Sample Thickness Research Articles

Assessment of submicron bone tissue composition in plastic-embedded samples using optical photothermal infrared (O-PTIR) spectral imaging and machine learning

Understanding the composition of bone tissue at the submicron level is crucial to elucidate factors contributing to bone disease and fragility. Here, we introduce a novel approach utilizing optical photothermal infrared (O-PTIR) spectroscopy and imaging coupled with machine learning analysis to assess bone tissue composition at 500 nm spatial resolution. This approach was used to evaluate thick bone samples embedded in typical poly(methyl methacrylate) (PMMA) blocks, eliminating the need for cumbersome thin sectioning. We demonstrate the utility of O-PTIR imaging to assess the distribution of bone tissue mineral and protein, as well as to explore the structure-composition relationship surrounding microporosity at a spatial resolution unattainable by conventional infrared imaging modalities. Using bone samples from wildtype (WT) mice and from a mouse model of osteogenesis imperfecta (OIM), we further showcase the application of O-PTIR spectroscopy to quantify mineral content, crystallinity, and carbonate content in spatially defined regions across the cortical bone. Notably, we show that machine learning analysis using support vector machine (SVM) was successful in identifying bone phenotypes (typical in WT, fragile in OIM) based on input of spectral data, with over 86% of samples correctly identified when using the collagen spectral range. Our findings highlight the potential of O-PTIR spectroscopy and imaging as valuable tools for exploring bone submicron composition.

Analysis of Structure, Morphology, Magnetic Properties, and Microwave Absorption of Lanthanum Orthoferrite (LaFeO3)

LaFeO3 has been prepared using the solid-state reaction method with High Energy Milling (HEM). The preparation of LaFeO3 was carried out using stoichiometric calculations. Based on the XRD measurement results, single-phase LaFeO3 with an orthorhombic crystal structure was obtained. From the SEM results, the morphology of LaFeO3 is uniform, and the EDS results show the weight percentage of La, Fe, and O elements are 49.74, 21.08, and 29.18 wt%, respectively. VSM LaFeO3 results show magnetic saturation, remanence, and coercivity are 0.24 emu/g, 0.02 emu/g, and 853.38 Oe, respectively, and the absorption of LaFeO3 is -7.40 dB at a frequency of 6.02 GHz with a LaFeO3 sample thickness of 1.5mm.

Investigation of thermal diffusivity measurement technique based on photoacoustic signal response under the influence of three-dimesional heat transfer

In this study, we investigated the feasibility of measuring the thermal diffusivity of thermally thick solid material using the photoacoustic (PA) signal response in a three-dimensional heat diffusion state. For this purpose, we developed a heat conduction simulation model based on cylindrical coordinates to replicate the PA effect on three-dimensional heat diffusion. By numerical analysis, it was found that the phase of PA signal deviates from one-dimensional theory prediction when the lateral heat diffusion of the solid sample reaches the chamber wall of PA cell. Specifically, it was found that the phase lag inflects at the frequency where the sample’s thermal diffusion length μs is 0.91 mm at a chamber radius of 3 mm. By utilizing this correlation, the infection frequency can potentially provide the thermal diffusivity of the thermally thick sample. The experimental validation qualitatively confirmed that the phenomena observed in the numerical analysis occur in practice. However, quantitatively, the experimental results showed discrepancies from the numerical analysis, which is likely due to the influence of the radial distribution of laser intensity. Nonetheless, this issue can be resolved in practical applications through calibration using a reference sample. Numerical analysis suggested that for materials with thermal diffusivity lower than that of air, measuring thermal diffusivity could be seemingly impossible. However, the experimental results demonstrated that calibration with a reference sample having sufficiently lower thermal diffusivity than that of air effectively compensates for the influence of air’s thermal diffusion. The significant factor affecting the accuracy of thermal diffusivity determination with the proposed method is identifying the inflection frequency. It will be necessary to explore an appropriate method for determining the frequency by integrating multiple sources of information, such as simultaneously observing the amplitude of the PA signal.

