Mm-thick Sample Research Articles

Effect of wall thickness on the microstructure and properties of a fourth-generation single crystal superalloy

This study investigated the effect of various thicknesses (0.3–1.5 mm) on the as-cast and heat-treated microstructures of the fourth-generation single crystal superalloy. The microstructures and fracture characteristics of samples with various thicknesses were analyzed after high-temperature stress rupture tests at 1100 ℃/137 MPa. The results showed that as the alloy thickness increased from 0.3 mm to 1.5 mm, the degree of segregation between dendritic core and inter-dendritic significantly increased. The increased segregation was attributed to the slower solidification rate of the 1.5 mm-thick sample compared to the 0.3 mm-thick sample. Lower solidification rates and higher degrees of dendritic segregation enhanced the area fraction of eutectics, the primary dendrite arm spacing (PDAS), the and area fraction of pores. After stress rupture tests, the rupture life of the alloy increased from 81 h to 333 h. It was observed that in the 0.3 mm-thick sample, microcracks initiated at the surface and extended into the matrix. On the contrary, as for the 1.5 mm-thick sample, microcracks initiated at the matrix and propagated towards the surface. To evaluate the influence of oxidation, interrupted stress rupture tests were conducted in air atmosphere to investigate the thickness debit effect. Surface oxidation led to the initiation of microcracks on the surface and change the morphology and area fraction of the internal γ′ phase, as well as the effective load-bearing area of the samples. TEM and EBSD were employed to characterize the deformation characteristics of samples with various thicknesses, and the influence of thickness on deformation mechanisms was discussed as well.

Lithium Volatilization and Phase Changes during Aluminum-Doped Cubic Li6.25La3Zr2Al0.25O12 (c-LLZO) Processing

Stabilized Li6.25La3Al0.25 Zr2O12 (cubic LLZO or c-LLZO) is a Li+-conducting ceramic with ionic conductivities approaching 1 mS-cm. Processing c LLZO so that it is suitable for use as a solid state electrolyte in all solid state batteries, however, is challenging due to the formation of secondary phases at elevated temperatures. The work described in this manuscript examines the formation of one such secondary phase La2Zr2O7 (LZO) formed during sintering c LLZO at 1000 °C. Specifically, spatially resolved Raman spectroscopy and X-ray Diffraction (XRD) measurements have identified gradients in Li distributions in the Li ion (Li+)-conducting ceramic Li6.25La3Al0.25 Zr2O12 (cubic LLZO or c-LLZO) created by thermal processing. Sintering c-LLZO under conditions relevant to solid state Li+ electrolyte fabrication conditions lead to Li+ loss and the formation of new phases. Specifically, sintering for 1 h at 1000 °C leads to Li+ depletion and the formation of the pyrochlore lanthanum zirconate (La2Zr2O7 or LZO), a material known to be both electronically and ionically insulating. Circular c-LLZO samples are covered on the top and bottom surfaces, exposing only the 1.6 mm-thick sample perimeter to the furnace’s ambient air. Sintered samples show a radially symmetric LZO gradient, with more LZO at the center of the pellet and considerably less LZO at the edges. This profile implies that Li+ diffusion through the material is faster than Li+ loss through volatilization, and that Li+ migration from the center of the sample to the edges is not completely reversible. These conditions lead to a net depletion of Li+ at the sample center. Findings presented in this work suggest new strategies for LLZO processing that will minimize Li+ loss during sintering, leading to a more homogeneous material with more reproducible electrochemical behavior.

