Sample Thickness Research Articles

Natural rubber based elastocaloric solid-state refrigeration device: design and performances of a single stage system

The elastocaloric effect denotes the ability of a material to release or absorb heat when the material is stretched and released respectively. This effect may be used to design an alternative cooling device. This work focuses on the development of a cooling device using natural rubber (NR) as the elastocaloric material. It consists of a solid–solid heat exchange between a cyclically stretched elastocaloric material and two exchangers, respectively put in contact with the elastocaloric material when it is stretched or released. An experimental device was designed and tested in order to assess the temperature span and cooling power (PC) achievable by NR based single stage device. The effect of the thickness of the NR is also discussed. It is shown that it was possible to transfer nearly 60% of the heat absorption potential of the NR from the cold heat exchanger. From the measurements, the highest PC was found to be 390 mW (430 W kg−1) for a 600 µm thick sample, and 305 mW (540 W kg−1) for a 400 µm thick sample. The temperature span was found to be similar for both materials, ranging 1.5 °C–1.9 °C.

Topological Spin Textures in an Insulating van der Waals Ferromagnet.

Generation and control of topological spin textures constitutes one of the most exciting challenges of modern spintronics given their potential applications in information storage technologies. Of particular interest are magnetic insulators, which due to low damping, absence of Joule heating and reduced dissipation can provide energy-efficient spin-textures platform. Here, it is demonstrated that the interplay between sample thickness, external magnetic fields, and optical excitations can generate a prolific paramount of spin textures, and their coexistence in insulating CrBr3 van der Waals (vdW) ferromagnets. Using high-resolution magnetic force microscopy and large-scale micromagnetic simulation methods, the existence of a large region in T-B phase diagram is demonstrated where different stripe domains, skyrmion crystals, and magnetic domains exist and can be intrinsically selected or transformed to each-other via a phase-switch mechanism. Lorentz transmission electron microscopy unveils the mixed chirality of the magnetic textures that are of Bloch-type at given conditions but can be further manipulated into Néel-type or hybrid-type via thickness-engineering. The topological phase transformation between the different magnetic objects can be further inspected by standard photoluminescence optical probes resolved by circular polarization indicative of an existence of exciton-skyrmion coupling mechanism. The findings identify vdW magnetic insulators as a promising framework of materials for the manipulation and generation of highly ordered skyrmion lattices relevant for device integration at the atomic level.

The sound absorption of air permeable structures produced by 3D printing using PLA material

The aim of the contribution is comparison of noise absorption properties of two designs of acoustic dampening air permeable structures. A circular test samples with a diameter of 89 mm and three different thicknesses of samples were produced using of 3D printing process. In addition to the thickness, the internal structure of the samples was also changed. The prepared samples were tested using an impedance tube. The acoustic properties of the test samples were investigated in accordance with the standards ASTM E1050-19, E2611-17 and ISO 10534-2. A two-microphone method based on the calculation of transfer function method was used to determine the absorption coefficient of the designed structures. The Brüel&Kjær PULSE system was used to estimate the frequency dependence of sound absorption coefficient of test samples. In the paper are presented the experimentally obtained values of the sound absorption coefficient for different structure design and thicknesses of samples produced by 3D printing technology. The measurements were evaluated in the range of working frequencies of the impedance tube.

Microscopic transmittance spectroscopy using a supercontinuum laser source

A supercontinuum laser source emitted from an optical fiber is suitable for developing microscopic transmittance spectroscopy. The microscopic supercontinuum transmittance spectrum can be taken with a fiber probe or a reflective objective. The reflective objective is only suitable for measuring a very thin sample of a thickness less than 1 µm. Therefore, while measuring a relatively thick sample, the fiber probe is the better choice because it effectively simplifies the system without lowering the resolution. The spatial resolution of the microscopic transmittance spectrum as a function of the optical wavelength, measurement distance, and sample thickness is quantitatively evaluated for a fiber probe.