Collapse of metallicity and high-Tc superconductivity in the high-pressure phase of FeSe0.89S0.11

We investigate the high-pressure phase of the iron-based superconductor FeSe0.89S0.11 using transport and tunnel diode oscillator studies using diamond anvil cells. We construct detailed pressure-temperature phase diagrams that indicate that the superconducting critical temperature is strongly enhanced by more than a factor of four towards 40 K above 4 GPa. The resistivity data reveal signatures of a fan-like structure of non-Fermi liquid behaviour which could indicate the existence of a putative quantum critical point buried underneath the superconducting dome around 4.3 GPa. With further increasing the pressure, the zero-field electrical resistivity develops a non-metallic temperature dependence and the superconducting transition broadens significantly. Eventually, the system fails to reach a fully zero-resistance state, and the finite resistance at low temperatures becomes strongly current-dependent. Our results suggest that the high-pressure, high-Tc phase of iron chalcogenides is very fragile and sensitive to uniaxial effects of the pressure medium, cell design and sample thickness. This high-pressure region could be understood assuming a real-space phase separation caused by nearly concomitant electronic and structural instabilities.

The Influence of Ag Addition and Different SiO2 Precursors on the Structure of Silica Thin Films Synthesized by the Sol-Gel Method.

In this work, the structure of silica thin films synthesized with three different SiO2 precursors and obtained by the sol-gel method and dip coating technique was studied. Additionally, the influence of Ag addition on the obtained silica sols and then gel structure was investigated. Silica coatings show antireflective properties and high thermal resistance, as well as hydrophobic or hydrophilic properties. Three different silica precursors, TEOS (tetraethylorthosilicate), DDS (dimethyldietoxysilane) and AerosilTM, were selected for the synthesis. DDS added to silica sol act as a pore size modifier, while Ag atoms are known for their antibacterial activity. Coatings were deposited on two different substrates: steel and titanium, dried and annealed at 500 °C in air (steel substrate) and in argon (titanium substrate). For all synthesized films, IR (infrared) spectroscopic studies were performed together with GID and XRD (Grazing Incidence Diffraction, X-ray Diffraction) measurements. The topography and morphology of the surface were traced by SEM and AFM microscopic methods, providing information on the samples' roughness, particle sizes and thickness of the particular layers. The wetting angle values were also measured. GID and XRD measurements pointed to the distinct contribution of an amorphous phase in the samples, allowing us to recognize the crystalline phases and calculate the silver crystallite sizes. The FTIR spectra gave information on the first coordination sphere of the studied samples.

Improved densification of SiCf/SiC composites by microwave-assisted chemical vapor infiltration process based on multifrequency solid-state sources excitation

This paper addresses the possibility of improving and controlling the temperature profile of a Ceramic Matrix Composite preform in a multiport Microwave-assisted Chemical Vapor Infiltration (MW-CVI) pilot-scale plant, based on a multifrequency excitation of the reactor by three solid-state sources. The choice of the most suited excitation frequencies is guided by rigorous numerical modeling of the reactor loaded by the sample, solving the coupled electromagnetic and thermal problems in a self-consistent way. The resulting infiltration front and residual porosity have been evaluated by a pseudo1D model, along the sample thickness, according to the previously computed heating pattern. The practical implementation and validation of the proposed technique are illustrated with MW-CVI trials on 10×10×0.3 cm3 SiCf/(SiC/BN)3/SiC preforms manufactured by Filament Winding method. The obtained results confirm the inside-out densification pattern, expected from the sample volumetric heating, along with an extension of the densification region by a factor of 2–3.

Study of Factors Affecting UV-Induced Photo-Degradation in Different Types of Polyethylene Sheets.

Enhancing the degradability of polyethylene plastics could provide a potential solution to the overwhelming crisis of plastic waste. Conventional studies have focused on the degradation of polyethylene thin films. This study investigated UV-induced photo-degradation according to ASTM D5208-14 in polyethylene sheets with thicknesses ranging from 0.4 to 1.2 mm. The impacts of sample thickness, metal pro-oxidants, polyethylene resin types and foaming were explored through the characterization of the carbonyl index, molecular weight, tensile properties and crystallinity. As pro-oxidants, single iron or manganese stearate demonstrated a concentration-dependent trend in accelerating the photo-degradation of polyethylene sheets. The thickness, foaming and resin type-such as low-density polyethylene (LDPE) and high-density polyethylene (HDPE)-significantly impacted the rate of photo-oxidation. Thick polyethylene sheets (1.2 mm) exhibited a heterogenous and depth-dependent degradation profile. As the photo-degradation progressed, the enhanced crystallinity, reduced UV transmittance and formation of crosslinks were able to prevent further oxidative cleavage of the polyethylene chain. This study investigated the time course and factors affecting the photo-degradation of polyethylene sheets, which could provide insights into the formulation design of photo-degradable polyethylene plastics.

