The method of obtaining powder of iron-silver


(57) Abstract:

Usage: in the field of powder metallurgy, in particular for the manufacture of powders based on iron, which can find application in chemical industry and medicine. The inventive carry out the formation of crystallization centers in the form of particles of metallic silver is precipitated on them oxalates of iron with a subsequent heat treatment in a reducing environment. Get the powder, Fe-Ag, which is corrosion-resistant, can withstand temperatures of sterilization and has antibacterial properties. 1 C.p. f-crystals.

The invention relates to powder metallurgy, in particular to the manufacture of powders based on iron, and can be used in chemical industry and medicine.

It is known that ferromagnetic powders due to the magnetic adresate delivery to the target organ can localize it drugs, thereby increasing the activity of drug action on pathological tissues.

From the point of view of efficient use of ferromagnetic powders in medicine and biology, they must have certain physical-chemical properties, such is acaricides. So, for the first time as the magnetic material was used ferromagnetic substance in the form of carbonyl iron particles with a size of 1-3 μm when introduced into the animal organism. Particles of metals such size have a high propensity to oxidation and require special storage conditions in the atmosphere of inert gas or in vacuum. Even a short exposure to air leads to oxidation, and hence to loss of physico-chemical properties. The degree of dispersion of carbonyl iron is not high enough for many biomedical research. Therefore underway to develop methods that provide hydrophilic, highly dispersed powders based on iron, resisting corrosion and has a bactericidal action.

A method of obtaining highly dispersed magnetic powder in a double-layer electrolytic bath.

The method is implemented as follows.

In the closed cell type, equipped with a rotating cathode and a fixed anode of iron "Armko", fill in an aqueous solution of iron salts, chloride, sulfate, sulfur-ammonia solution.

The mode of deposition of the magnetic powder, for example, a particular issue is the radio of salt in the electrolyte 25-300 g/l depending on the claimed dispersion of the obtained particles. After electrolysis the upper layer is separated from the bottom, the powder is washed with ethyl alcohol and dried in the vacuum oven to a constant weight. The resulting product is a black magnetic powder with a particle size of 0.1 to 1.0 μm; having the form of dendrites and contains 57% of the metal phase.

Sample powder with a particle size of 0.15 and 0.35 μm part is subjected to application in a constant magnetic field of 4 -120 kA/m at the facility for testing hard magnetic materials-5022. Bactericidal properties has been determined using the agar wells.

This molten agar medium is poured into 20 ml sterile Petri dishes with a diameter of 100 mm Before infection Staphaureus "209"/P/ surface environment dried for 40 min at room temperature. Bacterial suspension of Staphylococcus Staphylococcus in the amount of 1 ml are distributed uniformly on the surface environment. Then, using tubes with a diameter of 10 mm bore wells in the environment and in the wells fall asleep sample powder 5 mg Results read after 24 h after conditioning cups at 37oC. as the results is soaking zone of microbial growth around the wells with the sample powder, including the hole with a ruler. Powders Telesot Staphaureus 209/P/, equal 16-30 mm Area commensurate with the area of action of the antibiotic monomitsina.

Thus, there is a method of providing bactericidal powder is closest to the invention on the achieved result. However, from the point of view of use in medicine powder has the following disadvantages:

the powder has a hydrophobic surface and not moistened with either water or physiological fluids, resulting in can not be used for intravenous or intramuscular administration of it in the body;

quite a large particle size 0,15-0,35 µm and their dendritic shape is also not conducive to the introduction of it into the body.

As installed, the powder obtained according to the method, characterized

low corrosion resistance, because when stored for 6 months at room temperature iron metal contained therein, is reduced by 22%

may not be subjected to temperature sterilization 100-120oC, because at temperatures above 65oC is an intensive oxidation of the powder.

Closest to the invention is a method of obtaining ferromagnetic powder /U.S. patent N 4063000, CL H 01 F 1/02, publ.1977/.

The ferromagnetic powder is a repair using a reducing agent in a solution of a metal salt capable of forming a ferromagnetic metal powder, and salt nonmagnetic metal. The ferromagnetic metal powder is separated from the other reaction products, etc.

As follows from the chemical nature of the powder, it cannot be used in medicine due to the presence in its composition toxic to the body in large amounts of cobalt and Nickel. Thus, the maximum permissible concentration of cobalt in the form of CoSO47H2O in water is 1 mg/l (hazard class for cobalt 2), and Nickel should not be present in the water.

