Elimination Of Defects Research Articles

Synchrotron X‐ray multiscale tomography: Visualization of heterogeneous microstructures and defects in ceramics

AbstractSynchrotron X‐ray multiscale tomography is a three‐dimensional (3D) imaging method that combines microtomography and nanotomography to perform a high spatial resolution measurement with a wide field of view. We show how this method can be used to track the 3D microstructural evolution at multiple length scales in powder processing, sintering, and microfracture of ceramics. Heterogeneity, complexity, diversity, and hierarchical structure of powder compact lead to various types of defects that control the quality, reliability, and lifetime of products. The elimination and formation of defects are affected by applied stress in spark plasma sintering and by internal stresses generated during differential sintering and constrained sintering. The complex subsurface crack system induced by Vickers indentation demonstrates how heterogeneous microstructures control the toughening mechanisms.

Improved Soft Magnetic Properties in FeNi@MgO Composites by Sol-Gel-Based Surface Coating and High-Temperature Heat Treatment

In this study, we utilized MgO as an insulating buffer layer to enhance the thermal stability and soft magnetic properties of Fe-Ni soft magnetic composites (SMCs) and investigated the effect of high-temperature heat treatment on those soft magnetic properties. By employing the sol-gel process, a uniform MgO insulating layer with a thickness of 600 nm was coated onto Fe-Ni magnetic powder. Subsequently, high-density SMCs were fabricated through high-pressure compaction molding. The MgO layer remained intact up to 800 °C, leading to the FeNi@MgO@MK SMCs exhibiting enhanced permeability and reduced hysteresis loss due to grain enlargement and elimination of defects, such as dislocation stacking. Notably, the dynamic loss increase after high-temperature heat treatment was significantly regulated compared to the case of the uncoated counterpart. The results underscore the potential to improve the thermal stability and soft magnetic properties of MgO-coated Fe-Ni SMCs, rendering them suitable for various electromagnetic applications.

Features of Structure and Properties of Lap-Welded Joints of Aluminum Alloy Al–4Cu–1Mg with Titanium Alloy Ti–6Al–4V, Obtained by Friction Stir Welding

Lap-welded joints between Ti–6Al–4V and Al–4Cu–1Mg were obtained using water-cooling-bath friction stir welding at different FSW tool rotation rates. The increase in the tool rotation rate from 350 to 375 RPM leads to better plasticization of the titanium alloy, elimination of stir zone defects, better interlocking and bonding with the aluminum alloy as well as the formation of intermetallic Al–Ti compounds (IMC), preferentially of the Al3Ti type. Shear-loading testing showed the best result was at the level of 3000 N with 2 mm of displacement. Increasing the FSW tool rotation rate to 400 and 450 RPM resulted in the formation of more IMCs, which had a detrimental effect on both maximum load and displacement achieved in the shear tests.

Tailoring the separation performance of a carbon nanotube-based mixed matrix membrane decorated with metal–organic framework

Synthesis of mixed matrix membranes (MMM) using carbon nanotubes (CNTs) has shown great prospects for achieving excellent selective separation because of its special structure. Nevertheless, the preparation of highly selective MMM faces challenges, which is attributed to the obstacles encountered by CNTs dispersion in polymer matrix and elimination of interface defects. A novel CNT-based composite decorated with metal–organic framework (MOF) was synthesized and applied to the preparation of MMM. MOF was post modified, and then carboxyl groups were inserted on the outer surface of CNTs. The synthetic MMM (Cu-MOF-en@MWCNT) not only has selective adsorption on dyes, but also has selective photodegradation on dyes. The method of using CNTs to wrap the outside of MOF has great potential in dye separation. The performance of MMM was further improved by decorating MOF on the filler to improve the selectivity to the designated dye.

