Increasing Substrate Thickness Research Articles

Screen-printing high/low resistance using only a single silver nanowire ink: Resistance-gradient metasurface application for broadband microwave absorption and optical transparency

Transparent metasurface absorbers are highly sought after for their diverse applications, but achieving broad absorption bandwidths without sacrificing optical transparency remains a challenge. Traditionally, enhancing absorption involves increasing substrate thickness, which reduces transmittance. We address this by introducing a resistance-gradient metasurface (RGM) that combines broad absorption with high optical transparency. Unlike conventional methods requiring various inks for different resistances, our approach uses a single silver nanowire ink and screen-printing to create multiple resistances. This technique allows for flexible design and multiple resonances within the metasurface, achieving broad absorption even with a thin substrate. The RGM demonstrates an absorption bandwidth from 8.68 to 11.48 GHz with a substrate thickness of just 0.045 λ0, and optical transmittance of 66.3 % at 550 nm. This innovation promises to enhance both substrate efficiency and bandwidth in transparent metasurface absorbers, broadening their application potential in advanced devices.

Fracture energy and cohesive law analysis of adhesives using a recently developed SCB joint: The influence of joint geometry and mode mixity

In a prior study, the current authors proposed the utilization of semi-circular bend (SCB) specimens for analyzing the fracture energy of adhesive materials. However, similar to standard fracture test specimens, the geometry and size of the joint can impact the measured fracture energy when using SCB samples. Therefore, the objective of this research is to investigate the influence of adhesive layer thickness, substrate thickness, and disk radius of SCB specimens on cohesive law parameters and fracture energy of the adhesive. The study examines the fracture energy under different loading conditions, including pure mode I, pure mode II, and two mixed-mode conditions. By employing an inverse data reduction method, the cohesive law parameters of the tested adhesive are determined for various joint geometries. The results demonstrate that the disk radius does not affect the cohesive law of the joint. Furthermore, it is observed that bondline thicknesses of 0.2 mm and 0.4 mm lead to similar cohesive laws, whereas an adhesive thickness of 1 mm results in lower initial stiffness but higher fracture energy and damage initiation traction. Moreover, the study reveals that an increase in substrate thickness reduces the final fracture separation, indicating a more brittle fracture behavior. This can be attributed to a smaller fracture process zone caused by the plane strain load distribution in the adhesive layer.

CNR performance of semiconductor materials for X-ray imaging of breast calcifications

We present the results of a GAMOS/GEANT4 computer simulation of a standard X-ray mammography system, which consists of a Tungsten 28 kVp polychromatic X-ray source with a 50 μm Rh filter, a mammography phantom with Al2O3 spherical specks of different diameters, and a generic pixel detector (55 μm × 55 μm pixel size) with different types of semiconductor sensors. The number of photons simulated is calibrated to produce similar entrance surface dose (ESD) as the one used by a standard clinical mammography screening. Estimates of Contrast to Noise Ratio (CNR) as a function of ESD, sensor thickness and microcalcification diameter are presented for four different sensor materials: Silicon (Si), Cadmium Telluride (CdTe), Gallium Arsenide (GaAs) and Perovskite (MAPbI3). For the X-ray energy spectrum and pixel size considered, and an ESD dose of 4 mGy, our study shows that, with the exception of Si, these sensors, as thin as 200 μm, are able to resolve (with at least 3 standard deviations above background) Al2O3 spherical specks up to a minimum diameter of 180 μm, having statistically compatible CNR performance. The increase in substrate thickness has a substantial improvement in the CNR values provided by the Si sensor, while for the other cases the enhancement of CNR is marginal and consistent with statistical uncertainties with the thinnest case considered.

Study on the Adsorption Deformation of a Substrate via Spin Coating Based on the 3D-DIC Method and Its Effect on the Homogeneity of Perovskite Films.

