دانلود کتاب،مقاله،جزوه و نرم افزار مهندسی مواد
کلیه منابع مورد نیاز دانشجویان و مهندسین مواد (متالورژی ، سرامیک ، جوش ، خوردگی ، نانو و بایومواد)دانلود کتاب،مقاله،جزوه و نرم افزار مهندسی مواد
کلیه منابع مورد نیاز دانشجویان و مهندسین مواد (متالورژی ، سرامیک ، جوش ، خوردگی ، نانو و بایومواد)شناسایی ساختار و انتقال بار لایه های گرافن
Structural and charge transport characteristics of graphene layers
obtained from CVD thin film and bulk graphite materials
شناسایی ساختار و انتقال بار لایه های گرافن حاصل از لایه نازک CVD و مواد گرافیتی
ABSTRACT
We report an experimental comparative study of graphene layers produced by micromechanical cleavage of bulk graphite materials of different origins and graphite films obtained by plasma enhanced chemical vapor deposition (PECVD). Structural characteristics of these materials were evaluated using Raman spectroscopy and electron microscopy. Field effect transistors (FETs) based on the PECVD graphene were produced using electron beam lithography. Conductivity, carrier mobility and other characteristics of the PECVD graphene obtained from Raman and FET tests were similar to the properties of graphene flakes obtained from bulk graphite materials. Taking into account the scalability of the CVD fabrication, these results confirm the possible industrial use of graphene films obtained by this method.
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آنالیز اشعه ایکس Ti-Nb-Ta-Zr در آلیاژهای تیتانیوم
In situ X-ray analysis of mechanism of nonlinear
super elastic behavior of Ti–Nb–Ta–Zr system beta-type titanium alloy
for biomedical applications
آنالیز اشعه X در جای مکانیسم رفتار سوپرالاستیک غیر‌خطی سیستم Ti-Nb-Ta-Zr
در آلیاژهای تیتانیوم نوع بتا برای کاربردهای زیست‌پزشکی
ABSTRACT
Ti–XNb–10Ta–5Zr (mass %) alloys based on nominal compositions of Ti–35Nb–10Ta–5Zr, Ti–30Nb–10Ta–5Zr, and Ti–25Nb–10Ta–5Zr were fabricated through powder metallurgy and forging and swaging processes for biomedical applications. The tensile deformation mechanisms of the Ti–25Nb–10Ta–5Zr, Ti–30Nb–10Ta–5Zr, and Ti–35Nb–10Ta–5Zr alloys were investigated in situ by X-ray diffraction analysis under several loading conditions.
Under the loading conditions, the X-ray diffraction peaks of all the specimens shifted to higher angles than those obtained under the unloading conditions. For the Ti–30Nb–10Ta–5Zr alloy, the elastic deformation is considered to progress continuously in a different crystal direction although after the elastic strain reaches elastic limit in the crystal direction where the elastic limit is the smallest, slip deformation occurs in that crystal direction. The elastic modulus of this alloy appears to decrease in terms of strain over the proportional limit. Thus, the elastic deformation behavior of the Ti–30Nb–10Ta–5Zr alloy does not obey Hooke's law.
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افزودن کاربید بور پراکنده شده به مواد ترموالکتریک برپایه تلوراید بیسموت
Spark Plasma Sintered bismuth telluride-based thermoelectric
materials incorporating dispersed boron carbide
افزودن کاربید بور پراکنده شده به مواد ترموالکتریک برپایه تلوراید بیسموت
سینتر شده به روش پلاسمای جرقه ای
ABSTRACT
The mechanical properties of bismuth telluride based thermoelectric materials have received much less attention in the literature than their thermoelectric properties. Polycrystalline p-type Bi0.5Sb1.5Te3 materials were produced from powder using spark plasma sintering (SPS). The effects of nano-B4C addition on the thermoelectric performance, Vickers hardness and fracture toughness were measured. Addition of 0.2 vol% B4C was found to have little effect on zT but increased hardness by approximately 27% when compared to polycrystalline material without B4C. The KIC fracture toughness of these compositions was measured as 0.80 MPa m1/2 by Single-Edge V-Notched Beam (SEVNB). The machinability of polycrystalline materials produced by SPS was significantly better than commercially available directionally solidified materials because the latter is limited by cleavage along the crystallographic plane parallel to the direction of solidification.
