A method for producing a fine copper powder which includes solid phase thermal decomposition of an anhydrous copper formate in a non-oxidizing atmosphere at a temperature in the range between 150 and 300 ° C to obtain a fine copper powder having a primary particle diameter of 0,2 to 1 μm, a specific one Surface of 5 to 0,5 m² / g and having a low tendency to agglomerate, said anhydrous copper formate being an anhydrous copper formate powder having a particle diameter of 20 mesh or finer and 90 by weight or more within a temperature range between 160 and 200 ° C undergoes thermal decomposition when the anhydrous copper formate powder is heated in a nitrogen or hydrogen gas atmosphere at a heating rate of 3 ° C / min. and said anhydrous copper formate powder is obtained by dehydrating copper formate hydrate at a temperature of 130 ° C or less and then pulverizing the anhydrous copper formate, or by at least one copper compound selected from the group consisting of copper carbonate, copper hydroxide and copper oxide is reacted with formic acid or methyl formate. A method as claimed in claim 1 for producing a purified fine copper powder which comprises washing the fine copper powder obtained by the method claimed in claim 1 with water, an organic solvent or a solution of a rust inhibitor for copper in water or in an organic Solvent so as to reduce in said powder at least one impurity element selected from the group consisting of halogens, sulfur, alkali metals and heavy metals. All components of this product are listed in the U.S. Environmental Protection Agency Toxic Substances Control Act Chemical substance Inventory. In the method of the present invention, an anhydrous copper formate powder as described above is thermally decomposed in the solid phase to produce a fine copper powder.

As compared with the copper powders obtained by the reduction method and the like, the fine copper powder produced by the method of the present invention is more slowly oxidized in the air. Therefore, even if the fine copper powder according to the present invention is left in the air, no color change caused by oxidation takes place unless the duration of exposure is short. Since the produced fine copper powder contains impurity elements which were originally contained in the anhydrous copper formate powder which was expected to be present, and most of which adhere to the surface of the powder particles, it is preferred that the fine copper powder be mixed with water, an organic solvent or an organic solvent Solution of a rust inhibitor for copper in water or in an organic solvent is washed to reduce the impurity elements, such as halogens, sulfur, alkali metals and heavy metals. By such a washing treatment, for example, 90% or more of the alkali metals and halogens present as impurity elements may be removed, though depending on the amount of these impurity elements. Hirschhorn, Introduction to Powder Metallurgy. New York, American Powder Metallurgy Institute, 1969. Self-lubricating porous bronze bearings depend on conduction and convection for heat dissipation during service. The frictional heat developed is proportional to PVµ where P is the pressure on the bearing, V is the surface velocity and µ is the coefficient of friction. Practical limits for safe operation of these bearings are often set at a PV factor of 50-60 ksi (345-414 MPa). These bearings are installed by pressing into rigid reamed or bored housings. This powder was a fine copper powder having an oxygen content of 0,4% or less, consisting of nearly spherical primary particles uniform in size and having an average particle diameter of about 0,3 μm, and having a specific surface area of ​​3 m² / g would have. The powder thus obtained, which was the product of thermal decomposition, showed a copper color and consisted of uniform nearly spherical primary particles having an average particle diameter of about 0,3 μm. However, the powder became brown within a relatively short time. In addition, the agglomerate particle diameter of the powder was measured (on average) after the powder was dispersed in water by the treatment with a mixer, and found to be about 20 μm.

Isotopic ultrafine copper powder at least 99,999x%

This product is subject to the reporting requirements of section 313 of the Emergency Planning and Community Right to Know Act of 1986 and 40CFR372. After casting, the metallic appearance will not be clear or vivid because the metal particles will be obscured behind a thin layer of resin. To reveal the metallic appearance, the casting can be rubbed with an abrasive pad or wire-wool.

