Etching technique for revelation of plastic deformation zone in low carbon steel

Abstract

In this study, an etching technique to detect the localised plastic deformation behaviour in a low carbon steel was developed. With this technique, etching with Fry solution under ultrasonic vibration was carried out on samples plastically deformed and then heated at 550°C for a certain period of time. The plastic zone was revealed by different degrees of etching in the plastically deformed and non-deformed regions; the plastic zone was found to be only slightly etched, whereas the other region was deeply etched. From the surface offset after etching, the deformation zone was found to be observable even at low magnification, such as 10 times. As the heating duration increased, the plastic zone became clearer. The mechanism for such an etching reaction is discussed on the basis of electrochemical analysis.     

The combined effect of melt stirring and ultrasonic agitation on the degassing efficiency of AlSi9Cu3 alloy

The combined effect of high intensity ultrasound and melt stirring on the degassing of AlSi₉Cu₃ using simultaneously the novel MMM (Multi-frequency Multimode Modulated) ultrasonic technology to promote cavitation, and low frequency mechanical vibration to induce melt stirring, was studied. On a first stage single low frequency mechanical vibration experiments were carried out in water in order to visualize and characterize its individual effect on the liquid dynamics. On a second stage ultrasonic vibration combined with different mechanical vibration frequencies, melt temperatures and processing times were tested in liquid AlSi₉Cu₃ alloy and their influence on the degassing efficiency was evaluated and compared with the results of the single MMM ultrasonic degassing technique. Fixed ultrasonic parameters (frequency and electric power) were used, according to the best results obtained in former experimental works developed by the authors. For the experimental conditions used in this research, it was found that melt stirring significantly improves degassing efficiency, and such improvement depends on the metal temperature and the mechanical vibration frequency. The experimental results suggest that combining melt agitation and ultrasonic vibration it is possible to achieve almost the aluminum alloy theoretical density without increasing the processing time.     

Microstructure and mechanical properties of Cr12MoV by ultrasonic vibration-assisted laser surface melting

The effects of laser surface melting assisted by ultrasonic vibration on the microstructure and mechanical properties of Cr12MoV were investigated. Results indicated that the original coarse columnar dendrite can be converted into a fine dendritic and equiaxed. The average microhardness increase from 389HV_0.2 to 427HV_0.2 resulted from the effect of grain refinement. The friction coefficient was lower than the melted layer without ultrasonic vibration and substrate. Under the same experimental conditions, the width and depth of wear scar were decreased by 19% and 25% than that of without ultrasonic vibration, respectively. The wear mechanism from severe adhesive wear into slight abrasive wear under the action of ultrasonic vibration. Experimental results revealed that melted layer fabricated by ultrasonic vibration exhibit finer and more uniform microstructure as well as superior tribological properties.     

Synthesis of CaTiO<Subscript>3</Subscript>: Pr,Al phosphors by sol-gel method and their luminescence properties

Red long afterglow CaTiO₃: Pr, Al phosphors have been synthesized by sol-gel method using ethanol as solvent and citric acid as a chelating agent. TG-DTG curves and X-ray diffraction analysis indicate that crystalline calcium titanate has been synthesized at calcining temperature of 700 °C for 5 h. Photoluminescence and decay curves indicate that the luminescence properties of phosphors synthesized by sol-gel method are better than that prepared by solid-state reaction and the sample heated at 900 °C exhibits the optimal luminous property. Using ultrasonic dispersing technique improved the luminescence properties of phosphors.     

Fabrication of Flux Qubit with a Mechanical Degree of Freedom

We report on the fabrication and characterization of superconducting flux qubit coupled to nanomechanical resonator vibration modes. Anisotropic and isotropic etching processes parameters of plasma created by a reactive ion etching of a CF₄ gas, were optimized to suspend one arm of the qubit. One of the beams was characterized using a magnetomotive detection scheme in the transmission regime. And suspended beams with different length coupled to a superconducting flux qubits were characterized at base temperature by performing spectroscopy measurements.     

