Epoxy Substrate Research Articles

Sustainable lignin-based high-efficiency flame-retardant epoxy resins with excellent mechanical properties

As an abundant natural aromatic polymer, how to realize the high-value utilization of lignin (LA) is still a difficult problem. Herein, a sustainable flame retardant (LA@APP) was synthesized through hydrogen bonding interactions between LA and ammonium polyphosphate (APP), then flame retarded alone epoxy resin (EP/LA@APP). With loading of 6 wt% LA@APP, the LOI of EP/LA@APP6 rose to 27.9 % and achieved UL-94 V0 rating. Meanwhile, EP/LA@APP6 presented a 63.5 % reduction in peak of heat release rate (pHRR) and an 51.3 % decrease in peak of smoke production rate (pSPR). LA@APP could promote the EP composites to form the denser and more continuous expanded charring residuals than APP during the combustion process, effectively shielding the underlying epoxy substrate and thus enhancing fire safety. Additionally, the shell layer of LA@APP, abundant in hydroxyl groups and methoxy groups, effectively improved the compatibility and interfacial interaction with EP. Therefore, the tensile, flexural and impact strength of EP/LA@APP6 reached 50.8 MPa, 86.1 MPa and 7.81 kJ/m2, higher than those of pure EP at 48.3 MPa, 81.5 MPa and 7.45 kJ/m2. This flame retardant with simultaneously enhanced fire safety and mechanical properties of epoxy resin was expected to realize the high-level utilization of lignin.

Analyses and control of interphase structures and adhesion properties of epoxy resin/epoxy resin for development of CFRP adhesion systems

In the adhesion of carbon fiber reinforced plastics (CFRP), the boundary regions were composed of only epoxy resins of CFRP matrix and adhesives, and their similar epoxy structures pose significant difficulty in studying the adhesion mechanism. Herein, we focused on structure and properties of laminates of epoxy resin substrates and adhesives with different curing conditions of substrates. We prepared laminates using deuterated epoxy adhesives or fluorinated epoxy adhesives, and their boundary regions were identified through confocal Raman scattering measurements. The regions were distributed into “penetration” and “interphase”. In particular, the penetration phase is a key of the adhesion properties. The penetration behaviors strongly depended on the crosslinking densities of the adherends, suggesting that the penetration regions would be directly impacted by the curing conditions of the substrates and molecular size of epoxy adhesive precursors. Our findings provide insights into novel designs of the reliable adhesion-based manufacturing systems of CFRP.

A low-profile Wideband Meta-Surface based Microstrip Antenna for 5G Wireless Communications

This article presents a low-profile meta surface microstrip radiator operating at 34GHz with high performance for the operation of 5G wireless communications. The meta-surface radiator entails an improved patch that is present between the 4×4 proportioned square ring meta-surface and a ground plane. Initially, the rectangular slot of the patch would be aligned to improve the inherent narrow bandwidth. But the multifunctional properties of the proposed meta surface antenna with a convinced operating frequency increases the functionality and size of the network. Moreover, this paper outlines how the unit cell meta surface is implemented as a superstrate with a single U-slot for a rectangular patch antenna. The proposed antenna is simulated and measured on FR4 epoxy substrate material with a modified patch with a specific air-gap yields an overall antenna size of 1.36λ0×1.36λ0×0.1818λ0 especially to operate at 34 GHz resonating frequency. The results demonstrate that the meta surface radiator can achieve a wide-bandwidth range from 28 to 41GHz for S11 with a return loss of 60dB along with a maximum valued gain of 10dBi with a 3dB AR bandwidth.

Exploring Cu(triNHC) as a Bifunctional Catalyst for Carbonate Synthesis From CO2 and Epoxy Amines/Sulfides/Ethers

ABSTRACTThis study highlights the synergistic interplay between a Lewis acidic copper ion and a dissociated ligand from Cu(triNHC) complexes in the synthesis of cyclic carbonates from CO2 and epoxy compounds. The reactions were found to proceed efficiently under Cu(triNHC)‐catalyzed conditions, yielding significant quantities of cyclic carbonates across various epoxy substrates encompassing amine, sulfide, and ether functionalities. Stereochemical analyses underscore a pronounced propensity for retaining the stereochemistry of epoxy compounds in the resultant carbonates. This suggests a mechanism involving double inversion of stereochemistry during the reaction, which comprises catalyst‐mediated epoxide ring opening, subsequent CO2 addition, and carbonate ring closing. These findings align with established mechanisms for CO2 fixation reactions, shedding light on the intricate pathways underlying this catalytic process.

