Powdery, granular and conglomerate material treating apparatus and analyzing method using the apparatus

Abstract: A material treating apparatus is used for treating powdery, granular and conglomerate materials. The material treating apparatus includes a material supply apparatus (14) for transferring the materials to a predetermined position, particularly for supplying the materials to an automatic crusher (1). The material treating apparatus includes a crushing system having a crushing vessel transferring unit (8). The material treating apparatus further includes an analysis sample transferring apparatus particularly suitable for transferring samples formed by a press (101) to a fluorescent X-ray analyzing apparatus (102). The material treating apparatus includes a fluorescent X-ray analyzing system which is capable of automatically analyzing samples of various kinds. An analyzing method is carried out by the use of the above material treating apparatus. The analyzing method includes a method of vitrifying an inorganic material, which is preferably used for obtaining samples to be analyzed by the X-ray fluorescence analysis. The analyzing method further includes a method of pretreating samples for the X-ray fluorescence analysis.

Description: This invention relates to a method for treating powdery, granular or conglomerate materials. In analyzing components of various materials by a method such as the X-ray fluorescence analysis, it is necessary to pretreat the material to be analyzed. Following four methods have been known as methods for making samples of inorganic materials. 1) Crushing method in which a material is pulverized in order to bring the material into an appropriate condition for the analysis. 2) Vitrifying method in which a material is added with one or mixture of an alkali metal borate (for example, Li 2 B 4 O 7 , Li 2 O-B 2 O 3 and Na 2 B 4 O 7 ) and heated to be vitrified. 3) Alkali metal carbonate decomposing method in which a material is decomposed by an alkali metal carbonate. 4) Decomposition solution method in which a material in a pressurized vessel is decomposed by a strong acid such as hydrofluoric acid to make it a solution. With the crushing method among the above methods, it has a disadvantage in that if the material is at least partially crystalline, the crushed material still includes a crystal structure so that analyzed results with high accuracy could not be obtained in the X-ray fluorescence analysis due to so-called "mineral effect". Moreover, it takes long time to crush inorganic materials including non-oxides as components such as silicon nitride, sialon, silicon carbide and the like owing to high hardness. Moreover, there is a risk of the materials to be contaminated by a material of a vessel for crushing. Therefore, the crushing method has been scarcely used other than cases not requiring high accuracy of analysis. The alkali metal carbonate decomposing method is applicable as a pretreatment method for wet analyses even for non-oxides. However, this method could not be used for pretreating materials for the X-ray fluorescence analysis owing to the fact that decomposed and melted products are high in moisture absorption and difficult to be removed from used vessels such as platinum dishes and the like. The vitrifying method using the alkali metal borate has a disadvantage in that analyzed accuracy is often lowered because vitrification only partially progresses in case of inorganic materials including non-oxides as components. Moreover, the decomposition solution method using the strong acid requires a long time such as 24 hours for the decomposition. Obtained samples for the analysis are liquid which is preferable for the chemical analysis. However, it is difficult to use such liquid samples in the X-ray fluorescence analysis because of the limitation of an apparatus itself for the X-ray fluorescence analysis. So-called "mineral effect" has been known which means that grain sizes of samples detrimentally affect the accuracy of analysis of the samples. In order to avoid the mineral effect to carry out the analysis with high accuracy, it is necessary to pulverize samples in powdery, granular and conglomerate states into fine powders of the order of less than 1 µm and to form formed bodies suitable for analysis. It is preferable for the formed bodies to have smooth surfaces for high accuracy analysis. Moreover, it is desirable that the formed bodies are rigid and stable for a long period of time in order to facilitate the operation and automation for the analysis. The crushing to forming processes are referred to herein as "pretreatment of samples for the X-ray fluorescence analysis". The pretreating methods for the X-ray fluorescence analysis have been known as non-addition dry crushing and non-addition wet crushing methods which are carried out in dried and wetted conditions without any additions, powdery graphite added dry crushing which is carried out in dried condition with added graphite (magazine of Japanese Metallurgy Society, vol. 36, page 648, 1972), binder added wet crushing which is carried out in wetted condition with binders such as styrene-maleic acid copolymer or stearic acid. The powdery graphite has a lubricating effect so that it is effective as a crushing aid for promoting pulverization of samples. On the other hand, the binders are effective as a forming or molding aid which gives strength to formed bodies and makes smooth surfaces of the formed bodies. The graphite is also somewhat effective as a molding aid. However, the effect of the graphite as the molding aid is insufficient for disk-like formed bodies having diameters more than 10 mm which are usually used for the X-ray fluorescence analysis. Although the above non-addition dry crushing method is simple in operation, it has disadvantages in that as the crushing is sometimes insufficient, analysis accuracy is lowered due to the mineral effect, and the forming samples into disk-like bodies is difficult. The non-addition wet crushing method has disadvantages in that analysis accuracy is lowered and the forming samples into disk-like bodies is difficult and moreover volatilization of solvents is needed. The powdery graphite added dry crushing method has a disadvantage in that the forming samples into disk-like bodies is difficult although there is no problem of lowering of the analysis accuracy due to the mineral effect. The binder added wet crushing method has disadvantages in that there is the problem of lowering of the analysis accuracy due to the mineral effect and volatilization of solvents is needed. Therefore a pretreatment method of samples for X-ray fluorescence analysis has not been proposed capable of obtaining formed bodies which will bring high accuracy analysis and are rigid and smooth. It is an object of the invention to provide a method of pretreating samples for the X-ray fluorescence analysis, which mitigates the disadvantages