Outgassing Elements in Electron Microscopes

Image Credit: Thermo Fisher Scientific Phenom-World BV

When electron microscopes function in high vacuum levels, all wet samples loaded into the imaging chamber will instantly begin to outgas.

Particular samples contain microstructures that will combat the phase change, offering positive results with no key concerns. A common example is a fresh leaf. A sample with no firm structure can be imaged if critical point drying or force drying is utilized to prepare it.

Force Drying

To establish if the sample will withstand the vacuum, the use of a further instrument, such as a sputter coater or a desiccator, is suggested. Eventual variations in the sample should be instantly apparent.

Critical Point Drying

Also called supercritical drying, this method causes the evaporation of liquids in the sample, which maintains a low temperature.

The pressure level controls the evaporation, which is brought underneath the vapor tension of the liquid in the sample. Throughout this process, the liquids will produce fractures within the sample, creating changes in the structure.

SEM images of a cucumber’s intact structure.

SEM images of a cucumber’s intact structure. Image Credit: Thermo Fisher Scientific Phenom-World BV

SEM image of a tomato’s peel and interior structure.

SEM image of a tomato’s peel and interior structure. Image Credit: Thermo Fisher Scientific Phenom-World BV

Cooling

Freezing the sample is an alternative to drying methods and will keep the sample structure fully intact.

If the phase change is efficient enough, the liquids in the sample will not produce crystals and the structure will be well-preserved. It is essential to know that the phase change is brief and long-term exposure to a high vacuum will enhance the rate of evaporation.

Low Vacuum

If the moisture content of the sample is not particularly high, utilizing a small amount of sample at a decreased vacuum level can be sufficient to take images. The total quality of the image will be lower, but the sample can be imaged in its initial state.

Small Amount of Sample

Utilizing a small quantity of sample is sometimes enough to include the influences of evaporation and vacuum. The sample can be gathered with a toothpick and a veil of it can be placed on the stub. This method is especially successful with emulsions and gels.

SEM images of (left) spreadable hazelnuts and (right) cacao cream.

SEM images of (left) spreadable hazelnuts and (right) cacao cream. Image Credit: Thermo Fisher Scientific Phenom-World BV

This information has been sourced, reviewed and adapted from materials provided by Thermo Fisher Scientific Phenom-World BV.

For more information on this source, please visit Thermo Fisher Scientific Phenom-World BV.

Citations

Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Thermo Fisher Scientific Phenom-World BV. (2020, January 28). Outgassing Elements in Electron Microscopes. AZoM. Retrieved on December 03, 2024 from https://www.azom.com/article.aspx?ArticleID=18659.

  • MLA

    Thermo Fisher Scientific Phenom-World BV. "Outgassing Elements in Electron Microscopes". AZoM. 03 December 2024. <https://www.azom.com/article.aspx?ArticleID=18659>.

  • Chicago

    Thermo Fisher Scientific Phenom-World BV. "Outgassing Elements in Electron Microscopes". AZoM. https://www.azom.com/article.aspx?ArticleID=18659. (accessed December 03, 2024).

  • Harvard

    Thermo Fisher Scientific Phenom-World BV. 2020. Outgassing Elements in Electron Microscopes. AZoM, viewed 03 December 2024, https://www.azom.com/article.aspx?ArticleID=18659.

Ask A Question

Do you have a question you'd like to ask regarding this article?

Leave your feedback
Your comment type
Submit

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.