سنتز نانو ورقه های ZnO از طریق روش الکترورسوبی

Synthesis of ZnO nanosheets via electrodeposition method and

their optical properties, growth mechanism

سنتز نانو ورقه های ZnO از طریق روش الکترورسوبی ، خواص نوری و مکانیزم رشد

ABSTRACT

ZnO nanosheets were prepared by electrochemical deposition method at 80 C on seeded Indium Tin Oxide conducting glass substrates. The seed layer was coated on ITO by spin coating and annealed at 350 C for 30 min prior to electrochemical deposition growth. X-ray diffraction patterns (XRD) and field emission scanning electron microscope (FESEM) images confirmed that the ZnO nanosheets consist of polycrystalline structures. Room temperature photoluminescence spectra (PL) of the ZnO nanosheets exhibited band-edge ultraviolet (UV) and visible emission (blue) indicating the ZnO nanosheets had excellent optical properties. The UV–Vis absorption spectrum of ZnO nanosheets was shown a strong absorption at 300 nm. The ZnO nanosheets structure demonstrated higher photocatalytic activity during degradation of aqueous methylene blue under visible-light irradiation. Moreover, the growth mechanism of the ZnO nanosheets had been discussed.

 

سنتز نانو ورقه های ZnO از طریق روش الکترورسوبی

Synthesis of ZnO nanosheets via electrodeposition method and

their optical properties, growth mechanism

سنتز نانو ورقه های ZnO از طریق روش الکترورسوبی ، خواص نوری و مکانیزم رشد

ABSTRACT

ZnO nanosheets were prepared by electrochemical deposition method at 80 C on seeded Indium Tin Oxide conducting glass substrates. The seed layer was coated on ITO by spin coating and annealed at 350 C for 30 min prior to electrochemical deposition growth. X-ray diffraction patterns (XRD) and field emission scanning electron microscope (FESEM) images confirmed that the ZnO nanosheets consist of polycrystalline structures. Room temperature photoluminescence spectra (PL) of the ZnO nanosheets exhibited band-edge ultraviolet (UV) and visible emission (blue) indicating the ZnO nanosheets had excellent optical properties. The UV–Vis absorption spectrum of ZnO nanosheets was shown a strong absorption at 300 nm. The ZnO nanosheets structure demonstrated higher photocatalytic activity during degradation of aqueous methylene blue under visible-light irradiation. Moreover, the growth mechanism of the ZnO nanosheets had been discussed.

 

جوشکاری آلیاژ Al–Cu–Mg–Mn به روش تیگ

Effect of welding parameters on the solidification microstructure

of autogenous TIG welds in an Al–Cu–Mg–Mn alloy

تاثیر پارامترهای جوشکاری بر میکروساختار انجمادی جوش های TIG

بدون ماده پر کننده در یک آلیاژ Al–Cu–Mg–Mn

ABSTRACT

The weld metal microstructures of autogenous TIG welds have been investigated for a range of welding conditions using an Al–Cu–Mg–Mn alloy. It was found that a combination of high welding speeds and low power densities provide the thermal conditions required for the nucleation and growth of equiaxed grains in the weld pool, providing heterogeneous nucleation sites are available. The most likely origin of the nucleants is from a combination of dendrite fragments and TiB2 particles that survive in the weld pool. The finest microstructure was observed in the centre of the weld and is attributed to the higher cooling rates which operate along the weld centreline. Composition profiles across the dendrite side arms were measured in the TEM and were found to follow a Scheil type segregation behaviour where there is negligible back diffusion in the solid. The measured core concentration of the dendrite side arms was found to rise with increasing welding speed and was attributed to the formation of significant undercoolings ahead of the primary dendrite tip, which enriched the liquid surrounding the dendrite side arms.

 

اثر ارتعاش مکانیکی روی ریزساختار ماده‎ی جوشکاری

Studies on the Effect of Mechanical Vibration on 

the Microstructure of the Weld Metal

تحقیقات در مورد اثر ارتعاش مکانیکی روی ریزساختار ماده‎ی جوشکاری

ABSTRACT

The solidification process in the weld metal produces solidification structure. The solidification process depends on the thermal gradient, solidification speed and the alloy content. These structures can be planar, cellular, columnar dendritic and equiaxed dendritic. The solidification process may change from planar to cellular, columnar dendritic and equiaxed dendritic across the weld metal zone as shown in fig.1. Three grains are shown to grow epitaxially from the fusion line. A short distance away from the fusion line, solidification changes to the cellular mode. Further away from the fusion line, the solidification changes to columnar dendritic mode. Near the weld centre line equiaxed dendrites nucleate and grow, blocking off the columnar dendrites. Each one of these structures would affect the hot cracking susceptibility in greater or smaller extent.

 

مشخصه یابی فولاد یاتاقان Characteristics of 100Cr6 bearing steel

Characteristics of 100Cr6 bearing steel after thixoforming process performed 

with prototype device

مشخصه یابی فولاد یاتاقان 100Cr6 بعد از فرایند thixoforming انجام شده با ابزار مدل اولیه

ABSTRACT

A device based on a high pressure die-casting(HPDC) machine was constructed, with a capacity to produce thixo-casts from steel. After inductive heating to the required semi-solid temperature range, the samples were transported in a protective argon atmosphere to a cylinder of modified HPDC and injected into a pre-heated die. Bearing steel 100Cr6 (after forging) was used as the feedstock material. The metallographic analysis of the steel showed a homogenous structure within a whole volume characterized by a grain size between 2 μm and 8 μm. Differential scanning calorimetry (DSC) analysis allowed to estimate the process temperature for thixoforming at 1 390 °C which was attributed to about 45% of a liquid phase.

