Journal articles: 'Defect properties'

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Liang, Yingjing, Hongfa Qin, Jianzhang Huang, Sha Huan, and David Hui. "Mechanical properties of boron nitride sheet with randomly distributed vacancy defects." Nanotechnology Reviews 8, no. 1 (November 12, 2019): 210–17. http://dx.doi.org/10.1515/ntrev-2019-0019.

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Abstract Defects and temperature effects on the mechanical properties of hexagonal boron nitride sheet (h-BN) containing randomly distributed defects are investigated by molecular dynamics simulations and the reasons of the results are discussed. Results show that defect deteriorate the mechanical performance of BNNS. The mechanical properties are reduced by increasing percentage of vacancy defects including fracture strength, fracture strain and Young’s modulus. Simulations also indicate that the mechanical properties decrease with the temperature increasing. Moreover, defects affect the stable configuration at high temperature. With the percentage of defect increases the nanostructures become more and more unstable. Positions of the defect influent the mechanical properties. The higher the temperature and the percentage of defect are, the stronger the position of the randomly distributed defect affects the mechanical properties. The study provides a theoretical basis for the preparation and performance optimization of BNNSs.

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JIANG, B., J. L. PENG, L. A. BURSILL, and H. WANG. "MICROSTRUCTURE AND PROPERTIES OF FERROELECTRIC Bi4Ti3O12 THIN FILMS." Modern Physics Letters B 13, no. 26 (November 10, 1999): 933–45. http://dx.doi.org/10.1142/s0217984999001147.

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The film morphology and defect structure of ferroelectric bismuth titanate thin films are studied by high resolution transmission electron microscopy. As-grown and RTA-processed thin films have similar defect structures, consisting of stacking faults and complex intergrowth defect structures. The as-grown specimens prepared at low temperature had smaller particle size with higher density of these defects compared to RTA-processed samples. Detailed atomic structure models for the stacking faults and intergrowth defect structures are proposed and the computer-simulated images are compared with experiment.

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Sozykin, Sergey Anatolevich, Valeriy Petrovich Beskachko, and G. P. Vyatkin. "Atomic Structure and Mechanical Properties of Defective Carbon Nanotube (7,7)." Materials Science Forum 843 (February 2016): 78–84. http://dx.doi.org/10.4028/www.scientific.net/msf.843.78.

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The article presents the results of first-principle modeling of a defectless (7,7) carbon nanotube and (7,7) nanotubes containing single and double vacancy defects, as well as Stone–Wales defects. These types of defects are often found in real nanotubes and affect their properties. We have established that reliable results can be obtained by using models of more than 1.5 nm in length. It turned out that a single vacancy defect has the least influence on Young modulus, and double n type vacancy defect in the most influential. The elongation at break also depends on the defect type and is 30-60% less than for perfect tubes.

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Sun, S. P., Y. F. Hu, X. P. Li, Y. Chen, H. J. Wang, Y. Yu, Y. Jiang, and D. Q. Yi. "The effect of point defect on mechanical properties of MoSi2." International Journal of Modern Physics B 31, no. 16-19 (July 26, 2017): 1744081. http://dx.doi.org/10.1142/s0217979217440817.

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The effect of point defect on mechanical properties of MoSi2 has been investigated by the first-principles. The elastic constants, mechanical modulus, hardness and thermodynamic properties of MoSi2 with four different single point defects have been calculated. By comparing with the defect-free MoSi2, it is found that the bulk modulus/shear modulus ratio (B/G) of MoSi2 with a single point defect increases slightly while the Debye temperature decreases drastically, which indicates that MoSi2 with some point defects have relatively good ductility. The calculated three-dimensional (3D) contours of elastic modulus and these projections on the (001) and (010) planes show that the directionality of Young’s modulus and shear modulus is unapparent for MoSi2 with a point defect (V[Formula: see text] and Mo[Formula: see text]) but it is relatively obvious for MoSi2 with V[Formula: see text] and Si[Formula: see text]. It suggests that V[Formula: see text] and Si[Formula: see text] can strengthen the anisotropy in elasticity. The electronic properties of C11[Formula: see text] MoSi2 with different single point defects have been studied to reveal further the influencing mechanism of point defect on mechanical properties. This work should help reveal the interrelation between intrinsic defects and service performance of MoSi2.

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Zhao, Peng Cheng, Yu Bao Niu, Shuo Qin, and Yang Tao Yu. "Effect of Bucking on the Mechanical Properties of Honeycomb Sandwich Structure." Applied Mechanics and Materials 484-485 (January 2014): 705–7. http://dx.doi.org/10.4028/www.scientific.net/amm.484-485.705.

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Static compression test on the Honeycomb sandwich structure with surface core defect carry out in this paper. The specimen divided into four groups, one had no defect, one had circle defect, the other two groups had rectangular defect in different direction. In the process of loading the strain gauge which located on the specimen surface in each group record the strain transformation of the specimen surface. Through the Static load test on the fatigue testing machine, fracture load of each specimen was record. According to the data, how the size and shape of the defect influence the compression static strength of Honeycomb sandwich was discussed, and inspecting defects direction how to affect the structural static strength by means of theoretical analysis and data fitting, meanwhile the shape of the defects in structure how to effect buckling was discussed too.

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Jadi, Supri, and A. Setiadi. "Structural Shifting and Electronic Properties of Stone-Wales Defect in Armchair Edge (5,5) Carbon Nanotube." Advanced Materials Research 772 (September 2013): 380–85. http://dx.doi.org/10.4028/www.scientific.net/amr.772.380.