The physical and chemical stability of perovskite films has always been a key issue for their industrialization, which has been extensively studied in terms of materials, environment, and encapsulation. Spin coating is one of the most commonly used methods for the preparation of perovskite films in research. However, little attention has been paid to the deformation state of the substrate when it is fixed by means of adsorption and its impact. In this work, the three-dimensional digital image correlation (3D-DIC) method and hyperspectral technology are used to acquire and analyze the adsorption deformation characteristics of the substrate during spin coating, as well as the resulting inhomogeneity. Plastic and four different thicknesses of float glass (0.2, 0.5, 0.7, 1.1 mm) were selected as substrates, and they were tested separately on two suction cups with different structures. The results show that the plastic and 0.2 mm specimens exhibit obvious strain localization behavior. The distribution and magnitude of the strain are affected by the size of the sucker structure, especially the width of the groove. For glass specimens, this effect shows a nonlinear decrease with increasing substrate thickness. Compared to the strain value, the irregularity of local deformation has a greater impact on the non-uniform distribution of materials. Finally, inhomogeneities in the perovskite films were observed through optical lens and hyperspectral data. Obviously, the deformation of the substrate caused by adsorption should attract the attention of researchers, especially for flexible or rigid substrates with low thickness. This may affect the centrifugal diffusion path of the precursor, causing microstructure inhomogeneity and residual stress, etc.

Экспериментально-аналитические исследования пожарной опасности материалов, применяемых в оборудовании с обогащенными кислородом средамипри повышенных давлениях, и пути снижения их горючести

Introductio n. Sealed equipment (hereinafter referred to as hermetic chambers) is used in various branches of economy. Atmospheres enriched with oxygen (in some cases under variable pressure conditions) are used. It was shown that the main reason of the fires in the pressurized chambers was the unregulated use of the electrical equipment, as well as combustible substances and materials on the basis of organic compounds included in the materials used in the pressurized chambers. Objective. To find ways to decrease combustibility of materials used in pressurized chambers and to study fire risk parameters of pressurized chambers with high oxygen content and increased pressure. Obje ctives. To determine the boundary conditions of applying materials with increased values of temperature, oxygen content and pressure and analyze the results of experimental studies of combustibility of materials used in sealed chambers. Research met hods. Investigation of the characteristics of the combustion process of non-metallic materials under increased pressure was carried out on an original setup represented by a stainless steel vessel with a height of 750 mm and an inner diameter of 155 mm. A spiral of nichrome wire was used to ignite the sample. The pressure was fixed with a manometer. Results and th eir discussion. As a result of experimental research of fire hazard of construction and construction materials in oxygen-enriched media and under increased pressure the ways of increasing the oxygen concentration limit (OCL) and reduction of combustibility of materials were determined: application of heat-removing surface, incombustible shell; putting inhibitors in their composition and structure; surface treatment with different fire protective compositions and impregnations. When studying the parameters of fire hazard (flame propagation velocity, heat of combustion, autoignition temperature) of materials under the conditions of changes in the composition of nitrogen-oxygen atmosphere and pressure, it was found that the OCL for all materials decreases at higher pressures. Conc lusions. It is found that the limiting oxygen concentration depends on the geometrical dimensions of the sample, as well as on the speed of the gas flow. At higher pressures the OCL for all the materials decreases. The presence of a heat-removing surface also leads to higher OCL, which increases with increasing substrate thickness and decreasing thickness of the material on it. For materials not containing substances that inhibit the combustion reaction, a decrease in the LOC value with an increase in the number of hydrogen atoms in the polymer macromolecule is characteristic.

Experimental Study on the Influence of Substrate Properties on Rainfall Infiltration and Runoff from Ecological Slopes

Rain is an important factor influencing the instability of ecological slopes. There is little research on the inherent quantitative influence of substrate properties on slope runoff and water infiltration to support accurate ecological slope protection design. In this paper, the influence of substrate characteristics on slope runoff and water infiltration is quantitatively analyzed by constructing large physical models with different substrate characteristics for artificial rainfall simulations. The experimental results showed that the cumulative runoff volume and slope runoff rate were positively correlated with the cement content and substrate thickness in a 4 h, 60 mm/h artificially simulated rainfall. Specifically, the cumulative runoff volume increased by 2.06% for every 1% increase in cement content, and the cumulative runoff volume increased by 3.93% for every 1 cm increase in substrate thickness. The substrate inhibited the advance of the wetting front, and at different slope locations, the transport rate of the wetting front exhibited a mid-slope > upslope. Moreover, the transport rate of the wetting front showed a non-linear relationship with time as a power function V = a·tb, with the cement content showing a linear relationship with parameters a and b, and the substrate thickness showing a non-linear relationship with parameters a and b. The cumulative infiltration and infiltration rate were negatively correlated with cement content and substrate thickness, as shown by a 2.2% decrease in cumulative infiltration for every 1% increase in cement content and a 4.73% decrease in cumulative infiltration for every 1 cm increase in substrate thickness.

