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Zhou, Shujuan, Zhang, Xu, Wang, Li, Zhao, Yuyuan, Xiong, Wei, Li, Baoquan, Li, Jin, Xu, Jin, and Yan, Huizhong
International Journal of Hydrogen Energy . Jan2021, Vol. 46 Issue 5, p3414-3424. 11p.
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SURFACE preparation, HYDROGEN storage, LOW temperatures, ALLOYS, MAGNESIUM hydride, CARBON dioxide, and SAMARIUM
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The low-temperature performance (LTP) of AB 3.42 -type La–Y–Ni hydrogen storage alloy was studied by methods of element substitution and surface treatment. The effect of Mn-additive on LTP of La 1·3 Ce 0·5 Y 4·2 Ni 19.5- x Mn x Al (x = 0, 0.2, 0.5) was systematically investigated. Electrochemical studies showed that Mn-additive deteriorated the LTP of the alloy by reducing platform pressure, deteriorating kinetic performance and forming more oxides on the alloy surface. RE-substitution and hot alkali-ultrasonic treatment of La 1.3 RE 0.5 Y 4·2 Ni 19·5 Al (RE = Ce, Sm, Nd) alloys were applied to further optimize the LTP. The maximum discharge capacity and capacity retention at the 100th cycle of La 1·3 Ce 0·5 Y 4·2 Ni 19·5 Al alloy were 252.1 mA h/g and 87.1% at 243 K, respectively. Furthermore, the LTP of RE-substitution alloys at 243 K was conspicuously improved by surface treatment, which were raised from 214.7 mA h/g to 301.1 mA h/g by Sm-substitute, from 220.9 mA h/g to 303.9 mA h/g by Nd-substitute and from 252.1 mA h/g to 254.8 mA h/g by Ce-substitute. • The Ce 2 Ni 7 and Gd 2 Co 7 -type phase own diverse electrochemical characteristics under different temperatures. • Mn-additive reveals negative effect on the low temperature dischargeability of the alloy. • Surface treatment promotes the low temperature dischargeability of the Mn-free alloy. [ABSTRACT FROM AUTHOR]
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Daneshmehr, Shahla, Román, Frida, and Hutchinson, John M.
Journal of Thermal Analysis & Calorimetry . 2021, Vol. 143 Issue 1, p151-163. 13p.
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The use of coupling agents to enhance the thermal conductivity of composites of epoxy and boron nitride (BN) has been investigated. Two types of BN particles, lightly aggregated platelets with an average size of 6 µm and agglomerates with an average size of 120 µm, have been used. Different proportions of these BN particles, up to a volume percentage of approximately 34%, were mixed with a stoichiometric epoxy–thiol system and cured either isothermally or non-isothermally. The cure kinetics was investigated by differential scanning calorimetry, and the thermal conductivity of isothermally fully cured samples was measured. The effect of surface treatment of the particles was extensively investigated, with respect to the characteristics of the particles themselves, the cure kinetics and the thermal conductivity of the cured composites. The BN particles were treated with a silane coupling agent, both with and without previously treating the BN with a sodium hydroxide solution. Infrared spectroscopy and thermogravimetric analysis were used to assess whether or not the silane had been attached to the BN particles, and the effect of the surface treatment on the cure kinetics was studied. Although the cure kinetics suggested that the surface treatment was more effective for the 6 µm particles than for the 120 µm agglomerates, it did not generally lead to an increase in the thermal conductivity, while scanning electron microscopy showed that the coupling agent was not attached to the BN particles. It is concluded that truly platelet-shaped particles are necessary for effective surface treatment. [ABSTRACT FROM AUTHOR]
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Gumbleton, Richard, Cuenca, Jerome A., Hefford, Samuel, Nai, Kenneth, and Porch, Adrian
IEEE Transactions on Microwave Theory & Techniques . Jan2021, Vol. 69 Issue 1, p189-197. 9p.
