Substrate Plate Research Articles

Additive manufacturing of a lightweight Al-Ca alloy by direct energy deposition and laser powder bed fusion

Abstract High strength and low density materials are needed to achieve lightweight design of components. Aluminum base metals alloyed with calcium are of potential interest because of the low density of calcium and its abundance. The additive manufacturing of dense and crack free samples out of an Al-10 wt.% Ca (Al-10Ca) alloy is presented. Both laser-based direct energy deposition (DED-LB) and laser powder bed fusion (LPBF) processes were applied to manufacture sample material. Preheating of the substrate plate is needed in LPBF to receive crack free samples. An analysis of the microstructure shows an Al-Al4Ca lamellar eutectic.

Residual Stress Measurements on Rectangular Specimen SS316L using Numerical Computation Software and Selective Laser Melting

This research aimed to predict the residual stress of additively manufactured rectangular specimen using Selective Laser Melting (SLM) by means of non-linear numerical computation based on Thermo-mechanical method (TMM). The procedure starts with the geometrical and material modelling of rectangular specimen with regards to Austenitic Stainless Steel 316L (SS316L) in which the temperature dependent material data properties such as Young’s Modulus, Thermal Expansion Coefficient, Specific Heat Capacity and Thermal Conductivity are taken into account. The next phase consists of numerical computation procedure which is where the specimen is position 60° of inclination angle from the substrate plate. The support structure is to be generated within the lower surface of the specimen in order to avoid material to collapse during printing process. Laser heat source is to be modelled based on the laser beam width, power, efficiency and scanning speed in order for the numerical computation to accurately predict the thermal problem in SLM process. Furthermore, layer parameters used to fabricate the specimen such as hatch distance, hatch scan width and layer thickness are taken into TMM consideration. Similar set-up from numerical computation by means of laser and layer parameters to fabricate SS316L rectangular specimen is utilized in real fabrication process using SLM machine, Renishaw RenAM 500E. After fabrication of the specimen, electropolishing as for the sample preparation for X-Ray Diffraction (XRD) measurement are to be conducted by means of various depth on both sides of the specimen. For the validation procedure, residual stress on every depth is to be analysed and compared with the result from numerical computation. In conclusion, TMM simulation forecasting an acceptable residual stress on SLM product with relative error up to 14% and the computational time taken to predict the residual stress is only 56 minutes. This exploratory research using TMM simulation to predict residual stress on SLM product could benefit metal additive manufacturing (MAM) production as a whole by neglecting expensive trial and error approach.

Analytical model of z-piezoelectric energy harvester for power generation from human physical activities

Human physical activities, viz., walking, jogging, jumping, etc on piezoelectric energy harvesters (PEH) have a great potential for the generation of free and clean energy. In the present work, an analytical model is developed to study the performance of a z-PEH, and the results were validated with numerical and experimental results. The distinctive features of the z-PEH are (a) it can be installed in a very small pavement/road surface area, (b) it results in very less damage to the road during installation, and (c) the repair and maintenance works can be carried out relatively easily. The power generation of the harvester can be enormously increased by increasing the number of unimorphs in the vertical (z) direction without increasing in the surface (x-y) directions, hence termed z-PEH. The harvester studied has four unimorphs. Each unimorph has a PZT-5A plate and an Aluminum substrate. The analytical and numerical studies resulted in a harvester with optimum dimensions for the PZT plate and Aluminum substrate of 20 × 20 × 0.4 mm3 and 65.1 × 20 × 1 mm3 respectively. Experiments were carried out on the optimum structure. The z-PEH, for an input deflection of 1 mm generated a maximum power of 0.84 mW, 0.88 mW and 0.80 mW from the proposed analytical model, numerical work and experiments respectively. The percentage of error between analytical and numerical results is 4.55% and between analytical and experimental results is 4.76%. An average human can generate a force of 490 N while walking, thereby allowing the use of 88 unimorphs in the z-PEH. From the analytical model, the resulted DC power of this harvester is 18.39 mW and the power density is 10.09 W m−3.

