Moderate Dislocation Research Articles

Research on the Coupled and Coordinated Development of Tourism and Transport in Chengdu City

Based on a total of 16 indicators selected from the tourism and transport industries, an evaluation index system of the coupling and coordination development level of tourism and transport is constructed. The entropy value method and the coupling coordination degree model are used to conduct an empirical study on the development level and coupling coordination level of the transport and tourism industries in Chengdu City from 2011 to 2020. The results show that, on the whole, the coupling coordination degree of transport and tourism in Chengdu is poor and has been in a state of mild to moderate dysfunction. The development level of tourism lagged behind the development of transport from 2011 to 2012, and the two were in a state of mild dysfunction. However, from 2013 onwards, the development level of tourism was prioritized over the development level of transport. This shift caused the coupling coordination degree of the two industries to decline sharply to 0.23305 in 2013. The development level of the tourism industry increased again, reaching 0.34206 in 2019, which marked an improvement. Consequently, the coordination degree of the transport and tourism industries evolved from moderate dislocation to mild dislocation. Finally, the results of the empirical research are analyzed, and corresponding suggestions are put forward to promote the sustainable growth of the transport and tourism industries in Chengdu City. These suggestions aim to improve the coupled and coordinated development level of the two industries.

Experimental Investigations on Joining of Equal Channel Angular Pressed Structural Steel IS2062 with Friction Welding Method

In this study, the equal channel angler pressed (ECAPed) structural steel (IS2062) samples were joined by friction welding, and mechanical properties were analysed. The single-pass ECAP process was conducted at ambient (room temperature-RT) and hot (H) condition. The as-received, H-ECAPed and RT-ECAPed samples exhibit strengths of 422 MPa, 730 MPa and 662 MPa, respectively, after welding. The fractography analysis shows a ductile mode of failure in the as-received and RT-ECAPed samples. In the H-ECAPed sample, a brittle fracture occurs in the welding interface. This result confirms that the H-ECAPed sample has a higher strength than the weldment. Microstructural analysis shows that the weldment has finer grains than the ECAPed samples. However, the microhardness survey reveals that the weldment has a lower hardness. This is due to the presence of a moderate dislocation density in the different zones, which is confirmed through the transmission electron microscope (TEM). From the overall observation, the sample which has been H-ECAPed followed by friction welding is found to exhibit better mechanical properties than the other samples.

Parallel Dislocation Networks and Cottrell Atmospheres Reduce Thermal Conductivity of PbTe Thermoelectrics

AbstractDislocations play an important role in thermal transport by scattering phonons. Nevertheless, for materials with intrinsically low thermal conductivity, such as thermoelectrics, classical models require exceedingly high numbers of dislocations (>1012 cm–2) to further impede thermal transport. In this work, a significant reduction in thermal conductivity of Na0.025Eu0.03Pb0.945Te is demonstrated at a moderate dislocation density of 1 × 1010 cm–2. Further characteristics of dislocations, including their arrangement, orientation, and local chemistry are shown to be crucial to their phonon‐scattering effect and are characterized by correlative microscopy techniques. Electron channeling contrast imaging reveals a uniform distribution of dislocations within individual grains, with parallel lines along four <111> directions. Transmission electron microscopy (TEM) shows the parallel networks are edge‐type and share the same Burgers vectors within each group. Atom probe tomography reveals the enrichment of dopant Na at dislocation cores, forming Cottrell atmospheres. The dislocation network is demonstrated to be stable during in situ heating in the TEM. Using the Callaway transport model, it is demonstrated that both parallel arrangement of dislocations and Cottrell atmospheres make dislocations more efficient in phonon scattering. These two mechanisms provide new avenues to lower the thermal conductivity in materials for thermal‐insulating applications.

Dynamical X-ray diffraction imaging of voids in dislocation-free high-purity germanium single crystals.

White-beam X-ray topography has been performed to provide direct evidence of micro-voids in dislocation-free high-purity germanium single crystals. The voids are visible because of a dynamical diffraction contrast. It is shown that voids occur only in dislocation-free parts of the crystal and do not show up in regions with homogeneous and moderate dislocation density. It is further suggested that the voids originate from clustering of vacancies during the growth process. A general method is proposed to verify the presence of voids for any crystalline material of high structural perfection.

