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 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.

 

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 ZNO آراسته به کاهش اکسید گرافن

Hydrothermal synthesis of ZnO decorated reduced

graphene oxide: Understanding the mechanism of photocatalysis

سنتز هیدروترمال ZNO آراسته به کاهش اکسید گرافن : درک مکانیزم کاتالیز نوری

ABSTRACT

ZnO nanomaterials are grown in-situ on graphene oxide (GO) materials by a facile hydrothermal method at a temperature of 100
C. These ZnO–graphene composite materials display a strong and broad absorption in the visible region besides an intense UV absorption peak. The enhanced fluorescent quenching observed for the graphene hybrids compared to ZnO, indicates the photoinduced electron transfer between ZnO and graphene layers, which in-turn reduces the recombination of charge carriers. In order to understand the mechanism of improved photocatalytic properties, reagents such as a radical scavenger t-BuOH and a hole scavenger EDTA-2Na were employed. The addition of t-BuOH did not show any appreciable changes in the photo-degradation properties of the ZnO–graphene hybrids. However, the addition of EDTA-2Na significantly reduced the photocatalytic activities of the ZnO–graphene hybrids indicated that photo-generated holes are the main reactive oxidative species responsible for the photocatalytic reaction. It has been concluded that the excellent absorption range, efficient charge transportation and separation and high surface area make the ZnO–graphene hybrids a better photocatalyst under UV and visible light.

 

سنتز هیدروترمال و شناسایی لایه های ZnO با نانوساختارهای مختلف

Hydrothermal synthesis and characterization of

ZnO films with different nanostructures

سنتز هیدروترمال و شناسایی لایه های ZnO با نانوساختارهای مختلف

ABSTRACT

ZnO nanomaterials were grown on the F-doped SnO2 glass substrate by a two-step hydrothermal method [14]. Firstly, ZnO buffer layer was modified on FTO substrates by spin-coating. Secondly, hydrothermal method was employed to synthesize ZnO materials. ZnO buffer layer was obtained by the following procedure. Zinc acetate was dissolved in the mixed solution of ethanolamine and 2- methoxyethanol with a concentration of 0.75 M. The mixture was then agitated at 60 ◦C for 30 min to yield a homogeneous and stable colloid solution. The procedure was the same as Ref. [27]. After coated with the above colloid solution by spin-coating, FTO substrates were annealed at 300 ◦C to get ZnO buffer layer.