of the prior art and obtains formed samples which is rigid and smooth to provide high accuracy analysis, and which is easy to automatize its operation and most suitable for high accuracy analysis of various kinds of samples. In order to address this object, the method of pretreating a sample for X-ray fluorescence analysis according to the invention comprises steps of adding a sample under any of powdery, granular and conglomerate conditions with powdery graphite and a forming aid simultaneously or one after another, crushing the sample under dried condition, and press-forming the sample. With the above constitution, the sample is added with the powdery graphite and the forming aid simultaneously or one after another, and crushed under dried condition, thereby obtaining formed samples made of crushed materials, which are rigid, smooth and stable for long period of time. With such samples, high accuracy analysis can be accomplished by eliminating the influence of the mineral effect on the analysis accuracy. In case that the material is added with powdery graphite and crushed and thereafter added with a forming aid and crushed, the crushing is progressed faster so that the influence of the mineral effect is more reduced. Vibration mills, attrition mills and planetary motion type mills can be preferably used as the crusher. However, the vibration mills are most preferable because of their high crushing efficiency. In case of using a vibration mill, the crushing time is of the order of 8 minutes with simultaneous addition of the graphite and forming aid. In case of addition step by step, the crushing time of the 4 plus 4 minutes is sufficient. A method of pretreating samples or specimens to be analyzed according to the method of the invention will be explained hereinafter. However, samples or specimens to be analyzed according to the method of the invention may be of course pretreated by any other methods explained herein. An actual embodiment will be explained. Granular feldspar specimen having sides less than 10 mm, powdery graphite and styrene-maleic acid copolymer were prepared and weighed to obtain compositions shown in Table 1. Thereafter, the weighed granular feldspar specimen, powdery graphite and styrene-maleic acid copolymer were simultaneously introduced into a vessel made of tungsten carbide and crushed or pulverized in dried condition by the use of a vibrating mill for about eight minutes. Then the crushed materials were pressed in dies as material holding means or without dies at forming pressure of 30 ton to obtain disk-like formed bodies having 38 mm diameters to be analyzed by the X-ray fluorescence analysis. At the same time, disk-like formed bodies were prepared in the same manner above described with exception of addition of the powdery graphite as comparison samples. Moreover, other formed bodies were prepared as samples of the prior art, in which the powdery graphite was added without adding the styrene-maleic acid copolymer. In other formed bodies as samples of the prior art, the crushing was effected without adding the powdery graphite. The material or formed body holding means were rings or cups for receiving the formed bodies in order to facilitate the forming operation and handling of the bodies which were poor in moldability. Steel rings, synthetic resin rings, aluminum rings, aluminum cups and the like are preferably used for this purpose. However, the steel rings are the most preferable because they are able to be repeatedly used and to retain deformation of the formed bodies to less extent. Although the diameters of the formed bodies are 38 mm in the above embodiment, the diameters are not limited to this value. For example, if amounts of samples are little, dies having smaller diameters may be used to obtain smaller diameters formed bodies. Formed bodies having small diameters of the order of 10 mm can be supplied to the X-ray fluorescence analysis according to the invention. Although the forming pressure of 30 ton (about 2.6 ton/cm 2 ) are used in the above embodiment, the forming pressure is not limited to the value. The forming pressure requires only to be able to give the formed bodies the strength sufficient to be supplied to the X-ray fluorescence analysis and is preferably 0.2-5 ton/cm 2 . The obtained formed bodies were compared with states of the bodies and measured accuracies of SiO 2 calibration curves by X-ray fluorescence analysis. The states of the formed bodies were classified into strong those designated by o ○ which were superior in surface smoothness and very stable for long periods of time, those designated by ○ which did not have cracks but were not very good in surface smoothness or less stable for long periods, those designated by Δ which were poor in accuracy owing to partial cracks but were able to be analyzed by the X-ray fluorescence analysis, and those designated by X which were not obtained in formed bodies. The accuracies σ of calibration curves were obtained by using reference samples according to the equation (1) above described. The results are shown in Table 1. As can be seen from the results of Table 1, the samples subjected to the pretreatment according to the invention are superior in state of formed bodies and make it possible to carry out correct measurements. Moreover, the same measurement was effected with other silicates. It has been found that the pretreatment method can be applicable to almost all the silicates. They are pulverized to average grain diameters of about 0.5 µm in a few minutes and disk-like formed bodies under good conditions are easily obtained. As can be seen from the above explanation, the mineral effect of samples is remarkably reduced to make the analysis with high accuracy by adding the forming aid such as powdery graphite and styrene-maleic acid copolymer to the sample simultaneously or one after another and crushing them in dried condition. Moreover, as the samples are crushed in dried condition according to the invention, the preparation of samples is completed in a short period of time. Furthermore, suitable formed body holding means makes it easy to automatically handle the formed bodies so that all the operations of the X-ray fluorescence analysis including the pretreatment can be automated with ease.

Claims: A method of pretreating a sample for X-ray fluorescence analysis comprising steps of adding a sample under any of powdery, granular and conglomerate conditions with powdery graphite and a forming aid simultaneously or one after another, crushing the sample under dried condition, and press-forming the sample. A method as set forth in claim 1, wherein the forming aid is styrene-maleic acid copolymer. A method as set forth in claim 1, wherein in the step of press-forming, material holding means is used.

Inventors: NARUKAWA AKIRA, NARUKAWA, AKIRA
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 1988
Main classification: G01N23
IPC codes: G01N23, G01N1