Contact Materials Research Articles

Enhanced anti-welding and arc erosion performance of Ag-8 wt%SnO2 contact material with different addition of graphene nanoplatelets

To improve the welding resistance of Ag-8 wt%SnO2 contact material at large current, the graphene nanoplatelets (GNPs) was selected as the additive, and Ag-8 wt%SnO2 contact materials with different GNPs addition were prepared by powder metallurgy route. The electrical contact tests were performed under 36 V/16 A and 36 V/25 A, the welding, material transfer behavior and their mechanism were investigated combined with the analysis of arc duration, arc power and eroded morphology. The results show that 0.2 wt% GNPs addition decreases the welding frequency and welding force significantly, this can be attributed to the arc extinction effect and the weaken effect of the welding area. However, the excessive GNPs addition in turn aggravates the welding, the reason is that excessive GNPs addition weakens the bond between eroded layers, resulting in the decrease of arc stability and the generation of the small protrusion which cause the concentration of the contact stress and the electric field, which further results in the serious welding. Furthermore, 0.2 wt% GNPs addition decreases the mass loss rate, increasing the combination performance of Ag-8 wt%SnO2 contact material.

A Superhuman Sensing Triboelectric Nanogenerator with Boosted Power Density and Durability via a Bio‐Inspired Janus Structure

AbstractTriboelectric nanogenerators (TENG) not only enable sustainable self‐powered sensing of devices, but also have superhuman noncontact/contact identification capabilities, which are propelling humanity toward the intelligent era. However, the inherently low dielectric constant of triboelectric materials as well as the mechanical mismatch between electrodes and dielectric materials severely limited their efficient and stable output performance. Taking inspiration from the asymmetric structure and function of human skin, a novel single‐electrode TENG is developed, whose electrode and dielectric layer are integrated in a Janus architecture. By tuning the balance between gravity and the internal noncovalent interactions, gradient dispersion of carbon nanotubes in waterborne polyurethane networks can be feasibly achieved, which can boost the device performance by reinforcement in both the charge trapping capacity of the dielectric layer and the charge transfer of the electrode layer. As a proof‐of‐concept, triboelectric sensing and deep learning are integrated to realize the evolution from perception to identification under both noncontact (motion prediction) and contact (material identification) modes. The bionic design strategy of gradient Janus film can offer valuable insights into improving the output performance and durability of TENG. Additionally, the proximal prediction and tactile identification functions are also desirable attempts for future human‐machine interfaces.

Multi-build orientation effects on microstructural evolution and mechanical behavior of truly as-built selective laser melting Ti6Al4V alloys

The unique combination of lightweight, strength, corrosion resistance, high-temperature resistance, and biocompatibility make Ti6Al4V alloy an important material in metal contact of solar cells, and selective laser melting (SLM) enables the production of Ti6Al4V parts complex geometries that would be difficult or impossible to produce using traditional manufacturing methods. The build orientation of SLM process presents an essential effect on the quality of the produced parts, and thus, in this study it investigates the impact of multi-build orientation (0°, 30°, 45°, 60°, 90°) on the microstructural evolution and mechanical behavior of truly as-built Ti6Al4V alloys produced by SLM. The microstructure analysis revealed the presence of ordered subsurface pores, located at a distance of about 50 μm–150 μm from the sample surface. The microstructure consisted primarily of α′ martensite with a small amount of β phase. Massive transformation was observed in the 30° and 45° samples, with corresponding grain sizes of 5 μm and 10 μm, respectively. To be specific, the content of β phase and ultimate tensile strength (UTS) varied with the sample orientation, and the 45° build orientation exhibited the highest content of β phase with value of approximately 2.8%, but also the lowest UTS and elongation, which were 1161 MPa and 3.99%, respectively.

Mechanistic Insights into Propylparaben Sorption on Polyvinyl Chloride

The mechanism of loss of propylparaben potency from formulations when in contact with polyvinyl chloride has been determined. It is caused by the adsorption of propylparaben onto polyvinyl chloride surfaces. The adsorption kinetics is best described using a pseudo-second order model based on non-linear fit. The rate of adsorption increases with increasing bulk concentration of propylparaben. Adsorption equilibrium isotherm was fitted to three isotherm models: Langmuir, Freundlich, and Temkin, using non-linear fit. The Freundlich and Temkin models show the best fit, indicating a multi-layer adsorption. Using this case study, we present a methodology to provide mechanistic insights into the compatibility data between pharmaceutical ingredients and product contact materials when sorption is involved.