Development of a flexible composite based on vulcanized silicon casting with bismuth oxide and characterization of its radiation shielding effectiveness in diagnostic X-ray energy range and medium gamma-ray energies

The study aims to develop a novel, lead-free, flexible and lightweight composite shielding material against ionizing radiation. For this, it was used bismuth oxide (Bi2O3) in RTV-2 silicon matrix. The shielding tests were carried out in both diagnostic X-ray energies and intermediate gamma-ray energy range of up to 662 keV to determine the radiation attenuation properties of this material in terms of attenuation ratio, half value layer, tenth value layer, mean free path and lead equivalency of samples in weight of 30%, 40%, 50% in Bi2O3. In the diagnostic X-ray energy range, half value layer, tenth value layer and lead equivalency (in mm Pb) of the produced samples were measured at 80 and 100 kVp narrow beam conditions according to the requirements of EN IEC 61331-1 standard. The results show that lead equivalent values of the produced novel sheets was measured to be 0.16 mm Pb, corresponding to a 6 mm thickness of the flexible sample when it contains 30% wt. Bi2O3 in RTV matrix. The experimental findings for durability and flexibility also indicated that this new RTV-based flexible, lead -free shielding composite can be used safely for especially for manufacturing aprons, garments and thyroid guards used in mammography, radiology, nuclear medicine and dental applications in practice.

Monte Carlo simulation of electron interactions in an MeV-stem for thick frozen biological sample imaging

Monte Carlo simulation of electron interactions in an MeV-stem for thick frozen biological sample imaging

Cold atmospheric plasma (CAP) treatment increased reactive oxygen and nitrogen species (RONS) levels in tumor samples obtained from patients with low-grade glioma

Low-grade gliomas (LGGs) are a heterogeneous group of tumors with an average 10-year survival rate of 40%–55%. Current treatment options include chemotherapy, radiotherapy, and gross total resection (GTR) of the tumor. The extent of resection (EOR) plays an important role in improving surgical outcomes. However, the major obstacle in treating low-grade gliomas is their diffused nature and the presence of residual cancer cells at the tumor margins post resection. Cold Atmospheric Plasma (CAP) has shown to be effective in targeted killing of tumor cells in various glioma cell lines without affecting non-tumor cells through Reactive Oxygen and Nitrogen Species (RONS). However, no study on the effectiveness of CAP has been carried out in LGG tissues till date. In this study, we applied helium-based CAP on tumor tissues resected from LGG patients. Our results show that CAP is effective in promoting RONS accumulation in LGG tissues when CAP jet parameters are set at 4 kV voltage, 5 min treatment time and 3 lpm gas flow rate. We also observed that CAP jet is more effective in thinner slice preparations of tumor as compared to thick tumor samples. Our results indicate that CAP could prove to be an effective adjunct therapy in glioma surgery to target residual cancer cells to improve surgical outcome of patients with low-grade glioma.

Local-orbital ptychography for ultrahigh-resolution imaging.

Technical advances paired with developments in methodology have enabled electron microscopy to reach atomic resolution. Further improving the information limit in microscopic imaging requires further improvements in methodology. Here we report a ptychographic method that describes the object as the sum of discrete atomic-orbital-like functions (for example, Gaussian functions) and the probe in terms of aberration functions. Using this method, we realize an improved information limit of microscopic imaging, reaching down to 14 pm. High-quality probes and objects contribute to superior signal-to-noise ratios at low electron doses, allowing for relaxation of the sample thickness restriction to 50 nm for dense materials. Additionally, our method has the capability to decompose the total phase into element components, revealing that the information limit is element dependent. With enhanced spatial resolution, signal-to-noise ratio and thickness threshold compared with conventional ptychography methods, our local-orbital ptychography may find applications in atomic-resolution imaging of metals, ceramics, electronic devices or beam-sensitive material.

Structural, thermal, magnetic and microwave-absorbing properties of spinel-structured high entropy oxide (MnFeCoNiX)3O4 (X = Zn, Cu, Cr)

Within the present work, a series of spinel-structured (MnFeCoNiX)3O4 (X = Zn, Cu, Cr) high entropy oxides (HEOs) were fabricated by co-precipitation method and the subsequent heat treatment. The phase composition, microstructure, thermal stability, magnetic property and electromagnetic (EM) wave loss ability were comprehensively studied. It is found that spinel-structural (MnFeCoNiX)3O4 HEOs are well-crystallized at above 800 °C with a space group Fd-3m. Morphological analysis reveals that grains of different HEOs contain nano-domains with particle sizes between 100 nm and 500 nm. In addition, Mn, Ni, Co, Fe, Zn, Cr and Cu elements are homogeneously distributed and the chemical states of Mn, Ni, Co and Fe are all +2 and + 3, while Cu only exists in +2 state. Thermal stability analysis shows that (MnFeCoNiCu)3O4 HEO is able to keep stable at 1000 °C. Moreover, the (MnFeCoNiCu)3O4 sample exhibits the best magnetic properties and EM microwave loss ability in comparison with (MnFeCoNiZn)3O4 and (MnFeCoNiCr)3O4. For (MnFeCoNiCu)3O4, the values of saturation magnetization (Ms) and coercivity (Hc) are 38.6 emu/g and 52.6 Oe, respectively. Meanwhile, (MnFeCoNiCu)3O4 displays a minimum reflection loss (RL) of −15.5 dB at 8.48 GHz with a thickness of 4.5 mm and a wide effective absorption bandwidth (EAB) of 8.84 GHz with the sample thickness of 5 mm. It is expected that the excellent high-temperature stability and good EM wave absorbing performance of high entropy (MnFeCoNiCu)3O4 could make it potentially useful in EM wave absorption under elevated temperatures.

