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Preparation of Fe-Co-B-Si-Nb bulk metallic glasses by laser powder bed fusion: Microstructure and properties
摘要： In this work, laser powder bed fusion (LPBF) was employed for the preparation of {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 bulk metallic glasses (BMGs). Microstructural evolution, thermal stability and mechanical properties of LPBF-processed samples using different laser power and scanning speed were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), electron probe microscopy analysis (EPMA), electron backscatter diffraction (EBSD), differential scanning calorimetry (DSC) and nanoindentation. The results show that low area energy input facilitates the formation of Fe-Co-B-Si-Nb BMGs with a large amorphous fraction. LPBF-processed sample with an area energy density of 1.25 J/mm2 (at a laser power of 60 W and a scanning speed of 600 mm/s) exhibits a nearly fully glassy microstructure with an amorphous fraction of approximately 99%, meanwhile identical characteristic properties of LPBF-processed samples are correlated with the processing parameters during LPBF. This work demonstrates that LPBF is a promising method to prepare fully amorphous Fe-Co-B-Si-Nb BMGs. The results provide key insights for the fabrication of BMGs and BMGs composites with the desired microstructure possessing almost and properties by additive manufacturing.
关键词： Bulk metallic glasses,Laser powder bed fusion,Amorphous fraction,Crystallization,Microstructure,Nanoindentation
更新于2025-09-23 15:19:57
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A Study on Transparent Electrode Properties of Indium Tin Oxide Thin Films Deposited From Recycled Target
摘要： In this study, we investigated the transparent electrode and mechanical properties of indium tin oxide (ITO) thin ?lms deposited from recycled targets of In2O3 (90 wt %) and SnO3 (10 wt %). We also evaluated the effect of their heat treatment at different temperatures. The ITO thin ?lm deposited on the glass substrate at ambient temperature exhibited microcrystallization characteristics in which the amorphous state was incorporated. When the annealing temperature was over 200 (cid:1)C, the ITO thin ?lm showed stable transparent electrode characteristics with a sheet resistance value of 7.2 Ω/sq and high transmittance of more than 85% in the visible light region through recovery and recrystallization. Under compressive stress, the ITO thin ?lm exhibited stable elastic modulus and hardness values of more than 110 GPa and 6.0 GPa, respectively. It is anticipated that these outcomes will meet the electrical, optical, and mechanical property requirements for commercial ITO transparent electrodes.
关键词： Pulsed dc sputtering,ITO thin ?lm,Recycled target,Nanoindentation,Heat treatment
更新于2025-09-19 17:13:59
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Use of indentation to study the degradation of photovoltaic backsheets
摘要： The ability of electrical insulating materials within a module to act as insulators is a key safety requirement for photovoltaic (PV) technology. Presently, however, the durability of backsheets may not be readily assessed. For example, the mechanical tensile test continues to be developed, and its use has not been validated such that a technically based pass/fail criteria may be established. This study examines the use of simple indentation methods, including durometer hardness and instrumented indentation, as a means to quantitively assess the degradation of PV backsheets. Characteristics including: hardness, modulus, load/displacement pro?le, creep hold response, and residual impression are explored in an empirical study. Glass/encapsulant/backsheet mini-modules constructed using backsheets including: polyamide (speci?cally the AAA backsheet product), poly (ethylene terephthalate) (PET), polyvinyl ?uoride (PVF) laminate (“TPE”), and polyvinylidene ?uoride (PVDF) were examined. An M-type durometer as well as Berkovich and cube-corner tips were used in the indentation experiments. Additional characterizations were performed to interpret the indentation measurements including: surface roughness measurements using atomic force microscopy (AFM), a chemical structure study using Fourier-transform infrared spectroscopy (FTIR), and phase-transition measurements using di?erential scanning calorimetry (DSC). The results are analyzed in the context of the combined accelerated stress test (C-AST) also explored in this study. Instrumented indentation (i.e., using a Berkovich tip) was able to distinguish between backsheets and quantify the e?ects of accelerated testing (including up to 60%, 25%, and 20% change in hardness, modulus, and creep displacement, respectively). The embrittlement of the backsheets was not readily assessable using cube-corner indentation. Cracking of the known-bad polyamide backsheet was observed from the C-AST, which was not observed to result from steady state UV weathering.
