Adhesive Material Research Articles

Waste From Alwar Quartzite (A Global Heritage Stone From Rajasthan - India) As Secondary Raw Materials for Cementitious Tile Adhesives

Waste deriving from quarrying operations of natural stone material retains almost all the mineralogical and compositional characteristics of the original material, for such reason this research aimed to test prototypes cementitious tile adhesives made up recycling the Alwar Quartzite waste, used as fine and ultra-fine aggregate. Particle size distribution analysis, along with X-ray diffractometry, X-ray fluorescence and Scanning Electron Microscopy were carried out to characterize the waste. Experimental research involved the mix-designing of three dough formulations (a regular one [N], a latex added [L] and a fast-setting [R]) tested by using different types of tiles: (i) polished metal plates, (ii) ceramic tiles and (iii) rough natural stone slabs. Fresh prepared doughs were firstly tested for thixotropy achieving high values (ranging 82–93%) and cured for normative requested time after being stuck on a concrete support as reported in European UNI standard regulations. After respective curing time, adhesives technical performances were evaluated by the Pull-Off test obtaining results for Class 1 (N and R) and Class 2 (L) adhesives with high initial tensile adhesive strength. Experimental results carried out in this research proved the possibility to use huge amounts of waste coming from Indian stone industry in cementitious tile adhesives sector without compromising technical performances, proposing itself as an alternative method to landfill disposal for this waste.

Evalution of shear bond strength of brackets bonded using different hydrophobic and hydrophilic adhesives: An invitro study

A review of the long history of orthodontic bonding adhesives shows that many evolutional developments have occurred from the first chemically-cured composite resins to the most recently introduced light-cured color-change adhesives. An ideal orthodontic adhesive should have adequate bond strength while maintaining unblemished enamel after debonding. Therefore, researchers have been working hard to achieve the best quality and gentlest materials for bonding orthodontic brackets.To evaluate the shear bond strength of brackets bonded using four different adhesives in both dry and in moist environment.A total of 80 orthodontically extracted premolars will be selected. They are divided into 4 equal groups of different adhesives which are further sub-divided into 2 group each (dry and in presence of moisture). All the selected teeth will be cleaned and store in saline until it use. All teeth will be mounted on acrylic block. The shear bond strength will be measured by Lloyd’s Universal testing machine. The obtained data will be statistically evaluated using SPSS22 for Windows using ANOVA test at statistical significance.: The shear bond strength of the four groups were tested with Instron universal testing machine; breaking load at which bond failure occurred was recorded and bond strength was calculated. Data obtained was compiled on MS Office Excel Sheet (2007, Microsoft Redmond Campus, Redmond. Washington, United States.)Data was subjected to statistical package for social sciences (SPSS v 21).Statistically significant difference seen between the hydrophobic and hydrophilic adhesives. In the present study we did Tukey’s post hoc test for pairwise comparison of different hydrophobic and hydrophilic adhesives. It show highly significant values. : The greatest bond strength values were achieved with TransbondXT in both dry and saliva contamination condition. These values were significantly greater than those achieved with Greengloo, RMGIC and Aqualine LC. The overall study conclude that TransbondXT was considered the feasible adhesive material for orthodontic bonding followed by Aqualine LC.

Double-Sided Pressure-Sensitive Adhesive Materials under Human-Centric Extreme Environments.