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Stone Wales (SW) defect is one type of topological defect on the CNT, in this study we performed first principles calculations of SW defects in armchair edge (5,5) carbon nanotube (CNT) by the density functional theory (DFT). Two different defects were studied such as longitudinal and circumference types. Our calculation results show that a longitudinal SW defect is more stable than circumference SW defect. However barrier energy as parameter to control the SW defect in CNT was studied, in calculation we applied Nudge Elastic Band (NEB) method to find minimum energy path (MEP) and barrier energy for SW defect transitions. The result shows that barrier energy of circumference SW defect is lower than another one. We also found that in the case of circumference SW defect, armchair edge (5,5) CNT become semiconductor with the band gap of 0.0544 eV.

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Wolff, J., M. Franz, A. Broska, B. Köhler, and Th Hehenkamp. "Defect types and defect properties in FeAl alloys." Materials Science and Engineering: A 239-240 (December 1997): 213–19. http://dx.doi.org/10.1016/s0921-5093(97)00584-4.

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Lowitzer, Stephan, Dan J. Wilson, Björn Winkler, Victor Milman, and Julian D. Gale. "Defect properties of albite." Physics and Chemistry of Minerals 35, no. 3 (December 5, 2007): 129–35. http://dx.doi.org/10.1007/s00269-007-0204-4.

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Kamei, Koji, Ling Guo, Kenji Momose, and Hitoshi Osawa. "Structure of Straight-Line Defect and its Effect on the Electrical Properties of Schottky Barrier Diodes." Materials Science Forum 858 (May 2016): 213–16. http://dx.doi.org/10.4028/www.scientific.net/msf.858.213.

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We have investigated the “straight-line defect,” which has not been classified separately and is quite similar to the carrot defect. We found that the straight-line defect differed structurally from the carrot defect. The presence of a particle on the substrate-epi layer interface seemed to be the cause of the defect; a layer of poly-type (3C-SiC) extended from the particle to the epi-layer surface. The straight-line defect likely resulted from shape change from the 3C-SiC triangular defect. This change in shape from triangular to straight-line defects depended on the C/Si ratio. To investigate the electrical characteristics, we fabricated a Schottky barrier diode (SBD) structure on a silicon carbide (SiC) epi wafer. With application of a high voltage, destruction occurred on both the upstream and the downstream side of the step flow of straight-line defects in the reverse voltage test. This reverse direction characteristic differed from that observed with triangular defects.

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Li, Bao Long, Li Jun Zhou, and Jian Gao Guo. "Influence of Defects on Elastic Buckling Properties of Single-Layered Graphene Sheets." Key Engineering Materials 636 (December 2014): 11–14. http://dx.doi.org/10.4028/www.scientific.net/kem.636.11.

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Molecular structural mechanics based finite element method has been applied to study the effects of two types of Stone-Wales (SW) defects and vacancy defect on elastic buckling properties of single-layered graphene sheets (SLGSs). The defect effect factors of critical buckling stresses are calculated for the defective SLGSs with different chirality and geometrical dimensions. It is proved that defect effect factors are size-dependent and chirality-dependent. The results show that the vacancy defects will always weaken the SLGSs’ stability, and two types of SW defects have different effects on zigzag and armchair SLGSs. What’s more, the positions of defects also have remarkable influence on the critical buckling stress of SLGSs.

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Li, Ying, Han Bi, Yong Du, and Renchao Che. "Synthesis and thermoelectric properties of defect-containing PbSe–PbTe heterojunction nanostructures." RSC Advances 7, no. 85 (2017): 53855–60. http://dx.doi.org/10.1039/c7ra09282b.

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Defect-containing and defect-free PbSe–PbTe heterogeneous (HNSs) nanostructures are synthesized. The strain distribution and defects in the interface of PbSe–PbTe HNSs affect the thermoelectric parameters of PbSe–PbTe HNSs.

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12

PENG, QING, JARED CREAN, ALBERT K. DEARDEN, CHEN HUANG, XIAODONG WEN, STÉPHANE P. A. BORDAS, and SUVRANU DE. "DEFECT ENGINEERING OF 2D MONATOMIC-LAYER MATERIALS." Modern Physics Letters B 27, no. 23 (September 9, 2013): 1330017. http://dx.doi.org/10.1142/s0217984913300172.

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Atomic-thick monolayer two-dimensional materials present advantageous properties compared to their bulk counterparts. The properties and behavior of these monolayers can be modified by introducing defects, namely defect engineering. In this paper, we review a group of common two-dimensional crystals, including graphene, graphyne, graphdiyne, graphn-yne, silicene, germanene, hexagonal boron nitride monolayers and MoS2monolayers, focusing on the effect of the defect engineering on these two-dimensional monolayer materials. Defect engineering leads to the discovery of potentially exotic properties that make the field of two-dimensional crystals fertile for future investigations and emerging technological applications with precisely tailored properties.

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13

KIM, JONG-YUP, JOON-HYUN LEE, and SEUNG-HOON NAHM. "EFFECT OF CASTING DEFECT ON MECHANICAL PROPERTIES OF 17-4PH STAINLESS STEEL." International Journal of Modern Physics B 20, no. 25n27 (October 30, 2006): 4463–68. http://dx.doi.org/10.1142/s0217979206041525.

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Damage and integrity evaluation techniques should be developed steadily in order to ensure the reliability and the economic efficiency of gas turbine engines. Casting defects may exist in most casting components of gas turbine engines, and the defects could give serious effect on mechanical properties and fracture toughness. Therefore, it is very important to understand the effect of casting defects on the above properties in order to predict the safety and life of components. In this study, specimens with internal casting defects, made from 17-4PH stainless steel, were prepared and evaluated and characterized based on the volume fraction of defects. The relation between mechanical properties such as tensile, low cycle fatigue and fracture toughness and volume fraction of defect has been investigated. As a result of the analysis, the mechanical properties of 17-4PH decreased as the defect volume fraction increased with very good linearity. The mechanical properties also showed an inversely proportional relationship to electrical resistivity.