Simulation-based controlling of local surface temperature in laser powder bed fusion using the process laser

State-of-the-art laser powder bed fusion (PBF-LB/M) machines allow pre-heating of the substrate plate to reduce stress and improve part quality. However, two major issues have been shown in the past: First, with increasing build height the apparent pre-heat temperature at the surface can deviate drastically from the nominal pre-heat temperature in the substrate plate. Second, even within a single layer the local surface pre-heat temperature can show large gradients due to thermal bottlenecks in the part geometry underneath the top surface. Both lead to unwanted changes in microstructure or defects in the final parts. In this study, a first attempt is taken to show the feasibility of pre-heating the top surface with the onboard laser beam to overcome the mentioned issues. A single layer of a group of three parts built from IN718 to a height of 33.5 mm is pre-heated in a commercially available PBF-LB/M machine to an average steady state surface temperature of 200 °C using the onboard laser beam. The parts are continuously heated, omitting powder deposition and melting step. Temperatures are measured by thermocouples underneath the surface. The experiments are supported by a thermal finite element (FE) model that predicts the temperature field in the parts. When heating the parts uniformly with the laser beam, differences in surface temperatures as large as 170 K are observed. To overcome this inhomogeneity, the heat flux supplied by the laser beam is modulated. An optimized, spatial heat flow distribution is provided by the thermal FE model and translated into a scan pattern that reproduces the optimized heat distribution on the PBF-LB/M machine by locally modulating hatch distance and scan velocity. This successfully reduces the differences in surface temperature to 20 K. Thermographic imaging shows that a homogeneous surface temperature can be achieved despite the localized heat input by the beam. The potential for industrial application of the optimized laser-heating technique is discussed.

Solute-induced grain refinement and defect suppression in boron-modified molybdenum manufactured via laser powder-bed fusion

Molybdenum manufactured with laser powder bed fusion (LPBF) has an undesirable coarse-grained, columnar microstructure interspersed with intergranular cracks, high porosity, and poor mechanical strength. These defects result from a combination of the harsh LPBF process conditions and the disadvantageous properties of molybdenum, such as its high brittle-ductile transition temperature and low tolerance for oxygen impurities. In order to suppress these defect-forming mechanisms and improve the suitability for LPBF, alloy-side material adjustments with simultaneous process optimization are necessary. In this work, the effect of adjusting Mo by adding 3.5 at.% B is investigated experimentally.Mo-3.5 at.% B specimens can be produced entirely free of cracks, with a density of 99.8%. The specimens have a microstructure of fine, equiaxed grains with an average grain size of 31 μm and an aspect ratio of 1.3, thus achieving substantial refinement of the otherwise typically coarse-grained columnar, anisotropic microstructure of pure Mo in LPBF. Furthermore, the grains possess a honeycomb-like cellular subgrain structure. This structure is formed through the solute rejection effect of B during the solidification and consists of initially solidified pure α-Mo cells with a cell size <1 μm and a honeycomb-like network of an ∼100 nm thick intercellular Mo2B phase completely covering the α-Mo cells. In addition, the formation of boron oxide inclusions, presumably B2O3, with a size of <50 nm within the Mo2B phase, provides an effective mechanism for scavenging oxygen impurities, thus ensuring segregation-free grain boundaries in Mo-3.5 at.% B.The microstructural modifications substantially improve the mechanical properties. Under appropriate process conditions, with the substrate plate preheating temperature playing a crucial role, a bending strength of 1120 ± 172 MPa and a hardness of 379 ± 24 HV10 at room temperature can be achieved. At a test temperature of 600 °C, an increase in the bending strength to 2265 MPa is observed, and the bending angle simultaneously increases from 2° at room temperature to 35° at 600 °C. These findings indicate that the strength of Mo-3.5 at.% B is limited by the brittle behavior of the material at lower temperatures, at which residual defects are likely to initiate fracture.

