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3 pages, 194 KiB

Open AccessEditorial

Micro Non-Destructive Testing and Evaluation

by Giovanni Bruno

Materials 2022, 15(17), 5923; https://doi.org/10.3390/ma15175923 - 27 Aug 2022

Cited by 1 | Viewed by 1296

Abstract

What is meant by ‘Micro Non-Destructive Testing and Evaluation’ [...] Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

Research

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12 pages, 4595 KiB

Open AccessArticle

Magnetic Investigation of Cladded Nuclear Reactor Blocks

by Gábor Vértesy, Antal Gasparics, Ildikó Szenthe and Sándor Bilicz

Materials 2022, 15(4), 1425; https://doi.org/10.3390/ma15041425 - 15 Feb 2022

Cited by 2 | Viewed by 1442

Abstract

The wall, made of ferromagnetic steel, of a nuclear reactor pressure vessel is covered by an austenitic (very weakly ferromagnetic) cladding. In this work, we investigated how the base material and the cladding can be inspected separately from each other by nondestructive magnetic [...] Read more.

The wall, made of ferromagnetic steel, of a nuclear reactor pressure vessel is covered by an austenitic (very weakly ferromagnetic) cladding. In this work, we investigated how the base material and the cladding can be inspected separately from each other by nondestructive magnetic measurements. It was found that with the proper choice of the magnetizing yoke, these two different materials could be measured independently of each other. The effect of the yoke’s size was studied by the numerical simulation of magnetic flux, pumped into the material during magnetic measurements. Measurements were performed by two different sizes of yokes on pure base material, on base material under cladding and on cladding itself. Experiments verified the results of the simulation. Our results can help for the future practical application of magnetic methods in the regular inspection of nuclear power plants. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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26 pages, 9940 KiB

Open AccessArticle

Impact of Magnetization on the Evaluation of Reinforced Concrete Structures Using DC Magnetic Methods

by Paweł Karol Frankowski and Tomasz Chady

Materials 2022, 15(3), 857; https://doi.org/10.3390/ma15030857 - 23 Jan 2022

Cited by 9 | Viewed by 3276

Abstract

The magnetic method is the most promising method that can be used to inspect large areas of reinforced concrete (RC) structures. Magnetization is a crucial process in this method. The paper aims to present the impact of the magnetization method on the results [...] Read more.

The magnetic method is the most promising method that can be used to inspect large areas of reinforced concrete (RC) structures. Magnetization is a crucial process in this method. The paper aims to present the impact of the magnetization method on the results in the detection of reinforced bars (rebars) and the evaluation of concrete cover thickness in reinforced concrete (RC) structures. Three cases (without magnetization, same pole magnetization, and opposite pole magnetization) were considered in the experiments. Results achieved in all the methods are presented and evaluated. Two different sensing elements were used in the measurements: a magneto-optical (MO) sensor and an AMR sensor. The advantages and disadvantages of both mentioned transducers are presented and discussed in the context of a large areas inspection. The new approach involves using various magnetization methods to improve measurement results for complex structures. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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15 pages, 7138 KiB

Open AccessArticle

Magnetic Recording Method (MRM) for Nondestructive Evaluation of Ferromagnetic Materials

by Tomasz Chady, Ryszard D. Łukaszuk, Krzysztof Gorący and Marek J. Żwir

Materials 2022, 15(2), 630; https://doi.org/10.3390/ma15020630 - 14 Jan 2022

Cited by 7 | Viewed by 2574

Abstract

This paper proposes and experimentally investigates a novel nondestructive testing method for ferromagnetic elements monitoring, the Magnetic Recording Method (MRM). In this method, the inspected element must be magnetized in a strictly defined manner before operation. This can be achieved using an array [...] Read more.

This paper proposes and experimentally investigates a novel nondestructive testing method for ferromagnetic elements monitoring, the Magnetic Recording Method (MRM). In this method, the inspected element must be magnetized in a strictly defined manner before operation. This can be achieved using an array of permanent magnets arranged to produce a quasi-sinusoidal magnetization path. The magnetic field caused by the original residual magnetization of the element is measured and stored for future reference. After the operation or loading, the magnetic field measurement is repeated. Analysis of relative changes in the magnetic field (for selected components) allows identifying applied stress. The proposed research methodology aims to provide information on the steel structure condition unambiguously and accurately. An interpretation of the results without referring to the original magnetization is also possible but could be less accurate. The method can be used as a standard technique for NDT (Non-Destructive Testing) or in structural health monitoring (SHM) systems. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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19 pages, 6905 KiB

