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Machinability of Ni-based Superalloys by Indexable End Mills

forgácsolhatóság meghatározásának módszerei Ni-bázisú szuperötvözetek horonymaráskor . Gépgyártás 55(2). (2015) 125–129. [4] Zhu D., Zhang X., Ding H.: Tool wear characteristics in machining of nickel-based superalloys. International Journal of Machine Tools & Manufacture 64. (2013) 60–77. https://doi.org/10.1016/j.ijmachtools.2012.08.001 [5] Lendvai János: Szuperötvözet egykristályok–drágakövek a gázturbinákban . Fizikai Szemle 2006/10. [6] Qi Y., Zhang Y., Zhang W., Gao J., Yuan Z., Bu W., Li Y., Guo S.: Hydrogen storage thermodynamics and kinetics of RE

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Investigation of Laser Welding Technology of Diamond Drilling Segments

References [1] Vincent C.: Apparatus and Method for Securing Diamond Segment to Rotating Tool. US 2005/0279533 A1, 2005. [2] Bagyinszki Gy., Bitay E.: Hegesztéstechnika I. Eljárások és gépesítés . EME, Cluj-Napoca, 2010. https://eda.eme.ro/handle/10598/15437 [3] Kovács T.: Laser welding process specification base on welding theories . Procedia Manufacturing, 22. (2018) 147–153. [4] Bitay E.: Lézeres felületkezelés és modellezés . EME, Cluj-Napoca, 2007. https://eda.eme.ro/handle/10598/8923 [5] Bagyinszki Gy., Bitay E.: Nagy

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Addictive and Substractive Combined Production of Cobalt-Crome-Based Frames in Dentistry

Abstract

The following study analyses the use of modern 3D printing technology in dentistry with its necessary manufacturing and machining processes. Fitting of the manufactured metal structures is examined depending on their use, in terms of conventional adhesion-based denture designs and screw-fixed dentures on implants. Influencing factors and effects of the required post-processing steps are examined. Aspects such as sand-blasting, heat treatment, equipment and tools required for cutting are analyzed. The aim of this study is to create a manufacturing process that enables the required precision fitting of the created frame structure types.

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Irregular shaping of polystyrene nanosphere array by plasma etching

Abstract

The morphology of nanospheres is crucial for designing the nanofabrication in the nanosphere lithography. Here, by plasma etching, the controllable tailoring of the nanosphere is realized and its morphology dependence on the initial shape, microscopic roughness, and the etching conditions is investigated quantitatively. The results show that the shape evolution strongly depends on the etching gas, power, and process duration. Particularly, the aspect ratio (diameter/height) significantly increases with violent etching, turning the spherical shape into tiny ellipsoidal nanoparticles. The findings are practical to the protocol of non-uniform etching of nanoobjects and provide the useful design tool for the device fabrication at nanoscale.

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Photodecomposition of Rhodamine B on TiO2/SiO2 thin films prepared by sol-gel method

Abstract

Glasses showing catalytic effect have been of much interest recently because the catalytic layer is very effective in reducing of pollutants. The use of these glasses may bring reduction in cleaning costs. There are several methods of preparation of TiO2 with good catalytic properties, but sol-gel technique offers an opportunity to enhance catalytic effect by precise optimization of the composition and microstructure of the layer. This study concerns optimization of the composition and preparation technology of catalytic layers based on SiO2-TiO2 system. Catalytic effect was studied using Rhodamine B as a sensor. UV-VIS and photoelectron spectroscopy were the main research tools used in this study.

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Investigations of reconstruction of passivation layer on stainless steel surface using AFM-based techniques

Abstract

Continuous development of stainless steel technology forced by the increase in the growing demands on the operating parameters of various stainless steel alloys, is the motivation for implementation of research for understanding the complexity of electrochemical processes ongoing on the surface of a material during various technological processes and during exploitation of the finished components. In this paper, the use of atomic force microscopy (AFM) is presented as a tool for observation of reconstruction process of passivation layers on the surface of previously electropolished stainless steel. For this purpose, a technique called nanoscratching was used, in which scratches are made on the surface of a material by means of diamond scanning probe, which violates the continuity of the passivation layer. Then, the dynamics of the process of reconstruction of that layer was assessed using continuous imaging of the scratched area in AFM semicontact mode. Studies of this type can be used to evaluate the impact of various factors on the spontaneous reconstruction of the passivation layer as well as possible susceptibility of the material on the course of corrosion processes initiated as a result of mechanical defects arising during operation of the material. By using the AFM, it was possible to observe changes in the depth of scratches with a subnanometer resolution. Obtained results proved that the presented AFM application allowed observation of the dynamics of passivation layer reconstruction process in a quantitative fashion, therefore it seems to be a very useful tool in the investigation of the impact of various conditions on this phenomenon. The results showed that changes in surface modification were occurring in a continuous manner. Changing dynamics of said process was presented. It should be underlined that no such experiments have been reported so far.

