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22 pages, 6177 KiB  
Review
Recent Progresses on Hybrid Lithium Niobate External Cavity Semiconductor Lasers
by Min Wang, Zhiwei Fang, Haisu Zhang, Jintian Lin, Junxia Zhou, Ting Huang, Yiran Zhu, Chuntao Li, Shupeng Yu, Botao Fu, Lingling Qiao and Ya Cheng
Materials 2024, 17(18), 4453; https://doi.org/10.3390/ma17184453 - 11 Sep 2024
Cited by 1 | Viewed by 2709
Abstract
Thin film lithium niobate (TFLN) has become a promising material platform for large scale photonic integrated circuits (PICs). As an indispensable component in PICs, on-chip electrically tunable narrow-linewidth lasers have attracted widespread attention in recent years due to their significant applications in high-speed [...] Read more.
Thin film lithium niobate (TFLN) has become a promising material platform for large scale photonic integrated circuits (PICs). As an indispensable component in PICs, on-chip electrically tunable narrow-linewidth lasers have attracted widespread attention in recent years due to their significant applications in high-speed optical communication, coherent detection, precision metrology, laser cooling, coherent transmission systems, light detection and ranging (LiDAR). However, research on electrically driven, high-power, and narrow-linewidth laser sources on TFLN platforms is still in its infancy. This review summarizes the recent progress on the narrow-linewidth compact laser sources boosted by hybrid TFLN/III-V semiconductor integration techniques, which will offer an alternative solution for on-chip high performance lasers for the future TFLN PIC industry and cutting-edge sciences. The review begins with a brief introduction of the current status of compact external cavity semiconductor lasers (ECSLs) and recently developed TFLN photonics. The following section presents various ECSLs based on TFLN photonic chips with different photonic structures to construct external cavity for on-chip optical feedback. Some conclusions and future perspectives are provided. Full article
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15 pages, 13951 KiB  
Article
Investigation of Microstructure and Mechanical Properties of High-Depth-to-Width-Ratio Horizontal NG-GMAW Joint for S500Q Steel
by Ruiyan Jia, Haichao Li, Fangkai Wei, Yufei Zhou, Weizan Duan, Kuiliang Zhang and Zhenglong Lei
Materials 2024, 17(9), 2056; https://doi.org/10.3390/ma17092056 - 27 Apr 2024
Viewed by 1145
Abstract
A novel high depth-to-width ratio of 15:1 narrow-gap gas metal arc welding technique was developed for the welding of S500Q steel in a horizontal butt joint. The bead arrangement of the I groove was optimized to produce a high-quality connection with the upper [...] Read more.
A novel high depth-to-width ratio of 15:1 narrow-gap gas metal arc welding technique was developed for the welding of S500Q steel in a horizontal butt joint. The bead arrangement of the I groove was optimized to produce a high-quality connection with the upper sidewall of the joint. The microstructure and mechanical properties were observed and evaluated by optical microscopy, scanning electron microscopy, tensile testing, and micro-hardness and impact toughness testing at 1/5, 2/5, 3/5, and 4/5 thickness of the joint. The 3/5 T position exhibited the highest strength, which was attributed to the presence of finer carbide precipitates. The highest micro-hardness appeared at 4/5 T. The highest impact toughness appeared at 3/5 T. The formation of coarse granular bainite was the major reason for the decrease in impact toughness in other regions. A microscopic fracture at 1/5 T and 3/5 T was further analyzed. It was observed that the width of the fibrous zone at 3/5 T was significantly larger than that at 1/5 T. The radial zones at 1/5 T were observed to exhibit cleavage, with secondary cracks on the fracture surface. Full article
(This article belongs to the Special Issue Advances in the Welding of Materials)
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13 pages, 7141 KiB  
Article
Selection of Welding Conditions for Achieving Both a High Efficiency and Low Heat Input for Hot-Wire Gas Metal Arc Welding
by Keita Marumoto, Akira Fujinaga, Takeshi Takahashi, Hikaru Yamamoto and Motomichi Yamamoto
J. Manuf. Mater. Process. 2024, 8(2), 82; https://doi.org/10.3390/jmmp8020082 - 18 Apr 2024
Cited by 7 | Viewed by 2144
Abstract
This study presents a new gas metal arc welding (GMAW) technique that achieves both high efficiency and low heat input using a hybridization of the hot-wire method. The optimal combination of welding speed and welding current conditions was investigated using a fixed hot-wire [...] Read more.
