Advancements in Handheld LIBS for Metal Alloy … in Handheld LIBS for Metal Alloy Analysis Don Sackett ... • For alloys, theories are alloys ... Comparison to Handheld X‐ray Fluorescence

Advancements in Handheld LIBS for Metal Alloy Analysis

Don Sackett, CEOSciAps, Inc. Woburn, MA

Confidential and Proprietary SciAps Inc 1

Topics

• How LIBS works,• Recent Advancements in HH LIBS:

• Argon purge – why it’s essential,• Laser technology improvements,• Laser power improvements,

• Safety and Regulatory advantages of laser‐based measurements,• Application Stories,• Questions


Introduction

• LIBS (Laser Induced Breakdown Spectroscopy)• Bench top technology for the past 30 years or so

• Handheld LIBS is a new technology that is advancing rapidly,• Advantages include:

• Wide element range• Light Elements (Li, Be, B, C, N, O, F), • Improved performance on Mg, Al, Si, K, Ca, • Fast,• No X‐Rays

• Early users of handheld LIBS have complained of • Poor repeatability,• Reliance on sample preparation,• Weaker performance on key alloying refractory elements (e.g. Mo, V, W, Ta, Co)

• New advancements in both hardware and software are overcoming these issues


Laser Induced Breakdown Spectroscopy (LIBS!)


• Similar to other Optical Emission techniques like Arc/Spark but utilizes a laser to excite sample

• Can measure any sample medium (powder, solid, liquid, nonconductive),

• Laser is about 50 um diameter

One Advancement – Argon Purge


Argon Purge

• Long established spark optical emission technology,

• A key to repeatable, quantitative chemistry is operating in an argon purge,

• LIBS is very similar to optical emission, but with a laser to produce the plasma rather than electric spark.


Typical mobile spark OES analyzer, with tank of argon gas

Argon Purge Benefits

• Operating in an oxygen free environment reduces quenching of the plasma,

• Oxygen absorbs the plasma light emissions much more than an inert gas,

• Depending on element/wavelength there is 3x‐10x more light when using argon,

• Eliminate interfering lines from vaporized elements forming oxides.


Argon PurgeNo Argon Purge

Stainless 316

Argon, cont’d


• The Z uses a small spot, pulsed laser, • Argon flow rates are very low, • This supports a small, user‐replaceable argon cartridge in the analyzer’s handle.

• Each canister supplies 250 tests,• Cost/test is 2 cents,• Analyzer can be connected to larger tanks for stationary operation.

Another Advancement – Laser Cleaning and Rastering


Laser Cleaning

• LIBS is very sensitive to sample surface conditions,• Nobody in the alloy business wants to take the time to grind samples, • Laser cleaning means firing the laser at the same location multiple times to “burn off” surface material.

• Fire the laser several times to clean, then several more times to collect spectral data for analysis.


Cleaning Pulses: Change in Ca signal

• By firing the laser in a single location, a change in the Calcium signal can be observed as the laser ablates away the surface contaminants,

• Firing at 10 Hz (10 laser pulses/second) is too slow – 1 sec. of cleaning time.


‐0.5

0

0.5

1

1.5

0 5 10 15 20Ca Signal (no

rmalize

d)

Pulse #

Calcium Signal with Consecutive Laser PulsesLocation 1Location 2Location 3

Advancement: Bursting the laser


• Burst the laser at 50 Hz (50 pulses/second) for short periods of time,

• In 0.2 s, fire 10 cleaning shots,• Rapidly burn off material, more thoroughly,

• Reduce to 10 Hz for data collection (0.3 s),

• One location analyzed on sample in 0.5 sec.

The Challenge of Real‐world Samples


• Measuring Mg in an aluminum alloy,

• In OES and LIBS, you calibrate to intensity ratio’s:

Intensity of Mg lightIntensity of base metal light. • Poor cleaning affects both numerator and denominator,

• Mg measurement > 2x high without good surface cleaning.

