ALUMINA NANO PARTICLES

A presentation by:SAMAR NOURELDINOMER MOHAMMEDMARAM FARAH

Alumina can called :

aloxidealoxite, alundum

depending on particular forms or applications.

Alumina nanoparticles applications

alumina are Thermal insulator, High Temperature Stability will allow it to use in many industrial and institutional work.

in ceramic industry. In polishing/abrasive applications. as an absorbent. in the refractories as catalysts. wear resistant coating. medium for chemical chromatography

Sol-Jel method.emulsion combustion method (ECM).Spray Pyrolysis method(hot wall aerosol

synthesis method ).Hydrothermal method.Co-Precipitation method.Mechanical milling.Vapour phase reaction and Combustion

method.

Methods of preparation

Here we will explain only the three most important methods

• nanoscale alpha-alumina (α-Al2O3) powder is smaller than (Nano-Al2O3) but it’s difficult to obtain due to :

α-Al2O3 is in a stable phase after calcining at high temperature.

α-Al2O3 particles tend to aggregate during dehydration process in wet chemistry method.

Sol-gel method can solve these problems

Sol-Jel method

uses relatively low temperature.

can create very fine powder.

the possibility to obtain high purity materials.

Sol-gel method advantages

• There are different precursors used in the synthesis of alumina by sol-gel method were of different chemical nature such as:

inorganic – aluminium chloride (AlCl3) .

organic– aluminium triisopropylate (C3H7O)3Al.

Aluminum isopropoxide Al (OC3H7)3

Particle synthesis

Particle characterization

The produced particles characterized by, X-ray diffraction

The produced particles characterized by SEM micrographs

the particle become finer and less agglomerated until 48 hour stirring. The particle started to agglomerate and to be more dense in structure at 60 h.

TEM analysis

figure” a”

The size of particle after 24 hours of

stirring in range of 270–320 nm and

had a lot of agglomeration.

Figure” b”

the size of particles, after 36 hours of stirring, fell in the range of 250–300 

nm, and had a lot of agglomeration.

Figure”c”

the size of particles, after 48 hours of stirring, fell in the

range of 20-30 nm, and had a good

quality of dispersion.

Figure (d)

after 60 hours of stirring, the sizes of

particles were in the range of 150–

200 nm and a lot of agglomeration and only little dispersion

were observed

Spray Pyrolysis method

Its main application

In metal-matrix composites for nanoreinforcements

Method description

• it’s based on ultrasonic generation of micrometric-sized aerosol droplets and their decomposition at intermediate temperatures (400-800ºC).

• it possible to control important particle properties (size, morphology, chemical composition, etc.) simply by controlling the process parameters (residence time, decomposition temperature).

Particle synthesis

An aqueous precursor solution prepared by dissolving the corresponding amount of aluminium nitrate nonahydrate (Al(NO3)3·9H2O.

The initial solution was atomized using an ultrasonic vibrating frequency of 2.1·106 s-1.

The aerosol transported into a reaction zone and decomposed at 700°C.

Air used as a carrier gas .

the powders were isothermally annealed in air at 800 - 1300 oC for 12 hours (chamber furnace CHESA) to promote phase crystallization.

The particles water collected at exhaust “.

The predicted particle size, Dp, can be expressed as a function of the droplet size, Do.

The amorphous and polycrystalline character of the particles.

Initially the particle morphology does not change significantly with annealing.

As the temperature of thermal treating increase , the η-Al2O3 phase continues and the particles tends to form the peaks (alfa-Al2O3 phase) and loss there spherical shape .

there is a contamination of SiO2 from the quartz tube.

particles obtained by aerosol decomposition are spherical, smooth, non-aggregated and relatively uniform in size(≤ 400 nm).

confirm high compositional uniformity and the exclusive presence of the constitutive elements (Al and O).

Particle characterization

Experimental X-ray diffraction patterns

SEM micrograph of “as-prepared”

Al2O3 particles,

TEM analysis(secondary

particles)

(ECM) method

this method was originally developed in 1997 in Japan.

It is compination of :emulsion process + combustion

technology

The ECM is classified into liquid phase syntheses but it also has the features of gas phase syntheses.

produce high performance ceramic powders

Its main application

An isolated small reaction field.

Short reaction period ” less than half a second”.

gives synthesize fine and chemically homogeneous metal oxide powders.

It’s a continuous fabrication procedure which contributes to lower production costs. 

(ECM)method advantages

Particle formation mechanism(synthesis)

it is simmillary like the Hollow particles have been synthesized by spray pyrolysis where the aqueous droplets containing metal ions are rapidly heated at their surface.

but here the surface of emulsion droplets is rapidly heated by the combustion of the surrounding kerosene film.

The fast heating rate results in the unusually thin shell structure .

collection of the ceramic powder produced

combustion of the atomized emulsion

preparation of an emulsion “ An aqueous solution W/O type

Preparation procedures

Particle characterization

The particles are spherical in shape.

their diameters in the range 200–800 nm.

The particles exhibited the unique characteristics of hollow structure with extremely thin (10 nm) shell.

The specific surface area is 56m2/g.

In XRD profile of the hollow alumina powder The broad peaks are identified with gamma phase alumina.

TEM image of the typical alumina

powder synthesized by

the ECM(1mikro.m)

XRD profile of aluminapowder

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