Postdoctoral Researcher (PREP0001688)

6-port SPHERE validation and non-destructive mechanical characterization method for UV-exposed specimens

 This position is part of the National Institute of Standards (NIST) Professional Research Experience (PREP) program. NIST recognizes that its research staff may wish to collaborate with researchers at academic institutions on specific projects of mutual interest, thus requires that such institutions must be the recipient of a PREP award. The PREP program requires staff from a wide range of backgrounds to work on scientific research in many areas. Employees in this position will perform technical work that underpins the scientific research of the collaboration.

PREP Researcher associate will conduct laboratory accelerating weathering exposure experiments on various polymer systems using the commercially viable version (the 0.5 m – 6-port) SPHERE) of NIST SPHERE (Simulated Photodegradation via High Energy Radiant Exposure) device and develop validation protocols to confirm the 0.5 m (6-port) SPHERE performance against the current 2m SPHERE. It is crucial to demonstrate the results from 6-port exposure experiments do not exhibit any unnatural degradation behavior due to high UV intensity (~ 4x higher than that of 2m SPHERE), especially due to larger contributions from the low UV wavelength (<295 nm) regions. The effect of lower UV wavelength on degradation pathway and its impact on reciprocity law will be investigated using different NG filters to identity the root cause.  In addition to 6-port validation, a non-destructive mechanical characterization method using dynamic mechanical analyzer (DMA) will be developed to replace the large uncertainty and labor/sample intensive tensile test (destructive method) for monitoring mechanical changes of exposed specimens.  Job duties include conducting 6-port UV exposure experiments and comparing to the results of outdoor natural weathering; property characterization (physical, optical, & chemical); mechanical measurements using tensile test and DMA; metadata collection/recording/analyses; developing measurement protocols; technical presentations and reports.

The work will entail...

Key responsibilities will include but are not limited to:

  • Review literature and exposure results from previous 2m SPHERE and FL outdoor.
  • Investigate the effect of lower UV wavelength on degradation pathway and its impact on reciprocity law – using different NG filters; characterize the chemical, optical and machinal properties of the laboratory exposed samples using ATR-FTIR, UV-Vis, tensile test, nanoindentation & microscopy.
  • Develop non-destructive mechanical characterization method using DMA to UV-Vis exposed PE samples at different UV exposure time and correlated to results from tensile test (destructive method.
  • Analyze degradation data and determine the degradation rate and pathway.
  • Present results in the group and other relate meeting, writing protocols and technical reports.
  • Ensure that results, protocols, software, and documentation have been archived.


  • A Ph.D. degree in mechanical engineering, Chemical or Materials Engineering background, or a related polymer science field.
  • Hand-on Laboratory experiences on tensile test, DMA, nanoindentation, DSC, FTIR spectroscopy, AFM, optical microscopy
  • Experience using analysis software (e.g., Excel, Origin)
  • Experience using R or python for database and data analysis is a plus
  • Ability to work with real-time event data at scale.
  • Ability to develop prototypes of tools needed to analyze data.
Interested candidates should submit applications, including a cover letter and full curriculum vitae.

Privacy Act Statement

Authority: 15 U.S.C. § 278g-1(e)(1) and (e)(3) and 15 U.S.C. § 272(b) and (c)

Purpose: The National Institute for Standards and Technology (NIST) hosts the Professional Research Experience Program (PREP) which is designed to provide valuable laboratory experience and financial assistance to undergraduates, post-bachelor’s degree holders, graduate students, master’s degree holders, postdocs, and faculty.

PREP is a 5-year cooperative agreement between NIST laboratories and participating PREP Universities to establish a collaborative research relationship between NIST and U.S. institutions of higher education in the following disciplines including (but may not be limited to) biochemistry, biological sciences, chemistry, computer science, engineering, electronics, materials science, mathematics, nanoscale science, neutron science, physical science, physics, and statistics. This collection of information is needed to facilitate administrative functions of the PREP Program.

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