关键词： Reliability,Backsheet,Durability,Nanoindentation,Instrumented indentation
更新于2025-09-12 10:27:22
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Interface Microstructure and Nanoindentation Characterization of Laser Offset Welded 5052 Aluminum to Press-Hardened Steel Using a Brass Interlayer
摘要： Laser o?set welding of 5052 aluminum to press-hardened steel using a brass interlayer was carried out. The cross-sectioned macrostructure and tensile strength were governed by varying the thickness of the brass interlayer. The maximum tensile strength reached 56.4 MPa when the thickness of brass interlayer was 0.05 mm. Subsequently, the interface microstructure, the nanoindentation characterization, and the fracture behavior were evaluated experimentally by means of scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDS), and micro-X-ray di?raction (micro-XRD), respectively. It was found that the intermetallic compound (IMC) layer at the interface consisted of an Fe2Al5 layer and an FeAl layer, and the estimated nanohardness of Fe2Al5, FeAl, and Fe3Al were 16.11 GPa, 9.48 GPa, and 4.13 GPa, respectively. The fracture of the joint with the 0.05 mm brass interlayer was a mixture of cleavage fracture and intergranular fracture, while that of the joint with the 0.1 mm brass interlayer exhibited the characterization of a major dendrite arm, leaving a metallurgical connected zone consisting of the Al2Cu and the α-Al phase.
关键词： laser o?set welding,aluminum,press-hardened steel,brass interlayer,nanoindentation,interface microstructure
更新于2025-09-11 14:15:04
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Mechanism Analysis of PCC Harmonic Resonance Based on Nonlinear Self-Oscillation Concept in a High-Power Grid-Tied Photovoltaic Plant
摘要： Polycrystalline materials can be divided into four types of microstructural components, including grain cell (GC), grain boundary (GB), triple junction (TJ) and vertex points (VP). Nanoindentation at different microstructural components on the polycrystalline materials surface can lead to different plastic deformation behaviors of the polycrystalline materials. Due to experimental limitations, the indentation-induced internal stress and defect evolution process are difficult to investigate directly, especially for the polycrystalline materials with grain size less than 100 nm. The molecular dynamics (MD) simulations were performed to unravel the initial indentation position effect on the elasticity/plastic deformation mechanism of polycrystalline copper. The results reveal that the initial indentation position governs the indentation force variation and defect distribution range due to the different dimensionalities of the microstructural components. The defect propagation as well as the internal stress transmission in the GC regions tend to transfer to the low-dimensional microstructural components of the interfaces. In addition, the atomic internal stress and potential energy accumulation/release of the microstructural component atoms during the nanoindentation process are also investigated, revealing that the atomic internal stress and potential energy in the VPs vary earliest, followed by the TJs, GBs and GCs.
关键词： microstructural component,initial indentation position,molecular dynamics,polycrystalline material,Nanoindentation
更新于2025-09-11 14:15:04
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Investigation on the phase transformation of monocrystalline silicon during nanoindentation at cryogenic temperature by molecular dynamics simulation
摘要： High-pressure phase transformation of silicon is an important phenomenon as it is of scientific and technological importance for semiconductor industry and micro/nano electromechanical system. However, there are limited studies on the phase transformation at cryogenic temperature. In this study, molecular dynamics simulation was conducted to investigate the nanoindentation of monocrystalline silicon at 1 K. The force-displacement curve and the corresponding phase transformation were studied in details. During the loading process, the contact zone was affected by the applied stress and the original diamond cubic structure of Si was distorted. With the increase of the depth, the distorted diamond cubic structure (DDS) was transformed into body-centered-tetragonal structure (bct-5) and Si-II. With the release of the force, the reverse transformations of Si-II to Si-III and Si-XII in junction with the pop-out events in the unloading curves can be clearly seen. It was also found that the phase distribution during the reverse transformation was strongly influenced by the indenter radius and indentation depth due to the different stress fields. At the higher depth, the unloading curves showed the unusual absence of pop-out and the appearance of surface extrusion. This can be ascribed by that the retained DDS outside the indentation after unloading not only restricts the transformation of Si-II but also brings the material extrusion on the surface due to the residual internal stress.
关键词： Pop-out,Nanoindentation,Silicon,Molecular dynamics,Extrusion
更新于2025-09-10 09:29:36
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Properties of ta-C coatings prepared by pulsed cathodic arc source at various distances
摘要： Tetrahedral amorphous carbon (ta-C) coatings have been prepared on silicon substrates by the pulsed cathodic arc source. For the limitation of the heat flux of the carbon plasma to the sample, the diaphragm of 27 mm diameter has been used. The deposition process has been carried out at three different distances between the arc source and the substrate: 150, 215 and 265 mm. The properties of ta-C coatings have been studied by Raman spectroscopy and dynamic nanoindentation techniques. The analysis of Raman spectra parameters has revealed that the concentration of ordered aromatic rings in Csp2 cluster decreases with distance between the arc source and the substrate while the concentration of chain groups increases. Nanoindentation has shown the decrease in nanohardness and Young's modulus with the distance. Nanohardness value falls from 21 GPa to 16 GPa and Young's modulus value goes down from 197 GPa to 177 GPa. So, it’s possible to control the formation of ta-C coatings structure by changing distance between the pulsed cathodic arc source and the substrate.