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SURFACE resistance, MICROWAVE measurements, MICROWAVE devices, ALLOYS, and MEASUREMENT errors
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Additive manufactured (AM) metals are a subject of much interest for their performance in passive microwave applications. However, limitations could arise due to artifacts, such as surface texture and/or roughness resulting from the manufacturing process. We have, therefore, adopted a parallel plate microwave resonator for the accurate measurement of the surface resistance of flat metal plates, allowing for microwave current flow in two orthogonal directions by simply exciting a different resonant mode (at 5.3 and 6.4 GHz), without the need to remove and refix the sample. The systematic and random errors associated with the measurement of surface resistance are very small, less than 1% and 0.1%, respectively. The technique is demonstrated with measurements on a range of samples of the alloys, AlSi10Mg and Ti6Al4V, manufactured by laser powder bed fusion, in addition to traditionally machined samples of bulk metal alloys of aluminum and brass. For AM samples of AlSi10Mg, we have studied the effect on the surface resistance of directional roughness features, generated by the laser raster paths, in directions transverse or parallel to microwave current flow. Importantly for passive microwave device applications, we demonstrate that these samples exhibit no systematic anisotropy of surface resistance associated with such surface features. [ABSTRACT FROM AUTHOR]
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Key, Cam, Harmon, Jake, and Notaros, Branislav M.
IEEE Transactions on Antennas & Propagation . Jan2021, Vol. 69 Issue 1, p332-346. 15p.
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RICCI flow, COMPUTATIONAL electromagnetics, ALMOND, INTEGRAL equations, JET fighter planes, QUADRILATERALS, and SURFACE preparation
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We propose a surface meshing approach for computational electromagnetics (CEM) based on discrete surface Ricci flow (DSRF) with iterative adaptive refinement (AR) in the parametric domain for the automated generation of high-quality surface meshes of arbitrary element type, order, and count. Surfaces are conformally mapped by DSRF to a canonical parametric domain, allowing a canonical seed mesh to be mapped back to an approximation of the original surface. The new DSRF-based meshing technique provides a framework for generation of meshes with high element quality, aimed to greatly enhance the accuracy, conditioning properties, stability, robustness, and efficiency of surface integral equation CEM solutions. We demonstrate the ability of the proposed DSRF technique to produce meshes with near-optimal element corner angles for complicated, highly varied surfaces such as the NASA almond and a fighter jet model, using triangular, quadrilateral, and discontinuous quadrilateral elements. Other element types are also discussed. Where high-fidelity meshing is desired, the technique can capture fine-scale detail using very few high-order elements. Where low-fidelity meshing is desired, DSRF with AR can accurately recreate course-scale detail using standard first-order elements (e.g., flat triangular patches). [ABSTRACT FROM AUTHOR]
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Abdulkader, Kamilia Faisal, Elnaggar, Gihan Abd Elhady, and Kheiralla, Lamiaa Sayed
Journal of Adhesion Science & Technology . Jan2021, Vol. 35 Issue 1, p35-51. 17p.
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LITHIUM silicates, SURFACE preparation, BOND strengths, SHEAR strength, CERAMICS, and CEMENT composites
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Enhance the bonding of cement to ceramic surface with a variety of ceramic surface modifications have been established. Air-abrasion using alumina particles, hydrofluoric acid has been shown to provide micromechanical interlocking at the ceramic-resin interface. The aim of the present study was to evaluate the effect of two surface treatments; acid etching and sandblasting; on the shear bond strength of cemented newly introduced zirconia-reinforced lithium silicate ceramics following thermocycling. Methods: 24 discs of Zirconia- reinforced glass ceramics (Celtra Duo) were tested using 10% hydrofluoric acid for 20 s (control group) and 50 µm aluminum oxide for 60 s at 10 mm distance from the nozzle tip of sandblasting machine. Subsequent to the surface treatments, both groups were salinized and cemented to composites background discs using self-adhesive dual cure resin cement (BisCem). All sample were subjected to 2500 thermal cycle shear bond strength and failure mode was evaluated. The results of the t-test indicated that the bond strength value is significantly influenced by the surface treatment method. It was found that hydrofluoric acid group recorded statistically significantly higher shear bond strength mean value (10.81 MPa) than aluminum oxide sandblasting group (7.76 MPa) as indicated by t-test (t = 2.9, p = 0.0109 < 0.05). Conclusion: failure mode showed a relation between the bond strength and the failure type mixed failure showed with higher bond valves and cohesive failure accompanied with lowest bond strengthen values. The shear bond strength of zirconia reinforced lithium silicate (Celtra Duo) ceramic cemented to resin cement was affected by the type of surface treatment. [ABSTRACT FROM AUTHOR]
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Akay, Canan, Turan, Neslihan, Karakış, Duygu, and Angurel, Luis Alberto
International Journal of Applied Ceramic Technology . Jan/Feb2021, Vol. 18 Issue 1, p51-59. 9p.
