In our previous article, we explored what X-Rays can reveal—from internal structures and elemental composition to thickness, density, and crystal structure.
But an important question remains:
How can one technology provide so many different types of information?
The answer lies in the different ways X-Rays interact with matter.
Depending on the physical interaction being measured—transmission, fluorescence, diffraction, absorption, or scattering—X-Ray systems can perform very different analytical tasks. Each method is designed to answer a specific engineering or scientific question.
Here are six of the most widely used X-Ray analysis methods in modern industry.
1. Transmission Imaging – Seeing Inside Objects
Transmission imaging is the most familiar X-Ray technique and forms the basis of many inspection systems.
As X-Rays pass through an object, different materials absorb different amounts of radiation. The remaining X-Rays are captured by a detector to create a grayscale image that reveals internal structures.
Typical applications
Best for: Revealing hidden structures and internal defects without damaging the sample.
2. X-Ray Fluorescence (XRF) – Identifying Elements
Unlike imaging, XRF focuses on what a material is made of.
When a material is exposed to X-Rays, its atoms emit characteristic fluorescent X-Rays. Because every element produces a unique energy signature, XRF can rapidly identify elemental composition and estimate concentration.
Typical applications
Best for: Fast, non-destructive elemental analysis.
A Related Application: Coating Thickness Measurement
The same fluorescence principle can also be used to measure coating thickness.
By comparing the fluorescent signals from both the coating and the substrate, XRF instruments can accurately determine coating thickness from nanometer-scale films to multilayer metallic coatings.
Common applications include plated connectors, electronic components, decorative coatings, and precious metal products.
3. X-Ray Diffraction (XRD) – Understanding Crystal Structure
Knowing which elements are present is only part of the story.
X-Ray Diffraction (XRD) reveals how atoms are arranged inside crystalline materials by measuring diffraction patterns produced when X-Rays interact with ordered crystal lattices.
XRD helps researchers analyze:
Crystal structure
Phase composition
Crystallinity
Grain size
Residual stress
A simple way to remember the difference:
4. Absorption-Based Measurement – Measuring Thickness, Density, and Level
Many industrial measurement systems rely on the attenuation of X-Rays as they pass through materials.
Depending on what is already known, the same physical principle can be used for different purposes.
Thickness Gauging
When material density is known, X-Ray attenuation can be used to measure thickness continuously and without contact.
Typical applications include:
Battery electrodes
Metal strip
Copper and aluminum foil
Plastic films
Paper
Nonwoven materials
Density Measurement
If thickness remains constant, changes in X-Ray attenuation indicate density variations.
This method is widely used for evaluating material uniformity and identifying internal voids or compactness differences.
Level Measurement
Because liquids and gases absorb X-Rays differently, X-Ray sensors can continuously monitor liquid levels inside sealed or high-temperature equipment where conventional sensors may not be suitable.
Best for: Continuous industrial process monitoring.
5. Industrial CT – Building a 3D Model
Industrial Computed Tomography (CT) extends transmission imaging into three dimensions.
By collecting hundreds or thousands of X-Ray projections while the sample rotates, software reconstructs a complete 3D model of the object.
Engineers can virtually “slice” the model from any direction to inspect internal features without physically cutting the sample.
Typical applications include:
Aerospace components
Battery inspection
Precision castings
Additive manufacturing
High-value assemblies
Best for: Complete three-dimensional inspection and defect analysis.
6. X-Ray Scattering – Exploring the Nanoscale
Some materials lack the highly ordered crystal structures required for XRD.
In these cases, X-Ray scattering techniques—including Small-Angle X-Ray Scattering (SAXS) and Wide-Angle X-Ray Scattering (WAXS)—provide valuable structural information.
These methods are commonly used for:
Best for: Investigating nanoscale structures and partially ordered materials.
Choosing the Right X-Ray Method
Each X-Ray analytical technique answers a different question:
| If you need to… | The recommended method |
| Inspect internal defects | Transmission Imaging |
| Identify elements | XRF |
| Analyze crystal phases | XRD |
| Measure thickness | X-Ray Thickness Gauging |
| Build a 3D model | Industrial CT |
| Study nanostructures | SAXS / WAXS |
Understanding these complementary techniques helps engineers, researchers, and manufacturers select the right solution for their specific inspection or analytical requirements.
Coming Next
KeyWay Academy | Fundamentals Series
How to Choose the Right X-Ray Tube for Different Applications
In the next article, we’ll explore how X-Ray tube parameters—including target material, voltage, focal spot size, window material, and power—affect analytical performance across different X-Ray applications.
