سنتز پودرهای نانوکامپوزیت نقره-اکسید قلع از روش هم رسوبی شیمیایی

Synthesis  of  silver  tin  oxide  nanocomposite  powders

 via  chemical coprecipitation method

سنتز پودرهای نانوکامپوزیت نقره-اکسید قلع از روش هم رسوبی شیمیایی

ABSTRACT

Introduction : Silver-metal  oxide  composite  contact  materials  have  a variety  of  applications  in  low  voltage  switches  such  as relays,  contactors  and  circuit  breakers . Until  three decades  ago,  Ag-CdO  composite  was  the  preferred material  for  these  usages  due  to  excellent  functional and  technological  properties.  However,  because  of  toxic nature  of  Cd,  especially  when  it  is  evaporated,  consider- able  efforts  have  been  made  to  replace  it  with  environ-ment-friendly  substances  such  as  Ag-SnO2. Ag-SnO2 materials,  in  addition,  have  higher  hardness,  contact resistance  and  temperature  rise  than  Ag-CdO  substances. Besides  their  arc  erosion  and  anti-welding  properties  are excellent.

 

اهمیت بیو‌فیلم‌های میکروبی در صنایع غذایی: باز‌نگری

Significance of microbial biofilms in food industry: a review

اهمیت بیو‌فیلم‌های میکروبی در صنایع غذایی: باز‌نگری

ABSTRACT

In nature and food systems, microorganisms get attracted to solid surfaces conditioned with nutrients, that are sufficient for their viability and growth. These microorganisms initially are deposited on the surfaces and later get attached, grow and actively multiply to form a colony of cells. In this regard, the formation of organic polymers are essential which helps in the proper colonization of microorganisms (Allison and Sutherland, 1987). These mass of cells further become large enough to entrap organic and inorganic debris, nutrients and other microorganisms leading to the formation of a microbial biofilm. The term biofilm refers to the biologically active matrix of cells and extracellular substances in association with a solid surface (Bakke et al., 1984). However, according to Costerton et al. (1987) a biofilm is a functional consortium of microorganisms attached to a surface and is embedded in the extracellular polymeric substances (EPS) produced by the micro- organisms.

 

نانوسرامیک های هیدروکسی آپاتیت

Hydroxyapatite nanoceramics: Basic physical

properties and biointerface modification

نانوسرامیک های هیدروکسی آپاتیت : خواص فیزکی اصلی و  اصلاحbiointerface 

ABSTRACT

A new method of surface energy modification and engineering of the hydroxyapatite (HAp) nanoceramics coatings is presented. It is performed by electron-induced surface energy modification resulting in deep and tunable variation of its wettability state. It is found from electronic traps state spectroscopy studies of the HAp ceramics implemented by various methods such as photoluminescence and surface photovoltage spectroscopy, that the HAp nanoceramics is a wide band gap p-type semiconductor with complex structure of electron/hole bulk and surface localized states. It is shown that a low-energy electron irradiation leads to surface potential modulation and provides tailoring any wettability state in a wide range of contact angles by variation of injected and trapped electron charge. The diverse wettability states engineered on the HAp surface enable selective adhesion of basic biological cells such as proteins, DNA and various bacteria.

 

نانوپودرهای هیدروکسی آپاتیت: سنتز، چگال سازی و برهم کنش سلول- مواد

Hydroxyapatite nanopowders: Synthesis, densification

and cell–materials interaction

نانوپودرهای هیدروکسی آپاتیت: سنتز، چگال سازی و برهم کنش سلول- مواد

ABSTRACT

Hydroxyapatite (HA) nanopowders with different aspect ratios were synthesized using reverse micelle template system. Nanopowders were characterized using X-ray diffraction (XRD), BET specific average surface area analysis and transmission electron microscopy (TEM). It was observed that increase in aqueous to organic ratio (A/O) and pH decreased the aspect ratio of the nanopowders. HA nanopowders with the highest aspect ratio (rod-shaped) of 7.2 ± 3.2 and the lowest aspect ratio (spherical) of 1.3 ± 0.3 were synthesized for processing dense compacts. Effect of powder morphology on densification at 1250 °C was studied with different amount of rod-shaped and spherical nanopowders. It was observed that an increase in high aspect ratio powder content in the compacts decreased sintered density under pressureless sintering condition. Also, due to excessive grain growth, no nanoscale morphology could be retained in the sintered microstructure. Mineralization study in simulated body fluid (SBF) showed formation of apatite layer on the entire surface of both compacts made with spherical and rod-shaped particles. Cytotoxicity result with OPC1 human osteoblast cells showed excellent cell attachment and cell spreading on samples after 5 days in culture.

 

ساختار و استحکام کامپوزیت کربن- تقویت شده با کربن

Strength and structure of carbon–carbon reinforced composite

ساختار و استحکام کامپوزیت کربن- تقویت شده با کربن

ABSTRACT

The atomistic simulations of carbon nanotube (CNT) – carbon reinforced composite material are reported. The studied composite samples are obtained by impregnating certain amounts of CNTs (3,3) and (6,6) into a pristine graphite matrix. The addition of CNTs is found to be of significant usefulness for the CNT–reinforced composites, since it allows to achieve extreme lightness and strength. Being impregnated into graphite matrix, CNTs are able to increase the critical component of its initially highly anisotropic Young modulus by 2–8 times. The linear thermal expansion coefficients do not exceed 10−6 to 10−5 K−1, making this material applicable for novel aviation and space vehicles. The degree of dispersion of CNTs within graphite matrix is found to drastically influence composite properties.