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چکیده
خواص مکانیکی مواد ترموالکتریک برپایه تلوراید بیسموت، خیلی کمتر از خواص ترموالکتریکی آنها مورد توجه قرار گرفته است. ماده Bi0.5Sb1.5Te3 نوع p پلی کریستال، به روش سینتر پلاسمای جرقه ای (SPS) از پودر تولید شد. اثر افزودن نانوذرات B4C روی عملکرد ترموالکتریکی، سختی ویکرز و چقرمگی شکست اندازه گیری گردید. مشخص شد که افزودن 2/0% B4C اثر اندکی روی zT دارد، اما در مقایسه با ماده پلی کریستالی بدون B4C، تقریباً 27% افزایش سختی دارد. چقرمگی شکست KIC این ترکیبات به وسیله "آزمایش تیر با شیار V شکل لبه ای " (SEVNB) به صورت Mpa m1/2 80/0 اندازه گیری شد. قابلیت ماشین کاری مواد پلی کریستالی تولید شده به روش SPS، به طور قابل توجهی بهتر از مواد با انجماد جهت دار رایج تجاری است، چرا که ماشین کاری مواد با انجماد جهت دار، با کلیواژ در طول صفحه کریستالوگرافی موازی با جهت انجماد، محدود می گردد.
خواص سایش پوشش CrC–37WC–18M رسوب داده شده
Wear properties of CrC–37WC–18M coatings deposited by
HVOF and HVAF spraying processes
خواص سایش پوشش CrC–37WC–18M رسوب داده شده
توسط فرایندهای پاشش HVOF و HVAF
ABSTRACT
CrC–37WC–18M cermet coatings were deposited using new feedstock powders which seem to combine the properties of WC–CoCr and CrC–NiCr coatings. A conventional particle size CrC–37WC–18M powder was used as feedstock for the HVOF (high velocity oxygen fuel) thermal spraying process and a fine particle distribution was used as feedstock for the HVAF (high velocity air fuel) thermal spraying process. In order to characterize the morphology of the feedstock powders and deposited coatings SEM and X-ray diffraction were used. The microhardness of the coatings was also studied. The wear behavior of the coatings was evaluated by pin-on-disk and rubber wheel abrasion tests. The HVAF coating showed equal or even better wear resistance as compared to corresponding HVOF coatings
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کامپوزیتهای زمینه سرامیکی بافته شده
Multiscale model of woven ceramic matrix composites
considering manufacturing induced damage
کامپوزیتهای زمینه سرامیکی بافته شده با توجه به آسیبهای ایجاد شدهی تولید
ABSTRACT
Multiscale models play an important role in capturing the nonlinear response of woven carbon fiber reinforced ceramic matrix composites. In plain weave carbon fiber/silicon carbide (C/SiC) composites, for example, when microcracks form in the as-produced parts due to the mismatch in thermal properties between constituents, a multiscale thermoelastic framework can be used to capture the initial damage state of these composites. In this paper, a micromechanics-based multiscale model coupled with a thermoelastic progressive damage model is developed to simulate the elastic and damage behavior of a plain weave C/SiC composite system under thermal and mechanical loading conditions. The multiscale model is able to accurately predict composite behavior and serves as a valuable tool in investigating the physics of damage initiation and progression, in addition to the evolution of effective composite elastic moduli caused by temperature change and damage. The matrix damage initiation and progression is investigated at various length scales and the effects are demonstrated on the global composite behavior.
