Many techniques are used to characterize and analyze nanomaterials, one of the important techniques is the X-ray Diffractometer. This method is used to gain valuable insights into the structure of nanometers (i.e. 1 to 100 nm-sized materials). Here we provide detailed information about X-ray diffractometer and their applications.
Application of X-ray Diffractometer
Crystal structure analysis
This method is primarily used to determine the crystal structure of nanomaterials. Nanocrystals, nanoparticles, and other nanostructures have unique crystalline properties. Crystallographic properties refer to the characteristics and properties of crystalline materials, including their symmetry, atomic structure, lattice structure, and orientation of crystal planes. These properties play an important role in determining the physical, chemical and mechanical behavior of materials. These unique crystallographic properties influence their physical and chemical behavior. X-ray diffraction can reveal the arrangement of atoms or molecules within these materials.
Particle size and grain size determination
By analyzing diffraction patterns, researchers can quantify the size of nanocrystals or nanoparticles. Broadening of diffraction peaks indicates smaller grain sizes in nanomaterials. This information is important for understanding the nanoscale properties of materials.
Phase identification
XRD helps to identify different phases within a nanomaterial. Nanoparticles can have multiple phases or polymorphs, and X-ray diffraction can distinguish between them. This is important for quality control and material optimization.
Quantitative analysis
X-ray diffractometer allows quantitative analysis of the composition of nanomaterials. Researchers can determine the relative amounts of different crystal states or components in a nanoscale sample.
Structure and Preferred Orientation
Some nanomaterials may have a preferred orientation of crystal planes due to processing or synthesis methods. XRD can reveal such structure or preferred orientation, which affects material properties.
Stress and Strain Analysis
Residual stress and strain within nanomaterials can be assessed by X-ray diffraction. This information is valuable for understanding the mechanical behavior and reliability of nanomaterials in various applications.
Defect characterization
X-ray diffractometer can provide insights into defects, vacancies, and lattice defects in nanomaterials. These defects significantly affect the electronic and optical properties.
Nanocomposite characterization
When nanomaterials are incorporated into composites, XRD can help determine their distribution, alignment, and interactions in the composite matrix.
In Situ and Operando Studies
X-ray diffraction techniques can be adapted to in situ and operando experiments, allowing researchers to observe structural changes of nanomaterials under different environmental conditions or during chemical reactions.
in X-ray diffractometry tungsten is commonly used as cathode material for the following reasons:
- High melting point: when electron bombardment in an Xray tube it produces high temperature therefore Tungsten withstands this temperature because which is contains high melting point of around 3,422 degrees Celsius (6,192 degrees Fahrenheit). This stability ensures stable X-ray generation over time.
- Efficiency: this material provides efficient electrons when heated. This produces a steady stream of electrons needed to produce X-rays through electron impact with the anode material.
- Durability: Tungsten is long-lasting and can withstand repeated electron bombardment without harming or contaminating the X-ray tube.
- Broad Spectrum: Tungsten produces a broad spectrum of X-rays, covering a wide range of energies. This versatility is useful for a variety of applications, as it allows researchers to tailor X-ray beams to the specific needs of the analysis.
tungsten’s high melting point, stability, efficiency, durability, and broad X-ray spectrum make it an excellent option as a cathode material in X-ray diffractometers for generating the necessary X-rays for sample analysis.
Why does vacuum condition used in X-ray Diffractometry?
There are several important in maintaining of vacuum condition inside the X-ray tube in X-ray diffractometry
- Prevention of Gas Interference: when the vacuum chamber there the presence of other gases in zero therefore no gases absorb and scatter the x-rays. this vacuum prevents inaccurate measurements and constant the intensity of the X-ray beam reaching the sample.
- Enhanced Electron Flow: The number of gas molecules that can collide with electrons is greatly reduced in a vacuum. If less energy is lost in collisions, the cathode can more efficiently generate high-energy electrons as it heats up. The end result is an X-ray beam that is very stable and powerful.