Elimination of soft tissue deficiency of the alveolar ridge in the experiment

To date, dental implantation is the most common routine way to restore the continuity of dentition. Additional bone augmentation surgery is required in 50-80% of patients. In order to improve the results and reduce the risks of osseointegration, denudation and rejection of bone autografts, various ways of correcting the deficiency of soft tissues of the alveolar ridge are proposed, which include the use of free soft-woven autografts, the low efficiency of which is due to a high shrinkage coefficient.The purpose of the study: to test an experimental model of a vascularized muco-periosteal flap to eliminate the volume deficit of the soft tissues of the alveolar ridge.Material and methods. On the basis of the vivarium of the Stavropol State Agrarian University (StSAU), 15 biological mannequins (heads of female dwarf pigs) were subjected to a pilot experimental study. The study was conducted in accordance with the decision of the local Ethics Committee of the StSAU, as well as the provision of the World Convention on the Protection of Animals and the Procedure for the Treatment of Experimental Animals adopted by the Helsinki Council in 2002.Results. In the course of the study, the technical stages of the tested intervention were clarified, the metric parameters of the elimination of defects of the alveolar ridge were determined.Conclusion. The results obtained will make it possible to eliminate extended soft tissue defects of the alveolar ridge by increasing the possibility of tissue sampling in the donor bed in a volume not less than 3 times greater than the intake of free palatine flaps.

Quality Evaluation of Al-Rasheed Ready Concrete Mixture Plant By Using Six Sigma Approach

The objective of this research work is to evaluate the quality of central concrete plant of Al-Rasheed Company by using Six Sigma approach which is a measure of quality that strives for near elimination of defects using the statistical methods to improve outputs that are critical to customers. The fundamental objective of Six Sigma methodology is the implementation of a measurement-based strategy that focuses on process improvement and variation reduction to reach delighting customers, and then suggesting an improvement system to improve the production of concrete in Al-Rasheed State Contracting Construction Company. A field survey includes two parts (open and close questionnaire) that aimed to get the data and information required for achieving the research where the answers of questionnaire sample have led, during the application of DMAIC improvement cycle, to identifying the potential possible reasons that caused quality deviations in concrete works. Two programs have been used: First, ‘Sigma Level Calculator’ which is formulated by the researcher to measure the components of the processes performance. Second, ‘QI Macros Lean Six Sigma SPC Software 2011’ which uses the statistical tools of Six Sigma DMAIC methodology for: identifying the root causes of defects, analyzing the data, determining capability and stability of process. It is concluded that the processes sigma level for the concrete works quality is 2.41 σ and 181,070 DPMO which is considered too bad as compared with the current global competitio

High-temperature graphitization characteristics of vitrinite and inertinite

In order to explore the graphitization characteristic differences between vitrinite and inertinite in coal, this study conducted high-temperature thermal simulation experiments (at five temperature points: 1800°C, 2100°C, 2400°C, 2700°C, and 3000°C) using inertinite-rich and vitrinite-rich samples as graphitization precursors. The quantitative comparison for the evolution characteristics of their graphite lattice was carried out using high-resolution transmission electron microscopy (HRTEM), X-ray diffractometer (XRD), and Raman spectroscopy (Raman) techniques. HRTEM revealed that an evident increase in carbon layer numbers and degree of extension was observed with increasing treatment temperature, XRD showed the variation of lattice parameters (d002/La/Lc) with temperature, Raman data revealed the variation of lattice defects (R2/R3) with temperature. It was discussed about the differences of graphite lattice construction processes between inertinite and vitrinite, throughout the entire temperature range of the experiment, the d002 spacing of inertinite was always smaller than that of vitrinite, indicating a higher degree of graphitization. vitrinite exhibited a uniform and smooth evolution state throughout the entire heating process, while inertinite exhibited an “inert” state between 1800°C and 2100°C (d002 values stagnated near at 0.3440 nm). With increasing simulated temperature, the defect level (R2 and R3) of vitrinite rapidly decreased below that of inertinite, throughout the entire temperature range, vitrinite demonstrated superior defect healing ability in terms of both rate and capability compared to inertinite. Under high-temperature thermal simulation, the three-dimensional lattice construction and defect elimination of vitrinite exhibited synchronous evolution characteristics. On the other hand, the formation of the graphite lattice in inertinite showed an evolutionary trend of “first three-dimensional lattice construction, followed by gradual defect elimination”.

