Ultrasonik Sprey Piroliz Ve Hidrojen Redüksiyonu Yöntemi İle (usp-hr) Nano Yapılı Gümüş – Bakır Alaşım Partiküllerinin Üretimi

Abstract

Nanoteknoloji, yaklaşık 1-100 nm boyutundaki partiküllerin, yapıların, cihazların ve malzemelerin üretimini ve karakterizasyonunu içerir. Partikül boyutu bu değerlerler arasında elde edilen malzemenin sergilediği fiziksel ve kimyasal özellikler aynı maddeden oluşan makro boyutlu malzemelerin özelliklerinden büyük ölçüde farklıdır. Atomik boyutta malzemelerin tasarımı ve üretimine olanak sağlayan nanoteknoloji, topluma önemli faydalar sağlama potansiyeline sahiptir. Geleceğin teknolojisi olarak görülen, interdisipliner çalışmayı ön plana çıkaran ve günlük hayatımıza girmiş olan “Nanoteknoloji” alanında nano boyutlu metal partiküllerinin kullanımı ile geliştirilen ileri teknoloji malzemelerinin kullanımı son yıllarda giderek artmaktadır. 100 nanometreden daha küçük boyuta sahip partiküller genel olarak nanopartiküller olarak adlandırılırlar. Nano boyutlu metal partikülleri, ileri teknoloji malzemelerinin vazgeçilmez hammaddeleri olup, uygulama alanları çok değişik sektörlere yayılmış durumdadır. Bilişim ve haberleşme, uzay-havacılık, otomotiv, elektrik-elektronik, kimya, çevre, enerji, biyoloji, gen mühendisliği ve savunma sanayii en önemli uygulama alanlarıdır. Farklı boyut ve şekillerde nano-partiküllerin üretilmesi amacıyla yukarıdan aşağıya “Top Down” ve aşağıdan yukarıya “Buttom Up” yaklaşımları geliştirilmiştir. Yukarıdan aşağı yöntemlerinde hacimsel malzemelerin fiziksel veya mekanik teknikler kullanılarak nano yapıya indirgemesi esas alınır. Aşağıdan yukarı yöntemleri ise kimyasal prosesler sonucunda atomal ve moleküler boyuttan başlamaktadır. Aşağıdan yukarı yaklaşımında değerlendirilen USP tekniği, çok geniş aralıkta değişen kimyasal bileşime, boyuta ve morfolojiye sahip küresel partiküllerin üretilmesine imkan veren çok yönlü bir yöntemdir. USP yöntemi; başlangıç çözeltisinin hazırlanması ve çözeltinin atomize edilmesiyle başlar. Elde edilen aerosolun taşıyıcı gaz ile fırına taşınıp, fırına girişte aerosol damlacıkların kuruması ve damlacıkların büzülüp parçalanarak nano partiküller eldesiyle son bulur. Nanoteknoloji, günümüzde elektronik sektörü başta olmak üzere optik, haberleşme ve biyolojik sistemlerden yeni malzemelere son derece geniş potansiyel uygulamaları ortaya çıkarmaktadır. Bu uygulamaları şu şekilde sıralayabiliriz; ilaçlar, bilgi depolama araçları, gelişmiş seramik ve yalıtkanlar, su arıtma, katalizör, sensörler, gelişmiş polimerler, kendi kendini temizleyen boyalar ve antimikrobiyal uygulamalar. Son yıllarda özellikle günlük hayatımız ve toplu yaşama alanlarında antibakteriyel uygulamalar konusu üzerine bir çok araştırma ve inceleme yapılmaktadır. İnsan sağlığını olumsuz etkileyen bu organizmalara (Bakteri ve fungiler) karşı özellikle gümüş ve bakır metal iyonlarının etkisi tartışmasız odak noktası olmuştur. Gümüş ve bakır, özellikle bakteri ve fungilerin büyümesini xvi engellemede, onları öldürmede oldukça etkili olduğu bilinen antibakteriyel özelliğe sahip metallerin başında gelmektedirler. Çok eski yıllardan beri gemilerin alt kısmındaki yosunların oluşumunu engellemek için kullanıldığı bilinen bakır, günümüzde özellikle medikal ve tekstil sektöründe mikrobiyal gelişimi önlemek için kullanılmaktadır. Gümüş ise yine benzer özelliklerinden dolayı, tekstil, sonda, metal ve polimer gibi yüzey kaplama alanlarında antibakteriyel ajan olarak sıklıkla kullanılır. Bu çalışmada, gümüş – bakır alaşım nanopartikülleri, ultrasonik sprey piroliz tekniği ile 800 °C sıcaklıkta, farklı konsantrasyonlardaki (0,05-0,4 M) gümüş nitrat ve bakır nitrat başlangıç çözeltileri kullanılarak üretilmiştir. Sistem içinde inert atmosfer ortamı sağlamak amacıyla azot gazı, taşıyıcı gaz olarak da hidrojen gazı kullanılmıştır. Deneysel çalışmalar sonucunda, gümüş nitrat ve bakır nitrat başlangıç çözeltilerinden üretilen nano yapılı gümüş–bakır alaşım partiküllerinde, başlangıç çözeltisinin konsantrasyonun azalmasıyla, Ag-Cu alaşım nano partikül boyutunun azaldığı belirlenmiştir.