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فرایند زینترینگ انفعالی و خواص ترموالکتریک کاربیدهای غنی از بور
Reactive sintering process and thermoelectric properties of
boron rich boron carbides
فرایند زینترینگ انفعالی و خواص ترموالکتریک کاربیدهای غنی از بور
ABSTRACT
Dense boron rich boron carbides were reactive sintered by hot pressing at 2050 °C using elementary boronsingle bondcarbon compositions with carbon contents of 9.1, 11.1, 13.3 and 18.8 at.%. The following material characteristics are presented: relative density, SEM images, EDX, X-ray diffraction and corresponding lattice parameters, Seebeck coefficient, electrical conductivity and thermoelectric power factor. Significant grain growth has been obtained with increasing boron content. A deeper understanding of the boron and carbon reaction and the overall sintering process is gained by thermal and chemical analysis in combination with X-ray diffraction. Additionally a thermal experiment with boron and carbon layers illustrates the solid state diffusion behaviour. The found results of boron carbide properties of this paper correspond with results by other authors. The aim is to correlate technological aspects of sintering procedure with material properties. This should help to improve the thermoelectric efficiency of boron carbide based materials.
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مواد الکتروکرومیک
Electrochromic Materials
مواد الکتروکرومیک
ABSTRACT
A set of materials exhibit electrochromic activity when constituted as a thin film structure whose coloration can be changed reversibly by electrical charging and discharging . there are two types of such electrochromic materials . The first type is uncolored when unpowered and changes to a colored state when a voltage is applied and returns to its uncolored state when the voltage is removed . In the second type an opposite voltage is required to be applied for bleaching ( or decoloration ) .The degree of coloration is a direct visual indication of the state of charing present in the material .
مواد ابر رسانا
Superconducting Materials
مواد ابر رسانا
ABSTRACT
The phenomenon of superconductivity came to be known in 1911 by observing that a capillary column of mercury immersed in a liquid helium bath woud show an abrupt reduction in resistance and at 4.2 K it became impossible to measure the low resistance exhibited by the column with the then available measurement techniques . It was concluded that below a critical temperature (Tc) the mercury had passed into a new state . Subsequent studies on superconduction were pursued with tin and lead as candidate materials and it was discovered that a critical current density (Jc) is carried by a superconduction sample before it returns to its normal ( metallic ) state .
مقدمه الزامات مهندسی برای مواد کامپوزیتی صنعت هوافضا
Introduction: engineering
requirements for aerospace
composite materials
مقدمه الزامات مهندسی برای مواد کامپوزیتی صنعت هوافضا
ABSTRACT
Composite materials have gained popularity (despite their generally high cost) in high performance products that need to be lightweight, yet strong enough to take high loads such as aerospace structures (tails, wings and fuselages), boat construction, bicycle frames and racing car bodies. Other uses include storage tanks and fishing rods. Natural composites (wood and fabrics) have found applications in aircraft from the first flight of the Wright Brothers’ Flyer 1, in North Carolina on December 17, 1903, to the plethora of uses now enjoyed by man-made (engineered) composite materials on both military and civil aircraft, in addition to more exotic applications on unmanned aerial vehicles (UAVs), space launchers and satellites. Their adoption as a major contribution to aircraft structures followed on from the discovery of carbon fibre at the Royal Aircraft Establishment at Farnborough, UK, in 1964.
وضعیت صنعت در کنترل آخال ها در طی ریخته گری شمش فولادی
State of the Art in the Control of Inclusions during Steel
Ingot Casting
وضعیت صنعت در کنترل آخال ها در طی ریخته گری شمش فولادی
ABSTRACT
This article extensively reviews published research on inclusions in ingot steel and defects on ingot products, methods to measure and detect inclusions in steel, the causes of exogenous inclusions, and the transport and entrapment of inclusions during fluid flow, segregation, and solidification of steel cast in ingot molds. Exogenous inclusions in ingots originate mainly from reoxidation of the molten steel, slag entrapment, and lining erosion, which are detailed in this article. The measures to prevent the formation of exogenous inclusions and improve their removal are provided, which are very useful for the clean steel production of ingot industries.