Electrodeposition of Ti in Molten Alkali Metal Fluoride–Chloride Mixtures: Comparative Study of Li, Na, K, and Cs Systems

1. IntroductionTitanium (Ti) is a metal with excellent properties such as high corrosion resistance and biocompatibility. However, it is still not widely used due to its high production cost and poor workability. If Ti films can be plated on a variety of substrates, the excellent surface properties of Ti can be imparted, and it is expected to be applied in a wider range of fields.We have previously studied Ti electrodeposition using KF–KCl [1-3] and LiF–LiCl [4,5] melts and reported that smooth Ti films were obtained. Here, fluoride–chloride melts containing a single cation, such as KF–KCl and LiF–LiCl, were used so that differences due to cations could be compared. As a result, we have already reported that the electrodeposition potential of Ti differs significantly between the K- and Li-based systems [4]. Therefore, in this study, we investigated the electrodeposition of Ti and the electrochemical behavior of Ti(III) ions in the CsF-CsCl and NaF-NaCl melts. This allowed us to systematically compare the effects of cations on titanium electrodeposition for the Li-, Na-, K-, and Cs-based systems.2. ExperimentalThe experiments were conducted in eutectic CsF–CsCl and NaF–NaCl melts in an Ar glove box. A2TiF6 (A = Cs, Na) and sponge Ti were added to the melts and Ti(IV) ions were converted to Ti(III) ions by comproportionation reaction. Ni plate, Mo and Au flag electrodes were used as the working electrodes. The counter and reference electrodes were Ti rods. The potential of the reference electrode was calibrated by A+/A (A = Cs, Na) potential measured at a Mo electrode. The electrochemical behavior of Ti(III) was studied by cyclic voltammetry. Samples prepared by galvanostatic electrolysis of Ni plate substrates were analyzed by X-ray diffraction (XRD) after washing with distilled water.3. Result and DiscussionFigure 1 (a) shows cyclic voltammograms measured at a Mo flag electrode in the negative potential region in molten CsF–CsCl at 823 K. After the addition of Ti(III) ions, cathodic currents around 0.3 V were larger than those before the addition, and a current shoulder was observed at 0.3 V. Furthermore, a sample prepared by galvanostatic electrolysis at a cathodic current density of 25 mA cm−2 was confirmed to be Ti metal by XRD. Considering that the potential during the electrodeposition was around 0.3 V, the cathodic currents around 0.3 V in the CV were confirmed to beTi(III) + 3e− → Ti(0).Figure 1 (b) shows cyclic voltammograms measured at a Au flag electrode in the positive potential region in molten CsF–CsCl containing Ti(III) ions at 823 K. A pair of redox currents were observed around 1.7 V. The number of electrons transferred was 0.86 which was calculated from the difference in the cathodic and anodic peak potentials. This result indicates that the redox reaction around 1.7 V isTi(IV) + e− ⇄ Ti(III).Here, the formal potential of Ti(IV)/Ti(III) was calculated to be 1.63 V from the average values of the cathodic and anodic peak potentials.We compared the obtained potentials of Ti(III)/Ti(0) and Ti(IV)/Ti(III) to those previously reported in KF–KCl and LiF–LiCl melts [2,4]. Figure 2 shows the comparison of the Ti(III)/Ti(0) and Ti(IV)/Ti(III) potentials in CsF–CsCl, KF–KCl, and LiF–LiCl melts. All potentials were calibrated using F2/F− potential for comparison because Ti(III) ions exist as fluoro-complexes in the melts. Both Ti(III)/Ti(0) and Ti(IV)/Ti(III) potentials were negative in the order of Li-, K-, Cs-based systems. Such potential differences are explained by the interactions of alkaline cations (A+) and fluoride ions (F−); smaller cations interact more strongly with F−, resulting in reduced stability of Ti fluoro-complexes. At the meeting, we will compare and discuss all the results, including those obtained with NaF-NaCl melts.AcknowledgmentA part of this work was supported by JSPS KAKENHI Grant Number 22K14507. A part of this study was conducted as a collaboration with Sumitomo Electric Industries, Ltd.

Characteristics of band gaps of a metamaterial plate with membrane-type resonators based on the energy approach

Local resonance metamaterials have garnered substantial interest in recent years due to their potential to effectively control low-frequency noise and vibration. This study proposes a new metamaterial plate with double mass membrane-type resonators (DMMRs). Combining polynomial fitting and virtual spring method, the natural characteristics of the resonator and the dispersion surfaces of the metamaterial plate are obtained. Results show the proposed metamaterial plate exhibits multiple band gaps, resulting from the cancellation of shear forces in the plate by the reaction forces generated by the first two resonances of the resonators. Parametric analysis is performed to obtain the variation patterns of the band gaps, where approximate models of the resonator are adopted to explain the effects of the parameters. It is found that the occurrence and width of the two band gaps are closely related to the mass ratio between the masses on the resonator and the substrate plate. Furthermore, finite element analysis is conducted to verify the effectiveness of the theoretical derivation, as well as the suppression effect of the metamaterial plate. The findings demonstrate the advantages of the metamaterial plate in vibration control and band gap tuning. The study provides guidance for the design and analysis of elastic wave metamaterials.