Open AccessArticle

Non-Destructive X-ray Characterization of a Novel Joining Method Based on Laser-Melting Deposition for AISI 304 Stainless Steel

by Muhammad Arif Mahmood, Diana Chioibasu, Sabin Mihai, Mihai Iovea, Ion N. Mihailescu and Andrei C. Popescu

Materials 2021, 14(24), 7796; https://doi.org/10.3390/ma14247796 - 16 Dec 2021

Cited by 2 | Viewed by 2382

Abstract

In this study, an application of the laser-melting deposition additive manufacturing technique as a welding method has been studied for the laser welding (LW) of AISI 304 stainless steel, specifically 0.4 mm and 0.5 mm thick sheets. The welding was carried out without [...] Read more.

In this study, an application of the laser-melting deposition additive manufacturing technique as a welding method has been studied for the laser welding (LW) of AISI 304 stainless steel, specifically 0.4 mm and 0.5 mm thick sheets. The welding was carried out without and with filler material. Inconel 718 powder particles were used as filler material in the second case. A series of experiments were designed by changing the process parameters to identify the effect of operating conditions on the weld width, depth, and height. The welds were examined through metallographic experiments performed at various cross-sections to identify the defects and pores. All the deposited welds were passed through a customized mini-focus X-ray system to analyze the weld uniformities. The optimal operating conditions were determined for 0.4 mm and 0.5 mm sheets for the LW with and without filler material. It was found that laser power, laser scanning speed, powder flow rate, and helium to argon gases mixture-control the weld bead dimensions and quality. X-ray analyses showed that the optimal operating conditions gave the least peak value of non-uniformity in the laser welds. This study opens a new window for laser welding via additive manufacturing with X-ray monitoring. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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18 pages, 7234 KiB

Open AccessArticle

Pulsed Multifrequency Excitation and Spectrogram Eddy Current Testing (PMFES-ECT) for Nondestructive Evaluation of Conducting Materials

by Jacek Michał Grochowalski and Tomasz Chady

Materials 2021, 14(18), 5311; https://doi.org/10.3390/ma14185311 - 15 Sep 2021

Cited by 10 | Viewed by 2459

Abstract

This paper presents a new method for nondestructive testing—a pulsed multifrequency excitation and spectrogram eddy current testing (PMFES-ECT), which is an extension of the multifrequency excitation and spectrogram eddy current testing. The new method uses excitation in the form of pulses repeated at [...] Read more.

This paper presents a new method for nondestructive testing—a pulsed multifrequency excitation and spectrogram eddy current testing (PMFES-ECT), which is an extension of the multifrequency excitation and spectrogram eddy current testing. The new method uses excitation in the form of pulses repeated at a specified time, containing several periods of a waveform consisting of the sum of sinusoids with a selected frequency, amplitude and phase. This solution allows the maintenance of the advantages of multifrequency excitation and, at the same time, generates high energy pulses similar to those used in pulse eddy current testing (PECT). The effectiveness of the new method was confirmed by numerical simulations and the measurement of thin Inconel plates, consisting of notches manufactured by the electric-discharge method. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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16 pages, 3831 KiB

Open AccessArticle

Analysis of Magnetic Nondestructive Measurement Methods for Determination of the Degradation of Reactor Pressure Vessel Steel

by Gábor Vértesy, Antal Gasparics, Ildikó Szenthe, Madalina Rabung, Melanie Kopp and James M. Griffin

Materials 2021, 14(18), 5256; https://doi.org/10.3390/ma14185256 - 13 Sep 2021

Cited by 4 | Viewed by 1941

Abstract

Nondestructive magnetic measurement methods can be successfully applied to determine the embrittlement of nuclear pressure vessel steel caused by neutron irradiation. It was found in previous works that reasonable correlation could be obtained between the nondestructively measured magnetic parameters and destructively determined ductile-to-brittle [...] Read more.