Maintaining the adhesion strength of flexible pressure-sensitive adhesives (PSAs) is crucial for advanced applications, such as health monitoring. Sustainable mounting is critical for wearable sensor devices, especially under challenging surroundings such as low and high temperatures (e.g., polar regions or deserts), underwater and sweat environments (physical activity), and cyclical shear complex stresses. In this article, we consider the adhesive, mechanical, and optical properties of medical-grade double-sided PSAs by simulating extreme human-centric environments. Diverse temperature conditions, water and humidity exposures, and cyclical loads were selected and tested over long intervals, up to 28 days. We observed that high temperatures increased the shear adhesion strength due to the pore closing and expanding contact area between the adhesive layer and substrate. Conversely, low temperatures caused the adhesive layers to harden and reduce the adhesive strength. Immersion in salty and weakly acidic water and excessive humidity reduced adhesion as water interfered with the interfacial interactions. PSA films showed either adhesive or cohesive failure under extreme mechanical stresses and cyclical loading, which is also affected by the presence of various polar solvents. We demonstrated that the variable adhesive performance, mechanical properties, and optical transparency of pressure-sensitive materials can be directly related to changes in their morphologies, surface roughness, swelling state, and alternation of the mechanical contact area, helping to establish the broader rules of design for wearable human health monitoring sensors for the long-term application of wearable devices, sensors, and electrodes.

Comparison of the safety and efficacy of three superficial skin closure methods for multi-layer wound closure in total knee arthroplasty: a multicenter, prospective, randomized controlled trial

BackgroundGood wound healing is critical to infection prophylaxis and satisfactory rehabilitation in Total Knee Arthroplasty (TKA). Currently, two techniques, i.e., barbed continuous subcuticular suture without skin adhesive or combined use skin adhesive (n-butyl-2) are being used for superficial wound closure of TKA. While a new skin adhesive (2-octyl) with self-adhesive mesh has been employed as an alternative to conventional surgical skin closure in TKA, its superiority, especially in reducing wound complications and improving wound cosmetic outcomes has not been investigated. This study aimed to compare 2-octyl, n-butyl-2, and no skin adhesive in terms of safety and efficacy in TKA superficial wound closure.MethodsWe conducted a multicenter, prospective, randomized controlled study in 105 patients undergoing primary TKA between May 2022 and October 2023. Each patient’s knee was randomized to receive 2-octyl, n-butyl-2, or no skin adhesive skin closure with all using barbed continuous sutures in deep tissue. Wounds were followed 1, 3, 5 days, 2, 6 weeks, and 3 months after surgery. Wound discharge, complications, cosmetic outcomes, patient satisfaction, and wound-related costs were compared among these three methods.ResultsWound discharge was less in 2-octyl group and n-butyl-2 group than in non-adhesive group at 1 day, with the discharge only being less in 2-octyl group than in the non-adhesive group at day 3 and day 5 days (P < 0.05). There was no statistical difference in the incidence of other wound complications among the groups (P > 0.05). The 2-octyl group achieved better cosmetic effects than the other two groups in 6 weeks and 3 months (P < 0.05). Compared to the non-adhesive group, 2-octyl group scored higher in overall patient satisfaction score in 2 weeks and incurred lower costs (P < 0.05).ConclusionsSkin closure in TKA using 2-octyl adhesive material showed superiority when compared to no skin adhesive or n-butyl-2, in reducing wound discharge, improving the cosmetic outcomes, without increasing wound complications. In addition, the use of 2-octyl yielded better patient satisfaction and also was less costly compared to no skin adhesive. Our study exhibited that 2-octyl was a safe and effective wound closure technique for patients undergoing TKA.Trial registrationThis study has been registered at Clinical Trials. Gov (No. ChiCTR210046442).

Molecular Investigation of the Self-Assembly Mechanism Underlying Polydopamine Coatings: The Synergistic Effect of Typical Building Blocks Acting on Interfacial Adhesion.

Polydopamine (PDA) is well known as a mussel-inspired adhesive material composed of oligomeric heteropolymers. However, the conventional eumelanin-like structural assumption of PDA seems deficient in explaining its interfacial adhesion. To determine the decisive mechanism of PDA coating formation, experiments and simulations were performed in this study. 5,6-Dihydroxyindole (DHI), the signature building block of eumelanin, was introduced as the control group. Various typical building blocks in PDA were quantified by physicochemical characterizations, and the polar-group-dominated interfacial interaction was evaluated by classic molecular dynamics and metadynamics methods. Aminoethyl has been proven to be the key functional group inducing the adsorption of PDA on the hydroxylated silica substrates, while DHI shows limited adhesion to the substrate due to the absence of aminoethyl as the catechol-indole structure of DHI exhibits poor affinity to the silica surface. Pyrrole carboxylic acid, as an oxidative product detected from PDA/DHI, is unfavorable for its adhesion to silica substrates. Overall, the coating formation and self-aggregating precipitation of PDA are two competitive aminoethyl-consuming paths; thus, the in situ oxidative coupling of dopamine is indispensable for the PDA coating preparation. The collected PDA precipitates can no longer present satisfactory coating forming behavior, resulting from a shortage of aminoethyl moieties.