Analysis and research on the dynamic characteristics of shock absorber based on ADAMS

In order to effectively improve safety and stability during transportation, a shock absorber with buffering and self-locking functions was designed. Based on the rigid flexible coupling technology, the working state and dynamic response of the shock absorber were simulated and analyzed. The linear spring was treated as a flexible body, and the cam button, guide pillar, and base were treated as rigid bodies. The modal neutral files required for the rigid flexible coupling dynamic analysis were generated. Based on ADAMS, a dynamic simulation model was established, replacing a part of the rigid model with a flexible model and conducting load response analysis on it. To further improve the vibration reduction effect, the performance of the contact material of the shock absorber was analyzed. Through the calculation of dynamic characteristics, it could be known that the self-locking mechanism had no dead points, and the vibration reduction force response stability was high, meeting the working requirements.

Computational Insights into Phase Equilibria between Wide-Gap Semiconductors and Contact Materials

Computational Insights into Phase Equilibria between Wide-Gap Semiconductors and Contact Materials

Influence of PET as single-use contact material on gloss and surface properties of chocolate

Polyethylene terephthalate (PET) is a commonly used polymer in many industry sectors including confectionery industry. In the latter, PET is utilized for single-use moulds for chocolate manufacturing. Despite the broad application of PET in these areas, information regarding its influence on chocolate gloss and surface properties is not available. Meanwhile, it is already well established that fat crystal modification influence these properties (including gloss) distinctly. To bridge this disparity, this study examined how amorphous and glycol-copolymerized PET sheets influence non-pre-crystallised and pre-crystallised dark chocolate properties throughout a 28-day storage period. Polymorphic properties of cocoa butter were analysed via DSC. Non-pre-crystallised and pre-crystallised chocolate surfaces were characterised regarding colour, gloss, polarity, adhesion, roughness, and topography. While pre-crystallised chocolate shows consistent results, non-pre-crystallised chocolate experiences considerable changes in surface properties due to fat crystal transitions during storage. The findings show that the polymorphic state had a major impact on chocolate surface properties. Furthermore, results demonstrated that the type of PET had a significant impact on chocolate surface properties as well. Pre-crystallised chocolate gloss was significantly impacted by the choice of PET contact material. As a result, pre-crystallised chocolates exhibited a larger tendency to gloss inhomogeneities following amorphous PET monolayer sheet contact.

Passivating Contacts for Crystalline Silicon Solar Cells: An Overview of the Current Advances and Future Perspectives

AbstractSolar photovoltaics (PV) are poised to be crucial in limiting global warming by replacing traditional fossil fuel generation. Within the PV community, crystalline silicon (c‐Si) solar cells currently dominate, having made significant efficiency breakthroughs in recent years. These advancements are primarily due to innovations in solar cell technology, particularly in developing passivating contact schemes. As such, this review article comprehensively examines the evolution of high‐efficiency c‐Si solar cells, adopting a historical perspective to investigate the advancements in passivation contact techniques and materials to state‐of‐the‐art cell designs. Additionally, this work deeply studies the recent advances and critical design principles underlying each developed passivation scheme. Eventually, this work identifies existing challenges and proposes insights into future directions for c‐Si solar cells through diverse passivating contact strategies.

Safety assessment of mixtures of 1,9-nonanediamine (NMDA) and 2-methyl-1,8-octanediamine (MODA), for use in food contact materials.