Nondestructive magnetic measurement methods can be successfully applied to determine the embrittlement of nuclear pressure vessel steel caused by neutron irradiation. It was found in previous works that reasonable correlation could be obtained between the nondestructively measured magnetic parameters and destructively determined ductile-to-brittle transition temperature. However, a large scatter of the measurement points was detected even in the cases of the non-irradiated reference samples. The reason for their scattering was attributed to the local inhomogeneity of material. This conclusion is verified in the present work by applying three different magnetic methods on two sets of Charpy samples made of two different reactor steel materials. It was found that by an optimal magnetic pre-selection of samples, a good, linear correlation can be found between magnetic parameters as well as the ductile-to-brittle transition temperature with low scattering of points. This result shows that neutron irradiation embrittlement depends very much on the local material properties. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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21 pages, 8357 KiB

Open AccessArticle

Different Approaches for Manufacturing Ti-6Al-4V Alloy with Triply Periodic Minimal Surface Sheet-Based Structures by Electron Beam Melting

by Dmitriy Khrapov, Maria Kozadayeva, Kayrat Manabaev, Alexey Panin, William Sjöström, Andrey Koptyug, Tatiana Mishurova, Sergei Evsevleev, Dietmar Meinel, Giovanni Bruno, David Cheneler, Roman Surmenev and Maria Surmeneva

Materials 2021, 14(17), 4912; https://doi.org/10.3390/ma14174912 - 29 Aug 2021

Cited by 30 | Viewed by 3381

Abstract

Targeting biomedical applications, Triply Periodic Minimal Surface (TPMS) gyroid sheet-based structures were successfully manufactured for the first time by Electron Beam Melting in two different production Themes, i.e., inputting a zero (Wafer Theme) and a 200 µm (Melt Theme) wall thickness. Initial assumption [...] Read more.

Targeting biomedical applications, Triply Periodic Minimal Surface (TPMS) gyroid sheet-based structures were successfully manufactured for the first time by Electron Beam Melting in two different production Themes, i.e., inputting a zero (Wafer Theme) and a 200 µm (Melt Theme) wall thickness. Initial assumption was that in both cases, EBM manufacturing should yield the structures with similar mechanical properties as in a Wafer-mode, as wall thickness is determined by the minimal beam spot size of ca 200 µm. Their surface morphology, geometry, and mechanical properties were investigated by means of electron microscopy (SEM), X-ray Computed Tomography (XCT), and uniaxial tests (both compression and tension). Application of different manufacturing Themes resulted in specimens with different wall thicknesses while quasi-elastic gradients for different Themes was found to be of 1.5 GPa, similar to the elastic modulus of human cortical bone tissue. The specific energy absorption at 50% strain was also similar for the two types of structures. Finite element simulations were also conducted to qualitatively analyze the deformation process and the stress distribution under mechanical load. Simulations demonstrated that in the elastic regime wall, regions oriented parallel to the load are primarily affected by deformation. We could conclude that gyroids manufactured in Wafer and Melt Themes are equally effective in mimicking mechanical properties of the bones. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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23 pages, 11457 KiB

Open AccessArticle

Extended Damage Detection and Identification in Aircraft Structure Based on Multifrequency Eddy Current Method and Mutual Image Similarity Assessment

by Tomasz Chady, Krzysztof Okarma, Robert Mikołajczyk, Michał Dziendzikowski, Piotr Synaszko and Krzysztof Dragan

Materials 2021, 14(16), 4452; https://doi.org/10.3390/ma14164452 - 9 Aug 2021

Cited by 9 | Viewed by 2715

Abstract

In this paper, a novel approach to Non-Destructive Testing (NDT) of defective materials for the aircraft industry is proposed, which utilizes an approach based on multifrequency and spectrogram eddy current method combined with an image analysis method previously applied for general-purpose full-reference image [...] Read more.

In this paper, a novel approach to Non-Destructive Testing (NDT) of defective materials for the aircraft industry is proposed, which utilizes an approach based on multifrequency and spectrogram eddy current method combined with an image analysis method previously applied for general-purpose full-reference image quality assessment (FR IQA). The proposed defect identification method is based on the use of the modified SSIM4 image quality metric. The developed method was thoroughly tested for various locations, sizes, and configurations of defects in the examined structure. Its application makes it possible to not only determine the presence of cracks but also estimate their size. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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14 pages, 4162 KiB

Open AccessArticle

Examining Ferromagnetic Materials Subjected to a Static Stress Load Using the Magnetic Method

by Tomasz Chady and Ryszard Łukaszuk

Materials 2021, 14(13), 3455; https://doi.org/10.3390/ma14133455 - 22 Jun 2021

Cited by 5 | Viewed by 2174

Abstract

This paper discusses the experimental examination of anisotropic steel-made samples subjected to a static stress load. A nondestructive testing (NDT) measurement system with a transducer, which enables observation of local hysteresis loops and detection of samples’ inhomogeneity, is proposed. Local hysteresis loops are [...] Read more.

