سنتز کادمیوم تلوریم Fundamentals of the CdTe synthesis

Fundamentals of the CdTe synthesis

مفاهیم بنیادین سنتز CdTe

ABSTRACT

Different ways to achieve liquid, vapour, solution or even solid synthesis of CdTe are examined from a thermodynamic viewpoint. The catalytic character of the reactions of formation is stressed. The advantages of solution synthesis, mainly using the so-called Cold Travelling Heater Method (CTHM), are shown. Several kilograms of material in a run can be produced by this safe, non-expensive process, which can be easily extended to the production of homogeneous CdZnTe. Purity, homogeneity and possibility to obtain a composition corresponding to the congruent sublimation line are among the assets of this technique.

 

بهبود خصوصیات ترموالکتریکی هگزابورید‌های قلیایی خاکی

Improvement of thermoelectric properties of

alkaline-earth hexaborides

بهبود خصوصیات ترموالکتریکی هگزابورید‌های قلیایی خاکی

ABSTRACT

Thermoelectric (TE) and transport properties of alkaline-earth hexaborides were examined to investigate the possibility of improvement in their TE performance. As carrier concentration increased, electrical conductivity increased and the absolute value of the Seebeck coefficient decreased monotonically, while carrier mobility was almost unchanged. These results suggest that the electrical properties of the hexaboride depend largely on carrier concentration. Thermal conductivity of the hexaboride was higher than 10W/mK even at 1073K, which is relatively high among TE materials. Alloys of CaB6 and SrB6 were prepared in order to reduce lattice thermal conductivity. Whereas the Seebeck coefficient and electrical conductivity of the alloys were intermediate between those of CaB6 and SrB6 single phases, the thermal conductivities of the alloys were lower than those of both single phases. The highest TE performance was obtained in the vicinity of Ca0.5Sr0.5B6, indicating that alloying is effective in improving the performance.

 

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.

 

کنترل استاتیک مواد

Static Control Materials

کنترل استاتیک مواد

ABSTRACT

Static control materials are those which are useful to prevent or minimize the buildup of electrostatic charges on conducting and/or noconducting bodies . These materials are essentially of three typses : (1) Antistatic materials ; (2) static dissipative materials and (3) static conductive materials . Antistatic materials (or antistats ) act as the static control media in three different ways :First , they reduce the coefficient of friction to help minimize the frictional ( triboelectric ) Static charge generation .  Second, they increase surface resistivity to dissipate ( or bleed off ) the charges . third, they interact with the environmental factors to neutralize the generated charges .

مواد سرامیکی و پلیمری دارای مواد رسانا

Conductor-Loaded Polymeric and ceramic Material

مواد سرامیکی و پلیمری دارای مواد رسانا (دارای ذرات تقویت کننده رسانا)

ABSTRACT

Conductor-filled polymers and ceramic are specific subsets of the conductor-Loaded dielectrics . The primary reason for adding conducting particles in polymers plastics or ceramics is to enhance the electrical conductance of the medium . In general polymers and ceramics when loaded with conductors become very good conductors of electricity and are useful in a wide range of electromagnetic applications. However inclusion of a metallic constituent in a polymer matrix may affect the low density and high strength or impact resistance properties of the plastics or the ceramics .

معرفی و بررسی شکست

Introduction and fracture over view

معرفی و بررسی شکست

ABSTRACT

In this chapter ، a fundamental approach to fracture will be followed in order to develop a few central ideas about why any given material is ductile or brittle ، and how the basic lattic defects of the material cooperate to give rise to these two general classes of behavior . The analytical discussion will tend to focus on relatively brittle phenomena ، partly because any idealization of  fracture – leads one first to the consideration of brittle fracture and partly because the analysis for brittle fracture is better understood and therefor more accessible .

