The Natural Materials Analytical Research Laboratory (NMARL) offers analytical services designed specifically to address engineering problems in a wide range of fields. Analytical facilities combined with an experienced team of researchers provide a full range of advanced materials characterization and data interpretation.

Instrumentation

• Scanning Electron Microscopes (SEMs)
  The NMARL has the following SEMs available: JEOL 5800 with a NORAN Instruments energy-dispersive x-ray detector system, GW Electronics enhanced backscatter detector, and a NORAN Instruments Voyager IV microanalysis system and JEOL 5800 LV (LV is for manual control of the vacuum system to obtain a low vacuum) with a PRINCETON GAMMA TECH (PGT) SPIRIT Instruments energy-dispersive x-ray detector system and microanalysis system. Elements higher than atomic number 6 can be analyzed with an accuracy of 0.1 wt%. Standard and standardless quantification is available. The JEOL 5800 LV also has a HKL TECHNOLOGY electron backscatter diffraction (EBSD) system. The system is composed of a detector, essentially a digital camera charge-coupled device (CCD) chip placed behind a phosphor screen and interfaced with SEM. EBSD allows crystallographic information to be obtained from samples in the SEM.
  
  QEMSCAN is a surface analytical tool that allows for automated quantitative evaluation of minerals by matching spectra collected on the sample with a predefined lookup table then assigns and quantifies the mineral phases or chemical compositions on a particle-by-particle basis, with details down to the submicron resolution at relatively short time scales. The main components of the system include a Carl Zeiss motherboard SEM, four high-speed BRUKER energy-dispersive x-ray detector system silicon drift detectors (SDDs), an automated sample stage, a signal-processing unit, and proprietary software for mineral classification and quantification.
  
  The main advantages of the system are high speed and digital images of the analyzed samples. It typically collects spectrum at a point for a total of 1000 x-ray counts in about 5 milliseconds; thus it can process about 100,000 spectra in 1 hour. Typical output data include digital images of samples which use colored pixels to represent different mineral phases, mineralogical composition and morphology, mineral grain-size distributions, and pixel-by-pixel elemental information.
  
  SEM Techniques
  
  
• X-Ray Fluorescence (XRF)
  Rigaku RIX2100 is a wavelength-dispersive x-ray system that is good for elements above atomic number 6 with accuracies that can be attained to the ppm level (traditional reporting to 0.1 wt%). Standards must be available for elements to be quantified.
  
  XRF Techniques
  
  
• X-Ray Diffraction (XRD)
  BRUKER AXS D8 ADVANCE is a state-of-the-art research-grade XRD instrument for conducting phase identification, ab initio structure determination, and quantitative phase analysis (QPA).
  
  XRD Techniques

Analytical Techniques

• Computer Controlled Scanning Electron Microscopy (CCSEM)
  The CCSEM is an automated SEM technique that determines quantity, particle size, and chemistry, ideally for particles 1 µm to 100 µm in size (has been modified to include particles 1 µm to 300 µm). It is used for coal, coal ash, biomass, and biomass ash. Because the technique can be used on both fuel and ash, direct comparisons can be made and inorganic transformations inferred.
  
• SEM Point Count (SEMPC)
  SEMPC is an automated SEM technique that determines bulk chemistry and can be used to determine silicate viscosity distribution. It is used for deposits, coal ash, and biomass ash.
  
  
• Morphology
  Morphology is a manual SEM technique of examining material for visual appearance (surveying), spot and/or area chemical analysis, spatial arrangement of chemical phases, crystallography, line scans, and mapping of distribution or particular elements.
  
  
• WETSEM– WETSEM is a technique for examining and/or analyzing wet samples in the SEM. Any type of nonhazardous wet sample is placed in the specially designed capsules, and material is analyzed/examined using the SEM.
  
  
• EBSD– EBSD is a technique that allows crystallographic information to be obtained from samples in the SEM. A stationary electron beam strikes a tilted crystalline sample, and the diffracted electrons form a pattern on a fluorescent screen. Just as in powder x-ray diffraction, these patterns are characteristic of the crystal structure and orientation of the sample region from which it was generated. Computer software then compares this pattern to a known database and thus identifies, or indexes, the crystalline phase. Maps can be produced that include information such as crystal phases, crystal orientation, and residual stress.
  
  
• XRF– XRF is a technique that provides the bulk chemical composition of samples. Most often, samples are powders pressed into pellets, but the fusion pellet process can be used to make glass pellet. Quick semiquantitative determinations can be made for atomic numbered elements of 5 through 92. The XRF is used in conjunction with chemical fractionation
  
  
• Chemical Fractionation – Chemical fractionation is a wet-chemistry technique used to quantitatively determine the modes of occurrence of the inorganic elements in coal, based on the extractability of the elements in solvents. This is an especially good technique for low-rank coals and biomass that can have significant amounts of organically bound elements, which are dispersed within the organic matrix of the material, essentially making them invisible to SEM.
  
  The following solvents are used: water – removes soluble inorganics (water soluble salts like NaCl), ammonium acetate – removes inorganic ion-exchangeable cations associated with organic acid groups, hydrochloric acid – removes elements held in coordination complexes within the organic structure as well as acid-soluble minerals such as carbonates, sulfates, and oxides, as well as nonextractable elements associated in the coal as silicates, aluminosilicates, sulfides, and insoluble oxides.
  
  Portions of the sample are removed after each solvent extraction, then dried, ashed, and analyzed by XRF. Data can be used in combination with CCSEM mineral data to determine the distribution of all inorganic material in the coal.
  
  
• XRD– XRD is a qualitative to quantitative technique used for problems ranging from the identification of minor and clay phases to determining the anisotropic thermal expansion coefficients of novel materials. Phases are identified using the automated search–match PDF2 database and TOPAZ, the most widely used commercial software for whole pattern fitting; Rietveld, Pawley, and LeBail methods; indexing; quantitative phase analysis; and ab initio structure determination. Depending on sample preparation and composition, QPA can determine the absolute amounts of crystalline phases down to 0.1 wt%. XRD can also identify the presence of amorphous material (glass) but not the composition.
  
  The system is capable of performing thin film analysis, stress analysis, and texture analysis.