Aluminum Disk Research Articles

Stretchable Metamaterials with Tunable Infrared Emissivity for Dynamic Thermal Management.

Manipulation of infrared emissivity, which is closely related to surface structure and optical parameters of materials, is a crucial approach for realizing dynamic thermal management. In this study, we design a metamaterial consisting of an array of aluminum disks embedded on a surface of a stretchable elastomeric substrate. Mechanical stretching-induced deformation allows dynamic modification of the surface structure and equivalent optical parameters, thus enabling dynamic control of the emissivity. By utilizing the elastomer polydimethylsiloxane (PDMS) as the substrate, the microstructure interdisk gap can be altered by stretching the PDMS. Through theoretical calculations, the plausibility of this approach is explained by the excitation of plasmon resonance and the variation in the exposed area of highly absorbent PDMS, and the optimal structures for tuning the infrared emissivity are revealed to be 6 μm in diameter and 100 nm in height. Based on this design, we prepare samples with periods of 7 and 7.9 μm and experimentally demonstrate that a change in the period can cause a change in the emissivity and thus tunability in thermal control performance. The temperature difference between the two samples reaches 44.1 °C at a heating power of 0.28 W/cm2 for both samples. Furthermore, we construct a stretching platform that enables in situ mechanical stretching to realize dynamic changes in emissivity. The integral infrared emissivity of the sample increases from 0.32 to 0.5 at a biaxial tensile strain of 13%, achieving a 56% modulation rate of the integral infrared emissivity. The material is expected to enable dynamic thermal management.

An adjustable high‐flux LED solar simulator based on dome structure

AbstractHigh‐flux solar simulator (HFSS) commonly serves as a vital instrument for conducting material testing and thermochemical experiments, offering valuable applications in the fields of photovoltaic cells and concentrated solar energy. This paper proposes a continuously adjustable HFSS based on light‐emitting diodes (LEDs), which can be employed for experimental testing in the solar cell aging. First, an irradiation unit module has been built using high‐power LEDs and total internal reflection lenses, and the irradiation performance of the single unit has been validated. In theory, a dome layout model is proposed, in which a detailed geometric analysis is provided for the maximum number of units that can be accommodated on the dome, considering unit size and dome dimensions. Subsequently, aluminum disc has been used as thermal flux sensors, and the irradiation distribution of the system is characterized using a charge‐coupled device observation camera and Lambertian board. The results indicate that the system offers an adjustable average flux ranging from 1.6 to 9.04 kW/m2 when the system input current is in the range of 7.2–54 A. Additionally, the system demonstrates a spatial nonuniformity of 2% within a 10‐mm diameter (Φ = 10 mm) region test region and temporal instability of 2% within 30 min.

Acoustically transparent alumina-based cranial implants enhance ultrasound transmission through a combined mechano-acoustic resonant effect

Therapeutic ultrasound for brain stimulation has increased in the last years. This energy has shown promising results for treating Alzheimer’s disease, Parkinson’s disease and traumatic brain injury, among other conditions. However, the application of ultrasound in the brain should trespass a natural but highly attenuating and distorting barrier, the cranium. Implantable ceramic materials can be used to replace part of the cranium as an alternate method to enhance ultrasound transmission. In this work, it is presented the acoustic characterization of alumina ceramic disks that can be employed as cranial implants for acoustic windows-to-the-brain. Alumina samples were prepared using current-activated pressure-assisted densification and were acoustically characterized. Acoustic impedance and attenuation of the samples were determined for different porosities. Additionally, measured and modeled acoustic fields are presented and analyzed in terms of the total ultrasound transmitted through the ceramics. Results indicate a resonant behavior in the alumina disks when the thickness corresponds to a half-wavelength of ultrasound; this resonance permits a total of 95.4% of ultrasound transmission; for thicknesses out of the resonant zone, transmission is 53.0%. Alumina proves to be an excellent medium for ultrasound transmission that, in conjunction with its mechanical and optical properties, can be useful for cranium replacement in mixed opto-acoustic applications.