This paper discusses the experimental examination of anisotropic steel-made samples subjected to a static stress load. A nondestructive testing (NDT) measurement system with a transducer, which enables observation of local hysteresis loops and detection of samples’ inhomogeneity, is proposed. Local hysteresis loops are measured on two perpendicular axes, including one parallel to the rolling direction of the samples. The results confirm that the selected features of the local hysteresis loops provide important information about the conditions of ferromagnetic materials. Furthermore, it is shown that the selected parameters of the statistical analysis of the achieved measurements are beneficial for evaluating stress and fatigue changes induced in the material. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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14 pages, 7522 KiB

Open AccessArticle

X-ray Computed Tomography Procedures to Quantitatively Characterize the Morphological Features of Triply Periodic Minimal Surface Structures

by Sergei Evsevleev, Tatiana Mishurova, Dmitriy Khrapov, Aleksandra Paveleva, Dietmar Meinel, Roman Surmenev, Maria Surmeneva, Andrey Koptyug and Giovanni Bruno

Materials 2021, 14(11), 3002; https://doi.org/10.3390/ma14113002 - 1 Jun 2021

Cited by 18 | Viewed by 3056

Abstract

Additively manufactured (AM) metallic sheet-based Triply Periodic Minimal Surface Structures (TPMSS) meet several requirements in both bio-medical and engineering fields: Tunable mechanical properties, low sensitivity to manufacturing defects, mechanical stability, and high energy absorption. However, they also present some challenges related to quality [...] Read more.

Additively manufactured (AM) metallic sheet-based Triply Periodic Minimal Surface Structures (TPMSS) meet several requirements in both bio-medical and engineering fields: Tunable mechanical properties, low sensitivity to manufacturing defects, mechanical stability, and high energy absorption. However, they also present some challenges related to quality control, which can prevent their successful application. In fact, the optimization of the AM process is impossible without considering structural characteristics as manufacturing accuracy, internal defects, as well as surface topography and roughness. In this study, the quantitative non-destructive analysis of TPMSS manufactured from Ti-6Al-4V alloy by electron beam melting was performed by means of X-ray computed tomography (XCT). Several advanced image analysis workflows are presented to evaluate the effect of build orientation on wall thicknesses distribution, wall degradation, and surface roughness reduction due to the chemical etching of TPMSS. It is shown that the manufacturing accuracy differs for the structural elements printed parallel and orthogonal to the manufactured layers. Different strategies for chemical etching show different powder removal capabilities and both lead to the loss of material and hence the gradient of the wall thickness. This affects the mechanical performance under compression by reduction of the yield stress. The positive effect of the chemical etching is the reduction of the surface roughness, which can potentially improve the fatigue properties of the components. Finally, XCT was used to correlate the amount of retained powder with the pore size of the functionally graded TPMSS, which can further improve the manufacturing process. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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14 pages, 8558 KiB

Open AccessArticle

On the Response of a Micro Non-Destructive Testing X-ray Detector

by Dionysios Linardatos, Vaia Koukou, Niki Martini, Anastasios Konstantinidis, Athanasios Bakas, George Fountos, Ioannis Valais and Christos Michail

Materials 2021, 14(4), 888; https://doi.org/10.3390/ma14040888 - 13 Feb 2021

Cited by 27 | Viewed by 3979

Abstract

Certain imaging performance metrics are examined for a state-of-the-art 20 μm pixel pitch CMOS sensor (RadEye HR), coupled to a Gd₂O₂S:Tb scintillator screen. The signal transfer property (STP), the modulation transfer function (MTF), the normalized noise power spectrum (NNPS) [...] Read more.

Certain imaging performance metrics are examined for a state-of-the-art 20 μm pixel pitch CMOS sensor (RadEye HR), coupled to a Gd₂O₂S:Tb scintillator screen. The signal transfer property (STP), the modulation transfer function (MTF), the normalized noise power spectrum (NNPS) and the detective quantum efficiency (DQE) were estimated according to the IEC 62220-1-1:2015 standard. The detector exhibits excellent linearity (coefficient of determination of the STP linear regression fit, R² was 0.9978), while its DQE peaks at 33% and reaches 10% at a spatial frequency of 3 cycles/mm, for the measured with a Piranha RTI dosimeter (coefficient of variation CV = 0.03%) exposure value of 28.1 μGy DAK (detector Air Kerma). The resolution capabilities of the X-ray detector under investigation were compared to other commercial CMOS sensors, and were found in every case higher, except from the previous RadEye HR model (CMOS—Gd₂O₂S:Tb screen pair with 22.5 μm pixel pitch) version which had slightly better MTF. The present digital imager is designed for industrial inspection applications, nonetheless its applicability to medical imaging, as well as dual-energy is considered and certain approaches are discussed in this respect. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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31 pages, 14638 KiB