Biomimetic synthetic test system based on hydroxyapatite cement for adhesive strength evaluation of experimental mineral-organic bone adhesive materials.

The development of bone adhesive materials is a research field of high relevance for the advancement of clinical procedures. Despite this, there are currently no material candidates meeting the full range of requirements placed on such a material, such as biocompatibility, sufficient mechanical properties and bond strength under biological conditions, practical applicability in a clinical setting, and no adverse effect on the healing process itself. A serious obstacle to the advancement of the field is a lack in standardized methodology leading to comparable results between experiments and different research groups. Natural bone samples are the current gold-standard material used to perform adhesive strength experiments, however they come with a number of drawbacks, including high sample variability due to unavoidable natural causes and the impossibility to reliably recreate test conditions to repeat experiments. This paper introduces a valuable auxiliary test method capable of producing large numbers of synthetic test specimens which are chemically similar to bone and can be produced in different laboratories so to repeat experiments under constant conditions across laboratories. The substrate is based on a hydroxyapatite forming cement with addition of gelatine as organic component. Crosslinking of the organic component is performed to improve mechanical properties. In order to demonstrate the performance of the developed method, various experimental and commercial bone/tissue adhesive materials were tested and compared with results obtained by established methods to highlight the potential of the test system.

Improving mode I fracture response of glass fiber-epoxy composite adhesive joints using sanding treatment and MWCNTs inclusion

This study investigates the enhancement of fracture behavior in laminated composites using a combination of surface treatments and nanomaterial incorporation. The adherent material used is glass fiber-reinforced polymer (GFRP), and the surface treatment was applied to the GFRP surface. The adhesive used in the joints is an epoxy-based adhesive, which was reinforced with Multi-Walled Carbon Nanotubes (MWCNTs) to improve its mechanical properties. Initially, mechanical sanding techniques were explored, revealing significant improvements of 55% in fracture energy and 38% in load-bearing capacity with optimal 240-grit sanding. Subsequently, MWCNTs were introduced at varying weight percentages (0.1%, 0.3%, and 0.5%) into the adhesive. This combined approach aimed to synergistically examine the impact of surface pretreatments and nanoparticle integration on the fracture behavior of the GFRP joints. Results highlight the potential for fracture resistance and enhanced load-carrying capabilities in reinforced specimens, with maximum load and fracture energy improvements of up to 92% and 50%, respectively, compared to unreinforced specimens and those subjected solely to sanding treatments. Moreover, the shift in failure mode from adhesive failure to cohesive substrate failure was observed and is attributed to the enhanced bonding area created by the 240-grit sanding and the increased fracture resistance from the incorporation of 0.3 wt% MWCNTs. The inclusion of MWCNTs provides additional toughening mechanisms such as crack bridging and pull-out, which significantly increase the fracture energy. This comprehensive investigation underscores the intricate interplay between mechanical preparation and nanomaterial incorporation in significantly improving the performance of laminated composites.

Optimal Hydrofluoric Acid Etching Duration and Impact of Silane/Adhesive on Profilometric Properties and Bonding to Lithium Disilicate Glass Ceramics.