Use of biomass for a development of nanocellulose-based biodegradable flexible thin film thermoelectric material

In this work, we used solar energy converted via photosynthesis into chemical energy of the biomass of the fast-growing perennial herb Miscanthus × giganteus for the manufacture of nanocellulose (NC) films, which are biodegradable alternative to common petroleum-based polymer substrates used in flexible electronics. To create the NC substrates, we applied an environmentally friendly method of organosolv delignification of plant raw materials carried out at a low temperature and in a relatively short time. Then by means of the low-temperature cheap and scalable method Successive Ionic Layer Adsorption and Reaction (SILAR) we deposited copper iodide (CuI) film of 0.72 µm thickness on both sides of the 12 µm thick NC substrate, and thus obtained light-weight and flexible biodegradable nontoxic thermoelectric material CuI/NC. Crystal structure, morphology, chemical composition, and optical, electrical and thermoelectric properties of the CuI/NC have been researched. Studies have shown that nanostructured p-type semiconductor CuI film in the CuI/NC TE material is quite dense and completely covers the NC surface. It has typical optical direct band gap ≈ 3.0 eV, is single-phase γ-CuI with crystallite sizes in the 19–25 nm range, with moderate dislocation density of (1.6–2.8) × 1015 lines/m2, and tolerable microstrains ε of (4–9) × 10−3 a.u. The determined value of the Seebeck coefficient S is ~228 μV K−1, at that, S is constant in the temperature range 290–335 K. Together with the thermoelectric power factor ≈ 36 μW·m−1·K−2it is favorable for the use of CuI/NC as new thermoelectric material for an in-plane design of biodegradable flexible thin film thermoelectric generator (TEG). At temperature gradient of 50 K, the single p-CuI thermoelectric leg made from CuI/NC strip of 3 cm long and 0.5 cm wide generates open circuit voltage 8.4 mV, short circuit current 0.7 µA and maximum output power 1.5 nW. It corresponds to the output power density 10 µW/m2, and thus confirms the suitability of CuI/NC to obtain electricity by the harvesting the waste environmental heat.

The effect of the annealing temperature on the damping capacity under constant prestress, mechanical properties and microstructure of an Fe–11Cr-2.5Mo-0.1Zr-1.0Ni forged damping alloy

A new Fe–11Cr-2.5Mo-0.1Zr-1.0Ni forged damping alloy with dual phases of ferrite and martensite was obtained by an applicable heat treatment to improve the damping capacity under constant prestress. The effect of the annealing temperature on the damping capacity under constant prestress, mechanical properties and microstructure of the alloy was investigated and compared with that of an Fe–16Cr-2.5Mo-0.1Zr forged damping alloy. The Fe–11Cr-2.5Mo-0.1Zr-1.0Ni forged damping alloy annealed at 900 °C comprised dual phases of ferrite and martensite, while the Fe–16Cr-2.5Mo-0.1Zr forged damping alloy annealed at 900 °C comprised single-phase ferrite. The damping results showed that the damping capacity attenuation of the Fe–11Cr-2.5Mo-0.1Zr-1.0Ni forged damping alloy annealed at 900 °C was apparently slower than that of the Fe–16Cr-2.5Mo-0.1Zr forged damping alloy annealed at 900 °C with an increase in the constant prestress. When the strain amplitude γ was 3.88 × 10−5, the damping capacity Q−1 (0.038) of the Fe–11Cr-2.5Mo-0.1Zr-1.0Ni forged damping alloy annealed at 900 °C under a 40 MPa constant prestress maintained 71.7% of that (0.053) of the alloy under an 8 MPa constant prestress. However, the damping capacity Q−1 (0.017) of the Fe–16Cr-2.5Mo-0.1Zr forged damping alloy annealed at 900 °C under a 40 MPa constant prestress was only 35.4% of that (0.048) of the alloy under an 8 MPa constant prestress. According to the TEM results, the ferrite zone in the Fe–11Cr-2.5Mo-0.1Zr-1.0Ni forged damping alloy annealed at 900 °C had not only a moderate dislocation density but also dislocation lines that were almost parallel to each other and moved easily. It can be concluded that the dislocation damping of the Fe–11Cr-2.5Mo-0.1Zr-1.0Ni forged damping alloy annealed at 900 °C was effectively activated and increased as the constant prestress increased.