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of mixtures of 1,9-nonanediamine (NMDA) and 2-methyl-1,8-octanediamine (MODA) when used to produce polyamide food contact materials for contact with all food types for long-term storage at room temperature and below, including heating up to 121°C for up to 2 h. The polyamide material is also intended to be used for repeated use up to 121°C with short contact (up to 30 min). The polymer typically contains ■■■■■ of a low molecular weight fraction (LMWF, < 1000 Da). The specific migration was measured with polyamide samples in a set of migration tests with 3% acetic acid and 10% ethanol. NMDA and MODA were not detected at ■■■■■, respectively. The specific migration of the LMWF consisting of NMDA/MODA-related species was up to ■■■■■. The overall migration in olive oil was below the detection limit (3 mg/dm2). The most abundant migrating LMWF oligomers were identified. Toxicological studies were performed with NMDA, MODA and with polyamide formulations enriched in the LMWF. The results of genotoxicity assays did not raise a concern. From a repeated-dose oral 90-day toxicity study in rats, the Panel identified a no observed adverse effect level (NOAEL) of 1000 mg/kg body weight per day for the migrating LMWF. The CEP Panel concluded that NMDA/MODA mixtures do not raise a safety concern for the consumer when used as comonomer with terephthalic acid to manufacture polyamide articles intended for contact with all food types, except for infant formula and human milk, if the migration of NMDA and MODA does not exceed 0.05 mg/kg food (as a sum of the two substances) and if the migration of the LMWF consisting of NMDA/MODA-related species does not exceed 5 mg/kg food.

Safety assessment of the substance 'phosphorous acid, triphenyl ester, polymer with 1,4-cyclohexanedimethanol and polypropylene glycol, C10-16 alkyl esters', for use in food contact materials.

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids (CEP) assessed the safety of the substance 'phosphorous acid, triphenyl ester, polymer with 1,4-cyclohexanedimethanol and polypropylene glycol, C10-16 alkyl esters', when used as an additive in all types of polyolefins. The substance is a polymer containing ≤ 13% w/w of a low molecular weight fraction (LMWF, < 1000 Da). A polyethylene sample with 0.15% w/w of the substance was used in a comprehensive set of migration tests with food simulants. The specific migration was up to 0.014 and 0.023 mg/kg in 4% acetic acid and 10% ethanol, respectively. Migration into olive oil was estimated by the Panel to be up to 5.3 mg/kg under worst-case conditions of use. The migrating LMWF species were comprehensively identified. Those without phosphorous were either without alerts for genotoxicity or listed in Regulation (EU) 10/2011 with worst-case migrations well below their respective specific migration limits. Toxicological studies were performed using phosphite and phosphate versions of the substance enriched in its LMWF. The substance does not raise a concern for genotoxicity. From a repeated dose 90-day oral toxicity study in rats with a 50:50 phosphite:phosphate blend, the Panel identified a NOAEL of 250 mg/kg bw per day for each component of the blend. No delayed neurotoxicity in hens was observed. The CEP Panel concluded that the substance does not raise a safety concern for the consumer if its LMWF is not higher than 13% w/w, if it is used at up to 0.15% w/w in polyolefin materials and articles intended for contact with all food types, except for infant formula and human milk, for long-term storage at room temperature and below, after hot-fill and/or heating up to 100°C for up to 2 h, and if its migration does not exceed 5 mg/kg food.

Simulation Calculation and Experimental Study on the Properties of Re-, In-, and Nb-Doped Ag/Ni Electrical Contact Materials

Simulation Calculation and Experimental Study on the Properties of Re-, In-, and Nb-Doped Ag/Ni Electrical Contact Materials

Safety assessment of the substance calcium tert-butylphosphonate for use in food contact materials.

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids assessed the safety of calcium tert-butylphosphonate, which is intended to be used as a nucleating agent up to 0.15% w/w for the manufacture of polyolefin food contact materials (FCM) and articles for single and repeated use, in contact with all types of food, including infant formula and human milk. Specific migration was tested using polyethylene samples in 10% ethanol, 3% acetic acid and 95% ethanol for 2 h at 100°C, followed by 238 h at 40°C. Results for all three simulants were near or below the limit of detection of 10 μg/kg. As the solubility of the substance is far above the reported migration and above 60 mg/kg food, no assessment of the particle fraction was needed, and the conventional risk assessment was followed. The substance did not induce gene mutations in bacterial cells and structural chromosomal aberrations in mammalian cells, thus, did not raise concern for genotoxicity. The Panel considered that the use of the substance did not give rise to safety concern related to neurotoxicity for the general population, but this conclusion could not be applied to infants below 16 weeks of age, due to their specific sensitivity and the absence of dedicated data. The Panel concluded that calcium tert-butylphosphonate does not raise a safety concern for the consumer if it is used as a nucleating agent up to 0.15% w/w in the manufacture of polyolefin FCM that are intended to be in contact with all types of food for storage above 6 months at room temperature and below, including temperatures up to 100°C for maximum 2 h and up to 130°C for short durations. The Panel could not evaluate the safety of use to manufacture FCM for contact with infant formula and human milk.