Design of Microstrip Patch Antenna for WSN Application

Abstract: This paper focuses on the design and simulation of a microstrip patch antenna for Wireless Sensor Network (WSN) applications, utilizing HFSS (High-Frequency Structure Simulator) software and an FR-4 epoxy substrate. The objective is to develop an efficient and cost-effective antenna tailored for the 2.4 GHz frequency band, commonly used in WSNs due to its favourable propagation characteristics. The choice of FR-4 epoxy substrate, with a relative dielectric constant (ࡾࢿ (of 4.4 provides a balance of performance, availability, and cost-effectiveness. These properties are crucial in determining the antenna's resonant frequency and overall efficiency. The design process involves optimizing the dimensions of the rectangular microstrip patch antenna to achieve the desired frequency and performance metrics. HFSS simulation tools are employed to model the antenna's behaviour, allowing for precise adjustments and performance predictions. Key parameters analysed include return loss (S11), gain, radiation pattern, and bandwidth.

Transparent, robust, and anti-fingerprint silicone coating with a three-dimensional cross-linked network enabled by hydrosilylation reaction

Silicone coatings with anti-smudge, anti-fingerprint, abrasion resistance, and ultraviolet (UV) resistance properties are increasingly demanded for touch screens as the development of artificial intelligence and human-computer interaction interfaces. Herein, a transparent, robust, and self-cleaning silicone coating was developed by incorporating cage-like structures and long carbon chains into a 3D cross-linked network via the rational combination of polymethylhydrosiloxane (PMHS), PSS-Octavinyl substituted (VPOSS), lauryl acrylate (LA), and 1,2-epoxy-4-vinylcyclohexane (EVCH) through hydrosilylation reaction with the presence of Karstedt catalysts. After introducing sealed diphenyliodonium phosphate (I-200), the silicone coating (PVLE-I-200) demonstrated excellent pencil hardness, anti-smudge, and abrasion resistance, and its average transmittance of visible light reached about 92 %. Owing to the low surface energy carbon chains, the coating showed amphiphobic properties and excellent anti-fingerprint property. The binding between cyclohexyl epoxy and glass substrate contributed to the high adhesion of the coating, which remained nearly intact and slightly reduced surface wettability after 500 friction cycles of sandpaper. In addition, the PVLE-I-200 coating demonstrated UV resistance which could withstand 200 h of UV irradiation attributed to the cage-like structure of VPOSS. The functional silicone coating provides insights into the development of environmentally friendly coatings for touch screens with high transparency, abrasion resistance, anti-smudge, and anti-fingerprint properties.

Wideband circularly polarized reconfigurable metasurface antenna for 5G applications

Abstract A framework of a metasurface (MTS) – based wideband circularly polarized (CP) reconfigurable antenna for fifth generation (5G) wireless systems operating in the sub-6 GHz mid-frequency range is presented in this article. The proposed structure contains a simple patch antenna, which serves as the primary source, a shorting pin, two ring slots, and a metasurface superstrate. The shorting pin and two ring slots produce perturbation resulting in circular polarization with a narrow axial ratio (AR) bandwidth. A metasurface (MTS) superstrate composed of 4 × 4 rectangular patches stacked over the primary source antenna generates additional resonances that significantly improve the −10 dB impedance and 3 dB axial ratio (AR) bandwidth. Two PIN diodes are employed to alter the circular polarization between left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP). The prototype is made using an FR-4 epoxy substrate and has an overall size of 50 mm × 35 mm × 4.2 mm. The antenna has a −10 dB bandwidth of 44 % (4.0–6.2) and a 3 dB axial ratio bandwidth of 28 % (4.2–5.6). It also has a 3 dB beam width of 74° and 85° in the E and H planes, a gain of 7.1 dBi, cross-polar isolation of more than 15 dB, and a unidirectional radiation pattern. The simulated and measured results confirm that the implemented antenna is promising for sub-6 GHz 5G communication systems, particularly cognitive radio, wireless body area networks (WBAN), and satellite communication systems.