Investigating the effect of gravity on the optical performance of large-sized liquid crystal displays

This paper proposes a method to investigate the effect of gravity on optical performance of large-sized liquid crystal displays (LCDs). Combined with the finite element analysis and the LCD optical simulation, the change in optical performance of large-sized LCDs under the influence of gravity is analyzed. Compared with the condition without tilt angle, the Δu'v' is 0.025 in the bottom area of the 100-in LCD with the substrate thickness of 0.3 mm at a tilt angle of 1.5°, leading to a noticeable color shift. With the decrease of tilt angle or the increase of substrate thickness, the change in optical performance becomes unnoticeable and thus avoids the occurrence of visible display defect. Utilizing the proposed method, the assembly precision of large-sized LC panels can be calculated and the display defect caused by gravity can be effectively prevented.

Performance evaluation and design of 5G communication-based millimeter wave antenna

Multiple categories of electronic devices have been introduced recently in response to the demands and developments in the industry. Around 5.19 billion telecom services subscribers today have a significant effect on the allocation and utilization of bandwidth, and hence, there is extensive need to use higher-frequency bands, e.g., mm band to achieve the required quality of service since there is extensive need to shift the paradigm to the next generation. For 5G networks, antenna structuring and designing is an integral part of the communication system. In antenna theory, improving antenna gain is important to attain isotropic antenna, antenna gain can be improved by the controlled behavior of frequencies, beam forming and choosing the right antenna fabric. Through antenna design using different substrates thickness, the propagation losses are examined in order to determine the variation with radiation characteristics. In this way, the examination of the 5G mm-wave spectrum with comparative analysis of input impedance, gain and radiation efficiency is shown through mathematical modeling. Using this approach, the antenna efficiency is improved by up to 20% with increase in substrate thickness. Different antenna arrays have been designed for effective improvement in reflection coefficients. The results are obtained using simulation of antenna in CST and high-frequency structure simulator.

Simulation and Experimental Study of Terahertz Wave Transmission Characteristics Based on Periodic Metal Open Resonant Ring Structures

Different open resonant ring structures with substrate of polyimide were designed. The transmission characteristics of the structures for terahertz wave were investigated by simulation and experiment. The results show that the transmission peak of the structures moves to high frequency with increase of thickness of the metal layer. With increase of substrate thickness, the transmission peak moved to low frequency and the transmissivity decreased. The influence of number of “C” shape open resonant rings in the unit structure on the transmission characteristics of terahertz wave was also studied. It is found that when the number of “C” shape open resonant rings increases from one to two, more transmission peaks appeared in the frequency of 0.2–2 THz. The transmissivity of the designed structures was tested by terahertz time-domain spectrometer (THz-TDS). The experimental results showed good agreement to the simulation results.

Meshless analysis of substrate stiffness and its effect on metallic double-L joint strength and stress distributions

Aircraft, automotive, and wind turbine blade construction often require bonding of non-parallel substrates. T-joints are used for such purpose. However, reduced information about their mechanical behaviour is available in the literature, mostly reported with similar substrate thickness. When bonding a thin substrate on a thicker one, the thinner substrate could largely deform before the adhesive layer fails. Therefore, numerical techniques as the meshless methods (MM) are suitable to analyse this joint configuration. In this work, a MM was used to analyse T-joints with metallic substrates. The analyses were elastic-plastic and considered the Exponent Drucker-Prager (EDP), which is appropriate for ductile adhesives. Four substrate thicknesses (1–4 mm), and three different adhesive systems were considered, aiming to investigate the EDP suitability for the analysis of adhesive joints with non-parallel substrates and how substrate thickness and adhesive ductility influence joint strength (Pmax). Thus, Pmax, stress and strains along the bond-line, and plastic hinges in the substrates were evaluated. Regardless of the adhesive system, the increase of substrate thickness (tP2) also increased Pmax. For adhesives with failure strain (ϵf) below 10%, experimental and numerical results have a good agreement, showing that the proposed methodology is suitable to analyse this joint type.

