JP6150225B2 - Method for forming a surface region in which at least one of crystal orientation, crystal structure and composition changes depending on position, friction coefficient optimization method, and control method for at least one of crystal orientation, crystal structure and composition of surface - Google Patents

Description

  The present invention relates to a surface crystal orientation / structure / composition control method that can be used to search for a material crystal orientation / structure / composition for optimizing the friction coefficient of the material, and a method using the same.

  As global environmental and energy problems become more serious, expectations are growing for the development of energy-saving technologies by controlling frictional forces. For example, to give a familiar example, there are a large number of drive units inside a device such as a generator, and energy loss due to friction occurs in each of these parts. In order to suppress these, reducing the friction of the material will be one of the effective methods.

  Conventionally, there has been a technique for reducing frictional force by coating an existing structural material. The friction characteristics of this coating change greatly due to changes in its crystal orientation, structure, and composition, so research and development on how to efficiently search for crystal orientation, structure, and composition with low friction characteristics in a short period of time. It was the key.

  According to previous studies by the present inventors, it has been found that the friction characteristics and the crystal orientation / structure / composition of the material are closely related. For example, zinc oxide (ZnO), which is a general metal oxide, exhibits a low friction phenomenon when its crystal orientation is optimized (Non-Patent Documents 1 and 2). However, in order to know the optimum crystal orientation for having the low friction characteristics, a large number of samples with various crystal orientations were changed by changing the coating conditions, and the crystal orientation and friction characteristics were evaluated. There was a need to do. This required a lot of research and development.

  By the way, a novel material search technique called combinatorial technology is known in which a very small amount of each compound is synthesized at once and a desired one is selected from them. For example, when applying this technique to analysis of thin film properties or searching for the optimum composition of a thin film, the ratio of various components supplied during the formation of a single thin film is changed from place to place. A film in which the composition ratio between a plurality of components continuously changes is formed. The required measurements are made at a number of locations on the film thus formed. Thereby, the characteristic analysis about many composition ratios can be analyzed in the very highly efficient procedure of formation of one film | membrane, and the repetition of the measurement by changing the place on it. However, even in this case, although a method for changing the component composition has been established, a method that can be used for combinatorial technology that changes the crystal orientation, structure, and composition, which greatly affects the frictional characteristics, for each position. No proposal was made.

  An object of the present invention is to eliminate the above-mentioned problems of the prior art and to locally control the crystal orientation, structure and composition of the material surface.

According to one aspect of the present invention, at least one of a crystal orientation, a crystal structure, and a composition that slides a member while changing a load applied at each position in the region on a desired region of the surface is positioned. A method of forming a surface region that varies with
Here, by preparing the surface with the composition changed according to the position and performing the sliding on the surface with the composition changed according to the position, at least one of the crystal orientation and the crystal structure depends on the position. You can change it.
The sliding may be repeated a plurality of times.
The surface may be made of ZnO.
According to another aspect of the present invention, a surface region in which at least one of crystal orientation, crystal structure, and composition varies depending on a position is formed on the surface by any one of the above methods, A friction coefficient optimization method is provided in which the coefficient of friction is measured to determine the position where the coefficient of friction is minimum, and at least one of the crystal orientation, crystal structure and composition of the position where the coefficient of friction is minimum is determined.
Here, the measurement of the friction coefficient may be performed simultaneously with the sliding.
According to still another aspect of the present invention, there is provided a control method of at least one of a crystal orientation, a crystal structure and a composition of a surface, wherein a member is slid while applying a load on a desired region of the surface.
Here, the sliding may be repeated a plurality of times.

  In the present invention, the crystal orientation, structure, and composition on the surface of various coating films or bulk materials can be controlled for each position by a simple procedure.

The photograph which shows the sliding trace on ZnO coating, and the X-ray crystal structure analysis position performed on it. The figure which shows the graph which piled up the X-ray-diffraction spectrum acquired for every position of the sliding trace shown in FIG. The figure which shows the change by the measuring point of the magnitude | size of the peak of the typical crystal plane index in the X-ray-diffraction spectrum shown in FIG. The schematic diagram which shows the difference by the measuring point of the crystal orientation of the crystal grain on a sliding trace as shown in FIG. The figure which shows the change of the friction coefficient obtained by the sliding experiment.

  The inventor of the present application analyzes how the crystal orientation / structure / composition of the coating film can be continuously changed, and how to analyze the crystal orientation / crystal structure / composition of each part, and determine the friction coefficient thereof. We examined whether to make it correspond. In the process, the sliding structure (load, indenter material type, number of sliding, etc.) was changed and the crystal structure of each sliding trace was analyzed for each micro area. I found a change. It was also found that the correlation between the friction coefficient and the crystal orientation can be clarified by only one experiment by measuring the friction coefficient at the location corresponding to the crystal orientation. The present invention has been made based on such findings, and will be described in more detail below based on examples. In the following examples, specific experimental examples will be described in detail with respect to the change / control of crystal orientation, but the change / control of crystal structure and composition will also be described.

  In this embodiment, a ZnO coating film will be described as an example for controlling the crystal orientation, but the present invention can be applied to various other materials and forms (film thickness, film / bulk difference, etc.). Needless to say.

  A sample in which a ZnO coating was applied on a stainless steel substrate (440C) by sputtering was prepared. This coating film was reciprocated 200 times at a speed of 0.5 mm / s by a ball indenter (diameter 3 mmφ) made of stainless steel (440C) while changing the load continuously from 0.1 to 3.0 N. Slid. Of course, the friction coefficient for each position can be obtained continuously during the sliding. FIG. 1 shows a sliding mark formed by this sliding. The sliding structure was evaluated at the micrometer level using an X-ray crystal structure analyzer with a two-dimensional detector (Rigaku, SmartLab). FIG. 1 also shows the measurement point numbers (measurement point numbers) that are positions where the crystal structure analysis has been performed on the sliding traces (numbers starting with 1 from the low load side). As can be seen from this photo, the side with a small load has little wear due to the indentation or sliding of the ball indenter, so the width of the band of the sliding trace is narrow, and the width becomes wider as the load increases. .