Next Generation Heterogeneous 3D IC Chip Packaging

The demand for a faster and more efficient IC has been steadily increasing more than ever to accommodate the trend of Artificial Intelligence, Industry 4.0, Machine Learning, and Big Data. Traditionally, the semiconductor industry has kept up with demand of faster and more efficient IC by shrinking the size of transistor. As we approach a 1 nm transistor the technological challenge will be challenging to overcome as quantum tunneling becomes more pronounced and would decrease the reliability of the chip. To overcome this technological challenge, an advance packaging of 3D IC chip technology has been developed and delivered to market such as CoWoS (Chip-on-Wafer-on-Substrate) and InFO (Integrated Fan-Out). However, the aforementioned technology have their drawbacks with CoWoS uses interposer and TSV (through-silicon substrate via) which make it costly, time consuming, and wastes a lot of energy and InFO is limited in the number of layers it can accommodate for chiplets. Both of those technology are currently limited to 2 or 3 layer of IC and difficult to be modularize. In this study, we aim to develop a heterogeneous 3D IC package that can overcome the aforementioned problem which is modular, cost-effective, able to integrate chip from different manufacturers, and capable to stack more than 3 layers of ICs. This study has successfully completed the first stage of development by employing an advanced package consisting of Epoxy substrate with 200Å Ti/500Å Pt/1000Å Au metal interconnects, previously fabricated as a base for 3D stacking. Keywords : 3D IC Package, Advance Packaging, Modulable IC Packaging, Heterogeneous Integration Figure 1

Hybrid Self‐Repairing Polymer Composites Based on a Mixture of Intrinsic and Extrinsic Self‐Healing

AbstractThe development of high‐strength and multiple self‐healing polymer materials remains a major challenge. In this study, a hybrid self‐healable polymer using the combination of intrinsic and extrinsic self‐healing is demonstrated. The epoxy resin microcapsules with dynamic disulfide bonded shells are successfully prepared through an interfacial polymerization method, which are then added into the intrinsically self‐healable epoxy resin substrate also containing disulfide bonds. The unique combination structure enables the polymer composites to exhibit high mechanical strength and excellent multiple self‐healing efficiency. On the one hand, the Young's modulus and tensile strength of the material are enhanced due to the reinforcement effect of the fillers. On the other hand, the extrinsic self‐healing strategy of the microcapsules, which released repair agents, can support the intrinsic repairing substrate to improve the self‐healing ability of the material. More interestingly, the design of the disulfide bond structure of the microcapsule shell contributes to the high self‐healing capability of the material during multiple self‐healing processes.

Application of Friction Riveting technique for the assembly of electronic components on printed circuit boards (PCB)

This study focuses on the effects of reducing the diameter of rivets used in Friction Riveting due to the need for downscaling when joining assemblies on a smaller scale. The Friction Riveting process has shown promising feasibility for a variety of material combinations and applications in the transportation industry. Recent research has explored the potential application of this technique in electronics, specifically for the assembly of printed circuit boards (PCBs), using AA-2024-T351 rivets on thin glass-fiber-reinforced epoxy substrates (FR4). The joint formation of joints produced with PCBs was investigated in terms of process temperature evolution, microstructural changes, and mechanical properties. Joints were obtained at process temperatures ranging from 285 ºC to 368 ºC. The use of 4 mm rivets resulted in extensive delamination, weak joint mechanisms, and cracking, impaired by the different coefficients of thermal expansion of the materials involved. Reducing the rivet diameter to 3 mm significantly improved joint quality. A further reduction to 2.5 mm minimized delamination but led to insufficient anchorage and cracking. Joints produced with a 3 mm rivet diameter achieved the highest ultimate tensile force of 276 N. This study sets the foundation for applying the Friction Riveting process to practical PCB assemblies, demonstrating that optimizing the process parameters to the diameter-to-thickness ratio can balance sufficient rivet anchoring, minimize delamination, and reduce cracking.