Enhancing efficiency of crystalline silicon solar cells by the mixture of downshifting CaAlSiN3:Eu2+ and Y2O3:Eu3+ phosphors

Y₂O₃:Eu³⁺ (YO) phosphors which have high quantum yield in the range 200–280 nm are mixed with downshifting CaAlSiN₃:Eu²⁺ (CASN) phosphors to improve CASN’s low quantum yield in the wavelength range below 280 nm. The luminescence downshifting ethyl vinyl acetate films with the mixture of YO and CASN phosphors are fabricated and then used to package crystalline silicon solar cells. Experimental results show that the introduction of YO phosphors not only improves the external quantum efficiency of the solar cells in the range below 280 nm but also leads to the better absorption of the light in the range 280–500 nm due to the scattering by YO phosphors. The conversion efficiency of the solar cells with the mixed phosphors can be enhanced from 19.60 to 19.98% after packaging.

     

Effective diffraction gratings via acidic etching of thermally poled glass

Relief diffraction gratings are formed via acidic chemical etching of a periodically poled soda-lime glass. The thermal poling under 1000 V DC is performed at 325 °C using a thermally stable glassy-carbon anodic electrode with periodic grooves, the depth of the grooves being of ∼650 nm. Poling-induced modification of the glass results in deepening the glass anodic surface in the regions under the ribs of the anodic electrode due to volume relaxation and in increasing chemical durability of these regions in acidic media comparatively to the virgin glass. Chemical etching of the poled glass in NH₄F:8H₂O solution allows additional to the thermal poling shaping of the glass surface via faster dissolution of unpoled/less poled glass regions. The morphology of the glass surface before and after the etching is characterized with atomic force and scanning electron microscopy. About 30 min etching provides the formation of ∼0.9 μm in height relief diffraction gratings with the diffraction efficiency close to the theoretically achievable ∼30% for multi-order diffraction. In vivo measuring of the diffraction efficiency in the course of the etching allows precise fabrication of the gratings.     

Functionalization of the (100) surface of hydrogen-terminated silicon via hydrosilation of 1-alkyne

This work presents an experimental study based on X-ray photoemission spectroscopy (XPS) of hydrosilation of 1-alkyne as a tool for the functionalization of the (100) surface of silicon. In particular, the following processes are considered: (i) hydrogen termination of silicon via HF etching and subsequent exposure to H₂ at high temperature, and (ii) grafting alkene chains to the resulting hydrogen-terminated surface via hydrosilation of 1-octyne.     

Fabrication of silica nanocoatings on ZnS-type phosphors via a sol–gel route using cetyltrimethylammonium chloride dispersant

In order to apply ZnS-type phosphors in field emission displays (FEDs), their poor ageing performance, resulting from their surface oxidation at high current densities, should be improved. In this study, the green emitting ZnS:Ag,Cl phosphors are covered with uniform and continuous SiO₂ coatings via a sol–gel route, which is expected to inhibit their surface oxidation. During the gelation process, cetyltrimethylammonium chloride (CTAC), a cationic surfactant, is added to increase the dispersibility of phosphors in suspension. Furthermore, the addition of CTAC promotes uniform distribution of charges on the whole phosphor surfaces, thus benefit the formation of continuous and uniform coatings.     

Effect of zinc metal addition on microstructural evolution of Zn0.22Cd0.78S$ phosphors studied by transmission electron microscopy

The effect of zinc powder addition on the microstructural evolution of fine Zn_0.22Cd_0.78S:Ag$, Cl phosphor particles was investigated in relation to the luminescent property of phosphors. The phosphor microstructures were analyzed by high-resolution transmission electron microscopy (HRTEM) using the ultramicrotome technique for specimen preparation. The phosphor baking process at 480 °C for 30 min in air results in significant damage to the surface structure of the phosphors due to the decomposition and oxidation of the phosphor itself. The addition of zinc metal powders into the Zn_0.22Cd_0.78S$ phosphors suppresses the oxidization and decomposition of phosphors by oxidizing zinc metal during the baking process in air. The oxidation of the zinc powders during baking provides the baking furnace with less oxidizing atmosphere for phosphor particles. The structure of phosphors, especially at the surface region, is much less degraded compared to the phosphors baked with no zinc metal addition. © 2000 Kluwer Academic Publishers     

Texturization of multicrystalline silicon by wet chemical etching for silicon solar cells