Nanotechnology has become a major scientific endeavor in the last decade. Nanoscience and technology have been growing rapidly over recent years and are already having a great impact on the development of new materials and products. Nanotechnology involves the characterization, fabrication and/ or manipulation of structures, devices or materials that have at least one dimension that is approximately 1–100 nm in length. Nanotechnology is the ability to work at the atomic, molecular and supramolecular levels in order to understand, create and use material structures, devices and systems with fundamentally new properties and functions resulting from their small structure. When particle size is reduced below this threshold, the resulting material exhibits physical and chemical properties that are significantly different from the properties of macroscale materials composed of the same substance. Nanotechnology, the design and manipulation of materials at the atomic scale, has the potential to deliver considerable benefits to society. Nanotechnology, assumed as the future technology, entered our daily lives and it puts forward the interdisciplinary study. The use of advanced technology materials which are developed by the use of nano size metal particles in the field of nanotechnology is increasing in recent years. The particles which have sizes less than 100 nanometers are generally called as nanoparticles. Nano-size metal particles are indispensable raw materials of advanced technology and their applications are dispersed in different sectors. Informatics and communication, aerospace-aeronautic, superconductors, catalyst, drug carriers, sensors, magnetic materials automotive, electric-electro,nic, chemistry, environment, energy, bisology, gene engineering and defense industry are the most important application areas of nano metal particles. With the fast growth of their new applications, nanoparticles are produced globally in massive quantities; and as a consequence, human exposure to these materials is inevitable and quickly increasing. The toxicology of nanomaterials has become a new frontier in particle toxicology; however, our current knowledge about potential adverse effects of various nanoparticles is very limited. Development of simple methods for the preparation of nanosized metal particles has attracted significant attention because of their future applications due to unusual size-dependent optical and electronic properties. Several synthesis methodologies, both “top-down” and “bottom-up” approaches, have been developed to obtain a broad variety of nano-materials in different sizes and shapes. Top-down methods are theoritacally based on sizing materials down starting from bulk (macro-scale) to nano-scale by energy–requiring physical, chemical and mechanical processes. Bottom-up methods are, however, building materials up from atoms or molecules under physical and chemical conditions. The usual production techniques of nanosized materials are various and some known examples are thermal xviii decomposition, chemical vapor condensation (CVC), laser ablation, evaporation, oxidation route, chemical reduction and sol–gel methods. Also traditionally, mechanical milling was used for particle micronization. However, intensive milling can create amorphous regions or defects on particle surfaces, which can affect humidity dependence and stability, electrostatic charging, and cohesivity. Recently, wet chemical techniques such as sol-gel and hydrothermal methods have been widely studied. However, mean particle size and particle size distribution of the resulting particles are sometimes not controlled. In addition, long reaction and posttreatment times are usually required, and impurities may be introduced during the various steps of preparation. It is important to develop a process in which particle characteristics including mean size, size distribution, morphology, and composition can be controlled easily. To be industrially relevant, the process needs to be low cost and capable of both continuous operation and high production rates. One of the candidate methods used to fulfill these requirements is spray pyrolysis. Bottom-up approach is known to be included the USP technique is a versatile and inexpensive method that allows the production of spherical particles having very wide ranges of chemical composition, size and morphology. Compared to other synthesis techniques, spray pyrolysis has many advantages such as: simple and continuous operation, controlled shape and size of the particles from nano- to micro-meters, uniform particle size distribution, high purity, and control of chemical uniformity and stoichiometry in a mixed oxide system. Spray pyrolysis has been widely used to produce fine powders because it is an inexpensive and continuous, ambient pressure process. This process is more economical than other processes that involve multiple steps or that must be carried out under vacuum. Furthermore, spray pyrolysis offers numerous possibilities for controlled synthesis of advanced ceramic powders and films because of its chemical flexibility. Spray pyrolysis is a useful tool for large-scale or small-scale production of particles with controlled particle size because the final product properties can be controlled through the choice of precursor and solution concentration or by changing aerosol decomposition