Second law analysis of recharging microchannel using entropy generation minimization method

This work deals with numerical study of entropy generation in recharging and simple microchannel to explore effect of geometrical modification on thermodynamic irreversibility in a system. This work also investigates effects of geometrical and thermo-physical parameters on entropy generation in recharging microchannel system, by varying number of small channels, substrate thickness, channel wall width, channel aspect ratio, substrate material, and applied heat flux. Numerical simulations are carried out by considering water as working fluid with Reynolds number 100-500. Results reveal that recharging microchannel shows maximum 47% reduction in total entropy generation compared to simple microchannel, which indicates that thermodynamic irreversibility is lower in recharging microchannel compared to simple microchannel. Thermal entropy generation in recharging microchannel decreases with increasing number of small channels, channel aspect ratio, and substrate material thermal conductivity, whereas it increases with increasing substrate thickness, channel wall width, and applied heat flux. Moreover, frictional entropy generation in recharging microchannel is invariant with substrate thickness, channel wall width, substrate material, and applied heat flux. These parametric investigations indicate that consideration of entropy generation in microchannel solid substrate during entropy generation analysis is quite important, as it strongly influence entropy generation in a system.

Evolution of Welding Residual Stresses within Cladding and Substrate during Electroslag Strip Cladding.

Hydrogenation reactors are important oil-refining equipment that operate in high-temperature and high-pressure hydrogen environments and are commonly composed of 2.25Cr–1Mo–0.25V steel. For a hydrogenation reactor with a plate-welding structure, the processes and effects of welding residual stress (WRS) are very complicated due to the complexity of the welding structure. These complex welding residual stress distributions affect the service life of the equipment. This study investigates the evolution of welding residual stress during weld-overlay cladding for hydrogenation reactors using the finite element method (FEM). A blind hole method is applied to verify the proposed model. Unlike the classical model, WRS distribution in a cladding/substrate system in this study was found to be divided into three regions: the cladding layer, the stress-affected layer (SAL), and the substrate in this study. The SAL is defined as region coupling affected by the stresses of the cladding layer and substrate at the same time. The evolution of residual stress in these three regions was thoroughly analyzed in three steps with respect to the plastic-strain state of the SAL. Residual stress was rapidly generated in Stage 1, reaching about −440 MPa compression stress in the SAL region at the end of this stage after 2.5 s. After cooling for 154 s, at the end of Stage 2, the WRS distribution was fundamentally shaped except for in the cladding layer. The interface between the cladding layer and substrate is the most heavily damaged region due to the severe stress gradient and drastic change in WRS during the welding process. The effects of substrate thickness and preheat temperature were evaluated. The final WRS in the cladding layer first increased with the increase in substrate thickness, and then started to decline when substrate thickness reached a large-enough value. WRS magnitudes in the substrate and SAL decreased with the increase in preheat temperature and substrate thickness. Compressive WRS in the cladding layer, on the other hand, increased with the increase in preheat temperature.

Influence of the CdZnTe Substrate Thickness on the Response of HgCdTe Detectors Under Irradiation: Modeling of the Substrate Luminescence

The most extensively used infrared (IR) detectors in astrophysics are based on mercury cadmium telluride (MCT) technology: the MCT light-sensitive layer is grown on a cadmium zinc telluride (CZT) substrate. When launched on a satellite, these detectors are subjected to ionizing radiation from cosmic rays or solar flares (mainly protons) which degrade the detector performance. Indeed, an elevation of the detector background was noted under irradiation, which is believed to be associated with the luminescence of the CZT substrate. Complete removal of the substrate eliminates the problem, but it is a challenging step in the fabrication process. A deeper understanding of the response of IR detectors under irradiation, when the substrate is fully removed, will enable the optimization of substrate design for high-performance space-based scientific imaging. Here, the first results of proton irradiation modeling in MCT detectors, including energy deposition in the CZT substrate, are presented. The estimation of image pollution relies on GEANT4 (GEometry ANd Tracking 4) Monte Carlo simulations as well as analytical and numerical calculations of carrier transport inside the detector structure. In particular, recombination processes in the CZT substrate are taken into account to model the luminescence effect induced by proton irradiation. According to this model, considering published material properties, the diffusion of the carriers generated inside the CZT substrate toward the MCT layer is the main source of pollution. As the substrate thickness increases, more pixels are impacted by a proton impact on the IR. Consequently, depending on the targeted application, either partial or complete removal may be chosen.