Isolation enhancement of the F-shaped four-port MIMO antenna for WiMAX, Wi-Fi, WLAN and ISM band applications using dielectric material

In this article, an F-shaped four-port multiple-input multiple-output (MIMO) antenna is designed and analyzed. In the designed antenna for achieving high isolation, we introduced a novel isolation technique that appears like plus-shaped wall placed in between the antenna elements. The antenna is designed on a low-cost FR-4 epoxy substrate with total dimensions of 0.61 λ 0 × 0.61 λ 0 × 0.03 λ 0 (31 mm × 31 mm × 1.58 mm) where λ 0 is the free space wavelength at 5.8 GHz and experimentally verified. This MIMO antenna design covers operating the range of frequencies 5.47–6.20 GHz ( | S 11 | < − 10 dB) which provides a bandwidth of 730 MHz. In terms of performance, the proposed antenna achieves high isolation of < − 45.52 dB with an improved reflection coefficient of − 30.44 dB, a peak gain of 3.77 dBi and a radiation efficiency more than 82% across the entire operating band. Moreover, the achieved MIMO diversity parameters of the proposed antenna are envelope correlation coefficient < 0.005, diversity gain < 9.99 dB, mean effective gain < − 3 dB and total active reflection coefficient < − 10 dB in the operating band of frequency. The simulated and measured results show a good agreement between them. Finally, after analyzing the performance of the proposed MIMO configuration, we can say that this antenna is suitable for C-band, WiMAX, Wireless-Fidelity (Wi-Fi), Wireless Local-Area Network (WLAN), Bluetooth and Industrial, Scientific, & Medical (ISM) bands applications.

High gain dual-band circularly polarized two-port MIMO antenna with equivalent circuit for WiMAX/5G/C- and X-bands applications

Abstract A compact two-port novel geometry with microstrip fed wide slot equivalent circuit based dual-band MIMO antenna system of low specific absorption rate is presented. The proposed structure has two horizontal slotted patch with symmetrical chamfered at both corners, which are responsible for improving impedance bandwidth (IBW) and achieving wide axial ratio. The different cutting slots from the ground plane and vertical slot in MIMO antenna elements are responsible for enhancing isolation. The proposed antenna design covers −10 dB IBW ranging from 3.25 to 4.39 GHz and 6.74–8.41 GHz. This antenna radiates at 3.5 and 7.2 GHz with corresponding radiation efficiencies of 86.2 % and 92.32 %, isolation &lt; ${&lt; } $ −20.05 and &lt; ${&lt; } $ −29.71 dB, excellent peak gain 8.02 and 9.32 dB, while bandwidth of 1.14 GHz (29.84 %) and 1.67 GHz (22.05 %). Different diversity parameters for the proposed MIMO antenna have been obtained such as, envelope correlation coefficient &lt; ${&lt; } $ 0.0121 and &lt; ${&lt; } $ 0.0009, diversity gain nearly 9.87 and 9.99 dB, channel capacity loss &lt; ${&lt; } $ 0.0028 bits/s/Hz, and mean effective gain &lt; ${&lt; } $ −3 dB. The proposed work is printed on FR-4 epoxy substrate with overall electrical size of 0.29 λ 0 × 0.61 λ 0 × 0.018 λ 0 at 3.5 GHz. Moreover, the suggested work also exhibits circular polarization ranging from 3.24–4.38, 5.27–7.2, 7.6–8.1 and 8.2–8.41 GHz. Finally, experimental analysis was done and the tested results exhibit good agreement with simulated results. The proposed structure is a suitable candidate for WiMAX/C-band, satellite for X-band and 5G LTE band applications.