Exploring robust microwave absorption properties of functional polyvinyl butyral (PVB) via facile cross-linking and data-driven material discovery

This work introduces a chemically facile approach for synthesizing cross-linked polyvinyl butyral (XPVB) at room temperature, utilizing divinyl sulfone (DVS) as the cross-linking agent. Leveraging data-driven discovery methods, we optimize the DVS concentration to enhance the material's reflection loss (RL) performance, establishing XPVB as a formidable contender in microwave absorption without the need for conventional filler materials. Gaussian Process Regression (GPR) was used in this analysis, the material's development process was streamlined to achieve a high-fidelity predictive model that closely aligns with the observed experimental data. The synergy between our GPR model and the empirical evidence is particularly noteworthy, with the GPR predictions exhibiting exceptional agreement across the investigated frequency range, especially in the Ku-band, where high RL values are crucial. These findings indicate that XPVB exhibits exceptional dielectric properties that translate into an unprecedented absorption bandwidth encompassing the entire Ku-band, paired with strong RL, thereby achieving a significant attenuation of electromagnetic waves even at minimal material thicknesses. The optimized XPVB sample, without any filler addition, delivers an exceptional RL performance. Notably, a 2.4 mm-thick XPVB sample demonstrated an extraordinary RL value of -44 dB with RL≤-10 dB absorption Ku-bandwidth (12.4–18 GHz), showcasing the material's potential as a standalone absorber. This synthesis methodology, combined with the analytical approach, lays the groundwork for further research and development in microwave absorbers and has the potential to significantly impact the fields of defense, telecommunications and self-powered devices by providing a new standard for material performance.

INSIHGT: A scalable and homogeneous 3D multiplexed molecular mapping platform for spatial biology and precision medicine.

e15180 Background: The dynamic interplay between cancer cells and their microenvironment is a determinant of disease evolution and response to treatment. However, the current state of three-dimensional (3D) tumor microenvironment analysis is hindered by inadequate penetration of antibodies into thick tissue sections, leading to a substantial gap in acquiring unbiased, precise 3D multiplexed immunohistochemistry (IHC) images. Methods: We developed INSIHGT to surmount these limitations by enabling multi-round, multiplexed 3D IHC in standard formalin-fixed tissues. This fully automatable, fast-track method requires a simple series of chemical cocktail exchanges, translating to a tissue-to-image time of 6 days for 1 cm³ samples and as little as 6 hours for biopsy specimens. INSIHGT offers a scalable and efficient solution for detailed 3D spatial mapping of cancerous cells and their interactions within their native context. Results: 3D IHC with INSIHGT shows ideal penetration homogeneity, which quantitatively matches reference signals in 1cm3 samples. We further validated INSIHGT with 309 commercially available primary antibodies and is compatible with simultaneous fluorescent in situ hybridization (FISH) to detect RNA transcripts or DNA chromosomal abnormalities. Notably, the quality of post-INSIHGT traditional histological analyses, such as H&E and standard IHC, was not altered. We demonstrated a 3D mapping of over 20 markers in a 1 mm-thick tumor sample across seven INSIHGT cycles, and an atlas of multiple tumour samples with 3D IHC & H&E. The large datasets seamlessly integrates with single-cell segmentation and analysis workflows, yielding comprehensive maps that elucidate protein expression, cell morphology, spatial positioning, and potential cell-cell interactions. Conclusions: INSIHGT provides an unparalleled level of visualization and analytical detail concerning the spatial dynamics within the tumor microenvironment at a single-cell resolution. As a transformative next generation histopathology platform, it can uncover new structural and molecular details within clinical specimens, accelerating biomarker discovery and novel diagnostic assays development, thereby enriching the field of tumor biology and propelling the progress of personalized oncology treatments.

Giant nonlinear Faraday rotation in iron doped CdMnTe

Polarization rotation is an important parameter in the design of passive and active photonic components (optical isolators, magneto-optical valves, and magnetic field sensors). This effect is particularly important in materials with delocalized electrons and large atomic orbital moments like CdMnTe, which is an excellent candidate due to its large Zeeman splitting that gives rise to large Faraday rotation. In this paper we report a giant intensity dependent nonlinear Faraday rotation in iron doped Cd0.85Mn0.15Te:Fe crystal. Rotation on the order of 12o in magnetic field of the order of 0.55 T and intensities of 1.832 GW/cm2 can be achieved in a 1.9 mm thick sample. This is 60 time larger in magnitude than previously reported values. In large magnetic field, this intensity dependent rotation will be able to compete with two photon absorption in large magnetic fields, and enhance the linear faraday rotation.

