chapter 8 nanomaterials: Synthesis and characterization
264
Suppose you could make it so? It’s not easy. But materials scientists
like a challenge, and they have risen to this one.
There are three directions of attack, sketched in Figure 8.12. The first
is to break down the structure of a bulk material, reducing the crystal
size to submicron or nanodimensions—the top-down approach. The
second—the intermediate approach—starts with standard micronscale particles, reducing their structure to the nanoscale by milling
techniques. The third is to build the solid up from the atomic scale
or from nanoclusters in a way that retains the scale of is structural
units; this is the bottom-up approach.
top-down processes
Top-down processes are best described this way: Take the material
and drug, beat, and freeze it. Drug it by alloying. Beat it by severe
plastic deformation. Freeze it to stop the fine-scale structure, once
formed, from coarsening.
rapid solidification
Materials would rather be crystals than glasses. If ordered, all atoms
sit at exactly the distance from their neighbors that best satisfies
Figure 8.12
The top-down, intermediate, and bottom-up
approaches to making bulk nanostructured solids.
Mechanical alloying
Micromachining
Inert gas condensation
Sol-gel and self-assembly
Equiangle extrusion
Rapid solidification
Bulk nanostructured
solid
Scale
Macro
mm
Micro
mm
Nano
nm
Intermediate
MFA, 07
Top down
Bottom up
264
Suppose you could make it so? It’s not easy. But materials scientists
like a challenge, and they have risen to this one.
There are three directions of attack, sketched in Figure 8.12. The first
is to break down the structure of a bulk material, reducing the crystal
size to submicron or nanodimensions—the top-down approach. The
second—the intermediate approach—starts with standard micronscale particles, reducing their structure to the nanoscale by milling
techniques. The third is to build the solid up from the atomic scale
or from nanoclusters in a way that retains the scale of is structural
units; this is the bottom-up approach.
top-down processes
Top-down processes are best described this way: Take the material
and drug, beat, and freeze it. Drug it by alloying. Beat it by severe
plastic deformation. Freeze it to stop the fine-scale structure, once
formed, from coarsening.
rapid solidification
Materials would rather be crystals than glasses. If ordered, all atoms
sit at exactly the distance from their neighbors that best satisfies
Figure 8.12
The top-down, intermediate, and bottom-up
approaches to making bulk nanostructured solids.
Mechanical alloying
Micromachining
Inert gas condensation
Sol-gel and self-assembly
Equiangle extrusion
Rapid solidification
Bulk nanostructured
solid
Scale
Macro
mm
Micro
mm
Nano
nm
Intermediate
MFA, 07
Top down
Bottom up