were systematically studied in different phases of the process by scanning electron microscopy and x-ray diffraction. From confocal Raman microscopy on cross sections, we derived some information about the phase distribution in the oxide layer. Elemental composition was investigated by energy dispersive x-ray spectroscopy.The top electrode on the oxide layers consists of platinum and was applied by sputter deposition. Electrical connection between substrate as well as top electrode and socket pins was achieved with either silver epoxy glue or gold wire bonding. The gas sensing experiments were performed in a gas-flow apparatus with two pressurized gas bottles (oxygen and nitrogen). Mass flow controllers adjust the overall gas flow and the concentration of oxygen. Results and Conclusions Oxide coatings on titanium were produced in a PEO process with constant current density and were applied as gas sensing materials. The electrolyte in the PEO process was varied by different amounts of sulfuric and phosphoric acid. Therefore, the intensity of characteristic breakdowns in the PEO process and their impact on the oxide layer changes. In pure sulfuric acid, rough surfaces with high pore densities and mainly rutile evolve. With small additions of phosphoric acid, the destructive reforming is suppressed and mainly anatase is formed. Our findings explain the drastic change by a preferential adsorption of H3PO4 anions on the anodic area, which block the surface for more reactive H2SO4 anions [3]. Our findings from PEO were exploited to customize the oxide layers for application as sensor material for oxygen detection. The sensor performance varies, depending on the structure of the oxide layer. The signal was investigated regarding the sensitivity, stability and reproducibility. The performance was explained in a simple model of oxygen interaction.

Structural and multiferroic properties of trilayer green magnetoelectric Co0.8Ni0.2Fe2O4/K0.25Na0.75NbO3/Co0.8Ni0.2Fe2O4 composite structure

We have investigated the structural, dielectric, magnetic-magnetostrictive, ferroelectric-piezoelectric and magnetoelectric (ME) properties of green (Pb-free) Co0.8Ni0.2Fe2O4/K0.25Na0.75NbO3/Co0.8Ni0.2Fe2O4 (CNFO/KNN/CNFO) trilayer laminate (2-2) multiferroic composite structure. Magnetostrictive Co0.8Ni0.2Fe2O4phase was synthesized by the solution combustion technique and the piezoelectric K0.25Na0.75NbO3 phase was synthesized by a solid-state method. The trilayer ME laminate composite structure of CNFO-KNN phases fabricated by silver epoxy adhesive bonding technique. The magnetostrictive Co0.8Ni0.2Fe2O4 phase exhibits a piezomagnetic coefficient of −0.029 ppm/Oe at 1500 Oe magnetic field. The piezoelectric K0.25Na0.75NbO3 showed a piezoelectric charge coefficient of d33 ~57 pC/N. The trilayer CNFO/KNN/CNFO laminate structure reveals the ME coefficient (αME) of 3.06 mV/Oe·cm which is relatively higher than the 0–3 connectivity composite structures. Here, we have discussed the fabrication technique for multiferroic laminate structures for the green magnetoelectric device having αME ~3.06 mV/Oe·cm with their magnetic/magnetostrictive and ferroelectric/piezoelectric properties.

Resistive switching in tunnel junctions with a single-crystal La2NiO4 electrode

We study the resistive switching in tunnel junctions with single-crystal La2NiO4 electrodes. Such electro-resistive devices are promising candidates for future nonvolatile memory and reconfigurable logic applications thanks to their simple structure, excellent scalability and endurance. Our tunnel junctions were prepared by painting a spot of conductive silver epoxy on the surface of a La2NiO4 single crystal. The interface between the silver and the semiconducting crystal served as a natural barrier forming planar normal metal/insulator/semiconductor (N–I–S) tunnel junctions with resistances ranging from a few Ohms to more than hundred thousands of Ohms. The current–voltage (I–V) measurements performed on such junctions at room temperature demonstrated a bias-driven switching between high and low resistance states with ratios close to 100% and high endurance. A combination of 2- and 3- probe I–V measurements unambiguously demonstrated that the resistive switching is associated with the interfaces between the La2NiO4 crystal and the silver-contact electrodes, with negligible contribution from the bulk of the crystal. Similar resistive-switching phenomena in other oxide materials were previously associated with crystal-lattice distortions produced by an applied voltage/electric field. Here, we use an ultra-sensitive capacitive displacement meter to monitor the field-induced lattice distortions in situ. We observe that the crystal contraction/expansion is strongly correlated with the resistive switching. We also note that the Joule heating from dc bias may contribute to the crystal size changes. Our results provide a new insight into the origin of lattice distortions/resistive switching in transition metal oxides while the observed interfacial nature of the switching phenomenon is promising for fabrication of thin-film planar devices to be used in nonvolatile memory and logic.

Co-Integrated PIN-PMN-PT 2-D Array and Transceiver Electronics by Direct Assembly Using a 3-D Printed Interposer Grid Frame.

