Does anyone know which unit can qualify SEMs? How is it verified?

Institute of Mineral Resources, Chinese Academy of Geological Sciences, can ask you the following questions! And the verification can be carried out for a fee.

What is the accreditation and accreditation of SEM laboratories?

What is the role of SEM laboratory accreditation and accreditation?

Does every SEM lab need to be certified and accredited?

What is the current status of the accreditation and accreditation of SEM laboratories in China?

What are the serious consequences of the lack of SEM certification?

What standard documents are available for SEM laboratory accreditation and accreditation?

What programs (ability to implement standards) can be applied for in the SEM laboratory?

Can a scanning electron microscope measure length?

What are the three basic conditions for SEM length measurement?

Do we have the basic conditions for these three length measurements in our country?

What are the reasons for the failure to carry out SEM length measurement in China?

Why is a length standard the key to length measurement?

Is there a length standard for scanning electron microscopy in China?

What kind of length standards are used for instrument inspection or acceptance SEM?

What are the basic requirements for a length standard for SEM?

What are the common methods and standards for SEM length measurement?

What is the typical SEM length range and uncertainty?

What is the "Scanning Electron Microscope Verification Protocol"?

Should the SEM be self-tested or verified by the metrology department?

According to the verification procedures of SEM, what are the necessary tests for SEM?

What are the key tests in the above tests?

The electron probe has the function of scanning electron microscope, so is there any difference in the verification content of the electron probe?

What is the content of the analysis SEM?

What are the three types of standards that should be prepared for analytical SEM characterization?

What are the standard methods and specifications for the use of electron probes and SEMs?

Scanning electron microscopy (SEM) is generally used to observe the surface morphology of tissue cells.

The SEM I've seen can observe structures such as microvilli, pseudopods, perforations on the surface of dying cells, and maybe something more advanced. Transmission electron microscopy (TEM) can be used to visualize ultrastructures such as organelles inside cells. However, I suspect that if the technique is fine enough to dissect a cell, SEM can also observe the inside of the cell.

How the SEM works:

Scanning electron microscopy (SEM) is a large instrument used to test the surface morphology of a sample. When the incident electron beam with a certain energy bombards the surface of the sample, the electrons have a single or multiple elastic and inelastic collisions with the nucleus and outer electrons of the element, some electrons are reflected out of the surface of the sample, while the rest of the electrons penetrate into the sample, gradually lose their kinetic energy, and finally stop moving, and are absorbed by the sample.

During this process, more than 99% of the incident electron energy is converted into sample heat, while the remaining about 1% of the incident electron energy excites various signals from the sample. These signals mainly include secondary electrons, backscattered electrons, absorption electrons, transmitted electrons, Auger electrons, electron electromotive force, cathodoluminescence, X-rays, etc. It is from these signals that the SEM device obtains information and analyzes the sample.

SEM samples are required to have morphology, high vacuum resistance, no organic oil contaminants on the sample surface, dry samples, conductive sample surfaces, etc.

1. Morphology and morphology should be resistant to high vacuum.

Scanning electron microscopy (SEM) uses an electron beam to scan the surface of an object. The presence of air will deform the electron beam and affect the scanning effect, so the measured sample can withstand high vacuum.

2. The surface of the sample should not contain organic oil contaminants.

Oil pollution is easy to decompose into hydrocarbons under the action of electron beam, which causes great pollution to the vacuum environment. Sample surface details are obscured by hydrocarbons; Hydrocarbons reduce imaging signal yield; The adsorption of hydrocarbons in the electron beam light path causes large astigmatism; Hydrocarbons are adsorbed on the surface of the detector crystal, reducing detector efficiency. Severe interference with electron beams with low accelerating voltages.

3. The sample should be dry.

Water vapor will accelerate the volatilization of the cathode material of the electron gun, which will greatly reduce the filament life. Water vapor scatters the electron beam, increasing the energy dispersion of the electron beam, thereby increasing the large color difference and reducing the resolving power.