Long-term Results of the Open Latarjet Procedure for Recurrent Anterior Shoulder Instability in Patients Older Than 40 Years

Background: Subgroup analyses of the Latarjet procedure have suggested that age over 40 years is a risk factor for dislocation arthropathy. Purpose: To analyze long-term results of the open Latarjet procedure for recurrent anterior shoulder dislocation in patients at least 40 years of age. Study Design: Case series; Level of evidence, 4. Methods: A total of 39 consecutive patients (40 shoulders) with a mean age of 48 years (range, 40-66 years) at surgery were evaluated at a mean follow-up of 11.0 years (range, 8-16 years). Of these, 15 patients (38%) had undergone previous soft tissue stabilization surgery. Long-term results were assessed clinically and radiographically, including computed tomography scanning at final follow-up. Results: No recurrence of dislocation was noted. Subluxation had occurred in 3 patients (8%), and apprehension persisted in 5 patients (13%). The total Walch-Duplay score averaged 89 points at the final follow-up, and the mean Subjective Shoulder Value (60%-91%) had improved significantly (P < .001). In total, 36 patients rated their result as excellent, 3 as good. Further, 6 patients (15%) underwent joint-preserving reoperation, and 1 patient (3%) had reverse total shoulder arthroplasty for severe dislocation arthropathy. Dislocation arthropathy was severe in 14 patients (37%) and had progressed by at least 2 grades in 17 patients (45%). Patients with severe dislocation arthropathy had already shown degenerative changes preoperatively as opposed to those who ultimately had no or moderate dislocation arthropathy (n = 24) (P < .001). Progression of dislocation arthropathy was associated with lateral (>1 mm) graft positioning (P < .001) and older age at surgery (r = 0.58; P < .001). Conclusion: The open Latarjet procedure for recurrent anterior shoulder instability in patients older than 40 years reliably restores stability and leads to high patient satisfaction. This procedure is, however, associated with a substantial rate of advanced but clinically mild symptomatic dislocation arthropathy, which is associated with the degree of preoperative joint degeneration, older age at surgery, and lateral graft placement.

Recombination properties of dislocations in GaN

The recombination activity of threading dislocations in n-GaN with different dislocation densities and different doping levels was studied using electron beam induced current (EBIC). The recombination velocity on a dislocation, also known as the dislocation recombination strength, was calculated. The results suggest that dislocations in n-GaN giving contrast in EBIC are charged and surrounded by a space charge region, as evidenced by the observed dependence of dislocation recombination strength on dopant concentration. For moderate (below ∼108 cm−2) dislocation densities, these defects do not primarily determine the average diffusion length of nonequilibrium charge carriers, although locally, dislocations are efficient recombination sites. In general, it is observed that the effect of the growth method [standard metalorganic chemical vapor deposition (MOCVD), epitaxial lateral overgrowth versions of MOCVD, and hydride vapor phase epitaxy] on the recombination activity of dislocations is not very pronounced, although the average diffusion lengths can widely differ for various samples. The glide of basal plane dislocations at room temperature promoted by low energy electron irradiation does not significantly change the recombination properties of dislocations.

Thick CVD diamond films grown on high-quality type IIa HPHT diamond substrates from New Diamond Technology

The suitability of type IIa diamonds prepared by High Pressure High Temperature (HPHT) in cubic presses at New Diamond Technology was assessed as substrates for the growth of thick detector-grade quality Chemically Vapour Deposited (CVD) diamond films. The substrates were found to possess a moderate dislocation density of about 103cm−2 and a reduced amount of residual impurities as compared to standard type Ib crystals. Using these diamonds as seeds for homoepitaxial growth, CVD films with improved structural characteristics were obtained although extended defects could not be completely prevented from forming and propagating. Their performance as detectors for β radiation was however improved leading to almost full charge collection which shows significant improvement as compared to CVD films grown under the same conditions on standard Ib HPHT diamonds. The availability of this new material source opens the way to the fabrication of higher quality CVD material for electronics applications.