Ni/Bi bilayers: The effect of thickness on the superconducting properties

Nickel/bismuth (Ni/Bi) bilayers have recently attracted attention due to the occurrence of time-reversal symmetry breaking in the superconducting state. Here, we report on the structural, magnetic, and electric characterization of thin film Ni/Bi bilayers with several Bi thicknesses. We observed the formation of a complex layered structure depending on the Bi thickness caused by the inter-diffusion of Bi and Ni which leads to the stabilization of NiBi3 at the Bi/Ni interface. The superconducting transition temperature and the transition width are highly dependent on the Bi thickness and the layer structure. Magnetoelectric transport measurements in perpendicular and parallel magnetic fields were used to investigate the temperature-dependent upper critical field within the framework of the anisotropic Ginzburg–Landau theory and the Werthamer–Helfand–Hohenberg model. For thicker samples, we observed a conventional behavior, similar to that shown by NiBi3 bulk samples, including a small Maki parameter (αM=0), no spin–orbit scattering (λSO=0) and nearly isotropic coherence length (γ=ξ⊥(0)/ξ∥(0)≈1). The values obtained for these properties are close to those characterizing NiBi3 single crystals. On the other hand, in very thin samples, the Maki parameter increases to about αM=2.8. In addition, the coherence length becomes anisotropic (γ=0.32) and spin–orbit scattering (λSO=1.2) must be taken into account. Our results unequivocally show that the properties characterizing the superconducting state in the Ni/Bi are strongly dependent on the sample thickness.

A polarization-sensitive, high on/off ratio and self-powered photodetector based on Nb2CT x and Nd2CT x @MoS2

MXene two-dimensional materials have been widely used in energy storage, catalysis, sensing and other fields, Nb2C as a typical two-dimensional MXene material, its exploration in the field of optoelectronics is still in its infancy, especially Nb2C-based photodetectors are still to be developed. This paper demonstrates that two-dimensional films based on few-layer Nb2C have a photoelectric response in the wavelength range from visible to near-infrared. We have found that the light response performance can be easily adjusted by controlling the thickness of the spin-coated film, and that Nb2C photodetectors show great advantages in terms of wide bandwidth, polarization response, high switching ratio, etc. By adjusting the material concentration and sample thickness, the photocurrent can reach up to 330 nA, the switching ratio can reach 410, and the responsivity can reach 8.3 × 10−4 A W−1. In the polarization characteristic test, an extinction ratio of 7.6 can be obtained. By adjusting the content of that doped MoS2 quantum dot, the dark current can reach 7.6 × 10−13 A, and the switching ratio can reach 3 × 105, which can be increased by 700 times. The above results show that the few-layer Nb2C nanosheets can be used as optoelectronic detectors in the visible to near-infrared bands, which further broadens the application prospects of two-dimensional MXene.

Lab-scale and full-scale industrial composting of biodegradable plastic blends for packaging.

The acceptance of compostable plastic packaging in industrial composting plants is not universal despite available certification due to the persistence of plastic residues after composting. To better understand this discrepancy, this study compared the disintegration rates of two blends designed for rigid packaging (polylactic acid based) and soft packaging (polybutylene succinate based) in lab-scale composting tests and in an industrial composting plant. A lab-scale composting test was conducted in triplicates according to ISO 20200 for 4, 8 and 12 weeks to check the disintegration potential of the blends. Duplicate test material were then exposed in the compost pile of an industrial composting plant for a duration of 3 weeks and compared with a supplementary lab-scale test of the same duration. The rigid packaging samples (1 mm thickness) retained on average 76.4%, 59.0% and 55.7% of its mass after 4, 8 and 12 weeks respectively in the lab-scale. In the plant, the average remaining mass was 98.3%, much higher compared to the average of 68.9% after 3 weeks in the supplementary lab-scale test. The soft packaging samples (109±9 µm sample thickness) retained on average 45.4%, 10.9% and 0.3% of its mass after 4, 8 and 12 weeks respectively in the lab-scale. In the plant, a high average remaining mass was also observed (93.9%). The supplementary lab-scale test showed similar remaining mass but higher fragmentation after 3 weeks. The results show that the samples achieved significant disintegration in the lab-scale but not in the plant. The difference between the tests that might further contribute to the differing degradation rates is the composition and heterogeneity of the composting substrate. Therefore, the substrate composition and thermophilic composting duration of individual plants are important considerations to determine the suitability of treating compostable plastic in real-world conditions.