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ULTRAVIOLET lasers, FLEXURAL strength, BOND strengths, TUKEY'S test, ZIRCONIUM oxide, and ONE-way analysis of variance
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Zirconia is a dental material that shows excellent biocompatibility and high strength in clinical applications. This study aims to evaluate the effects of ultrafast laser applications. The surface nanostructures were classified into three groups. Group 1 was generated using the burst mode, with three different distances between dots: 52 µm (Group 1a), 104 µm (Group 1b), and 156 µm (Group 1c). Group 2 was processed using the scanning mode configuration, with a set of parallel lines. Group 3 was also processed using this scanning configuration creating a set of square‐shaped patterning. Group 4 was the control group. After the surface treatments, a pair of zirconia specimens was bonded end to end with resin cement. Flexural bond strength (FBS) test was applied in a universal test machine. Multiple comparisons were performed using a one‐way analysis of variance and the Tukey's HSD test. All the samples that were treated with the laser showed higher FBS values than the untreated surface. Using the burst mode, preformed circular‐shaped surface on an angle of 900 at 52 µm distance (Group 1a) showed the highest FBS values among all groups (p <.05). Groups 2 and 3 had significantly higher values than 1b and 1c. [ABSTRACT FROM AUTHOR]
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Kawashima, Ryosuke, Mishima, Tomokazu, and Ide, Chiaki
IEEE Transactions on Power Electronics . Jan2021, Vol. 36 Issue 1, p639-653. 15p.
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INDUCTION heating, ZERO current switching, METALS, INDUSTRIAL metals, and ZERO voltage switching
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A new multiresonant three-phase utility frequency ac (UFAC) to high-frequency ac (HFAC) direct power converter for the industrial metal hardening induction heating (IH) applications is presented in this article. The proposed ac–ac converter features direct frequency conversion with the wide range of soft switching by means of the minimized numbers of bidirectional switches. The conducting current of bidirectional switches can be reduced effectively owing to the multiresonant tank while keeping a high power in the IH load. Accordingly, the practical power converter with simplicity, cost-effectiveness, and high efficiency can be realized on the basis of a simple pulse-frequency modulation (PFM). The circuit topology and operating principle of the proposed converter are described, after which the design procedure of the multiresonant tank and switching frequency is presented. The performances on the soft switching and the steady-state PFM characteristics of the ac–ac converter are evaluated in experiment with the 1.7 kW/85–90-kHz prototype. Finally, the feasibility of the proposed ac–ac converter is evaluated from a practical view point. [ABSTRACT FROM AUTHOR]
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8. Development of a Process for Applying Cerium-Containing Protective Coatings to Alloy Steel. [2020]
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Abrashov, A. A., Grigoryan, N. S., Vagramyan, T. A., Zhukov, A. F., and Zhukov, A. P.
Protection of Metals & Physical Chemistry of Surfaces . Dec2020, Vol. 56 Issue 7, p1311-1314. 4p.
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PROTECTIVE coatings, STEEL alloys, CERIUM oxides, STAINLESS steel, CHROMIUM oxide, PITTING corrosion, FERRIC oxide, and CERIUM compounds
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A solution has been developed for deposition of cerium-containing coatings on an alloy steel base that meets the requirements for protective coatings. It is established that the protective coating on alloyed steel consists of cerium oxides Ce2O3 and CeG2, iron oxide Fe2O3, and chromium oxide Cr2O3. Passivation of stainless steel in a cerium-containing solution has been shown to significantly increase its resistance to pitting corrosion. [ABSTRACT FROM AUTHOR]
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9. Application of cerium phosphate in preparing anti-ultraviolet PET fibers with masterbatch method. [2020]
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Gao, Kezheng, Hu, Die, Wang, Suwei, Ding, Yun, Sheng, Pinghou, Xue, Ping, Jiang, Wei, Chen, Ke, and Qiao, Hui
Journal of Polymer Research . Dec2020, Vol. 27 Issue 12, p1-12. 12p.
