Zeitschriftenartikel: „Interfacial defect“

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Qin, Renyuan, Denvid Lau, Lik-ho Tam, Tiejun Liu, Dujian Zou und Ao Zhou. „Experimental Investigation on Interfacial Defect Criticality of FRP-Confined Concrete Columns“. Sensors 19, Nr. 3 (24.01.2019): 468. http://dx.doi.org/10.3390/s19030468.

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Defects between fiber reinforced polymer (FRP) and repaired concrete components may easily come out due to misoperation during manufacturing, environmental deterioration, or impact from external load during service life. The defects may cause a degraded structure performance and even the unexpected structural failure. Different non-destructive techniques (NDTs) and sensors have been developed to assess the defects in FRP bonded system. The information of linking up the detected defects by NDTs and repair schemes is needed by assessing the criticality of detected defects. In this study, FRP confined concrete columns with interfacial defects were experimentally tested to determine the interfacial defect criticality on structural performance. It is found that interfacial defect can reduce the FRP confinement effectiveness, and ultimate strength and its corresponding strain of column deteriorate significantly if the interfacial defect area is larger than 50% of total confinement area. Meanwhile, proposed analytical model considering the defect ratio is validated for the prediction of stress–strain behavior of FRP confined columns. The evaluation of defect criticality could be made by comparing predicted stress–strain behavior with the original design to determine corresponding maintenance strategies.

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LUCOVSKY, GERALD. „PART I: BOND STRAIN AND DEFECTS AT Si-SiO2 AND DIELECTRIC INTERFACES IN HIGH-k GATE STACKS“. International Journal of High Speed Electronics and Systems 16, Nr. 01 (März 2006): 241–61. http://dx.doi.org/10.1142/s0129156406003631.

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The performance and reliability of aggressively-scaled field effect transistors that include deposited high-k dielectrics and interfacial SiO 2 buffer layers are determined in large part by electronically-active defects and defect precursors at the Si - SiO 2, and internal SiO 2-high-k dielectric interfaces. A crucial aspect of reducing interfacial defects and defect precursors is associated with bond-strain driven bonding self-organizations that take place during high temperature annealing in inert ambients. These interfacial self-organizations, and intrinsic interface defects are addressed through an extension of bond constraint theory from bulk glasses to interfaces between non-crystalline SiO 2, and i) crystalline Si , and ii) non-crystalline and crystalline alternative gate dielectric materials.

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Wei, Jinfeng, Guangnan Xu, Guolin Liu, Jinwei Guo, Wang Zhu und Zengsheng Ma. „Quantitative Characterization of Interfacial Defects in Thermal Barrier Coatings by Long Pulse Thermography“. Coatings 12, Nr. 12 (26.11.2022): 1829. http://dx.doi.org/10.3390/coatings12121829.

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The non-contact long pulse thermography method is commonly used to detect the defects in thermal barrier coatings (TBCs). The profile of interfacial defect in TBCs can be monitored by infrared camera under the irradiation of the excitation source. Unfortunately, the defect profile is always blurry due to heat diffusion between the defect area and the intact area. It is difficult to quantify the size of defect size in TBCs. In this work, combined with derived one-dimensional heat conduction analytical model, a non-contact long pulse thermography (LPT) method is applied to quantitatively investigate the interface defects in TBCs. Principal component analysis (PCA) and background subtraction method are used to improve the contrast of the defect profile in collected thermal images. By fitting the results between the profile of the interface defect in thermal images and the predicted shape of the model, the interface defect size can be determined. Furthermore, a simple extension of proposed method for interfacial defects with irregular shape is presented. The predicted errors for round defect with diameters of 3 mm, 5 mm and 7 mm are roughly distributed in the range of 3%~6%, which are not affected by the defect diameter.

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Zhang, Xin, und Shaoqing Wang. „Interfacial Strengthening of Graphene/Aluminum Composites through Point Defects: A First-Principles Study“. Nanomaterials 11, Nr. 3 (15.03.2021): 738. http://dx.doi.org/10.3390/nano11030738.

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The relationship between point defects and mechanical properties has not been fully understood yet from a theoretical perspective. This study systematically investigated how the Stone–Wales (SW) defect, the single vacancy (SV), and the double vacancy (DV) affect the mechanical properties of graphene/aluminum composites. The interfacial bonding energies containing the SW and DV defects were about twice that of the pristine graphene. Surprisingly, the interfacial bonding energy of the composites with single vacancy was almost four times that of without defect in graphene. These results indicate that point defects enhance the interfacial bonding strength significantly and thus improve the mechanical properties of graphene/aluminum composites, especially the SV defect. The differential charge density elucidates that the formation of strong Al–C covalent bonds at the defects is the most fundamental reason for improving the mechanical properties of graphene/aluminum composites. The theoretical research results show the defective graphene as the reinforcing phase is more promising to be used in the metal matrix composites, which will provide a novel design guideline for graphene reinforced metal matrix composites. Furthermore, the sp3-hybridized C dangling bonds increase the chemical activity of the SV graphene, making it possible for the SV graphene/aluminum composites to be used in the catalysis field.

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Liu, Feng, Yuan Zhu, Ruoyu Wu, Lidan Zhang, Rui Zou, Shengbing Zhou, Huiming Ning, Ning Hu und Cheng Yan. „Interfacial mechanical properties of periodic wrinkled graphene/polyethylene nanocomposite“. Physica Scripta 98, Nr. 8 (31.07.2023): 085955. http://dx.doi.org/10.1088/1402-4896/ace93c.

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Abstract Molecular dynamics simulations have been performed to investigate the interfacial mechanical properties of periodic wrinkled graphene (GR) with polyethylene (PE) matrix. The influences of amplitude (H), wavelength (λ), and vacancy defect for the periodic wrinkled GR on the interfacial mechanical properties were considered and the potential mechanisms were analyzed. The results indicate that the interfacial mechanical properties of GR with periodic wrinkles are superior to that of flat GR, especially when the H / λ = 0.51 the interfacial strength enhances ∼29.3%. Through the radial distribution function (RDF) analysis we found that the stronger interfacial mechanical properties are, the more PE molecular chains are attached to the GR when the GR is separated from the PE matrix. In addition, we found that vacancy defect in periodic wrinkled GR does not always degrade the interfacial mechanical properties, and when the vacancy defect content is 20%, the interfacial mechanical properties can be improved, as the vacancy defect reduces the interfacial distance and increases the roughness of the interface.

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Chen, Yuyun, Yi Shen, Yuanming Chen, Guodong Xu, Yudong Liu und Rui Huang. „Effects of Annealing Temperature on Bias Temperature Stress Stabilities of Bottom-Gate Coplanar In-Ga-Zn-O Thin-Film Transistors“. Coatings 14, Nr. 5 (30.04.2024): 555. http://dx.doi.org/10.3390/coatings14050555.