Evaluating the Use of Predicted Cushion Curves for Comparing the Performance of Some Sustainable Cushion Systems

ABSTRACTThis paper studies the cushion performance of a range of sustainable cushion systems and applies two methods to estimate cushion curves from limited cushion test data. The methods employed were previously developed to allow for (1) the conversion of cushion curves representing a material's performance for a given drop height and sample thickness to alternative (non‐measured) drop heights and sample thicknesses and (2) generating a complete cushion curve for a given thickness and drop height from a single acceleration (shock) measurement. The results include those generated for medium‐density polyethylene (MDP) closed‐cell foam for benchmarking of the materials and to aid in validating the approach. The results indicate that predicting cushion curves from single shock measurements is generally accurate for polymeric materials (MDP closed‐sell foam and HDPE inflated bag) but much less so for organic materials (sugarcane bagasse and perforated cardboard). Finally, all alternative cushioning materials and systems evaluated are shown to only be effective for very low static stresses. This finding demonstrates that much higher volumes are required when using the alternative materials to achieve the same cushioning effectiveness as MPD foam.

EBSD and TKD analyses using inverted contrast Kikuchi diffraction patterns and alternative measurement geometries

Electron backscatter diffraction (EBSD) patterns can exhibit Kikuchi bands with inverted contrast due to anomalous absorption. This can be observed, for example, on samples with nanoscale topography, in case of a low tilt backscattering geometry, or for transmission Kikuchi diffraction (TKD) on thicker samples. Three examples are discussed where contrast-inverted physics-based simulated master patterns have been applied to find the correct crystal orientation. As first EBSD example, self-assembled gold nanostructures made of Au fcc and Au hcp phases on single-crystal germanium were investigated. Gold covered about 12% of the mapped area, with only two thirds being successfully interpreted using standard Hough-based indexing. The remaining third was solved by brute force indexing using a contrast-inverted master pattern. The second EBSD example deals with maps collected at a non-tilted surface instead of the commonly used 70° tilted one. As TKD example, a jet-polished foil made of duplex stainless steel 2205 was examined. The thin part close to the hole edge producing normal-contrast patterns were standard indexed. The areas of the foil that become thicker with increasing distance from the edge of the hole produce contrast-inverted patterns. They covered three times the evaluable area and were successfully processed using the contrast-inverted master pattern. In the last example, inverted patterns collected at a non-tiled sample were mathematically inverted to normal contrast, and Hough/Radon-based indexing was successfully applied.

Effect of Proton Irradiation on Thin-Film YBa2Cu3O7-δ Superconductor.

We investigated the effect of 0.6 MeV proton irradiation on the superconducting and normal-state properties of thin-film YBa2Cu3O7-δ superconductors. A thin-film YBCO superconductor (≈567 nm thick) was subject to a series of proton irradiations with a total fluence of 7.6×1016 p/cm2. Upon irradiation, Tc was drastically decreased from 89.3 K towards zero with a corresponding increase in the normal-state resistivity above Tc. This increase in resistivity, which indicates an increase in defects inside the thin-film sample, can be converted to the dimensionless scattering rate. We found that the relation between Tc and the dimensionless scattering rate obtained during proton irradiation approximates the generalized d-wave Abrikosov-Gor'kov theory better than the previous results obtained from electron irradiations. This is an unexpected result, since the electron irradiation is known to be most effective to suppress superconductivity over other heavier ion irradiations such as proton irradiation. In comparison with the previous irradiation studies, we found that the result can be explained by two facts. First, the dominant defects created by 0.6 MeV protons can be point-like when the implantation depth is much longer than the sample thickness. Second, the presence of defects on all element sites is important to effectively suppress Tc.

