پلاستیک ها، الاستومر ها و کامپوزیت ها به منظور کنترل خوردگی

 Using Plastics, Elastomers, and Composites for Corrosion Control

استفاده از پلاستیک ها، الاستومر ها و کامپوزیت ها به منظور کنترل خوردگی 

ABSTRACT

This chapter provides a broad overview of the application of polymers used for corrosion control in the chemical proces- sing industry. The generalizations offered about polymer performance might suggest possible approaches, but they should not be considered as recommendations owing to the complexity of equipment design and the many variables of chemical processing. Consultations with experts, analyses of case histories, and testing are essential to the success of these materials.

 

بهبود یک فولاد میکروآلیاژی HSLA با وانادیم و تیتانیم

Effect of vanadium and titanium modification on the microstructure and

mechanical properties of a microalloyed HSLA steel

اثر بهبود یک‌نوع فولاد میکروآلیاژی HSLA با وانادیم و تیتانیم بر ریزساختار و خواص مکانیکی آن

ABSTRACT

Microalloyed high-strength low-alloy (HSLA) steels are essentially low carbon low-alloy steels that contain small additions (0.001–0.1wt.%) of alloying elements such as Nb, V, or Ti. These steels exhibit an outstanding combination of high strength, resistance to brittle fracture and good weldability, particularly if the carbon content is kept below ∼0.1wt.% . Several categories of HSLA steels have been developed catering to the needs of specific applications, such as the construction of large ships, oil and gas transmission lines, and offshore oil drilling platforms.

 

آنالیز میکروسکوپ تونلی روبشی STM و میکروسکوپ نیروی روبشی SFM

scanning tunneling microscope (STM) 

Scanning Force Microscopy (SFM)

آنالیز میکروسکوپ تونلی روبشی STM و میکروسکوپ نیروی روبشی  SFM

ABSTRACT

Scanning tunneling microscopy (STM) and its offspring, scanning force microscopy (SFM) , are real-space imaging techniques that can produce topographic images of a surface with atomic resolution in all three dimensions. Almost any solid surface can be studied with STM or SFM : insulators, semiconductors, and conductors, transparent as well as opaque materials. Surfaces can be studied in air, in liquid, or in ultrahigh vacuum, with fields of view from atoms to greater than 250*250um. With this flexibility in both the operating environment and types of samples that can be studied, STM/SFM is a powerful imaging system.

 

سلول های خورشیدی از تک کریستال های Si تا مواد متخلخل

A review on solar cells from Si-single crystals

to porous materials and quantum dots

مروری بر سلول های خورشیدی از تک کریستال های Si تا نقاط کوانتومی و مواد متخلخل

ABSTRACT

Solar energy conversion to electricity through photovoltaics or to useful fuel through photoelectrochemical cells was still a main task for research groups and developments sectors. In this article we are reviewing the development of the different generations of solar cells. The fabrication of solar cells has passed through a large number of improvement steps considering the technological and economic aspects. The first generation solar cells were based on Si wafers, mainly single crystals. Permanent researches on cost reduction and improved solar cell efficiency have led to the marketing of solar modules having 12–16% solar conversion efficiency. Application of polycrystalline Si and other forms of Si have reduced the cost but on the expense of the solar conversion efficiency. The second generation solar cells were based on thin film technology. Thin films of amorphous Si, CIS (copper–indium–selenide) and t-Si were employed. Solar conversion efficiencies of about 12% have been achieved with a remarkable cost reduction. 

 

زینترینگ سرامیک های Nd:YAG شفاف تحت اتمسفر اکسیژن

Sintering of transparent Nd:YAG ceramics in oxygen atmosphere 

زینترینگ سرامیک های Nd:YAG شفاف تحت اتمسفر اکسیژن

ABSTRACT

Yttrium aluminum garnet (YAG) transparent ceramics were fabricated by sintering at oxygen atmosphere. Tetraethyl orthosilicate (TEOS) was added as the sintering additive to control the grain growth and densification. Pores were eliminated clearly at temperature lower than 1700 °C, while grain size was around 3 μm. The in-line transmittance was 80% at 1064 nm when samples were sintered at 1710 °C. The effect of TEOS was studied in oxygen atmosphere sintering for Nd:YAG transparent ceramics. At higher temperature like 1710 °C, the grain growth mechanism was solute drag, while at 1630 and 1550 °C the grain growth was controlled by liquid phase sintering mechanism. And 0.5 wt.% TEOS was the best adding content for Nd:YAG sintered in oxygen atmosphere.