Laboratory X-ray Microscopy of 3D Nanostructures in the Hard X-ray Regime Enabled by a Combination of Multilayer X-ray Optics.

High-resolution imaging of buried metal interconnect structures in advanced microelectronic products with full-field X-ray microscopy is demonstrated in the hard X-ray regime, i.e., at photon energies > 10 keV. The combination of two multilayer optics-a side-by-side Montel (or nested Kirkpatrick-Baez) condenser optic and a high aspect-ratio multilayer Laue lens-results in an asymmetric optical path in the transmission X-ray microscope. This optics arrangement allows the imaging of 3D nanostructures in opaque objects at a photon energy of 24.2 keV (In-Kα X-ray line). Using a Siemens star test pattern with a minimal feature size of 150 nm, it was proven that features < 150 nm can be resolved. In-Kα radiation is generated from a Ga-In alloy target using a laboratory X-ray source that employs the liquid-metal-jet technology. Since the penetration depth of X-rays into the samples is significantly larger compared to 8 keV photons used in state-of-the-art laboratory X-ray microscopes (Cu-Kα radiation), 3D-nanopattered materials and structures can be imaged nondestructively in mm to cm thick samples. This means that destructive de-processing, thinning or cross-sectioning of the samples are not needed for the visualization of interconnect structures in microelectronic products manufactured using advanced packaging technologies. The application of laboratory transmission X-ray microscopy in the hard X-ray regime is demonstrated for Cu/Cu6Sn5/Cu microbump interconnects fabricated using solid-liquid interdiffusion (SLID) bonding.

Anatomy of the dielectric behavior of methyl-m-toluate glasses during and after vapor deposition.

Glassy films of methyl-m-toluate have been vapor deposited onto a substrate equipped with interdigitated electrodes, facilitating in situ dielectric relaxation measurements during and after deposition. Samples of 200nm thickness have been deposited at rates of 0.1 nm/s at a variety of deposition temperatures between 40K and Tg = 170K. With increasing depth below the surface, the dielectric loss changes gradually from a value reflecting a mobile surface layer to that of the kinetically stable glass. The thickness of this more mobile layer varies from below 1 to beyond 10nm as the deposition temperature is increased, and its average fictive temperature is near Tg for all deposition temperatures. Judged by the dielectric loss, the liquid-like portion of the surface layer exceeds a thickness of 1nm only for deposition temperatures above 0.8Tg, where near-equilibrium glassy states are obtained. After deposition, the dielectric loss of the material positioned about 5-30nm below the surface decreases for thousands of seconds of annealing time, whereas the bulk of the film remains unchanged.

Unsaturated out-of-plane permeability measured with three-dimensional flow monitoring by etched optical fiber sensors

In our work, the three-dimensional flow in stacks of biaxial E-glass fiber non-crimp fabrics (NCF) and unidirectional carbon fiber layers was monitored by the etched optical fiber sensors embedded inside the fabric stack. The influence of embedding sensors with a diameter of 200 µm on the flow was experimentally illustrated and discussed. The out-of-plane permeability of the two fabric materials was estimated with a radial infusion model using the in-plane permeability values as the prior knowledge. The assumed radius of the semi-ellipsoidal flow was derived and showed a good agreement with the results obtained by the best fit of the exact solution, which provides an approximate solution that simplifies the calculation process. The asymptotic form and the modified semi-ellipsoidal inlet radius method for the case of a non-negligible radius of injection tube compared to the fabric sample thickness were verified. The uncertainties related to the unknown flow pattern near the inlet were also demonstrated. The presented results facilitate the further development and standardization of out-of-plane permeability measurement methods with embedded sensors.

Fabrication and study of the strontium fluoroarsenate Sr5(AsO4)3F (SFAs) transparent ceramics

Strontium fluorarsenate Sr5(AsO4)3F optical ceramics were fabricated for the first time by vacuum hot pressing of chemically precipitated powders. The properties of these ceramics were compared with those of the well-known strontium fluorophosphate Sr5(PO4)3F. According to BET, X-ray diffraction, and scanning electron microscopy, Sr5(AsO4)3F and Sr5(PO4)3F powders have an isomorphic single-phase structure and similar particle sizes of about 100–200 nm. The transmittances of 1.5 mm thick samples are as high as 89.5% and 85.8% in the mid-IR for Sr5(AsO4)3F and Sr5(PO4)3F, respectively. The Sr5(AsO4)3F ceramics have a wider mid-IR transmission range (up to 5.8 μm) than the Sr5(PO4)3F ceramics (up to 4.5 μm).

