جایگزین های بافت نرم Soft Tissue Replacements

Soft Tissue Replacements

جایگزین های بافت نرم 

ABSTRACT

Blood comes in contact with foreign materials for a short term in extracorporeal devices such as dialyzers , blood oxygenators , ventricular assist devices, and catheters . Long-term vascular implants include heart valve prostheses, vascular grafts , and cardiac pacemakers , among others. In this section, we will be concerned with development of biomaterials for long-term implants, specifically for heart valve prostheses, total artificial heart ( TAH ), and vascular grafts. The primary requirements for biomaterials for long-term implants are biocompatibility, nontoxicity, and durability. Furthermore, the material should be nonirritating to the tissue, resistant to platelet and thrombus deposition, nondegradable in the physiological environment, and neither absorb blood constituents nor release foreign substances into the blood stream [Shim and Lenker, 1988]. In addition, design considerations include that the implant should mimic the function of the organ that it replaces without interfering with the surrounding anatomical structures and must be of suitable size and weight. The biomaterials chosen must be easily available, inexpensive, easily machinable, and sterilizable and have a long storage life.

قابلیت تزریق شدن خمیرهای کلسیم فسفات

Injectability of calcium phosphate pastes

قابلیت تزریق شدن خمیرهای کلسیم فسفات 

ABSTRACT

A theoretical model was developed to assess ways to improve the injectability of calcium phosphate pastes. The theoretical results were then compared to experimental data obtained on calcium phosphate slips. The theoretical approach predicted that the injectability of a cement paste could be improved by an increase of the liquid-to-powder ratio, and a decrease of the particle size and the plastic limit (PL) of the powder. The theoretical results were confirmed by experimental data. Interestingly, an increase of the viscosity of the mixing liquid with small additions of xanthan had a positive effect on the paste injectability. This effect could be due to a change of the PL of the powder or to the lubricating effect of the polymer.

سنتز، شناسایی و خواص نوری نانوذرات اکسید روی

Synthesis, characterization and optical properties of zinc oxide nanoparticles

سنتز، شناسایی و خواص نوری نانوذرات اکسید روی

ABSTRACT

Zinc oxide nanoparticles were synthesized using a simple precipitation method with zinc sulfate and sodium hydroxide as starting materials. The synthesized sample was calcined at different temperatures for 2 h. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and proton-induced X-ray emission (PIXE) analysis. SEM images show various morphological changes of ZnO obtained by the above method. The average crystallite sizes of the samples were calculated from the full width at half maximum of XRD peaks by using Debye-Scherrer's formula and were found to be in the nanorange. EDS shows that the above route produced highly pure ZnO nanostructures. PIXE technique was used for trace elemental analysis of ZnO. The optical band gaps of various ZnO powders were calculated from UV-visible diffuse reflectance spectroscopic studies.

خواص ساختاری منیزیم و آلومینیوم جانشین شده در فریت لیتیم

Structural properties of magnesium and aluminium co-substituted lithium ferrite

خواص ساختاری منیزیم و آلومینیوم جانشین شده در فریت لیتیم

 

ABSTRACT

The structural properties of Mg2 + and Al3 + co-substituted Li0.5Fe2.5O4 are studied by synthesizing the spinel solid solution series MgxAl2xLi0.5(1
x)Fe2.5(1
x)O4. Polycrystalline samples of this series with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 have been prepared by double-sintering ceramic method. The structural details like: lattice constant and distribution of cations in the tetrahedral and octahedral interstitial voids have been deduced through X-ray diffraction (XRD) data analysis. The x dependence of bond length, oxygen positional parameter, site ionic radii, bulk density, porosity and shrinkages have also been determined.

راهنمای عملیات حرارتی آلیاژ های منیزیم

Heat Treater's Guide: Mg Alloys
راهنمای عملیات حرارتی آلیاژ های منیزیم

آلیاژ منیزیم ، آلومینیوم، روی

آلیاژ منیزیم، زیر کونیوم

آلیاژ منیزیم، کروم

 AZ91C ،AZ92A،EQ21A،EZ33A،HK31A،HZ32A،AZ91A،AZ91B،AZ91D،AZ91E،AZ81A

ABSTRACT

The principles which govern heat treatment of metals and alloys are applicable to both ferrous and nonferrous alloys. However, in practice there are sufficient differences to make it convenient to emphasize as separate topics the peculiarities of the alloys of each class in their response to heat treatment. For example, in nonferrous alloys, eutectoid transformations, which play such a prominent role in steels, are seldom encountered, so there is less concern with principles associated with time-temperaturetransformation diagrams and with martensite formation. On the other hand, the principles associated with chemical homogenization of cast structures are applicable to many alloys in both classes. Diffusion Process The diffusion process is involved in nearly all heat treatments for nonferrous alloys. Common treatments include:

• Annealing after cold working
• Homogenization of castings
• Precipitation hardening treatments
• Development of two-phase structures

اثر عملیات حرارتی در جوشکاری انفجاری فولاد زنگ نزن/مس

Effect of heat treatment on bonding interface in explosive welded
copper/stainless steel

اثر عملیات حرارتی روی فصل مشترک اتصال در جوشکاری انفجاری فولاد زنگ نزن/مس

ABSTRACT

In this investigation, explosive welding and heat treatment processes provided an effective method for manufacturing high-strength and high-ductility copper/ austenitic stainless steel couple. In order to improve diffusion in the interface of copper/stainless steel, first the tensile samples were provided from the welded part, then they were subjected to annealing at 300 C (below recrystallization temperature) for 8–32 h with 8 h intervals and then samples were cooled in the furnace. Optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to evaluate the possibility of diffusion in the joints. Moreover, in order to measure the hardness of the samples, microhardness test was performed. Microstructural evaluations showed that the stainless steel 304L had a wavy interface. Furthermore, the post heat treatment process resulted in great enhancement of diffusion. Microhardness measurements showed that the hardness of the sample near to the interface is greatly higher than other parts; this is due to plastic deformation and work hardening of copper and stainless steel 304L in these regions. The interface of samples with and without the post heat treatment was exhibited ductile and brittle fracture, respectively.