- Reduced Thermal Conductance: The cathode’s surrounding medium’s thermal conductivity is decreased in a vacuum. This aids in preserving the cathode’s stable, high temperature, which is essential for effective electron emission.
- Prevention of Oxidation: The cathode material, which is typically made of tungsten, and other components inside the X-ray tube are protected from oxidation and damage by the vacuum’s lack of oxygen. This guarantees the X-ray source’s durability and dependability.
- Prevention of Contamination: The vacuum environment reduces the risk of contamination inside the x-ray tube. Impurities or contaminants can change the composition of the X-ray beam or affect the performance of the tube.
Components and Processes in X-ray Diffractometer
X-ray Diffractometry and X-ray Tube
X-ray diffraction is an important technique used to analyze the crystal structure of materials. This technique involves an X-ray tube with a cathode and anode. The cathode is typically made of tungsten, while the anode can be composed of materials such as Mo, Cu, Co, Fe, and Cr. Within the X-ray tube, the cathode emits X-rays that strike the anode, resulting in the generation of X-rays.
HT Generator and its Function
HT, or High-Tension, refers to the generator used in conjunction with the X-ray tube. It provides a stable source of radiation. The generator is built using an HT transformer/rectifier and power and control electronics. The power electronics supply low voltage to the HT transformer, and the control electronics ensure stable power output at the correct settings.
Sample Illumination and Detection
X-rays are emitted, collimated, and directed towards the sample. The sample and detector are rotated according to Bragg’s law. The detector records the X-ray signals, converts them to a count rate, and displays the results on a computer or printer.
Sample rotation is denoted as θ, and the X-ray detector rotation is referred to as 2θ. These angles are set to capture different X-rays at various angles.
Goniometer
The instrument used to maintain the angles and control sample rotation is termed a goniometer. Typical powder patterns are scanned with 2θ angles ranging from 5° to 70°.
To identify unknown crystalline materials, X-ray powder diffraction is one of the most widely used techniques, particularly for inorganic compounds and minerals. Determining the characteristics of these unknown crystals contributes significantly to the fields of geology, environmental science, material science, engineering, and biology.
Some applications of X-ray powder diffraction include:
- Characterization of crystalline materials
- Identification of fine-grained minerals, such as clays and mixed-layer clays, which can be challenging to determine optically
- Determination of unit cell dimensions
- Measurement of sample purity.
Strengths of X-ray Diffractometry
- Rapid and powerful identification: XRD can quickly identify unknown minerals, typically taking less than 20 minutes.
- Provides specific and clear mineral determination in most cases.
- Requires a relatively small sample size for analysis.
- The wide availability of XRD units.
- Relatively straightforward data interpretation.
Limitation for X-ray Diffractometer
Homogeneous and Single-Phase Materials
it most suitable for homogenis and single-phase metreals. if it is multiple phase or not well mixed which is challenging to obtain accurate and interpretable diffraction patterns.
Access to a Standard Reference File
for their successful identification, XRD relies on the reference database. XRD identifies the materials they compare the known inorganic compounds information to classify the unknown materials.
Sample Quantity and Powdering
The sample must frequently be pulverized into a fine powder before using XRD. This is due to the method’s reliance on the dispersion of individual crystalline grains inside the sample from X-rays. For a precise diffraction examination, samples must be in the form of a fine powder. Additionally, a substantial amount is required because the sample size is usually expressed in tenths of a gram.
Detection Limit for Mixed Materials: for the mixed compound materials limit of around less than 2 % Detection (e.g., a mixture of two different compounds).
Indexing for Nonisometric Crystal Systems
Indexing, which involves determining the unit cell parameters and crystal symmetry, can be more challenging for materials with nonisometric (non-cubic) crystal systems. These systems require more complex mathematical analyses for accurate determination.
Peak Overlay for High Angle “Reflections”
Peak overlay can happen in XRD, particularly for high-angle reflections. This means that the diffraction peaks from various crystallographic planes may partially or entirely overlap in complicated materials. Diffraction pattern interpretation may become more challenging as a result.