 

آنالیز SEM و اشعه ایکس - SEM and X-ray Microanalysis

SEM and X-ray Microanalysis Image Formation and Interpretation

آنالیز اشعه ایکس و SEM - تفسیر و تشکیل تصویر

ABSTRACT

Scanning electron microscopy is a technique in which images form the major avenue of information to the user. A great measure of the enormous popularity of the SEM arises from the ease with which useful images can be obtained. Modern instruments incorporate many computer-controlled, automatic features that permit even a new user to rapidly obtain images that contain fine detail and features that are readily visible, even at scanning rates up to that of television (TV) display. Although such automatic “computer-aided” microscopy provides a powerful tool capable of solving many problems, there will always remain a class of problems for which the general optimized solution may not be sufficient.

متالورژی منگنز -Manganese metallurgy

Manganese metallurgy review . Part I: Leaching of ores/secondary materials and

recovery of electrolytic/chemical manganese dioxide

مروری بر متالورژی منگنز. قسمت I: فروشویی سنگ‌های‌معدنی/مواد ثانویه

و بازیافت الکترولیتی/شیمیایی دی‌اکسید منگنز

ABSTRACT

The world rapidly growing demand for manganese hasmade it increasingly important to develop processes for economical recovery of manganese from low grade manganese ores and other secondary sources. Part I of this review outlines metallurgical processes for manganese production from various resources, particularly focusing on recent developments in direct hydrometallurgical leaching and recovery processes to identify potential sources of manganese and products which can be economically produced. 

High grade manganese ores (N40%) are typically processed into suitable metallic alloy forms by pyrometallurgical processes. Low grade manganese ores (b40%) are conventionally processed by pyrometallurgical reductive roasting or melting followed by hydrometallurgical processing for production of chemical manganese dioxide (CMD), electrolytic manganese (EM) or electrolytic manganese dioxide (EMD).

اثر نرخ سرد شدن روی ساختار میکروسکوپی آلیاژ هایپر یوتکتیک Al-Ni

The influence of cooling rate on the microstructure of an Al–Ni hypereutectic alloy

اثر نرخ سرد شدن روی ساختار میکروسکوپی آلیاژ هایپر یوتکتیک Al-Ni

ABSTRACT

An Al–4 at.% Ni alloy was prepared by a melt spinning technique and characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and high resolution transmission electron microscopy. The resulting ribbon microstructure consists of intermetallic Al9Ni2 globular-like structures embedded within an aluminum matrix. Characteristic globules are nanometric (∼100 nm) and are mainly located at the grain boundaries. The resulting effect on the mechanical properties is the enhancement of the alloy hardness from 58 to 371 HV.

 

اثر ایتربیم روی خواص مکانیکی و ریزساختار آلیاژ آلومینیوم-منیزیم

Effects of Yb on the mechanical properties and microstructures of an Al–Mg alloy

اثر ایتربیم روی خواص مکانیکی و ریزساختار آلیاژ آلومینیوم-منیزیم

ABSTRACT

This paper reported a first study of the effects of Yb on the microstructures and mechanical properties of an extruded Al–Mg alloy. It has been shown that the addition of 0.3 wt.% Yb decreases the mechanical properties of the alloy since Mg- and Yb-containing constituents decrease the concentration of Mg solute atoms in Al matrix, and thus the solution strengthening effect. However, the addition of 1 wt.% Yb substantially improves the mechanical behavior of the alloy because the concentration of Yb solute atoms in Al matrix is high enough to generate solution strengthening effect. The improvement in the mechanical properties is due to the large work-hardening and high dislocation density caused by the interaction between dislocations and Yb and Mg solute atoms. The Yb and Mg atoms inhibit the dynamic recovery and recrystallization of the alloy, thus provide a uniformly distributed dislocation structure with high density.

 

تبلور مجدد و مقاومت به خوردگی آلیاژهای آلومینیوم-روی-منیزیم-مس

Effect of of Yb, Cr and Zr additions on recrystallization and corrosion resistance of Al–Zn–Mg–Cu alloys

اثر افزودن ایتربیم، کروم و زیرکونیوم روی تبلورمجدد و مقاومت به خوردگی آلیاژهای آلومینیوم-روی-منیزیم-مس

ABSTRACT

The effect of complex additions of Yb, Cr and Zr on recrystallization and corrosion resistance of Al–Zn–Mg–Cu alloy has been investigated. By complex additions of Yb, Cr and Zr to Al–Zn–Mg–Cu alloy, 20–50nm dispersoids were formed in Al matrix and identified by X-ray diffraction analysis and energy dispersive X-ray spectroscopy as Zn, Mg, Cu, Zr-containing YbCr2A120 with cubic CeCr2Al20 crystal structure. The dispersoids remarkably inhibited the recrystallization of Al matrix, and a lot of low angle grain boundary of the Al–Zn–Mg–Cu alloy by complex additions of Zr, Cr and Yb investigated by electron back scattered diffraction was retained. Complex additions of Yb, Cr and Zr to Al–Zn–Mg–Cu alloy remarkably enhanced resistance to stress corrosion cracking (KISCC) from 9.8 to 17.0MPam1/2, exfoliation corrosion from EB+ to EA and intergranular corrosion with the improved strength, fracture toughness and ductility.