Droplet impact dynamics on a rotating aluminum disk: Comparative study based on liquid properties

Droplet impact dynamics on a rotating aluminum disk: Comparative study based on liquid properties

Weak magnetic vestibular stimulation decreases postural sway

BackgroundPerceptible galvanic vestibular stimulation (GVS) causes nystagmus and postural sway deterioration. Conversely, imperceptible GVS improves postural stability, suggesting the presence of stochastic resonance. Research questionSimilar to GVS, strong magnetic vestibular stimulation of 7 T induces nystagmus and increases body sway. Thus, a relatively small magnetic stimulation may improve postural stability. In this study, we measured the effect of a relatively small magnetic field on postural sway. MethodsPosturography was performed in eight healthy participants using a stabilometer with foam rubber on board. The center of pressure (COP) trajectories were recorded in both the anterior–posterior and medial–lateral directions for 60 s with the eye closed. Neodymium magnets (0.4 T) or aluminum disks of similar size (0 T) were placed bilaterally over the mastoid processes. ResultsBoth the trajectory length and envelopment area of the COP movement with 0.4 T were significantly smaller than those with 0 T. SignificanceThe relatively smaller magnetic vestibular stimulation decreased postural sway. This method may be useful for improving the vestibular function and related reflexes.

Thermoelastic response of a finite thick annular disc with radiation-type conditions via time fractional-order effects

The study investigates thermal interactions in a two-dimensional time fractional-order thermoelastic problem in a homogeneous, isotropic, and perfectly conducting thick annular disc subjected to a point impulsive sectional heat source. We utilize unconventional integral transformation techniques to study the thermoelastic response of a disc, in which an internal heat source is generated according to the linear function of the temperature and radiation-type boundary conditions. The time fractional-order thermoelastic theory is used to determine temperature, displacement, and stresses through a series of Bessel functions. Numerical calculations analyze fractional-order parameters on aluminum discs, incorporating time-based fractional derivatives into field equations for practical engineering scenarios, enhancing thermal properties analysis.

Friction and corrosion characteristics of microarc oxidation/laser cladding palygorskite coating on 6061 aluminum alloy substrates

In this study, micro arc oxidation (MAO) technology was used to surface coating of 6061 aluminum (Al) disk. Then laser is used to clad palygorskite (Pal) on the surface of the MAO coating to improve the protection of the coating against the Al substrate. The laser irradiates heat onto the Pal powder, the Pal is heated and at the same time the MAO coating is affected by the heat, and the MAO coating is cooled and cured along with the Pal to form the MAO- Pal composite coating. The surface morphology, elemental composition and phase composition of the MAO-Pal coating were analyzed using scanning electron microscopy, energy spectroscopy and X-ray diffraction. And friction experiments were performed on the MAO- Pal coating. The results showed that the coefficient of friction (COF) of the MAO-Pal coating was reduced by 27 % compared to the Al substrate and 19 % compared to the MAO coating under water lubrication conditions. Through the corrosion resistance experiments, the corrosion potential (Ecorr) of the MAO- Pal coating increased by 0.197 V compared to the Al substrate and 0.280 V compared to the MAO coating, and the corrosion current density (Icorr) simultaneously decreased by three orders of magnitude compared to the Al substrate and one order of magnitude compared to the MAO coating. The MAO- Pal coating prepared by laser cladding Pal had good wear and corrosion resistance, which improved the service life and application range of Al alloy and was expected to promote the development of Al alloy in the application field.

Tribological properties of aluminum alloy coated with graphene oxide/polyvinyl alcohol composites after micro-arc oxidation

PurposeAluminum alloy is considered an ideal material in aerospace, automobile and other fields because of its lightweight, high specific strength and easy processing. However, low hardness and strength of the surface of aluminum alloys are the main factors that limit their applications. The purpose of this study is to obtain a composite coating with high hardness and lubricating properties by applying GO–PVA over MAO coating.Design/methodology/approachA pulsed bipolar power supply was used as power supply to prepare the micro-arc oxidation (MAO) coating on 6061 aluminum sample. Then a graphene oxide-polyvinyl alcohol (GO–PVA) composite coating was prepared on MAO coating for subsequent experiments. Samples were characterized by Fourier infrared spectroscopy, X-ray diffraction, Raman spectroscopy and thermogravimetric analysis. The friction test is carried out by the relative movement of the copper ball and the aluminum disk on the friction tester.FindingsResults showed that the friction coefficient of MAO samples was reduced by 80% after treated with GO–PVA composite film.Originality/valueThis research has made a certain contribution to the surface hardness and tribological issues involved in the lightweight design of aluminum alloys.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0427/