Effect of aluminium substrate thickness on the lap-shear strength of adhesively bonded and hybrid riveted-bonded joints

For lightweight materials, e.g. aluminium, the definition of proper joining technology relies on material properties, as well as design and manufacturing aspects. Substrate thickness is especially relevant due to its impact on the weight of components. The present work compares the performance of adhesively bonded (AJ) to hybrid riveted-bonded joints (HJ) using aluminium substrates. To assess the lightweight potential of these joining methods, the effect of substrate thickness (2 and 3 mm) on the lap-shear strength (LSS) of single lap joints is investigated. An epoxy-based structural adhesive is employed for bonding, whilst HJs are produced by lockbolt rivet insertion into fully cured adhesive joints. The stiffness of joints increased with an increase of substrate thickness. HJs presented two-staged failure process with an increase in energy absorption and displacement at break. For HJs, the substrate thickness changed the failure mechanism of rivets: with thicker substrates failure occurred due to shear, whereas in thinner substrates due to rivet pulling-through. The LSS of 2 mm and 3 mm-thick AJs is similar. With 2 mm-thick substrates, the LSS of HJs was lower than AJs. In contrast, the highest LSS is obtained by the 3 mm-thick HJs. The highest lightweight potential, i.e. LSS divided by weight, is achieved by the 2 mm-thick AJs, followed by the 3 mm-thick HJs with a loss of ca. 10% of specific LSS.

Design of a microstrip metamaterial for C-band Radar absorber

Electromagnetic wave absorber has an important role in radar technology used for military as well as for civilian application. There are many electromagnetic wave absorbing technologies used in current radar technology, one of which is an absorber based on metamaterial. In this paper, design of a microstrip metamaterial for C-band radar absorber will be discussed. The metamaterialabsorbers on theC-bandrange is designed on microstrip material having a thickness 4.8 mm and dielectric constant 2.17. There are several techniques can be implemented to broad the working frequency, which are increasing substrate thickness, decreasing dielectric constant and patch modification. In this work, the simulation method is employed for optimizing the design and achieving good electromagnetic wave absorption at the C-band working frequency. Simulated result show the microstrip metamaterial design has broadband absorption lower than -10 dB ranging from 4.3 GHz to 7.1 GHz. Based on the characteristics, this design can be realized as radar absorber at C-band frequency

Study of an Inverted Rectangular Patch Printed on Anisotropic Substrates

ABSTRACTThe resonant frequencies and bandwidths of the inverted rectangular patch over anisotropic substrates are investigated in this paper. A rigorous analysis is performed using dyadic Green’s function formulation in the vector Fourier transform domain. The Galerkin’s technic is then used in the resolution of the integral equation; the complex resonance frequencies for the TM01 mode are studied with sinusoidal basis functions. The numerical results obtained are compared with previously published numerical results computed by means of the electromagnetic simulator “IE3D software”. Good agreement is found in all cases among all sets of results. For an isotropic substrate, it is confirmed that the bandwidth decreases with increasing of air-gap layer for high permittivity and low thickness of the substrate. Also, we show that the resonant frequencies and bandwidths are highly dependent on the permittivity variations alongside the optical axis. Other theoretical results attained display that the resonant frequencies downtrend monotonically with increasing substrate thickness, the diminution being larger for the uniaxial anisotropy of the substrate. Finally, numerical results for the effects of uniaxial anisotropy in the substrate on the radiation of the inverted rectangular microstrip structure are also presented.