parameters. Generally, in a spray pyrolysis process, reaction temperature and carrier gas composition are basic operating variables. In addition, solution properties such as precursor composition, concentration, or the addition of a co-solvent may be crucial to achieve the desired product composition and morphology. Ultrasonic spray pyrolysis may be employed to generate an aerosol from a dilute aqueous metal salt solution, resulting in the production of particles with a narrow size distribution. Ultrasonic spray pyrolysis has been most used to synthesize fine powders by aerosol decomposition. In the USP-process, a metal-containing solution is prepared and then this solution is atomized forming an aerosol. This aerosol is transported by a reduction gas into a hot reactor, where the aerosol droplets undergo drying, droplet shrinkage and it ends with formation of nanoparticles. The average size distribution of the final particles can be roughly determined from the size of the atomized droplets and its concentration in the starting solution. The size and/or morphology of the final particles produced may also be determined using the concentration and velocity of the droplet generated by the atomizers. The mechanism of droplet transformation into the particle, and degree of diameter reduction of the droplet through this process, depends on different parameters. Nanotechnology reveals an extremely wide potential applications from electronics, optical communications and biological systems to new materials. These applications are listed as; drugs, information storage devices, advanced ceramics and insulators, xix water purifier, catalysts, sensors, advanced polymers, self-cleaning paints and antimicrobial materials. Metallic nanoparticles show various applications in medicine, biotechnology, and electronics. Especially, silver nano particles are the most widely researched material and these nano particles exhibit very useful properties in catalysis and biosensing. So important applications for silver particles can be found in the catalyst and electronic industry. For example, the production of formaldexyde and ethylene oxide can benefit from the use of silver comprising nanoscale catalysts. Silver nanoparticles are important materials that have been studied extensively. They can be synthesized by several physical, chemical and biological methods. Such nanoparticles possess unique electrical, optical as well as biological properties and are thus applied in catalysis, biosensing, imaging, drug delivery, nanodevice fabrication and in medicine. Usage of silver particles are increasing significantly in consumer products such as food packaging, textiles, paints, household appliances and medical devices including wound dressings and therapeutic devices. The increased production and use of engineered nanoparticles in recent years have drawn the attention of the scientific community to its toxicity and health impacts, and to the flow of nanoparticles in the environment. So they are being projected as future generation antimicrobial agents. Since 1990s, copper nano particles have attracted much attention of researchers due to their applications in catalysis. The copper nano-powders with a small diameter size (1 – l00nm) have a large specific surface area, a small electric resistance, a large effect of quantum size and a large macroscopic effect of tunnel, which many have the different new properties compared with the common materials. The copper nano-powders can be used to produce conducting slurres (conducting gel, magnetoconducting gel etc.), which are applied in microelectronic industries (cloth, wrapping and connection etc.). The copper nano-powders play an important role in miniaturization of the microelectronic elements, and can be directly utilized in the chemical engineering as a catalyst (such as polymerization of ethylene). They can also be used as a lubricant. In these days, there are lots of research and investigation in order to ensure protective ambience against especially in virtually every area of daily life existing bacteria and fungi. Particularly the effect of silver and copper metal ions has been the undisputed focal point against these organisms having negatively effect on human health. Silver and copper ions are well known antibacterial metals capable to inhibit the growth of bacteria and fungi and also kill them. Copper,which has been known to be used to inhibit growth of algaes on the bottom of ships since the very earlist times, is currently used especially medical and textile industry to prevent microbial growth. Thanks to similar behavior, silver is widely used as antibacterial agent in many applications such as antibacterial coatings of textiles, catheders, metal and polymer surfaces. In this work, silver – copper alloy nanoparticles were produced by ultrasonic spray pyrolysis of a liquid solution of silver nitrate and copper nitrate with different concentrations (between 0,05-0,4 M) at 800 °C. To provide an inert atmosphere within the system nitrogen gas is used,also as carrier gas hydrogen gas is used. Experimental results showed that, both hydrogen and nitrogen gases are suitable as carrier/reduction gas for production of silver nanoparticles from silver nitrate and copper nitrate solution and the results are extremely successful. It was observed that particle size is reduced by reduction of concentration.