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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Fill Factor Loss in Fielded Photovoltaic Modules Due to Metallization Failures, Characterized by Luminescence and Thermal Imaging
摘要： During irradiation UO2 nuclear fuel experiences the development of a non-uniform distribution of porosity which contributes to establish varying mechanical properties along the radius of the pellet. Radial variations of both porosity and elastic properties in high burnup UO2 pellet can be investigated via high frequency acoustic microscopy. For this purpose ultrasound waves are generated by a piezoelectric transducer and focused on the sample, after having travelled through a coupling liquid. The elastic properties of the material are related to the velocity of the generated Rayleigh surface wave (VR). A UO2 pellet with a burnup of 67 GWd/tU was characterized using the acoustic microscope installed in the hot cells of the JRC-ITU at a 90 MHz frequency, with methanol as coupling liquid. VR was measured at different radial positions. A good agreement was found, when comparing the porosity values obtained via acoustic microscopy with those determined using SEM image analysis, especially in the areas close to the centre. In addition, Young’s modulus was calculated and its radial pro?le was correlated to the corresponding burnup pro?le and to the hardness radial pro?le data obtained by Vickers micro-indentation
关键词： Nuclear fuels,piezoelectric devices,Vickers microhardness,Young’s modulus,nuclear power
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - In-situ Microscopy Characterization of Cu(In,Ga)Se <sub/>2</sub> Potential-Induced Degradation
摘要： During irradiation UO2 nuclear fuel experiences the development of a non-uniform distribution of porosity which contributes to establish varying mechanical properties along the radius of the pellet. Radial variations of both porosity and elastic properties in high burnup UO2 pellet can be investigated via high frequency acoustic microscopy. For this purpose ultrasound waves are generated by a piezoelectric transducer and focused on the sample, after having travelled through a coupling liquid. The elastic properties of the material are related to the velocity of the generated Rayleigh surface wave (VR). A UO2 pellet with a burnup of 67 GWd/tU was characterized using the acoustic microscope installed in the hot cells of the JRC-ITU at a 90 MHz frequency, with methanol as coupling liquid. VR was measured at different radial positions. A good agreement was found, when comparing the porosity values obtained via acoustic microscopy with those determined using SEM image analysis, especially in the areas close to the centre. In addition, Young’s modulus was calculated and its radial pro?le was correlated to the corresponding burnup pro?le and to the hardness radial pro?le data obtained by Vickers micro-indentation
关键词： Nuclear fuels,piezoelectric devices,Vickers microhardness,Young’s modulus,nuclear power
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Rough and Straightforward Estimation of the Mismatching Loss by Partial Shading of the PV Modules Installed on an Urban Area or Car-Roof
摘要： During irradiation UO2 nuclear fuel experiences the development of a non-uniform distribution of porosity which contributes to establish varying mechanical properties along the radius of the pellet. Radial variations of both porosity and elastic properties in high burnup UO2 pellet can be investigated via high frequency acoustic microscopy. For this purpose ultrasound waves are generated by a piezoelectric transducer and focused on the sample, after having travelled through a coupling liquid. The elastic properties of the material are related to the velocity of the generated Rayleigh surface wave (VR). A UO2 pellet with a burnup of 67 GWd/tU was characterized using the acoustic microscope installed in the hot cells of the JRC-ITU at a 90 MHz frequency, with methanol as coupling liquid. VR was measured at different radial positions. A good agreement was found, when comparing the porosity values obtained via acoustic microscopy with those determined using SEM image analysis, especially in the areas close to the centre. In addition, Young’s modulus was calculated and its radial pro?le was correlated to the corresponding burnup pro?le and to the hardness radial pro?le data obtained by Vickers micro-indentation
关键词： Nuclear fuels,piezoelectric devices,Vickers microhardness,Young’s modulus,nuclear power
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE International Ultrasonics Symposium (IUS) - Glasgow, United Kingdom (2019.10.6-2019.10.9)] 2019 IEEE International Ultrasonics Symposium (IUS) - Laser Ultrasonic Sensing of Oxidation-Induced Microstructural Changes in Nuclear Graphites
摘要： Serving both as a structural and as a functional material, nuclear graphites have a range of useful mechanical, chemical and radiation-related behaviors that are important for nuclear applications. The raw materials used as feedstock along with the manufacturing processes used for production of these materials results in a complicated microstructure composed of graphite filler, graphitized pitch binder, and voids/defects that include porosity and microcracks. These heavily influence the overall elastic moduli of nuclear graphites and must be taken into account when interpreting ultrasonic measurements. Indeed, the measured elastic moduli are generally close to the Reuss limits – the theoretical, lower bounds for the moduli – but no attempts have been made to explain these results within the broader context of elasticity in porous materials containing microcracks. In this work, we report ultrasonic measurements of elastic moduli for nuclear graphites as a function of the bulk porosity and interpret them using relatively simple, physics-based models that describe the effects of porosity and microcracking on modulus. Modifications to these models are explored to account for microstructure-related effects on modulus such as those that are associated with oxidation-induced porosity. These models can be used to interpret a broad range of ultrasonic measurements reported previously for nuclear graphites, and the insight gained into the elastic responses of these materials can be used to guide the use of ultrasonic methods to assess the structural integrity of nuclear graphites.