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CERIUM oxides, FOURIER transform infrared spectroscopy, POLYETHYLENE terephthalate, CERIUM, and FIBERS
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In this work, a novel cerium-based anti-ultraviolet fiber (CAUF) was prepared by masterbatch method for the first time. A pigment material, nano-cerium phosphate (nano-CePO4) was modified by aluminate coupling agent and then applied as the cerium-based anti-ultraviolet agent (CAUA) in the preparation of masterbatch. The characteristics of anti-ultraviolet agent, masterbatch and fibers were investigated by Fourier transform infrared spectroscopy, electron microscopy, differential scanning calorimeter, X-ray diffractometer, contact angle meter and ultraviolet spectrophotometer. The results indicated that masterbatch with the CAUA content of 10 wt.% could achieve the excellent dispersion of nanoparticles in PET matrix and improve the compatibility between nanoparticles and PET matrix, which was chosen for spinning. As the content of masterbatch (CAUA) in fibers reached to 15 wt.% (1.5 wt.%), not only the good physical–mechanical properties of fibers were achieved, but also the ultraviolet transmittance of fibers in UVA and UVB bands decreased to 2.27% and 0.57%, which presented the better anti-ultraviolet property than nano-titanium dioxide. Therefore, surface modified nano-CePO4 is a promising inorganic anti-ultraviolet agent with great chemical inertia, low photocatalytic activity and high absorption in the UV region, which could endow fibers with excellent protection properties in both UVA and UVB bands. [ABSTRACT FROM AUTHOR]
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Alter, Anne L., Flader, Ian B., Chen, Yunhan, Ortiz, Lizmarie Comenencia, Shin, Dongsuk D., and Kenny, Thomas W.
Journal of Microelectromechanical Systems . Dec2020, Vol. 29 Issue 6, p1483-1492. 10p.
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MEMS resonators, FRACTURE mechanics, FATIGUE, HIGH temperatures, SURFACE roughness, and HELMHOLTZ resonators
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Fatigue in thick ($> 20~\mu \text{m}$), epitaxially deposited polysilicon MEMS is characterized from 25°C and up to 250°C in an environment free of oxygen and humidity. This work is the first to report fatigue initiated in the native epi-polysilicon, free from any contributions due to oxide or environmental conditions. Fatigue was most prominent above stresses of 1.5 GPa at all temperatures. Resonant frequency shift is used to measure crack growth, and elevated temperatures increased the total frequency drift and frequency drift rates. Since the epi-polysilicon surfaces roughen due to grain boundary migration during fabrication, we conclude that epi-polysilicon fatigue can be attributed to a subcritical cracking mechanism that arises from surface roughness. Furthermore, the measured increases in the critical crack length before failure suggest that the fracture toughness increases at the elevated temperatures. [2020-0068] [ABSTRACT FROM AUTHOR]
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Qi, Xuanmeng, Yoshida, Shinya, and Tanaka, Shuji
IEEE Transactions on Ultrasonics Ferroelectrics & Frequency Control . Dec2020, Vol. 67 Issue 12, p2738-2744. 7p.
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PIEZOELECTRIC thin films, THIN films, SPUTTER deposition, MICROELECTROMECHANICAL systems, PIEZOELECTRIC transducers, EPITAXY, and SOLAR cells
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We have developed a unique sputter deposition technique for a pure-perovskite (001)/(100)-oriented samarium-doped Pb(Mg1/3, Nb2/3)O3–PbTiO3 (Sm-PMN-PT) epitaxial thin film on Si as a future piezoelectric transducer thin film in microelectromechanical systems (MEMSs). This technique bases on the use of a “Pb(Zr,Ti)O3 (PZT)-based seed layer” and “separate sputter deposition.” Undesired orientations and phases of such a relaxor-based ferroelectric are usually generated during the sputter deposition. This technique was demonstrated to provide preferential (001)/(100) orientation and pure-perovskite phase to the monocrystalline thin film. The fabricated film had excellent homogeneousness of the content distribution. Considering a practical thickness, a 2- $\mu \text{m}$ -thick monocrystalline thin film was grown on an Si substrate with this technique. Then, the piezoelectricity $\vert {e}_{{31},{f}}\vert $ of the Sm-PMN-PT/PZT stacked film was evaluated through an actuation test of the unimorph cantilever. As a result, it measured 16–17 C/m2, which is almost comparable with intrinsic PZT polycrystalline thin films with high $\vert {e}_{{31},{f}}\vert $ values. Considering that the actuation voltage was divided into Sm-PMN-PT and PZT layers, the inherent piezoelectricity of the Sm-PMN-PT thin film is expected to be higher. Optimization of the phase in the film by tuning the composition ratio also will further improve the piezoelectricity. We believe that this achievement is a great step to discover a giant piezoelectricity relaxor-based thin film beyond PZT for MEMS. [ABSTRACT FROM AUTHOR]
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Wen, Guojun, Gao, Zhijun, Cai, Qi, Wang, Yudan, and Mei, Shuang
IEEE Transactions on Instrumentation & Measurement . Dec2020, Vol. 69 Issue 12, p9668-9680. 13p.