This study presents a new gas metal arc welding (GMAW) technique that achieves both high efficiency and low heat input using a hybridization of the hot-wire method. The optimal combination of welding speed and welding current conditions was investigated using a fixed hot-wire feeding speed of 10 m/min on a butt joint with a V-shaped groove using 19 mm thick steel plates. Molten pool stability and defect formation were observed using high-speed imaging and cross-sectional observations. The power consumption and heat input were predicted prior to welding and measured in the experiments. The results indicate that a combination of a welding current of 350–500 A and welding speed of 0.3–0.7 m/min is optimal to avoid defect formation and molten metal precedence using three or four passes. The higher efficiency and lower heat input achieved by hot-wire GMAW results in a weld metal of adequate hardness, narrower heat-affected zone, smaller grain size at the fusion boundary, and lower power consumption than those obtained using tandem GMAW and high-current GMAW. Based on the experimental results, a single bevel groove, which is widely used in construction machinery welding joints, was welded using hot-wire GMAW, and we confirmed that the welding part could be welded in six passes, whereas eight passes were required with GMAW only. Full article
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12 pages, 6301 KiB  
Article
Effect of Beam Oscillation Amplitude on Microstructure and Mechanical Properties of Small Laser Spot Welded QP980 Steel
by Jingwei Yang, Tao Li, Wolin Ye, Jiale Chen and Jian Qiao
Metals 2023, 13(8), 1363; https://doi.org/10.3390/met13081363 - 28 Jul 2023
Cited by 3 | Viewed by 1693
Abstract
In this study, butt welds of QP980 steel were produced using small laser spot (0.1 mm) oscillating welding. The effect of beam oscillation with a circular trajectory on weld morphologies, microstructures, and mechanical properties was characterized. As the oscillating amplitude rose, the energy [...] Read more.
In this study, butt welds of QP980 steel were produced using small laser spot (0.1 mm) oscillating welding. The effect of beam oscillation with a circular trajectory on weld morphologies, microstructures, and mechanical properties was characterized. As the oscillating amplitude rose, the energy accumulation range enlarged, and the energy peak value was decreased, leading to the appearance of the cross-section changing from a nail-like shape to a cup-cone-like shape and then to a W-type shape. The weld zone is divided into the fusion zone, inner heat-affected zone, and outer soften zone. The fusion zone and inner heat-affected zone are full of typical lath martensite and have the highest hardness. The soften zone is composed of pre-existing martensite, temper martensite, ferrite, and retained austenite and has the lowest hardness. Compared to laser welding, beam oscillation could reduce the pre-existing block martensite to decompose, leading to a narrower width and higher hardness soften zone. Although the width of the fusion zone and soften zone increases with the oscillation amplitude, all welded samples failed at the base metal with 97% joint efficiency. Full article
(This article belongs to the Special Issue Laser Welding Technology)
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13 pages, 7175 KiB  
Article
Study on Porosity Defect Detection in Narrow Gap Laser Welding Based on Spectral Diagnosis
by Jinping Liu, Baoping Xu, Yingchao Feng, Peng Chen, Cancan Yan, Zhuyuan Li, Kaisong Yang, Kun She and Yiming Huang
Materials 2023, 16(14), 4989; https://doi.org/10.3390/ma16144989 - 13 Jul 2023
Cited by 2 | Viewed by 2406
Abstract
As an advanced connection technology for large thick-walled components, narrow gap laser welding has the advantages of small heat input and high efficiency and quality. However, porosity defects are prone to occur inside the weld due to the complex welding environment. In this [...] Read more.