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14

Gali, Adam. "Excitation Properties of Silicon Vacancy in Silicon Carbide." Materials Science Forum 717-720 (May 2012): 255–58. http://dx.doi.org/10.4028/www.scientific.net/msf.717-720.255.

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Isolated point defects possessing high spin ground state and below-band-gap excitation may play a key role in realizing solid state quantum bits in semiconductors which are the basic building blocks of quantum computers. Silicon vacancy in silicon carbide provides these features making it a feasible candidate in this special and emerging field of science. However, it has been not clarified what is the exact nature of the luminescence of silicon vacancy detected in hexagonal polytypes. This is the first crucial step needed to understand this basic defect in silicon carbide. We report density functional theory based calculations on silicon vacancy defect. Based on the obtained results we identify the silicon vacancy related photoluminescence signals with the negatively charged defect.

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15

Klinkhamer, F. R., and Z. L. Wang. "Lensing and imaging by a stealth defect of spacetime." Modern Physics Letters A 34, no. 03 (January 30, 2019): 1950026. http://dx.doi.org/10.1142/s0217732319500263.

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We obtain the geodesics for the simplest possible stealth defect which has a flat spacetime. We, then, discuss the lensing properties of such a defect, and the corresponding image formation. Similar lensing properties can be expected to hold for curved-spacetime stealth defects.

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16

Hsu, Julia W. P. "Semiconductor Defect Studies Using Scanning Probes." Microscopy and Microanalysis 6, S2 (August 2000): 704–5. http://dx.doi.org/10.1017/s1431927600036011.

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Understanding how defects alter physical properties of materials has lead to improvements in materials growth as well as device performance. Transmission electron microscopy (TEM) provides an invaluable tool for structural characterization of defects. Our current knowledge of crystallographic defects, such as dislocations, would not have been possible without TEM. Recently, scanning tunneling microscopy and scanning force microscopy (SFM) have shown the capability of imaging surface defects with atomic or near-atomic resolution in topographic images. What is more important is to gain knowledge on how the presence of a certain type of defects changes the physical properties of materials. For example, how is the carrier lifetime altered near electrically active defects? How does photoresponse vary near grain boundaries? Where are defect levels in the forbidden bandgap? This talk will discuss several examples of how scanning probe microscopies (SPMs) can contribute to this aspect of defect studies in semiconductors.

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17

Seeger, Alfred. "Diffusion and Point-Defect Properties." Defect and Diffusion Forum 95-98 (January 1993): 147–70. http://dx.doi.org/10.4028/www.scientific.net/ddf.95-98.147.

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18

LUBOMIRSKY, I. "Mechanical properties and defect chemistry." Solid State Ionics 177, no. 19-25 (October 15, 2006): 1639–42. http://dx.doi.org/10.1016/j.ssi.2006.01.020.

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Yauri, J. M., and S. Watanabe. "Defect dependent properties in grossularite." physica status solidi (c) 2, no. 1 (January 2005): 555–59. http://dx.doi.org/10.1002/pssc.200460232.

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Ogorodnikov, I. N., and A. V. Kruzhalov. "Defect Properties of Beryllium Oxide." Materials Science Forum 239-241 (January 1997): 51–56. http://dx.doi.org/10.4028/www.scientific.net/msf.239-241.51.

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Elliott, James. "Enamel Properties and Defect Characterization." European Journal of Oral Sciences 114, s1 (May 2006): 375–76. http://dx.doi.org/10.1111/j.1600-0722.2006.00375.x.

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22

Zhang, Sen, Zhihua Ren, Zude Ding, Jincheng Wen, and Zhixin Yan. "Influence of Existing Defects on Mechanical Properties of NC Lining." Advances in Materials Science and Engineering 2019 (December 19, 2019): 1–15. http://dx.doi.org/10.1155/2019/8571297.

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The mechanical properties of the lining are directly affected by defects such as voids behind the lining and insufficient thickness of the lining. In order to quantitatively evaluate this effect, the mechanical behavior of the lining under the influence of the void behind the lining, the insufficient thickness of the lining, and the combination of the two kinds of defects are adopted by the 1/5 scale model test. Based on the experimental research, numerical calculation models based on the CDP model for defect lining are established, with the effects of load direction, stratum stiffness, defect location, defect type, and degree on the mechanical behavior of the lining analyzed by the numerical simulation. The experimental and numerical results show that the void weakens the stiffness of the lining. As the void range increases, the lining becomes more deformable and its bearing capacity decreases with the “S” curve. Thinning significantly reduces the deformation properties of the lining and the bearing capacity and stiffness of the thinned section. The lining bearing capacity decreases linearly with the increase of the thinning ratio, when the load is applied at the thinning. With the influence of combined defects on the load-displacement curve of the lining fluctuating drastically, the mechanical properties of the lining are significantly reduced. The bearing capacity of lining decreases with the increase of composite defects in a “S” shape. The effect of void and lining thinning on the lining bearing capacity increases with the increase of the stiffness of the formation. The loss rate equation of the concrete lining bearing capacity under the influence of existing defects is established by using the L-M nonlinear regression analysis, a provision of scientific guidance for the safety evaluation of the defect lining.

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Wang, Zongguo, Shaojing Qin, and Chuilin Wang. "Properties of single-layer graphene with supercell doped by one defect only." International Journal of Modern Physics B 31, no. 27 (October 24, 2017): 1750196. http://dx.doi.org/10.1142/s021797921750196x.