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CONVOLUTIONAL neural networks, SEMICONDUCTOR wafers, SURFACE defects, SEMICONDUCTOR manufacturing, ROBOTIC welding, and MANUFACTURING processes
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Semiconductor wafer is widely used in welding robot, spray robot, unmanned material delivery vehicle, and detection station sensor. The defects of semiconductor wafer, such as stains, burrs, scratches, and holes generated in the manufacturing process, severely affect the quality of downstream products. Therefore, the inspection of wafer defect could not be neglected. Traditional semiconductor wafer defect inspection methods based on handcrafted features heavily rely on the expertise and are limited in some application scenario. In this article, a novel method based on deep convolutional neural networks for semiconductor wafer surface defect inspection is proposed. First, a new structure of feature pyramid networks with atrous convolution (FPNAC) is developed to extract the features and to generate feature maps. Second, the feature maps are fed into region proposal network (RPN) to generate region proposals. Finally, the region proposals are aligned to corresponding size as the inputs of deep multibranches neural network (DMBNN) consisting of three branches, to classify and segment the defects precisely. Experimental results demonstrate that the proposed method yields good comprehensive performance with mean pixel accuracy (MPA) 93.97% and mean intersection over union (MIoU) 83.58%. [ABSTRACT FROM AUTHOR]
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Liu, Zhenyu, Yang, Benyi, Duan, Guifang, and Tan, Jianrong
IEEE Transactions on Instrumentation & Measurement . Dec2020, Vol. 69 Issue 12, p9681-9694. 14p.
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CONVOLUTIONAL neural networks, METALLIC surfaces, METAL defects, INSPECTION & review, and PYRAMIDS
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Visual surface defect inspection for metal part has become a rapidly developing research field within the last decade. But due to the variances of defect shapes and scales, the inspection of tiny and irregular shape defects has posed challenges on the robustness of the inspection model. In this context, a deep learning method based on the deformable convolution and concatenate feature pyramid (CFP) neural networks is proposed to improve the inspection. We design a deformable convolution layer in the neural networks as an attention mechanism to adaptively extract the features of defect shape and location, which enhances the inspection of the defects with large shape variances. We also merge the multiple hierarchical features collected from different deformable convolution layers by the CFP, which improves the inspection of tiny defects. The results show that the proposed method has a better generalization ability than traditional convolution neural networks. [ABSTRACT FROM AUTHOR]
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Nategh, Mahshid, Nikoo, Amir Hossein, and Malayeri, M. Reza
Chemical Engineering Research & Design: Transactions of the Institution of Chemical Engineers Part A . Dec2020, Vol. 164, p373-384. 12p.
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SURFACE energy, SURFACE temperature, COHESION, HEAT exchanger fouling, METALLIC surfaces, HIGH temperatures, and COAGULATION
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• Substantial increase of acid-base interaction energy with surface temperature • Reduction of Lifshitz-van der Waals interaction energy with surface temperature • Spreading coefficient better interpolates dependency of deposition on temperature • Surface energy-based correlation for prediction of CaSO 4 deposition propensity • Impact of surface temperature on coagulation to precursors While numerous surface energy-based studies have investigated various aspects of CaSO 4 deposition on modified surfaces, the impact of surface temperature though, as a dominant parameter, has not thoroughly been characterized from surface energy perspective. This has led that most previous studies have attained surface energy specifications at ambient temperature for utilization at elevated operating temperatures. The present study examines the impact of surface temperature in the range of 293–368 K, but at a constant bulk temperature less than surface temperature, on surface energy and its sub-components of several metallic surfaces and amorphous carbon-based coatings. Moreover, the influence of surface temperature on the energy of adhesion between CaSO 4 precursors and these surfaces, energy of cohesion between precursors as well as wettability of surfaces in terms of spreading coefficient are also investigated. Results showed that the Lewis acid-base sub-component of surface energy experiences profound changes, at least 3-fold increase, with temperature, while it is a maximum of 1.5-fold decrease for the Lifshitz-van der Waals sub-component. A cumulative correlation based on the spreading coefficient is also proposed to project the propensity of investigated surfaces to CaSO 4 deposition as a function of temperature and is validated using data from the literature. [ABSTRACT FROM AUTHOR]
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Bessa, Wissam, Trache, Djalal, Derradji, Mehdi, Ambar, Houda, Tarchoun, Ahmed Fouzi, Benziane, Mokhtar, and Guedouar, Bendiba
International Journal of Biological Macromolecules . Dec2020, Vol. 164, p2931-2943. 13p.
