مشخصه یابی ریزساختارها و انحراف جهت گیری رشد دندریت فاز Al2Cu

Characterization of microstructures and growth orientation deviating

of Al2Cu phase dendrite at different directional solidification rates

مشخصه یابی ریزساختارها و انحراف جهت گیری رشد دندریت فاز Al2Cu

در نرخ های انجماد جهت دار مختلف 

ABSTRACT

At different directional solidification rates (10, 20 and 100 mm/s), microstructures and growth orientation variations of Al2Cu dendrite in Al-40%Cu alloy were characterized. When solidification rates were ranged from 10 to 100 mm/s, three-dimensional microstructure of Al2Cu dendrite changed from faceted L-shaped patterns to non-faceted complex dendrite morphology in transverse section. By the macro and micro orientation analysis characterize methods, [001] growth direction of Al2Cu dendrites with different morphologies was determined. The deviation angle between [001] direction and the heat flow direction was increased with solidified rate increasing. The experimental results showed that the regular solidified microstructure and growth orientation along the heat flow direction could be well controlled under lower directional solidification rate.

 

نقش آستنیت در چقرمگی جوش فولاد زنگ‌نزن سوپردوفازی

Role of Austenite in Weld Toughness of Super Duplex Stainless Steel

نقش آستنیت در چقرمگی جوش فولاد زنگ‌نزن سوپردوفازی

ABSTRACT

Microstructure control for welding super duplex stainless steel SAF2507 was carried out on a welded joint by GTA welding. The toughness of the bond region in the heat-affected zone (HAZ) of the advanced SAF2507 stainless steel was much lower than that of the base metal. The microstructure of the bond region for the as-welded sample was examined and the extreme grain growth of ferrite and the lowering of the amount of austenite phase were observed. In order to improve the toughness of the bond region, microstructure control was carried out using a cooling rate control process during welding. Various cooling times from 1 673 K to 1 073 K in the bond region were selected, which corresponded to the heat input from 1 kJ/mm to 6 kJ/mm. For the ferrite grain growth, the cooling time from 1 673 K to 1 473 K, that is,
t16-14 was controlled using a Gleeble simulator. The ferrite grain size increased with increasing cooling time
t16-14. For austenite phase reformation, the cooling time from 1 473 K to 1 073 K,
t14-10 was selected, since austenite phase reformation occurs within that temperature range. The amount of austenite increased with increasing
t14-10. Increasing the cooling rate caused both ferrite grain growth and an increase of the austenite phase. Improvement of the toughness was accomplished up to 60 s in the cooling time from 1 473 K to 1 073 K, however hardly any change in toughness was accomplished at the cooling time of 120 s, because the slow cooling rate caused both ferrite grain growth and an increase of the austenite phase.

 

مهندسی سطح surface engineering

surface engineering

مهندسی سطح

ABSTRACT

Surface engineering encompasses the research and technical activity aimed at the design, manufacturing, investigation and utilization of surface layers, both for technological and for end use, with properties better than those of the core [7] Surface engineering can be the key to improve performance for many products by improving their properties, such as corrosion resistance, wear resistance, fatigue limit etc Surface engineering practices play a major role in ameliorating problems and enhancing prospects for advancement in three major areas of technology, corrosion, wear and manufacturing [8] The expanding use of surface engineering generated a need for understanding or at least an awareness of the physical and chemical properties of materials (coatings/substrate), their mechanical properties and especially structure/property relationships in materials

 

آنالیز رنگی برخی رنگدانه های آبی بر پایه کبالت

Colour analysis of some cobalt-based blue pigments

آنالیز رنگی برخی رنگدانه های آبی بر پایه کبالت

ABSTRACT

The coloring efficiency in different ceramic glazes of the classical Co olivine blue pigment (Co2SiO4) was compared with those obtained with a Co-doped willemite (Co0.05Zn1.95SiO4), and with a magnesium-doped Co-Al spinel (Mg0.2Co0.8Al2O4). The fired pigments and enameled samples were characterized by XRD, UV-VIS-NIR spectroscopy, CIE-L*a*b* color-measurements, and by SEM/EDX. The Co-olivine and Co-willemite pigments dissolved to a higher extent in the molten glazes than the Co–Al spinel. The darker blue color of the Co-olivine probed to be mostly due to Co2+ ions incorporated in the glassy matrix. The Co-willemite composition (which only contained a 1.3 Co wt.%) developed the bluest color hue of all pigments in both double and single firing glazes, while the magnesium-doped Co–Al spinel was found the most appropriate blue pigment in the bulk coloration of fast-fired porcelainized stoneware.

 

مقاومت به فرسایش جرم های ریختنی دیرگداز

What Affects Erosion Resistance Of Refractory Castables?

چه چیزی مقاومت به فرسایش  جرم های ریختنی دیرگداز را تحت تأثیر قرار می دهد؟

ABSTRACT

The wear of refractory linings is often a critical problem in process units where transfer lines are subjected to high velocity gas stream containing solid particles. Knowledge regarding erosive wear of refractory linings under these conditions is restricted and, as consequence, the technological development is slow and, in general, carried out in an empirical way. The objective of the present work is to review relevant aspects related to erosive wear in industrial applications and to investigate the erosion resistance of refractory castables currently used by the aluminum industry and in petrochemical cracking units. Among the erosion variables tested are: the particle impingement angle, line pressure, particle size and hardness, the microstructure of the refractories, the binding agent content, type of aggregate, thermal history and porosity. It was found that the higher erosion was attained at 90º of impingement and decreased slightly when the angle was close to 30º. The results also pointed out that erosion was proportional to the particle velocity, its hardness and size. In addition, it was observed that the refractory erosion resistance is mostly affected by reducing the porosity.