Tailored directional porosity in ceramic matrix composites (CMCs) for hypersonic applications

AbstractIn the field of hypersonic systems and their missions, the occurring flows impose extreme mechanical and thermal loads on the materials used. At the German Aerospace Center (DLR), extensive research is conducted in this area, ranging from design and specification to the development of suitable materials concluding with the proof of concept under realistic conditions in wind tunnels. In recent years, ceramic matrix composites (CMCs) have been investigated for specific aspects of hypersonics. These materials exhibit consistent mechanical behavior over a wide temperature range (up to 1600 °C), coupled with high damage tolerance and thermal shock resistance, distinguishing them from metals and superalloys. Particularly, special porous C/C–SiC ceramics (carbon-fiber-reinforced carbon with silicon carbide) enable innovative material applications for components in transpiration cooling, fuel injection, or boundary-layer transition control. The work presented focuses on the next generation of porous C/C–SiC ceramics currently in development. By deliberately modifying the textile preform, the resulting microstructure and pore morphology are influenced, allowing for control over both the total volume and the orientation of the pores. Relevant parameters influencing porosity have been determined based on the results, and an initial characterization has been conducted. It has been demonstrated that there is a preferred direction of porosity within the sample thickness (Z-axis), and in terms of hypersonic-relevant properties, an absorption coefficient of 0.58 for an acoustic wave at 500 kHz (static pressure of 15 kPa), as well as a length-specific flow resistance of 3.4 MPa s/m2 and an overall porosity of 12.25% were determined. Building upon these promising initial findings, the goal is to further expand the understanding of the parameters influencing porosity and to generate a tailored material for different application scenarios by correlating them with hypersonic properties.

Assessing the electromagnetic shielding effectiveness of coconut coir composites with varying iron particle concentrations

This study investigates the electromagnetic shielding effectiveness of Coconut Coir-based Porous Carbon (CCPC) composites with varying iron (Fe) particle concentrations, specifically focusing on four different weight ratios of CCPC/Fe-80, CCPC/Fe-60, CCPC/Fe-40, and CCPC/Fe-20. The novelty of this work lies in the use of sustainable coconut coir as a base material, emphasizing its eco-friendly and cost-effective attributes for Electromagnetic interference (EMI) shielding applications. The significance of varying iron particle concentrations is highlighted to optimize electromagnetic shielding effectiveness. Comprehensive analyses were conducted on these composites. X-Ray Diffraction (XRD) analysis confirmed the presence of crystalline Fe particles and amorphous carbon, with crystalline sizes determined via Williamson-Hall (W-H) plot, Scherrer Equation, and Strain Size Plot (SSP) ranging from 17.33 nm to 18.01 nm for the former. Raman spectroscopy revealed distinctive D and G bands, with intensity ratios indicating a slight increase in structural disorder with higher Fe content. UV-Visualization spectroscopy demonstrated distinct absorption peaks, with higher Fe content resulting in more pronounced absorbance and lower band gap energies. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analyses provided detailed insights into the material's microstructure and elemental composition, confirming the successful integration of Fe particles within the porous carbon matrix. Vector Network Analyzer (VNA) testing measured the reflection loss (RL), showing values in the range of −26.4 dB to −20.2 dB, for 2 mm thick samples, corresponding to electromagnetic wave attenuation of over 99%. These results underscore the potential of CCPC/Fe composites, particularly in applications requiring effective Electromagnetic (EM) wave attenuation. This research offers a sustainable and cost-effective solution, contributing significantly to the field of materials science by enhancing electromagnetic compatibility in various technological applications.

High Refractive Index Imaging Buffer for Dual-Color 3D SMLM Imaging of Thick Samples.

The current limitations of single-molecule localization microscopy (SMLM) in deep tissue imaging, primarily due to depth-dependent aberrations caused by refractive index (RI) mismatch, present a significant challenge in achieving high-resolution images at greater depths. To extend the imaging depth, we optimized the imaging buffer of SMLM with the RI matched to that of the objective immersion medium and systematically evaluated five different RI-matched buffers, focusing on their impact on the blinking behavior of red-absorbing dyes and the quality of reconstructed super-resolution images. Particularly, we found that clear unobstructed brain imaging cocktails-based imaging buffer could match the RI of oil and was able to clear the tissue samples. With the help of the RI-matched imaging buffers, we showed high-quality dual-color 3D SMLM images with imaging depths ranging from a few micrometers to tens of micrometers in both cultured cells and sectioned tissue samples. This advancement offers a practical and accessible method for high-resolution imaging at greater depths without the need for specialized optical equipment or expertise.

