High-melting-point graphite tube for elemental analysis

Abstract

The utility model provides a high-melting-point graphite pipe for elemental analysis, which belongs to the technical field of spectral analysis and comprises a circular hollow graphite pipe main body and transverse support parts symmetrically arranged on two sides of the graphite pipe main body, an inner pyrolytic carbon layer is deposited on the inner wall of the graphite pipe, a porous structure is arranged in the inner pyrolytic carbon layer, and an outer compact pyrolytic carbon layer is further deposited on the surface of the inner pyrolytic carbon layer. Through the inner pyrolytic carbon layer and the outer compact pyrolytic carbon layer, in the high-temperature working process, the inner wall pyrolytic carbon layer can be selectively consumed to form a compact glassy carbon film, a self-adaptive protection mechanism enables the graphite tube to still keep stable analysis performance under extreme conditions, reaction or permeation of a detected element and graphite at high temperature is reduced, and the analysis accuracy of the graphite tube is improved. The phenomenon of cross contamination is reduced, the memory effect of the graphite pipe is reduced by 70%, but the memory effect of a traditional pyrolytic graphite pipe can only be reduced by 30-40%, and the graphite pipe is particularly suitable for analysis of high-melting-point elements.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of spectral analysis technology, especially relates to a graphite tube for high melting point element analysis. BACKGROUND

[0002] As the core component of atomic absorption spectrometer, the working principle of graphite tube is based on atomic absorption spectrometry. When the light of specific wavelength emitted by the light source (such as hollow cathode lamp) passes through the atomic vapor in the graphite tube, the electrons in the atom will absorb the energy of the photon, and jump from the ground state to the excited state. According to Lambert-Beer's law, the absorbance is proportional to the atomic concentration, so the concentration of elements in the sample can be determined by measuring the absorbance.

[0003] The graphite tube for spectral analysis has very high requirements on material performance and is made of high-purity graphite material. The high-temperature resistance of the graphite tube is one of its core characteristics. High-purity graphite can withstand extreme temperatures up to 3000℃ in inert gas or vacuum environment. In practical application, the high-temperature resistance of the graphite tube is affected by the following factors: material purity: high-purity graphite (purity ≥ 99.9%) has higher thermal stability and oxidation resistance, and can maintain structural integrity at high temperature. Environmental atmosphere: graphite shows excellent high-temperature resistance in inert gas (such as argon, nitrogen) or vacuum environment, and can be used at 2500-3000℃ for a long time.

[0004] However, the existing graphite tube has the most common problem: when analyzing high melting point elements through the graphite tube, the graphite tube has memory effect, and there is cross contamination between the elements measured in real time and the elements measured in advance. INVENTION CONTENTS

[0005] Therefore, the utility model provides a graphite tube for high melting point element analysis to solve the technical problem that the graphite tube has memory effect when analyzing high melting point elements through the graphite tube, and there is cross contamination between the elements measured in real time and the elements measured in advance in the prior art.

[0006] The technical solution of the utility model to solve the above technical problem is as follows:

[0007] A graphite tube for high melting point element analysis, comprising a circular hollow graphite tube body, and a transverse support part symmetrically arranged on both sides of the graphite tube body; an inner layer of pyrolytic carbon layer is deposited on the inner wall of the graphite tube, the inner layer of pyrolytic carbon layer has a porous structure, and an outer layer of dense pyrolytic carbon layer is further deposited on the surface of the inner layer of pyrolytic carbon layer.

[0008] Preferably, the porous structure comprises first holes distributed axially along the graphite tube body, and second holes distributed radially along the graphite tube body, the first holes and the second holes are interconnected to form a mutually interlaced grid structure.

[0009] Preferably, the porous structure is irregular polygon.

[0010] Preferably, the inner layer pyrolytic carbon layer has a thickness of 20-30 μm.

[0011] Preferably, the outer layer dense pyrolytic carbon layer has a thickness of 20-30 μm.

[0012] Preferably, the graphite tube body outer surface is further coated with a graphite antioxidant with a thickness of 5-20 μm.

[0013] Preferably, the graphite tube body inner wall is provided with two raised circular arcs on both sides.