Laser-induced fluorescence detection of nitroxyl (HNO) formed from the thermal decomposition of hydroxylammonium nitrate vapor

The decomposition of the ionic liquid hydroxylammonium nitrate (HAN) produces gas phase products which have utility in spacecraft propulsion systems. Among the various gas phase species generated from HAN decomposition is the nitroxyl (HNO) radical, a highly reactive molecule with implications in both chemical and electric propulsion applications. The work described here used a laser-induced fluorescence platform to directly detect the relative density of the HNO radical formed by passing HAN vapor through heated porous disks of varying composition. The use of heated porous 316-stainless steel and aluminum disks showed significant HNO density production and is attributed to a surface hydrogen abstraction mechanism. There was also evidence of surface modification to the metal disks which resulted in a shift in the HNO density temperature profiles. The results reported demonstrate that use of a heated porous material can easily generate a molecular vapor at moderate temperatures for combustion and electric propulsion applications.

Effect of copper introduction on the properties of micro-arc oxidation coating on powder metallurgy aluminum disk

Powder metallurgy (PM) is a process technology utilizing metals as raw materials that are shaped and sintered to create metallic materials. Micro-arc Oxidation (MAO) is a surface modification technique that improves the surface properties of metals by forming a dense oxide coating on the metal surface. In this study, aluminum‑copper alloys were prepared by introducing copper to PM aluminum disk, and the alloys were treated with MAO. During the PM process, Cu atoms diffuse into the Al particles, filling the gaps in the Al particles and improving the interface bonding strength of the particles. The CuAl2 phase is also generated, which improves the mechanical properties of the alloy. During the MAO process, the addition of Cu filled up the pore defects of the PM Al disk, and a complete and dense oxide coating was formed on the surface of the alloy. The MAO coating was characterized by scanning electron microscopy and X-ray diffraction. The mechanical strength of the alloy was evaluated by metal bending tests. The wear resistance of the coating was evaluated by tribological tests and the wear marks after friction were characterized by metallographic microscopy and energy dispersive spectroscopy. The hardness of coating was evaluated by microhardness tester. The corrosion resistance of the coating was evaluated by electrochemical corrosion tests. The test results show that the substrate after the introduction of Cu by PM and treated by MAO has high strength, high hardness, low coefficient of friction, high wear resistance and high corrosion resistance. It effectively improves the mechanical properties of the alloy, improves the performance of the MAO coating, and improves the service life and application range of the metal.

Task-based detectability in anatomical background in digital mammography, digital breast tomosynthesis and synthetic mammography

Objective. Determining the detectability of targets for the different imaging modalities in mammography in the presence of anatomical background noise is challenging. This work proposes a method to compare the image quality and detectability of targets in digital mammography (DM), digital breast tomosynthesis (DBT) and synthetic mammography. Approach. The low-frequency structured noise produced by a water phantom with acrylic spheres was used to simulate anatomical background noise for the different types of images. A method was developed to apply the non-prewhitening observer model with eye filter (NPWE) in these conditions. A homogeneous poly(methyl) methacrylate phantom with a 0.2 mm thick aluminium disc was used to calculate 2D in-plane modulation transfer function (MTF), noise power spectrum (NPS), noise equivalent quanta, and system detective quantum efficiency for 30, 50 and 70 mm thicknesses. The in-depth MTFs of DBT volumes were determined using a thin tungsten wire. The MTF, system NPS and anatomical NPS were used in the NPWE model to calculate the threshold gold thickness of the gold discs contained in the CDMAM phantom, which was taken as reference. Main results. The correspondence between the NPWE model and the CDMAM phantom (linear Pearson correlation 0.980) yielded a threshold detectability index that was used to determine the threshold diameter of spherical microcalcifications and masses. DBT imaging improved the detection of masses, which depended mostly on the reduction of anatomical background noise. Conversely, DM images yielded the best detection of microcalcification s. Significance. The method presented in this study was able to quantify image quality and object detectability for the different imaging modalities and levels of anatomical background noise.