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Graphene has vast promising applications in nanoelectronics and spintronics because of its unique magnetic and electronic properties. Making use of an ab initio spin-polarized density functional theory, implemented by the method of the Heyd–Scuseria–Ernzerhof 06 (HSE06) hybrid functional, the properties of various defect dopants in a supercell of a semi-metal monolayer graphene were investigated. We found from our calculation that introducing one defect dopant in a supercell would break the spin sublattice symmetry, and will induce a magnetic state at some appropriate doping concentrations. This paper systematically analyzes the magnetic effects of three types of defects on graphene, that is, vacancy, substitutional dopant and adatoms. Different types of defects will induce various new properties in graphene. The energies and electronic properties of these three types of defects were also calculated.

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Danielski, M. "Defect distributions and transport properties in high defect, multilayer scales." Solid State Ionics 26, no. 2 (March 1988): 152. http://dx.doi.org/10.1016/0167-2738(88)90070-7.

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Li, Maoyuan, Peng Chen, Bing Zheng, Tianzhengxiong Deng, Yun Zhang, Yonggui Liao, and Huamin Zhou. "Effect of Stone-Wales Defect on Mechanical Properties of Gr/epoxy Nanocomposites." Polymers 11, no. 7 (July 1, 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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Wang, Sanjun, Xueqing Wang, Jinming Li, Yu Jia, and Fei Wang. "Electronic and optical properties of Er doped in AlN." Modern Physics Letters B 29, no. 21 (August 10, 2015): 1550114. http://dx.doi.org/10.1142/s0217984915501146.

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Using density functional theory combined [Formula: see text] method, the structural, electronic and optical properties of rare earth Er substituted Al atom [Formula: see text] and its complex with neighboring N vacancy [Formula: see text]-[Formula: see text] in wurtzite AlN were investigated, respectively. Calculated results show that both defects induced quite localized [Formula: see text]-[Formula: see text] related defect donor levels in the band gap but had few effects on host electronic structures. Moreover, the calculated complex dielectric functions and other optical constants show that these two defects show clear bulk optical properties, only a small peak near the redshift edge appears for the complex defect. These results show that Er dopant AlN should be a good optical material candidate for optoelectronics application.

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Borovina Josko, João Marcelo, and João Eduardo Ferreira. "Visualization properties for data quality visual assessment: An exploratory case study." Information Visualization 16, no. 2 (July 25, 2016): 93–112. http://dx.doi.org/10.1177/1473871616629516.

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Data quality assessment outcomes are essential to ensure useful analytical processes results. Relevant computational approaches provide assessment support, especially to data defects that present more precise rules. However, data defects that are more dependent of data context knowledge challenge the data quality assessment since the process involves human supervision. Visualization systems belong to a class of supervised tools that can make visible data defect structures. Despite their considerable design knowledge encodings, there is little support design to visual quality assessment of data defects. Therefore, this work reports a case study that has explored which and how visualization properties facilitate visual detection of data defect. Its outcomes offer a first set of implications to design visualization system to permit data quality visual assessment.

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Chiodelli, G., U. Anselmi-Tamburini, M. Arimondi, G. Spinolo, and G. Flor. "Defect Chemistry of “BaCuO2” II. Transport Properties and Nature of Defects." Zeitschrift für Naturforschung A 50, no. 11 (November 1, 1995): 1059–66. http://dx.doi.org/10.1515/zna-1995-1113.

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Abstract The charge transport properties of "BaCuO2" with 88:90 (Ba :Cu) cation ratio were characterized by thermopower, electrical conductivity and ionic transport number measurements in a wide range of temperature and oxygen partial pressure conditions. The nature of carriers is always represented by small polarons due to self-trapping of the electronic holes generated by the oxygen non-stoichiometry equilibrium. Some anomalies in carrier mobility as a function of temperature are shown not to be related to incomplete ionization of oxygen atoms on interstitial sites

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Zhou, Gang, Ye Tian, Shuai Xue, Guangqi Zhou, Ci Song, Lin Zhou, Guipeng Tie, Feng Shi, Yongxiang Shen, and Zhe Zhu. "Enhancement of the Load Capacity of High-Energy Laser Monocrystalline Silicon Reflector Based on the Selection of Surface Lattice Defects." Materials 13, no. 18 (September 19, 2020): 4172. http://dx.doi.org/10.3390/ma13184172.

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Various defects during the manufacture of a high-energy laser monocrystalline silicon reflector will increase the energy absorption rate of the substrate and worsen the optical properties. Micron-scale or larger manufacturing defects have been inhibited by mechanism study and improvement in technology, but the substrate performance still fails to satisfy the application demand. We focus on the changes in the optical properties affected by nanoscale and Angstrom lattice defects on the surface of monocrystalline silicon and acquire the expected high reflectivity and low absorptivity through deterministic control of its defect state. Based on the first principles, the band structures and optical properties of two typical defect models of monocrystalline silicon—namely, atomic vacancy and lattice dislocation—were analyzed by molecular dynamics simulations. The results showed that the reflectivity of the vacancy defect was higher than that of the dislocation defect, and elevating the proportion of the vacancy defect could improve the performance of the monocrystalline silicon in infrared (IR) band. To verify the results of simulations, the combined Ion Beam Figuring (IBF) and Chemical Mechanical Polishing (CMP) technologies were applied to introduce the vacancy defect and reduce the thickness of defect layer. After the process, the reflectivity of the monocrystalline silicon element increased by 5% in the visible light band and by 12% in the IR band. Finally, in the photothermal absorption test at 1064 nm, the photothermal absorption of the element was reduced by 80.5%. Intense laser usability on the monocrystalline silicon surface was achieved, and the effectiveness and feasibility of deterministic regulation of optical properties were verified. This concept will be widely applied in future high-energy laser system and X-ray reflectors.