Deformable and wearable carbon nanotube microwire-based sensors for ultrasensitive monitoring of strain, pressure and torsion.

Human joints have the ability to recover their mechanical functions after moderate dislocation. This remarkable capability inspired us to develop a "bone-skin-like" mechanosensor that can detect multiple mechanical deformations after recovery from electrical disconnection. To create this sensor, we embedded a low-strength, wet-spun single-walled carbon nanotube wire in polydimethylsiloxane. When various mechanical stimuli are applied, the wire gets fragmented and its resistance increases dramatically (from 360 Ω to practically infinity) in a reversible, recoverable manner even after the electrical failure/disconnection. The sensor is sensitive enough (a gauge factor of 105 at 15% uniaxial strain, a pressure sensitivity of 105 MPa-1 at 0.9 MPa pressure and a torsion sensitivity of 860 at a twisting angle of 60°) to be used for accurate sensing of a variety of deformation modes, suggesting a wide range of applications in wearable and deformable mechanical sensors.

Freestanding single crystal AlN layers grown using the SiC substrate evaporation method

The physical vapor transport growth of aluminium nitride (AlN) layers was performed in one process with the evaporation of silicon carbide (SiC) substrates. In this paper, we show that the rate of SiC evaporation is slow in a narrow process window for AlN growth but increases in the presence of AlN vapor. The properties of the substrates influence the evaporation process; therefore an investigation is done to understand this phenomenon. We first describe the evaporation behavior of a SiC substrate depending on its size, thickness, structure and polarity. Then we demonstrate the surface morphology and structural quality of the AlN layers grown on C-polar SiC. In the case of a step-flow growth, our method allows us to obtain thin freestanding layers with moderate dislocation densities and rocking curve widths comparable to those of bulk crystals.

Effect of Friction Stir Welding on Microstructure of a 5024 Alloy

Influence of friction stir welding (FSW) on microstructure of an Al-4.57Mg-0.35Mn-0.2Sc-0.09Zr (wt. pct.) alloy was studied. Following parameters of FSW were used: the rotation speeds of 500, 650 and 800 rpm, the traverse speed of 75 mm/min and the tilt angle of 2.5°. Defect-free welds were obtained using all these parameters. FSW leads to the formation of fully recrystallized microstructures with average grain sizes less 2 μm and a moderate dislocation density of ~1013 m–2 in the stir zone. No evidence for abnormal grain growth was found in the heat affected zone of the weld. The nanoscale Al3(Sc,Zr) dispersoids coarsened to 21 nm but retained coherent interfaces and cube-cube orientation relationship with the matrix.

Twinning-detwinning assisted reversible plasticity in thin magnesium wires prepared by one-step direct extrusion

The present study examines the micromechanisms of plastic deformation in magnesium wires with diameters of 250μm, which were prepared by one-step direct extrusion with a high reduction ratio of 576:1 at a temperature of 577K. It is shown that small wire diameter combined with appropriate microstructure (grain size 14±2μm and strong texture) can yield convenient mechanical properties even in pure Mg. Reversible bending plasticity is achieved by abundant 101̅2 twinning-detwinning of selected variants in the compression zone and moderate dislocation activity in the tensile zone of bended wires. The 101̅2 twinning during bending is facilitated by the medium grain size and by the strong texture with the c-axis of grains roughly perpendicular to the extrusion direction. Intense or repeated plastic bending of wires results in twinning-induced grain refinement in the compression zone. Tensile tests conducted at room temperature and at strain rates of 10−3 and 10−1s−1 reveal maximum true stresses of 198±2 and 246±4MPa and ductility values of 10 and 8%, respectively. In contrast with bending, tensile deformation of wires almost exclusively includes dislocation mechanisms, and a minor contribution of any twinning mode is observed.