Effect of in-situ synthesized TiC particles on microstructure and mechanical properties of directed energy deposited AA2219 Al-Cu alloy

Directed energy deposition (DED) process can enable rapid and low-cost manufacturing of large-scale high-strength AA2219 Al-6.3 wt%Cu alloy components, displaying broad prospects for structural lightweighting in aerospace applications. However, a high tendency to prominent porosity defects and inhomogeneous layered microstructure are intrinsically present in DED-processed Al-Cu alloy, leading to significant performance degradation and anisotropy. Herein, we demonstrate a robust DED process to fabricate high-quality formed AA2219 alloy deposits, based on in-situ synthesized TiC-containing wires and an ultrasonic-frequency pulsed (UFP) arc. The effects of in-situ synthesized submicron-scale TiC particles (average diameter 0.7 ± 0.4 µm) in microstructural evolution and mechanical performance were comparatively investigated through multi-scale microstructural characterization and mechanical property measurement. The introduction of TiC particles into the as-deposited AA2219 component results in a homogeneous refined equiaxed microstructure with an average α-Al grain diameter of 23.4 ± 2.9 µm, and a dramatical elimination of porosity defects. After undergoing a T6 solution and aging treatment, the TiC-reinforced AA2219 deposit demonstrates excellent resistance against grain coarsening, porosity defects growth, and particle segregation. Moreover, the introduced TiC particles lead to a noticeably enhanced precipitation hardening behavior. A homogeneous precipitation microstructure of dispersed θ′-Al2Cu particles with an average diameter of 84.1 ± 34.5 nm and a high fraction of 9.8 ± 2.5 vol% was obtained in the heat-treated AA2219 deposit. Based on the as-built multiscale homogeneous microstructure, the heat-treated deposit embedded with TiC particles exhibits a synergy of unprecedented tensile strength of 501 ± 14 MPa and excellent ductility of 9.6 ± 3.3%.

Clinical and morphological assessment of innervation restoration after defects elimination in patients with oral cancer using functional flaps

Актуальность. Приоритетом при реконструкции органов полости рта после радикального хирургического лечения по поводу злокачественных новообразований (ЗНО) является восстановление таких жизненно важных функций, как глотание, речь, защита дыхательных путей от аспирации и поддержание нормальной внутриротовой чувствительности.Цель. Определить преимущества использования иннервированных аутотрансплантатов на восстановление чувствительности при реконструкции органов полости рта.Материалы и методы. Проведено проспективное исследование 62 пациентов с ЗНО полости рта. Из них 32 человека - опытная группа, в которой выполнялась реконструкция иннервированными лоскутами, и 30 – группа контроля без иннервации. Из субъективных методов оценки применялись: восприятие температурной и болевой чувствительности, тест Вебера, тест Семменса-Вайнштейна, опрос. Для морфологической оценки прорастания нервных волокон в ткани аутотраспланатов выполнялась трепан-биопсия с последующим морфологическим исследованием и иммуногистохимическим (ИГХ) окрашиванием маркерами S100 и NF. Микропрепараты оценивались на предмет наличия и количества нервных структур. Для статистических расчетов использовалась программа StatTech v.3.0.9.Результаты. Были выявлены статистические значимые различия в пользу опытной группы при оценке восприятия температурной чувствительности - 90,6% (29) против 66,7% (20) (p = 0,029); при оценке острой боли - 78,1%(25) против 33,3% (10) (p < 0,001); при тесте Семменса-Вайнштейна - 71,9% (23) против 36,7% (11) (p = 0,005); при оценки дискриминационной чувствительности менее 5 мм – 12,5% (4) против 0%, от 5 до 10 мм - 34,4% (11) против 6,7% (2), более 10 мм - 53,1%(17) против 93,3% (28). При ИГХ различия по качественному показателю различия не были статистически значимыми (р=0,078). Однако, при количественной оценке нервных стволиков в группе иннервированных лоскутов Ме=3 (Q1-0; Q3-5), тогда как в группе неиннервированных лоскутов Ме=0 (Q1-0; Q3-1), (р=0,005). Выводы. Получены статистически значимые различия, подтверждающие, что иннервированные лоскуты превосходят неиннервированные лоскуты по восстановлению чувствительности и количеству нервных волокон.