A numerical investigation of thermal stress induced cracking pattern in the solidifying nuclear fuel droplet during MFCI

During Molten Fuel Coolant Interaction (MFCI) occurring in a Sodium-cooled Fast Reactor (SFR) following a severe accident, the corium jet breaks up into coarse droplets due to hydrodynamic instabilities and fine flaked debris are generated due to the thermal stress cracking occurring on the solidifying droplet. In particular mixed oxide core debris quenched by liquid sodium are more prone to thermal stress cracking because of the excellent heat transport properties of liquid sodium, which leads to a large temperature gradient across the crust of the ceramic fuel. In this paper, thermal stress initiated cracking of solid crust of the nuclear fuel droplet is studied using Fracture Bifurcation Theory (FBT) and Minimum Potential Energy Principle (MPEP). FBT is able to predict the minimum crack length needed for crack propagation or catastrophic failure depending on the computed KI values. On the other hand, MPEP can predict the periodic and hierarchical cracking pattern that can develop on the core debris. This helps in the prediction of number of cracks and the crack length that can develop on the solid crust. Parametric studies have been carried out by varying MOX droplet sizes, crust thickness and cooling conditions and calculating KI by semi-analytical means and comparing it with KIC. The analysis revealed that solidifying droplets with radius equal to or more than 2 mm are susceptible to thermal stress initiated crack growth and catastrophic breakage even if a few tens of micron size initial crack develops on its surface. Then a particular case of 2 mm radius core debris is considered and its cracking pattern is studied by applying MPEP. This optimal crack configuration is obtained by minimizing potential energy for a given range of crack length and spacing. The analysis has been carried out with ANSYS APDL code which calculates the strain energy for a given initial crack length and spacing. The 2D computational model is validated with a similar study carried out for Alumina disc quenched in water and the results are in good agreement. The minimum fine fragment size predicted by the analysis for mixed oxide debris is a flake like debris with equivalent radius of 41 µm when approximated to be a sphere. The particle size correlates well with the fine debris sizes reported in literature of MFCI experiments.

Preparation of alumina disc ceramic membrane with enhanced abrasion resistance for dynamic membrane filtration

Although disc ceramic membranes for dynamic filtration provide notable benefits in reducing membrane contamination, enhancing their resistance to erosive wear remains a challenging task. In this work, boehmite sol was employed as an effective additive to establish tightly connections between the membrane particles, and narrow the pore size of ceramic membrane with the increase of boehmite content. Alumina ceramic membranes with 15 wt% of boehmite sol and sintered at 1250 °C exhibited exceptional mechanical strength of 94 MPa, a porosity of 34 %, and an average pore size of 450 nm. Accelerated erosive wear tests were conducted by adjusting variables such as wear time, rotational speed and silica slurry concentration. It was observed that membranes prepared with 15 % boehmite sol exhibited a wear rate only 1/25th that of the without boehmite sol. Furthermore, the membrane displayed a consistent permeate flux of 1510 L m−2 h−1 bar−1 and a retention rate exceeding 99.5 % when filtering slurry containing 150 g/L of solid contents. After an extended duration of dynamic filtration, the flux and retention rate of the disc membrane exhibit a consistent and stable behavior. This disc ceramic membrane demonstrates promising potential for the filtration of suspensions with high solids content.

Application of pressure-sensitive paint for explosive blast measurements

This study demonstrates the application of fast response pressure-sensitive paint (PSP) to explosively driven blast wave testing. A sprayable polymer ceramic fast response PSP was applied to an aluminium disc before being coated with platinum porphyrin compound as the active luminophore. The disc was then exposed to a blast wave and the response was measured using a high-speed video camera. The PSP measured the transit of the incident shock wave clearly, albeit with a slight response delay following the instantaneous change in pressure. A time domain-based method for improving temporal response, whilst considering both spatial and temporal effects, is described. This study clearly demonstrates that the spatial distribution of a blast wave on a surface may be captured by PSP technology. Integrated parameters such as impulse can correctly be characterised using this method. This technology offers an enhanced and more efficient way of characterising blast.