Acoustic Characterization of Integrated Circuits During Operation

Abstract Power electronics are widely serving as core components of propulsion systems in electric vertical takeoff and landing (VTOL) aircraft. Nevertheless, affected by the Paschen effect, the breakdown voltage of these electronics during flight is significantly lower than that on the ground, which could deteriorate system stability, or even cause aircraft faults or crashes, increasing safety risks for the public. As such, condition monitoring of power electronics has become critical for the safe operation of eVTOL. To achieve non-intrusive monitoring, acoustic emissions (AE) sensors have gained traction with their prominent resistance to electromagnetic interference and high temperatures. However, existing studies yield conflicting results regarding whether an increase in loading voltage impacts the internal mechanical stress of electronics. To address this issue, we present this work to probe the existence and the pattern of a relationship between load voltage and stress wave, since the change of mechanical stress could generate acoustic waves that can be acquired by AE sensors. In this study, an AE sensor was applied onto an oscillator placed upon an epoxy substrate to characterize the acoustic waves emitted from the device under various input loads. In the experiment, we observed a unique AE signal pattern characterized by two distinct components that consistently intersect at a specific frequency. The time required to establish such intersections progressively lengthens as the load voltage increases. Through time-domain and frequency-domain analyses of the unique AE signals under different load voltages, it was discovered that certain features of the unique AE signals have an approximately linear relationship with the load voltage.

A Novel Rhombus Shaped Multiband Antenna for Wireless Applications

A 30X20X1.6mm3 Novel Rhombus Shaped ring type multiband Antenna was proposed in this paper. The Antenna has 25x15mm2 partial ground inserted below the FR4 Epoxy Substrate to improve performance of Antenna. In addition, we added two rectangle shaped patch structures of dimensions 14X5.5mm2 on both sides of Feed structure to improve S11.The proposed design operates at three bands covering C, X, and Ku band regions. Here we got better S11 at 12.1GHZ which is useful for Radar Applications.

A Compact Dual-polarized Probe-fed UWB Antenna System for Breast Cancer Detection Applications

This article proposes an electrically small, probe-fed Ultra-Wideband (UWB) monopole antenna on a slotted truncated ground plane for breast cancer detection. The physical footprint of the proposed antenna element is 33 mm × 35 mm × 0.5 mm. This element is designed on the low-cost FR4 Epoxy substrate with a thickness of 0.5 mm. The proposed antenna has an electrical size of 0.33λ × 0.35λ × 0.005λ at the lowest frequency of operation; the radiator offers an impedance bandwidth of 8.34 GHz, which implies a fractional bandwidth of 115.5%. A compact dual-polarized antenna topology with two orthogonally placed probe-fed monopole antennas is proposed to achieve polarization diversity. The impedance characteristics of the individual radiating elements are maintained in spite of the electrical proximity of the radiators. The numerically computed and experimentally measured results of dual-polarized electrically small UWB antenna agree quite well. The proposed dual-polarized antenna topology is investigated for its utility in breast cancer detection in simulation.

Effect of inorganic material surface chemistry on structures and fracture behaviours of epoxy resin

The mechanisms underlying the influence of the surface chemistry of inorganic materials on polymer structures and fracture behaviours near adhesive interfaces are not fully understood. This study demonstrates the first clear and direct evidence that molecular surface segregation and cross-linking of epoxy resin are driven by intermolecular forces at the inorganic surfaces alone, which can be linked directly to adhesive failure mechanisms. We prepare adhesive interfaces between epoxy resin and silicon substrates with varying surface chemistries (OH and H terminations) with a smoothness below 1 nm, which have different adhesive strengths by ~13 %. The epoxy resins within sub-nanometre distance from the surfaces with different chemistries exhibit distinct amine-to-epoxy ratios, cross-linked network structures, and adhesion energies. The OH- and H-terminated interfaces exhibit cohesive failure and interfacial delamination, respectively. The substrate surface chemistry impacts the cross-linked structures of the epoxy resins within several nanometres of the interfaces and the adsorption structures of molecules at the interfaces, which result in different fracture behaviours and adhesive strengths.

Design and mathematical modeling of DNG metamaterial having six-band capabilities with high effective medium ratio

ABSTRACT In this paper, six-band double negative (DNG) metamaterial with a substantially high effective medium ratio (EMR) under the S and C microwave band is designed and investigated for multiple microwave applications. The proposed metamaterial unit cell consists of four Plus Appended Split Ring Resonator (PASRR) cells, which are combined with variable sides and positions by plus (+) shape stubs at the centre. All four Plus Appended Split Ring Resonator (PASRR) cells are mutually coupled with each other to vary the electrical length to achieve hexa Bands DNG characteristics in a lossy FR-4 epoxy substrate with the thickness of 1.5748 mm. A parameter extraction method has been used to extract effective permittivity (ε eff), permeability (μ eff) and refractive index (n). Moreover, the equivalent circuit model is obtained. Ansys HFSSTM software & Keysight ADSTM software are used to obtain the simulated and theoretical results, respectively, which agree measured with simulated and theoretical results.