Friction-stir welding of an Al–Mg–Sc–Zr alloy in as-fabricated and work-hardened conditions

The effect of prior work hardening on the microstructure and mechanical properties of a friction-stir welded (FSWed) Al–5.4Mg–0.2Sc–0.1Zr alloy was investigated. The microstructure of the final stir zone was shown to be weakly dependent on the initial condition of the base material; FSW led to the formation of fully recrystallized microstructures with average grain sizes ranging from 1.2 to 1.5μm and a moderate dislocation density of ~3.5±1.5×1013m−2 in the stir zone. The nano-scale Al3(Sc,Zr) dispersoids coarsened from 9 to ~15nm but retained a coherent relationship with the matrix. In contrast, the joint efficiency of the obtained welds was very sensitive to the initial material condition. Nearly full strength joints were obtained in both annealed (O) and partially hardened and stabilized (H323) conditions. However, the joint efficiency was only 65% in the fully hardened condition (H18). The relatively low weld strength for the alloy in the H18 condition was attributed to the elimination of dislocation and substructure strengthening during FSW.

Dislocation Analysis of a New Method for Growing Large-Size Crystals of Monocrystalline Silicon Using a Seed Casting Technique

A new method is proposed for growing large-size crystals of monocrystalline silicon using a seed casting technique. The stress and dislocation distributions for this type of growth during crystallization were simulated. The results indicate that the order of dislocation density is not very large. If the cooling flux of the crystal growth is controlled to be small at the initial stage, and the annihilation and direction effects of dislocation in the Alexander and Haasen model are included, the real dislocation density could be considerably smaller than the calculated value. Therefore, the new growth method for monocrystalline silicon is promising for complete single crystal growth, effectively avoids polycrystalline nucleation, and has a moderate dislocation density.

Irreducible lateral knee dislocation with incarceration of the lateral femoral condyle in the posterolateral capsuloligamentary structures: a case report and literature review

Knee dislocations are relatively rare 1 , often associated with neurovascular injury, and usually amenable to closed reduction 2 . The irreducible knee dislocation is an even rarer occurrence 3 , 4 . Irreducibility of a knee dislocation is usually due to the medial femoral condyle being buttonholed through the gap formed by medial capsuloligamentary structures. We have treated a rare irreducible dislocation of the left knee in which the neurovascular status was intact. MRI revealed entrapment of the posterolateral capsuloligamentary structures in the intercondylar notch. Emergency operation was performed to reduce the dislocation and reconstruct the injured ligaments. We have described the case in order to present the characteristics of this dislocation and guidelines for its diagnosis and treatment.

Equilibrium and passing properties of dislocation dipoles

Static and dynamic properties of dislocation dipoles are investigated under isotropic and anisotropic elasticity. In elastically isotropic systems for a dislocation character between 35 and 40°, a dipole assumes the same stress-free equilibrium angle of 90° as the screw dipole. This can be affected by elastic anisotropy, as in Cu where the equilibrium angle assumed by a screw dipole (≈59°) is unchanged up to a dislocation character of 22°. In contrast, the static properties of near-edge dislocation dipoles are little influenced by elastic anisotropy. Certain dipole passing properties, not the passing stress however, are also modified by elastic anisotropy. For large heights and/or in the case of undissociated dislocations, the minimum passing stress corresponds to a dipole character of ∼60° and it exhibits a sharp maximum in screw orientation. Reasonably moderate dislocation reorientations should facilitate the passing of near-screw dislocations in fatigue channels. Within a certain range of applied stresses, the passing of dipoles, comprised of unlike attractive dislocations, is accompanied by the sweeping of one dislocation by the other over a limited distance. Dissociation plays a prominent role in determining both static and dynamic properties for dipole heights less than a few times the dissociation distance of an isolated dislocation.