As an advanced connection technology for large thick-walled components, narrow gap laser welding has the advantages of small heat input and high efficiency and quality. However, porosity defects are prone to occur inside the weld due to the complex welding environment. In this study, the influence of the process parameters and pollutants such as water and oil on the porosity defect were explored. The action mechanism of water on the electron temperature and spectral intensity of the laser-induced plasma was analyzed. The results showed that the spectral intensity during narrow gap laser welding was weaker than that of flat plate butt welding. Under the optimal welding process conditions, the electron temperature during narrow gap laser self-fusion welding was calculated as 7413.3 K by the Boltzmann plot method. The electron density was 5.6714 × 1015 cm−3, conforming to the thermodynamic equilibrium state. With six groups of self-fusion welding parameters, only sporadic porosity defects were observed according to the X-ray detection. When there was water on the base metal surface, a large number of dense pores were observed on the weld surface and in the weld through X-ray inspection. Compared with the spectral data obtained under the normal process, the relative light intensity of the spectrometer in the whole band was reduced. The electron temperature decreased to the range of 6900 to 7200 K, while the electron density increased. The spectrum variation during narrow gap laser wire filling welding was basically the same as that of laser self-fusion welding. The porosity defects caused by water and oil pollutants in the laser welding could be effectively identified based on the intensity of the Fe I spectral lines. Full article
(This article belongs to the Special Issue Advanced Materials Processing for Engineering Applications)
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16 pages, 5763 KiB  
Article
Design and Mechanical Properties of Flat Anchorage Limit Plate
by Bo Huang, Anyang Wu, Shuang Zhang, Jiawei Wang, Bing Cao, Yihan Du and Yue Zhang
Appl. Sci. 2023, 13(9), 5638; https://doi.org/10.3390/app13095638 - 3 May 2023
Cited by 1 | Viewed by 2129
Abstract
To address the safety problems caused by clips being squeezed by jacks and wire slipping in the tensioning process of flat anchorages, we designed a limit plate to be used with a flat anchorage, and we studied the mechanical properties of the anchorage [...] Read more.
To address the safety problems caused by clips being squeezed by jacks and wire slipping in the tensioning process of flat anchorages, we designed a limit plate to be used with a flat anchorage, and we studied the mechanical properties of the anchorage system after adding the limit plate through numerical simulation. Lastly, the limit plate was created and applied in a practical engineering scenario to test its safety performance. The results showed that the newly designed limit plate changed the butt position of the jack during tension, increased the hole distance, and hid the clips in the hole position of the limit plate, thus mitigating the safety hazard caused by the narrow surface tension construction in practice. The limit plate alleviated the stress concentration on the anchorage, and the extreme stress value decreased by 10–13%. Adverse effects, such as stress concentration caused by tension, were transferred to the replaceable limit plate, thus improving the reliability of the flat anchorage. The symmetrical tensioning scheme represented by sequential tensioning of holes 1, 4, 2, 5, and 3 is recommended, which produced the lowest extreme stress value of 685.55 kPa, which is 22.42 kPa lower than the maximum value of various other schemes. Full article
(This article belongs to the Special Issue Advanced Technologies for Bridge Design and Construction)
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12 pages, 4202 KiB  
Article
Microstructure and Fracture Behaviors of Oscillating Laser Welded 5A06 Aluminum Alloy Lock Butt Joint
by Yang Lu, Jian Lai, Junping Pang, Xin Li, Chen Zhang and Ming Gao
Appl. Sci. 2023, 13(6), 3381; https://doi.org/10.3390/app13063381 - 7 Mar 2023
Viewed by 1851
Abstract
Oscillating laser welding is potential to improve the quality of aluminum alloy joints, but has been seldom addressed on lock butt joint. In this paper, the effects of beam oscillation frequencies (f) on the properties of laser-welded 5A06 aluminum alloy lock [...] Read more.