[0014] Preferably, the lateral support part comprises a current transition part and an electrode contact part, the current transition part is connected with the graphite tube body, and the electrode contact part is connected with the current transition part.

[0015] Preferably, the electrode contact part is provided with a light measuring hole, and the light measuring hole is in communication with the graphite tube body inner cavity.

[0016] Preferably, the graphite tube body is provided with a sample inlet hole.

[0017] Compared with the prior art, the graphite tube for high melting point element analysis has at least the following advantages:

[0018] 1. In the high temperature working process, the inner wall pyrolytic carbon layer selectively consumes to form a dense glassy carbon film, the self-adaptive protection mechanism enables the graphite tube to maintain stable analysis performance under extreme conditions, reduces the reaction or penetration of the measured elements with graphite under high temperature, reduces the cross contamination phenomenon, and reduces the memory effect of the graphite tube by 70%, while the traditional pyrolytic graphite tube can only reduce by 30-40%, and is particularly suitable for analysis of high melting point elements.

[0019] 2. The porous structure of the inner layer pyrolytic carbon layer can effectively hinder crack propagation, deflect and branch the cracks in the porous layer, the porous structure is also beneficial to the diffusion of reaction gas, the dense layer is deposited more uniformly, and the porous structure can reduce the overall density of the inner layer pyrolytic carbon layer to realize lightweight.

[0020] 3. The inner layer pyrolytic carbon layer with the porous structure is combined with the graphite tube body inner wall, and the outer layer dense pyrolytic carbon layer is deposited, which can effectively solve the peeling phenomenon of single coating. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 It is a graphite tube for high melting point element analysis.

[0022] Figure 2It is a high melting point element analysis with a view of the graphite tube.

[0023] Figure 3 It is a high melting point element analysis with a view of the graphite tube.

[0024] Figure 4 It is Figure 3 A-A half sectional view of.

[0025] Figure 5 It is Figure 4 C in the partial enlarged view.

[0026] Figure 6 It is a high melting point element analysis with a view of the graphite tube.

[0027] Figure 7 It is Figure 6 B-B half sectional view of.

[0028] Figure 8 It is Figure 7 D in the partial enlarged view.

[0029] In the figure: graphite tube body 100, inner layer pyrolytic carbon layer 110, first hole 111, second hole 112, outer layer dense pyrolytic carbon layer 120, RLHY-305 graphite antioxidant 130, raised arc 140, sample hole 150, transverse support part 200, current transition part 210, electrode contact part 220, light measurement hole 221. DETAILED DESCRIPTION

[0030] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The technical solutions of the present application will be further described below in combination with the drawings of the embodiments of the present application. The present application is not limited to the following specific embodiments.

[0031] It should be understood that the same or similar reference numerals in the drawings of the embodiments correspond to the same or similar parts. In the description of the present application, it should be understood that if the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom" and the like indicate the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the positional relationship in the drawings are only used for exemplary illustration, and cannot be understood as a limitation of the present patent, for those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0032] As the core component of atomic absorption spectrometer, the graphite tube has the advantages of uniform temperature distribution, larger constant temperature area and smaller temperature gradient, and is widely used. For example, the utility model with the patent number CN201520107788.6 provides an atomic absorption transverse graphite tube, which discloses the main structural features of the existing transverse graphite tube. However, when the existing atomic absorption transverse graphite tube is used to analyze high melting point elements, the graphite tube has memory effect, and there is cross contamination between the elements determined in real time and the elements determined in advance.

[0033] Therefore, a graphite tube for high melting point element analysis is proposed to solve the problems of the existing transverse graphite tube. Please refer to Figures 1 to 7 A graphite tube for high melting point element analysis includes a circular hollow graphite tube body 100 and transverse support parts 200 symmetrically arranged on both sides of the graphite tube body 100. An inner layer pyrolytic carbon layer 110 is deposited on the inner wall of the graphite tube, the inner layer pyrolytic carbon layer 110 has a porous structure, and an outer layer dense pyrolytic carbon layer 120 is further deposited on the surface of the inner layer pyrolytic carbon layer 110.