The sintered yield strength increases from 11 ksi (26 MPa) at 7% aluminum to 40 ksi (276 MPa) at 11% aluminum; heat treatment of the latter alloy increases the yield strength to 60 ksi (414 MPa). Tensile strengths increase uniformly from 32 ksi (221 MPa) for the 7% alloy to 65 ksi (448 MPa) for the heat treated 11% alloy. Elongations of the 5% to 9% alloys are in the 25-35% range; the two phase alloys are considerably less ductile. 4 These properties make the P/M aluminum bronzes suitable for the production of parts where the strength requirements are too high to be met by the tin bronzes. The present invention will be explained in more detail with reference to the following examples and comparative examples, but the examples should not be construed as limiting the scope of the invention. In these examples, unless otherwise stated, all parts and percentages are based on weight. In addition, with the exception of anhydrous copper formate, all copper compounds must be heated in a reducing atmosphere (H 2 gas) to form metallic copper powder, and their reactions in the reducing atmosphere are exothermic, their exothermic amounts of heat at least five times greater than that of anhydrous copper formate are. The powder thus obtained, which was the product of thermal decomposition, showed a brown color, had an oxygen content of about 3%, and consisted of uniform nearly spherical primary particles having an average particle diameter of about 0,3 μm. The agglomerate particle diameter of the powder was measured (on average) after the powder was dispersed in water by the treatment with a mixer, and found to be about 15 μm.V. Morgan, "Applications of Porous Metal Bearings," Industrial Lubrication & Tribology 24(3):129-138 (1972). Aluminum bronze P/M parts containing from 5% to 11% aluminum are prepared from blends of the elemental powders. Alloys containing from 5% to 9% aluminum are single-phase materials and have excellent ductility. They can be strengthened by cold working. Alloys containing from 9% to 11% are two-phase materials which are less ductile than the alloys of lower aluminum content. However, they can be heat treated to increase their strengths. This powder was a fine copper powder consisting of nearly spherical primary particles uniform in size and having a uniform particle diameter of about 0,4 μm and having a specific surface area of ​​2 m² / g. The agglomerate particle diameter of the powder was measured (on average) after the powder was dispersed in water by the treatment with a mixer, and found to be about 8 μm. With the exceptions that 0,66 kg of cupric oxide powder and 2,4 kg of 80-percent formic acid solution were used as starting materials and that the starting materials were mixed and stirred at 80 ° C 20 for hours, anhydrous copper formate crystals in an amount of 1,28 kg in same way as in example 1. The degree of thermal decomposition of the thus obtained anhydrous copper formate was practically 100%.

Metals such as copper and lead which have very limited solubilities in each other are difficult to alloy by conventional means but copper-lead powder mixtures have excellent cold pressing properties. They can be compacted at pressures as low as 11 ksi (76 MPa) to densities as high as 80% and, after sintering, can be repressed at pressures as low as 22 ksi (152 MPa) to produce essentially nonporous bearings.

Introduction

Source: Standards Handbook, Part 2, Alloy Data. New York, Copper Development Association Inc., 1973. A ratio of at least 50% copper powder (by weight) would be required to result in a significantly metallic appearance. Higher ratios, up to the limit of pour-ability, will yield a more impressive metallic appearance and feel.

Anhydrous copper formate produced by any of a variety of methods can be used in the present invention as far as the copper formate to be used satisfies the above requirements. However, anhydrous copper formate prepared by a method using copper carbonate, copper hydroxide or copper oxide as the starting copper compound and reacting this starting copper compound with formic acid or methyl formate is useful as a starting material for the process of the present invention when the process is industrial is performed. and stirring or ultrasonic treatment (indicated by *) was performed for ten minutes. In cases where a washing operation has been repeated, the number of repeated washing operations is shown in the table after 'x' (e.g. 'x9' means 'washed nine times'). The washing liquids and the washing technique for each copper powder shown in the table 3 are as follows. R51/53: Toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment. Source: A.K.S. Rowley, E.C.C. Wasser and M.J. Nash, "The Effect of Some Variables on the Structure and Mechanical Properties of Sintered Bronze," Powder Met. Int. 4(2):71 (1971).The thermal decomposition behavior of these copper compounds was examined by means of a differential thermal balance analysis in which copper hydroxide, basic copper carbonate, anhydrous copper formate and a product of the subsequent decomposition reaction of copper formate, each weighing 10 mg, in an N 2 or H 2 gas atmosphere with a heating rate of 3 ° C / min. were heated. The results obtained on the peak temperatures in the calorimetric changes (endothermic, exothermic or the like changes) and the decomposition products are shown in Table 1.