 

خوردگی فرسایشی مواد برای کاشتنی های ارتوپدی

Fretting corrosion of materials for orthopaedic implants:

a study of a metal/polymer contact in an artificial physiological medium

خوردگی فرسایشی مواد برای کاشتنی های ارتوپدی :

مطالعه ارتباط فلز-پلیمر در یک محیط فیزیولوژیکی مصنوعی

ABSTRACT

The fretting corrosion behaviour of a 316L SS flat against a PMMA counterface has been investigated in an artificial physiological medium. A specific device has been used to visualize the in situ degradation at the contact interface. Simultaneous analysis of the coefficient of friction and free corrosion potential has shown four distinct stages during fretting experiments. An energy-oriented approach to the fretting process was conducted in tandem with measurement of wear. This method has shown a linear progression in the wear volume of the samples as a function of the interfacial energy dissipated during fretting. The presence of chlorides contributes to a considerable acceleration of the degradation of the stainless steel surface. This process was explained by a mechanism related to crevice corrosion activated by friction.

 

جذب و جمع آوری الکترون در سلول های خورشیدی

Enhanced absorbance and electron collection in inverted organic

solar cells: Optical admittance and transient photocurrent analyses

بهبود جذب و جمع آوری الکترون در سلول های خورشیدی آلی معکوس:

 ورود یا گذر نوری و آنالیز از فوتون گذار

ABSTRACT

Optical admittance analysis reveals that light absorption in inverted organic solar cells (OSCs), based on the same polymer blend layer of regio-regular poly(3-hexylthiophene):[ 6,6]-phenyl-C61-butyric acid methyl ester (PCBM), is always greater than their regular geometry OSCs fabricated using an ITO/poly(3,4-ethylene dioxythiophene):(polystyrene sulfuric acid) anode. Transient photocurrent measurements elucidate that interfacial exciton dissociation at the cathode interfaces of Al-modified ITO/ PCBM (inverted cell) and Al/PCBM (regular cell) is not equivalent. It is shown that the reverse configuration allows improving the absorbance of the cell, favoring charge collection at cathode/PCBM interface and also possessing a dawdling degradation behavior as compared to a control regular OSC in the accelerated aging test.

 

پودر نانوکریستالین ZnO سنتز شده با روش رسوب تبخیر بخار شیمیایی فراصوتی

ZnO nanocrystalline powder synthesized by

ultrasonic mist-chemical vapour deposition

پودر نانوکریستالین ZnO سنتز شده با روش رسوب تبخیر بخار شیمیایی فراصوتی

ABSTRACT

In this paper, we report on the synthesis and characterization of ZnO nanocrystalline powder grown by ultrasonic mist-chemical vapour deposition (UM-CVD) which is a promising method for large-area deposition at low temperatures taking into account of its simplicity, inexpensiveness and safety. The morphology and crystallite size of the ZnO nanopowder characterized by FESEM and TEM revealed that the powder consisted of the mixture of nanoparticles with particle size of 50–100 nm. The XRD results indicated that the synthesized ZnO powder had the pure wurtzite structure with lattice parameters a and c of 3.244 and 5.297 nm, and c/a ratio of 1.6, respectively. High temperature XRD studies of ZnO nanopowder showed that the crystallite size increased with increasing temperature with a systematic shift in peak positions towards lower 2h values due to change in lattice parameters. Temperature dependence of the lattice constants shows linear increase in their values. Diffraction patterns of ZnO nanopowder obtained from TEM were also in agreement with the XRD results. The synthesized powder exhibited the estimated direct band gap (Eg) of 3.43 eV. The optical band gap calculated from Tauc’s relation and the band gap calculated from the particle size inferred from XRD were in agreement with each other.  2007 Elsevier B.V. All rights reserved.

 

سنتز و خواص اپتیکی فیلم‌های متخلخل نانوخوشه‌ای ZnO

Synthesis and optical properties of ZnO nanocluster porous

films deposited by modified SILAR method

سنتز و خواص اپتیکی فیلم‌های متخلخل نانوخوشه‌ای ZnO نشانده شده

توسط روش SILAR اصلاح شده

ABSTRACT

possessing wide band gap and large exciton binding energy. The recent discovery of ultraviolet-luminescence at room temperature for ZnO nanomaterial has stimulated great researching interest for its potential applications in various photoelectric devices [1]. ZnO nanocluster film belongs to a new class of ZnO-based photoelectric material. The quantum confinement and the surface state or other in-gap states in ZnO nanocluster could exert strong influence on its electronic state and optical properties [2], thus making it more promising for the production of optical devices. Therefore, the investigation on the optical properties of ZnO nanocluster films is of both fundamental interest and technological importance.

 

سنتز نانو ساختار ZnO با روش رسوب حمام شیمیایی

Synthesis and characterization of ZnO nanostructures using

modified chemical bath deposition method

سنتز و ویژگی های نانو ساختار ZnO با روش رسوب حمام شیمیایی اصلاح شده

ABSTRACT

ZnO thin films were deposited using a simple, convenient and an inexpensive modified chemical bath method along with subsequent air annealing. There action mechanism for the growth of the ZnO nanostructure after theair annealing is also discussed. SEM observations reveal the formation of flower like nanostructures that are composed of leaf-like petals of thin nanosheets. The annealed ZnO nanostructures grow with the hexagonal crystalstructure. The ZnO nanostructure exhibits a blue shift in its optical absorption spectrum. The room temperature photo luminescence study reveals UV emission peaks due to near band edge emissions along withd efect related blue and green emission peaks.