Two kinds of surface texturization of mc-Si obtained by wet chemical etching are investigated in view of implementation in the solar cell processing. The first one was the acid texturization of saw damage on the surface of multicrystalline silicon (mc-Si). The second one was macro-porous texturization prepared by double-step chemical etching after KOH saw damage layer was previously removed.Both methods of texturization are realized by chemical etching in HF-HNO₃-H₂O with different additives. Macro-porous texturization allows to obtain effective reflectivity (R_eff) in the range 9–20% from bare mc-Si. This R_eff value depends on the time of second step etching that causes porous structure modification. The internal quantum efficiency (IQE) of cells with this kind of texturization has possibility to reach better conversion efficiency than the standard mc-Si solar cells. However, low shunt resistance depends on morphology of porous layer and it is the main factor which can reduce open circuit voltage and conversion efficiency of cells.The effective reflectivity is about 17% for acid texturized mc-Si wafer. The investigation of surface morphology by scanning electron microscopy (SEM) revealed that the dislocations are appearing during chemical etching and they can reduce open circuit voltage. The density of the dislocations can be reduced by controlling depth of etching and optimisation of acid solution.     

Ultrasonic assisted fabrication of particle reinforced bonds joining aluminum metal matrix composites

This paper presents a method of producing uniform particle strengthened bonds between pieces of aluminum metal matrix composite (Al-MMCs), of strength equal to that of the substrate material. SiC particle reinforced Zn-based filler metals were fabricated by mechanical stir casting and ultrasonic treatment, and then used to join pieces of SiC_p/A356 composite with the aid of ultrasonic vibration. The filler metals made by mechanical stirring were porous and contained many particle clusters. Ultrasonic vibration was used to disperse the agglomerates and prevent further coagulation of SiC particles during joining, but the method failed to eliminate the porosity, resulting in a highly porous bond. The filler metal treated by ultrasonic vibration was free of defects and produced a non-porous bond strengthened with uniform particles between pieces of SiC_p/A356 composite. The presence of surface oxide films at the bonding interface significantly degraded the performance of SiC particle reinforced bond. Removal of this oxide film by at least 4 s of ultrasonic vibration significantly increased the bond strength, reaching a value equal to that of the substrate metal.     

Rapid synthesis of spherical-shaped green-emitting MgGa2O4:Mn phosphor via spray pyrolysis

Simple, one-step synthesis of spherical-shaped powder phosphors with aqueous precursors via a spray pyrolysis method is reported. Green-emitting MgGa₂O₄:Mn²⁺ phosphor with a controlled shape was successfully obtained by spraying under a reductive atmosphere (N₂ + H₂ carrier gas) without high-temperature post-heat treatment. In addition, the corresponding powder phosphors were well dispersed and showed a clean surface morphology compared to an existing cumbersome process using high-temperature post-annealing. The new method may help to prevent surface residual non-radiative defect sites. The result of highly luminescent and spherical morphology, non-aggregated powder phosphor by this procedure holds promise for a cost-effective and rapid synthesis process for conventional inorganic phosphors.     

Synthesis of green emitting and transparent zn2siO4:mn2+ thin film phosphors on 2D photonic crystal patterned quartz substrates

Zn2SiO4:Mn2+ thin film phosphors (TFPs) have been synthesized by RF magnetron sputtering, using a single multicomponent stoichiometric target. And 2D photonic crystal patterns were introduced on a quartz substrate to enhance the light extraction efficiency. In order to introduce 2D photonic crystal patterns on a quartz substrate, nanosphere lithography was used. Polystyrene spheres, with diameter of 330 nm, were transferred on the quartz substrate and subsequently were served as an etch mask. Quartz substrates were patterned by CF4 gas-based reactive ion etching. Zn2SiO4:Mn2+ were deposited on that 2D photonic crystal patterned quartz substrate and the effect of height of photonic crystal layers were investigated. The light extraction efficiency of Zn2SiO4:Mn2+ thin film phosphors deposited on the photonic crystal patterned quartz substrate was enhanced three times to compared with that of flat Zn2SiO4:Mn2+ thin film phosphors due to the Bragg diffraction and leaky mode caused by PCLs. Transmittance of Zn2SiO4:Mn2+ TFPs deposited on the photonic crystal patterned substrate was high enough, above 70% in the visible light region with respect to that of quartz substrate.     

Comparison of models for silicon etching in CF4 + O2 plasma

The plasma chemical etching (PCE) of Si in CF₄ + O₂ plasma is considered. The concentrations of plasma components are calculated using values extrapolated from experimental data. Resulting calculations of plasma components are used for the calculation of Si etching rates. The concentrations of the adsorbed layer and surface components, obtained from analysis of PCE of silicon, are used for the comparison of site-balance and adsorbed-layer models. It is found that adsorbed-layer model predicts higher concentration of SiO₂ molecules on the surface than site-balance model. The difference in SiO₂ concentration is important during ion-beam-assisted etching and reactive ion etching processes as the models predict different etching rates due to different sputtering yields of Si atoms and SiO₂ molecules.     