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Defect annihilation of the IGZO/SiO2 layer is of great importance to enhancing the bias stress stabilities of bottom-gate coplanar thin-film transistors (TFTs). The effects of annealing temperatures (Ta) on the structure of the IGZO/SiO2 layer and the stabilities of coplanar IGZO TFTs were investigated in this work. An atomic depth profile showed that the IGZO/SiO2 layer included an IGZO layer, an IGZO/SiO2 interfacial mixing layer, and a SiO2 layer. Higher Ta had only one effect on the IGZO layer and SiO2 layer (i.e., strengthening chemical bonds), while it had complex effects on the interfacial mixing layer—including weakening M-O bonds (M: metallic elements in IGZO), strengthening damaged Si-O bonds, and increasing O-related defects (e.g., H2O). At higher Ta, IGZO TFTs exhibited enhanced positive bias temperature stress (PBTS) stabilities but decreased negative bias temperature stress (NBTS) stabilities. The enhanced PBTS stabilities were correlated with decreased electron traps due to the stronger Si-O bonds near the interfacial layer. The decreased NBTS stabilities were related to increased electron de-trapping from donor-like defects (e.g., weak M-O bonds and H2O) in the interfacial layer. Our results suggest that although higher Ta annihilated the structural damage at the interface from ion bombardment, it introduced undesirable defects. Therefore, to comprehensively improve electrical stabilities, controlling defect generation (e.g., by using a mild sputtering condition of source/drain electrodes and oxides) was more important than enhancing defect annihilation (e.g., through increasing Ta).

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Bondon, Arnaud, Khalid Lamnawar und Abderrahim Maazouz. „Influence of Copolymer Architecture on Generation of Defects in Reactive Multilayer Coextrusion“. Key Engineering Materials 651-653 (Juli 2015): 836–41. http://dx.doi.org/10.4028/www.scientific.net/kem.651-653.836.

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Several polymers can be combined in one multilayer structure by reactive coextrusion. Tie-layers are often used to compatibilize adjacent layers and may reduce or suppress interfacial instabilities and defects in multilayer coextrusion flow. However, a new additional defect defined as “grainy” defect can be observed. In our best of knowledge, no study in literature has been dedicated to understand its origin. The phenomena are quite complex due to the coupling of the effects of flow and the physico-chemical mechanisms at the interface. The aim of this work is to understand the relationship between the instabilities and defects encountered in multilayer coextruded films and the role of the copolymer formed in-situ between tie and barrier layers. Polyamide 6 (PA6) and ethylene-vinyl alcohol copolymer (EVOH) were used as barrier layers sandwiched in polypropylene (PP) with or without tie-layer based on polypropylene grafted maleic anhydride (PP-g-MA). Influence of process parameters and nature of the polymer pair on the generation of “grainy” defect has been assessed and related to the rheological and the physico-chemical properties of layers. These experiments showed that this defect appeared mainly in the compatibilized EVOH system and could be distinguished from the usual coextrusion instabilities. Interfacial properties between tie and barrier layers have been investigated. Shear stress relaxation experiments have been carried out on reactive tie/barrier bilayers. Due to the interphase generated in-situ, the relaxation behavior was altered by extending the relaxation time. Investigation of interfacial morphology highlighted that the copolymer architecture significantly affected the interface/interphase development and interface roughness. Hence, relationships between relaxation process, interfacial morphology and copolymer structure were correlated with the generation of grainy defects in coextrusion.

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Kim, Jin Mo, und Sung Won Hwang. „Bipolar Resistive Switching Behavior of PVP-GQD/HfOx/ITO/Graphene Hybrid Flexible Resistive Random Access Memory“. Molecules 26, Nr. 22 (09.11.2021): 6758. http://dx.doi.org/10.3390/molecules26226758.

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We have investigated highly flexible memristive devices using reduced graphene oxide (RGO) nanosheet nanocomposites with an embedded GQD Layer. Resistive switching behavior of poly (4-vinylphenol):graphene quantum dot (PVP:GQD) composite and HfOx hybrid bilayer was explored for developing flexible resistive random access memory (RRAM) devices. A composite active layer was designed based on graphene quantum dots, which is a low-dimensional structure, and a heterogeneous active layer of graphene quantum dots was applied to the interfacial defect structure to overcome the limitations. Increasing to 0.3–0.6 wt % PVP-GQD, Vf changed from 2.27–2.74 V. When negative deflection is applied to the lower electrode, electrons travel through the HfOx/ITO interface. In addition, as the PVP-GQD concentration increased, the depth of the interfacial defect decreased, and confirmed the repetition of appropriate electrical properties through Al and HfOx/ITO. The low interfacial defects help electrophoresis of Al+ ions to the PVP GQD layer and the HfOx thin film. A local electric field increase occurred, resulting in the breakage of the conductive filament in the defect.

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Pond, R. C. „TEM studies of line defects in interfaces“. Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 586–87. http://dx.doi.org/10.1017/s0424820100104996.

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Line defects are ubiquitious features in interfaces, and have important structural and mechanistic role. Recently, a crystallographic theory of such defects has been presented which appears to offer a comprehensive framework for their classification. The object of the present paper is firstly to outline the characterisation and classification of defects according to this treatment. Secondly, we illustrate examples of defects in the distinctive classes observed using tern, and discuss the various imaging techniques which have been employed.In the absence of a rigorous treatment of line defects in single crystals and interfaces, which would require the development of a discrete field theory, approximate methods of defect characterisation are used. The most popular method involves mapping a contour, initially constructed around a defect of interest, into a reference space. For defeats in single crystals this Burgers circuit method, introduced by Frank, is very helpful, but suffers from certain procedural inconveniences in the case of interfacial defects.

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Zhou, Mingjian, Liqing Liu, Jiahao Liu und Zihang Mei. „Prediction and Control of Thermal Transport at Defective State Gr/h-BN Heterojunction Interfaces“. Nanomaterials 13, Nr. 9 (25.04.2023): 1462. http://dx.doi.org/10.3390/nano13091462.

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The control of interfacial thermal conductivity is the key to two−dimensional heterojunction in semiconductor devices. In this paper, by using non−equilibrium molecular dynamics (NEMD) simulations, we analyze the regulation of interfacial thermal energy transport in graphene (Gr)/hexagonal boron nitride (h-BN) heterojunctions and reveal the variation mechanism of interfacial thermal energy transport. The calculated results show that 2.16% atomic doping can effectively improve interfacial heat transport by more than 15.6%, which is attributed to the enhanced phonon coupling in the mid−frequency region (15–25 THz). The single vacancy in both N and B atoms can significantly reduce the interfacial thermal conductivity (ITC), and the ITC decreases linearly with the increase in vacancy defect concentration, mainly due to the single vacancy defects leading to an increased phonon participation rate (PPR) below 0.4 in the low-frequency region (0–13 THz), which shows the phonon the localization feature, which hinders the interfacial heat transport. Finally, a BP neural network algorithm is constructed using machine learning to achieve fast prediction of the ITC of Gr/h-BN two-dimensional heterogeneous structures, and the results show that the prediction error of the model is less than 2%, and the method will provide guidance and reference for the design and optimization of the ITC of more complex defect-state heterogeneous structures.

