X-ray diffraction (XRD) is a non-invasive method for determining the crystalline phase, elemental composition, and mechanical characteristics of substances.
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The essential idea is that the constituent atoms in the crystal lattice cause an X-ray stream to scatter in a number of different directions—a change in the crystal size results in a variation of the width of the X-ray diffraction pattern.
Introduction to X-ray Diffraction
X-ray diffraction is a process in which the molecules of crystals generate a diffraction pattern of the waveforms existing in an incoming stream of X rays due to their equal intervals. The molecular dimensions of the crystal operate on the X rays in the same way as an evenly governed diffraction acts on a light beam.
On June 8, 1912, a thirty-three-year-old scientist named Max von Laue reported his findings of X-ray dispersion in the crystalline lattice as in a three-dimensional beam splitter at the German Physical Society conference at the University of Berlin.
The finding was utilized by two English researchers, W. H. Bragg and W. L. Bragg, father, and son, to validate Barlow's hypothesized conception of rock salt, launching the first X-ray diffraction examination of nanocrystals.
Applications of X-ray Diffraction
Nanomaterials are gaining popularity in a variety of applications, including synthetic biology. Because of their various uses, hydroxyapatites (HAp) from biological entities such as humans, cattle, and pigs are a common application.
X-ray diffraction was used to investigate the crystalline structure of these biologically active materials. XRD is also often used for identifying unknown crystalline substances. These must be determined for geological studies, atmospheric engineering, nanotechnology, and biological research investigations.
Much research has been conducted by professionals all over the world. Ooi et al (2007) demonstrated the presence of the nanocrystalline phase in the X-ray pattern of raw bovine bone. Their findings show that in annealed samples heated to 700 to 1000 °C, there is a significant rise in height and a decrease in width.
Peak widths narrowed, relating to an increase in crystallinity and crystallite size. The influence of the burning method used to create Haps on their structure has been investigated. As the temperature rose, the crystallographic quality followed suit, resulting in a shift from wide to acute peaks in the patterns.
The crystallinity value is a variable used to measure the atomic order into the structure matrix and may be calculated using an order parameter that external and internal causes can influence. When the pattern is defined by the elastomeric component, the crystalline quality (CQ) is a quantity that can only be calculated using the FWHM.
The latest research published in Nature scientific reports focuses on assessing the variation of the size of nanocrystals on the results of XRD patterns from humans and porcine bones.
TEM analysis revealed that polycrystalline nanocrystals with stretched plate shapes were essential and pristine constituents of raw bones. The findings validated the nano-dimensions of unprocessed bone hydroxyapatite, which are straight plate-like structures that might be associated with the bone's well-known transverse and selective growth.
The SEM analysis indicated that as with H-720, HAp crystals achieved diameters in the range of micrometer after the carbonization process at 720°C. Crystals with extended morphologies were found in the B-720 sample, and their borders were connected to those of other crystalline substances. It was proof that the coalescence-based growth mechanism had been disrupted.
A distinctive XRD pattern of a decorticated bovine bone revealed that a pattern is created by the following factors: specimen composition (polycrystalline and unstructured), disturbance (noise), and experimental functionality.
However, it is crucial to demonstrate that the region utilized to define the crystallographic input of a nanocrystal specimen is created by elastic and plastic dispersion and the experimental component, implying that each of these signals cannot be determined individually.
The XRD signals for raw HAps were characterized as polycrystalline specimens with "poor crystallographic integrity," yet the HRTEM pictures show that these samples belong to organized HAp nanocrystals.
Limitations and Challenges
One of the issues with interpreting HAp XRD analysis spectra is the utilization of the FWHM as a metric to assess their crystalline nature. However, direct evaluation of this characteristic in the control sample reveals wide peaks.
BIO-HAp has been claimed to have inadequate crystalline quality based on the FWHM of a distinctive peak, and the crystallinity % is calculated using the whole XRD pattern. However, the large peaks shown in the diffraction patterns are caused by scattering from the BIO-HAp nanocrystals, widening caused by scattering, and experimental impact.
In short, the crystal size determines the form and amplitude of the X-ray diffraction peaks for structured crystalline material. The large peaks of the nano HAP patterns are not always associated with disorderly crystalline formations.
From the standpoint of the future of synthetic biology, these results demonstrated that the combustion procedure might be used to create biocompatible-HAp, though XRD studies must demonstrate that the temperatures did not cause alterations in its nano size.
Continue reading: Developing a Universal Route to Controlled Nanocrystal Synthesis
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Reischig, P., & Ludwig, W. (2020). Three-dimensional reconstruction of intragranular strain and orientation in polycrystals by near-field X-ray diffraction. Current Opinion in Solid State and Materials Science. 24(5). 100851. Available at: https://doi.org/10.1016/j.cossms.2020.100851
Restrepo, S. M., Cruz, R. J., Malo, B. M., Muñoz, E. M., & García, M. E. (2019). Efect of the Nano Crystal Size on the X-ray Difraction Patterns of Biogenic Hydroxyapatite from Human, Bovine, and Porcine Bones. Scientific Reports. 9(1). 5915. Available at: https://doi.org/10.1038/s41598-019-42269-9
Zhang, L., Gonçalves, A. A., & Jaroniec, M. (2020). Identification of preferentially exposed crystal facets by X-ray diffraction. RSC Advances, 5585-5589. 10(1). Available at: https://doi.org/10.1039/d0ra00769b
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