Mimicking real-field degradation of biodegradable plastics in soil and marine environments: From product utility to end-of-life analysis

Biodegradable plastics can mitigate plastic waste issues by undergoing hydrolysis and microbial digestion. However, biodegradable plastics face unjust accusations of not decomposing in natural environments, including barren soil or cold oceans, under unsuitable conditions. In this study, we simulated end-of-life of biodegradable plastic products under real-field soil and seawater conditions. Replenishing vermicompost in horticultural topsoil (3:7 wt ratio) activated microbial growth, resulting in significant degradation. In fertile soil, polycaprolactone (PCL) and poly(butylene succinate) (PBS) required fewer than 6-months, for complete degradation, while poly(butylene adipate-co-terephthalate) (PBAT) with more than 51 mol% terephthalate content was rarely degraded. In an artificial seawater aquarium, PCL degraded at the rate of 30 μm per month. The degradation of bioplastics enclosed in coarse nets was superior to that in fine nets, owing to higher aeration and water circulation. Sea waves and current significantly accelerated the rate of PCL-degradation to 89 μm per month in a coastal marine environment; the ranking of rate of decomposition was PCL > PBS > PBAT. After 12 months of biodegradation, the tensile strength and elongation of a 2 mm-thick sample of PCL decreased to 15 MPa and almost 0 %, respectively. 3D-printed jars, designed for octopus fishing, is widely used and its designed mechanical decay aids in preventing the ghost fishing of abandoned gear as demonstrated by artificial conches, illustrating the potential for biodegradable fishing gear.

Lightweight and large-scale rGO reinforced SiBCN aerogels with hierarchical cellular structures exposed to high-temperature environments

SiBCN ceramic aerogel is an ideal potential candidate for ultra-high temperature thermal insulation due to its unique microscopic pore structure combined with the excellent thermal stability of SiBCN ceramic. Here, reduced graphene oxide (rGO) modified SiBCN aerogels (rGO/SiBCN) were prepared through solvothermal, freeze-casting and pyrolysis, and the dimension of the aerogel is up to Φ130 mm × 28 mm. The density of the rGO/SiBCN aerogel is as low as 0.024 g/cm3 and the microstructural regulation is achieved by controlling the rGO content in the aerogel. The hierarchical cellular structure endows the aerogel with a high specific surface area (148.6 m2/g) and low thermal conductivity (0.057 W m−1 K−1). The 10 mm-thick sample exhibits excellent thermal insulation and ablation resistance, as evidenced by its ability to reduce the temperature from ∼1100 °C to ∼180 °C under the intense heat of a butane flame. Moreover, benefiting from the ultrahigh-temperature stability of SiBCN, the rGO/SiBCN aerogel exhibits good thermal stability up to 1200 °C in argon and short-oxidation resistance at 800 °C in air. Therefore, the rGO/SiBCN aerogel with superior overall performance could expand its practical application in high-temperature thermal insulation under extreme environments.

Selective microwave absorption of SiC–Si3N4 porous ceramics prepared by sacrificial template method

Porous SiC–Si3N4 ceramics with various pore structures were prepared by adding different amounts and sizes of pore-forming agents (Polymethyl methacrylate, PMMA). The dielectric and wave absorption properties of porous ceramics were investigated over a wide temperature and frequency range. Increasing the porosity reduced the frequency dependence of complex permittivity. When the porosity increased from 50.97% to 54.59%, the loss tangent was slightly enhanced due to pore-induced polarization. An optimal pore size range enhanced the dielectric properties, beyond which a lower loss tangent was exhibited. Increasing the porosity reduced the temperature dependence of the loss tangent, and the peak of the change rate of the loss tangent moved to a higher temperature. The minimum reflection loss at room temperature can reach - 49.61 dB at 11.91 GHz for a 1.9 mm-thick sample. The minimum reflection loss at 9.72 GHz for 25 vol% PMMA-added porous ceramic with a 2.1 mm-thick material can be as low as - 65.92 dB at 300 °C. The porosity can be changed to achieve selective electromagnetic wave absorption at different temperatures.