Wettability and Surface Tension of Imidazolium, Ammonium, and Phosphonium Bis(fluorosulfonyl)amide Ionic Liquids: Comparison between Pentyl, Ethoxyethyl, and Ethylthioethyl Groups.

This study particularly compares the surface tensions and contact angles for molten bis(fluorosulfonyl)amide salts of imidazolium, ammonium, and phosphonium cations with the pentyl, ethoxyethyl, or ethylthioethyl group. The examined substrate plates for contact angle measurements include silicate glass, platinum, copper, graphene, and polytetrafluoroethylene (PTFE). In addition, quantum chemistry calculations were performed to obtain the optimized structures of the cations and anions of the ionic liquids (ILs) that were studied here along with some typical anions and their dipole moments, mean polarizabilities, and charge distributions. All ILs showed the same order of contact angles with respect to the substrates: PTFE > graphene ≈ copper ≈ platinum > silicate glass. By comparing the three functional groups, i.e., pentyl, ethoxyethyl, and ethylthioethyl, the ILs with the ethylthioethyl group featured a higher work of adhesion than the respective ILs with the pentyl or ethoxyethyl group. The values of the surface tensions of the ILs followed the same trend for the three functional groups. Based on the Fowkes theory, it was found that the larger surface tensions of the ILs with the ethylthioethyl group compared with pentyl and ethoxyethyl groups were because of the increase in both dispersive and nondispersive components. The quantum chemistry calculations of the ions showed a larger dipole moment and mean polarizability for the cations with the ethylthioethyl group as compared with the pentyl and ethoxyethyl groups. This is consistent with the analysis results of the surface tensions based on the Fowkes theory. By comparing other anions, the dispersive component of the surface tension of the ILs with bis(fluorosulfonyl)amide was large, which is attributed to the small dipole moment of the anion.

Distortion Analysis Method for Wire Arc Additive Manufacturing Component Using Thermomechanical Computation with Enhanced Separation and Deposition Algorithm.

This research is devoted to numerical and experimental analysis on deformation of completely removed component induced by wire arc additive manufacturing (WAAM). The component has the form of a hollow and rectangular thin wall made of deposition layer of stainless steel SS316L on top of substrate plate of mild steel S235. In this research, thermomechanical finite element analysis was applied with Goldak's double ellipsoid as heat-source model and isotropic hardening rule based on von-Mises yield criterion. A specialized numerical simulation software Simufact.Welding 2021 (SW) was utilized in developing the numerical model and the simulation of process enhanced with separation and deposition algorithm to predict the component deformation after removal of substrate. On determining the best possible mesh size, a sensitivity analysis was conducted before the advanced stage of model development. An advanced material modeling, the data of which were obtained based on the chemical composition of the evolved SS316L sample, was developed using an advanced material modeling software JMATPRO. For verification purpose, a series of WAAM experiments using robotic GMAW with synergic power source were conducted followed by the removal of substrate from component using machining process. Furthermore, component distortion was measured using industrial noncontact 3D scanner with structured blue light to fully capture the upper section deformation and compared with result of numerical computation. It can be concluded that this novel distortion analysis method using thermomechanical numerical computation with evolved material property and modified algorithms for substrate removal exhibits a surface deviation in vertical direction between 0.05 and 2.16 mm with acceptable pointwise and average error percentage of up to 3%.

