Schafer CorporationAn Employee-Owned Small Business

Schafer Laboratories

Schafer Corporation atSandia National Laboratory1515 Eubank SE, M.S 1196

Albuquerque, NM 87123505 845-7762 (tel.)505 845-7820 (fax)

dgschro@sandia.gov

Advanced Foam Shell Production

Laser IFE Program Workshop

Diana SchroenJon Streit

Glen Southard

Naval Research LaboratoryJune 1, 2001

DSC 6/1/01 2

The Goal Of This Task Is To Produce Hollow Foam Shells.

4 mm foam shell 300 micron foam wall

CH polymer ~ 1 micron cell size 10 - 20 mg/cm3

1 micron carbon overcoat 0.03 micron gold coating

DSC 6/1/01 3

Outer WaterPhase @ 70ºC

W

W

O

Inner WaterPhase Inlet

Organic Polymer Phase Inlet

Stripping Outer Water Phase Inlets

The Overcoated Shells Will Be Produced Using A Two Step Approach.

• In the first step, a droplet generator produces uncoated foam shells.

• We have refurbished the droplet generator to accommodate the larger size spheres.

• Gelation of the oil phase needs to occur about 15 minutes after the complex drop is formed.

Drawing by S. Buckley

DSC 6/1/01 4

In the Second Step, Interfacial Polymerization Produces The Polymer Overcoat.

INTERNAL WATER PHASE

IPA RINSE

POLYMER AND ORGANIC PHASE

The shell is placed in a reactive aqueous solution a wall is built at the interface.

The shell is placed in organic solvent + acid chloride.

WATER PHASE + REACTANT

ORGANIC + ACID CHLORIDE

ORGANIC + ACID CHLORIDE

LIQUID CO2

The organic phase and internal water phase must be removed.

The shell is rinsed with IPA, then liquid CO2. The CO2 is taken supercritical and vented.

DSC 6/1/01 5

To Meet The Requirements Of Density, Cell Size And CH Requires A New Foam.

= CH foam

= IFE region

DSC 6/1/01 6

DVB Is Very Developmental.

• The process for making divinyl benzene (C10H10) foam is an extension of processes used by Steve Letts (LLNL) and Warren Steckle (LANL).

• We have been making prototype samples for about 1 year.• This foam is of interest for many ICF experiments:

– cylinders for SNL Z-pinch – flat foams for NRL– overcoated high density beads for LLNL (Omega)

• The synergism of these requests has hastened development, but the difficulty of microencapsulation requires significant effort. We have hired another chemist, Jon Streit.

• To microencapsulate this system we need to:– determine an efficient surfactant system.– Need to study gelation, the complex drops must gel within 15 minutes of

formation.

DSC 6/1/01 7

We Have Begun Gelation Studies.

• Time to gelation is a function of density.• Clearly the lower the density the more difficult microencapsulation becomes.• We will vary the polymerization conditions, radical initiators, and try adding

small amounts of other CH monomers.

DSC 6/1/01 8

To Enhance Gelation We Need To Raise The Crosslinking.

20

25

30

35

40

45

50

55

60

65

%Reflectance

500 1000 1500 2000 2500 3000 3500 4000

Wavenumbers (cm-1)

• We are using IR spectral analysis to monitor the crosslinking.

• The IR absorption is obviously also important for target survivability and layering.

DSC 6/1/01 9

Deuterated DVB May Be Needed For IR Layering.

• We have produced a deuterated foam target for SNL.

»10 mm tall, 5 mm OD.»30 mg/cm3.»very difficult to handle.»witness piece sent to Schafer

Livermore for IR analysis.

DSC 6/1/01 10

The Foam Shell Production Task Is Linked To The Characterization Task.

• Fred Elsner has already reported on the characterization task.• We have had two meetings to coordinate efforts.• Schafer has produced DVB foam in wedges, spheres and annuli

to assist the characterization efforts.• We have also supplied a list of solvents

– index of refraction– toxicity– cost

DSC 6/1/01 11

We Are Progressing As Expected.

• We have– hired Jon Streit.– refurbished the droplet generator.– ordered and received the chemicals needed for the shell and

the overcoat chemistries.– begun the gelation studies and IR analyses.– assisted the characterization task.

• We will now– begin the emulsion studies.– begin making high

density shells.