Mechanism and principle of doping: realizing of silver incorporation in CdS thin film via doping concentration effect.

A high-quality buffer layer serves as one of the most significant issues that influences the efficiency of solar cells. Doping in semiconductors is an important strategy that can be used to control the reaction growth. In this study, the influence of Ag doping on the morphological, optical and electrical properties of CdS thin films have been obtained. Herein, we propose the mechanism of CdS film formation with and without Ag ions, and we found that changes in the reaction of preparing CdS by the chemical bath deposition (CBD) method cause a shift in the geometric composition of the CdS film. XRD showed that the position of peaks in the doped films are displaced to wider angles, indicating a drop in the crystal lattice constant. The optical analysis confirmed direct transition with an optical energy gap between 2.10 and 2.43 eV. The morphological studies show conglomerates with inhomogeneously distributed spherical grains with an increase of the Ag ratio. The electrical data revealed that the annealed Ag-doped CdS with 5% Ag has the highest carrier concentration (3.28 × 1015 cm-3) and the lowest resistivity (45.2 Ω cm). According to the results, the optimal Ag ratio was obtained at Ag 5%, which encourages the usage of CdS in this ratio as an efficient buffer layer on photovoltaic devices.

Correction: Mechanism and principle of doping: realizing of silver incorporation in CdS thin film via doping concentration effect.

[This corrects the article DOI: 10.1039/D2RA04790J.].

Mechanical and thermal stress evaluation of PEEK prefabricated post with different head design in endodontically treated tooth: 3D-finite element analysis.

An endodontic post is required to retain and support the core restoration in case of insufficient remaining coronal dentin after root canal therapy. This study analyzed the biomechanical and thermal behavior of PEEK prefabricated post after choosing the head design that produces the least amount of stress on the core and remaining tooth structure. These results were compared with the most common commercially available prefabricated post, which is titanium and glass fiber post. Thus a CBCT scanning of a maxillary central incisor with its supporting structure was used to construct a 3D solid model of an endodontically treated teeth for finite element analysis (FEA). The restored tooth with the spherical head design of PEEK prefabricated post yielded a more benign stress distribution and repairable failure mode on the crown, luting cement, core, and dentin under both mechanical and thermal loads, followed by glass fiber post and titanium post respectively.

Biomechanical finite element analysis of a single implant threaded in anterior and posterior regions of maxilla bone.

CONTEXT: The ability of implant dentistry to be a successful alternative for edentulous patients has increased in the last decade. Clinical features such as osseointegration and stability, in addition to the endurance of the integration urged the researchers towards a better understanding of the design parameters that control long term success of the implants. It is therefore necessary to quantify the effect of changing implant design parameters on interface stress distribution within the maxilla bone. METHODS AND MATERIALS: A 3D-finite element study was conducted to investigate the effect of changing implant shape parameters (implant body design and implant thread depth) on stress distribution while insertion of the implant in two different regions of maxilla bone (anterior (type III bone) and posterior (type IV bone)). A 3D-CAD geometry of implant-maxilla bone was created through importing digitally visualized CT skull images of a human adult, and then converted into a workable solid body through using a collection of engineering software. Tapered and cylindrical implant models with three different implant V-shaped thread depths (0.25 mm, 0.35 mm, 0.45 mm) were threaded into maxilla bone to investigate the design parameters effect on the final stress status. The proposed implant was of commercial dimensions of 10 mm length and 4 mm in diameter. A vertical static load of 250N was directly applied to the center of the suprastructure of the implant for each model. RESULTS: Evaluations were performed for stress distribution patterns and maximum equivalent Von Mises (EQV) stresses for implants in two regions of maxilla bone under 250N vertical static loading. The obtained results throughout this work showed that, for all models, the highest stresses were located at the crestal cortical bone around the implant neck. The von-Mises stress distribution patterns at different models were similar and higher peak von-Mises stresses of cortical bone were seen in tapered implant body compared to cylinder body in all models. CONCLUSIONS: Within the restrictions of the current model, the results obtained can be applied clinically to select properly both implant thread depth and body shape design for a foreseeable success of implant therapy.

Effect of thread depth and implant shape on stress distribution in anterior and posterior regions of mandible bone: A finite element analysis.

BACKGROUND: The ability of modern implant dentistry to achieve goals such as normal contour, function, comfort, esthetics, and health to totally or partially edentulous patients guaranteed it to be more effective and reliable method for the rehabilitation process of many challenging clinical situations. In regard to this, the current study evaluates the effect of changing implant shape design parameters on interface stress distribution within the mandible bone. MATERIALS AND METHODS: A numerical procedure based on finite element (FE) method was adopted to investigate the influence of using different body design and thread depth of the inserted implant on the final stress situation. For the purpose of evaluation, a three-dimensional realistic FE models of mandible bone and inserted implant were constructed and analyzed using a pack of engineering software (Solidworks, and ANSYS). Six different commercial implant models (cylindrical and tapered) with three different V-shaped thread depths (0.25 mm, 0.35 mm, and 0.45 mm) were designed to be used in this study. The suggested implants used in this study were threaded in two different locations of mandible bone; the anterior region (Type I model) and posterior region (Type II model). A vertical static load of 250 N was directly applied to the center of the suprastructure of the implant for each model. RESULTS: For both models, evaluations were achieved to figure out the stress distribution patterns and maximum equivalent von Mises. The results obtained after implementation of FE dental-implant models show that the highest stresses were located at the crestal cortical bone around the implant neck. In addition, the simulation study revealed that taper body implant had a higher peak value of von Mises stress than that of cylinder body implants in all types of bones. Moreover, a thread depth of 0.25 mm showed highest peak of maximum von Mises stresses for Type I and Type II models. CONCLUSION: The simulation results indicate that all models have the same von Mises stress distribution pattern and higher peak von Mises stresses of the cortical bone were seen in tapered implant body in contrast to the cylindrical body.

Conceptual designs of conduction cooled MgB2 magnets for 1.5 and 3.0T full body MRI systems.

Conceptual designs of 1.5 and 3.0 T full-body magnetic resonance imaging (MRI) magnets using conduction cooled MgB2 superconductor are presented. The sizes, locations, and number of turns in the eight coil bundles are determined using optimization methods that minimize the amount of superconducting wire and produce magnetic fields with an inhomogeneity of less than 10 ppm over a 45 cm diameter spherical volume. MgB2 superconducting wire is assessed in terms of the transport, thermal, and mechanical properties for these magnet designs. Careful calculations of the normal zone propagation velocity and minimum quench energies provide support for the necessity of active quench protection instead of passive protection for medium temperature superconductors such as MgB2. A new 'active' protection scheme for medium Tc based MRI magnets is presented and simulations demonstrate that the magnet can be protected. Recent progress on persistent joints for multifilamentary MgB2 wire is presented. Finite difference calculations of the quench propagation and temperature rise during a quench conclude that active intervention is needed to reduce the temperature rise in the coil bundles and prevent damage to the superconductor. Comprehensive multiphysics and multiscale analytical and finite element analysis of the mechanical stress and strain in the MgB2 wire and epoxy for these designs are presented for the first time. From mechanical and thermal analysis of our designs we conclude there would be no damage to such a magnet during the manufacturing or operating stages, and that the magnet would survive various quench scenarios. This comprehensive set of magnet design considerations and analyses demonstrate the overall viability of 1.5 and 3.0 T MgB2 magnet designs.