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Wimmer, Yannick, Al-Moatasem El-Sayed, Wolfgang Gös, Tibor Grasser, and Alexander L. Shluger. "Role of hydrogen in volatile behaviour of defects in SiO 2 -based electronic devices." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 472, no. 2190 (June 2016): 20160009. http://dx.doi.org/10.1098/rspa.2016.0009.

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Charge capture and emission by point defects in gate oxides of metal–oxide–semiconductor field-effect transistors (MOSFETs) strongly affect reliability and performance of electronic devices. Recent advances in experimental techniques used for probing defect properties have led to new insights into their characteristics. In particular, these experimental data show a repeated dis- and reappearance (the so-called volatility ) of the defect-related signals. We use multiscale modelling to explain the charge capture and emission as well as defect volatility in amorphous SiO 2 gate dielectrics. We first briefly discuss the recent experimental results and use a multiphonon charge capture model to describe the charge-trapping behaviour of defects in silicon-based MOSFETs. We then link this model to ab initio calculations that investigate the three most promising defect candidates. Statistical distributions of defect characteristics obtained from ab initio calculations in amorphous SiO 2 are compared with the experimentally measured statistical properties of charge traps. This allows us to suggest an atomistic mechanism to explain the experimentally observed volatile behaviour of defects. We conclude that the hydroxyl-E′ centre is a promising candidate to explain all the observed features, including defect volatility.

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Xiao, Zhong Run, Jun Hui Nie, and Jian Zhong Fan. "Effect of SiC Defects on Performance of Particle Reinforced Aluminum Matrix Composites." Materials Science Forum 993 (May 2020): 730–38. http://dx.doi.org/10.4028/www.scientific.net/msf.993.730.

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The effect of segregation defect of SiC particles on the properties of materials was studied. 15% SiCp/2009Al composites were prepared by powder metallurgy (PM). Special SiC/Al samples were added to 15% SiCp/2009Al composites. These SiC/Al samples with different sizes and volume fractions were 25%, 35%, 45% and 60%, respectively, which resulted in SiC particulates segregation defect. The 15% SiCp/2009Al composites with defects were tested by ultrasonic testing. Tensile samples were obtained at the locations, where defects might be detected and the mechanical properties were tested. The results showed that all defective samples were cracked at the defective location. The difference in tensile strength between the samples of defect and the samples without defect was large. The toughness of the sample containing the defect reduced and the brittleness increased. The dimples on the matrix indicate that ductile fracture occurred during the fracture process. The cleavage fracture or cracking of the SiC particulates indicated that the stress can be effectively transferred from the matrix to the particles, and the particulates strengthen the matrix well. However, the sample with defect led to brittle fracture in the defect, and a crack source produced at the interface, resulting in a significant decrease in the mechanical properties of the material. If the inhomogeneous distribution of particulate containing a large area was found in the ultrasonic testing of the aluminum matrix composites, the tensile properties of the products generally cannot meet the requirement for application.

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Sun, Shouzheng, Zhenyu Han, Hongya Fu, Hongyu Jin, Jaspreet Singh Dhupia, and Yang Wang. "Defect Characteristics and Online Detection Techniques During Manufacturing of FRPs Using Automated Fiber Placement: A Review." Polymers 12, no. 6 (June 12, 2020): 1337. http://dx.doi.org/10.3390/polym12061337.

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Automated fiber placement (AFP) is an advanced manufacturing method for composites, which is especially suitable for large-scale composite components. However, some manufacturing defects inevitably appear in the AFP process, which can affect the mechanical properties of composites. This work aims to investigate the recent works on manufacturing defects and their online detection techniques during the AFP process. The main content focuses on the position defect in conventional and variable stiffness laminates, the relationship between the defects and the mechanical properties, defect control methods, the modeling method for a void defect, and online detection techniques. Following that, the contributions and limitations of the current studies are discussed. Finally, the prospects of future research concerning theoretical and practical engineering applications are pointed out.

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Ge, Xiang-Hong, Xing-Xing Ding, Bao-He Yuan, Xian-Sheng Liu, Yong-Guang Cheng, and Er-Jun Liang. "AC Impedence Properties of Multifunction Ceramics ZrScMo2VO12." Science of Advanced Materials 13, no. 4 (April 1, 2021): 615–19. http://dx.doi.org/10.1166/sam.2021.3966.

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Alternating current (AC) impedance properties of negative expansion material ZrScMo2VO12 are studied with electrochemical impedance spectroscopy. The conductivity is measured as 2.49×10-4 Ohm-1cm-1K at 673 K and 4.15×10-4 Ohm-1cm-1K at 773 K. We have also elucidated that the conduction of ZrScMo2VO12 come from defects and the co-doping of N and P type in semiconductors. The Schottky defect and Frenkel defect in the material lead to O2- ion conduction, and co-doping leads to electron conduction. And the grain boundary barrier could limit the conduction of electron and hole. This work may be useful for the application exploration of ZrScMo2VO12 in fuel cell and corresponding energy conversion fields.

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Wu, Zhangting, and Zhenhua Ni. "Spectroscopic investigation of defects in two-dimensional materials." Nanophotonics 6, no. 6 (March 11, 2017): 1219–37. http://dx.doi.org/10.1515/nanoph-2016-0151.