Freshwater algal biofilm assemblages are more effective than invertebrate assemblages at aggregating microplastics

Microplastics, plastic particles less than 5 mm in length, are a ubiquitous pollutant in the environment, but research on freshwater microplastic contamination is lacking. A possible fate of microplastics in freshwater environments is to become entangled or aggregated in biofilms, which are matrices of algae, bacteria, and micro invertebrates that grow on underwater surfaces, following a progression of settling algae, periphyton, and finally invertebrate colonization. This in-situ study at the Oasis Marina at National Harbor in Oxon Hill, Maryland, examined how the taxonomic assemblages of freshwater biofilms in the Potomac River are associated with the number of microplastics aggregated within them. Aluminum discs, acting as artificial substrate for biofilm growth, were deployed at the water's surface and at 2 m depth to survey biofilm assemblage and were sampled monthly from October 2021–October 2022. Microplastic abundances in the water column were measured every 2 weeks over the same period. Spatial and temporal trends in trapped and suspended microplastics, water quality parameters (temperature, dissolved oxygen, pH, salinity, conductivity, turbidity, ammonia, nitrate, and phosphate), and biofilm assemblages were measured and compared to explore factors affecting the abundance of microplastics and their partitioning between the water column and biofilms. Water quality had no measurable impact on microplastic abundance in the water column at either depth, but temperature was negatively correlated to microplastic abundance in biofilms. As the weather warmed and biofilms progressed to invertebrate settling, they tended to contain fewer microplastics. This may have occurred because less biologically rich biofilms, primarily composed of unicellular algal colonies, provide a favorable surface for microplastic deposition. Understanding seasonal changes in biofilm assemblage and microplastic abundance may help track the fate of microplastics in freshwater systems, particularly in their interactions with lower trophic organisms.

The Effect of an Aluminium Disc Rotator on Polyvinyl Chloride (PVC) Material using 360° Lateral Sliding Disc Triboelectric Generator (TEG)

Triboelectric generatorshave the ability to harvest energy from human activities, mechanical vibration, and other sources to drive minor electronic devices.In many circumstances, charges created from a triboelectric process are referred to as a negative effect or waste energy. Here, this paper will demonstrate an approach of the charging process in friction with a rotator and stator to investigate the effects of rotating speed and the different thickness of electrification to the output voltage. The 360° lateral sliding disc triboelectric generator (TEG) fabricated by connecting an Aluminium disc to the motor as a rotator, while a Polyvinyl Chloride (PVC) sheet placed at the top of an acrylic coated by a copper electrode served as a stator. PVC material with different thicknesses (0.2, 0.5 and 0.7 mm) and grit sizes were used (P500, P1000 and P1500) and prepared prior to the experiment. Thus, three different rotational speeds (500, 1000 and 1500 rpm) were monitored using a tachometer to standardize the speed for each set of experiment. Such as a TEG at 1500 rpm on a 0.2 mm thick sample with P500 grit size modification delivers a maximum voltage output, VRMSof 13.8 mV, with the maximum calculated current of 69 µA and the maximum power density of 0.485 mW/m2.

Multiple shearing induced in one-step deformation fabricating gradient-structured aluminium disks

Repeated deformation or extended time is generally required in producing ultrafine grained structures, while this applies equally to forming gradient structures with ultrafine grains, which have been developed to evade the strength-ductility trade-off in recent years. This paper reports multiple shearing assisted fabrication of gradient-structured (GS) aluminium disks involving ultrafine grain formation in one step through a new process, called radial extrusion machining (REM). Finite element analysis and microstructural observations revealed that REM introduced multiple shearing, which provided hierarchical combinations of shear effects of different origins, intensities, and ranges of influence, resulting in a structural gradient across the disk thickness. The fabricated GS disks exhibited significant refinement of grains from ∼100 µm to submicron scale in the large-strained layers, which is attributable to the promoted multiple shearing. It was demonstrated that the grain refinement process is accelerated with the evolution of mutually crossing deformation or microshear bands introduced by multiple shearing. The operating structural mechanisms responsible for the dynamic formation of new grains were discussed in detail. This study provides a feasible method to fabricate GS disks with ultrafine grains formed in a straightforward and time-efficient way, and offers insights and guidance to develop new processes by introducing multiple shearing.