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GIANT reed, CRYSTALLIZATION, DIFFERENTIAL scanning calorimetry, FIBERS, ANALYTICAL mechanics, and ACTIVATION energy
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In the present work, giant reed cellulosic fibers (Arundo donax L., RF) were explored as reinforcement of bisphenol A-based benzoxazine (BA-a). RF were extracted from giant reed cane, and subjected to different chemical treatments using either alkaline, silane or their combining treatments. The examination of the structural, thermal, crystallinity and morphological properties of the untreated (NRF) and treated fibers (TRF) was carried out using different analytical techniques. Broadly, the morphology of the treated fibers is affected, their crystallinity and thermal stability increased. The investigation of the effect of the treated fibers on the curing kinetics of composites based on BA-a was performed by differential scanning calorimetry (DSC) technique, under non-isothermal conditions, and isoconversional integral kinetic methods. A decrease in the heat of curing as well as activation energy (Ea) was reported. The Avrami-Erofeev autocatalytic kinetic model was the most appropriate to describe the curing reactions and the predicted curves from the calculated kinetic parameters fitted well with experimental data. [ABSTRACT FROM AUTHOR]
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16. Influence of surface contaminants on the adhesion strength of structural adhesives with aluminium. [2020]
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Akiyama, H., Fukata, T., Sato, T., Horiuchi, S., and Sato, C.
Journal of Adhesion . 2020, Vol. 96 Issue 15, p1311-1325. 15p.
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POLLUTANTS, FOURIER transform infrared spectroscopy, ADHESION, MINERAL oils, and ALUMINUM plates
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Surface contamination of an adherend has an influence on its adhesive bonding properties. To investigate this phenomenon, various contaminants, including silicone oil, mineral oil, a fluorine release agent, and surfactants, were quantitatively applied to an aluminium plate (6061) using a spray apparatus. The contaminated adherends were bonded with acrylic and epoxy adhesives, and their adhesion strengths were examined using single lap-shear tests. Mineral oil did not affect the adhesion strength, but silicone oil and surfactant agents were found to significantly affect the adhesion strength. Atomic force microscopy observations and Fourier transform infrared spectroscopy of these surfaces revealed a specific interaction between silicone oil and aluminium. [ABSTRACT FROM AUTHOR]
17. 물리적 표면처리 기법에 따른 복합소재 및 알루미늄간 접합특성 연구. [2020]
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김무선
Journal of the Korea Academia-Industrial Cooperation Society . 2020, Vol. 21 Issue 11, p334-339. 6p.
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SURFACE preparation, GLASS composites, FIBROUS composites, MECHANICAL abrasion, SURFACES (Technology), and ADHESIVE joints
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In this study, the adhesion properties between aluminum and composite materials, composite materials, and composite materials were compared according to the physical surface treatment to improve mechanical bonding at the bonding surface when considering carbon fiber and glass fiber-reinforced composite materials. Bonded specimens were classified into the type of base material and the surface treatment method of the bonding surface. Sandpaper, sandblasting, and plasma were applied as physical surface treatment methods. The bonded specimen was prepared as a single lap joint test specimen. An experiment to measure the lap shear strength was conducted, and the results were compared. The experimental results confirmed that the mechanical abrasion and sandblasting treatment improved the lap shear strength approximately 4 to 5 fold compared to the general specimen without physical surface treatment. In plasma treatment, the experiment was conducted by defining the respective plasma output and treatment time as follows: 150 W and 5 minutes, 150 W and 10 minutes, and 300 W and 3 minutes. Moreover, the lap shear strength results were similar to the previous mechanical surface treatments. On the other hand, the effect on the adhesion properties was small, depending on the plasma treatment conditions. [ABSTRACT FROM AUTHOR]
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Pai, Hsiang Ting and Lin, Che-Hsin
IEEE Transactions on Plasma Science . Nov2020, Vol. 48 Issue 11, p3915-3920. 6p.
