Process of producing an X-ray lens

Abstract: It was found that polyfeniren oxadiazole is heat treated at a high temperature above 2800°C under normal pressure thereby to be easily formed into a crystalline graphite. A graphite film obtained by graphitizing a film-like polyfeniren oxadiazole has a sufficient flexibility while being mono­ crystalline. The thus obtained graphite film is able to have a sufficient area, which is plastered on a base plate thereby to be used as a reflecting mirror and a lens for radiation such as X-ray, neutron ray, etc.

Description: This invention relates to a graphite-crystal element used as a radiation optical element in X-ray spectrum, neutron spectrum, etc. It is well known that optical elements used for X-ray optical instruments such as an X-ray spectroscope, an X-ray microscope, etc. generally uses Bragg reflection of crystal other than the total reflection of X-ray which skims the surface, which is used in the special case. Crystals used for the purpose as described require that a crystal construction is complete, that crystal having a size as necessary is obtained, that crystal is small in absorption coefficient with respect to X-ray, and that crystal has a flexibility when used for a crystal spectroscope or the like. Graphite is one of elements which are desired as an X-ray optical element since the absorption coefficient relative to the X-ray is small, which is being marketed as CAPG (Compression-annealed pyrographite) by Union Carbide Ltd. This product is obtained by annealing graphite crystal for a long period of time while pressurizing the same. As is well known, the Bragg reflection is represented by 2 d sin ϑ = λ where d represents the spacing of a crystal lattice, λ the wavelength of reflection X-ray, and ϑ the reflection angle. It is said in case of graphite of UNION CARBIDE LTD. that when a monochrome X-ray, for example, Kα line (λ = 1.5418 Å) of Cu is reflected at (002) face, the spacing d of the lattice is close to d = 3.354Å which is the spacing of graphite monocrystal, and the width Δδ oo2 of the reflection line is approximately 0.7°. However, when an attempt is made to obtain such graphite as described above, in monocrystal of natural graphite, it is impossible to obtain one having a large area. If an attempt is made to obtain graphite by hot rolling a hot cracked sedimentary material of hydrocarbon, annealing at high temperature for a long period of time under pressure is required, which involves a complicated manufacturing process, and higher cost of products. In case of converging X-rays, in the past, a flexed, thin silicon monocrystal has been used, or graphite is subjected to machining to form a spherical lens. Either process involves cumbersome process of manufacture and increases cost. The present invention provides an artificial graphite which can be produced simply without use of a complicated process such as pressurizing and annealing or the like, thus obtaining it at low cost, and which has complete crystallinity and flexibility with a large area. It is known that when a polymer is subjected to thermal cracking, it is carbonized while maintaining its original shape. This process is a good process for producing a carbonaceous material having flexibility and a large area. However, the carbonaceous material obtained by this process is often graphite free having a construction different from graphite. As the result of researches of thermal cracking of various kinds of high polymers, the present inventor has found that a material (hereinafter referred to as GPOD) obtained by processing poly (para-phenylene 1, 3, 4-oxadiazole) (hereinafter referred to as POD) is suitable for graphitization, and a graphitized film has a flexibility which is suitable for use in a radiation optical element such as X-ray lens. The POD as a starting material for graphitization is a known, heat-resistant polymer. It is generally obtained by dewatering and cyclizing polyhydrazide which is obtained by polycondensation of terephthalic acid and hydrazine. It is also possible to obtain POD by reaction of dimethylterephthalate and hydrazide sulfate or reaction of terephthalic acid chloride and hydrazine, etc. POD is soluble in concentrated sulfuric acid, and a film obtained by casting from a concentrated sulfuric acid solution has a high crystallinity. This is considered to result from the ordered orientation of high-polar 1, 3, 4-oxaziazole rings induced by mutual interaction action of dipoles. POD easily forms a nitrogen-containing condensation polycyclic construction by heat treatment at a temperature of 520 to 1400°C, and this apparently results from the orientation of POD. It is assumed that the presence of such controlled polycyclic construction makes it easy to provide graphitization. Accordingly, if various isomers of POD have a high crystallinity, they have a similar property of easy-graphitization. Isomers of POD include poly (m-phenylene-1, 3, 4-oxadiazole), poly (p-phenylene-1, 2, 4-oxaziasole), poly (m-phenylene-1, 2, 4-oxaziasole), poly (o-phenylene-1, 3, 4-oxaziasole), poly (o-phenylene-1, 2, 4-oxaziasole) and copolyers thereof, etc. Such a process for the production of graphite from POD is disclosed in EP-A-0203581. The reaction of the graphitization is promoted by the presence of pressure or catalyst. For example, under a pressure of 5 Kb, the same effect is obtained by heating at 2200°C, as heating at 2800°C under normal pressure. Also, the reaction of graphitization is promoted by heat treatment under the presence of elements in the periodic table IV B to VII B . The property values of GPOD obtained by treatment of the aforesaid starting material at a temperature above 2800°C under normal pressure are given below: (1) The reflection lines with respect to CuKα (1.5418 Å) correspond to faces 002, 004 and 006 as shown in Fig. 1. (2) The reflection angle (2ϑ) of the face 002 is 26.576°, and the distance d is 3.354 Å, which coincides with that of graphite monocrystal. (3) The half-value widths of the reflection line (around 2ϑ=26.576°) of the face 0.02 were 2.0° and 0.14° with respect to the heat treating temperatures 2800°C and 3000°C, respectively. (4) GPOD has a flexibility, and an area thereof may be increased as desired according to the area of the starting material POD and the size of a heat treating furnace. According to the present invention there is provided a process for producing an X-ray lens comprising the steps of heat treating a polyphenylene oxadiazole material to convert the polymer to a graphite film having a pre-determined value of line width of 002 reflection and applying said graphite film to an inner surface of a cylindrical base member thereby to form the X-ray lens. Reference will now be made to the accompanying drawings, in which: FIG. 1 shows a reflection spectral of CuKα line of GPOD; FIG. 2 shows one embodiment of the present invention and is an optical arrangement to which an X-ray lens is applied; and FIG. 3 shows a further embodiment of the invention and is an optical arrangement to which an X-ray monochrometer is applied. 1) X-ray lens FIG. 2 shows an example in which GPOD is plastered on the inside of a cylindrical surface to form a converging lens. A CuK alpha-ray is incident upon a lens 1 prepared by plastering GPOD having a size of 5 cm x 10 cm and a thickness of 30 µ onto the base plate, through a hole having 1 mm  of an Mo plate 2. An image on a photographic dry plate 3 placed at a focal position is formed into a single line of which length is 1 mm and width is approximately 15 µm, and an excellent condensation was obtained. A fine pattern less than 1 µm was obtained by causing the lens to pass through twice. 2) X-ray monochrometer FIG. 3 shows an example in which GPOD Is plastered onto a plane base plate to form of a monochrometer. The monochrometer 4 is prepared by plastering GPOD having a size of 5 cm x 5 and a thickness of 15 µm onto a smooth glass base plate, and the wavelength of X-ray passing through a pin hole of an Mo plate 2 may be varied by varying an angle e. The X-ray having passed through the pin hole passes through a pin hole of a second Mo plate 2′ by the lens 1 similar to that of Embodiment 1 and is condensed at a counter 5. When X-ray with Cu as a target is incident the characteristic X-ray of CuK alpha was intensely observed in the direction of ϑ=13.288°. When this is compared with the case where a natural graphite monocrystal was used, the line width is decreased from 0.3° to 0.2°, thus assuring the high performance of GPOD. While in the embodiment, a description has been made of an X-ray optical element, it is to be noted that since the material is graphite and is small in absorption of neutron, this can be used as a monochrometer in a neutron spectrum, an analyzer and a filter on the basis of the same principle in addition to one for the X-ray. According to the present invention, as described above, it is possible to produce a completely graphitized GPOD at a temperature much lower than that of a conventional CAPG which is above 2800°C, and an X-ray optical element was able to be obtained at an extremely low cost. In addition, an element having a larger size may be obtained as well as great flexibility. This is very convenient to form an X-ray lens and the like.

Claims: A process of producing an X-ray lens comprising the steps of heat treating a polyphenylene oxadiazole material to convert the polymer to a graphite film having a predetermined value of line width of 002 reflection and applying said graphite film to an inner surface of a cylindrical base member thereby to form the X-ray lens. A process of producing an X-ray lens as claimed in Claim 1 wherein the polyphenylene oxadiazole material has been heat treated without the application of additional pressure.

Inventors: MURAKAMI MUTSUAKI, YOSHIMURA SUSUMU, MURAKAMI, MUTSUAKI, YOSHIMURA, SUSUMU
Applicants: JAPAN RES DEV CORP, MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD., RESEARCH DEVELOPMENT CORPORATION OF JAPAN
Application year: 1986
Main classification: G21K1
IPC codes: G21K1, G21K7