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Cheng, Linan, und Xiangming Chen. „Analysis of interfacial de-bonding failure on stiffened composite panel“. Journal of Physics: Conference Series 2553, Nr. 1 (01.08.2023): 012026. http://dx.doi.org/10.1088/1742-6596/2553/1/012026.

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Abstractor This article aimed at the interfacial de-bonding between the stringer and skin when the structure is under post-buckling loads. A four-point bending test was set up, and the cohesive zone model (CZM) was employed considering the effects of through-thickness compression on the inter-laminar shear failure of composite laminates. The numerical result is in good agreement with the experimental one. The results indicate that: embedded defect at the flange/skin interface has a slight influence on the load capacity of the structure, but embedded defect at the flange/radius-filler interface has a significant influence on the load capacity of the structure, and delamination always initiated at the flange/radius-filler interface. The presence of inner corner defects in the filled area has a greater impact on the load capacity of the structure, the load capacity is in direct proportion to the width of corner defects.

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Wu, Zhishen, Ping Zhou, Kikuzirou Tanabe und Nishizawa. „Interfacial Defect Detection Using Laser Doppler Velocitometer“. Concrete Research and Technology 12, Nr. 1 (2001): 13–21. http://dx.doi.org/10.3151/crt1990.12.1_13.

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Bian, Zeqi, Bin Wu, Bing Liu, Yan Lyu, Jie Gao und Cunfu He. „Characterization of Bonding Defects in Fiber-Reinforced Polymer-Bonded Structures Based on Ultrasonic Transmission Coefficient“. Materials 17, Nr. 5 (27.02.2024): 1080. http://dx.doi.org/10.3390/ma17051080.

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This research delves into the characterization of the ultrasonic transmission coefficient pertaining to various types of bonding defects in Fiber-Reinforced Polymer (FRP)-bonded structures. Initially, an ultrasonic transmission coefficient calculation model for FRP-bonded structures in a water immersion environment is established. This model is used to analyze the variation in the ultrasonic transmission coefficient under different defect types, namely intact bonding, interfacial slip, and debonding defects. Subsequently, a frequency domain finite element analysis model of FRP-bonded structures with different defect types is constructed. The simulation validates the accuracy of the theoretical analysis results and concurrently analyzes the variation in the transmission signal when the defects alter. Lastly, an experimental platform for water immersion ultrasonic transmission measurement is set up. The transmission signals under different defect types are extracted through experiments and evaluated in conjunction with theoretical calculations to assess the types of bonding defects.

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Edelman, Piotr, Dmitriy Marinskiy, Alexander Savtchouk, John D'Amico, Andrew Findlay, Marshall Wilson, Carlos Almeida und Jacek Lagowski. „Non-Visual Defect Monitoring with Surface Voltage Mapping: Application for Semiconductor IC and PV Technology“. Solid State Phenomena 242 (Oktober 2015): 472–77. http://dx.doi.org/10.4028/www.scientific.net/ssp.242.472.

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Non Visual Defects (NVD) is a category of defects that cause electrical failures but are not detected with visual wafer inspection tools. Our approach for NVD detection is based on the Kelvin probe surface voltage mapping technique. The detection of defects is enhanced using field-effect created in a non-contact manner by corona charge deposition on the surface of semiconductor. Precise defect location is accomplished with surface voltage gradient magnitude mapping that enhances delineation of defects. Detected defects are characterized locally using the corona-voltage technique or isothermal voltage transient decay analysis. Presented examples include: dielectric charge and interfacial defect mapping on 300mm Si wafers; deep level emission mapping on epitaxial SiC and mobile ion mapping in Si solar cells.

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Cheng, Tin Kei, und Denvid Lau. „A photophone-based remote nondestructive testing approach to interfacial defect detection in fiber-reinforced polymer-bonded systems“. Structural Health Monitoring 17, Nr. 2 (12.01.2017): 135–44. http://dx.doi.org/10.1177/1475921716686772.

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Externally bonded fiber-reinforced polymer is an increasingly popular material to be used in strengthening and retrofitting aging structures. In such structures, debonding defects may occur at or near the interface between fiber-reinforced polymer and concrete. As such debonding in fiber-reinforced polymer-bonded systems is generally brittle in nature, there is a need of a reliable inspection technique that can provide early warning of interfacial defects such that premature failure of fiber-reinforced polymer-strengthened structures can be avoided. A remote nondestructive testing approach based on the working principle of a photophone is presented here as an economical alternative to laser Doppler vibrometry for detecting interfacial defects. Concrete specimens retrofitted with fiber-reinforced polymer are excited acoustically by white noise, while the surface of the structure is illuminated by a light source. If an interfacial defect exists beneath the surface, the surface will exhibit a frequency response different from an intact surface. The surface of the fiber-reinforced polymer portrays the role of flexible mirror in a photophone, which encodes information about surface vibration into amplitude-modulated light signal. A light detector then captures the irradiance of the reflected beam, and the amplitude modulation is converted into frequency domain in post-processing. With this technique, defect dimensions and thus damage extent can be inferred from the frequency spectrum obtained. The obtained results correspond well with the theoretical calculation, demonstrating the robustness and the applicability of the proposed technique in civil infrastructure.

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Stemmer, S., G. Duscher, E. M. James, M. Ceh und N. D. Browning. „Atomic Scale Structure-Property Relationships of Defects and Interfaces in Ceramics“. Microscopy and Microanalysis 4, S2 (Juli 1998): 556–57. http://dx.doi.org/10.1017/s143192760002290x.

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The evaluation of the two dimensional projected atom column positions around a defect or an interface in an electronic ceramic, as it has been performed in numerous examples by (quantitative) conventional high-resolution electron microscopy (HRTEM), is often not sufficient to relate the electronic properties of the material to the structure of the defect. Information about point defects (vacancies, impurity atoms), and chemistry or bonding changes associated with the defect or interface is also required. Such complete characterization is a necessity for atomic scale interfacial or defect engineering to be attained.One instructive example where more than an image is required to understand the structure property relationships, is that of grain boundaries in Fe-doped SrTi03. Here, the different formation energies of point defects cause a charged barrier at the boundary, and a compensating space charge region around it. The sign and magnitude of the barrier depend very sensitively on the atomic scale composition and chemistry of the boundary plane.

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Sun, Dong, und Yong Wei. „Simulation Research on Air-Coupled Ultrasonic Detection of Layered Composite Interface Defects Using Matlab Computer Software“. Science of Advanced Materials 14, Nr. 6 (01.06.2022): 1116–23. http://dx.doi.org/10.1166/sam.2022.4320.