Surface modification of the (Y,Gd)BO3:Eu phosphor by dual-coating of oxide nano-particles

The surface of (Y,Gd)BO₃:Eu³⁺ phosphor, red-emitting source in the plasma display panel (PDP), was dual-coated with SiO₂ and Al₂O₃ nano-particles. The surface modification of the phosphor was performed by a modified sol-gel method using the colloidal alumina and silica as surface coating precursors. We observed the oxide nano-particles on the surface of the single coated and the dual-coated phosphors and it was found that the luminance intensity was increased in the photoluminescence (PL) by a suppression of the nonradiative recombination via surface defects. The experimental results suggest that the surface modification of phosphors with nano-particles of the oxides leads to an increase in the luminance intensity of phosphors in the PDP (plasma display panel) and the gas discharge lamps.     

An Experimental Investigation on Ultrasonic Vibration-Assisted Grinding of SiO2f/SiO2 Composites

Fiber-reinforced ceramic matrix composite (FRCMC) have been widely used in aerospace and other high-technology fields due to their excellent mechanical and physical properties. However, FRCMC is a kind of typical material with anisotropic and inhomogeneous structure; thus, it is difficult to guarantee the precision and surface quality using traditional machining. The present paper employed ultrasonic vibration-assisted grinding (UAG) to machine 2.5D woven SiO_2f/SiO₂ composites. By comparing the grinding force, surface microstructure, chip formation, surface topography and surface roughness with and without ultrasonic vibration for the machining of SiO_2f/SiO₂ composites, the feasibility of UAG on FRCMC was investigated experimentally. In addition, the effects of the process parameters (including spindle speed, feed rate, grinding depth, grain mesh size and ultrasonic power) on grinding force and surface roughness were studied through an orthogonal experiment. The research obtained can be a useful technical support for the development of UAG in the machining of FRCMC.     

Preparation and characterization of boron oxide-based red-emitting phosphors using Eu,Al and Ca additives

New red-emitting phosphors have been produced and studied by investigating the effects of various additives such as europium (Eu), aluminum (Al), and calcium (Ca) on the photoluminescence performance of boron oxide-based phosphors. When both Eu and Ca ions were added, Ca₃B₂O₆:Eu phosphors could be synthesized via a straightforward process using a liquid precursor. The photoluminescent spectra of Ca₃B₂O₆:Eu phosphors exhibited a red emission at 611 nm under 254 nm excitation, and the internal quantum efficiency reached 41.5% when the concentration of Eu ion was fixed at an optimal condition of 0.13 M.     

Cathodoluminescence characterization of rare earth doped composite materials based on porous GaP

Porous GaP layers doped with erbium or europium elements have been obtained by electrochemical etching and further impregnation processes. The thermal treatments for optical activation of rare earth (RE) ions lead to partial oxidation of porous GaP skeleton and a composite material is obtained. The presence of ErPO₄ and EuPO₄ oxide nanophases is detected by X-ray diffraction (XRD) analysis. Visible luminescence from RE ions in the composite material has been investigated by means of the cathodoluminescence (CL) technique in the scanning electron microscope. Intense red and green emission lines characteristic from Er³⁺ and Eu³⁺ ions dominate the CL spectra in the case of parallel and regular nanotubes in the samples. The role of the oxygen content and the detected phases in the luminescence results are discussed.     

超声振动辅助磨削完全烧结氧化锆陶瓷牙冠的实验研究

针对现有全锆牙在制作过程中存在二次烧结、收缩精度难以控制等问题,提出了采用超声振动辅助磨削完全烧结氧化锆陶瓷牙冠的方法。从理论分析的角度对其运动学特性进行了研究,并通过超声振动辅助磨削和普通金刚石磨削实验,对该方法的可行性进行了分析。结合牙冠的加工特点,重点研究了主轴转速对材料去除率、表面粗糙度以及最大边缘碎裂的影响规律。实验结果表明,超声振动辅助磨削不仅能提升材料的去除率,有效抑制出口边缘碎裂,同时降低了工件表面的粗糙度,是实现完全烧结氧化锆陶瓷牙冠高效低损伤加工的新方法。