Open AccessArticle

A Novel Camera-Based Measurement System for Roughness Determination of Concrete Surfaces

by Barış Özcan, Raimund Schwermann and Jörg Blankenbach

Materials 2021, 14(1), 158; https://doi.org/10.3390/ma14010158 - 31 Dec 2020

Cited by 13 | Viewed by 3086

Abstract

Determining the roughness of technical surfaces is an important task in many engineering disciplines. In civil engineering, for instance, the repair and reinforcement of building component parts (such as concrete structures) requires a certain surface roughness in order to ensure the bond between [...] Read more.

Determining the roughness of technical surfaces is an important task in many engineering disciplines. In civil engineering, for instance, the repair and reinforcement of building component parts (such as concrete structures) requires a certain surface roughness in order to ensure the bond between a coating material and base concrete. The sand patch method is so far the state-of-the-art for the roughness measurement of concrete structures. Although the method is easy to perform, it suffers from considerable drawbacks. Consequently, more sophisticated measurement systems are required. In a research project, we developed a novel camera-based alternative, which comes with several advantages. The measurement system consists of a mechanical cross slide that guides an industrial camera over a surface to be measured. Images taken by the camera are used for 3D reconstruction. Finally, the reconstructed point clouds are used to estimate roughness. In this article, we present our measurement system (including the hardware and the self-developed software for 3D reconstruction). We further provide experiments to camera calibration and evaluation of our system on concrete specimens. The resulting roughness estimates for the concrete specimens show a strong linear correlation to reference values obtained by the sand patch method. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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18 pages, 9789 KiB

Open AccessArticle

Microstructural Analysis and Mechanical Properties of TiMo₂₀Zr₇Ta₁₅Si_x Alloys as Biomaterials

by Adriana Savin, Mihail Liviu Craus, Alina Bruma, František Novy, Sylvie Malo, Milan Chlada, Rozina Steigmann, Petrica Vizureanu, Christelle Harnois, Vitalii Turchenko and Zdenek Prevorovsky

Materials 2020, 13(21), 4808; https://doi.org/10.3390/ma13214808 - 28 Oct 2020

Cited by 5 | Viewed by 3370

Abstract

TiMoZrTaSi alloys appertain to a new generation of metallic biomaterials, labeled high-entropy alloys, that assure both biocompatibility as well as improved mechanical properties required by further medical applications. This paper presents the use of nondestructive evaluation techniques for new type of alloys, TiMo [...] Read more.

TiMoZrTaSi alloys appertain to a new generation of metallic biomaterials, labeled high-entropy alloys, that assure both biocompatibility as well as improved mechanical properties required by further medical applications. This paper presents the use of nondestructive evaluation techniques for new type of alloys, TiMo₂₀Zr₇Ta₁₅Si_x, with x = 0; 0.5; 0.75; 1.0, which were obtained by vacuum melting. In Ti alloys, the addition of Mo improves tensile creep strength, Si improves both the creep and oxidation properties, Zr leads to an α crystalline structure, which increases the mechanical strength and assures a good electrochemical behavior, and Ta is a β stabilizer sustaining the formation of solid β-phases and contributes to tensile strength improvement and Young modulus decreasing. The effects of Si content on the mechanical properties of the studied alloys and the effect of the addition of Ta and Zr under the presence of Si on the evolution of crystallographic structure was studied. The influence of composition on fracture behavior and strength was evaluated using X-ray diffraction, resonant ultrasound spectroscopy (RUS) analyses, SEM with energy dispersive X-ray spectroscopy, and acoustic emission (AE) within compression tests. The β-type TiMo₂₀Zr₇Ta₁₅Si_x alloys had a good compression strength of over 800 MPa, lower Young modulus (69.11–89.03 GPa) and shear modulus (24.70–31.87 GPa), all offering advantages for use in medical applications. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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27 pages, 12806 KiB

Open AccessArticle

Detection and Quantification of Cracking in Concrete Aggregate through Virtual Data Fusion of X-Ray Computed Tomography Images

by Tyler Oesch, Frank Weise and Giovanni Bruno

Materials 2020, 13(18), 3921; https://doi.org/10.3390/ma13183921 - 4 Sep 2020

Cited by 13 | Viewed by 2738

Abstract

In this work, which is part of a larger research program, a framework called “virtual data fusion” was developed to provide an automated and consistent crack detection method that allows for the cross-comparison of results from large quantities of X-ray computed tomography (CT) [...] Read more.