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In this paper, a mathematical model and a finite element model are established to describe the dispersion characteristics of acoustic modes in a two-layer medium. Air-coupled ultrasound was used to detect interfacial defects in a laminated composite. An appropriate excitation signal was simulated to locate interface defects by both MATLAB (for the numerical model) and ANSYS (for the finite element model) software tools. The results confirmed that the mode of the excitation wave was consistent with the materials of the layered structure, which ensured propagation of the wave into each layer whereas avoiding the phenomenon of total reflection that prevents complete detection of the interfacial adhesive properties in the layered composite structure. This study demonstrates that the size of an interface defect should be simulated interchangeably using both MATLAB and ANSYS software. As such, it is feasible to detect the interfacial quality of laminated composites by air-coupled ultrasonic waves.

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Kulkova, Svetlana E., Alexander V. Bakulin, Q. M. Hu und Rui Yang. „Study of Nickel Segregation at the TiNi-Titanium Oxide Interface“. Materials Science Forum 738-739 (Januar 2013): 269–73. http://dx.doi.org/10.4028/www.scientific.net/msf.738-739.269.

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Ab-intio investigations of atomic and molecular oxygen on TiNi(110) surface are performed by using the projector augmented wave method with generalized gradient approximation for the exchange-correlation functional. Our results confirm the formation of a Ni-rich interface TiO2(100)/TiNi(110), for which the formation energies (Hf) of point defects at the interfacial layers were estimated. It is shown that Hf of swap Ti-Ni defect has a lower energy than that for the Ni antisites at the interfacial layers. The formation energies of point defects in bulk TiNi, monoclinic TiO, and rutile TiO2 are also calculated. Our results demonstrate that Hf of Ni-antisites in TiO is twice less than that in TiO2. The formation of small Ni clusters is also discussed.

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Huang, Wenhuan, Wenming Gao, Shouwei Zuo, Luxi Zhang, Ke Pei, Panbo Liu, Renchao Che und Huabin Zhang. „Hollow MoC/NC sphere for electromagnetic wave attenuation: direct observation of interfacial polarization on nanoscale hetero-interfaces“. Journal of Materials Chemistry A 10, Nr. 3 (2022): 1290–98. http://dx.doi.org/10.1039/d1ta09357f.

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In situ constructing hetero-interface, and revealing its interfacial polarization is challenging. Here, the Mo defect-induced interfacial polarization on MoC(−)/NC(+) interface was clarified, and for the first time, directly observed by hologram.

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Sadowski, Marcel, Sabrina Sicolo und Karsten Albe. „Defect thermodynamics and interfacial instability of crystalline Li4P2S6“. Solid State Ionics 319 (Juni 2018): 53–60. http://dx.doi.org/10.1016/j.ssi.2018.01.047.

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Scheerlinck, T., J. Broos, D. Janssen und N. Verdonschot. „Mechanical implications of interfacial defects between femoral hip implants and cement: A finite element analysis of interfacial gaps and interfacial porosity“. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine 222, Nr. 7 (01.10.2008): 1037–47. http://dx.doi.org/10.1243/09544119jeim362.

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Two types of defect between femoral hip implants and cement have been identified. Interfacial porosity arises from cement shrinkage during curing and presents as pores randomly located along the stem. Interfacial gaps are much larger stem—cement separations caused by air introduced during stem insertion. To investigate the mechanical consequences of both types of defect, a finite element analysis model was created on the basis of a computed tomography image of a Charnley—Kerboul stem, and alternating torsional and transverse loads were applied. The propagation of fatigue cracks within the cement and the rotational stability of the stem were assessed in models simulating increasing amounts of interfacial gaps and pores. Anterior gaps covering at least 30 per cent of the implant surface promoted cement cracks and destabilized the stem. Anterolateral gaps were less destabilizing, but had more potential to promote cracks. In both cases, cracks occurred mainly outside gap regions, in areas where the stem contacted the cement during cyclic loading. Although random interfacial pores did not destabilize the implant, they acted as crack initiators even at low fractions (10 per cent). In conclusion, random interfacial pores were more harmful for the cement mantle integrity than were larger regions of interfacial gaps, although gaps were more detrimental for the rotational stability of the stem.

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Demir, I., und H. M. Zbib. „The Interface Ring Dislocation in Fiber-Matrix Composites: Approximate Analytical Solution“. Journal of Engineering Materials and Technology 116, Nr. 3 (01.07.1994): 279–85. http://dx.doi.org/10.1115/1.2904287.

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An analytical solution for the extended stress field of the fundamental problem of interfacial Somigliana ring dislocation in fiber-matrix composites is obtained. The result of this work provides a powerful tool which can be used to address a class of three-dimensional defect problems encountered in heterogeneous materials, such as fiber-matrix debonding, fiber pull-out, broken fibers and others, as well as interaction among defects.

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Yao, Wenjuan, und Lei Fan. „Defects in Graphene/h-BN Planar Heterostructures: Insights into the Interfacial Thermal Transport Properties“. Nanomaterials 11, Nr. 2 (16.02.2021): 500. http://dx.doi.org/10.3390/nano11020500.

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In this work, the defects (local stress generated) induce the formation of graphene/h-BN planar heterostructure (Gr-hBN-PH) to form "unsteady structure". Then, the coupling effects of external field (heat flow direction, strain and temperature field) and internal field (defect number, geometry shape and interfacial configuration) on the interface thermal conductivity (ITC) of Gr-hBN-PH were studied. The results show phonon transmission is less affected by compression deformation under the action of force-heat-defect coupling, while phonon transmission of heterostructure is more affected by tensile deformation. The non-harmonic interaction of the atoms in the composite system is strengthened, causing the softening of high-frequency phonons. The greater reduction of thermal transport at the interface of heterostructures will be. The interface bonding morphology plays a significant role on the ITC of the Gr-hBN-PH. The relationship between structure and properties in the low dimension is analyzed from the perspective of defect energy. It is helpful for us to understand the physical mechanism of low-dimensional structure, realize multiple structural forms, and even explore new uses.

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Gao, Yuanji, Xiangxiang Feng, Jianhui Chang, Caoyu Long, Yang Ding, Hengyue Li, Keqing Huang, Biao Liu und Junliang Yang. „Surface ion exchange and targeted passivation with cesium fluoride for enhancing the efficiency and stability of perovskite solar cells“. Applied Physics Letters 121, Nr. 7 (15.08.2022): 073902. http://dx.doi.org/10.1063/5.0097939.

