POSITIVE MATERIAL IDENTIFICATION (PMI), X-Ray & INSTRUMENTAL ANALYSIS

POSITIVE MATERIAL IDENTIFICATION (PMI)

Positive Material Identification or PMI, is an integral part of process safety management in the petroleum refining, petrochemical, airline and electric power generation industries. In response to a series of accidents resulting from material mix-ups, many companies have instituted stringent PMI programs. Industry organizations have also worked to develop guidelines to assure that the nominal compositions of all alloy components in a process system are consistent with design specifications. MATCO can provide Positive Material Identification (PMI) at the project site, part of an on-site investigatyion or in our laboratories in a moment notice and on rush basis. at MATCO, Thermo’s NITON XLi/XLp 800 Series alloy analyzer is available for in-service PMI applications.

X-ray Diffraction

Eelectromagnetic radiation of wavelength about 1 Å (equivalent to 0.1 nanometers) is called x-rays. These rays are about the same wavelength as the diameter of an atom. They occur in the portion of the electromagnetic spectrum between gamma-rays and ultraviolet light. The discovery of X-rays in 1895 enabled scientists to probe crystalline structure at the atomic level by using diffraction techniques. X-ray diffraction is used in two main areas: the fingerprint characterization and the determination of the structures of crystalline materials . Each crystalline solid has a unique characteristic set of interplanar spacings which may be used as a "fingerprint" for its identification using x-ray diffraction techniques. Once the material has been identified, X-ray crystallography may be used to determine its structure, i.e. how the atoms pack together in the crystalline state and what the interatomic distances and angles are etc. X-ray diffraction is one of the most important characterization tools used in solid state chemistry and materials science. General Uses include:

• Identification of phases and compounds contained in unknown samples

• Quantitative determination of the weight percent in multiphase materials

• Lattice paramter and lattice type determinations

• Characterization of solid phase transformations

• Determination of phase diagrams

• Determination of pressureor temperature induced phase transformations

Energy Dispersive X-ray Analysis

Because all elements have characteristic X-ray energy “fingerprints” those energies can be used both to identify and quantify elements in unknown samples. One technique for doing this is “energy-dispersive x-ray spectroscopy” or EDS. This technique is used routinely on MATCO’s scanning electron microscopes. A similar technique (WDS) is used on electron microprobes, only there the wavelengths of the x-rays are measured, rather than their energies.

EDS techniques allow rapid determination of elemental compositions of areas down into the micron range. The beam of energetic electrons in the scanning electron microscope penetrates several micrometers into the sample surface, so that the EDS results are an average of the compositions of the top layer of the sample, not its absolute surface. Refer to the section on Auger Spectroscopy for a brief discussion of true surface analysis.

Quantification of EDS results, rather than simple identification of the elemental constituents, can be done by a theoretical calculation (using the well known ZAF corrections) or it can be done more precisely using appropriate standards. The only way to get more than semi-quantitative results is to use polished samples such as metallurgical cross-sections. Rough surfaces such as usually used in the SEM make it difficult to get highly precise quantitative results from EDS spectra.

MATCO’s Dan Gibson, Senior Technician. Dan, a vital member of MATCO’s analytical team, can re-build any type of instrument or start from scratch and create a new one

At MATCO, we provide you with a laboratory that you can count on. We can identify the chemical compounds in your samples and determine the size and the shape of the unit cell for any unknown compound using x-ray diffraction. Building on this information and with accurate and reliable test results and appropriate site visits, we can provide you with root cause determination for your corporate materials failures. Future product design, materials selection and quality control decisions can be based this sound foundation.

MATCO's other capabilities include surface analysis equipment (SEM/EDS, AES, EIS...), metallurgical investigations; R&D of new products or improvements to existing products, inspectors for onsite investigations and third party inspections, one to two day seminars on materials selection, corrosion, coating and failure analysis, and litigation support. We can also perform a wide array of routine NACE and ASTM test procedures for identification of materials, evaluating the corrosion resistance of metallic and non-metallic materials and components in adverse environments. If necessary, MATCO personnel can be on site within 48 hours when requested during emergency situations.

Who performs the investigation:

Our team includes Certified Materials / Corrosion / Metallurgical / Chemical Analysis / Coating Specialists and FEA Specialists:

Dr. Zee                       Dr. Gibbon

Dr. Bayer                    Dr. Bavaria

Mr. Gibson                  Mr. Larkin

Mr. Groll