Safety assessment of the process Martogg Group, based on the EREMA Advanced technology, used to recycle post-consumer PET into food contact materials.

The EFSA Panel on Food Contact Materials, Enzymes and Processing Aids assessed the safety of the recycling process Martogg Group (EU register number RECYC321), which uses the EREMA Advanced technology. The input material is ■■■■■ washed and dried poly(ethylene terephthalate) (PET) flakes originating from collected post-consumer PET containers, including no more than 5% PET from non-food consumer applications. The flakes are heated in continuous reactors ■■■■■ before being extruded. Having examined the challenge test provided, the Panel concluded that the continuous decontamination steps (Steps 2 and 3), for which a challenge test was provided, are critical in determining the decontamination efficiency of the process. The operating parameters to control the performance of this step are temperature, pressure and residence time. It was demonstrated that this recycling process is able to ensure a level of migration of potential unknown contaminants into food below the conservatively modelled migration of 0.1 μg/kg food derived from the exposure scenario for infants when such recycled PET is used at up to 100%. Therefore, the Panel concluded that the recycled PET obtained from this process is not of safety concern when used at up to 100% for the manufacture of materials and articles for contact with all types of foodstuffs, including drinking water, for long-term storage at room temperature or below, with or without hotfill. Articles made of this recycled PET are not intended to be used in microwave or conventional ovens and such uses are not covered by this evaluation.

Investigating the sources and fate of per- and polyfluoroalkyl substances (PFAS) in food waste compost

Composting municipal food waste is a key strategy for beneficially reusing methane-producing waste that would otherwise occupy landfill space. However, land-applied compost can cycle per- and polyfluoroalkyl substances (PFAS) back into the food supply and the environment. We partnered with a pilot-scale windrow composting facility to investigate the sources and fate of 40 PFAS in food waste compost. A comparison of feedstock materials yielded concentrations of ∑PFAS under 1 ng g−1 in mulch and food waste and at 1380 ng g−1 in leachate from used compostable food contact materials. Concentrations of targeted ∑PFAS increased with compost maturity along the windrow (1.85–23.1 ng g−1) and in mature stockpiles of increasing curing age (12.6–84.3 ng g−1). Among 15 PFAS quantified in compost, short-chain perfluorocarboxylic acids (PFCAs) – C5 and C6 PFCAs in particular – led the increasing trend, suggesting biotransformation of precursor PFAS into these terminal PFAS through aerobic decomposition. Several precursor PFAS were also measured, including fluorotelomer carboxylic acids (FTCAs) and polyfluorinated phosphate diesters (PAPs). However, since most targeted analytical methods and proposed regulations prioritize terminal PFAS, testing fully matured compost would provide the most relevant snapshot of PFAS that could be land applied. In addition, removing co-disposed food contact materials from the FW feedstock onsite yielded only a 37 % reduction of PFAS loads in subsequent compost, likely due to PFAS leaching during co-disposal. Source-separation of food contact materials is currently the best management practice for meaningful reduction of PFAS in food waste composts intended for land application.

Enhanced arc erosion and dynamic welding resistance of Ag-10 wt%Ni@Gr contact material

In this work, a novel hybrid reinforcement Ni@Gr was successfully synthesized by graphene in-situ grown on the surface of Ni particles, and the Ag-10 wt%Ni@Gr contact material was prepared by the combined methode of wet mixing and spark plasma sintering. The effect of graphene incorporation on the electrical performance of Ag-10 wt%Ni@Gr contact material was investigated, and the arc erosion mechanism was discussed as well. As compared to the Ag-10 wt%Ni contact material, the make-arc energy, break-arc energy and the maximum welding force of the Ag-10 wt%Ni@Gr contact material are decreased by 13.2 %, 4.9 %, and 23.1 %, respectively. Moreover, the Ag-10 wt%Ni@Gr contact material displays smaller erosion area, lower surface roughness and less mass loss. It can be ascribed to the increased elastic modulus of the contact surface, reduced bounce effect, lowered make-arc energy and shortened the make-arc duration that are stemmed from the incorporation of graphene. In addition, the incorporation of graphene contributes to the enhanced molten pool viscosity, which can effectively restrain Ag splashing, thereby enhancing arc erosion resistance and welding resistance.