Preparation of Epoxy Resin/Carbon Black Superhydrophobic Photothermal Materials with Shape Memory Capacity for Anti/De‐Icing

The accumulation of ice can cause damage to various equipment, resulting in numerous economic losses. One promising solution for anti/de‐icing is the use of superhydrophobic materials powered by solar energy. In this study, a multilayer superhydrophobic photothermal materials with anti/de‐icing ability is prepared. First, an epoxy resin (EP) substrate with microstructure is prepared by the template method. Then carbon black (CB) nanoparticles are sprayed on the substrate as the photothermal layer. Finally, fluorine‐modified resin is dip‐coated as the hydrophobic modified layer. The light absorption of this material is 1.6 in the wavelength range of 400–2000 nm. The surface temperature rose to 114.2 °C within 270 s under 1 sun illumination. Additionally, the materials can respond to light stimulation and exhibit shape memory, with a shape recovery rate close to 100%. The air cushions in the micro‐nanostructures delayed the droplet freezing time by nearly two times. The good photothermal properties endowed the materials with photothermal de‐icing performance, which improved the de‐icing efficiency by almost 2.2 times. Furthermore, the materials demonstrate outstanding durability that can resist to mechanical wear, acid‐base corrosion, and UV aging, thermal stability, and self‐cleaning properties, making it highly suitable for outdoor equipment applications.

Fabrication of a polishable and reusable triple electrode as a new generation of three-electrode systems for the electrochemical analysis applications through both immersion and drop casting-procedures

An innovative three-electrode system was developed for electrochemical analysis, aiming to overcome the limitations of conventional approaches. The system incorporates a glassy carbon rod as the working electrode, platinum wire as the counter electrode, and silver wire as the quasi-reference electrode that are positioned within an epoxy resin substrate. The advantages of this type of three-electrode system include the possibility of sample analysis in both drop mode and when immersed in the solution, low manufacturing cost, reduction of chemical consumption, no need for special maintenance protocols, no requirement for stand, absence of liquid junction potential (due to the direct contact of the reference electrode with the solution), usability for on-site analysis, and usability for non-aqueous solutions.To check the efficiency of this electrode, cyclic voltammetry technique was used. Also, for direct comparison of PTE with conventional three-electrode system and screen-printed electrode (SPE), current density was used instead of peak current. According to the results, PTE system shows more peak current for the same surface area of the working electrode compared to other systems, which shows the high efficiency of the proposed system for electrochemical analysis. Acetaminophen (ACT) was chosen in order to investigate the ability to measure an analyte with PTE using differential pulse voltammetry (DPV). The linear range was obtained from 29.12 μM to 609.37 μM with a detection limit (LOD) 20.22 μM. Also, PTE was used to measure ACT in tablet as real sample.

Novel robot arm concept for lightweighting high-performance machinery

Abstract To improve the efficiency of robots, a novel sustainable design of a robotic arm is proposed that can address the thermal, vibration, energy usage and dynamic stiffness issues. The proposed design utilises easy-to-produce carbon fibre tubes including some that are commercially available, for the robot link instead of traditional materials, which can be heavy and carbon intensive. The design involves arranging several carbon fibre reinforced polymer (CFRP) tubes in a specific array inside an epoxy resin substrate. Based on this design, a Finite Element Analysis (FEA) was implemented demonstrating the relatively low mass and high stiffness characteristics. Design optimisation was then performed using custom generated MATLAB® code to reduce the computation time. The proposed design for a one-meter-long robot link with a diameter of 108 mm offers a stiffness of 0.75 N/μm. A structural steel link, with the same stiffness, is 33 % heavier than the concept design. The design maintains thermal stability with about a third of the thermal deformation seen in structural steel.