انتخاب پوشش Coating Selection

Coating Selection

انتخاب پوشش

ABSTRACT

An improved approach to coating selection should thus allow progressive elimination and lend itself to a computerised implementation. Furthermore, an approach which avoids the identification of one dominant wear mechanism would be desirable. A systematic framework fulfilling these goals is described below. This is intended to provide a basis for minimising the probability of tribological problems by indicating the material property limitations and characteristics needed (Matthews et. al., 1992b). 

 

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.

 

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.

 

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.

 

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.