[0034] After the graphite tube body 100 and the transverse support parts 200 are integrally pressed and formed, the inner layer pyrolytic carbon layer 110 is formed, and then the graphite tube body is placed into a reaction furnace again. The furnace temperature is raised to 980℃, propylene / nitrogen mixed gas with a volume ratio of 1:3 is introduced, the pressure is 1.2kPa, and the time is 30 hours. At the relatively high temperature of 980℃, propylene (C3H6) molecules will undergo pyrolysis reaction to generate active carbon species. The cracking process of propylene is carried out in steps. First, the C-H bond is broken to form a propylene radical, and then the C-C bond is broken to generate smaller CH3, C2H2 and other fragments. These active fragments adsorb, migrate and deposit on the surface of the substrate to form a carbon layer. Nitrogen as a diluent gas reduces the concentration of active carbon species and slows down the deposition rate. The propylene / nitrogen ratio (1:3) determines the carbon source concentration. The lower the ratio, the slower the deposition rate and the higher the porosity. The relatively low pressure of 1.2kPa reduces the gas molecule collision frequency, so that the deposition process is controlled by surface reaction, forming a more loose structure. The temperature of 980℃ balances the carbon deposition rate and gas diffusion rate. If the temperature is too high, the structure will be densified. Therefore, by raising the furnace temperature to 980℃, introducing propylene / nitrogen mixed gas with a volume ratio of 1:3, the pressure is 1.2kPa, and the time is 30 hours, it is beneficial to form a loose and porous structure.

[0035] The outer layer of dense pyrolytic carbon layer 120 is formed by heating to 1030°C, switching to a propane / methane / nitrogen mixed gas with a volume ratio of 1:5:15, a pressure of 1.8 kPa, and a time of 50 hours. The furnace temperature of 1030°C promotes methane cracking and increases deposition density. The propane / methane / nitrogen ratio of 1:5:15 provides a higher active carbon source from propane and promotes dense deposition from methane. The higher pressure of 1.8 kPa increases gas phase molecular collisions, improving deposition uniformity. The time of 50 hours ensures sufficient thickness and complete densification. This in turn facilitates the formation of the outer layer of dense pyrolytic carbon layer 120.

[0036] Through the inner layer of pyrolytic carbon layer 110 and the outer layer of dense pyrolytic carbon layer 120, during high-temperature operation, the inner wall pyrolytic carbon layer selectively consumes to form a dense glassy carbon film, a self-adaptive protection mechanism enables the graphite tube to maintain stable analysis performance under extreme conditions, reduces the reaction or penetration of the measured elements with graphite at high temperatures, reduces the cross-contamination phenomenon, and reduces the memory effect of the graphite tube by 70%, while traditional pyrolytic graphite tubes can only reduce by 30-40%, especially suitable for the analysis of high-melting-point elements. In addition, the porous structure of the inner layer of pyrolytic carbon layer 110 can effectively hinder crack propagation, causing cracks to deflect and branch in the porous layer. The porous structure also facilitates the diffusion of reaction gases, making the dense layer deposition more uniform. The porous structure can reduce the overall density of the inner layer of pyrolytic carbon layer 110, achieving lightweight. Furthermore, the combination of the porous structure of the inner layer of pyrolytic carbon layer 110 with the inner wall of the graphite tube body 100 and the subsequent deposition of the outer layer of dense pyrolytic carbon layer 120 can effectively solve the peeling problem of single coating.

[0037] In a preferred embodiment, referring to Figures 3 to 8 (Note: Due to the extremely small size of the porous structure, which is measured in microns, the partial method diagram in the figure is for illustrative purposes only and is not the actual pore structure), the porous structure includes first pores 111 distributed axially along the graphite tube body 100 and second pores 112 distributed radially along the graphite tube body 100, the first pores 111 and the second pores 112 are interconnected to form a mutually interlaced grid structure. Through the forming process, the inner layer of pyrolytic carbon layer 110 has first pores 111 distributed axially and second pores 112 distributed radially, forming a mutually interlaced grid structure that can absorb the stress generated by thermal mismatch at the interface and effectively hinder crack propagation.