Oscillating laser welding is potential to improve the quality of aluminum alloy joints, but has been seldom addressed on lock butt joint. In this paper, the effects of beam oscillation frequencies (f) on the properties of laser-welded 5A06 aluminum alloy lock butt joints were investigated, especially those at the lock step. In the microstructure, the columnar grain zone (CGZ) near the fusion line narrowed, the porosity was reduced, and the angle between lock step and fusion line increased with the increase of f. Correspondingly, the fracture changed from equiaxed grain zone to heat affected zone (HAZ), and the fracture angle between lock step and crack propagation line from 90° to 45°. The maximum ultimate tensile strength and elongation of oscillating weld reached 308 MPa and 18.2%, respectively, 36.3% and 203.3% higher than non-oscillating weld. The fracture behaviors indicated that the crack always initiated at the lock step, and then preferably propagated to the pores, followed closely by the weaker CGZ, and then the stronger HAZ when CGZ was narrowed enough. Notably, when the pore size was small (<0.39 mm) and located below the lock step, the pore was not on the crack propagation path. The crack tended to propagate towards the weaker CGZ. Finally, the fracture mechanism was discussed. The results clarify the fracture mechanism of oscillating laser-welded lock butt joints and contribute to the development of oscillating laser welding. Full article
(This article belongs to the Special Issue Focus on Fatigue and Fracture of Engineering Materials)
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14 pages, 8111 KiB  
Article
Interlaminar Microstructure and Mechanical Properties of Narrow Gap Laser Welding of 40-mm-Thick Ti-6Al-4V Alloy
by Xing Liu, Wanli Ling, Yue Li, Jianfeng Wang and Xiaohong Zhan
Materials 2022, 15(21), 7742; https://doi.org/10.3390/ma15217742 - 3 Nov 2022
Cited by 10 | Viewed by 2209
Abstract
Narrow gap laser welding (NGLW) is a common solution for the welding of thick structures. NGLW was carried out on narrow-gap butt joints of 40 mm-thick Ti-6Al-4V alloy plates with a U-shaped groove. The distribution characteristics of the interlaminar microstructure in different height [...] Read more.
Narrow gap laser welding (NGLW) is a common solution for the welding of thick structures. NGLW was carried out on narrow-gap butt joints of 40 mm-thick Ti-6Al-4V alloy plates with a U-shaped groove. The distribution characteristics of the interlaminar microstructure in different height ranges of the joint were investigated, and the evolution behavior and formation mechanism of the interlaminar microstructure of the joint were also revealed. This showed that a large amount of short needle martensite nucleated and grew up near the fusion line and the upper boundary of the remelting zone. The “softening” phenomenon occurred in all welds except the cover layer weld. The microstructure evolution and defect migration, induced by multiple welding thermal cycles in the upper weld forming process, were the main reasons for the “softening” of the lower weld. The tensile strength of each sample changed in the range of 920~990 MPa; the fracture mode of the sample belongs to a transgranular ductile fracture. In addition, compared with the upper part of the joint, the plasticity and toughness of the weld area in the lower part of the joint was improved. Full article
(This article belongs to the Special Issue Welding and Processing in Alloy Manufacturing)
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11 pages, 3709 KiB  
Article
Investigation of Strength and Formability of 6016 Aluminum Tailor Welded Blanks
by Dario Basile, Raffaella Sesana, Manuela De Maddis, Luca Borella and Pasquale Russo Spena
Metals 2022, 12(10), 1593; https://doi.org/10.3390/met12101593 - 24 Sep 2022
Cited by 4 | Viewed by 2901
Abstract
The automotive industry is constantly looking for innovative techniques to produce lighter, more efficient, and less polluting vehicles to comply with the increasingly restrictive environmental regulations. One of the latest technologies, which is still developing, is based on the fabrication of the body-in-white [...] Read more.
