Economical synthesis of nano alumina powder using an aqueous sol–gel method
A B S T R A C T
1. Introduction
In recent years, increasing attention has been focused on the development of nano-sized alumina powders for advanced engineering materials .Conventional processes for synthesizing ceramic nano powder involve mechanical synthesis, vapor phase reaction, precipitation, combustion and sol–gel methods. There are some limitations in all aforementioned methods .Among the various synthesis methods, sol–gel method is the most promising and thus has been widely investigated because it produces solid particles of high purity and high specific surface area. It is known that aluminum alkoxides are very popular for processing of alumina.
A B S T R A C T
1. Introduction
In recent years, increasing attention has been focused on the development of nano-sized alumina powders for advanced engineering materials .Conventional processes for synthesizing ceramic nano powder involve mechanical synthesis, vapor phase reaction, precipitation, combustion and sol–gel methods. There are some limitations in all aforementioned methods .Among the various synthesis methods, sol–gel method is the most promising and thus has been widely investigated because it produces solid particles of high purity and high specific surface area. It is known that aluminum alkoxides are very popular for processing of alumina.
Among the alkoxides, aluminum isopropoxide is currently used in the sol–gel processing of alumina. The high cost of aluminum alkoxides for processing of alumina, probably is a drawback in the commercialization of high purity alumina nano powders. For example, the price of aluminum isopropoxide (250 g) provided from Aldrich and Fluka is 408.36 and 580.76 Euro, respectively. In the present work, an alumina nano powder was synthesized though an aqueous sol–gel method using both low cost Al and AlCl3•6H2O powders (21.75 and 20.25 Euro, respectively, Merck. 1 kg) which has not been reported elsewhere.
2. Experimental procedure The precursor solutions for Al2O3 nano powder were prepared by sol–gel method using AlCl3•6H2O (Merck), Al powder (M.A. university) and HCl (domestic product). At first, the aluminum chloride hexahydrate was mixed with aqueous HCl. The Al powder was then 42 gradually added to the solution. The solution was then stirred using a magnetic stirrer at 95 °C for 4 h to obtain a transparent solution. The obtained gelwas dried at 85 °C for 48 h. The dried gelwas then ground and calcined in a furnace at different temperatures. The obtained powder was ball milled in ethanol media using a high dense alumina jar and high pure alumina balls. The powder was again dried at 80 °C.X-ray diffractionwas carried out for phase analysis of the dried gel and calcined powder using Philips X-pert model with Cu Kα radiation. DTA and TG analyses of dried gel were performed in the range of 25–1200 °C with a rate of 5 °C/min by means of a STA 1460 equipment. The morphology and particle size of synthesized powder were characterized by a Phillips XL30 scanning electron microscope.
2. Experimental procedure The precursor solutions for Al2O3 nano powder were prepared by sol–gel method using AlCl3•6H2O (Merck), Al powder (M.A. university) and HCl (domestic product). At first, the aluminum chloride hexahydrate was mixed with aqueous HCl. The Al powder was then 42 gradually added to the solution. The solution was then stirred using a magnetic stirrer at 95 °C for 4 h to obtain a transparent solution. The obtained gelwas dried at 85 °C for 48 h. The dried gelwas then ground and calcined in a furnace at different temperatures. The obtained powder was ball milled in ethanol media using a high dense alumina jar and high pure alumina balls. The powder was again dried at 80 °C.X-ray diffractionwas carried out for phase analysis of the dried gel and calcined powder using Philips X-pert model with Cu Kα radiation. DTA and TG analyses of dried gel were performed in the range of 25–1200 °C with a rate of 5 °C/min by means of a STA 1460 equipment. The morphology and particle size of synthesized powder were characterized by a Phillips XL30 scanning electron microscope.