In Situ Thermal Ablation Repair of Delamination in Carbon Fiber-Reinforced Thermosetting Composites

Repairing delamination damage is critical to guarantee the structural safety of carbon fiber-reinforced thermosetting composites. The popular repair approaches, scarf repair and injection repair, can significantly restore the in-plane mechanical performance. However, the out-of-plane properties become worse due to the sacrifice of fiber continuity in these repairing processes, leading to the materials being susceptible under service loads. Here, we propose a novel in situ delamination repair approach of controllable thermal ablation in damage removal, achieving a high repair efficiency without impairing the fiber continuity in carbon fiber/epoxy panels. The epoxy resin in the delaminated region was eliminated under the carbonization temperature in a few minutes, allowing the carbon fiber frame to retain its structural integrity. The healing agent, refilled in the damaged region, was cured by the Joule heating of designed electrodes for 30 min at 80 °C, yielding the whole repair process to be accomplished within one hour. For the delaminated carbon fiber/epoxy panels with thicknesses from 2.5 to 6.8 mm, the in-plane compression-after-impact strength after repair could recover to 90.5% of the pristine one, and still retain 74.9% after three successive repair cycles of the 6.8 mm-thick sample. The simplicity and cost-saving advantages of this repair method offer great potential for practical applications of prolonging the service life of carbon fiber-reinforced thermosetting composites.

Influencing the Shape Recovery and Thermomechanical Properties of 3DP PLA Using Smart Textile and Boehmite Alumina and Thermochromic Dye Modifiers

The technology of 4DP utilizes shape memory materials (SMMs). Among the SMMs, SMP is the material that has potential and is ideal for this technology. However, due to their restrictions, fillers are incorporated to produce a novel shape memory polymer composite (SMPC). The objective of the present work was to investigate how the modification of PLA via the incorporation of boehmite alumina and thermochromic dye, and the use of 3DP on polyester fabric to make smart material textiles (SMT), influenced the shape-memory properties of printed objects. SMPCs with 3 wt% BA particles were prepared by means of the fused deposition modelling (FDM) process, with heat used as an actuation. It was demonstrated that sample thickness and the method of PLA modification affected the shape recovery of 3D-printed objects. All neat PLA samples recovered their angle fully for all thicknesses, while modified PLA incorporated with BA particles and dye recovered its initial angle fully at 1 mm thickness and showed less recovery for 1.5- and 2 mm-thicknesses. The 1 mm-thick sample was then chosen for printing onto the textile material for all samples. When printed onto the fabric, the neat PLA and SMPCs recovered their initial shapes fully, while samples with the dye added into the PLA and SMPC did not recover their initial shape fully due to the presence of the dye, which hindered the movement of the polymer chains. SEM revealed good layer bonding for the SMPCs compared to the neat PLA, which led to improved mechanical properties. The thermal stability of PLA was improved by the BA particles; furthermore, the dye and BA particles nucleated the crystallization of PLA, resulting in an enhanced storage modulus. Overall, a biodegradable 3D-printed object of 1 mm in thickness with improved thermal and mechanical properties was produced, with and without the use of the textile.

