The method of preparation of samples for transmission electron microscopy of electrically conductive materials and device for its implementation
The invention relates to the field of electron-microscopic studies of the real microstructure of solids and can be used for making objects from electrically conductive materials for transmission electron microscopy (TEM). In the invention on one surface of the specimen immersed in the electrolyte acts adjustable frequency and amplitude of the pulsating jet of electrolyte. Pulsating jet of electrolyte affects the sample immersed in the electrolyte. The control process is finished thinning provide electrical contact with the circuit through the drop chemically inert elektroprovoda liquid electrical circuit to sample the signal electrode on the occurrence of pinholes in tanaami sample areas. The electrochemical cell contains a U-shaped channel, one end of which is connected through a polymer tube with an air pulsator and the other containing the nozzle and connected with the total volume of the cell is set objectoperation with the sample and the signal electrode. The invention improves the efficiency of the method of electrochemical thinning of the samples and the quality of the EMP object, but also simplifies the design of the device for Pro-microscopic studies of the real microstructure of solids and can be used for making objects from electrically conductive materials for transmission electron microscopy (TEM).For TEM studies required objects in the thickness of not more than 0.15 μm. Because the original sample thickness is much greater (at least up to 1 mm), requires a particular method of thinning to the desired thickness. Basically apply a two-step process of thinning. At the first stage typically use mechanical thinning to achieve a thickness of not more than 0.4 mm, Then, in the second stage, mainly used electrochemical thinning. It is at the last stage conditions bezdetonatsionnoy thinning with getting the mirror surface of the sample. The thinning is carried out before the appearance tanaami the field of micro-holes, near which the thickness of the sample is usually complies with the requirement of the passage through it of electrons with an energy of 100-200 Kev (i.e., not more than 0.15 μm) (PAM-objects).Recently, widespread use has been the so-called method of "jet" electrochemical thinning. It is based on a continuous effect on utheemu part of the sample stream of the electrolyte. The main advantage of the "jet" method is obtaining a self-supporting thin foil, suitable for TEM studies. Control achieve acceptable for TEM studies sample thickness (PAM-object) is done according to claim who I am through the hole in the TEM-object light from the source to the receiver.It is described above the principles of preparation of the EMP objects from electrically conductive materials form the basis of commercially available firm "Struers" (Denmark) device "Tenupol-3", taken as a prototype ("Practical methods in electron microscopy"./Edited by Audrey M. Glora, Leningrad, mechanical engineering, 1980). It is based on a continuous effect on the two surfaces of the sample located outside the volume of the electrolyte, two jets of electrolyte and the optical principle of the control process is finished thinning.The main disadvantages of the method of thinning and device for its implementation.The continuous action of the jet of electrolyte on the sample located in the air, form a conical recess. However, more than the original thickness of the sample, the smaller the area of the thinned plot, suitable for TEM studies. Therefore, in the device "Tenupol-3" the original thickness of the sample is limited to the value of 0.4 mm. If the original thickness of the sample is larger, then reservation is its mechanical and chemical thinning to 0.4 mmMethod of forming a continuous flow of electrolyte requires a large number (up to 1 litre). Such a large volume of electrolyte makes it difficult to maintain given system, in contact with the electrolyte, when changing the electrolyte, require a large number of necessary reagents, deteriorating security conditions when working with toxic electrolytes, radioactive materials, with the disposal of waste electrolytes.The optical system control process is finished thinning requires an infrared light source (to reduce background from extraneous light sources), chemical resistant filters, eliminates the use of more efficient opaque electrolytes, complicates the device.The purpose of the invention is to increase the efficiency of the method of electrochemical thinning of the images and the quality of the EMP object, and also to simplify the design of the device for its implementation.This objective is achieved in that on one of the surfaces of the sample immersed in the electrolyte acts adjustable frequency and amplitude of the pulsating jet of electrolyte. The formation of a pulsating jet of electrolyte through the air pulsator comes from a small amount directly into the electrochemical cell and without circulation of the electrolyte outside its scope. The control process is finished thinning exercise of electromontaj and "sample-signal electrode" according to the occurrence of pinholes in tanaami sample areas.The proposed principle of the pulsating jet of electrolyte on the sample immersed in the electrolyte, provides a combination of the two electrochemical processes. In the absence of flow, the sample becomes thinner in the abs static