Effect of CZT Powder Burying CZT Crystal on Annealing in Cd Atmosphere

AbstractDue to the inevitable formation of the second phase of Te in the growth process of Cadmium zinc telluride (CdZnTe/CZT) crystal, the Te related defects are usually treated by Cd atmosphere annealing to improve the crystal quality. In this paper, the influence of different powder burying crystals on the annealing effect in Cd atmosphere is studied by analyzing the change of crystal surface components, removal effect of Te inclusion, electric field distribution and carrier transport characteristics. The results show that burying the crystal with powder helps to maintain the crystal surface composition in annealing, but the Te inclusion can be eliminated only by controlling the amount of powder. Moreover, it is found that the uniformly distributed Te inclusions tend to migrate to the surface during the annealing process, while the Te inclusions at dislocation or crystal boundary are difficult to eliminate. It is speculated that the internal Te loading is more inclined to the reaction of diffused Cd atom, which makes the Te inclusions decrease continuously. After annealing with proper amount of powder, due to the elimination of Te inclusion defects, the electric field distribution inside the crystal is more uniform and the carrier lifetime product is improved.

STUDY ON THE INFLUENCE OF INJECTION MOLDING PARAMETERS ON THE WARPAGE AND SHRINKAGE IN HOT RUNNER SYSTEM MOLD

The good combination of injection molding parameters (IMP) will make high quality product by elimination of defects occurred during injection molding process such as warpage and shrinkage. This paper investigates influence of IMPs on shrinkage and warpage on injection molding process using hot runner system. Taguchi method and ANOVA analysis are used to optimize the IMPs including melt temperature, filling time, injection pressure, packing pressure, coolant inlet temperature, cooling time, and flow rate. The analysis and simulation processes were done by using a Moldflow software. The plastic material is acrylonitrile butadiene styrene (ABS) with some features of the dimensional stability, chemical endurance, and simple processing capacity. The results show that melt temperature and coolant temperature are the main factors affecting the warpage with 66.67% of melt temperature and 15.59% of cooling temperature. The melt temperature and packing pressure are the main factors affecting the shrinkage with 74.62% of melt temperature and 19.46% of packing pressure. The optimal IMP is retested with warpage defect reduced 16.6% and shrinkage decreased of about 2.45% after optimization.

Coexistent improvement of thermal and mechanical performance at Si/Cu joint by thickness-controlled Sn-Ag bond layer

In this study, sound Si-Cu joints with high thermal conductivity and mechanical property were achieved at 260 °C with thickness-controlled Sn-Ag bond layer. The microstructure evolution, thermal and mechanical properties were proposed systematically. The bond layer was fabricated by micro electroforming technology to precisely control the thickness and improve the bond ability. The electroformed Ag layer could protect the sputtered Cu film and restrict the diffusion of Cu elements, which could decrease the residual stress and remove the interface defects. At the joints, the electroformed Sn layer was consumed to form Ag3Sn and Cu6Sn5 intermetallic compounds. The thermal conductivity and shear strength both increased firstly and then decreased with the thickness of bond layer increasing. The highest thermal conductivity of 283.21 W/(m·K) and shear strength of 88.74 MPa were achieved synchronous with 15-μm-thickness Sn-Ag bond layers, which were attributed to the reduction of the interface stress and elimination of interfacial defects. This technology had potential to be applied in the microelectronic heat dissipation at the future.