[0038] In a preferred embodiment, the porous structure is irregularly polygonal.

[0039] In a preferred embodiment, the inner pyrolytic carbon layer 110 has a thickness of 20-30 μm. The outer dense pyrolytic carbon layer 120 has a thickness of 20-30 μm. The total thickness of the inner pyrolytic carbon layer 110 and the outer dense pyrolytic carbon layer 120 is between 40-60 μm. The thinner thickness is more advantageous for high melting point element analysis.

[0040] In a preferred embodiment, in order to improve the oxidation resistance of the graphite tube body 100, the outer surface of the graphite tube body 100 is further coated with an RLHY-305 graphite antioxidant 130, and the coating thickness is 5-20 μm. The oxidation resistance of the graphite tube body 100 is improved by the RLHY-305 graphite antioxidant 130.

[0041] In a preferred embodiment, referring to Figure 1 , two raised circular arcs 140 are arranged on both sides of the inner wall of the graphite tube body 100. In the process of atomizing the liquid to be detected, the liquid is prevented from flowing outside the graphite tube, thereby playing a blocking role.

[0042] In a possible embodiment, referring to Figure 1 , the lateral support part 200 includes a current transition part 210 and an electrode contact part 220. The current transition part 210 is connected with the graphite tube body 100, and the electrode contact part 220 is connected with the current transition part 210. The current transition part 210 is symmetrically arranged on both sides of the graphite tube body 100, so as to ensure that the current is uniformly distributed when the current flows through the graphite tube body 100. The electrode contact part 220 is symmetrically arranged on both sides of the current transition part 210, and one end is a positive electrode and the other end is a negative electrode.

[0043] In a preferred embodiment, the electrode contact part 220 is provided with a light measuring hole 221, and the light measuring hole 221 is in communication with the inner cavity of the graphite tube body 100. The light measuring hole 221 helps to improve the analysis sensitivity and realize uniform temperature distribution of the graphite tube.

[0044] In a preferred embodiment, the graphite tube body 100 is provided with a sample inlet hole 150.

[0045] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A graphite tube for high-melting-point element analysis, characterized in that, The graphite tube body comprises a circular hollow graphite tube body and lateral support parts symmetrically arranged on both sides of the graphite tube body. An inner layer of pyrolytic carbon is deposited on the inner wall of the graphite tube body, and the inner layer of pyrolytic carbon has a porous structure and an outer layer of dense pyrolytic carbon is deposited on the surface of the inner layer of pyrolytic carbon.

2. A graphite tube for high-melting-point elemental analysis according to claim 1, characterized in that, The porous structure comprises first pores distributed along the axial direction of the graphite tube body and second pores distributed along the radial direction of the graphite tube body, and the first pores and the second pores are interconnected to form a mesh structure.

3. A graphite tube for high-melting-point elemental analysis according to claim 2, characterized in that, The porous structure is irregular polygonal.

4. A graphite tube for high-melting-point elemental analysis according to claim 1, characterized in that, The thickness of the inner layer of pyrolytic carbon is 20-30 μm.

5. A graphite tube for high-melting-point element analysis according to claim 1, wherein The thickness of the outer layer of dense pyrolytic carbon is 20-30 μm.

6. A graphite tube for high-melting-point element analysis according to claim 1, wherein The outer surface of the graphite tube body is coated with a graphite antioxidant layer with a thickness of 5-20 μm.

7. A graphite tube for high-melting-point element analysis according to claim 1, wherein Two raised circular arcs are arranged on both sides of the inner wall of the graphite tube body.

8. A graphite tube for high-melting-point elemental analysis as claimed in claim 1, characterized by The lateral support part comprises a current transition part and an electrode contact part, the current transition part is connected with the graphite tube body, and the electrode contact part is connected with the current transition part.

9. A graphite tube for high-melting-point element analysis according to claim 8, characterized in that, A light measuring hole is arranged in the electrode contact part, and the light measuring hole is in communication with the inner cavity of the graphite tube body.

10. A graphite tube for high-melting-point elemental analysis as claimed in claim 1, characterized by A sample inlet hole is arranged on the graphite tube body.

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