 

رسوب دهی لیزر پالسی لایه های نازک CdTe و اثر دمای زیرلایه

CdTe thin films grown by pulsed laser deposition

using powder as target: Effect of substrate temperature

لایه های نازک CdTe رشد کرده به روش رسوب دهی لیزر پالسی و با استفاده از

پودر به عنوان ماده هدف : اثر دمای زیرلایه

ABSTRACT

CdTe thin films were deposited by pulsed laser deposition on Corning glass slides using CdTe powder as target. Films were grown at substrate temperatures ranging from room temperature (~25 °C) to 300 °C. The structural, compositional and optical properties were analyzed as a function of substrate temperature. X-ray diffraction shows that CdTe films grown at room temperature have hexagonal phase, while for higher temperatures the films have cubic phase. Raman and EDS indicate that films grew with Te excess, which suggests that CdTe films have p-type conductivity.

 

شناسایی و سنتز نانوکریستال های CdTe شفاف فوتولومینسنت

Synthesis and characterization of

brightly photoluminescent CdTe nanocrystals

شناسایی و سنتز نانوکریستال های CdTe شفاف فوتولومینسنت

ABSTRACT

A new synthesis procedure for the preparation of spherical shaped CdTe nanocrystals (NCs) is presented, exhibiting bright luminescence with exceptionally high quantum efficiency (up to 85%). The growth of these NCs occurs in a non-coordinating solvent, octadecene, with the addition of oleic acid/tri-octylphosphine stabilizers, CdO as a precursor for the Cd monomers and additional Cd metal particles as a supplementary Cd reservoir source. The dependence of the crystalline quality and the optical properties of the CdTe NCs, on the initial Cd:Te precursors’ molar ratio, and the reaction duration were investigated. It was demonstrated that the NCs’ properties improved significantly as the initial Cd:Te molar ratios are increased. The obtained NCs’ properties were correlated with measurements of the Cd0 concentration in Cd metal particles, CdTe NCs and in Cd monomer solutions.

 

شناسایی کوآنتوم دات های CdTe در نانوذرات ژلاتینی

Synthesis and characterization of CdTe quantum dots

embedded gelatin nanoparticles 

شناسایی و سنتز کوآنتوم دات های CdTe محاط در نانوذرات ژلاتینی

ABSTRACT

Novel CdTe quantum dots (QDs) embedded gelatin nanoparticles (CdTe/gelatin nanoparticles) were synthesized via a two-step desolvation method. The morphology and size distribution of the nanoparticles were characterized by transmission electron microscope (TEM) and laser particle size analyzer. They are presented spherically and relatively uniform with a diameter of 150 nm. The luminescent properties of the nanoparticles were investigated by using fluorescence spectrophotometry and fluorescence microscopy. The fluorescence stability of nanoparticles was tested in vitro. It was found that the nanoparticles were stable in water and phosphate-buffered saline (PBS) solution (pH 7.4) for at least 15 days. A possible formation mechanism of the CdTe/gelatin nanoparticles was also proposed. The inherent stability and biocompatibility indicate that the nanoparticles are expected to be promising candidates for in vivo biological imaging studies.

 

سنتز لایه های CdTe به روش آنیل کردن در جعبه گرافیتی

Synthesis of high quality CdTe films by graphite box annealing

سنتز لایه های CdTe کیفیت بالا به روش آنیل کردن در جعبه گرافیتی

ABSTRACT

CdTe films were prepared by graphite box annealing of an evaporated CdTe precursor in different ambient conditions in the quartz annealing chamber. Large grain growth was observed for films synthesized at 710 K in argon atmosphere. The films thus produced were characterized by measuring the optical, microstructural and electrical properties.

 

سنتز لایه های نازک نانوکریستالی CdTe به روش تبخیر حرارتی در خلأ

Synthesis, electrical properties and transport mechanisms

of thermally vacuum evaporated CdTe nanocrystalline thin films

سنتز، خواص الکتریکی و مکانیزم های انتقال لایه های نازک نانوکریستالی CdTe

به روش تبخیر حرارتی در خلأ

ABSTRACT

A stoichiometry CdTe nano-structured powder was synthesized by chemical process. Thin films of different thicknesses (40, 60, and 100 nm) of CdTe were prepared by thermal evaporation method onto silicon substrates. Current–voltage (I–V) and capacitance–voltage (C–V) characteristics of CdTe nanocrystalline thin films deposited on p-Si as heterojunction have been investigated. At low voltages, current in the forward direction was found to obey the diode equation and the conduction was controlled by thermionic emission mechanism. Also, various electrical parameters were determined from the I–V and C–V analysis. The thickness dependence of the obtained capacitance–voltage (C–V) characteristics was also considered.