The automotive industry is constantly looking for innovative techniques to produce lighter, more efficient, and less polluting vehicles to comply with the increasingly restrictive environmental regulations. One of the latest technologies, which is still developing, is based on the fabrication of the body-in-white and car parts through the stamping of aluminum tailor welded blanks. Tailor welded blanks (TWBs) are generally a combination of two/three metal sheets with different thicknesses and/or mechanical strengths, which are commonly laser butt-welded. Even though the aluminum TWBs have the main advantage of producing lightweight parts, their use is still limited by the lower formability than their parent materials and by the fact that laser welding of aluminum sheets still remains a process easily subjected to weld defects (i.e., internal porosity) and, hence, requires strict control of process parameters. This study has investigated the effects of the main laser welding process parameters (laser power, welding speed, and focus position) on the mechanical properties and formability of aluminum TWBs made of the 6xxx series. The research results show that the welding conditions highly influence the weldability of such alloys. Heat input over 70 J/mm is responsible for excessive porosity and molten pool (and consequent root concavity), which are responsible for the lowest mechanical strength and formability of joints. Differently, low amounts of imperfections have a limited influence on the mechanical behaviors of the TWB joints. Overall, a narrow weldability window is required to ensure welded joints with proper strength and limited or no porosity. Full article
(This article belongs to the Special Issue Welding Metallurgy)
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19 pages, 10399 KiB  
Article
Residual Stress Redistribution Analysis in the Repair Welding of AA6082-T6 Aluminum Alloy Joints: Experiment and Simulation
by Zhihao Chen, Yanjuan Duan, Ping Wang and Hongliang Qian
Materials 2022, 15(18), 6399; https://doi.org/10.3390/ma15186399 - 15 Sep 2022
Cited by 10 | Viewed by 2724
Abstract
Residual stress has a three-dimensional scale effect (length, depth, and width) in the process of repair welding, which has a detrimental impact on the service of the aluminum alloy welded structures in high-speed trains. This paper aims to systematically analyze the effects of [...] Read more.
Residual stress has a three-dimensional scale effect (length, depth, and width) in the process of repair welding, which has a detrimental impact on the service of the aluminum alloy welded structures in high-speed trains. This paper aims to systematically analyze the effects of the repair welding dimension on the residual stress redistribution and obtain the optimal repair welding principles. A combination of blind-hole drilling method and stress linearization in BS7910 was adopted to investigate residual stress redistribution under various repair welding dimensions. The results indicate that repair welding dimension was in accordance with the principle of “SNL (shallow, narrow and long)” and the optimal repair length, depth, and width of butt joints in this study were 15t, 0.25t, and t, respectively (t is the plate thickness of butt joints). Full article
(This article belongs to the Special Issue Fatigue Behavior, Lifetime Prediction and Modeling of Welding Process)
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19 pages, 6442 KiB  
Article
An Approach to Assessing S960QL Steel Welded Joints Using EBW and GMAW
by Raghawendra Pratap Singh Sisodia and Marcell Gáspár
Metals 2022, 12(4), 678; https://doi.org/10.3390/met12040678 - 15 Apr 2022
Cited by 16 | Viewed by 3449
Abstract
In recent years, ultra-high-strength structural (UHSS) steel in quenched and tempered (Q+T) conditions, for example, S960QL has been found in wider application areas such as structures, cranes, and trucks due to its extraordinary material properties and acceptable weldability. The motivation of the study [...] Read more.