Interface formation and defect elimination mechanism of T2/304L interface during electromagnetic pulse welding process

Experimental and numerical methods are carried out to analyze the interface formation and defect elimination mechanism during electromagnetic pulse welding T2 to 304L tube by changing the inner tube morphology from original scheme to stage scheme, ramp stage, and location stage. When the original scheme is operated with 13mm lap length, the morphology of interface is divided into four zones containing end unwelded zone, first welded zone, central unwelded zone, and second welded zone due to the different impact velocity and angle during the initial impact process, parallel impact process, and final impact process. The parallel impact leads to the formation of the central unwelded zone, containing (Cu, Fe) solid solution, oxides, nano grains, and amorphous phase. By providing a suitable impact angle, the ramp scheme (α = 7°) and location scheme (L = 6.5 mm) can eliminate the defect in the central unwelded zone.

Irremovable Mn-Bi Site Mixing in MnBi2Te4.

MnBi2Te4, an antiferromagnetic topological insulator, was theoretically predicted to have a gapped surface state on its (111) surface. However, a much smaller gapped or even gapless surface state has been observed experimentally, which is thought to be caused by the defects in MnBi2Te4. Here, we have theoretically identified the antisite MnBi and BiMn as dominant defects and revealed their evolution during the phase transition from MnTe/Bi2Te3 to MnBi2Te4. We found that the complete elimination of MnBi and BiMn defects in MnBi2Te4 by simple annealing is almost impossible due to the high migration barrier in kinetics. Moreover, the gap of the Dirac point-related bands in a MnBi2Te4 monolayer would be eliminated with an increasing concentration of MnBi and BiMn defects, which could explain the experimentally unobserved large-gap surface state in MnBi2Te4. Our results provide an insight into the theoretical understanding of the quality and the experimentally measured topological properties of the synthesized MnBi2Te4.

Elimination of defects in laser metal deposited TiCp/Ti6Al4V composite by synchronous ultrasonic impact treatment

TiCp/Ti6Al4V composites produced by laser metal deposition (LMD) are usually characterized by internal defects and resultant deteriorated mechanical properties. In the present work, a synchronous ultrasonic impact treatment (UIT) was introduced during LMD of TiCp/Ti6Al4V composites. The effect of synchronous UIT on the defects was investigated. The defects in the LMDed composites are sub-spherical pores distributed in the interlayer region. With the assistance of UIT, the maximum surface height difference reduces from 200.2 ± 0.5 μm to 25 ± 0.5 μm and the internal porosity decreases from 1.95% to 0.09%, which is attributed to inhibiting the nucleation of defects and increasing molten pool flow. This work may provide a solution to effectively reduce the defects in additively manufactured parts.

EVALUATION OF THE RESULTS OF TESTING THE HARDWARE COMPARTMENT OF SUBORBITAL ROCKETS FOR RELIABILITY

Nowadays, the issue of creating modern models of rocketry is becoming more and more popular due to the constant development of technologies and competition in the domestic market. This paper describes the results of the behavior of on-board electronic equipment during launches of ultra light suborbital rockets of the «Meteo» series manufactured by the Rocketry agency project. When designing the hardware compartment
 and further improving it in subsequent rocket models, the first place is occupied by its level of reliability, which should in turn take into account the economic part for the development and manufacture of further products. Such improvements included the use of new materials, increased strength and resistance to negative impacts, improved thermal management and elimination of structural defects. Tests have shown that to overcome higher altitudes, such as the Karman Line, more fuel is used and the mass and size characteristics of the rockets change, which leads to increased complexity of their control and navigation. One of the key challenges is the lack of an effective control system. Without a proper control system, a missile's flight becomes unpredictable and dangerous for the area where it is flying. One way to solve this problem is to develop and test a proper control system for the missile on a special test bed that will allow testing and debugging the control system in a controlled environment that ensures its functioning in real-world conditions without the risk of sending an untested missile into the air.

Eliminating lattice defects in metal-organic framework molecular-sieving membranes.