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Interfacial defects greatly influence the performance of perovskite solar cells (PSCs), and interface engineering is a powerful technique to promote the power conversion efficiency (PCE) of PSCs. Herein, an interfacial passivation strategy is developed employing cesium fluoride (CsF) to modify the surface of a perovskite film. Theoretical calculations suggest that the Cs+ and F− ions have a targeted passivation effect to decrease the defect density of the perovskite. Meanwhile, Cs+-formamidine+ (FA+) and F−–I− ion exchange can occur on the perovskite surface, which leads to the decline of the Fermi level of perovskite and reinforces the built-in potential of PSCs. Additionally, experiment results also confirm the reduction in the interfacial defects and the enhancement of the built-in potential. Consequently, the open-circuit voltage ( Voc) of PSCs is increased from 1.07 to 1.12 V, contributing to the promotion of the PCE. Furthermore, the stability of PSCs is obviously improved as well owing to the suppressed phase transition of α-phase perovskite. Our findings provide guidelines for surface modification of perovskite crystals to enhance the performance and stability of PSCs.

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Tang, Qing-Ju, Tao Zhang, Zhuo-Yan Gu und Chi-Wu Bu. „Infrared thermal wave detection of interfacial debonding defects of thermal barrier coatings based on non-linear frequency modulation“. Thermal Science 27, Nr. 1 Part B (2023): 705–11. http://dx.doi.org/10.2298/tsci2301705t.

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In order to improve the reliability of detecting the debonding defects at the interface of thermal barrier coatings (TBC), a non-linear frequency modulated (NLFM) infrared thermal wave detection method is proposed. A NLFM infrared thermal wave detection system is built, and zirconia TBC specimens are prepared and tested. The effects of defect diameter, excitation power, initial frequency and termination frequency on the defect detection effect are analyzed. Three algorithms such as principal component analysis (PCA) are used to process the image sequence, and the signal-to-noise ratio (SNR) of each sequence processing algorithm is calculated and compared. The results show that the larger the diameter of the defect, the easier it is to be detected, and the appropriate adjustment of the excitation power or the reduction of the initial and termination frequencies is beneficial to the detection of defects. Compared with the other two algorithms, the PCA method is more effective for image sequence processing. It offers a reference for detecting debonding flaws at the TBC interface.

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Jiang, Cui Xiang, und Rui Li. „Single Fiber Testing Study the Mechano-Electric Behavior between Carbon Fiber and Cement“. Advanced Materials Research 183-185 (Januar 2011): 1859–63. http://dx.doi.org/10.4028/www.scientific.net/amr.183-185.1859.

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The mechano-electric behavior between carbon fiber and cement matrix was revealed by single fiber testing. The resistance between fiber and matrix was found to increase when the interfacial bonding force increased and decrease when the interfacial bonding force decreased under dynamic load, which exhibited good reversibility except the first loading. The irreversibly increasing resistance is associated with interface debonding due to the interfacial defect, and the reversibly increasing resistance is attributed to elastic deformation of interfacial structure. The interfacial shear stresses cause the change of interfacial structure, which produce an effect on conductive network of the complex, and lead to the change of resistance between fiber and matrix.

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Xie, Sujing, George E. Sterbinsky, Bruce W. Wessels und Vinayak P. Dravid. „Defect and Interfacial Structure of Heteroepitaxial Fe3O4/BaTiO3 Bilayers“. Microscopy and Microanalysis 16, Nr. 3 (09.04.2010): 300–305. http://dx.doi.org/10.1017/s1431927610000255.

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AbstractThe defect and interfacial structure in a Fe3O4/BaTiO3 heteroepitaxial bilayer was investigated by scanning transmission electron microscopy. The results show that the Fe3O4 film grew epitaxially on BaTiO3. The orientation relationship between Fe3O4, BaTiO3 and MgO is [100]Fe3O4//[100]BaTi3O//[100]MgO and (010)Fe3O4//(010)BaTiO3//(010)MgO. An initial interfacial nucleation layer was formed that partially accommodated the lattice mismatch strain between BaTiO3 and MgO. This investigation indicates that the formation of this buffer layer provides a high-quality BaTiO3 surface for subsequent Fe3O4 growth, resulting in a semicoherent interface. The Fe3O4 surface is nearly atomically abrupt (roughness Rrms = 0.78 nm). The Fe3O4 film exhibits magnetic domains with a diameter in the range of 0.4–2 μm.

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Laxman, Karthik, Tanujjal Bora, Salim H. Al-Harthi und Joydeep Dutta. „Improved Sensitization of Zinc Oxide Nanorods by Cadmium Telluride Quantum Dots through Charge Induced Hydrophilic Surface Generation“. Journal of Nanomaterials 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/919163.

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This paper reports on UV-mediated enhancement in the sensitization of semiconductor quantum dots (QDs) on zinc oxide (ZnO) nanorods, improving the charge transfer efficiency across the QD-ZnO interface. The improvement was primarily due to the reduction in the interfacial resistance achieved via the incorporation of UV light induced surface defects on zinc oxide nanorods. The photoinduced defects were characterized by XPS, FTIR, and water contact angle measurements, which demonstrated an increase in the surface defects (oxygen vacancies) in the ZnO crystal, leading to an increase in the active sites available for the QD attachment. As a proof of concept, a model cadmium telluride (CdTe) QD solar cell was fabricated using the defect engineered ZnO photoelectrodes, which showed ∼10% increase in photovoltage and ∼66% improvement in the photocurrent compared to the defect-free photoelectrodes. The improvement in the photocurrent was mainly attributed to the enhancement in the charge transfer efficiency across the defect rich QD-ZnO interface, which was indicated by the higher quenching of the CdTe QD photoluminescence upon sensitization.

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Yu, Bin-Bin, Xuanang Hu, Haijun Wang, Qihua Liang, Liaoyu Wang, Yinghui Wu, Qi Qin und Long-Biao Huang. „Improved perovskite triboelectric nanogenerators by effective defect passivation and interface modulation“. Applied Physics Letters 122, Nr. 13 (27.03.2023): 133902. http://dx.doi.org/10.1063/5.0142055.

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Perovskite-based triboelectric nanogenerators (TENGs) have obtained wide attention and investigation due to their excellent dielectric and electrical properties, as well as the diversity of perovskite materials. In this work, phenethyl ammonium iodide (PEAI) was applied to tailor the interface of MAPbI3 films, to form a 2D/3D heterojunction, and to passivate defects of films. The TENGs after PEAI passivation achieved significant improvement in voltage and current density with an increase in the output voltage from 33.3 to 40.1 V, and the current density was improved from 9.1 to 10.1 mA/m2. The improved output properties might be attributed to changes in the triboelectric charge density, carrier mobility, reduced interfacial combination by effective defect passivation, and favorable charge transporting by constructing 2D/3D heterojunctions for the effect of the built-in electric field. This work demonstrates that interfacial modification is one of the feasible methods for improving the performance of TENGs and supplies further possibilities for high-performance perovskite-based TENGs.