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AbstractTwo-dimensional (2D) materials have been extensively studied in recent years due to their unique properties and great potential for applications. Different types of structural defects could present in 2D materials and have strong influence on their properties. Optical spectroscopic techniques, e.g. Raman and photoluminescence (PL) spectroscopy, have been widely used for defect characterization in 2D materials. In this review, we briefly introduce different types of defects and discuss their effects on the mechanical, electrical, optical, thermal, and magnetic properties of 2D materials. Then, we review the recent progress on Raman and PL spectroscopic investigation of defects in 2D materials, i.e. identifying of the nature of defects and also quantifying the numbers of defects. Finally, we highlight perspectives on defect characterization and engineering in 2D materials.

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Patel, Ajay M., Nipun Gosai, and Anand Y. Joshi. "A Review on Defects in Carbon Nanotubes." Applied Mechanics and Materials 813-814 (November 2015): 145–50. http://dx.doi.org/10.4028/www.scientific.net/amm.813-814.145.

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Various defects on the CNT wall have been reported, which are formed during the synthesizing process. CNTs have superior properties compared to the traditional engineering materials. However, these properties hold only for the ideal case of carbon nanotubes, where these are made of perfect hexagonal graphite honeycomb lattice of mono-atomic layer thickness. The advantages or disadvantages of the presence of defects in carbon nanotubes depend on their applications. Structural defects may increase the adhesion of other atoms and molecules to carbon nanotubes. It has also been found that the defects in CNT do cause a change in its resonant frequency as compared to that of a non-defective CNT. The defects that have been considered for the purpose of analysis in this research includes defects in the carbon nanotubes likewise Waviness, Vacancy Defect, Pinhole Defect, Fracture and Stone Wales Defect. It has been observed that with the increase in the number of defects in CNT, a reduction in the fundamental frequency is observed.

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Lee, Wonk Yun, Shinya Suzuki, and Masaru Miyayama. "Electrode Properties of Defect-Introduced Graphenes for Lithium-Ion Batteries." Key Engineering Materials 582 (September 2013): 103–6. http://dx.doi.org/10.4028/www.scientific.net/kem.582.103.

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Electrochemical properties of defect-introduces graphenes for lithium ion batteries were investigated. Graphene sheets (GSs) were prepared from graphite through treating with oxidizing agent followed by rapid thermal exfoliation. Defect concentration was controlled by selecting the number of times of oxidation of graphite. GSs electrodes derived from 1, 2 and 3 times-oxidized graphite oxides exhibited a high charge capacity of 1250, 1790 and 2310 mAh g1, respectively, at the 20th cycle at a current density of 100 mA g1. The enhanced capacity is assumed to be due to additional lithium storage sites such as defects and edges.

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Guerra, Fabrizio, Marta Mazur, Denise Corridore, Debora Pasqualotto, Gianna Maria Nardi, and Livia Ottolenghi. "Evaluation of the Esthetic Properties of Developmental Defects of Enamel: A Spectrophotometric Clinical Study." Scientific World Journal 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/878235.

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Objectives. Detailed clinical quantification of optical properties of developmental defect of enamel is possible with spectrophotometric evaluation. Developmental defects of enamel (DDE) are daily encountered in clinical practice. DDE are an alteration in quality and quantity of the enamel, caused by disruption and/or damage to the enamel organ during amelogenesis.Methods. Several clinical indices have been developed to categorize enamel defects based on their nature, appearance, microscopic features, or cause. A sample of 39 permanent teeth presenting DDE on labial surface was examined using the DDE Modified Index and SpectroShade evaluation. The spectrophotometric approach quantifiesL*(luminosity),a*(quantity of green-red), andb*(quantity of blue-yellow) of different DDE.Conclusions. SpectroShade evaluation of the optical properties of the enamel defect enhances clinical understanding of severity and extent of the defect and characterizes the enamel alteration in terms of color discrepancy and surface characterization.

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Veblen, David R. "Fine structure and properties of defects in naturally occurring silicates and oxides." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 460–61. http://dx.doi.org/10.1017/s0424820100175430.

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Extended defects and interfaces control many processes in rock-forming minerals, from chemical reactions to rock deformation. In many cases, it is not the average structure of a defect or interface that is most important, but rather the structure of defect terminations or offsets in an interface. One of the major thrusts of high-resolution electron microscopy in the earth sciences has been to identify the role of defect fine structures in reactions and to determine the structures of such features. This paper will review studies using HREM and image simulations to determine the structures of defects in silicate and oxide minerals and present several examples of the role of defects in mineral chemical reactions. In some cases, the geological occurrence can be used to constrain the diffusional properties of defects.The simplest reactions in minerals involve exsolution (precipitation) of one mineral from another with a similar crystal structure, and pyroxenes (single-chain silicates) provide a good example. Although conventional TEM studies have led to a basic understanding of this sort of phase separation in pyroxenes via spinodal decomposition or nucleation and growth, HREM has provided a much more detailed appreciation of the processes involved.

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Kimerling, Lionel C. "Defect Engineering." MRS Bulletin 16, no. 12 (December 1991): 42–47. http://dx.doi.org/10.1557/s0883769400055342.

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The pervasive role of defects in determining the thermal, mechanical, electrical, optical, and magnetic properties of materials is biblical. Thermodynamic control of imperfection under equilibrium conditions dictates, for instance, the high temperatures needed to raise defect content for diffusion processes. Nonequilibrium treatments, such as work hardening, are used to control dislocation and grain boundary density and morphology to enhance mechanical properties. Both approaches represent the practice of defect engineering. Both are examples of a synergistic interaction between science and engineering in which an existing knowledge base is applied to its limits, stirring the development of new knowledge and new applications.The purpose of this article is to convey the flavor of the defect engineering culture. The invention of the transistor can be traced to a triumph of defect engineering. Original explorations of semiconductor materials had the goal of controlling surface rectification properties to devise rectifiers, oscillators, and amplifier substitutes for vacuum tube counterparts. Schottky barriers, p-n junctions and metal-oxide-semiconductor capacitors—the products of the endeavor—are now the building blocks of today's microcircuits. The commercial success of these applications has fueled a boom in materials physics research during the last two decades. The work-hardening knowledge base can be traced from the Japanese swordmaking ritual to the discovery of dislocations (in theory first, and then by direct observation). Expansion of the dislocation knowledge base was a dominating concern in materials science prior to the transistor. As shown in this article, these two disparate areas are essential components of the defect engineer's tool kit.