Examining primary aromatic amines' stability in aqueous food simulants: effects of 3% acetic acid and water test conditions

Primary aromatic amines (PAAs) may be found in food contact materials and can potentially migrate from packaging material into the packed foodstuffs. Certain members of this substance class are of particular concern due to their toxicological properties. Legislators and authorities require a risk assessment regarding the transfer of PAAs into food. The evaluation of PAAs’ migration into food relies on migration or extraction tests using aqueous and acidic food simulants or solvents. However, PAAs exhibit stability issues in acidic media, which could lead to an underestimation of migration. Therefore, a systematic stability study was conducted for 28 PAAs in 3% acetic acid and water at different storage conditions. Standard solutions of 2 and 10 ng/ml of the amines in these media were prepared and stored under the following conditions: 2 h at 40 °C, 70 °C, and 100 °C, and 10 days at − 20 °C, 4 °C, 20 °C, 40° C, and 60 °C. The test solutions were analyzed using liquid chromatography coupled to mass spectrometry, and recovery was calculated against freshly prepared standard solutions. It was found that several PAAs undergo a loss of recovery under the investigated conditions; 7 of the substances were identified to be the most unstable: 3,3ʹ-dimethoxybenzidine, 3,3ʹ-dimethylbenzidine, 6-methoxy-m-toluidine, 4-methoxy-m-phenylendiamine, 2,6-toluenediamine, benzidine and 2,4-toluenediamine. It was concluded that both time and storage temperature play a pivotal role in the stability of PAAs. The experiments also demonstrated that PAAs exhibit greater stability in water than in 3% acetic acid.

Influencing chocolate gloss inhomogeneities by the choice of surface-active substance and contact material

Gloss is an important criterion for chocolate quality and hence consumer acceptance. Gloss inhomogeneities, meaning glossy and matt spots on chocolate surfaces, remain a problem as they occur even after apparently optimal pre-crystallisation and cooling of chocolates. The presented study dealed with clarifying the complex interactions between dark chocolate with different surface-active substance (SAS) in contact with several mould materials by focusing on changes in chocolate surface properties and formation of gloss inhomogeneites. Contact materials used were polycarbonates (PC) and silicone. They varied in surface properties, specifically in roughness and surface free energy (SFE). PGPR, soy, and sunflower lecithin were used as SAS to alter the chocolate mass’ interface properties. Beside mould material’s surface properties, gloss (inhomogeneities), color, surface topography, roughness, and SFE were examined. Results showed that gloss and its inhomogeneities were significantly influenced by the contact material. Compared to PC, silicone had a significantly different impact on chocolate’s SFE and roughness. Topography images obtained by Atomic Force Microscopy revealed microstructural variations in the different gloss areas. Contact material and SAS had an impact on the microstructure as well. A statistical analysis further revealed that the contact materials' SFE and its dispersive share influence the formation of gloss inhomogeneites.

Analysis of per- and polyfluoroalkyl substances (PFAS) in raw materials intended for the production of paper-based food contact materials – evaluating LC-MS/MS versus total fluorine and extractable organic fluorine

Per- and polyfluoroalkyl substances (PFAS) analysis has become crucial due to their presence in the environment, their persistence and potential health risks. These compounds are commonly used in food contact materials (FCM) as a coating to provide water and grease-repellent properties. One of the pathways for PFAS to enter the human body is either through direct consumption of contaminated food or indirectly through migration from FCM into food. The purpose of this study was to investigate where the initial contamination of paper FCM occurs. We analysed paper material consisting of fresh fibre and secondary materials, intended to produce food packaging for the presence of PFAS. The samples were extracted and analysed for 23 different PFAS substances using the targeted approach with LC tandem mass spectrometry (LC-MS/MS). This analytical technique detects specific, easily ionisable PFAS with high sensitivity. However, one drawback of this approach is that it allows the identification of less than 1% of the PFAS known today. For this reason, we used combustion ion chromatography (CIC) to determine the content of extractable organic fluorine compounds (EOF) and compare it to the total fluorine content. The targeted analysis using LC-MS/MS measured an average sum concentration of PFAS of 0.17 ng g−1 sample. Our research shows that the primary PFAS contamination happens during the recycling process since all of the samples in which the targeted PFAS were measured belonged to the secondary material. The most frequently detected analytes were PFOA and PFOS, detected in 90% and 62% of the samples, respectively, followed by PFBS (in 29% of the samples). CIC showed that measured PFAS via LC-MS/MS amount to an average of 2.7 × 10−4% of total fluorine content, whereas the EOF was under the LOD in all of the measured samples. This result highlights the complexity of the accurate determination of PFAS compounds, displaying what kind of information the chosen methods provide.