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ELECTRIC insulators & insulation, FLIP chip technology, SEMICONDUCTORS, VACUUM chambers, PACKAGING, NUMERICAL calculations, and ELECTRIC fields
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Delamination between the molding compound and the die surface is a common failure pattern in the semiconductor package industry. Plasma treatment is a standard process to clean and activate the die surface to enhance the bonding force between the molding compound and the die surface in the packing procedure. However, the unexpected delamination still happens and results in a huge commercial loss for the packaged products. This study adopts experimental and numerical approaches to systematically investigate the delamination risk for plasma treatment before compound molding. A vacuum chamber is established to visualize the plasma distribution and the oxidation condition of the lead frames placed on the metal and the insulator rails. Moreover, a numerical calculation is used to systematically predict the plasma distribution over the lead frame and die surface. Results show that the lead frame placed on the metal rail exhibited a higher electric field gradient than that placed on the insulation rail. Moreover, the copper lead frame placed on the insulation rail exhibits a lower electric field gradient and less metal oxidation on the die surface. The delamination risk for semiconductor packaging can be systematically predicted and efficiently reduced before the packing process with the results obtained in the present study. [ABSTRACT FROM AUTHOR]
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19. Design Guidelines and Performance Tradeoffs in Recessed AlGaN/GaN Schottky Barrier Diodes. [2020]
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Soni, Ankit, K. M., Amogh, and Shrivastava, Mayank
IEEE Transactions on Electron Devices . Nov2020, Vol. 67 Issue 11, p4834-4841. 8p.
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SCHOTTKY barrier diodes, WIDE gap semiconductors, and ALUMINUM gallium nitride
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Critical design parameters for AlGaN/GaN Schottky barrier diodes (SBDs) are analyzed in this work using TCAD computations and detailed experiments. A comprehensive TCAD-based computational modeling approach is developed for GaN-based SBD. Breakdown mechanisms in SBD for unintentionally doped (UID) buffer, Fe-doped buffer and C-doped buffer are studied. For the first time, we have reported impact of anode recess, on breakdown and leakage behavior of SBD, in correlation with interface defects. Using these insights an optimum recess design strategy has been presented and is validated experimentally. Furthermore, for the first time, we have revealed critical repercussions of the field plate termination on SBD’s breakdown, leakage as well as transient behavior. Forward and reverse recovery measurements were carried out to study the diode’s transient performance as a function of field plate design. Various performance matrices such as diode current collapse, reverse current overshoot and reverse recovery time were studied experimentally as a function of field plate design. Moreover, the field plate-dependent electro-thermal behavior of SBD was studied using TCAD computations and experiments. Using the systematic device design approach we have experimentally demonstrated large periphery SBD with 15 A forward current at 5.5 V. [ABSTRACT FROM AUTHOR]
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Song, Xingjuan, Xu, Jingping, and Liu, Lu
IEEE Transactions on Electron Devices . Nov2020, Vol. 67 Issue 11, p5196-5200. 5p.
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FIELD-effect transistors, CHEMICAL vapor deposition, DISCONTINUOUS precipitation, CHARGE carrier mobility, SURFACE roughness, and DIELECTRIC films
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In this article, an effective way of chemical modification on the dielectric surface (Al2O3) is investigated to chemical vapor deposition (CVD)-grown high-quality monolayer MoS2 and the relevant back-gated FETs are fabricated without MoS2 transfer. As a result, the size of the triangle MoS2 is increased and its quality is improved as the surface of Al2O3 is treated by H2SO4. Furthermore, as compared with the gate dielectrics of the SiO2 and as-deposited Al2O3, the fabricated transistor with the H2SO4-treated Al2O3 as gate dielectric achieves better electrical properties: high carrier mobility of 12.9 cm2/Vs (~10 times higher than the untreated sample, ~5.2 times higher than the SiO2 gate-dielectric sample), small subthreshold swing of 110 mV/dec, and high ON/OFF ratio of $3\times 10^{{6}}$. The involved mechanisms are attributed to the fact that the H2SO4-treated Al2O3 not only can increase its surface roughness to promote the nucleation and high-quality growth of MoS2 but also can improve the quality of the MoS2/Al2O3 interface. This simple chemical-modification treatment will open up an effective approach of combining the high-crystallinity CVD-MoS2 with the high- ${k}$ dielectric without MoS2 transfer required. [ABSTRACT FROM AUTHOR]
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