جوشکاری حالت جامد آلیاژ برنج Cu-Zn و فولاد

Solid-state bonding of alloy-designed Cu–Zn brass and steel

associated with phase transformation by spark plasma sintering

جوشکاری حالت جامد آلیاژ برنج Cu-Zn مخصوص و فولاد وابسته به استحاله فازی

به وسیله ی زینترینگ به کمک قوس پلاسما

ABSTRACT

Solid-state bonding between steel and a Cu alloy was studied to investigate fabrication of advanced bimetallic composites by using spark plasma sintering (SPS). In order to obtain proper bonding strength between the mating materials, Si and Al were alloyed to Cu–Zn brass to enhance interdiffusion with steel. The alloying elements diffused from the Cu alloy to steel, which transformed from the gamma to alpha phase during bonding. Owing to the phase stability of steel, the new columnar microstructure that evolved during the transformation across the joint interface showed high bonding strength between the mating alloys. The samples bonded without fracture, defects, or inhomogeneous deformation. Microstructural observations, elementary mapping, and mechanical testing demonstrated that the SPS technique and specific bonding parameters enhanced the interdiffusion between the metals. This novel method would be well suited to strengthen bonding between two dissimilar metals with different diffusion coefficients.

 

ارزیابی ساختار در اتصال نفوذی آلیاژ تیتانیوم/فولاد زنگ نزن

THE EVOLUTION CHARACTERISTICS AND NUMERICAL
ANALYSIS OF DIFFUSION BONDING INTERFACE
STRUCTURE OF TITANIUM ALLOY/Cu/STAINLESS STEEL

ارزیابی خصوصیات و آنالیز عددی ساختار در فصل مشترک اتصال نفوذی آلیاژ تیتانیوم/فولاد زنگ نزن

ABSTRACT

Carries on the investigation to the titanium alloy/Cu/stainless steel intermetallic compound of bonding interface in the meantime, to make a thermodynamic model of the interface element diffusion to have a numerical simulation of the diffusion distance and diffusion temperature, time. Using analysis methods of stretching test, microhardness test, SEM and EDS, to investigate and research the mechanical properties, the interface structure characteristic, the principal element atomic diffusion mechanism of joints thermal simulation and the vacuum diffusion bonding of Ti-6Al-4V/Cu/304, the reacting phases are produced and the distribution range . The results show that when bonding prssere is 5.0 MPa ، the joints tensile strength first increase and then decreases, with bonding temperature and time rising, When bonding temperature is 1223K, bonding time is 3.6 ks, there is a maximum tensile strength that is 162.73 MPa. However, it will is disadvantageous to performance of the joints, when bonding temperature and time extended overly. It formed multi-phase transition organizations by solid solution, intermetallic compounds in the bonding interface, such as Ti2Cu, TixCuy , Ti2Fe, TiFe2 and TiFe. Effect of TixFey on strength of the joints is slightly inferior the TixCuy compound. The fracture is mainly by the titanium alloy side region III for the source dehiscence, developing in the weak diffusion layer.

اتصال نفوذی آلیاژ مس به فولاد زنگ نزن تحت فشار ناگهانی

Impulse pressuring diffusion bonding of a copper alloy to a stainless

steel with/without a pure nickel interlayer

اتصال نفوذی آلیاژ مس به فولاد زنگ نزن تحت فشار ناگهانی همراه با یک لایه ی نیکل خالص بین آن ها و یا بدون آن

ABSTRACT

Impulse pressuring diffusion bonding of a copper alloy to a stainless steel was performed in vacuum. Using Ni interlayer of 12.5 lm, the joint produced at 825 C under 5–20 MPa for 20 min exhibited lower strength, which could result from the insufficient thermal excitation and plastic deformation. At 850 C under 5–20 MPa for 5–20 min, the strength of the joint improved with time. An optimized joint strength reached up to 217.2 MPa. Fracture occurred along the Cu–Ni reaction layer and the Ni layer and almost plastic fracture was confirmed by extensive dimples on the fracture surface. Using the interlayer of 50 lm, the fracture surface was similar. Without Ni assistance, under the same bonding condition, the joint strength was about 174.2 MPa. The lowered strength might be attributed to the appearance of some unbonded zones in the joint. Lots of brittle fracture areas appeared on the fracture surface.

مقدمه ای بر ریخته گری تحت فشار و عیوب رایج در آن

Introduction Of High Pressure Die-Casting

And Common Defects In Die-Casting

مقدمه ای بر ریخته گری تحت فشار و عیوب رایج در آن

ABSTRACT

Die casting is a manufacturing process that can produce geometrically complex metal parts through the use of reusable molds, called dies. The die casting process involves the use of a furnace, metal, die casting machine, and die. The metal, typically a non-ferrous alloy such as aluminum or zinc, is melted in the furnace and then injected into the dies in the die casting machine. There are two main types of die casting machines - hot chamber machines (used for alloys with low melting temperatures, such as zinc) and cold chamber machines (used for alloys with high melting temperatures, such as aluminum). The differences between these machines will be detailed in the sections on equipment and tooling. However, in both machines, after the molten metal is injected into the dies, it rapidly cools and solidifies into the final part, called the casting. The steps in this process are described in greater detail in the next section.