9. Wet Chemical Synthesis Of Nano-materials
•Chemical synthesis –
It is the process by the combination and
detachment of components or elements to be obtain.
It is applied to all types of chemical
compounds, but most syntheses are of organic
molecules.
Chemical Synthesis is used for obtaining Nano-
molecules from Complex molecules.
12. Sol-gel Process
The sol-gel process is a method for producing solid
materials from small molecules.
The method is used for the fabrication of metal oxides,
especially the oxides of silicon and titanium.
The process involves conversion of monomers into a
colloidal solution (sol) that acts as the precursor* for an
integrated network (or gel) of either discrete particles or
network polymers.
( *precursor is a compound that participates in a chemical
reaction that produces another compound.)
18. Typical Terms
Common uses for organic solvents are
in dry cleaning (e.g. tetrachloroethylene),
as paint thinners (e.g. toluene, turpentine),
as nail polish removers and glue solvents
(acetone, methyl acetate, ethyl acetate),
in spot removers (e.g. hexane, petrol ether),
in detergents (citrus terpenes)
In perfumes (ethanol).
A solvent is a substance that dissolves a
solute (a chemically distinct liquid, solid or
gas), resulting in a solution
Etching is traditionally the process of
using strong acid to cut into the
unprotected parts of a metal
a precursor is a compound that participates
in a chemical reaction that produces
another compound.
A powder is a dry, bulk solid composed of a
large number of very fine particles that may
flow freely
Editor's Notes
Crystal Structure*
Introduction
Crystallographic Terms and Concepts
Crystal structure is the arrangement of atoms in the interior of a crystal. A fundamental unit of the arrangement repeats itself at regular intervals in three dimensions throughout the interior of the crystal.
A unit cell is a parallelepiped whose edges form the axes of a crystal. A unit cell is the smallest pattern of atomic arrangement. A crystal consists of unit cells stacked tightly together, each identical in size, shape, an orientation with all others. The choice of the boundaries of a unit cell is somewhat arbitrary, being conditioned by symmetry considerations and by convenience.
Table 1 Relationships of edge lengths and of interaxial angles for the seven crystal systems
Crystal system Edge lengths Interaxial angles Examples
Triclinic (anorthic) a ≠ b ≠ c α ≠ β ≠ γ ≠ 90° HgK
Monoclinic a ≠ b ≠ c α = γ = 90° ≠ β β-S; CoSb2
Orthorhombic a ≠ b ≠ c α = β = γ = 90° α-S; Ga; Fe3C (cementite)
Tetragonal a = b ≠ c α = β = γ = 90° β-Sn (white); TiO2
Hexagonal a = b ≠ c α = β = 90°; γ = 120° Zn; Cd; NiAs
Rhombohedral(a) a = b = c α = β = γ ≠ 90° As; Sb; Bi; calcite
Cubic a = b = c α = β = γ = 90° Cu; Ag; Au; Fe; NaCl