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FeS2 quantum dots sensitized nanostructured TiO2 solar cell: photoelectrochemical and photoinduced absorption spectroscopy studies

Abstract

Thin films of nanostructured TiO2 have been modified with FeS2 (pyrite) nano-particles by a low temperature chemical reaction of iron pentacarbonyl with sulfur in xylene. Quantum size effects are manifested by the observation of a blue shift in both absorption and photocurrent action spectra. PIA (Photoinduced absorption spectroscopy), where the excitation is provided by a square-wave modulated (on/off) monochromatic light emitting diode, is a multipurpose tool in the study of dye-sensitized solar cells. Here, PIA is used to study quantum-dot modified TiO2 nanostructured electrodes. The PIA spectra obtained give evidence for long-lived photoinduced charge separation: electrons are injected into the metal oxide and holes are left behind in the FeS2 quantum dot. Time-resolved PIA shows that recombination between electrons and holes occurs on a millisecond timescale. The Incident-Photon-to-Current Efficiency of about 23 % was obtained at 400 nm excitation. The performances of TiO2 electrodes modified with FeS2 are relatively low, which is explained by the presence of FeS2 phases other than the photoactive pyrite phase, as follows from the XRD spectrum.

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A theoretical analysis of bi-metallic (Cu–Ag)n = 1 − 7 nano alloy clusters invoking DFT based descriptors

Abstract

Due to its large scale applications in the real field, the study of bi-metallic nano-alloy clusters is an active field of research. Though a number of experimental reports are available in this domain, a deep theoretical insight is yet to receive. Among several nano-clusters, the compound formed between Cu–Ag has gained a large importance due to its remarkable optical property. Density Functional Theory (DFT) is one of the most popular approaches of quantum mechanics to study the electronic properties of materials. Conceptually, DFT based descriptors have turned to be indispensable tools for analyzing and correlating the experimental properties of compounds. In this venture, we have analyzed the experimental properties of the (Cu–Ag)n = 1 − 7 nano-alloy clusters invoking DFT methodology. A nice correlation has been found between optical properties of the aforesaid nano-clusters with our evaluated theoretical descriptors. The similar agreement between experimental bond length and computed data is also reflected in this analysis. Beside these, the effect of even-odd alternation behavior of nano compounds on the HOMO-LUMO gap is very important in our computation. It is probably the first attempt to establish such type of correlation.

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Investigation of Cu(In, Ga)Se2 solar cell performance with non-cadmium buffer layer using TCAD-SILVACO

Abstract

The purpose of this work is to achieve the best efficiency of Cu(In, Ga)Se2 solar cells by replacing the CdS buffer layer with other nontoxic materials. The simulation tool used in this study is Silvaco-Atlas package based on digital resolution 2D transport equations governing the conduction mechanisms in semiconductor devices. The J-V characteristics are simulated under AM1.5G illumination. Firstly, we will report the modeling and simulation results of CdS/CIGS solar cell, in comparison with the previously reported experimental results [1]. Secondly, the photovoltaic parameters will be calculated with CdS buffer layer and without any buffer layer to understand its impact on the output parameters of solar cells. The simulation is carried out with the use of electrical and optical parameters chosen judiciously for different buffers (CdS, ZnOS and ZnSe). In comparison to simulated CdS/CIGS, the best photovoltaic parameters have been obtained with ZnOS buffer layer. The structure has almost the same open circuit voltage Voc and fill factor FF, and higher short circuit current density Jsc, which results in slightly higher conversion efficiencies.

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Effect of pulsed magnetron sputtering process for the deposition of thin layers of nickel and nickel oxide

Abstract

Magnetron sputtered nickel and nickel oxide films have been studied for various applications. We may find, among others, these films in electrochromic display devices, in resistive type gas sensors, as metal electrodes in electronic devices, in solar thermal absorbers. Pure nickel films deposited using PVD technique possess good corrosion and wear resistant properties. Magnetron sputtering has several advantages in film deposition (in comparison to other methods) such as relatively low heating temperature of the deposited substrate during sputtering process, high energy of sputtered atoms (about 10 eV) at the substrate, which influences positively the films adhesion. From application point of view, the most valuable feature of these films is the possibility of scaling target dimensions, which makes feasible the deposition on a several square meter surfaces. The improvement of magnetron sputtering devices design may influence positively the optimization of the deposition technology and its efficiency. The thin nickel and nickel oxide films were prepared by pulsed magnetron sputtering using original type WMK magnetron device. Ni (99.9 %) has been used as a sputtering target of 100 mm in diameter and different thicknesses (3 mm, 5 mm, and 6 mm). The distance between the substrate and target was the same in all experiments and equal to 120 mm. Argon and oxygen gases were introduced during the reactive process through needle gas valves at a total pressure of 0.4 Pa. The sputtering power, sputtering pressure and oxygen partial pressure have been used as technological knobs for deposition processes. The helpful tool for controlling the pulsed magnetron sputtering process was the original parameter of supply (so called circulating power). Results from our experiments showed that the deposition of Ni films is possible even from targets of 6 mm thickness. Deposition rate increased proportionally with the sputtering power. The aim of this work is to use the acquired expertise to develop an efficient technology of thin nickel oxide layers for electrochromic systems.

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