In recent years, ultra-high-strength structural (UHSS) steel in quenched and tempered (Q+T) conditions, for example, S960QL has been found in wider application areas such as structures, cranes, and trucks due to its extraordinary material properties and acceptable weldability. The motivation of the study is to investigate the unique capabilities of electron beam welding (EBW) compared to conventional gas metal arc welding (GMAW) for a deep, narrow weld with a small heat-affected zone (HAZ) and minimum thermal distortion of the welded joint without significantly affecting the mechanical properties. In this study, S960QL base material (BM) specimens with a thickness of 15 mm were butt-welded without filler material at a welding speed of 10 mm/s using the high-vacuum (2 × 10−4 mbar) EBW process. Microstructural characteristics were analyzed using an optical microscope (OM), a scanning electron microscope (SEM), fractography, and an electron backscatter diffraction (EBSD) analysis. The macro hardness, tensile strength, and instrumented Charpy-V impact test were performed to evaluate the mechanical properties. Further, the results of these tests of the EBW joints were compared with the GMAW joints of the same steel grade and thickness. Higher hardness is observed in the fusion zone (FZ) and the HAZ compared to the BM but under the limit of qualifying the hardness value (450 HV10) of Q+T steels according to the ISO 15614-11 specifications. The tensile strength of the EBW-welded joint (1044 MPa) reached the level of the BM as the specimens fractured in the BM. The FZ microstructure consists of fine dendritic martensite and the HAZ predominantly consists of martensite. Instrumented impact testing was performed on Charpy-V specimens at −40 °C, which showed the brittle behavior of both the FZ and HAZ but to a significantly lower extent compared to GMAW. The measured average impact toughness of the BM is 162 J and the average impact toughness value of the HAZ and FZ are 45 ± 11 J and 44 ± 20 J, respectively. Full article
(This article belongs to the Special Issue Processing of Advanced High Strength Steel (AHSS))
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12 pages, 4626 KiB  
Article
Ultra-Narrow Gap Fiber Laser Conduction Welding Technology for 304 Stainless Steel Thick Plates and the Mechanical Properties of Welding Joints
by Guowei Zhang and Feihu Yu
Coatings 2022, 12(1), 59; https://doi.org/10.3390/coatings12010059 - 5 Jan 2022
Cited by 11 | Viewed by 3321
Abstract
The application of thick metal plates is increasing, and the welding problem is becoming more and more prominent. Narrow gap laser welding is one of the important methods, and it is also a research hotspot. The stainless steel thick plates were welded using [...] Read more.
The application of thick metal plates is increasing, and the welding problem is becoming more and more prominent. Narrow gap laser welding is one of the important methods, and it is also a research hotspot. The stainless steel thick plates were welded using the ultra-narrow gap fiber laser conduction welding with filler wire. Results show that the ranges of technological parameters for the achievement of the weld seam with no defects are smaller when the gap width is comparatively larger. Using the optimized technological parameters, the butt welding with no defects on the 3 mm gap between two 304 stainless steel plates with 60 mm thickness was achieved through the filling 20 times. This welding method of 304 metal with large thickness is rare in the literature. The tensile strength of the welding joint can be up to 87% of that of the base metal, and the micro-hardness and yield strength of the joint are comparable with those of the base metal. Full article
(This article belongs to the Special Issue Laser Processing Effects on Special Steels and High Entropy Alloys)
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23 pages, 3857 KiB  
Article
Laser Scanning and Parametrization of Weld Grooves with Reflective Surfaces
by Andrej Cibicik, Lars Tingelstad and Olav Egeland
Sensors 2021, 21(14), 4791; https://doi.org/10.3390/s21144791 - 13 Jul 2021
Cited by 9 | Viewed by 3029
Abstract
This paper presents a novel weld groove parametrization algorithm, which is developed specifically for weld grooves in typical stub and butt joints between large tubular elements. The procedure is based on random sample consensus (RANSAC) with additionally proposed correction steps, including a corner [...] Read more.