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Ourmazd, A., M. Scheffler, M. Heinemann und J.-L. Rouviere. „Microscopic Properties of Thin Films: Learning About Point Defects“. MRS Bulletin 17, Nr. 12 (Dezember 1992): 24–32. http://dx.doi.org/10.1557/s0883769400046923.

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Microscopic properties of thin films are often strongly influenced by departures from “perfection.” These can take the form of extended defects such as dislocations, interfacial roughness, or point defects. Direct imaging of extended defects was one of the early contributions of electron microscopy to solid-state science. Since then, the role of extended defects in controlling the fabrication and properties of thin films has been extensively studied and reviewed. Recently, in-situ observation of strain relaxation in thin-film structures has increased our understanding of dislocation kinetics and its effect on properties of thin films.In this article, we focus on electron microscopic studies of interfacial roughness, the effect of processing on thin films, and the role and properties of intrinsic point defects in solids. Concurrent development of sophisticated theoretical and experimental approaches has substantially facilitated the investigation of point-defect properties. Here, we illustrate how results from theory and experiment can be combined to form a detailed picture of point-defect diffusion in solids, and highlight areas needing increased attention. Microscopic properties of thin films cannot be covered in a single review. For this reason, and because fabrication of semiconducting thin films has reached unprecedented levels of sophistication, we illustrate this article with references to semiconducting materials.Our main conclusions can be summarized as follows, (a) Thin films of the highest quality are bounded by interfaces that are microscopically rough. Moreover, thin-film interfaces contain roughness on many length scales, each affecting a subset of the physical properties of interest.

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Yang, Menghao, und Yifei Mo. „Interfacial Defect of Lithium Metal in Solid‐State Batteries“. Angewandte Chemie International Edition 60, Nr. 39 (20.08.2021): 21494–501. http://dx.doi.org/10.1002/anie.202108144.

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Yang, Menghao, und Yifei Mo. „Interfacial Defect of Lithium Metal in Solid‐State Batteries“. Angewandte Chemie 133, Nr. 39 (20.08.2021): 21664–71. http://dx.doi.org/10.1002/ange.202108144.

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Komninou, Ph, Th Kehagias, J. Kioseoglou, G. P. Dimitrakopulos, A. Sampath, T. D. Moustakas, G. Nouet und Th Karakostas. „Interfacial and defect structures in multilayered GaN/AlN films“. Journal of Physics: Condensed Matter 14, Nr. 48 (22.11.2002): 13277–83. http://dx.doi.org/10.1088/0953-8984/14/48/378.

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Huang, Shuai, Lian Duan und Dongdong Zhang. „Synergistic optimization of interfacial energy-level alignment and defect passivation toward efficient annealing-free inverted polymer solar cells“. Journal of Materials Chemistry A 8, Nr. 36 (2020): 18792–801. http://dx.doi.org/10.1039/d0ta05696k.

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Mannan, Hafiz Abdul, Alamin Idris, Rizwan Nasir, Hilmi Mukhtar, Danial Qadir, Humbul Suleman und Abdul Basit. „Interfacial Tailoring of Polyether Sulfone-Modified Silica Mixed Matrix Membranes for CO2 Separation“. Membranes 12, Nr. 11 (11.11.2022): 1129. http://dx.doi.org/10.3390/membranes12111129.

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In this work, in situ polymerization of modified sol-gel silica in a polyether sulfone matrix is presented to control the interfacial defects in organic-inorganic composite membranes. Polyether sulfone polymer and modified silica are used as organic and inorganic components of mixed matrix membranes (MMM). The membranes were prepared with different loadings (2, 4, 6, and 8 wt.%) of modified and unmodified silica. The synthesized membranes were characterized using Field emission electron scanning microscopy, energy dispersive X-ray, Fourier transform infrared spectroscopy, thermogravimetric analyzer, and differential scanning calorimetry. The performance of the membranes was evaluated using a permeation cell set up at a relatively higher-pressure range (5–30 bar). The membranes appear to display ideal morphology with uniform distribution of particles, defect-free structure, and absence of interfacial defects such as voids and particle accumulations. Additionally, the CO2/CH4 selectivity of the membrane increased with the increase in the modified silica content. Further comparison of the performance indicates that PES/modified silica MMMs show a promising feature of commercially attractive membranes. Therefore, tailoring the interfacial morphology of the membrane results in enhanced properties and improved CO2 separation performance.

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Tay, A. A. O., K. H. Lee und K. M. Lim. „Numerical Simulation of Delamination in IC Packages Using a New Variable-Order Singular Boundary Element“. Journal of Electronic Packaging 125, Nr. 4 (01.12.2003): 569–75. http://dx.doi.org/10.1115/1.1604803.

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Delamination of interfaces in integrated circuit (IC) packages gives rise to electrical and mechanical failures such as popcorn cracking. Hence it is important to be able to analyze the mechanics of delamination from small interfacial defects which may exist at interfaces due to contamination or random factors. This paper describes the mechanics of interfacial delamination and the application of the boundary element method to analyze delamination propagation at interfaces. Now, a crack tip at an interface between two materials has an order of singularity which is a function of the material properties. For an accurate analysis, a special variable-order singular boundary element has been developed and used. The effect of defect size and location along the pad-encapsulant interface on interfacial delamination has been studied. It was found that the energy release rate or stress intensity factor increases with defect size as well as proximity to the pad corner. This implies that when a small delamination near a pad corner delaminates the crack tip nearer the pad corner will propagate first. The analysis has also shown that this delamination, once started, will continue until the crack tip reaches the pad corner. If the variation of interface toughness as a function of mode mixity is known, the delamination propagation behavior can be determined. Depending on the shape of the curve describing the variation of interface toughness with mode mixity, the delamination growth can either be stable, catastrophic, or initially unstable followed by stable growth.

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Sun, Chi, Zhanyi Cao, Yanzhu Jin, Hongyu Cui, Chenggang Wang, Feng Qiu und Shili Shu. „Numerical Simulation of Lost-Foam Casting for Key Components of A356 Aluminum Alloy in New Energy Vehicles“. Materials 17, Nr. 10 (15.05.2024): 2363. http://dx.doi.org/10.3390/ma17102363.

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The intricate geometry and thin walls of the motor housing in new energy vehicles render it susceptible to casting defects during conventional casting processes. However, the lost-foam casting process holds a unique advantage in eliminating casting defects and ensuring the strength and air-tightness of thin-walled castings. In this paper, the lost-foam casting process of thin-walled A356 alloy motor housing was simulated using ProCAST software (2016.0). The results indicate that the filling process is stable and exhibits characteristics of diffusive filling. Solidification occurs gradually from thin to thick. Defect positions are accurately predicted. Through analysis of the defect volume range, the optimal process parameter combination is determined to be a pouring temperature of 700 °C, an interfacial heat transfer coefficient of 50, and a sand thermal conductivity coefficient of 0.5. Microscopic analysis of the motor housing fabricated using the process optimized through numerical simulations reveals the absence of defects such as shrinkage at critical locations.