This study aimed to assess the surface roughness, surface free energy (SFE), and shear bond strength (SBS) on a lithium disilicate glass-ceramic surface following varying etching protocols (time variation) and application of silane either with or without adhesive material. Lithium disilicate glassceramic (LDGC) computer-aided design and computer-aided manufacture (CAD/CAM) blocks were cut using a slow-speed cutting mechanism. CAD/CAM blocks were then evaluated for surface roughness, 6 groups (n=20); SFE,12 groups (n=5); and SBS, 10 groups (n=10). The cut CAD/CAM blocks were randomly allocated to 28 groups. Groups were based on the following: 30 or 90 seconds of etching with 9% hydrofluoric acid (HF); application or absence of silane coupling agent (Sil); and application or absence of adhesive (Adh).The control group (Cont) had untreated surfaces. Unetched surfaces were surveyed with only silane (Sil), only adhesive (Adh), or silane+adhesive (SilAdh). Further etched groups were HF30 with HF for 30 seconds, HF30-Sil, HF30-Adh, and HF30-SilAdh. Alternative 90-second etching times produced similar groups: HF90, HF90-Sil, HF90-Adh, and HF90-SilAdh. A digital profilometer was used to assess the surface roughness of specimens, and two readings were recorded. Sessile drop analysis was used to examine SFE specimens, and the OWRK model was modified to measure liquid surface tension. A universal testing machine (UltraTester, Ultradent Products, Inc, South Jordan, UT, USA) was utilized for the SBS test, with the crosshead speed set at 0.5 mm/min until failure. Representative treated specimens from each group were submitted to surface morphological evaluation and chemical analysis using scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDXS) (n=3). After data collection, evaluation using one- or two-way analysis of variance and the post-hoc Tukey test (α=5%) was conducted. A longer etching time of 90 seconds produced a rougher surface. After the 90-second etching process, SFE displayed the greatest values; nevertheless, the use of silane did not affect SFE. For every group examined, the application of silane followed by adhesive resulted in an increase in SBS and more stable bonding over time. SEM/EDXS showed that etching times did affect the amount of cerium on the surface and altered surface morphology. Higher and more consistent bond strengths have been observed with longer etching periods. Silane and adhesive application on the ceramic surface showed stronger and enhanced bond strength, specifically when longer etching times were employed.

Branched Oligomer-Based Reversible Adhesives Enabled by Controllable Self-Aggregation.

Supramolecular adhesion material systems based on small molecules have shown great potential to unite the great contradiction between strong adhesion and reversibility. However, these material systems suffer from low adhesion strength/narrow adhesion span, limited designability, and single interaction due to fewer covalent bond content and action sites in small molecules. Herein, an ultrahigh-strength and large-span reversible adhesive enabled by a branched oligomer controllable self-aggregation strategy is developed. The dense covalent bonds present in the branched oligomers greatly enhance adhesion strength without compromising reversibility. The resulting adhesive exhibits a large-span reversible adhesion of ≈140 times, switching between ultra-strong and tough adhesion strength (5.58MPa and 5093.92Nm-1) and ultralow adhesion (0.04MPa and 87.656Nm-1) with alternating temperature. Moreover, reversible dynamic double cross-linking endows the adhesive with stable reversible adhesion transitions even after 100 cycles. This reversible adhesion property can also be remotely controlled via a voltage of 8V, with a loading voltage duration of 45s. This work paves the way for the design of reversible adhesives with long-span outstanding properties using covalent polymers and offers a pathway for the rational design of high-performance adhesives featuring both robust toughness and exceptional reversibility.