Graphene-Based Thermoplastic Composites as Extremely Broadband and Frequency-Dependent EMI Absorbers for Multifunctional Applications

Multifunctional materials are the future of modern electronics. The reduction of weight and no interfacial mismatches perfectly fit the requirements of those industry sectors which require miniaturization, low weight, and high functionality, like aerospace or wearable electronics. Here, we show multifunctional thermoplastic polymer composites based on acrylonitrile–butadiene–styrene (ABS) with graphene nanoplatelet (GNP) inclusions at different weight loadings of GNPs, from the pure polymer up to 10 wt %. The multifunctionality is expressed via efficient electromagnetic interference (EMI) shielding in an extensive frequency range, from microwave to terahertz, and good electrical conductivity and heat management. The highest measured total shielding efficiency reached over 80 dB per 1 mm-thick sample in the terahertz range for the 5 wt % GNP concentration. Composites with the highest GNP loading show high thermal conductivity of 1.8 W/mK and an electrical conductivity of 188 S/m. All composites exhibited absorption as the primary shielding mechanism. These are some of the highest EMI shielding efficiency and thermal conductivity values reported in the literature. Our results suggest that the ABS/GNP composites reported here are suitable for multifunctional EMI absorber/heat management applications.

(AlCrMg)x(PO4)y/MgO composite: A new thermal protection and insulation material up to 2400 °C

A (AlCrMg)x(PO4)y/MgO composite(APMC) was prepared based on the acid–base reaction between MgO and chromium aluminum phosphate solution for thermal protection and insulation applications at ultrahigh-temperatures up to 2400 °C. The compositions, formation mechanisms, microstructure, mechanical properties, thermal conductivity and ablation resistance of the composite were systematically investigated. The results show that the (AlCrMg)x(PO4)y/MgO composite can be consolidated in different shapes at room temperature. The compressive strength of the as-prepared porous composites is higher than 20 MPa due to the macromolecular network structure, and it can be further improved to 42 MPa via thermal treatment. After ablation by an oxyacetylene flame at 2400 ± 70 °C for 60 s, the mass and line ablation rates of the composite were 0.0195 g/s and 0.43 × 10−3 mm/s, respectively, which are comparable to those of ultrahigh-temperature ceramics. The excellent ablation resistance can be attributed to the in situ formation of a dense protective layer composed of spinel MgCr2O4 and MgO phases. Interestingly, during ablation at 2400 °C the back-side temperature of the 15 mm-thick sample was lower than 130 °C, suggesting outstanding thermal insulation performance. The temperature gradient leads to the formation of a gradated porous structure which reduces the overall thermal conductivity of the composite.

Potential alpha particle detection with thin poly (ether sulfone) substrates

Plastics without fluorescent-molecule doping have attracted increasing attention as radiation detection components in measurement systems to ensure safe nuclear reactors and radiation facilities. A promising candidate is poly (ether sulfone) (PES), which is resistant to environmental stress. Here, we show that transparent PES responds rapidly to alpha particles despite its amber colouration. Specifically, 1- and 5 mm-thick PES samples were exposed to an 241Am radioactive source, and the induced PES fluorescence was acquired with a photodetector. The overall system responses were comparable to the intrinsic detector response. The averaged time profiles of the acquired fluorescence pulses for each sample exhibited leading edges that exponentially increased with rise times of 3.3 ± 0.1 ns. The falling tails exponentially decreased with decay times of 12.4 ± 0.1 ns and 12.1 ± 0.3 ns. The maximum intensity from the 1 mm-thick sample was approximately 2.4 times greater than that from the 5 mm-thick sample. This knowledge will lead to future PES applications in radiation measurements.

Research on influencing factors of fatigue performance of cruciform welded joints on offshore platforms

In this study, the fatigue life of load-carrying cruciform welded joints under various plate thicknesses and degrees of penetration was performed. The fatigue assessment results showed a significant “thickness effect.” The fatigue limit of the 25 mm-thick sample was 13.4% lower than that of the 16 mm-thick fatigue sample. Essentially, the fatigue life of the weld toe does not change with the degree of penetration. Plate thickness is the key factor affecting the fatigue life. The thickness effect is determined by both the stress gradient along the plate thickness and the degree of surface stress concentration. The correction result based on the effective notch stress approach is more accurate than the thickness correction formula in the ABS standard, which underestimates the thickness effect of load-carrying cruciform welded joints and may lead to danger. The penetration ratio a/t affects the fatigue failure position of load-carrying cruciform welded joints. The fatigue design of load-carrying cruciform welded joints can be performed by appropriately increasing the degree of penetration while achieving the damage at the weld toe.