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Chuan, Mu Wen, Kien Liong Wong, Afiq Hamzah, Nurul Ezaila Alias, Cheng Siong Lim, and Michael Loong Peng Tan. "Electronic properties of zigzag silicene nanoribbons with single vacancy defect." Indonesian Journal of Electrical Engineering and Computer Science 19, no. 1 (July 1, 2020): 76. http://dx.doi.org/10.11591/ijeecs.v19.i1.pp76-84.

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<p>Silicene is envisaged as one of the two-dimensional (2D) materials for future nanoelectronic applications. In addition to its extraordinary electronic properties, it is predicted to be compatible with the silicon (Si) fabrication technology. By using nearest neighbour tight-binding (NNTB) approach, the electronic properties of zigzag silicene nanoribbons (ZSiNRs) with single vacancy (SV) defects are modelled and simulated. For 4-ZSiNR with L=2, the band structures and density of states (DOS) are computed based on SV incorporated ZSiNRs at varying defect locations. The results show that the SV defect will shift the band structure and increase the peak of DOS while the bandgap remain zero. This work provides a theoretical framework to understand the impact of SV defect which is an inevitable non-ideal effect during the fabrication of silicene nanoribbons (SiNRs).</p>

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Damasceno, Daniela A., R. K. N. D. Nimal Rajapakse, and Euclides Mesquita. "Atomistic Modelling of Size-Dependent Mechanical Properties and Fracture of Pristine and Defective Cove-Edged Graphene Nanoribbons." Nanomaterials 10, no. 7 (July 21, 2020): 1422. http://dx.doi.org/10.3390/nano10071422.

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Cove-edged graphene nanoribbons (CGNR) are a class of nanoribbons with asymmetric edges composed of alternating hexagons and have remarkable electronic properties. Although CGNRs have attractive size-dependent electronic properties their mechanical properties have not been well understood. In practical applications, the mechanical properties such as tensile strength, ductility and fracture toughness play an important role, especially during device fabrication and operation. This work aims to fill a gap in the understanding of the mechanical behaviour of CGNRs by studying the edge and size effects on the mechanical response by using molecular dynamic simulations. Pristine graphene structures are rarely found in applications. Therefore, this study also examines the effects of topological defects on the mechanical behaviour of CGNR. Ductility and fracture patterns of CGNR with divacancy and topological defects are studied. The results reveal that the CGNR become stronger and slightly more ductile as the width increases in contrast to normal zigzag GNR. Furthermore, the mechanical response of defective CGNRs show complex dependency on the defect configuration and distribution, while the direction of the fracture propagation has a complex dependency on the defect configuration and position. The results also confirm the possibility of topological design of graphene to tailor properties through the manipulation of defect types, orientation, and density and defect networks.

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Jiang, Jie, Tao Xu, Junpeng Lu, Litao Sun, and Zhenhua Ni. "Defect Engineering in 2D Materials: Precise Manipulation and Improved Functionalities." Research 2019 (December 2, 2019): 1–14. http://dx.doi.org/10.34133/2019/4641739.

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Two-dimensional (2D) materials have attracted increasing interests in the last decade. The ultrathin feature of 2D materials makes them promising building blocks for next-generation electronic and optoelectronic devices. With reducing dimensionality from 3D to 2D, the inevitable defects will play more important roles in determining the properties of materials. In order to maximize the functionality of 2D materials, deep understanding and precise manipulation of the defects are indispensable. In the recent years, increasing research efforts have been made on the observation, understanding, manipulation, and control of defects in 2D materials. Here, we summarize the recent research progress of defect engineering on 2D materials. The defect engineering triggered by electron beam (e-beam), plasma, chemical treatment, and so forth is comprehensively reviewed. Firstly, e-beam irradiation-induced defect evolution, structural transformation, and novel structure fabrication are introduced. With the assistance of a high-resolution electron microscope, the dynamics of defect engineering can be visualized in situ. Subsequently, defect engineering employed to improve the performance of 2D devices by means of other methods of plasma, chemical, and ozone treatments is reviewed. At last, the challenges and opportunities of defect engineering on promoting the development of 2D materials are discussed. Through this review, we aim to build a correlation between defects and properties of 2D materials to support the design and optimization of high-performance electronic and optoelectronic devices.

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Cherpakov, Alexander V., Elena A. Shlyakhova, Inna O. Egorochkina, and Yana A. Kokareva. "Identification of Concrete Properties in Beam-Type Structures with Defects Based on Dynamic Methods." Materials Science Forum 931 (September 2018): 373–78. http://dx.doi.org/10.4028/www.scientific.net/msf.931.373.

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The problem of concrete properties identification and damage location in model beam type constructions is considered on the basis of application of experimental vibration analysis. As a simple analysis model, beam structures are considered defect-free and with defects. Based on the experimental approach, the model vibrations under shock and vibration excitation are analyzed. On the basis of analytical modeling, the dynamic modulus of elasticity, the velocity of sound in the beam, and the location of the defect are calculated. A technique and an example of the location of a defect in beam type constructions are presented.

