Transcript No Slide Title

Like SHS, is loose powder ignition a key
process within mechanochemical
reactions (ball milling), or is it just an
anomaly for Cu2O?
J. Zeck, Dr. Takacs, and Dr. Bakhshai Goucher
College
Baltimore, MD
What exactly is ball milling?
Stainless Steel Milling Vials
SPEX 8000 Mixer Mill
example reactions:
3CuO + 2Al  Al2O3 + 3Cu
2CuO + Ti  TiO2 + 2Cu
Vial temperature (Celsius)
Trends in Temperature When Ignition Occurs in
Individual Samples
Sample 975 : CuO / Al mixture 3 grams - 3 Large balls
50
40
30
20
10
0
0
100
200
Ignition time (seconds)
300
400
Ignition Trends from Summer 2001 Work
Normalized Ignition Time (s)
Al Reduction of Cu 2O
2500
3 Large
2 Large
4 Large
2000
1500
1000
500
0
0
2
4
6
Charge Mass (g)
8
10
New material systems that have been investigated:
3CuO + 2Al  Al2O3 + 3Cu
2CuO + Ti  TiO2 + 2Cu
Bi2O3 + 2Al  Al2O3 + 3Bi
3Ag2O + 2Al  Al2O3 + 6Ag
3CuS+ 2Al  Al2S3 + 3Cu
Ignition
3PbO + 2Al --> Al2O3 +3Pb
No ignition
3Cu2S + 2V  V2S3 + 6Cu
3CuS + 2V  V2S3 + 3Cu
3ZnO + 2Al  Al2O3 + 3Zn
Cu Oxide Ignition Trends; as previously looked at
ignition time (s)
Comparison of CuO System’s
Ignition Times as mixed with
Aluminum and Titanium
Powders
Relationship between total mass of CuO / Ti Powder to
the ignition time with 3 large balls
Relationship between total mass of CuO / Al
Powder to the ignition time with 3 large balls
80
70
60
50
40
30
20
10
0
0
2
4
powder mass (g)
ignition time (s)
100
80
60
40
20
0
0
2
4
powder mass (g)
6
6
Instead of single step:
3CuO + 2Al  Al2O3 + 3Cu
ΔH= 287.7 kcal/mol
A two step reaction:
6CuO + 2Al  3Cu2O + Al2O3
3Cu2O + 2Al  Al2O3 + 6Cu
ΔH= 304.8
ΔH= 270.6
may contribute to additional
transitory region
3CuO + 2Al  Al2O3 + 3Cu
Is it just the copper that is causing the transitory regions?
a look into bismuth...
ignition time (s)
Relationship between the total mass of Bi2O3 / Al
Powder to the ignition time with 3 large balls
2000
1500
1000
500
0
0
5
10
mass (g)
Bi2O3 + 2Al  Al2O3 + 3Bi
15
Would the ignition affects of ductile silver compare with copper?
ignition time (s)
Relationship between total mass of Ag2O / Al
Powder to the ignition time with 3 large balls
4000
3000
2000
1000
0
0
2
4
6
8
mass (g)
3Ag2O + 2Al  Al2O3 + 6Ag
10
How do the ignition times of lead oxide compare?
Relationship between total mass of PbO / Al Powder to
the ignition time with 3 large balls
ignition time (s)
2000
1500
1000
500
0
0
2
4
6
8
mass (g)
3PbO + 2Al --> Al2O3 +3Pb
10
Is the anomaly just unique to the copper oxides or does it
apply more generally to other copper compounds as well?
ignition time (s)
Relationship between total mass of CuS / Al Powder
to the ignition time with 3 large balls
5000
4000
3000
2000
1000
0
0
2
4
6
mass (g)
3CuS+ 2Al  Al2S3 + 3Cu
8
Examples of Relative Linearity of Temperature
Changes due to Ignition in various systems
Delta temperature varying directly with CuO/Ti powder
mass using 3 Large steel balls
Delta temperature varying directly with CuO/Al
powder mass using 3 Large steel balls
35
30
25
20
15
10
5
0
temperature change
(Celsius)
temperature change
(Celsius)
25
20
15
10
5
0
0
2
4
6
0
8
2
4
6
powder mass (g)
powder mass (g)
Relationship btw. Total mass of Bi2O3 / Al Powder
to the change in temperature with 3 large balls
CuS - Al 3 Large Delta Tem perature
30
40
delta temp (C)
delta temp
25
20
15
10
5
30
20
10
0
0
0
1
2
3
4
mass (g)
5
6
7
8
0
5
10
mass (g)
15
Atomic Force Microscopy Investigation:
CuO/Al 2 Gram Powder Sample—Layer Study
Atomic Force Microscopy Investigation:
CuO/Al 5 Gram Powder Sample—Layer Study
Conclusions …
•Alternate process to established SHS
•Isolated case–exhibited only in Copper Oxides
•Cu2O– critical mass transition only
•CuO– critical mass and exponential decay transitions