Broadband RCS Reduction Using Circular Sector Structure

In this paper, a new metasurface structure is designed to reduce radar cross section (RCS). In order to reduce the radar cross section (RCS), a new metasurface structure is designed. The unit adopts the polarization conversion metasurface structure, which is composed of asymmetric double arrow-shaped metal structure and etched on the dielectric substrate on the back of the metal plate. This polarization conversion metasurface (PCM) unit consists of asymmetric double arrow-shaped metal structure, and it is etched on a dielectric substrate backed with metallic plate. It can realize converting linear polarized waves to orthogonal ones in a broadband from 18.1 GHz to 32.7 GHz efficiently. According to the further development of the triangle chessboard layout, we also designed several new circular fan-shaped configurations, which realize RCS reduction in a wider -10 dB bandwidth compared with the triangle chessboard configuration. Finally, an optimized 8-lobed circular sector configuration composed of the designed PCM unit is selected for processing and testing. It can realize the RCS reduction greater than 10 dB in a wide bandwidth ranging from 13.7 GHz to 27.5 GHz, compared with the equal-sized metallic-backed dielectric substrate plate. The experimental results basically agree with the simulation ones. The proposed broadband circular sector structure has broad application prospects such as phased array antenna technology, electromagnetic stealth technology, and electromagnetic absorption technology.

Trajectory optimization for arbitrary layered geometries in wire-arc additive manufacturing

AbstractIn wire-arc additive manufacturing, a wire is molten by an electrical or laser arc and deposited droplet-by-droplet to construct the desired workpiece, given as a set of two-dimensional layers. The weld source can move freely over a substrate plate, processing each layer, but there is also the possibility of moving without welding. A primary reason for stress inside the material is the large thermal gradient caused by the weld source, resulting in lower product quality. Thus, it is desirable to control the temperature of the workpiece during the process. One way of its optimization is the trajectory of the weld source. We consider the problem of finding a trajectory of the moving weld source for a single layer of an arbitrary workpiece that maximizes the quality of the part and derive a novel mixed-integer PDE-constrained model, including the calculation of a detailed temperature distribution measuring the overall quality. The resulting optimization problem is linearized and solved using the state-of-the-art numerical solver IBM CPLEX. Its performance is examined by several computational studies.

Influence of durability of waterproofing solutions terraces protecting against water and moisture

The article analyses the changes in the durability of waterproofing of terraces, with particular emphasis on the properties of waterproofing materials as a result of utility factors. It was analysed the influence of tensile properties of the above-mentioned materials on their resistance against fatigue resulting from movements of the substrates caused by temperature changes on the surface of the terraces coverings. The adopted range of horizontal plate movements was from 0 to 2 mm at variable temperatures: – 15°C and +70°C. The durability of waterproofing sheets, such as reinforced bitumen sheets and PVC sheets and rubber sheets, as well as coating products was assessed. Thermal deformations of the substrate plates occurring within the terrace covering are most effectively transferred by flexibility sheets with a high relative elongation value, that is: bitumen sheets with polyester reinforcement, PVC sheets and EPDM sheets. The correlation between the mechanical properties of the coatings and their resistance to fatigue cannot be determined but the most favourable properties are shown by two-component (polymer-cement) liquid applied water impermeable products reinforced on the entire surface or reinforced with special tapes over the thermal expansion joints of the substrate plates.

Reversible bonding of microfluidics: Review and applications.

With the development of microfluidic technology, new materials and fabrication methods have been constantly invented in the field of microfluidics. Bonding is one of the key steps for the fabrication of enclosed-channel microfluidic chips, which have been extensively explored by researchers globally. The main purpose of bonding is to seal/enclose fabricated microchannels for subsequent fluid manipulations. Conventional bonding methods are usually irreversible, and the forced detachment of the substrate and cover plate may lead to structural damage to the chip. Some of the current microfluidic applications require reversible bonding to reuse the chip or retrieve the contents inside the chip. Therefore, it is essential to develop reversible bonding methods to meet the requirements of various applications. This review introduces the most recent developments in reversible bonding methods in microfluidics and their corresponding applications. Finally, the perspective and outlook of reversible bonding technology were discussed in this review.