4. The surface of the sample can be conducted, blinded, and electrified.

The surface of the sample should be electrically conductive, and if not, it should be plated with gold to increase conductivity. In most cases, the number of primary electron beam charges is greater than the sum of the number of backscattered electrons and secondary electrons, so the excess electrons are channeled into the ground, i.e., the sample surface potential is kept at 0.

Preliminary processing of samples:

1. Materials. In terms of SEM, the sample can be slightly larger, with an area of up to 8 mm and a thickness of up to 5 mm. For samples that are easily curled by SEM, such as blood vessels and gastrointestinal mucosa, they can be fixed on filter paper or card stock to fully expose the surface of the tissue to be observed.

2. Cleaning of samples.

The site that is viewed with SEM is often the surface of the sample, i.e., the free surface of the tissue. Since the sample is taken from living tissue, there is often blood, tissue fluid, or mucus attached to the surface, which can obscure the surface structure of the sample and interfere with observation. Therefore, these attachments should be cleaned before the sample is fixed.

3. Fixed. The reagents used for fixation are the same as those for TEM sample preparation, and glutaraldehyde and osmium acid double fixation are commonly used. Due to the large sample volume, the fixation time should be appropriately extended. It can also be fixed with flash freezing.

4. Dehydration. After rinsing, the sample is dehydrated with a progressively higher concentration of alcohol or acetone, and then enters an intermediate solution, generally with isoamyl acetate as the intermediate solution.

Brand model: SFMIT scanning electron microscope.

System: DSF-60

Scanning electron microscopy (SEM) is used to measure the material properties of materials on the surface of a sample for microscopic imaging.

Scanning electron microscopy (SEM) is an observation technique that sits somewhere between a transmission electron microscope and an optical microscope. It uses a focused narrow high-energy electron beam to scan the sample, and through the interaction between the beam and the substance, various physical information is excited, and the information is collected, amplified, and re-imaged to achieve the purpose of microscopic morphology characterization of the substance.

The resolution of the new scanning electron microscope can reach 1 nm; The magnification can reach 300,000 times and above and can be continuously adjusted; And the depth of field is large, the field of view is large, and the imaging stereo effect is good.

In addition, the combination of scanning electron microscope and other analytical instruments can be used to observe the microscopic morphology and analyze the microstructure of the material at the same time. Scanning electron microscopy is widely used in the study of geotechnical, graphite, ceramics and nanomaterials. Therefore, scanning electron microscopy plays a significant role in the field of scientific research.

Requirements: 1. The sample must be a Guxun hungry body, and be non-toxic and non-radioactive.

2. The sample can be lumpy, flake, fibrous, granular or powdery, no matter what kind of sample can not be residual organic volatiles and contain water, the sample containing water can make the image blurry, or even not imaging at all, and can also cause contamination of the lens tube, therefore, the water in the sample should be dried first.

3. Whether it is a bulk sample or a powder granular sample, its chemical and physical properties should be stable, and it must be able to keep the composition stable and the shape unchanged under the irradiation of electron beam in high vacuum.

4. On the premise of not damaging the surface structure of the sample, the sample surface structure should be properly cleaned and dried.

Mega Nai Requirements:

1. The sample must be solid, non-toxic and non-radioactive.

2. The sample can be lumpy, flaked, fibrous, granular or powdery, no matter what kind of sample digging can not be organic volatiles and containing water, the sample containing water can make the image blurry in the lens tube, and even can not be imaged at all, it can also cause the lens tube pollution, therefore, the water in the sample should be dried first.

3. Whether it is a bulk sample or a powdered granular sample, its chemical and physical properties should be stable, and the composition should be stable and the morphology should remain unchanged under the irradiation of the electron beam in a high vacuum.

4. Samples with contaminated surfaces should be properly cleaned and dried without damaging the surface structure of the samples.