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Ao, Lei, und Zhihua Xiong. „Insights into the vacancy behaviour at the interface of As–Sb lateral heterostructures“. Journal of Materials Chemistry C 8, Nr. 2 (2020): 650–62. http://dx.doi.org/10.1039/c9tc05395f.

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Mandal, Balaji P., P. Anithakumari, Sandeep Nigam, Chiranjib Majumder, Manoj Mohapatra und Avesh K. Tyagi. „Enhancement of dielectric constant in a niobium doped titania system: an experimental and theoretical study“. New Journal of Chemistry 40, Nr. 11 (2016): 9526–36. http://dx.doi.org/10.1039/c6nj00176a.

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Ma, G.-H. M., Y. H. Lee und J. T. Glass. „Electron microscopic characterization of diamond films grown on Si by bias-controlled chemical vapor deposition“. Journal of Materials Research 5, Nr. 11 (November 1990): 2367–77. http://dx.doi.org/10.1557/jmr.1990.2367.

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Diamond films grown by Bias-Controlled Hot Filament Chemical Vapor Deposition (BCCVD) on silicon (Si) substrates were characterized by Transmission Electron Microscopy (TEM). Both plan-view and cross-sectional TEM samples were made from diamond films grown under different biasing conditions. It was found that defect densities in the films were substantially reduced under zero and reverse bias (substrate negative relative to the filament) as compared to forward bias. Furthermore, the diamond/Si interface of the reverse and zero bias films consisted of a single thin interfacial layer whereas multiple interfacial layers existed at the diamond/Si interface of films grown under forward (positive) bias. Tungsten (W) contamination was also found in the interfacial layers of forward bias films. It is concluded that forward biasing in the present condition is not favorable for growing high quality, low defect density, diamond films. The possible mechanisms which induced the microstructural differences under different biasing conditions are discussed.

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BERSUKER, G., D. VEKSLER, C. D. YOUNG, H. PARK, W. TAYLOR, P. KIRSCH, R. JAMMY, L. MORASSI, A. PADOVANI und L. LARCHER. „CONNECTING ELECTRICAL AND STRUCTURAL DIELECTRIC CHARACTERISTICS“. International Journal of High Speed Electronics and Systems 20, Nr. 01 (März 2011): 65–79. http://dx.doi.org/10.1142/s0129156411006416.

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An attempt is made to correlate electrical measurement results to specific defects in the dielectric stacks of high-k/metal gate devices. Defect characteristics extracted from electrical data were compared to those obtained by ab initio calculations of the dielectric structures. It is demonstrated that oxygen vacancies in a variety of charge states and configurations in the interfacial SiO2layer of the high-k gate stacks contribute to random telegraph noise signal, time-dependent dielectric breakdown, and the flatband voltage roll-off phenomenon.

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Li, Maoyuan, Peng Chen, Bing Zheng, Tianzhengxiong Deng, Yun Zhang, Yonggui Liao und Huamin Zhou. „Effect of Stone-Wales Defect on Mechanical Properties of Gr/epoxy Nanocomposites“. Polymers 11, Nr. 7 (01.07.2019): 1116. http://dx.doi.org/10.3390/polym11071116.

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Due to its superior mechanical properties, graphene (Gr) has the potential to achieve high performance polymer-based nanocomposites. Previous studies have proved that defects in the Gr sheets could greatly reduce the mechanical properties of Gr, while the Stone-Wales (SW) defect was found to enhance the interfacial mechanical strength between Gr and epoxy. However, the combined effects of defects on the overall mechanical properties of Gr/epoxy nanocomposites have not been well understood. In this paper, the effect of the SW defect on the mechanical properties of Gr/epoxy nanocomposites was systematically investigated by using molecular dynamic simulations. The simulation results showed that the SW defect would degrade the mechanical properties of nanocomposites, including the Young’s modulus and in-plane shear modulus. Surprisingly, the transverse shear modulus could be remarkably enhanced with the existence of SW. The reinforcing mechanisms were mainly due to two aspects: (1) the SW defect could increase the surface roughness of the Gr, preventing the slippage between Gr and epoxy during the transverse shea; and (2) the nanocomposite with defective Gr enables a higher interaction energy than that with perfect graphene. Additionally, the effects of temperature, the dispersion and volume fraction of Gr were also investigated.

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Oba, Fumiyasu, Hirohiko Adachi und Isao Tanaka. „Energetics and electronic structure of point defects associated with oxygen excess at a tilt boundary of ZnO“. Journal of Materials Research 15, Nr. 10 (Oktober 2000): 2167–75. http://dx.doi.org/10.1557/jmr.2000.0312.

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The formation energies and electronic structure of zinc vacancies and oxygen interstitials at a tilt boundary of ZnO were investigated by a combination of static lattice and first-principles molecular orbital methods. For both of the defect species, the formation energies were lower than those of the bulk defects at certain sites in the grain boundary. The defects with low formation energies formed electronic states close to the top of the valence band. The interfacial electronic states observed experimentally in ZnO varistors cannot be explained solely by the point defects associated with the oxygen excess: the effects of impurities should be significant for the states.

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Cao, Xueying, Bari Wulan, Baohua Zhang, Dongxing Tan und Jintao Zhang. „Defect evolution of hierarchical SnO2 aggregates for boosting CO2 electrocatalytic reduction“. Journal of Materials Chemistry A 9, Nr. 26 (2021): 14741–51. http://dx.doi.org/10.1039/d1ta03530d.

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Zhu, Lei, Yongshan Qin, Yulong Zhao und Jian Song. „Optimization of Perovskite-Solar-Cells with AlO_x Passivated NiO_x Hole-Transport-Film“. Journal of Nanoelectronics and Optoelectronics 18, Nr. 5 (01.05.2023): 527–33. http://dx.doi.org/10.1166/jno.2023.3434.

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Perovskite solar cells have good photoelectric performance and simple fabrication process which received extensive attention in recent years. However, defects-induced carrier recombination strictly inhibits the photovoltaic performance of the device. This paper proposes a simple, fast and efficient interfacial passivation strategy based on sol–gel micro-reaction. The AlOx nanoparticles deposition at NiOx/perovskite interface reduces defect density providing inverted planar PVCs. The influence of aluminum sec-butoxide concentration on the morphology and optical properties of hole-transport layers discovered the internal relationship between the passivation parameters and the carrier transport process at NiOx/perovskite interface. This breakthrough investigation shows the increase in photoelectric efficiency from 12.26% to 14.54% and the retention efficiency from 63% to 72% after 240 h. Therefore, this feasible experiment for interfacial regulation and passivation for PSCs is a gate to new discoveries.