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Šicner, Jiří, Pavel Škarvada, Robert Macků, and Pavel Koktavý. "Study of the Influence of Structural Defects on Properties of Silicon Solar Cells." Key Engineering Materials 592-593 (November 2013): 449–52. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.449.

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Solar cells of common sizes contains many of these defects and it is not easy to determine the influence of particular defects on the characteristics of the whole solar cell. Therefore, in our research we use samples of size of square centimeter at which we can disentangle the influence of the defect. We localize the defect by using a CCD camera, we measure the electrical, thermal and optical properties of the sample and then study it by means an electron microscope, we find the damaged structure and put it to focused ion beam. We expect the change in electrical, thermal and optical properties of the sample.

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Bockstedte, M., A. Marini, Adam Gali, Oleg Pankratov, and A. Rubio. "Defects Identified in SiC and Their Implications." Materials Science Forum 600-603 (September 2008): 285–90. http://dx.doi.org/10.4028/www.scientific.net/msf.600-603.285.

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Defect signatures, such as deep level positions, hyperfine parameters, local vibrational modes and optical transitions characterize a defect and enable the identification of defect centers. This identification is a key to an understanding of complex phenomena like the defect kinetics. Albeit density functional theory enabled the identification of several defects and their kinetic properties, a new approach is needed to address the optical excitation of defect. Within a quasiparticle theory and taking into account excitonic effects we analyze the excited states of VC +.

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Jalili, Seifollah, Farzad Molani, and Jeremy Schofield. "First principles study on energetic, structural, and electronic properties of defective g-C3N4-zz3 nanotubes." Journal of Theoretical and Computational Chemistry 13, no. 04 (June 2014): 1450021. http://dx.doi.org/10.1142/s0219633614500217.

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The energetic, electronic and structural properties of defective g- C 3 N 4-zz3 nanotubes are considered based on spin-polarized density-functional theory calculations. Nine basic system types with vacancy defects are characterized by their stabilization energies and band gaps. It is found that the nitrogen atom denoted as N 3 is the most favorable atom for a vacancy defect. In all cases, local bond reconstruction occurs in the presence of vacancy defects. The role of C / N bond rotations on the above properties has been also investigated. The results show that N 1– C 3 bond rotation is the most favorable rotational defect. In addition, the electronic properties of the semiconducting g- C 3 N 4-zz3 nanotube with defects have been studied using band structure and density of states plots.

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Bak, T., J. Nowotny, M. Rekas, and C. C. Sorrell. "Defect chemistry and semiconducting properties of titanium dioxide: II. Defect diagrams☆." Journal of Physics and Chemistry of Solids 64, no. 7 (July 2003): 1057–67. http://dx.doi.org/10.1016/s0022-3697(02)00480-8.

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Nowotny, J., T. Bak, M. K. Nowotny, and L. R. Sheppard. "Defect Chemistry and Electrical Properties of Titanium Dioxide. 1. Defect Diagrams." Journal of Physical Chemistry C 112, no. 2 (January 2008): 590–601. http://dx.doi.org/10.1021/jp074565u.

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Luo, Min, Bo-Lin Li, and Dengfeng Li. "Effects of Divacancy and Extended Line Defects on the Thermal Transport Properties of Graphene Nanoribbons." Nanomaterials 9, no. 11 (November 13, 2019): 1609. http://dx.doi.org/10.3390/nano9111609.

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The effects of divacancy, including isolated defects and extended line defects (ELD), on the thermal transport properties of graphene nanoribbons (GNRs) are investigated using the Nonequilibrium Green’s function method. Different divacancy defects can effectively tune the thermal transport of GNRs and the thermal conductance is significantly reduced. The phonon scattering of a single divacancy is mostly at high frequencies while the phonon scattering at low frequencies is also strong for randomly distributed multiple divacancies. The collective effect of impurity scattering and boundary scattering is discussed, which makes the defect scattering vary with the boundary condition. The effect on thermal transport properties of a divacancy is also shown to be closely related to the cross section of the defect, the internal structure and the bonding strength inside the defect. Both low frequency and high frequency phonons are scattered by 48, d5d7 and t5t7 ELD. However, the 585 ELD has almost no influence on phonon scattering at low frequency region, resulting in the thermal conductance of GNRs with 585 ELD being 50% higher than that of randomly distributed 585 defects. All these results are valuable for the design and manufacture of graphene nanodevices.

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Zhao, Wei Min, Liang Zhang, Zhi Feng Wang, and Hong Ji Yan. "Study on Defects of A356 Aluminum Alloy Wheel." Advanced Materials Research 189-193 (February 2011): 3862–65. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.3862.

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This paper studied the effects of inclusion and slag on properties of a die cast A356 alloy wheel. The result showed that the rate of defect is important for the mechanical properties. The tensile strength and extension was not dropped but the rate of defect is increased about 2%. The variation trend of tensile strength and extension is linear, while the area of porosity on tensile fracture is between 2% and 6%. However, the tensile strength and extension was dropped with the increasing rate of defect. The variation trend of mechanical properties of the sample with inclusion is stable, but the sample with slag is not stable. The mechanical properties of samples with inclusion are drastically changed, while the rate of defect is increased. The mechanical properties of samples with slag are smoothly. The EDS analysis indicated that the defects consist of Al-Ti-B compound, α-phase (Al12FeSi), β-phase (Al9Fe2Si2) and Al2O3. These oxides form the compact composite oxide film expand into first cracks. The fracture mode of sample with defects is brittle fracture. The values of the Secondary dendrite arm spacing (DAS) in the inclusion and the matrix are the same, while the values of DAS in the slag and the matrix are different.

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Journal articles on the topic 'Defect properties'

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