method anodic dissolution, which forms a convex shape alonaemig area due to edge effects increase the electric field at the edges of the sample. In the dynamic conditions of action of the jet, on the contrary, utonomy plot becomes concave (conical) shape of the recess.It stated the principle of periodic action of these successive processes are immersed in the electrolyte sample provides, according to the method, the necessary conditions for obtaining tilkobling deepening in the sample regardless of its original thickness and modes of electrochemical process, and consequently, large areas of the object, suitable for TEM studies. At the same time, it eliminates the need for preliminary mechanical thinning of the samples.The formation of a pulsating jet of electrolyte due to its retraction and ejection in a U-shaped channel electrochemical cell using a remotely located common (membrane) vozdushnye within the volume of the electrochemical cell. This saves chemicals, safe working conditions with toxic electrolytes and highly radioactive samples, and environmentally acceptable disposal of waste electrolytes. Moreover, the minimum amount of electrolyte used provides an economical conditions of forced heating or cooling, particularly liquid nitrogen.Electric contact method of controlling the end of the process of preparation of the EMP object is very simple to implement, has high sensitivity, is not dependent on the optical transparency of the electrolyte and the presence of extraneous light sources. The high sensitivity of the proposed method of control via not circuit circuit pattern-signal electrode" microvolume electrolyte penetrating transferred in the sample (this requires some time for filling the electrolyte microvolume between the sample and the signal electrode), and the faster diffusionin the process of changing the conductivity drops elektroprovoda chemically inert liquid (for example, glycerin) between the sample and the signal electrode.A comparison of the proposed physical and technical solutions with the prototype for the x solutions in the art signs distinguishing the claimed invention from the prototype could not be identified because they provide the claimed technical solution according to the criterion of "significant differences".An example of the method.In Fig. 1 shows the design of the device for implementing the proposed method of preparation of the EMP objects from electrically conductive materials.The device consists of objectattributes, electrochemical cell with camera cooler and electronic unit including an adjustable DC voltage source, time relay, a source of regulated power for the dosage of liquid nitrogen and air pulsator with adjustable pulse frequency.Objectoperation consists of a Teflon block (1) which is pressed stainless tube-anode (2). Inside the anode tube (2) posted by moving the signal electrode (3) is electrically isolated from the anode of the tube (2) Teflon tube (4). The sample (5) is placed in a special washer (6). The sample (5) in the plate (6) is tightly pressed to the anode of the tube (2) acorn nut (7). The microvolume between the sample (5) and a signal electrode (3) is filled with a drop of chemically inert elektroprovoda fluid (8), for example, glycerin.E(9) with an air pulsator, remotely located in the power supply. At the other end of the U-shaped channel with a nozzle (10) install objectoperation. The volume of this channel through holes communicated with the total volume of the electrochemical cell. In the amount of U-shaped channel entered electrode-cathode (11), the material may vary. The adjustment of the amplitude of the jet of electrolyte is carried out by moving the screw (12).The working volume of the electrochemical cell filled with electrolyte (13), is separated from the camera forced cooling/heating of the electrolyte chemically resistant and heat-conducting separating diaphragm of stainless plate (14). The camera cooler can join the systems running cold water, thermostat or the dosing of liquid nitrogen. In the process of preparation of the EMP object due to the ripple level of a small amount of electrolyte in the cell provided an effective and economical conditions of cooling.The device operates as follows.At the end of the anode tube (2) forming a drop of chemically inert and elektroprovoda fluid (8). The sample (5) install the washer (6) and sealed on the anode tube (2) with nut (7). To the anode of the tube (2) and signals the required quantity of the required electrolyte (14) to a level providing the immersion of the sample (5) objectdelete (1). Using the polymer tube (9) connect the remotely located air pulsator in the power supply with the corresponding end of the U-shaped channel in the electrochemical cell. To the cathode electrode (11) connect the appropriate wire from the power supply. Include the power supply. Adjusting the pulse rate of the jet of electrolyte, changing the voltage at the engine air pulsator and its amplitude by using the adjusting screw (12), visually set these parameters jets of electrolyte. As needed to the camera cooler plug in the appropriate cooling system and achieve the required temperature of the electrolyte in the cell. On the power supply is set to the desired value of the voltage on the electrodes of the anode and cathode. Set objectoperation with the sample in the electrochemical cell and control the start and course of the process according to the reading of the milliammeter on the power supply. Since