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Lu, Jiangfeng, Xu Zhang, Lusheng Xu, Guoliang Zhang, Jiuhan Zheng, Zhaowei Tong, Chong Shen und Qin Meng. „Preparation of Amino-Functional UiO-66/PIMs Mixed Matrix Membranes with [bmim][Tf2N] as Regulator for Enhanced Gas Separation“. Membranes 11, Nr. 1 (04.01.2021): 35. http://dx.doi.org/10.3390/membranes11010035.

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Development of mixed matrix membranes (MMMs) with excellent permeance and selectivity applied for gas separation has been the focus of world attention. However, preparation of high-quality MMMs still remains a big challenge due to the lack of enough interfacial interaction. Herein, ionic liquid (IL)-modified UiO-66-NH2 filler was first incorporated into microporous organic polymer material (PIM-1) to prepare dense and defect-free mixed matrix membranes via a coating modification and priming technique. IL [bmim][Tf2N] not only improves the hydrophobicity of UiO-66-NH2 and facilitates better dispersion of UiO-66-NH2 nanoparticles into PIM-1 matrix, but also promotes the affinity between MOFs and polymer, sharply reducing interface non-selective defects of MMMs. By using this strategy, we can not only facilely synthesize high-quality MMMs ignoring non-selective interfacial voids, but also structurally regulate MOF nanoparticles in the polymer substrate and greatly improve interface compatibility and stability of MMMs. The method also gives suitable level of generality for fabrication of versatile defect-free MMMs based on different combination of MOFs and PIMs. The prepared UiO-66-NH2@IL/PIM-1 membrane exhibited outstanding gas separation behavior with large CO2 permeation of 8283.4 Barrer and high CO2/N2 selectivity of 22.5.

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Chen, Hongbing, Bin Xu, Jiang Wang, Lele Luan, Tianmin Zhou, Xin Nie und Yi-Lung Mo. „Interfacial Debonding Detection for Rectangular CFST Using the MASW Method and Its Physical Mechanism Analysis at the Meso-Level“. Sensors 19, Nr. 12 (20.06.2019): 2778. http://dx.doi.org/10.3390/s19122778.

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In this study, the transient multichannel analysis of surface waves (MASW) is proposed to detect the existence, the location and the length of interface debonding defects in rectangular concrete-filled steel tubes (CFST). Mesoscale numerical analysis is performed to validate the feasibility of MASW-based interfacial debonding detection. Research findings indicate that the coaxial characteristics in the Rayleigh wave disperse at the starting point of the debonding area and gradually restores at the end of the defect. For healthy specimens, the surface wave mode in CFST is closer to the Rayleigh wave. However, it can be treated as a Lamb wave since the steel plate is boundary-free on both sides in the debonding area. The displacement curves are further investigated with forward analysis to obtain the dispersion curves. The mesoscale numerical simulation results indicate that the propagation characteristic of the surface wave is dominated by the debonding defect. The detectability of interfacial debonding detection for rectangular CFST using the MASW approach is numerically verified in this study. The proposed MASW-based nondestructive testing technique can achieve bond-slip detection by comparing the variation trend of the coaxial characteristics in the time-history output signals and the dispersion curves obtained from the forward analysis, for avoiding misjudgment of the experimental observations.

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Chen, Gaoqiang, Huijie Liu und Qingyu Shi. „Development of Computational Approach for Analyzing In-Process Thermal-Mechanical Condition during Friction Stir Welding for Prediction of Material Bonding Defect“. Materials 16, Nr. 23 (01.12.2023): 7473. http://dx.doi.org/10.3390/ma16237473.

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Unlike the conventional fusion welding process, friction stir welding (FSW) relies on solid-state bonding (SSB) to join metal surfaces. In this study, a straightforward computational methodology is proposed for predicting the material bonding defects during FSW using quantitative evaluation of the in-process thermal-mechanical condition. Several key modeling methods are integrated for predicting the material bonding defects. FSW of AA2024 is taken as an example to demonstrate the performance of the computational analysis. The dynamic sticking (DS) model is shown to be able to predict the geometry of the rotating flow zone near the welding tool. Butting interface tracking (BIT) analysis shows a significant orientation change occurring to the original butting interface, owing to the material flow in FSW, which has a major impact on the bonding pressure at the butting interface. The evolution of the interfacial temperature and the interfacial pressure at the butting interface was obtained to analyze their roles in the formation of material bonding. Four bonding-quality indexes for quantifying the thermal-mechanical condition are tested to show their performance in characterizing the bonding quality during FSW. When the BQI is below a critical value, a bonding defect will be generated. The paper indicates that the simulation-based prediction of a material bonding defect is highly feasible if the developed methodology is extended to quantitatively determine the critical value of the bonding quality index for successful SSB for various alloys.

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Serizawa, Yurika, Tomoe Yayama und Fumiko Akagi. „Theoretical study of the interfacial properties of carbon nanotube/epoxy resin nanocomposites“. Japanese Journal of Applied Physics, 11.03.2022. http://dx.doi.org/10.35848/1347-4065/ac5d24.

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Abstract We demonstrate the effect of defects in carbon nanotubes (CNTs) on the interfacial interaction of CNT/epoxy nanocomposites by first-principles calculation. Atomistic interface models consisting of single-walled CNT and epoxy (diglycidyl ether of bisphenol A; DGEBA) were used. Total energy, the partial density of states, and electronic charge distributions were investigated. The results indicated a weak interaction between the defect-free CNT and the epoxy. When the DGEBA was placed over the site nearest to the defect on a CNT, it was found to be energetically stable. Moreover, shared charge density, which may result in a stronger interfacial interaction, was observed between the CNT and DGEBA. The presence of the defects is responsible for providing the valence electrons that do not participate in the carbon-carbon bond in the CNTs. Consequently, we conclude that the defects in the CNT are sometimes useful and may enhance interfacial adhesion at the interface of nanocomposites.

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Dudley, M., G. D. Yao, J. Wu, H. Y. Liu und Y. C. Kao. „Determination of 3-Dimensional Defect Structures in Gallium Arsenide Epilayers on Silicon Using White Beam Synchrotron Radiation Topography in both Transmission and Grazing Bragg-Laue Geometry.“ MRS Proceedings 160 (1989). http://dx.doi.org/10.1557/proc-160-469.

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AbstractWhite beam synchrotron topography in both transmission and grazing Bragg-Laue geometries has been used to reveal the 3-dimensional defect structure in MBE grown GaAs epilayers on Si. Defects observed and characterized include substrate threading dislocations and interfacial dislocations. Dislocation line direction and Burgers vector analysis was performed on transmission topographs. The relationship between substrate threading dislocations and interfacial dislocations was established. In the grazing Bragg-Laue case, manipulation of geometry enabled depth profiling of defect structures in the epilayer. The position of the interfacial dislocations was verified by correlating penetration depth analysis with the visibility of the dislocations under different diffraction conditions.This technique affords a rapid and non-destructive way of quantitatively characterizing processing induced damage in such systems.

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