Inhibitor activity of lactiplantibacillus plantarum LP5 on thermotolerant campylobacter with different biofilm-forming capacities.

To evaluate the biofilm-forming capacity of thermotolerant Campylobacter (TC) strains from poultry production and to analyse the inhibitory capacity of Lactiplantibacillus plantarum LP5 against TC on different materials. Biofilm-forming capacity by Campylobacter jejuni and Campylobacter coli was analysed by cell adhesion in polystyrene plates. TC were classified as non-biofilm-forming (NBF, 1.3%), weak biofilm-forming (WBF, 68.4%), moderate biofilm-forming (MBF, 27.6%), and strong biofilm-forming (SBF, 2.7%). The inhibitory capacity of L. plantarum LP5 against TC was tested on stainless-steel, nylon, aluminium, and glass disks (treated group) and compared with biofilm-forming TC (control group). L. plantarum LP5 was inoculated, and then TC. Biofilm was removed in both experimental groups and TC and LP5 bacterial counts were performed. The L. plantarum LP5 presence reduced the formation of TC biofilm (P<0.001). The material type and strain category influenced biofilm formation, with stainless-steel and the SBF strain being the material and TC having the highest adhesion (P<0.001). L. plantarum LP5 formed similar biofilm on all materials (P=0.823). This trial showed very promising results; L. plantarum LP5 could be incorporated as a bio-protector of TC on different surfaces.

Dense plasma diagnostics with a Nomarski interferometer using a frequency-tripled Ti:sapphire laser

An overdense plasma is considered as a new tool for high-power laser pulse compression. For this purpose, a high density plasma was generated by illuminating an intense fs Ti:sapphire laser pulse onto a surface of an aluminum disk and its spatio-time-resolved dynamics was investigated by a Nomarski interferometer. To probe the laser-produced high density plasma, the original Ti:sapphire laser pulse with a wavelength of 800 nm was frequency-tripled and the UV laser pulse of 266 nm in wavelength was used in the interferometer. It turned out that the fs UV laser interferometer can provide a fairly high density information up to 8.5 × 1020 cm-3. Our experimental result shows that the initial high density plasma near the solid target surface expands rapidly and its density profile in space is gradually reduced to exponential in the ns time scale. This result will provide an important information towards the next step for experimental demonstration of the laser pulse compression using a plasma.

Highly permeable ZIF-8 membranes for C2H4/C2H6 separation in a wide temperature range

Ethylene/ethane separation is a critical and energy-consuming process in the chemical industry due to the similar properties of the compounds and the great need of ethylene for e.g., polymer production. Many materials have been studied for their implementation as membranes as an energetically favorable alternative to conventional distillation and adsorption processes. Metal-organic frameworks (MOF) have revealed promising properties as highly permeable and selective membranes. Among the most studied and promising MOF candidates is ZIF-8, known for its thermal stability and small pores connected by narrow-sized windows. In this work, we present an analysis of the influence of parameters such as temperature, feed pressure and feed flowrate on the separation of ethylene/ethane through a thin ZIF-8/alumina disc membrane. We observed that the temperature has a significant effect on the separation. The ethylene permeance increased with decreased temperature and reached 8.1 × 10−7 mol/(m2·s·Pa) at −30 °C. At this temperature, the ethylene/ethane selectivity was 2.5. The study concluded with a considerable enhancement of the permeance of ZIF-8 membranes for ethylene/ethane separations, while maintaining a good selectivity compared to the reported values in the literature. The results have important implications for the development of more cost-effective and energy-efficient membrane-based separation technologies for ethylene purification.