Fabrication, microstructures, and optical properties of Yb:Lu2O3 laser ceramics from co-precipitated nano-powders

The Yb:Lu2O3 precursor made up of spherical particles was synthesized through the co-precipitation method in the water/ethanol solvent. The 5 at% Yb:Lu2O3 powder is in the cubic phase after calcination at 1100 °C for 4 h. The powder also consists of spherical nanoparticles with the average particle and grain sizes of 96 and 49 nm, respectively. The average grain size of the pre-sintered ceramic sample is 526 nm and that of the sample by hot isostatic pressing grows to 612 nm. The 1.0 mm-thick sample has an in-line transmittance of 81.6% (theoretical value of 82.2%) at 1100 nm. The largest absorption cross-section at 976 nm is 0.96×10−20 cm2 with the emission cross-section at 1033 nm of 0.92×10−20 cm2 and the gain cross sections are calculated with the smallest population inversion parameter β of 0.059. The highest slope efficiency of 68.7% with the optical efficiency of 65.1% is obtained at 1033.3 nm in quasi-continuous wave (QCW) pumping. In the case of continuous wave (CW) pumping, the highest slope efficiency is 61.0% with the optical efficiency of 54.1%. The obtained laser performance indicates that Yb:Lu2O3 ceramics have excellent resistance to thermal load stresses, which shows great potential in high-power solid-state laser applications.

Interlayer thickening for development of laser-welded Ti-SS joint strength

This paper investigates the mechanical strength and microstructural characterization of the laser beam-welded Ti6Al4V-304 stainless steel (SS) joints using different interlayer thicknesses at single and double interlayer structures. This study attempts to increase the Ti-SS joint strength through changing the Cu interlayer thickness. In single interlayer experiments using 0.5 mm-, 1 mm-, and 1.5 mm-thick Cu, the greatest strength was reached at a laser power of 4 kW using 1 mm-thick Cu. Energy dispersive spectroscopy (EDS) and X-Ray diffraction (XRD) characteristics showed that some FeTi and Fe2Ti were formed along the fracture propagation path of a 0.5 mm-thick Cu sample; however, no Fe-Ti IMCs or Cr2Ti could be found in the 1 mm-thick Cu sample. Meanwhile, αTi + FeTi and CuTi + CuTi2 compounds fractured in 0.5 mm- and 1 mm-thick Cu joints, respectively, after the tensile testing. Electron backscatter diffraction (EBSD) observation showed that the fracture happened through grain boundaries of CuTi and Cu3Ti2 compounds at a 0.5 mm-thick Cu joint; however, that happened approximately along the grain boundaries of Cu4Ti-Cu3Ti2 for the 1 mm-thick Cu joint. For double interlayer experiments, the XRD result of the SS-Cu0.5-V-Ti sample showed the formation of the Fe2Ti and FeTi at the fracture surface, while the fracture surface of the SS-Cu1-V-Ti sample primarily contained some Cu-Ti IMCs. The microstructures of the fracture edges indicated that the eutectic FeTi + Fe2Ti and eutectoid αTi + Ti2Cu fractured after the tensile testing at the SS-Cu0.5-V-Ti and SS-Cu1-V-Ti samples, respectively. EBSD observation indicated that the fracture happened primarily along the low angle grain boundaries of Cu3Ti2 and αTi compounds at the SS-Cu1-V-Ti joint; however, the fracture occurred intergranularly along the high angle grain boundaries of the Fe2Ti in the SS-Cu0.5-V-Ti joint. Investigation showed that the joint strength and also the elongation of the SS-Cu1-V-Ti joint are approximately 179% and 10 times greater than those found in the SS-Cu0.5-V-Ti joint.