Experimental Characterisation of BGBC OTFT for Indoor CO&lt;sub&gt;2&lt;/sub&gt; Gas Sensing

Global warming is a concern nowadays due to excessive release of harmful gasses to the environment, leading to greenhouse effect phenomena worldwide. Based on the data provided by global pollution agencies, the release of greenhouse gasses to the atmosphere is the main cause of pollution and the increase in atmospheric temperature due to warming. Greenhouse gasses (GHGs) contents released to the environment is worrying, with carbon dioxide (CO2) is reported at the highest concentration compared to other gasses. There are many studies conducted to develop and evaluate the performance of harmful gas sensors incorporating inorganic and organic semiconductive materials. Organic semiconductors (OSCs) are environmentally friendly materials, relatively cheaper technology, and comprised of a wide range of materials with good carrier mobility. Therefore, in this work, Organic Thin Film Transistor (OTFT) is developed for gas sensor application. As global warming is becoming more serious, this solution is instead a sustainable solution to the environment, as organic molecules which are held together via Van der Waals bond are easily processed via low-temperature deposition and solution processing as compared to more complicated processes involved in conventional inorganic counterpart. In addition, the developed sensor is generally robust due to the ability to withstand high humidity conditions and can be fabricated on flexible substrates. In this work, suitable materials are identified in basic OTFT construction, which are the electrodes, dielectric and substrate. The scope is mainly focusing on the development of bottom gate OTFT construction, incorporating p-type active material which are Trisisopropylsilylethynyl Pentacene (TIPS Pentacene), Aluminium (Al) as drain and source electrodes, PEDOT: PSS as gate electrode and Polyvinyl alcohol (PVA) as gate dielectric. The materials in bottom gate bottom contact (BGBC) configuration, fabricated via screen printing technique is experimentally tested towards CO2 detection. CO2 is initially detected at 1618 ppm with contact resistance of 15 kΩ, and at 10 ml/minute flow rate, the developed configuration is demonstrated able to achieve sensitivity of 2.069 Ω/ppm. In conclusion, the studied BGBC OTFT has demonstrated suitability and applicability in CO2 gas sensing for sustainable environmental condition monitoring, that could lead to safer environment for the living things on earth. With the proposed dimensions, in the future it is possible to proceed with this work to be fabricated by using more advanced techniques such as photolithography and many others.

Per- and Polyfluoroalkyl Substances in Food Packaging: Migration, Toxicity, and Management Strategies.

PFASs are linked to serious health and environmental concerns. Among their widespread applications, PFASs are known to be used in food packaging and directly contribute to human exposure. However, information about PFASs in food packaging is scattered. Therefore, we systematically map the evidence on PFASs detected in migrates and extracts of food contact materials and provide an overview of available hazard and biomonitoring data. Based on the FCCmigex database, 68 PFASs have been identified in various food contact materials, including paper, plastic, and coated metal, by targeted and untargeted analyses. 87% of these PFASs belong to the perfluorocarboxylic acids and fluorotelomer-based compounds. Trends in chain length demonstrate that long-chain perfluoroalkyl acids continue to be found, despite years of global efforts to reduce the use of these substances. We utilized ToxPi to illustrate that hazard data are available for only 57% of the PFASs that have been detected in food packaging. For those PFASs for which toxicity testing has been performed, many adverse outcomes have been reported. The data and knowledge gaps presented here support international proposals to restrict PFASs as a group, including their use in food contact materials, to protect human and environmental health.