Unsupervised machine learning and cepstral analysis with 4D-STEM for characterizing complex microstructures of metallic alloys

Four-dimensional scanning transmission electron microscopy, coupled with a wide array of data analytics, has unveiled new insights into complex materials. Here, we introduce a straightforward unsupervised machine learning approach that entails dimensionality reduction and clustering with minimal hyperparameter tuning to semi-automatically identify unique coexisting structures in metallic alloys. Applying cepstral transformation to the original diffraction dataset improves this process by effectively isolating phase information from potential signal ambiguity caused by sample tilt and thickness variations, commonly observed in electron diffraction patterns. In a case study of a NiTiHfAl shape memory alloy, conventional scanning transmission electron microscopy imaging struggles to accurately identify a low-contrast precipitate at lower magnifications, posing challenges for microscale analyses. We find that our method efficiently separates multiple coherent structures while using objective means of determining hyperparameters. Furthermore, we demonstrate how the clustering result facilitates more robust strain mapping to provide immediate and quantitative structural insights.

Validation of Hole-Drilling Residual Stress Measurements in Workpieces of Various Thickness

BackgroundA recent revision to the ASTM E837 standard for near-surface residual stress measurement by the hole-drilling method describes a new thickness-dependent stress calculation procedure applicable to “thin” and “intermediate” workpieces for which strain versus depth response depends on workpiece thickness. This new calculation procedure differs from that of the prior standard, which applies only to thick workpieces with strain versus depth response independent of thickness.ObjectiveHerein we assess the new calculation procedures by performing hole-drilling residual stress measurements in samples with a range of thickness.MethodsNear-surface residual stress is measured in a thick aluminum plate containing near-surface residual stress from a uniform shot peening treatment, and in samples of different thickness removed from the plate at the peened surface. A finite element (FE) model is used to assess consistency between measured residual stress across the range of sample thickness.ResultsMeasured residual stress varies with sample thickness, with thinner samples exhibiting smaller near-surface compressive stress and a larger gradient of subsurface stress. These trends are consistent with both observed bending (curvature) of the removed samples and the trend in FE-calculated expected residual stress. The measured and expected residual stresses are in good agreement for samples of intermediate thickness, but the agreement decreases with sample thickness. Measured residual stress is invariant with gage circle diameter.ConclusionThe new thickness-dependent stress calculation procedure for hole-drilling provides meaningful improvement compared to thick-workpiece calculations.

Towards high-strength electrolyte-supported solid oxide fuel cells

The functionality and structural reliability of electrolyte-supported solid oxide fuel cells depend crucially upon the load-bearing capability of the ceramic electrolyte. In this work, the effect of thickness on the mechanical strength of tape-casted 8 mol% yttria-stabilized zirconia electrolyte discs was investigated. Samples with 98 % relative density and 2–3 µm grain size fabricated with thicknesses between 75 µm and 360 µm were mechanically tested using an adapted biaxial bending test. Thin electrolytes with biaxial strength up to 1 GPa could be produced. The measured characteristic strengths ranged from σ0 = 940 MPa to σ0 = 520 MPa for thin and thick samples, respectively, yielding a common Weibull modulus of m = 6. A higher strength scaled with decreasing thickness, confirming the “size effect” as in many technical ceramics. The measured ionic conductivity was above 0.1 S/cm at 1000 °C, which is in good agreement with commercial or conventionally prepared electrolytes.

Prospect for detecting magnetism in two-dimensional perovskite oxides by electron magnetic circular dichroism