Stability and Bifurcation Analysis of Two-Immiscible Liquids Film Down an Inclined Slippery Solid Substrate

In this work, the dynamic behavior of linear and nonlinear waves propagating at the separating surface between two thin layers of viscous Newtonian fluids is studied in the presence of the effect of insoluble surface surfactant. The two liquids are confined between two infinite rigid parallel plates and assumed to have different densities and viscosities. The equations of evolution for surface-wave elevation and concentration of surfactant are derived using the lubrication approximation. In the linear stage, by utilizing the normal mode approach, we have derived the dispersion relation that relates the wave angular frequency to the wave number and other parameters that is solved numerically to inspect the influences of some selected parameters on the stability criteria of the fluid flow. Also, analytical expressions for the growth rate as well as its maximum value with corresponding wave number are obtained in the special case of long-wave limiting. It is concluded that the Marangoni number text {Ma} has acquired a significant stabilizing influence on the fluid flow, whereas the inverse of the slippery length of substrate plate beta, resorts to the destabilize the motion of the interfacial waves. Consequently, both of the Marangoni number and the substrate slippy coefficient can be utilized to control the film flow regime, where they preserve the film laminar flow and tend to prevent the film breakdown. These can be useful in many industrial applications such as coating processes, heat exchangers, cooling microelectronic devices, chemical reactors, food processing, thermal protection design of combustion chambers in rocket engines and operation of Laser cutting and heavy casting production processes.

Bio-Inspired Circular-Polarized UHF RFID Tag Design Using Characteristic Mode Analysis

This paper presents a bio-inspired circularly polarized ultra-high frequency (UHF) radio frequency identification (RFID) tag antenna for metallic and low-permittivity substances. This tag design is based on a leaf-shaped radiator, two shorting stubs and slots etched on F4B substrate. Initially, the tag antenna is designed using characteristics mode analysis (CMA) by analyzing the first six CM modes and characteristic angles. The width of orthogonal slots is varied to get the resonance of CM modes in the required US RFID band. Moreover, the edges are blended to get orthogonal current distribution, which is necessary for circular polarization. Additionally, the proposed tag design is optimized further using CST Microwave studio and an RFID chip is exploited as a capacitive coupling element (CCE) to run CM modes with the orthogonal current pattern. This tag can also be tunable to European RFID (EU) band (866 – 868 MHz) by changing the length of shorter diagonal slot. The tag design offers a read range of 7 m and 4.5 m on 100 × 100 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> metals plate and low-permittivity substrates, respectively (for 902 – 928 MHz band). In EU band, the corresponding read ranges are 5.7 m and 3.5 m above metal and low-permittivity objects, respectively. This circularly polarized tag antenna is advantageous in terms of cost, circular polarization feature, and ease of fabrication due to the absence of vias, shorting pins, and matching circuits. Therefore, this tag design is suitable for labeling various low-permittivity objects, industrial conveyer belt applications, baggage handling systems, and IoT applications.

An Investigation into Heat Transfer Enhancement by Using Oscillating Fins

The present work describes numerical and experimental investigation of the heat transfer characteristics in a plate-fin, having built-in piezoelectric actuator mounted on the base plate (substrate). The geometrical configuration considered in the present work is representative of a single element of the plate-fin and triple fins. Air is taken as the working fluid. A performance data for a single rectangular fin and triple fins are provided for different frequency levels (5, 30 and50HZ) , different input power (5,10,20,30,40 and 50W) and different inlet velocity (0.5, 1, 2, 3, 4, 5 and 6m/s) for the single rectangular fin and triple fins with and without oscillation. The investigation was also performed with different geometrical fin heights ( 50mm and 35mm) and distance between the fins (3mm and 6mm). It is observed that the heat transfer increases with the increase in the frequency and Reynolds number. It is further observed that triple fins with (height=50mm and distance between the fins=3mm) gives better enhancement as compared to othercases, The study shows that the piezoelectric actuator when mounted on the rectangular fins gives great promise for enhancing the heat transfer rate

Thermoplastic-based microfluidic chip bonding with PES hot melt adhesive film

ABSTRACT In this study, a low-cost and rapid bonding method for thermoplastic-based microfluidic devices is introduced. The thermoplastic substrate and cover plate were directly bonded with PES copolyester hot melt adhesive film. Compared with conventional bonding methods for thermoplastic chips, e.g. thermal fusion and chemical-assisted bonding, the proposed bonding process can be finished within minutes without sophisticated instruments or volatile chemical solvents. Several microfluidic devices were also fabricated and tested, the measured bonding strength is comparable to the conventional thermal fusion bonding method. The biocompatibility of the proposed bonding method was also evaluated by culturing bacteria in the PES adhesive covered culture dish. The proposed bonding method for thermoplastic-based microfluidic is especially suitable for the massive fabrication of POCT devices with advantages in processing speed, instrument requirement, cost, and bonding strength.