Analisis Studi Kelayakan Usaha Briket Limbah Tongkol Jagung

The use of energy resources that are not environmentally friendly is a problem in Indonesia today. Briquettes are also the primary material because they are abundant, and the primary material has yet to be optimally utilized, including corn cobs. The purpose of this study is to analyze the economic feasibility of corn cob waste briquettes in this study using data analysis of technological technical aspects, financial feasibility analysis such as Payback Period (PP), Net Present Value (NPV), Internal Rate of Return (IRR) and Benefit and Cost Ratio (B/C). The results showed that it takes 19,800 kg of corn cobs to produce charcoal, as much as 3,168 kg and 158.4 kg with tapioca starch adhesive material, as much as 5% of the total weight of charcoal powder, requiring four pieces of equipment, namely pyrolyzer machines, Hammer mills, Planetary mixers, and Tray dryers. Furthermore, the feasibility analysis of this corn cob briquette business was declared feasible with the four categories: Payback Period (PP) for 3.1319 years, Net Present Value (NPV) of Rp 28,129,336,212; IRR of 17.77%, and Net B/C of 1.55. The corn cob briquette agro-industry will remain profitable even if the production capacity decreases by 28% from the original capacity. The agro-industry can also still operate despite an 8% decrease in the selling price of briquettes and will remain profitable if raw materials increase by 17%.

Mechanisms of the effect of high-performance ester composite materials on plant growth under soilless conditions

The utilization of high-performance ester materials in addressing soil erosion and conserving water remains a crucial area of research in soil remediation. Currently, however, the mechanism underlying the role of these materials in vegetation restoration remains unclear, hampering the accurate determination of the optimal ratio of high-performance ester composite materials for soil enhancement. To address this issue, this study examines the mechanism of how high-performance ester composite materials affect the germination and growth of plant seeds through soilless cultivation experiments. The results revealed that the high-performance ester composite materials significantly enhanced seed germination ability and fostered plant seedling growth. Notably, the promotional effects of the ester adhesive and water-retaining materials within the high-performance ester composite varied. Specifically, the adhesive material significantly spurred radicle development, while the water-retaining material significantly accelerated germ growth. Varying concentrations of adhesive materials exerted distinct effects on plant growth. In particular, a small amount of adhesive materials enhanced seed germination, whereas excessive amounts exhibited inhibitory effects. Consequently, the optimal adhesive materials dosage conducive to plant growth and the optimal weight ratio of adhesive to water-retaining materials were ascertained. Additionally, the underlying mechanism of high-performance ester composite materials influence plant growth was elucidated. Overall, this research offers a theoretical foundation for the optimal ratio adjustment of high-performance ester composite materials to optimize soil improvement efforts.

Variable stiffness performance analysis of layer jamming actuator based on bionic adhesive flaps

Soft actuators made of soft materials cannot generate precisely efficient output forces compared to rigid actuators. It is a promising strategy to equip soft actuators with variable stiffness modules of layer jamming mechanism, which could increase their stiffness as needed. Inspired by the gecko's the array of setae, bionic adhesive flaps with inclined micropillars are applied in layer jamming mechanism. In this paper, after the manufacturing process of the layer jamming actuator based on the bionic adhesive flaps is described, the equivalent stiffness models of the whole actuator are established in the unjammed and jammed states. And the shear adhesive force of a single micropillar is calculated based on the Kendall viscoelastic band model. The finite element simulation results of two bionic adhesive flaps show that the interlaminar shear stress and stiffness increase with the increase of pressure. The measurement of shear adhesive force show that the critical shear adhesive force of the bionic adhesive material is 3.2 times that of polyethylene terephthalate (PET) material, and exhibit the ability of anisotropic adhesion behavior. The variable stiffness performance of the layer jamming actuator based on bionic adhesive flaps is evaluated by three test methods, and the max stiffness reaches 8.027 N mm-1, which is 1.5 times higher than the stiffness of the layer jamming actuator based on the PET flaps. All results of simulation and experiment effectively verify the validity and superiority of applying the bionic adhesive flaps to the layer jamming mechanism to enhance the stiffness.