Two-dimensional (2D) magnets, especially strongly correlated 2D transition-metal perovskite oxides, have attracted significant attention due to their intriguing electromagnetic properties for potential applications in spintronic devices. Potentially electron magnetic circular dichroism (EMCD) under zone axis conditions can provide three-dimensional components of magnetic moments in 2D materials, but the collection efficiency and the signal-to-noise ratio for out-of-plane (OOP) components is limited due to the limited collection angle. Here we conducted a comprehensive computational simulation to optimize the experimental setting of EMCD for detecting the OOP components of magnetic moments in three beam conditions (3BCs) on 2D perovskite oxides La1-xSrxMnO3 (LSMO) in a TEM. The key parameters are sample thickness, accelerating voltage, Sr doping concentration, collection semi-angle and position, and sample orientation including systematic reflections excited and tilt angle. Our simulation results demonstrate that the relative dynamical diffraction coefficients of Mn OOP EMCD of LaMnO3 with a thickness ranging from 1 unit cell (uc) to 4 uc can be optimized in a 3BC with (110) systematic reflections excited and a relatively large collection semi-angle of 19 mrad at the relatively low accelerating voltage of 80 kV. In most cases, the relative dynamic diffraction coefficients for La1-xSrxMnO3 with the thickness ranging from 1 uc to 4 uc decrease with the increase of the Sr doping concentrations. The optimal tilt angle from a zone axis to a 3BC is 18° for the cases of the LSMO thickness of 2 uc, 3 uc and 4 uc, and 22° for the monolayer LSMO. Our work provides the theoretical simulation foundation for optimized EMCD experiments for measuring OOP components of magnetic moments in 2D transition-metal perovskite oxides.

Organic compounds as temperature calibrants for fast scanning calorimetry

Organic compounds can be used as temperature calibrants in fast scanning calorimetry. Their advantages include ease of surface cleaning of the calorimetric chip and good thermal contact with the chip surface. Among several compounds tested, benzoic acid was identified as a convenient and reliable calibrant for temperatures below approximately 130 °C. However, organic calibrants often exhibit unusual heating rate dependencies of the onset temperatures of melting. This phenomenon can be semi-quantitatively explained by considering different heat flows within the sensor. Notably, the thermal resistance between the heater and thermopile, often overlooked, introduces an additional time constant that can sometimes result in a negative apparent thermal lag. In addition, the onset temperatures are influenced by factors such as sample position, thickness, surface wetting, and spreading. These factors limit the accuracy of transition temperature determinations to approximately ±1 K below 130 °C and ±5 K up to 220 °C.

Facile constructing core-shell F–CIP@O/N-SWCNHs composites for high-performance microwave absorption and anti-corrosion

The development of electromagnetic wave-absorbing materials (EWAMs) with good environmental adaptability has emerged as a focal point of research in the realm of electromagnetic protection. Herein, a core-shell structure composite EWAMs, in which flake carbonyl iron powders and O, N co-doped single-walled carbon nanohorns are respectively a core and a shell (F–CIP@O/N-SWCNHs), has been prepared by a simple electrostatic adsorption method. The high-shape anisotropy of the F–CIP core exhibits strong specific saturation magnetization (160.47 emu/g) and excellent magnetic loss capacity. The tunable O/N-SWCNHs shell effectively enhances the dielectric properties and improves impedance matching, while the oxygen and nitrogen doping strengthens the dipole polarization. The surface protection provided by O/N-SWCNHs imparts favorable corrosion resistance and anti-oxidation properties to the F-CIP@O/N-SWCNHs. Moreover, F–CIP@O/N-SWCNHs exhibit excellent wave absorption performance. When the sample thickness is 1.53 mm, the minimum reflection loss reaches −74.8 dB. This study provides a feasible approach for the preparation of efficient EWAMs with strong environmental adaptability for the practical application of composite-absorbing materials.

Bridgman growth and luminescence properties of Na2Mo2O7 crystal

This research presents a Bridgman method for the crystal growth of disodium dimolybdate (Na2Mo2O7, NM2O) crystals and understanding their luminescence mechanism. An NM2O crystal with a size of 23 * 23 * 90 mm3 was grown using the vertical Bridgman method. The cleavage of the NM2O crystal was analyzed by X-ray diffraction and scanning electron microscopy, which showed that the crystal cleaves along the (001) plane and the cleavage planes appear in a step pattern. Its luminescence properties were studied using transmission spectra and laser-stimulated luminescence spectra, which showed that the transmittance of a 5 mm thick sample reaches 85 % in the range of 500–700 nm with the absorption cutoff edge at 360 nm, resulting in the optical band gap of 3.35 eV. Under excitation of a 278 nm laser beam, the sample exhibited dual-peak emission, typically at around 598 nm and 673 nm, consistent with radioactive annihilation of the self-trapped exciton on [MoO6]6− and [MoO4]2− groups respectively. Also the luminescence at low temperatures were measured and discussed. All results can benefit the crystal growth and application to the 0νββ experiments for the functional material.