In this work, which is part of a larger research program, a framework called “virtual data fusion” was developed to provide an automated and consistent crack detection method that allows for the cross-comparison of results from large quantities of X-ray computed tomography (CT) data. A partial implementation of this method in a custom program was developed for use in research focused on crack quantification in alkali-silica reaction (ASR)-sensitive concrete aggregates. During the CT image processing, a series of image analyses tailored for detecting specific, individual crack-like characteristics were completed. The results of these analyses were then “fused” in order to identify crack-like objects within the images with much higher accuracy than that yielded by any individual image analysis procedure. The results of this strategy demonstrated the success of the program in effectively identifying crack-like structures and quantifying characteristics, such as surface area and volume. The results demonstrated that the source of aggregate has a very significant impact on the amount of internal cracking, even when the mineralogical characteristics remain very similar. River gravels, for instance, were found to contain significantly higher levels of internal cracking than quarried stone aggregates of the same mineralogical type. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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8 pages, 3032 KiB

Open AccessArticle

Contactless Measurements of Carrier Concentrations in InGaAs Layers for Utilizing in InP-Based Quantum Cascade Lasers by Employing Optical Spectroscopy

by Marcin Kurka, Michał Rygała, Grzegorz Sęk, Piotr Gutowski, Kamil Pierściński and Marcin Motyka

Materials 2020, 13(14), 3109; https://doi.org/10.3390/ma13143109 - 12 Jul 2020

Cited by 4 | Viewed by 2124

Abstract

The precise determination of carrier concentration in doped semiconductor materials and nanostructures is of high importance. Many parameters of an operational device are dependent on the proper carrier concentration or its distribution in both the active area as well as in the passive [...] Read more.

The precise determination of carrier concentration in doped semiconductor materials and nanostructures is of high importance. Many parameters of an operational device are dependent on the proper carrier concentration or its distribution in both the active area as well as in the passive parts as the waveguide claddings. Determining those in a nondestructive manner is, on the one hand, demanded for the fabrication process efficiency, but on the other, challenging experimentally, especially for complex multilayer systems. Here, we present the results of carrier concentration determination in In_0.53Ga_0.47As layers, designed to be a material forming quantum cascade laser active areas, using a direct and contactless method utilizing the Berreman effect, and employing Fourier-transform infrared (FTIR) spectroscopy. The results allowed us to precisely determine the free carrier concentration versus changes in the nominal doping level and provide feedback regarding the technological process by indicating the temperature adjustment of the dopant source. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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16 pages, 5271 KiB

Open AccessArticle

Structural and Morphological Quantitative 3D Characterisation of Ammonium Nitrate Prills by X-Ray Computed Tomography

by Fabien Léonard, Zhen Zhang, Holger Krebs and Giovanni Bruno

Materials 2020, 13(5), 1230; https://doi.org/10.3390/ma13051230 - 9 Mar 2020

Cited by 6 | Viewed by 3490

Abstract

The mixture of ammonium nitrate (AN) prills and fuel oil (FO), usually referred to as ANFO, is extensively used in the mining industry as a bulk explosive. One of the major performance predictors of ANFO mixtures is the fuel oil retention, which is [...] Read more.

The mixture of ammonium nitrate (AN) prills and fuel oil (FO), usually referred to as ANFO, is extensively used in the mining industry as a bulk explosive. One of the major performance predictors of ANFO mixtures is the fuel oil retention, which is itself governed by the complex pore structure of the AN prills. In this study, we present how X-ray computed tomography (XCT), and the associated advanced data processing workflow, can be used to fully characterise the structure and morphology of AN prills. We show that structural parameters such as volume fraction of the different phases and morphological parameters such as specific surface area and shape factor can be reliably extracted from the XCT data, and that there is a good agreement with the measured oil retention values. Importantly, oil retention measurements (qualifying the efficiency of ANFO as explosives) correlate well with the specific surface area determined by XCT. XCT can therefore be employed non-destructively; it can accurately evaluate and characterise porosity in ammonium nitrate prills, and even predict their efficiency. Full article

(This article belongs to the Special Issue Micro Non-destructive Testing and Evaluation)

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