Smart hybrid composite sensor technology to enhance the detection of low energy impact damage in composite structures

This paper introduces novel structural health monitoring (SHM) sensors to improve the detection of low energy impact damage in laminated composites. The sensor is a purposely designed thin-ply hybrid composite, composed of a layer of unidirectional S-glass/epoxy and another layer of unidirectional ultra-high modulus (UHM) carbon/epoxy. The sensor was incorporated onto both the impacted face and back of a substrate plate made from unidirectional T800 carbon/MTM49-3 epoxy prepregs with the stacking sequence of [45/0/90/-45]4S. A series of drop tower tests were conducted on the composite plates with and without the attached hybrid sensing layer, with two different in-plane dimensions and varying energy levels ranging from 3 J to 124 J. The results indicate that the sensors functioned satisfactorily and provided direct correlations between visible and internal hidden damage detected by C-scan. The sensor can be optimized by selecting appropriate material properties and adjusting it to the in-plane dimensions of the substrate.

A potential-responsive ion-pump system based on nickel hexacyanoferrate film for selective extraction of cesium ions

A nickel hexacyanoferrate (NiHCF) film electrode was prepared with NiHCF, conductive carbon black, and polyvinylidene difluoride, which was coated on graphite plate substrate for selective extraction of Cs+ ions by using electrochemically switched ion exchange (ESIX) technology. A potential-responsive ion-pump system for efficient extraction of Cs+ ions was designed, and the effect of wet film thicknesses, charging modes, flow rates, and chamber widths on Cs+ ions extraction performance was investigated. In the system, the adsorption capacity and removal percentage of Cs+ ions on the NiHCF film electrode reached as high as 147.69 mg·g−1 and 92.47%, respectively. Furthermore, the NiHCF film electrode showed high selectivity for Cs+ ions and stability. After seven cycles of adsorption/desorption, the desorption percentage could reach about 100%. The excellent Cs+ extraction performance should be attributed to the strong driving force produced by the potential-responsive ion-pumping effect in the ESIX process, as well as the low ion transfer resistance of the film electrode which is caused by the special crystal structure of NiHCF. In addition, the NiHCF film electrode was implemented to work together with the bismuth oxybromide (BiOBr) film electrode to accomplish the simultaneous extraction of Cs+ and Br–. And the adsorption capacity and removal percentage of Br– ions on the BiOBr film electrode reached 69.53 mg·g−1 and 77.32%, correspondingly. It is expected that such a potential-responsive ion-pump system based on NiHCF and BiOBr film electrodes could be used for the selective extraction and concentration of Cs+ and Br– ions from salt lake brine..

Influences of a Variety of Reinforcements on the Durability of Reinforced Bitumen Sheets Operating at Variable Temperatures

This manuscript provides an overview of the most commonly-produced bitumen roofing sheets, focusing on the types of reinforcements used for their production and the reinforcements’ effects on the durability of tensile mechanical properties of roofing sheets under thermal loads. The paper includes the analysis of working conditions of roof coverings in the mid-European transitional climate, i.e., exposed to temperatures passing through 0 °C for three seasons in a year, periodic exposure to negative temperatures reaching −15 °C and positive temperatures up to +70 °C, justifying the above-mentioned emphasis on thermal load. It draws attention to technical problems related to the cooperation of roofing sheets with roofing substrates, with particular emphasis on concrete substrates. For the purposes of the work, the analyses were carried out with regard to the assessment of the service life of roof coverings made of various reinforcements working in conditions of variable temperatures and thus exposed to the transfer of thermal movements of substrate plates. The analyses also included the impact of different coefficients of thermal expansion of the materials in contact with other materials within roof coverings on the incidence of damage to cover layers. Particular attention was paid to the conditions resulting from the production process of roofing sheets effect on the durability of roof coverings made of these materials. Additionally, there were set directions for further work to calculate the impact of stresses, arising in layers of roof coverings during their operation in changeable negative and positive temperatures, on the incidence of mechanical damage to these coverings.