the inventive device generates a single stream of electrolyte, first, the process of electrolytic thinning is subjected to one of the surfaces of the sample for some time (usually not more than 1/5 of the total time required for OK is that automatically stops the thinning process after a specified period of time. Note that this pre-thinning one of the surfaces of the sample, allows for a controlled prepare required for TEM analysis, the layer thickness of the studied sample. After this stage, the sample is turned in the washer on the other side and the thinning process continues until the formation in tanaami region of the sample recipient sites. This is controlled by a signal electrode, through which the corresponding system automatically turns off the power to the anode and the cathode and the engine of the pulsator. PAM-the object is extracted from objecttitle, washed and dried.In Fig.2A (General view) and 2b (cross-section) shows an example of thinned by the proposed method PAM object of plates of bronze Brng a thickness of 1 mm can be Seen that even with such a large initial thickness of the sample, without prior thinning, is formed trelkovsky (flat bottom) profile thinning that guarantees the quality of the EMP object.This method completely eliminates the time-consuming process of chemical and mechanical pre-thinning of the samples with the original thickness of more than 0.4 mm, used in the prototype, because the use of immersed in e is in the sample in terms of the mirror electropolishing machined surfaces regardless of the original thickness of the sample.A small amount of electrolyte (50 ml), poured into the electrochemical cell: - contributes to its efficient and cost-effective forced cooling, especially liquid nitrogen, - allows the economical use of expensive chemical reagents, provides the security of working with toxic electrolytes and highly radioactive samples (easy to provide biological protection, secure storage in a protective safes used electrolyte, simple decontamination only cell volume), - ensures compliance with environmental requirements for disposal and recycling - effectively to experiment with the search electrolyte composition most appropriate to achieve the highest quality of the EMP object.Simple contact principle control end of the process of preparation of the EMP object with high efficiency (due to the use of the diffusion process of changing the conductivity of the buffer drops chemically inert and elektroprovoda fluid between the sample and the signal electrode) excludes used in the prototype, complex implementation and operation of the optical principle of control. The independence of the proposed power who's" electrolytes, containing, for example, chromic anhydride, which may be required when the thinning of a number of metals and alloys.
Claims1. The method of preparation of samples for transmission electron microscopy of electrically conductive materials, which consists in electrochemical processing of its surface by the action of the jet of electrolyte, leading to thinning of the sample, and the end of the process is controlled by the appearance in it of micro-holes, characterized in that the surface of the sample immersed in the electrolyte acts adjustable frequency and amplitude of the pulsating jet of electrolyte, while the control process is finished thinning provide electrical contact with the circuit through the drop chemically inert and elektroprovoda liquid electrical circuit to sample the signal electrode on the occurrence of pinholes in tanaami sample areas.2. The device sample preparation for transmission electron microscopy of electrically conductive materials containing electrochemical cell system of jet formation electrolyte, the control system end thinning, objectiterator, characterized in that the electrochemical what its air pulsator, and at the other end of the channel containing the nozzle and connected with the total volume of the cell is set objectoperation with the sample and the signal electrode.3. The device according to p. 2, wherein the electrochemical cell has a camera cooling/heating of the electrolyte attached to the bottom of the electrochemical cell through the wall of the stainless plate.
FIELD: automatical aids for sampling liquids.
SUBSTANCE: system for sampling and delivering filtrate has filter submerged into tested medium and connected with collecting tank and vacuum pressure source which is connected with top hole of collecting tank by means of pneumatic pipe. System has sample receiving tank connected with collecting tank and control unit which has first output to be connected with vacuum pressure source. Collecting tank has two separated chambers - washing chamber and dispatching chamber. Lower hole of washing chamber has to be lower hole of collecting tank and side hole of dispatching chamber has to be side hole of collecting tank. Floating valve is installed inside washing chamber to shut off lower and top holes. Filter is connected with lower hole of collecting tank through sampling pipe. Side hole of collecting tank is connected with lower hole of tank for receiving samples through sampling pipe. Flow-type sensor and check valve are installed inside transportation pipe. Output of flow-type sensor is connected with input of control unit; second output of control unit is connected with control input of analyzer.
EFFECT: improved precision of measurement of sample ion composition; prolonged service life of filter.
1 cl, 1 dwg