Experimental study on the fatigue behavior of CFRP-strengthened cracked steel plates under eccentric axial tension

In this paper, an experimental investigation has been conducted to study the fatigue behavior of single edge-notch steel plates strengthened with CFRP (laminates/sheets). The plates have been subjected to eccentric fatigue under axial loading conditions. The experimental study includes fourteen specimens and has been tested under axial loading until failure. The constant parameters in the study are steel material grade, steel plate dimensions, and fatigue loading conditions. Meanwhile, the studied parameters are steel plate initial edge crack size, CFRP configurations (length, one or two-sided, and laminates or sheets), and adhesive material strength. The experimental results revealed that the fatigue life for specimens strengthened with CFRP sheets or CFRP laminates can be improved by a factor of 1.15 to 3.87 and 1.47 to 6.32, respectively, compared with the un-strengthened specimens. The results show that using CFRP can be considered an efficient way to repair the initial cracks in steel elements under eccentric axial fatigue loading.

FSW of AA2024: effects of tool wear on energy consumption

ABSTRACT This study shows that the progressive adhesion of weld material to the tool in friction stir welding AA 2024-T3, up to tool saturation, brings about a decrease in power consumption until a plateau is reached. The cause of this behavior is the hindering of the stirring action of the tool due to the material accumulated on it. The built-up material changes the nature of the tool/material interaction and then the friction condition at their interface. The direct consequence is a decrease in the shearing strain and therefore in the heat generated by friction. Bits of this adhering material break off from the tool at intervals. Macro and micro detachments are identified. Micro-detachments happen continuously at small periodic intervals and produce vibrations. The amplitude of these vibrations increases in all their characteristic spectral components up to tool saturation. Macro-detachments generate oscillations in power consumption and leave galling on the weld bead.

Self-adhesive fiberboards fabricated from waste bamboo powder through biological pretreatment

Using renewable and sustainable agricultural and forestry wastes to produce bio-based materials is an effective approach for significantly reducing the environmental pollution caused by petroleum-based materials such as plastics and chemical fibers. This research aims to develop a cleaning process for large-scale production of high-performance green bio-based materials without the use of any chemical binders. The mechanical properties of self-adhesive fiberboards are improved through pretreatment with white rot fungi. By pretreating bamboo powder with biological factors like sugars and laccase produced by white rot fungi under high temperature and pressure, lignin-active molecules are formed on the surface. These active molecules can reconstruct chemical bonds between multi-fiber materials, thereby exhibiting biological adhesion. The reconfiguration of lignin molecules on the material's surface also helps prevent rapid water penetration. After biological pretreatment, the surface of bamboo powder forms a concave-convex structure, effectively increasing the area of biological adhesion during hot-pressing conditions. Compared to regular bamboo powder control samples, bio-pretreated fiberboards showed an increase in modulus of rupture (MOR) by 83.33 % and modulus of elasticity (MOE) by 100.79 %. In contrast to traditional fossil-based adhesive synthetic materials, the findings of this study circumvent the emission of harmful volatiles from chemical adhesives while effectively substituting petroleum-based synthetic materials that necessitate diverse chemical additives, which are in alignment with the principles of environmental protection and sustainable development.

Dopamine-modified hyaluronic acid (DA-HA) as a novel dopamine-mimetics with minimal autoxidation and cytotoxicity

Dopamine-modified hyaluronic acid (DA-HA) has been initially developed as an efficient coating and adhesion material for industrial uses. However, the biological activity and safety of DA-HA in the brain have not been explored yet. Here, we report a series of evidence that DA-HA exhibits similar functionality as dopamine (DA), but with much lower toxicity arising from autoxidation. DA-HA shows very little autoxidation even after 48-h incubation. This is profoundly different from DA and its derivatives including l-DOPA, which all induce severe neuronal death after pre-autoxidation, indicating that autoxidation is the cause of neuronal death. Furthermore, in vivo injection of DA-HA induces significantly lower toxicity compared to 6-OHDA, a well-known oxidized and toxic form of DA, and alleviates the apomorphine-induced rotational behavior in the 6-OHDA animal model of Parkinson's disease. Our study proposes that DA-HA with DA-like functionalities and minimal toxicity has a great potential to treat DA-related disease.