Glowing and flaming autoignition of wood exposed to coupled convective and radiative heating

Autoignition of solid fuels driven by coupled convective and radiative heating is frequently encountered in fires, whereas its controlling mechanism is rarely revealed. To challenge this issue, autoignition tests of 5 and 15 mm thick cylindrical wood samples were conducted using a newly developed apparatus enabling coupled convective and radiative heating. The total heat flux imposed on wood was maintained at 25 kW/m2, while the fractions of the two heating components changed as the airflow velocity and temperature varied in the ranges of 0–1.51 m/s and 298–473.3 K. Glowing ignition occurred in all scenarios except for one case due to enhanced heat loss and declined radiative heating. Flaming ignition was observed in all conditions except for 298 K airflow temperature. Four stages were identified during flaming combustion: a preheating and deformation stage, a glowing combustion stage, a coupled glowing and flaming combustion stage, and an extinction stage. Compared to 5 mm samples, the surface temperature rise of 15 mm wood was significantly delayed due to its thermally thick nature. By fitting experimental data, a new formula was proposed to correlate glowing ignition temperature with radiative heat flux, airflow velocity, and airflow temperature. Both glowing and flaming ignition times were affected by airflow and radiative heating in a complex manner, and their values to the power of −0.5 approximately linearly depended on radiative heat flux. Damköhler number and nondimensional heat loss ratio were employed to quantitively analyze the flaming ignition propensity. Meanwhile, an ignitability trend map identifying the flaming and non-flaming ignition regimes was drawn.

The influence of sample thickness on results of Mössbauer spectroscopy of ordinary chondrites and their classification

The influence of sample thickness on results of Mössbauer spectroscopy of ordinary chondrites and their classification

Influence of sample thickness and microstructure on metal dusting behavior of NiCrFeAl alloys

AbstractSamples of alloy 601, 602 CA and 602 MCA with different thickness and microstructure, all 600 grit laboratory ground, are compared. All samples are exposed to up to 5693 h at 600°C in a metal dusting producing atmosphere with a total pressure of 20 bar. A smaller sample thickness leads to an increased pit density for alloy 601 and an increased pit density, a longer incubation time and an increased pit depth growth rate for alloy 602 CA. This is attributed to lower stresses in the scale of the thinner samples. Grain size effects of the substrate are probably concealed by the deformed and recrystallized subsurface due to the 600 grit finish of the samples. If carbides are unavoidable in an alloy, they should be small, as they can serve as chromium suppliers during scale formation better than larger ones. They increase incubation time and pit depth growth rate.

Writing temperature and thickness dependence of perpendicular magnetic-dot magnetization reversal probability

Investigation is necessary to figure out magnetization dynamics at high temperatures due to the low power requirement for heat-assisted magnetic recording technology. The Landau-Lifshitz-Gilbert equation was employed to assess the dynamic of magnetization in perpendicular magnetic-dots at elevated temperatures, considering the thermal contribution to the effective field. The simulated perpendicular magnetic-dot has a 50×50 nm2 surface area with thicknesses of 10 nm, 50 nm, and 100 nm. This study reveals that the probability of magnetization reversal and the threshold field in the thermally-assisted magnetic reversal process of a magnetic dot is influenced by the thickness and writing temperature. Below the Curie point, as sample thickness increases, demagnetization energy increases, requiring a larger external magnetic field for magnetization reversal. For the thicker sample, the magnitude of the writing field decreases as the temperature increases, which corresponds to temperature-dependent magnetization. Meanwhile, the optimum writing field is obtained below the Curie point. The magnetic-dot with 100 nm of thickness has an effective writing temperature of 739.7 K with a corresponding writing field is 250 Oe while its reversal probability at zero magnetic field is up to 0.2. Magnetic-dot thickness affects magnetization reversal probability due to domain wall propagation mechanisms during magnetic switching that result from the demagnetization factor. Moreover, as the temperature approaches the Curie temperature, the probability of zero-field magnetization reversal in the absence of an external magnetic field is observed to escalate which has a direct impact on the writing field magnitude. It was found that the effective writing temperature is below the Curie temperature, which allows several hundred Oersted of the writing field.