اثر کار مکانیکی اولیه بر ساختار و ظرفیت تغییرشکل

EFFECT OF PRIOR WORKING ON THE STRUCTURE AND DEFORMATION CAPACITY

اثر کار مکانیکی اولیه بر ساختار و ظرفیت تغییرشکل آلیاژ Mn-29.5%Al-0.5%C

ABSTRACT

Alloys based on the system Mn–AI–C relate to promising magnetically hard materials which in magnetic properties in an anisotropic state are close to barium ferrites, and in magnetic energy referred to density, they markedly surpass widely known alloys of the YuNDK type . The high magnetic properties of the system Mn–Al–C are obtained as a result of plastic deformation . Metastable r-phase, governing the ferromagnetic properties of these alloys, is stable up to 700-750°C, and therefore deformation treatment of them is not carried out at higher temperatures. It should be noted that alloys of the Mn–AI–C system have high brittleness, low ductility, and poor workability. For example, in order to obtain magnets of these alloys by extrusion at 700°C a stress of more than 800 N/mm2 is required , which leads to rapid wear of the die tool. A study was made in  of alloys containing lamellar T-phase of the martensitic type obtained after air cooling. The morphology of the r-phase may be altered by using special working methods, e.g., extrusion  or prior plastic deformation as a result of which it is possible to expect a considerable improvement in the working capacity of the alloy. It is of interest to study prior deformation of an alloy of the Mn–AI–C system in the temperature region for existence of high-temperature e-phase followed by cooling.

مواد کامپوزیت دی الکتریک با یک فاز رسانای گسسته

composite dielectric materials with a Discrete conducting phase 

مواد کامپوزیت دی الکتریک با یک فاز رسانای گسسته

 

ABSTRACT

A class of composite dielectric  materials refers to a two-phase refer ، host inclusion system in which the inclusion is a discrete- phase of conducting medium ( such as metals ، semiconductors ، or solid electrolytes ) dispersed randomly or textured as an orderly embedment in the host medium which forms a dielectric  receptacle . such composite are essentially dielectric – conductor mixtures and have Unique ( effective )  dielectric properties due to the fact that the constituent phases have extremely opposite characteristics as regards their electrical susceptance and the associated conduction phenomena .

تولید زیرکنیای تثبت شده با ایتریا به کمک تفجوشی مایکروویو

Microwave synthesis of yttria stabilized zirconia

تولید زیرکنیای تثبت شده با ایتریا به کمک تفجوشی مایکروویو

 

ABSTRACT

Yttria stabilised zirconia (YSZ) nanocrystals, with a mean size between 5 and 10 nm, were prepared by microwave flash synthesis. Flash synthesis was performed in alcoholic solutions of yttrium, zirconium chloride and sodium ethoxide (EtONa) using a microwave autoclave (RAMO system) specially designed by authors. Energydispersive X-ray analysis (EDX), X-ray powder diffraction (XRD), BET adsorption technique, photon correlation spectroscopy (PCS) transmission and scanning electron microscopy (TEM and SEM) are used to characterized these nanoparticles. Compared with conventional synthesis, nanopowders can be produced in a short period (e.g. 10 s), both high purity and stoechiometric control are obtained. Nevertheless, this mean of production is more cheaper and much faster than the ones commonly used to produce yttria stabilized zirconia (YSZ) by conventional sol–gel techniques.

مشخصه یابی ریزساختاری آلیاژ Al-8Fe-1.4V-8Si تحت ریخته گری

Microstructural characterization of squeeze-cast Al–8Fe–1.4V–8Si

مشخصه یابی ریزساختاری آلیاژ  Al-8Fe-1.4V-8Si تحت فرایند ریخته گری فشاری

 

ABSTRACT

This paper investigates the effect of vanadium on the composition and morphology of intermetallics formed during the squeeze casting of Mgmodified Al–8Fe–1.4V–8Si alloy in both monolithic form and as-reinforced with 7.58, 10.52 and 15.68 wt.% SiC particles (SiCp). Iron intermetallics of -Al7(Fe,V)3Si and -Al18Fe11Si phases were predominantly observed in the alloy and composite. SEM studies and the EDX analyses revealed that refinement of Fe-intermetallics and modification of -phases to less deleterious morphologies of -phases has been achieved by vanadium addition of 1.4%. Also, heat treatment enhances V diffusion and SiC particles act as nucleation sites for the formation of finer -intermetallics. Fractographs exhibited cracking of long -phases and partial decohesion of SiCp from the matrix.