Bio-based Benzoxazine-Containing Polycyclosiloxanes as Flame-Retardant Adhesive Materials

Bio-based Benzoxazine-Containing Polycyclosiloxanes as Flame-Retardant Adhesive Materials

Evaluation of coating materials on the characterization of size and viability of virus-laden particles collected with an Andersen cascade impactor

Airborne pathogens are typically associated with particles, and the transport behavior of these particles is largely driven by their size. To better understand airborne transmission of viral diseases and develop effective control measures, proper size characterization of virus-laden particles is essential. The Andersen cascade impactor (ACI) is an 8-stage air sampler that separates aerosol particles into 9 aerodynamic size fractions. During sampling with an ACI under certain conditions, particles may bounce upon impact with the collection plates of the ACI, leading to eventual deposition on a stage further downstream than their target stage. Coating collection plates with adhesive materials may help decrease particle bounce; however, it may also affect the viability of collected pathogens. In this study, we evaluated different materials for their ability to minimize particle bounce while conserving virus viability during the collection of viral aerosol particles with an ACI. We evaluated nine materials - Tween® 80, silicone oil, Span® 85, Brij® 35, glycerol, mineral oil, gelatin, bovine serum albumin, and virus growth media - on their effect to inactivate H1N1 influenza virus and bovine coronavirus, a surrogate of SARS-CoV-2. Plates coated with gelatin, silicone oil, and mineral oil resulted in the least reduction of viability for both viruses. These materials were then used to sample viral aerosol particles in a wind tunnel. Results of physical particle collection, viral load and viral viability from the various ACI stages revealed no significant differences in aerodynamic size distribution between coated and uncoated plates, and the size distribution was similar to that reported by an optical particle sizer. Overall, our results did not support the need to coat ACI collection plates when characterizing viral aerosol particles under the conditions of this study. However, we did identify potential coating materials which could conserve virus viability maximally, if particle bounce is of concern.

Formulation of optimized TCA using PDMS epoxy and Ag-coated PMMA for high-efficiency Si tandem solar cell applications

In this study, we aimed to develop and characterize Transparent Conductive Adhesive (TCA) materials for mechanically stacked tandem solar cell applications. The research objectives were to enhance the transparency, conductivity, and adhesive strength of TCAs to improve the efficiency and practicality of tandem solar cells. The TCA formulation comprises a combination of polymers and Ag-coated particles, with flexible poly-methyl methacrylate (PMMA) micro-spheres serving as conductive particles and SYLGARD 184 silicon elastomer poly-di-methyl-siloxane (PDMS), mixed in a 10:1 ratio of base to curing agent, serving as the transparent adhesive. We conducted systematic experiments with Ag-particle coverage areas ranging from 0.34 % to 21.61 % at temperatures of 80 °C and 100 °C, under 500 mb pressure. The optimal conductivity was achieved at 2 wt% Ag-particle coverage, measuring 5.26 × 10⁷ S/m, with over 93 % transparency. These key results indicate the significant potential of the optimized TCA in enhancing the performance of mechanically stacked tandem solar cells, thus contributing to the advancement of renewable energy technologies.

Ultrasonic signal classification for composite materials via deep convolutional neural networks

ABSTRACT Ultrasonic testing (UT) is the most commonly used non-destructive testing method in the aerospace field. However, for the detection of delamination defect in multi-layer composite adhesive materials with metal and non-metal bonding, traditional energy statistics methods are limited and cannot achieve high-precision automatic signal classification. This article proposes a signal classification model based on hybrid neural networks. By studying the classification accuracy of convolutional neural networks (CNN) and long short-term memory networks (LSTM) for different types of signals, a relatively balanced classification is achieved, which effectively improves the classification accuracy. By integrating attention mechanisms, the ability of the detection model to identify key features is further enhanced. Experimental results demonstrate that the proposed model achieves an accuracy of 98.57%. Bayesian Optimisation (BO) can effectively and automatically select the optimal hyperparameters, and achieve global optimisation. In the experiment, the accuracy increased by 0.73% compared to the benchmark value. Comparative experiments show that the signal classification model established in this paper has good performance.