Tiled modular 2-D ultrasound arrays have the potential for realizing large apertures for novel diagnostic applications. This work presents an architecture for fabrication of tileable 2-D array modules implemented using 1-3 composites of high-bandwidth (BW) PIN-PMN-PT single-crystal piezoelectric material closely coupled with high-voltage CMOS application-specific integrated circuit (ASIC) electronics for buffering and multiplexing functions. The module, which is designed to be operated as a λ -pitch 1.75-D array, benefits from an improved electromechanical coupling coefficient and increased Curie temperature and is assembled directly on top of the ASIC silicon substrate using an interposer backing. The interposer consists of a novel 3-D printed acrylic frame that is filled with conducting and acoustically absorbing silver epoxy material. The ASIC comprises a high-voltage switching matrix with locally integrated buffering and is interfaced to a Verasonics Vantage 128, using a local field programmable gate array (FPGA) controller. Multiple prototype 5 ×6 element array modules have been fabricated by this process. The combined acoustic array and ASIC module was configured electronically by programming the switches to operate as a 1-D array with elements grouped in elevation for imaging and pulse-echo testing. The resulting array configuration had an average center frequency of 4.55 MHz, azimuthal element pitch of [Formula: see text], and exhibited average -20-dB pulsewidth of 592 ns and average -6-dB fractional BW of 77%.

Unprecedented Piezoresistance Coefficient in Strained Silicon Carbide.

Reports reveal that the piezoresistance coefficients of silicon carbide (SiC) nanowires (NWs) are 2 to 4 times smaller than those of their corresponding bulk counterparts. It is a challenge to eliminate contamination in adhering NWs onto substrates. In this study, a new setup was developed, in which NWs were manipulated and fixed by a goat hair and conductive silver epoxy in air, respectively, in the absence of any depositions. The goat hair was not consumed during manipulation of the NWs. The process took advantage of the stiffness and tapered tip of the goat hair, which is unlike the loss issue of beam sources in depositions. With the new fixing method, in situ transmission electron microscopy (TEM) electromechanical coupling measurements were performed on pristine SiC NWs. The piezoresistance coefficient and carrier mobility of SiC NW are -94.78 × 10-11 Pa-1 and 30.05 cm2 V-1 s-1, respectively, which are 82 and 527 times respectively greater than those of SiC NWs reported previously. We, for the first time, report that the piezoresistance coefficient of SiC NW is 17 times those of its bulk counterparts. These findings provide new insights to develop high performance SiC devices and to help avoid catastrophic failure when working in harsh environments.

Electrical Conductivity Enhancement of Epoxy by Hybrid Carbon Nanotubes and Self-made Silver Nanoparticles

Flexibility electrode with high stretchability, electrical conductivity, and good mechanical properties are desirable, owing to their promising applications in electronic circuit and human motion monitoring systems. In this paper, a high performance flexibility electrode was prepared based on printable and electrically conductive adhesive (ECA). This flexibility electrode is fabricated by mixing silver nanoparticles (AgNPs), carbon nanotube (CNT) and epoxy resin and screen-printed to a required shape. The spherical AgNPs were prepared by DC arc plasma method. The Ag NPs present a polycrystalline crystal structure, the particle’s diameter range from 20 to 150 nm, with an average of 80 nm. Simultaneously, this flexibility electrode provides the advantages of simple, scalable fabrication, robust mechanical properties and versatility in applications. Based on these performance characteristics, its applications in flexible printed electrodes are demonstrated, revealing its tremendous potential for applications in flexible and wearable electronics. The flexibility sensor prepared by ECA exhibits fascinating comprehensive performances. The ECA filled with 65 % Ag NPs and 0.8 % CNT shows an excellent electrical conductivity (9×10−4 Ω·cm) and bonding strength (9.2 MPa).

Ultrahigh Recovery of Fracture Strength on Mismatched Fractured Amorphous Surfaces of Silicon Carbide

Nanowires (NWs) have been envisioned as building blocks of nanotechnology and nanodevices. In this study, NWs were manipulated using a weasel hair and fixed by conductive silver epoxy, eliminating the contaminations and damages induced by conventional beam depositions. The fracture strength of the amorphous silicon carbide was found to be 8.8 GPa, which was measured by in situ transmission electron microscopy nanomechanical testing, approaching the theoretical fracture limit. Here, we report that self-healing of mismatched fractured amorphous surfaces of brittle NWs was discovered. The fracture strength was found to be 5.6 GPa on the mismatched fractured surfaces, recovering 63.6% of that of pristine NWs. This is an ultrahigh recovery, due to the limits of reconstruction of dangling bonds on the fractured amorphous surfaces and the mismatched areas. Simulation by molecular dynamics showed fracture strength recovery of 65.9% on the mismatched fractured amorphous surfaces, which is in good agreement with the experimental results. Healing on the mismatched fractured amorphous surfaces is by reorganization of Si-C bonds forming Si-C and Si-Si bonds. The potential energy increases 2.6 eV in the reorganized Si-C bonds and decreases by 3.2 and 1.9 eV, respectively, in the formed Si-C and Si-Si bonds. These findings provide insights for the reliability, design, and fabrication of high performance NW-based devices, to avoid catastrophic failure working in harsh and extreme environments.