  Next, FIG. 2 shows a superposition of the X-ray diffraction spectra acquired at these positions. Even if the position of the measurement point was changed, the position of each peak corresponding to the various crystal planes of ZnO did not change, but it became clear that the size increased or decreased. For example, an enlarged view around 2θ = 31.5 ° is shown on the left side of FIG. From this enlarged view, it can be seen that the (100) peak shown here decreases with increasing load. This is because the crystal orientation is changed by frictional heat due to sliding.

  FIG. 3 shows typical crystal plane index peaks ((100): 31.769 °, (002): 34.421 °, (101): 36.252 °, (102)) in the X-ray diffraction spectrum. ): 47.538 [deg.], (110): 56.602 [deg.], (103): 62.862 [deg.], (200): 66.378 [deg.] (The peak positions shown above are data described in the database) ))) Excerpted and expanded. The peak intensity gradually changes due to the difference in sliding position (change in load). For example, on the (100) and (002) planes, the peak intensity gradually decreases. On the contrary, the (101) plane showed a tendency for the peak intensity to increase. In the case of a stainless steel indenter, for example, the peak strength of the (100) surface decreased in proportion to the increase in load, but when the test was performed with a sapphire indenter, the load was larger than that of the stainless indenter. It was found that the peak intensity did not decrease without applying.

  From the above-described experiment, it has been clarified that the crystal orientation continuously changes as the applied load increases or decreases. In addition, the change in crystal orientation is also affected by a member that gives the number of sliding times and a load (for example, whether a stainless steel indenter or a sapphire indenter is used). FIG. 4 is a schematic diagram showing the difference in crystal orientation due to the difference in shading and texture for each crystal grain on the sliding trace as shown in FIG. 1, and crystal grains having a specific orientation depending on the magnitude of applied load. It shows that it increases or decreases.

  FIG. 5 shows the change in the coefficient of friction obtained by this sliding experiment. The change in the crystal orientation of the ZnO coating film and the change in the friction coefficient can be associated with each other, and the crystal orientation of the coating film having the necessary friction coefficient can be specified from the information. This has made it possible to greatly accelerate friction research. Furthermore, by using the method of the present invention, it is possible to modify a desired position on the material to a desired crystal orientation by rubbing a desired position on the material while controlling sliding conditions.

  Note that there are two phenomena in which the friction coefficient is minimized by controlling the crystal orientation. That is, the friction coefficient is minimized when a specific single crystal orientation is taken, and the crystal orientation of various crystals appearing on a plurality of specific control target surfaces is not a specific crystal orientation. This is the case when the coefficient of friction is minimized when a combination is taken (that is, when a certain number of crystal orientations appear in a certain ratio). The present invention can deal with any of the above cases.

  The above experiment is for controlling the crystal orientation, but the change and control of the crystal structure can also be realized by sliding while changing the conditions as described in detail above. The composition is conventionally used in the combinatorial technology field, etc., and is supplied by the position on the substrate surface when the sample substrate before the sliding treatment is made, for example, by a method of continuously changing the composition. It is also possible to apply a composition ratio or a supply time ratio between a plurality of raw materials. Alternatively, for example, the composition can be controlled or changed by accelerating the segregation of the material by the heat and pressure of friction caused by sliding as described above. Therefore, according to the present invention, various combinations of these can be realized on a single sample or a small number of samples by simultaneously changing the three elements of crystal orientation, structure and composition. Of course, it is of course possible to prepare and evaluate a sample in which not all of these three elements but only two or only one of them are changed as necessary, and the present invention has such a form. It is not excluded.

  According to the present invention, it is possible to obtain knowledge of the crystal structure necessary for expressing a necessary friction coefficient for a film or a bulk material by a few experiments. Would be a powerful tool for. Further, the present invention is expected not only as research and development, but also as an innovative technique that can selectively control the crystal orientation of the material surface that affects the friction coefficient and the like.

Low-Friction Coatings of Zinc Oxide Synthesized by Optimization of Crystal Preferred Orientation, Masahiro Goto, Akira Kasahara and MasahiroTosa, Tribology Lett., 43 (2) (2011) 155-162. Reduction in Frictional Force of ZnOCoatings in a Vacuum, Masahiro Goto, Akira Kasahara and Masahiro Tosa, Jpn. J. Appl. Phys., 47 (2008) 8914-8916.

Claims (7)

  A method of forming a surface region in which at least one of crystal orientation, crystal structure, and composition varies depending on the position, on a desired region of the surface, by sliding a member while changing a load applied at each position in the region. . The method of claim 1, wherein the sliding is repeated a plurality of times . The method according to claim 1, wherein the surface is made of ZnO . A surface region in which at least one of crystal orientation, crystal structure and composition varies depending on the position is formed on the surface by the method according to claim 1,
  Measure the coefficient of friction for each position on the surface area to determine the position with the smallest coefficient of friction,
  Determining at least one of crystal orientation, crystal structure and composition at a position where the friction coefficient is minimum;
Friction coefficient optimization method. The method according to claim 4, wherein the measurement of the coefficient of friction is performed simultaneously with the sliding . A control method for at least one of crystal orientation, crystal structure and composition of a surface, wherein a member is slid while changing a load applied to each position in the region on a desired region of the surface. The method according to claim 6, wherein the sliding is repeated a plurality of times .