A High-Gain Circularly Polarized U-Slot Patch Antenna Array [Antenna Designers Notebook

Patch antennas are widely applied in modern wireless communication systems. However, conventional patch antennas have the disadvantage of narrow bandwidth and are not suitable for Ku-band satellite broadcast reception. Many researchers have proposed various techniques to enhance the bandwidth of probe-fed patch antennas, e.g., employing thick substrate [1], adding parasitic patches either in the same layer (coplanar) [2]-[3] or in another layer (stacked) [4], and using capacitor-loaded patches [5]. With the first technique, the substrate thickness increases and induces the excitation of surface waves [6]. Apart from reducing the radiation efficiency, these surface waves diffract at the substrate edges and deteriorate the radiation patterns. The presence of coplanar and stacked geometry has the disadvantage of increasing the area and thickness of the antenna, respectively. Additional capacitors cause antenna gain reduction because of the ohmic loss of the loading chip resistor.

Effect of processing conditions on the microstructure, porosity, and mechanical properties of Ti-6Al-4V repair fabricated by directed energy deposition

In this study, the effect of processing parameters in directed energy deposition (DED) additive manufacturing (AM) on the microstructure and mechanical properties of Ti-6Al-4V was evaluated. A commercial DED system was used to deposit square patches of Ti-6Al-4V onto a substrate with the same nominal composition, with varying conditions to represent those that may be found in actual repair applications. A design of experiments was used to study the effect of substrate thickness, interlayer dwell time (time between deposition of subsequent layers), initial substrate temperature, hatch pattern, and number of deposited layers on the microstructure, porosity, and hardness of the deposition. Varying these processing parameters elucidates how each independently, or all collectively, impact the resulting microstructure and properties of Ti-6Al-4V deposits. As internal pores, or defects, significantly affect the properties of additively manufactured components, this study aimed to identify and quantify those defects in DED. The results from the current study show that with decreasing substrate thickness, the depth of the heat affected zone increased by an average of 400 μm. The density of the part was affected by the number of deposited layers and the initial substrate temperature, increasing with increasing the number of deposited layers, but decreasing with higher initial substrate temperatures. Lastly, the hardness increased with increasing substrate thickness, but was not impacted significantly by the other parameters studied.

Polaron effect influenced by thicknesses of GaAs film and AlxGa1−xAs substrate

The binding energy and effective mass of a polaron confined in a GaAs film deposited on AlxGa1-xAs substrate are studied theoretically within the framework of the fractional-dimensional approach and by using a correctional length of confinement. The numerical results for the polaron binding energy and effective mass in the GaAs film deposited on AlxGa1-xAs substrate are obtained as functions of the film thickness and substrate thickness. Through the correctional length of confinement, the problem of the original fractional-dimensional approach for the jumps of the polaron binding energy and mass shift with increasing the film thickness is solved. Our calculations show that the polaron binding energy and mass shift decreases monotonously as the film thickness increases. It is also shown that the polaron binding energy and mass shift both have their maxima as the substrate thickness increases.

The Effect of A Pre-Deposited Mobile Substrate On Terminal-Fan Evolution and Channel Organization: Tank Experiments

Abstract: Depositional processes interact with mobile substrates in nearly all passive-margin settings throughout the world. The interplay between sedimentation and a mobile substrate (e.g., salt layer) results in a complex stratigraphic record, making it difficult to reconstruct basin-fill history. Herein we investigate the dynamic feedback between sediment loading and substrate deformation to understand morphologic change and stratigraphic development. We used simplified tank experiments of a linked fan and terminal-channel system evolving over a deformable substrate. A series of experiments were conducted with controlling variables including mobile substrate thickness, sediment supply rate, and basin slope. Experimental results indicate: (1) an increase in substrate thickness resulted in increased subsidence around the fan that limited sediment transport to its terminal channels, (2) a higher sediment discharge rate on a substrate resulted in faster fan progradation coupled with relatively less subsidence and more sediment transport to terminal channels, and (3) a higher-slope experiment caused the largest amount of sediment transport downstream, while a decrease in basin slope resulted in a larger number of established channels along with a wider fan surface. An analysis of surface processes is also used to determine the expected stratigraphy between a linked fan and terminal-channel system as it interacted with the mobile substrate. We apply the experimental findings to understand the fluvial-dump–wind-redistribute system deposited on top of the Louann Salt layer in the eastern part of the Late Jurassic Gulf of Mexico basin.