关键词： porosity,laser ultrasonics characterization,elastic modulus,material property
更新于2025-09-19 17:13:59
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Improvement of 2.79 um laser performance on the LD side-pumped GYSGG/Er,Pr:GYSGG bonding rod with concave end-faces
摘要： The melting of crystals is one of the commonest and most general phase transition phenomena, however, the mechanism of crystal melting is not understood enough, and more experimental measurements and explorations are still needed. The mechanical spectra of propylene carbonate and 1,3-propanediol during the crystal melting processes are measured by the reed vibration mechanical spectroscopy for liquids (RMS-L) for the first time. The experimental results show that, with the increasing temperature, the real part of complex Young modulus decreases slowly first, and then quickly drops to zero, meanwhile, its imaginary part increases slowly at first, then goes up and drops quickly to zero, showing a peak of internal friction. Preliminary analyses indicate that both the real and imaginary parts can present some characteristics of the melting process, such as the transition from the liquid regions disconnected to the connected, that from the crystal regions connected to the disconnected and so on. In addition, the results show that the melting rate per unit volume of crystalline phase versus temperature satisfies the Arrhenius relation at the initial stage of melting and deviates from this relation as the temperature increases to a certain value. Therefore, the RMS-L will provide an effective supplement for the further study of melting.
关键词： mechanical spectroscopy,percolation,complex Young modulus,crystal melting
更新于2025-09-19 17:13:59
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Ultrasound-assisted electrodeposition of Fe-Ni film for OLED mask
摘要： Fe-Ni alloy is considered as the most suitable metal for OLED mask making due to its excellent properties. However, electrodeposited Fe-Ni ?lm is often companied with poor surface quality and thermal expansion. To get proper ?lm for masks making, experiments of electroforming Fe–Ni were performed with di?erent ultrasonic powers and current densities. Results show that Fe-Ni ?lm with smooth surface could be electrodeposited at high current density due to the reducing of internal stress of ?lm by ultrasonic power. The iron content, grain size, micro-hardness and Young’s modulus of ?lm all present an upward trend with ultrasonic power increases from 13 W to 93 W, and then a downward trend due to the intensively transient cavitation caused by higher ultrasonic power 120 W. With the ultrasonic power of 93 W and current density of 1 A/dm2, a good surface quality of Fe-Ni ?lms with 60.07 wt.% iron content, microhardness 351 HV, Young's modulus 167.5 GPa and CTE 3.38 × 10?6/℃ can be electrodeposited.
关键词： Fe-Ni ?lm,Electroforming,Young's modulus,Ultrasonic power,Thermal expansion
更新于2025-09-19 17:13:59
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Fluorescence imaging analysis of depth‐dependent degradation in photovoltaic laminates: insights to the failure
摘要： Accurate evaluation of the reliability of photovoltaic (PV) packaging materials is critically important for the long‐term safe operation of modules. However, the complexity of the laminated systems due to their multilayered and multicomponent structures and diverse aging mechanisms makes a thorough system evaluation very challenging, especially when the degradation is non‐uniform through the thickness. In such a case, neither surface nor bulk measurements can present a clear picture of the degradation profile. In this study, fluorescence imaging was developed to visualize the degradation depth‐profiles of an aged laminated PV system. A glass/ethylene vinyl acetate (EVA) encapsulant/poly(ethylene terephthalate) (PET)‐PET‐EVA (PPE) backsheet laminate was weathered with the glass‐side facing an ultra-violet (UV) light source for 3840 h. Cross‐sectional fluorescence images revealed a non‐uniform distribution of degradation species across the thickness of the EVA encapsulant, providing greater insight into the mechanisms of degradation, which are unavailable by traditional bulk‐based methods. In addition, strong fluorescence emissions were observed from the two thin adhesive layers of the aged backsheet, indicating severe degradation of the adhesives and a potential for interlayer delamination. This method is further confirmed with other microscale characterization techniques. The changes in optical (yellowness index), chemical (oxidation, UV absorber concentration), mechanical (Derjaguin‐Muller‐Toporov modulus), and thermal (melting enthalpy) properties of the EVA encapsulant were found to be related to fluorescence profiles, following the attenuation of UV light. This study highlights that fluorescence imaging is a spatially‐resolved and sensitive method for rapid failure assessment and in‐depth mechanism study for complex PV‐laminated system.
