Your Guide to ONH Analysis of Different Shaped Samples

Inorganic materials such as metals (e.g., iron, copper), alloys (e.g., steel, brass), and ceramics (e.g., silicon carbide, boron nitride) are often subjected to extensive mechanical and chemical testing.

Mechanical testing may include the determination of properties like hardness, density, or tensile strength. On the chemical side, analysis can involve identifying the elemental composition of metals (such as iron, copper, or chromium) as well as nonmetals like carbon and sulfur, as well as gases such as oxygen, nitrogen, and hydrogen.

The presence of these gases, especially oxygen, nitrogen, and hydrogen, can have a significant impact on the mechanical properties of inorganic materials. As such, gas content analysis plays a critical role in quality control, helping ensure materials meet performance and safety standards.

Effects of gases on a steel sample. Source: ELTRA GmbH

A common analysis technique for O/N/H determination is inert gas fusion with analyzers like the ELEMENTRAC ONH-p2. This analyzer is compliant with all relevant international standards like the ASTM E 1019, ASTM 1409, DIN EN 3976, and many others.

Fig 1. ELEMENTRAC ONH-p2. Image Credit: ELTRA GmbH

Inert gas fusion analyzers are focused on the measurement of oxygen, nitrogen, and hydrogen and show several advantages compared to spectrometric techniques like XRF or OES.

ONH analyzers, such as the ELEMENTRAC ONH-p2, are capable of determining oxygen, nitrogen, and hydrogen concentrations across a wide range, from below 0.0001 % up to high percentage levels, in various inorganic materials, including metals, alloys, and ceramics. This level of sensitivity and range is not achievable with techniques like Optical Emission Spectroscopy (OES) or X-ray Fluorescence (XRF).

Other sample types can be processed in a variety of shapes, significantly reducing the time required for sample preparation. This article highlights how commonly used sample forms are handled in oxygen, nitrogen, and hydrogen analysis.

Typical Sample Shapes

Chemical analysis can generally be performed on samples in a variety of physical forms.

Source: ELTRA GmbH

Only inorganic solid samples, such as metals or ceramics, can be processed for O/N/H analysis via inert gas fusion analyzers. However, due to the production or sample preparation process, the samples can be present in very different shapes.

The following pictures illustrate typical sample shapes which can be analysed with the ELEMENTRAC ONH-p2:

Pins. Image Credit: ELTRA GmbH

Sheared Samples. Image Credit: ELTRA GmbH

Granule, drilled, chipped sample. Image Credit: ELTRA GmbH

Powders. Image Credit: ELTRA GmbH

Analysis of the Different Shaped Samples

All of the sample shapes mentioned above can generally be analyzed using the ELEMENTRAC ONH-p2. However, depending on the specific shape, minor software adjustments may be necessary, or a sample capsule might be required to introduce the material into the furnace.

To help clarify these adjustments, the following section outlines each step involved in the ONH analysis process:

1. Log in the Sample with its Weight in the Software: Begin by logging the sample into the software, making sure to select a suitable pre-installed application. ELTRA provides optimized settings based on different sample shapes. Be aware that some standards, such as those for titanium analysis, specify a maximum sample weight—make sure you're in compliance with these limits.
2. Place a New Graphite Crucible on the Lower Electrode: The graphite crucible serves as the standard reaction vessel in ONH analysis. Its size and type remain the same regardless of the sample shape, so no adjustments are needed here.
3. Fill in the Sample in the Sample Port: Before analysis, it's essential to remove atmospheric gases from the sample to ensure accurate O/N/H results. To do this, flush the sample with an inert gas—typically helium or argon. Solid, granular, or drilled samples can be introduced directly into the sample port. However, powder samples must be placed in capsules before they are loaded for analysis.
4. Press Start in the ELEMENTS Software: From this point on, the analysis process runs automatically. The system measures the gases released during the analysis using infrared cells and/or a thermal conductivity cell.

Solid sample. Image Credit: ELTRA GmbH

Granule sample. Image Credit: ELTRA GmbH

Powder in a capsule. Image Credit: ELTRA GmbH

Typical Results of ONH Analysis

Regardless of the sample’s shape or chemical composition, precise analysis can be achieved consistently, with each measurement typically completed within a cycle time of 3 to 4 minutes.

Source: ELTRA GmbH

Summary and Conclusion

Inert gas fusion using the ELEMENTRAC ONH-p2 offers a user-friendly, standards-compliant method for determining oxygen, nitrogen, and hydrogen content in inorganic samples. Compared to spectrometric techniques, this approach is generally less sensitive to sample shape and requires less intensive preparation. With the right application settings, reliable analysis of powders, granules, or solid samples is straightforward and efficient.

This information has been sourced, reviewed and adapted from materials provided by ELTRA GmbH.

For more information on this source, please visit ELTRA GmbH.