This paper presents a novel weld groove parametrization algorithm, which is developed specifically for weld grooves in typical stub and butt joints between large tubular elements. The procedure is based on random sample consensus (RANSAC) with additionally proposed correction steps, including a corner correction step for grooves with narrow root weld, and an iterative error elimination step for improving the initially obtained data fit. The problem of curved groove sides (due to the pipe geometry) is attributed and solved. In addition, the procedure detects and eliminates several types of data noise due to laser line reflections. The performance of the procedure is studied experimentally using small-scale test objects, which have been ground using typical industrial power tools to achieve a realistic level of reflections. The execution times and data fit errors of the proposed procedure are compared to a procedure based on a more conventional RANSAC approach for line segment detection. Full article
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20 pages, 3696 KiB  
Article
Insights into Equilibrium and Adsorption Rate of Phenol on Activated Carbon Pellets Derived from Cigarette Butts
by Nahum A. Medellín-Castillo, Raúl Ocampo-Pérez, Angélica Forgionny, Gladis J. Labrada-Delgado, Ana I. Zárate-Guzmán, Sergio A. Cruz-Briano and Rogelio Flores-Ramírez
Processes 2021, 9(6), 934; https://doi.org/10.3390/pr9060934 - 26 May 2021
Cited by 16 | Viewed by 3397
Abstract
In the present work, the preparation of activated carbon pellets from cigarette butts by thermal treatment was evaluated. The morphological, textural, topological, and surface chemical properties were studied by SEM-EDX, N2 adsorption, Raman, and FTIR spectroscopy. For adsorption assays, activated carbon was [...] Read more.
In the present work, the preparation of activated carbon pellets from cigarette butts by thermal treatment was evaluated. The morphological, textural, topological, and surface chemical properties were studied by SEM-EDX, N2 adsorption, Raman, and FTIR spectroscopy. For adsorption assays, activated carbon was tested for the adsorption of phenol as a model molecule at different solution pH, temperature, and type of water. In addition, leaching tests before and after carbonization were conducted to evaluate the lixiviation of ions present in the solid. The results revealed a microporous material, composed of cylindrical fibers (thickness of 13 µm) with a microporous area of 713 m2/g and narrow and uniform slit-shaped pores (0.4–0.8 nm). The surface chemistry analysis evidenced the presence of oxygenated groups (carboxylic, esters, and phenolics). Activated carbon leaching tests indicated that the concentrations of the leached ions did not exceed the maximum permissible limit for drinking water. Phenol adsorption revealed an exothermic process with a maximum adsorption capacity of 272 mg/g at 10 °C. Finally, it was confirmed that phenol diffusion was drastically affected by hindered phenomena due to the similarity in the molecular size of phenol and the average size of micropores, and as a result an effective diffusion coefficient between 6.10 × 10−0 and 5.50 × 10−12 cm2/s and a maximum tortuosity value of 3.3 were obtained. Full article
(This article belongs to the Special Issue Redesign Processes in the Age of the Fourth Industrial Revolution)
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13 pages, 3008 KiB  
Article
Dynamic Error Correction of Filament Thermocouples with Different Structures of Junction based on Inverse Filtering Method
by Chenyang Zhao and Zhijie Zhang
Micromachines 2020, 11(1), 44; https://doi.org/10.3390/mi11010044 - 30 Dec 2019
Cited by 3 | Viewed by 2808
Abstract
Since filament thermocouple is limited by its junction structure and dynamic characteristics, the actual heat conduction process cannot be reproduced during the transient thermal shock. In order to solve this problem, we established a thermocouple dynamic calibration system with laser pulse as excitation [...] Read more.
Since filament thermocouple is limited by its junction structure and dynamic characteristics, the actual heat conduction process cannot be reproduced during the transient thermal shock. In order to solve this problem, we established a thermocouple dynamic calibration system with laser pulse as excitation source to transform the problem of the restoring excitation source acting on the surface temperature of thermocouple junction into the problem of solving the one-dimensional (1D) inverse heat conduction process, proposed a two-layer domain filtering kernel regularization method for double conductors of thermocouple, analyzed the factors causing unstable two-layer domain solution, and solved the regular solution of two-layer domain by the filtering kernel regularization strategy. By laser narrow pulse calibration experiment, we obtained experimental samples of filament thermocouples with two kinds of junction structures, butt-welded and ball-welded; established error estimation criterion; and obtained the optimal filtering kernel parameters by the proposed regularization strategy, respectively. The regular solutions solved for different thermocouples were very close to the exact solution under the optimal strategy, indicating that the proposed regularization method can effectively approach the actual surface temperature of the thermocouple junction. Full article
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