Including Liquid Metal into Porous Elastomeric Films for Flexible and Enzyme-Free Glucose Fuel Cells: A Preliminary Evaluation

This communication introduces a new flexible elastomeric composite film, which can directly convert the chemical energy of glucose into electricity. The fabrication process is simple, and no specific equipment is required. Notably, the liquid metal Galinstan is exploited with a two-fold objective: (i) Galinstan particles are mixed with polydimethylsiloxane to obtain a highly conductive porous thick film scaffold; (ii) the presence of Galinstan in the composite film enables the direct growth of highly catalytic gold structures. As a first proof of concept, we demonstrate that when immersed in a 20 mM glucose solution, a 5 mm-long, 5 mm-wide and 2 mm-thick sample can generate a volumetric power density up to 3.6 mW·cm − 3 at 7 mA·cm − 3 and 0.51 V without using any enzymes.

Investigations on the sound field between waveguide and counterpart induced by high-intensity focused ultrasound in thin polymer films

The use of high-intensity focused ultrasound (HIFU) to heat polymer films is getting more in focus of interest in the industry due to some advantages e.g. low damages of thin polymer films during film processing or cost reduction of the processing tool. The capability to heat thin polymer films using a solid waveguide transducer was already reported in the literature. However, some significant hurdles persist: the physical principles responsible for the heating of thin polymer films are not fully understood. This study aims to investigate the sound field occurring in thin polymer films between a solid waveguide transducer (having a resonance frequency of 1.1 MHz) and a solid counterpart and compared it to the sound field in mm-thick polymer sample. An analogy between the sound field measured in water and the sound field inside polymer films during the heating process is done. The sound field between counterpart and solid waveguide is analyzed by means of membrane hydrophone sound field measurements and finite element simulations. The impact of the transducer-counterpart gap size is studied. This investigation reveals that the behavior and characteristics of the sound field in water in a transducer-counterpart gap differ considerably from each other depending on the gap size. When the gap is smaller than a wavelength, the sound cannot be focused within the waveguide-counterpart gap and complex interferences occur inside the small gap. Furthermore, the investigation showed that similarities occur between the sound field measured in water and the sound field calculated in polymer. These findings are relevant for the understanding of HIFU-based processes involving thin polymer films.

Sound absorption of several various nickel foam multilayer structures at aural frequencies sensitive for human ears

Abstract Using the three-dimensional reticular nickel foam as experimental material, the sound absorption performance was investigated for several various multilayer structures in the frequency range of 2000–4000 Hz, which is aurally sensitive for human ears. The results showed that the 7.5 mm-thick foam sample, which was formed by piling of 5-layer foam plate (thickness: 1.5 mm; porosity: 96%; average pore-diameter: 0.65 mm) could exhibit an excellent sound absorption effect at 4000 Hz, with the absorption coefficient about 0.8. Constituting alternate air gap with the total thickness of about 18.5 mm can greatly improve the absorption performance at relatively low frequencies of 2000–3150 Hz, with the absorption coefficient up to about 0.5 or more. In addition, the research showed that alternate piling up the perforated plate inside the foam plates can also achieve a quite good effect of sound absorption at relatively low frequencies.

An experimental and simulation study on build thickness dependent microstructure for electron beam melted Ti–6Al–4V

Build thickness dependent microstructure of electron beam melted (EBM®) Ti–6Al–4V has been investigated from both experiment and simulation using four block samples with thicknesses of 1, 5, 10 and 20 mm. We observe a mixed microstructure of alternate α/β with some α′ martensite inside the 1 mm-thick sample. By contrast, only the alternate α/β microstructure with both colony and basket-weave morphologies occurs inside the 5 mm-, 10 mm- and 20 mm-thick samples. It is found that β spacing is constantly increased with the build thickness, leading to an obvious decrease in microhardness. Finite element method (FEM) simulations show that cooling rates and thermal profiles during EBM process are favorable for the formation of martensite. Moreover, full-scale FEM simulations reveal that the average temperature inside the samples is higher as the build thickness increases. It suggests that martensitic decomposition is faster in thicker samples, which is in good agreement with the experimental observations.