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 CollegeBaltimore, MD

Stainless Steel Milling Vials

What exactly is ball milling?

SPEX 8000 Mixer Mill

3CuO + 2Al Al2O3 + 3Cu2CuO + Ti TiO2 + 2Cu

example reactions:

Sample 975 : CuO / Al mixture 3 grams - 3 Large balls

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Ignition time (seconds)

Via

l te

mp

era

ture

(C

els

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Trends in Temperature When Ignition Occurs in Individual Samples

Al Reduction of Cu2O

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Charge Mass (g)

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rma

lize

d Ig

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Tim

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3 Large

2 Large4 Large

Ignition Trends from Summer 2001 Work

New material systems that have been investigated:

Bi2O3 + 2Al Al2O3 + 3Bi

3Ag2O + 2Al Al2O3 + 6Ag

3CuS+ 2Al Al2S3 + 3Cu

3Cu2S + 2V V2S3 + 6Cu

3CuS + 2V V2S3 + 3Cu

3ZnO + 2Al Al2O3 + 3Zn

Ignition

No ignition

3CuO + 2Al Al2O3 + 3Cu2CuO + Ti TiO2 + 2Cu

3PbO + 2Al --> Al2O3 +3Pb

Cu Oxide Ignition Trends; as previously looked atRelationship between total mass of CuO / Ti Powder to

the ignition time with 3 large balls

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0 2 4 6

powder mass (g)

ign

itio

n t

ime

(s

)

Relationship between total mass of CuO / Al Powder to the ignition time with 3 large balls

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0 2 4 6

powder mass (g)

ign

itio

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(s)

Comparison of CuO System’s Ignition Times as mixed with Aluminum and Titanium Powders

6CuO + 2Al 3Cu2O + Al2O3

3Cu2O + 2Al Al2O3 + 6Cu

3CuO + 2Al Al2O3 + 3Cu

Instead of single step:

A two step reaction:

may contribute to additional transitory region

ΔH= 287.7 kcal/mol

ΔH= 304.8ΔH= 270.6

3CuO + 2Al Al2O3 + 3Cu

Is it just the copper that is causing the transitory regions?

a look into bismuth...

Relationship between the total mass of Bi2O3 / Al Powder to the ignition time with 3 large balls

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0 5 10 15

mass (g)

ign

itio

n ti

me

(s)

Bi2O3 + 2Al Al2O3 + 3Bi

Would the ignition affects of ductile silver compare with copper?

Relationship between total mass of Ag2O / Al Powder to the ignition time with 3 large balls

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0 2 4 6 8 10

mass (g)

ign

itio

n ti

me

(s)

3Ag2O + 2Al Al2O3 + 6Ag

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

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0 2 4 6 8 10

mass (g)

ign

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3PbO + 2Al --> Al2O3

+3Pb

Is the anomaly just unique to the copper oxides or does it apply more generally to other copper compounds as well?

Relationship between total mass of CuS / Al Powder to the ignition time with 3 large balls

010002000300040005000

0 2 4 6 8

mass (g)

ign

itio

n ti

me

(s)

3CuS+ 2Al Al2S3 + 3Cu

Delta temperature varying directly with CuO/Al powder mass using 3 Large steel balls

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0 2 4 6

powder mass (g)

tem

pe

ratu

re c

ha

ng

e

(Ce

lsiu

s)

Delta temperature varying directly with CuO/Ti powder mass using 3 Large steel balls

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0 2 4 6 8powder mass (g)

tem

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Examples of Relative Linearity of TemperatureChanges due to Ignition in various systems

CuS - Al 3 Large Delta Temperature

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mass (g)

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Relationship btw. Total mass of Bi2O3 / Al Powder to the change in temperature with 3 large balls

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mass (g)

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tem

p (

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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