Laser Rastering

• Why? Benchtop LIBS research shows better analytical results by averaging several locations,

• For alloys, theories are alloys not entirely homogeneous at the 50 um level (laser beam size),

• Grain boundaries, inclusions. • Recommendations from 30 years of LIBS research is to average results from multiple locations to improve repeatability.


Video: An example of a 12 Location raster. Each location is shot with 2 cleaning bursts, followed by 3 “data” pulses

Laser Advancement• New Proprietary SciAps Laser

• Provided best signal intensity compared to other similar off the shelf lasers

• 1064 nm, Class 3B • Pulse Energy of 5‐6 mJ/pulse,

• Compare to other handhelds that use “micro‐joule lasers” 0.1 mJ/pulse,

• Shorter pulse duration: 1 ns instead of 6 ns• Better beam quality, more photons in smaller area• Variable Pulse Rates

• Normal operation at 10 Hz• Burst: 10 pulses in only 0.2 s (50 Hz), followed by gated, 10 Hz operation for 0.3 s, then raster to new location.


Comparison to Handheld X‐ray Fluorescence (XRF)


Analytical Comparisons

• HH LIBS measures virtually every element in the Periodic Table,• H, Li, Be, B, C, N, O, F, Na HHXRF cannot measure at all• Mg, Al, Si HHXRF measures poorly compared to

LIBS• Most difficult elements for HH LIBS: P and S (in alloys)

S (all materials)


Regulatory – X‐ray Requirements

• Annual operator training,• Body and ring badges,• Unannounced inspections from State agencies,• Administrative burden for tracking badges, training requirements and overall radiation safety,


Continued…

11/23/2015 Confidential & Proprietary SciAps Inc 19

• Easier to handle small samples,• Hold them in your hand,• Don’t need to have test stand, laptop, etc.

Laser versus X‐ray

Maintenance Costs

• Far lower maintenance costs:• LIBZ typical repairs are $500, maximum $1,500,

• X‐ray typical repairs are $6,000 ‐ $10,000 due to tube and detector,

• SciAps makes our own lasers and spectrometers and thus can repair at the component level.


Success Stories


Aluminum Alloys• Precise measurements 0.05 – 1% range of key alloying elements Mg, Si, Cr, Cu,• Fast sorting (1‐2 s) of close alloy grades

• 6061/6063/1100, 3003/3005/3105, 7050/7075,• Cast alloys, etc.


Aluminum alloy producers• Looking at 1000 series grades, • Interest in grading alloys by low concentrations Mg, Mn, Cr, Si, etc.


Low Alloy Steels• Looking at 0‐1% Cr, V, Ni, Cu, Mo, Mn in low‐alloy steels,• Evaluated air‐based HH LIBS couldn’t achieve needed precision compared to HHXRF,• Z‐200 successful


Nickel Superalloys:


• Evaluated Z‐200 on their 70 grades of Ni, Co and Ti alloys.• Z‐200 reliably identified 70 out of 70, • Far better than any air‐based LIBS unit,• Superalloys very refractive, hard to get into plasma, thousands of lines,

• High laser energy, argon to maximize signal, high resolution spectrometer to minimize interferences.

Thank you. Questions?


Check out our demo videos:

Scrap Sorting https://goo.gl/gZlLvnGeneral Apps Available https://goo.gl/mnSxUO

SciAps Models

• Z 200• 190 nm – 615 nm• Includes Argon purge for improved sensitivity

• Carbon at 193 nm*

• Z 500• 190 nm – 850 nm,• Mostly for geochem, other non‐alloy applications,

• Adds in O, N, F, Cl, Br, and improved K.


The Argon Difference

Argon PurgeNo Argon Purge

Detect, Measure, Analyze.

Thank You for Attending Today’s Webinar

Your HostTom DouglasSalesRAECO-LIC [email protected]

Our Featured SpeakerDon SackettCEO & [email protected]

Detect, Measure, Analyze.

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Documents

Advancements in Handheld LIBS for Metal Alloy … in Handheld LIBS for Metal Alloy Analysis Don Sackett ... • For alloys, theories are alloys ... Comparison to Handheld X‐ray Fluorescence