Microstructure and Precipitation Behavior of Nb, Ti Complex Microalloyed Steel Produced by Compact Strip Processing

A comprehensive microstructure analyses were conducted for CSP processed Nb, Ti microalloyed steel, especially focusing on the precipitation behavior of the microalloying elements Nb and Ti. After coiling, the steel exhibits mainly a ferrite microstructure. The average ferrite grain size is 5.3 μm. The ferrite has a transitional morphology from polygonal ferrite to non-polygonal ferrite and is characterized by a moderate dislocation density of 2.47E+10/cm2. A high density of Nb, Ti complex star-like or cruciform shaped precipitates exist in the steel. They are Nb-rich and the average size is around 150 nm. About 49% Nb of the total in the steel is tied up in star-like precipitates, thus remarkably reducing the amount of Nb available for austenite conditioning, transformation temperature control and precipitation as small strengthening particles in ferrite. The main strengthening mechanisms found in the steel are the grain refinement and dislocation strengthening. Of the total yield strength, they represent contributions of 44% and 24%, respectively. There is a very little precipitation strengthening in the steel. It is thought that Nb, Ti complex star-like precipitate is prone to form in Ti-containing niobium microalloyed steel produced by compact strip processing.

Synthetic fluid inclusions. XV. TEM investigation of plastic flow associated with reequilibration of fluid inclusions in natural quartz

The nature and abundance of dislocations in quartz surrounding fluid inclusions were studied to obtain a better understanding of processes associated with fluid inclusion reequilibration. Synthetic fluid inclusions containing 10 wt% NaCl aqueous solution were formed in three samples at 700 °C and 5 kbar. One of the samples was quenched along an isochore to serve as a reference sample. The other two samples were quenched along a P-T path that generated internal pressures in excess of the confining pressure. The two samples were held at the final reequilibration P-T conditions of 625 °C and 2 kbar for 30 and 180 days, respectively. Following the experiments, microstructures associated with fluid inclusions were examined with the TEM. Quartz in healed fractures in the reference sample that was quenched isochorically shows a moderate dislocation activity. Quartz adjacent to reequilibrated fluid inclusions in the other two samples, however, showed a marked increase in dislocation activity compared to the un-reequilibrated sample. Deformation of the inclusion walls occurred anisotropically by expansion of mobile dislocations in their slip systems. Dislocation expansion was controlled by glide in the rhombohedral planes {1 0 1 1} that was restricted to narrow zones (≤3 μm) in the immediate vicinity of the fluid inclusion walls outside of the healed fracture plane. These plastic zones were observed after both short term (30 days) and long term (180 days) experiments and are attributed to hydrolytic weakening of quartz around fluid inclusions owing to diffusion of water into the quartz matrix during the experiment. The close spatial association of submicroscopic water bubbles with dislocations, and the rarity of water bubbles in the reference sample, show clearly that in both the 30 and 180 day experiments reequilibration involves water loss from the fluid inclusions. Our results indicate that synthetic fluid inclusions in this study recover (chemically and volumetrically), even at relatively fast experimental loading rates, such that internal stresses never reach the point of brittle failure. The driving force for fluid inclusion deformation involves two related mechanisms: plastic deformation of hydrolytically weakened wet quartz in the healed fracture, and water leakage associated with preexisting and strain-induced dislocations.

Response to phosphorus gettering of different regions of cast multicrystalline silicon ingots

Minority carrier lifetimes were measured to determine the effect of phosphorus gettering on cast multicrystalline silicon solar cell substrates from central and end regions of two different ingots. One ingot exhibited visibly inferior crystallographic structure and, correspondingly, showed lower lifetimes. Wafers from the bottom region of both ingots improved significantly after gettering, whilst those from the top experienced no lifetime increase. Defect etching revealed that the wafers from the top had very high dislocation densities (>10 6 cm −2), whereas wafers from the bottom had low dislocation densities (10 4 cm −2). Novel cross-contamination experiments showed that all top and bottom wafers contained high concentrations of mobile (and hence getterable) impurities in comparison to central regions, irrespective of dislocation density. For the case of the highly dislocated samples, a sufficient number of recombination centers remains to prevent an increase in the lifetime, even after the mobile impurities have been extracted through gettering. Wafers from central regions had both moderate dislocation densities and low concentrations of out-diffusible impurities. Their lifetimes increased after gettering up to a more evenly distributed limit imposed by the crystallography, which was found to be ingot and region dependent.