关键词： ta-C coatings,nanohardness,Young's modulus,pulsed cathodic arc source,nanoindentation,Raman spectroscopy
更新于2025-09-09 09:28:46
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Effect of precursor flow rate on physical and mechanical properties of a-C:H:SiO <sub/><i>x</i> </sub> films deposited by PACVD method
摘要： In this paper the deposition of a-C:H:SiOx films by plasma activated chemical vapour deposition in a mixture of argon and polyphenylmethylsiloxane (PPMS) vapor with the impulse bipolar bias voltage applied to the substrate is presented. The paper discusses the dependence of the physico-mechanical properties of the deposited films on the flow rate of the PPMS precursor. The structure of the deposited films was determined by Fourier transform infrared spectroscopy and Raman spectroscopy. Mechanical properties characterization of a-C:H:SiOx films (hardness and elastic modulus) was made using the nanoindentation method. Hardness and elastic modulus were used to evaluate the endurance capability (H/E) and resistance to plastic deformation (H3/E2). The elastic recovery was calculated based on loading and unloading curves. It is shown that with an increase in the PPMS flow rate in the range of 35-287 μl/min, the films deposition rate increases from 17 to 221 nm/min. At this films mechanical properties, such as hardness, elastic modulus and elastic recovery did not deteriorate. The maximum values of the endurance capability and resistance to plastic deformation are obtained at a flow rate of 175 μl/min and equal to 0.12 and 203 MPa, respectively.
关键词： PPMS,a-C:H:SiOx films,PACVD,mechanical properties,nanoindentation
更新于2025-09-09 09:28:46
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Evolution of microstructure and mechanical properties of a graded TiAlON thin film investigated by cross-sectional characterization techniques
摘要： In the last years, quaternary oxynitrides have emerged as a new class of materials due to their tunable properties. Within the present work, a graded TiAl(O)N film was grown by magnetron sputter deposition, using TiAl targets with a Ti/Al atomic ratio of 40/60, constant nitrogen and stepwise increasing oxygen partial pressure over the film thickness. The microstructural evolution of the film was investigated by transmission electron microscopy and synchrotron X-ray nanodiffraction. Complementary, cross-sectional μ-Raman spectroscopy was performed to further validate the phase evolution. The first layer, grown without the addition of oxygen, showed a prevalent wurtzite (w) structure and a subordinate face centered cubic (fcc) phase fraction. The addition of small amounts of oxygen resulted in the stabilization of the fcc-phase and the w-phase vanished. With increasing film thickness and thus, increasing oxygen content, increasing amounts of an additional amorphous phase fraction were observed. In the first layers, tensile in-plain strain was determined, which turns to compressive towards the film surface. Cross-sectional nanonindentation revealed increasing hardness and elastic modulus with increasing oxygen content in the first layers as a result of the w to fcc transition; however, towards the film surface the hardness decreases, which can be related to the increasing amorphous phase fraction.
关键词： sputtering,TiAlON,graded film,cross-sectional nanoindentation,synchrotron X-ray nanodiffraction,TEM
更新于2025-09-04 15:30:14
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Conformal Coating of Metallic Shells on Carbon Nanotube Turfs
摘要： A synthesis method to form conformal core-shell foams of metals and alloys on a carbon nanotube (CNT) scaffold by electroplating from a single bath electrolyte is demonstrated in this work. A triple cyclic pulse electrodeposition technique was used to deposit Ni and Cu layers on the CNT scaffold, and electron microscopy was then used to identify conditions amenable to conformal and island growth morphologies. Nanoindentation of the resulting metallic foam structure, using a flat punch/compression geometry, demonstrates that adding conformal metallic shells to the CNT turf to create a metal coated low density foam increases both the hardness and elastic modulus; however, once island growth initiates there is no significant subsequent increase in mechanical properties with increases in deposited metals.
关键词： Nanoindentation,Conformal coating,Electrodeposition,Mechanical properties,Carbon nanotube
更新于2025-09-04 15:30:14