# Presentation: 778838

## Target Material Characterization Apparatusand Measurement Techniques Measurements of  Diffusive, Effusive and Electrochemical transport Motivation 

- Direct measurements of the chemical interactions between the RIB species and target / ion source - fundamental limitation of the traditional ISOL technique - isolating the critical phenomena
- Provide a matrix for initial investigations into the feasibility of developing new beams: D and a must be within a reasonable range before investing time and resources
- Provide a matrix for direct investigation of new-concept techniques such as electrochemical mass transport and other methods

## Target Material Characterization Apparatus Measurement Technique 

- Introduce the stable analogue of the RIB species under investigation either as a gas or vapor into sample volume exposed to hot membrane.
- Measure the time profile of the permeation and fit to solutions of Fick’s second law determining **D **( D>10-9 cm2/s )
- Replace solid membrane with tube long, thin capillary tube with dimensions chosen so that Dcap>>Dsolid.  Repeat diffusion measurements extracting ******a** from flow equations such as the Clausing relation

## Target Material Characterization Apparatus Measurement Technique (con’t)  

- The permeation constant **K**=bD can also be measured from the saturation flow-rate.  This allows determination of the solubility of the sample gas as a function of sample pressure.
- This simplified configuration allows direct measurement of new techniques of mass transport such as: bulk or surface electrochemical (electrolytic) transport, electrochemical suppression (pumping) of unwanted isobars or vapors and the effects of physical or chemical carrier vapors.

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## Determination of D from the measured time profile - solution to Fick’s second law

## Measurements of the diffusion coefficient:fitting the solution to the measured time profile 

- Time (min)

- Flow rate (arb. units)

**Diffusion of ****16****O in ZrO****2****/Y****2****O****3 ****(x****YO****=0.1) T=832 C**

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## T=915 C

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## Measurement of mean surface adsorption timesa

- Replace diffusive membrane with a long narrow capillary channel composed of the target or ion source material under investigation
- Select channel dimensions to such that Dtube>> Dbulk and l>>r
- Verify geometry using by flowing a mass range of the noble gases
- Rapidly fill one side of capillary channel with a sample gas or vapor while monitoring RGA response
- Mean surface adsorption times can be related to an effective diffusion coefficient, for example, in the molecular flow range:

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## Example of surface adsorption time measurement

**Example of surface adsorption time measurement**

- Mean adsorption time (ms)

- Measured  delay time (min)

- Capillary time =100 m  l=1 cm for O2 at 1000 C

## A tool to investigate new methods of mass transport

- Once the material has been characterized in terms of D and a: the effect of alternative mass transport techniques can be investigated.
-  For example, the above measurements could be repeated with an electric field applied across the membrane and electrochemical transport investigated.  An effective D could then be measured.
- To investigate electrochemical surface migration, a potential could be set up along a capillary tube by passing a current through it.

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## Ionic transport under an electrochemical potential gradient 

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## Conclusions

- We have shown that the diffusive measurement technique gives reasonably accurate measurements of D for 16O and 18O in ZrO2/ Y2O3 (x=0.1) over a 400 C temperature range.
- The successful diffusion measurements suggest determination of characteristic surface - particle adsorption times should also be readily achieved.
- The electrical potential developed across the sample material shows the correct dependence on  PO2 as predicted by the Nernst equation.
- Repeating the 16O and 18O diffusion measurements with an external electrical potential across the material resulted in a ~103 mass transport enhancement over thermal pure diffusion.
- Initial results of the F investigation (one experimental run) suggest fast electrochemical transport of F through ZrO2 / Y2O3.   Data suggests Deff > 10-7 cm2/s when an electric field of ~3 V/mm is applied at 1005 C.

## Electrochemical transport through YSZ  Conclusions 

- The electrical potential measured across the sample material showed the correct PO2 dependence as predicted by the Nernst equation
- Repeating the 16O and 18O measurements with an external electrical potential across the materials resulted in an ~103 flow enhancement over thermal diffusion.  The enhancement was increasing with increasing temperature.
- Initial results of the F investigation (one experimental run) suggest fast electrochemical transport of F through ZrO2 / Y2O3 (x=0.1).  Data suggests Deff> 10-7 cm2/s when an electric field of ~3 V/mm is applied at 1005 C