 

اثر ریزساختار بر رفتار سایشی گلوله‌های آسیاب از جنس چدن پرکروم

Effect of microstructure on wear behavior of

high Chromium cast iron milling balls

اثر ریزساختار بر رفتار سایشی گلوله‌های آسیاب از جنس چدن پرکروم

ABSTRACT

In milling and grinding of minerals, balls which can be made of high chromium white cast iron are loaded into the milling container. Under the operating conditions of milling, the balls are subjected to impact, rolling, fatigue and corrosion wears which cause fracture and deforming the balls [1,2]. Since the wear conditions are unchangeable and inevitable, control of the ball dimensions, ball material, alloying and heat treatment must meet the required conditions to provide good wear and erosion resistance [3,4]. Generally, the balls are chosen from high chromium cast iron to provide hard carbide within the martensitic matrix with a little retained austenite to result in the best wear resistance for the operating conditions of the balls [5].

 

اثر توزیع ZrB2 و SiC روی فرسایش کامپوزیت های کربن/کربن اصلاح شده

Effect of ZrB2 and SiC distributions on the ablation of

modified carbon/carbon composites

اثر توزیع ZrB2 و SiC روی فرسایش کامپوزیت های کربن/کربن اصلاح شده

ABSTRACT

To understand the effect of introduced phases’ distribution on the ablation of carbon/carbon (C/C) composites, C/C–ZrB2–SiC composites containing isolated (SZ-1) and coupled (SZ-2) ZrB2–SiC particles were prepared via controllable precursor infiltrations and pyrolysis, respectively. Ablation under oxyacetylene torch at both Z and XY directions showed that SZ-1 had better ablation resistance than SZ-2, while the surface temperature rose up to about 2400 °C. The ablated surface morphologies showed that a relative integrate layer of ablation products was formed on SZ-1, whereas the layer on SZ-2 was defective. It was believed that the dissimilar distributions of ZrB2–SiC particles in composites resulted in distinct structures of ablation products on the surfaces and consequently their different ablation behavior.

افزودن آهن بر سینترینگ فاز مایع کامپوزیت تنگستن- برنز

The effects of Fe additions on the liquid phase sintering of

W-bronze composites

اثرات افزودن آهن بر سینترینگ فاز مایع کامپوزیت تنگستن- برنز

ABSTRACT

In this investigation, experiments were conducted to evaluate the effects of Fe additives in the range of 1–5 wt.% on the densification of different compositions of W–pre-alloy bronze compacts sintered isothermally at temperatures ranging from 900 °C to 965 °C for 2.30 h. The results showed that substantial improvement in hardness by a factor of two folds and density by 10% was achieved for the W–pre-alloy bronze sintered compacts by the addition of 2–3 wt.% Fe as an activator.

 

تاثیر انجماد بر تحول ریزساختاری فلز جوش پایه نیکل

Influence of solidification on the microstructural evolution

of nickel base weld metal

تاثیر انجماد بر تحول ریزساختاری فلز جوش پایه نیکل 

ABSTRACT

The effect of segregation resulting from solidification on the microstructural evolution of nickel base alloys was investigated. Two different groups of alloys were produced to simulate either the Hastelloy C type or the Inconel 625/718 type of alloys. Gravitational thermal analysis welding was performed on these experimental alloys and the extent of microsegregation in the weld metal was determined. Using composition profiles obtained from solidified microstructures, predictions of the phase stability of these microstructures were made based on metal d-level (Md) calculations. The maximum Md values obtained in these microstructures were compared with those critical to the formation of topologically close-packed (TCP) phases such as sigma, P, and Laves. These profiles showed an increase in the Md level in the interdendritic regions which was correlated to the formation of TCP phases.

 

جوشکاری اصطکاکی اغتشاشی صفحات AA 2219 نورد شده

Interface behaviours and mechanical properties of filling friction stir weld joining AA 2219 

رفتارهای فصل مشترک وخواص مکانیکی جوشکاری اصطکاکی اغتشاشی

پرکردن اتصال AA2219

ABSTRACT

Being brittle and having low thermal conductivity, refractories suffer damage and sometimes fail in service as a result of thermal shock. While the approach of those making fine-grained technical ceramics is to make their products sufficiently strong to withstand thermal stresses the refractory technologist is more cunning. He uses, often little known, devices to provide resistance to thermal shock that minimise but do not eliminate damage to the component. In this paper the basic equations of thermal conduction and elasticity are presented and followed by some immediate results that should guide the designer of components subject to severe thermal environments. The influence of size and shape of the refractory components is then discussed along with ways in which refractory producers can engineer the thermal and mechanical properties. In particular, the methods used to tailor fracture behavior to optimize the thermal shock resistance are treated in some detail.