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    Home > Coatings News > Paints and Coatings Market > The particle size test method of nanomaterials is complete

    The particle size test method of nanomaterials is complete

    • Last Update: 2020-11-20
    • Source: Internet
    • Author: User
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    Nanomaterials refer to materials of a special nature consisting of nanostructure units in which at least one dimension of three-dimensional space size is at least one dimension (1 to 100 nm), and is known as "one of the most important strategic high-tech materials of the 21st century". When the particle size of the material reaches the nanoscale, it will have many characteristics such as small size effect, quantum size effect and surface effect that are not available in traditional micron scale material, which will provide a new way of thinking for the development and application of new materials.
    , nanomaterials have become the most basic component of material research and development and industrialization, of which the granularity of nanomaterials is one of its most important characteristic parameters

    . Based on different test principles, this paper expounds the particle size test methods of 8 nanomaterials, and analyzes the advantages and disadvantages of different particle size test methods and the scope of application.
    1. Electron microscopy
    electron microscopy is the most commonly used method for the study of nanomaterial size, shape, surface structure and chemical composition of micro-regions, generally including scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For very small particle sizes, especially clusters consisting of only a few atoms, measurements are made using scanning tunnel mirrors. The particle size measured by the calculated electron mirror mainly uses the cross method, the maximum cross-length mean method, the particle size distribution method and so on.
    :
    method is an absolute method of particle degree observation, so it is reliable and intuitive.
    disadvantages:
    measurements lack overall statistics, ultrasonic dispersion must be done before the sample is dripped, and accurate results are difficult to obtain for nanoparticle samples that are not resistant to strong electron beam bombardment.
    2. Laser particle size analysis
    Laser particle size analysis is based on Fraunhofer diffraction and Mie scattering theory, according to the laser exposure to particles, particles can make the laser diffraction or scattering phenomenon to test the particle size distribution. Therefore, the corresponding laser particle size analyzer is divided into laser diffraction type and laser dynamic scattering type. The general diffraction particle size meter is suitable for the analysis of samples with a particle size of more than 5 m, while the dynamic laser scattering instrument is more accurate for the analysis of nano and sub-micron particle samples with a particle size of less than 5 m. Therefore, the measurement of nanoparticles generally uses dynamic laser scattering instrument.
    advantages:
    sample dosing, high degree of automation, good repeatability, can be analyzed online.
    disadvantages:
    can not analyze the high concentration of particle size and particle size distribution, the analysis process needs to be diluted, resulting in some errors.
    3. Dynamic light scattering
    Dynamic light scattering, also known as photon-related spectra, is the average particle size and particle size distribution of a sample by measuring the fluctuations in the intensity of the scattered light of the sample. Nanoparticles in liquids are dominated by Brown motion, which depends on factors such as particle size, temperature and viscosity coefficient. Under constant temperature and viscosity conditions, particle diffusion coefficient can be obtained by photon-related spectrometration, which is suitable for the detection of particle size of industrial products, and the measurement of suspensions with particle size ranges of 1nm to 5 m.of the nuclear shell particle size growth rate chart drawn by dynamic light scattering method
    advantages:
    fast particle size, accurate particle size distribution is obtained.
    :
    results are influenced by the particle size and distribution of the sample, and are only suitable for measuring particle samples with narrow particle size distribution;
    4.X-ray diffraction wide (XRD)
    XRD measures the size of nanomaterial grains on the principle that when the size of the material grain is nanoscale, its diffraction peak type is correspondingly wide, through the measurement of the wide peak type and the use of the Scherrer formula to calculate the grain size of different wafers. For specific grains, the product of diffraction hkl's face spacing dhkl and crystal surface number N is the grain size Dhkl perpendicular to this wafer direction. The grain size in the sample can be calculated using the Scherrer formula:
    : x-ray wavelength;
    of the crystalline structure of the material by X-ray diffraction (XRD):
    can
    for the identification of unknowns.
    disadvantages:
    sensitivity is low, the accuracy of quantitative analysis is not high, the measured grain size does not determine whether there is a close reunion between the grains, and it is important to note that there can be no microscopic stress in the sample.
    5.X-ray small-angle scattering (SAXS)
    When X-rays are shining on a material, scattering X-rays occur within a small angle range of 2 to 5 degrees around the incoming X-ray beam if there is a nanoscale density uneven area inside the material. When the grain size of the material is finer, the center scattering becomes more diffuse, and this behavior is independent of the inner structure of the grain of the material. The SAXS method calculates the particle size distribution of the material by measuring the scattering map of the center. SAXS can be used for the determination of the size distribution of various metals, inorganic non-metallic, organic polymer powders and particle size distributions such as biomolecules, collosal solutions and magnetic liquids at the nanoscale scale, as well as for the analysis and study of nanoscale holes, partialization zones, and the equivalent size of the analysis and development of various materials.
    advantages of microfocus X-ray small-angle scattering microclysis imaging principle schematic:
    is simple to operate, and for spherical powders of a single material, this method has good accuracy in measuring particle size.
    disadvantages:
    does not effectively distinguish scattering from particles or micro pores, and for dense scattering systems, the interference effect between particle scattering occurs, resulting in low measurement results.
    6.X-ray photoelectronic energy spectrum (XPS)
    XPS method using X-ray as the excitation source, based on the nanomaterial surface excited electrons have characteristic energy distribution (energy spectrum) and analysis of its surface elements, also known as chemical analysis of photoelectronic energy spectrum (ESCA). Since the binding energy of an atom in a particular orbit depends on the chemical environment around the atom, the fingerprint characteristics of the X-ray photoelectronic energy map can be used for qualitative and semi-quantitative analysis of various elements except hydrogen and helium.advantages of XPS spectroscopy
    for graphene-type porous carbon nanoplate samples:
    is absolutely sensitive and requires very little sample size for analysis.
    disadvantages:
    relative sensitivity is not high, and the analysis of liquid samples is difficult;
    7. Scan probe microscope (SPM)
    SPM method is the use of measuring the probe and sample surface interaction generated by the signal, at the nano-scale or atomic level to study the geometry of atoms and molecules on the surface of a substance and related physical and chemical properties of the analysis technology, especially the atomic force microscope (AFM), which can not only directly observe the appearance and structure of the nanomaterial surface, but also the surface of the matter can be controlled local processing.AFM image of graphene oxide
    advantages:
    is unique in nanomaterial measurement and characteristics.
    :
    lack of implementation in practice due to the lack of standard substances.
    8. Raman spectroscopy is
    method for low-dimensional nanomaterials under the Raman spectroscopy. It is based on the Raman effect of inelastic light scattering analysis technology, is an inelastic scattering spectrum produced by the interaction of photons exciting light with the lattice vibration of the material, which can be used for fingerprint analysis of the material. Raman frequency shift is related to the rotation and vibration energy level of material molecules, and different substances produce different Raman frequency shift. Raman frequency characteristics provide valuable structural information. Using Raman spectroscopy, molecular structure, key-state characteristic analysis, measurement of grain average particle size and so on can be carried out on nanomaterials.the in-place Raman spectrogram of the ORR process on the surface of the monocrystalline electrode:
    high sensitivity,
    non-destructive samples, convenient and fast.
    disadvantages:
    different vibration peak overlap and Raman scattering intensity are easily affected by optical system parameters and other factors;
    test methods of
    nanomaterial granularity are different, but the measurement principles corresponding to different test methods are different, so there can be no horizontal comparison between different test methods. Different particle size analysis methods have a certain scope of application and corresponding sample processing methods, so in the actual test should take into account the characteristics of nanomaterials, measurement purposes, economic costs and other aspects
    factors, to determine the final choice of test methods.
    This article is an English version of an article which is originally in the Chinese language on echemi.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to service@echemi.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

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