فشار انفجاری لوله‎های فولاد زنگ‎نزن تحت کشش، فشار و دمای بالا

Burst pressure of super duplex stainless steel pipes subject to

combined axial tension, internal pressure and elevated temperature

فشار انفجاری لوله‎های فولاد زنگ‎نزن ابردوتایی در معرض سه مشخصه‎ی

کشش محوری ترکیبی، فشار داخلی و دمای بالا

ABSTRACT

The burst pressure of super duplex stainless steel pipe is measured under combined internal pressure, external axial tension and elevated temperature up to 160 °C. The experimental results are compared with existing burst pressure prediction models. Existing models are found to provide reasonable estimate of the burst pressure at room temperature but significantly over estimate the burst pressure at elevated temperature. Increasing externally applied axial stress and elevated temperature reduces the pressure capacity.

 

روش فیلترینگ غیرخطی برای حذف صدای ریزنگار HR(S)TEM

A nonlinear filtering algorithm for denoising HR(S)TEM micrographs

روش فیلترینگ غیرخطی برای حذف صدای ریزنگارهای HR(S)TEM

ABSTRACT

Noise reduction of micrographs is often an essential task in high resolution (scanning) transmission electron microscopy (HR(S)TEM) either for a higher visual quality or for a more accurate quantification. Since HR(S)TEM studies are often aimed at resolving periodic atomistic columns and their non-periodic deviation at defects, it is important to develop a noise reduction algorithm that can simultaneously handle both periodic and non-periodic features properly. In this work, a nonlinear filtering algorithm is developed based on widely used techniques of low-pass filter and Wiener filter, which can efficiently reduce noise without noticeable artifacts even in HR(S)TEM micrographs with contrast of variation of background and defects. The developed nonlinear filtering algorithm is particularly suitable for quantitative electron microscopy, and is also of great interest for beam sensitive samples, in situ analyses, and atomic resolution EFTEM.

 

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.

 

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.

 

ویژگی های بصری و ساختاری نوار نازک ZNO با روش اسپاترینگ

Structural and optical characterization of ZnO thin films

for optoelectronic device applications by RF sputtering technique

ویژگی های بصری و ساختاری نوار نازک ZNO برای کاربردهای دستگاه آپتوالکترونیک

با روش اسپاترینگ RF

ABSTRACT

This work reports structural and optical study of ZnO thin films grown over p-type silicon (Si) and glass substrates by RF magnetron sputtering technique. Surface morphological and optical properties of thin film have been studied using X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray (EDX), ellipsometry and photoluminescence (PL) spectroscopy. Strong diffraction peak (002) obtained from XRD spectra of ZnO thin film indicates a preferential growth of single crystalline thin film along the c-axis oriented phase of hexagonal wurtzite structure. Surface morphological feature reveals uniform growth of undoped ZnO thin film over the substrate. Different important microstructural parameters for the film such as grain size, lattice parameters, defect density, stress and strain have been obtained. Optical properties such as transmittance, reflectance, absorption coefficient, refractive index and dielectric constant for a spectral range of 300–800 nm have been evaluated. A good optical transmittance of 83–92% has been observed for visible region, and the optical bandgap of ZnO films was found to be 3.23 eV. Energy Loss Function (ELF) and photoluminescence (PL) spectra for ZnO thin film has also been analyzed and reported.

 

سنتز هیدروترمال نانو میله ی ZnO به کمک مایکروویو

Microwave-assisted hydrothermal synthesis and

characterization of ZnO nanorods

سنتز هیدروترمال به کمک مایکروویو و ویژگی های نانو میله ی ZnO

ABSTRACT

For the purpose of this study, the nanorods of zinc oxide were synthesized by rapid microwave-assisted hydrothermal route. The microstructure and surface morphology of the sensitized nanorods were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM) and transimision electron microscope (TEM) . XRD results indicate that synthesized ZnO nanorods have wurtzite phase. The calculated value of the particle size using Debye Scherrer formula and Williamson Hall plot was found to be 20-28 nm and 35.3 nm, respectively. Low uniformity distribution of rod-like morphology (60-80 nm in diameter and average length about 250 nm) are seen in TEM micrographs. The optical parameters of the prepared ZnO nanorods have been calculated using Kubeleka-Munk. approach for the UV-vis diffuse reflectance spectrum.

 

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.

 

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.

 

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.