Metal-organic framework (MOF) membranes are energy-efficient candidates for molecular separations, but it remains a considerable challenge to eliminate defects at the atomic scale. The enlargement of pores due to defects reduces the molecular-sieving performance in separations and hampers the wider application of MOF membranes, especially for liquid separations, owing to insufficient stability. Here we report the elimination of lattice defects in MOF membranes based on a high-probability theoretical coordination strategy that creates sufficient chemical potential to overcome the steric hindrance that occurs when completely connecting ligands to metal clusters. Lattice defect elimination is observed by real-space high-resolution transmission electron microscopy and studied with a mathematical model and density functional theory calculations. This leads to a family of high-connectivity MOF membranes that possess ångström-sized lattice apertures that realize high and stable separation performance for gases, water desalination and an organic solvent azeotrope. Our strategy could enable a platform for the regulation of nanoconfined molecular transport in MOF pores.

Grain-boundary/interface structures and scatterings of ruthenium and molybdenum metallization for low-resistance interconnects

Ruthenium and molybdenum are of great potential to replace copper for use as the next-generation interconnect metallization. Important parameters including their intrinsic resistivity, grain-boundary reflectivity and interface permeability need to be carefully examined. Hence in this study, ruthenium and molybdenum films with various thicknesses were prepared on different substrates by physical vapor, chemical vapor and atomic layer depositions. The microstructure, chemical compositions, bonding configurations and interfacial adhesion were characterized, and the electrical resistivities with scaling was examined using the Fuchs-Sondheimer and Mayadas-Shatzkes models. Experimental results indicate that the grain-boundary reflectivity was strongly influenced by the structure coherency and impurity (oxygen) segregation. Thermal annealing facilitated defect elimination and structure recovery, lowering the intrinsic resistivity and the grain boundary reflectivity. Strong interface bonding caused serious interface diffuse scattering, and an inverse proportional relationship between interfacial adhesion strength and interface permeability was suggested, which was dominated by the electronegativity of the metals.

Prevention of Cu Electrolytic Migration Defects on RDL by a Cu-Selective Passivation to Enhance Reliability

Copper (Cu) is the metal of choice for the redistribution layer (RDL) to facilitate fast I/O communication in an integrated circuit (IC). Cu can electrochemically migrate (ECM) between the array of electrodes under bias, electrolyte, and moisture. IC packages fail miserably when exposed to various ion impurities and moisture. Copper at the anode dissolves to form Cu+1, +2 ions. As the anodic dissolution continues, the concentration of copper ion increases. These anions deposit on cathode leading to Cu dendrite formation. To achieve the near zero ppb defectivity goal, elimination of (ECM) defects in packaged devices is critical. This work discusses development of a novel Cu-selective passivation and a method to accelerate reliability testing. A hydrophobic passivation with minimum stress to the IC package is proposed in this work. The new passivation coating is thermally stable, strongly adheres to Cu, corrosion resistant, low cost and shows good potential to prevent ECM defects. The coated packaged devices were tested by an accelerated PEG drop test (PDT) to explore its ECM prevention capabilities.

Fabrication of the novel hybridized AZ31B Mg/CeO2+ZrO2 composites via multiple pass friction stir processing

The mixture of the rare-earth CeO2 and ZrO2 particulates was used for fabricating the hybridized AZ31BMg/(CeO2+ZrO2)p composites by utilizing friction stir processing with a multiple-tool pass strategy. The structure, mechanical properties (tensile strength and hardness), tribological performances (wear properties) and corrosion behaviours of the hybrid composites were examined. The findings reveal the elimination of tunnel-like defects and clustering of the CeO2+ZrO2 particles in the composite after the multiple passes of the tool due to the successive mechanical stirring-assisted material flow. The rise in the tool passes reduced the mean grain sizes (7.91–3.02 μm), the particle sizes (5.47–2.28 μm), the average friction coefficient (0.45–0.18) and the specific wear rate (4.26 × 10−5–2.17 × 10−5 mm3/Nm) of the composite. The tensile strength (172–239 MPa), and the corrosion performance of the hybrid composite were also improved via the multiple tool pass strategy. Multiple tool pass is thus recommended for the fabrication of Mg-based hybrid composites.