关键词： modulus,depth profile,UV aging,photovoltaic laminates,yellowness index,fluorescence imaging,degradation
更新于2025-09-16 10:30:52
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Stiffness and hardness gradients obtained by laser surface melting of an aged β-Ti alloy
摘要： Components with variable stiffness have been attracting interest because of their potential for use in biomedical implants. Here, a β-titanium alloy aged under different conditions was subjected to laser surface melting (LSM). The high cooling rate typical of LSM avoided α-phase precipitation in the fusion zone (FZ) and heat-affected zone (HAZ) as the α precipitates were solid-solutioned into the β phase, producing a surface layer with full β phase over the aged substrate and reduced stiffness and hardness. The decrease in stiffness occurred independently of the aging condition used while the decrease in hardness was greater for the sample aged at the lower temperature as this had finer precipitates. A route involving aging at this lower temperature and LSM is proposed for use when a graded material combining a less rigid surface with the original core stiffness and strength is required, as in orthopedic implants.
关键词： Laser processing,Graded materials,Elastic modulus,Titanium alloys
更新于2025-09-12 10:27:22
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Fixed-Path Length Laser-Induced Sound Pinging: A Streamlined Method for Sound Speed Determination in Arbitrary Liquids
摘要： Recently, we introduced laser-induced sound pinging (LISP) as a simple photoacoustic technique for the expedient and fairly rapid (2?3 min) measurement of the speed of sound traversing low-volume samples (25?1000 μL), built around an inexpensive tattoo-removal source (Sens. Actuators B-Chem. 2019, 291, 401?410). In this report, we expand on the utility of this technique by improving the facility of measurement and speed of analysis by adopting a ?xed-path length (FPL) architecture which allows for much faster analysis (1?5 s) of similar sample volumes. The FPL-LISP setup was employed to determine the speeds of sound at temperatures from 293 to 333 K for four popular hydrophilic deep eutectic solvents (DESs) containing choline chloride (i.e., reline, ethaline, glyceline, and maline), plus several representative decanoic acid?based (i.e., hydrophobic) DESs. The temperature-dependent speeds of sound were used alongside the corresponding experimental densities to calculate the bulk modulus for these illustrative DESs. Interestingly, the bulk modulus was in the 4000?5000 MPa range for choline chloride-derived DESs, essentially twice the value of a hydrophobic DES (typi?ed by 1:2 tetraoctylammonium bromide/decanoic acid), suggesting unique potential for hydraulic applications, for example. The modest volume requirements of FPL-LISP make it suitable for determining the speed of sound in scarce, precious, or hazardous liquids, and the speed of analysis enables integration into a continuous-?ow platform for real-time analytics (e.g., beverage quality control).
关键词： bulk modulus,speed of sound,laser-induced sound pinging,photoacoustic technique,deep eutectic solvents
更新于2025-09-12 10:27:22
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Characterizing the Complex Modulus of Asphalt Concrete Using a Scanning Laser Doppler Vibrometer
摘要： Asphalt mixtures are the most common types of pavement material used in the world. Characterizing the mechanical behavior of these complex materials is essential in durable, cost-effective, and sustainable pavement design. One of the important properties of asphalt mixtures is the complex modulus of elasticity. This parameter can be determined using different standardized methods, which are often expensive, complex to perform, and sensitive to the experimental setup. Therefore, recently, there has been considerable interest in developing new, easier, and more comprehensive techniques to investigate the mechanical properties of asphalt. The main objective of this research is to develop an alternative method based on an optical measurement technique (laser Doppler vibrometry). To do this, a frequency domain system identification technique based on analytical formulas (Timoshenko’s beam theory) is used to determine the complex modulus of asphalt concrete at its natural frequencies and to form their master curve. The master curve plotted by this method is compared with the master curve obtained from the standard four-point bending test, and it is concluded that the proposed method is able to produce a master curve similar to the master curve of the standard method. Therefore, the proposed method has the potential to replace the standard stiffness tests. Furthermore, the standard stiffness methods usually conduct experiments up to the maximum frequency of 30 Hz. However, the proposed method can provide accurate complex modulus at high frequencies. This makes an accurate comparison between the properties of the asphalt mixtures in high frequencies and the development of more accurate theoretical models for simulation of specimens possible.
关键词： laser Doppler vibrometry,asphalt mixtures,modal analysis,complex modulus,master curve,non-destructive testing
更新于2025-09-11 14:15:04