Thus, from the analysis of the prior art, it follows that no known way of providing a ferromagnetic powder with the required physico-chemical and biological characteristics satisfying the requirements of medicine.

The basis of the invention tasked to develop a method of obtaining a ferromagnetic powder, based on the prior receipt of centers of crystallization with subsequent deposition on them oxalate metal, in which the formation of crystallization centers in the form of metal particles is hydrophilic, corrosion-resistant powder Fe-Ag, can withstand the temperature of sterilization and acquiring bactericidal properties when the magnetization in a magnetic field. The specified properties of the powder Fe-Ag can be used in medicine and biology.

To solve this problem, a method for obtaining a powder of Fe-Ag, including the prior receipt of centers of crystallization, deposition on the last metal oxalates, Department of the obtained particles with a subsequent heat treatment in a reducing environment, in which the crystallization centers prepare recovery of silver ions of bivalent iron and the obtained metallic silver particles precipitated oxalate of iron; the iron oxalate precipitated with 5-10oC.

The basis of the proposed method is based on the possibility of obtaining mono - and highly dispersed silver particles directly in the reaction mixture in the recovery of silver ions iron /N/ (Ag++ Fe2+__ Ag+Fe3+used as crystallization nuclei for subsequent receipt of oxalate powders based on iron. We believe that the silver particles is the adsorption of molecules of the reducing agent FeSO4the donor electrons that provide the Snov iron plate at the optimum temperature of its formation 5-10oC.

When thermal decomposition of oxalate powder based on iron in a reducing environment, the formation of fine powder of Fe-Ag, the surface of which is formed iron carbide Fe3C, as evidenced by the data Mossbauer spectroscopy. We believe the presence of iron carbide on the surface of the powder Fe-Ag and gives it a high corrosion resistance.

Thus, the totality of the proposed signs yields a powder of Fe-Ag, having a plate shape particle size of 0.015 to 0.15 μm, with:

hydrophilic surface, which is characterized by a heat of wetting Q= 1000,5 erg/cm2;

corrosion resistance, characterized by almost constant content of metallic iron at 56-58 wt. and magnetic properties during 6 months storage:

s= 88-90 S2/kg induction saturation specific;

r= 21 Am2/kg residual induction unit;

Hc320 340 e coercivity;

K 0,236 0,237 coefficient of Squareness.

and to maintain the temperature of sterilization 100 120oC.

We have shown that when a powder of Fe-Ag magnetic field h the sticks Preudo mas aeguginosa, equal to 15 to 30 mm

The method is implemented as follows.

Serves 4 solution, each separately with stirring on a magnetic stirrer.

Solution 1 contains oxalic acid, sucrose, distilled water and ethyl alcohol.

Solution 2 contains acetic acid, heptahydrate iron, silver nitrate, sucrose, ethanol, distilled water.

A solution of 3 aqueous solution of oxalic acid.

A solution of 4 aqueous solution of iron sulfate heptahydrate.

All 4 solution is cooled to room temperature and then to 5 - 10oC. the Temperature below 5oC it is difficult to practically implement, and the temperature of >10oC does not provide the necessary dispersion of a powder of iron oxalate. Then the prepared solutions are mixed with stirring in the following order: to the solution of 2 was added a solution of 1, the resulting mixture, and then a solution of 4 is introduced into the solution 3. After mixing the mixture of all 4 solutions additionally stirred for 30 to 40 minutes on a magnetic stirrer. After settling for 2 to 3 h, the resulting suspension is filtered, the precipitate washed with water to remove sucrose, and then with acetone. The resulting powder oxalate is hydrogen flow in the temperature range 200 400oC. When cooled heat-treated samples blow them first with argon, then air.

Techniques used in research superfine powder of Fe-Ag.

1. To establish the nature of the surface of the powder Fe-Ag were determined heat of wetting by the method /Poles C. E. Polyakova, I. Tarasevich Y. I. Peculiarities of determination of the heats of wetting of dispersed minerals with low specific surface/ /Colloid journal, 1976. vol. 38, 188 N. C. 191-193./

Installed: the heat of wetting of the powder Fe-Ag Q 1000,5 erg/cm2that indicates a hydrophilic surface of a powder of Fe-Ag.

2. On the corrosion resistance of powder Fe-Ag was judged by the change of magnetic properties: Hc320 340 e; K 0,236 0,237 within 6 months, measured by the method using a vibration magnetometer and constant content of metallic iron 56 58 wt. defined by well-known methods.

3. The plate shape of the powder particles of Fe-Ag and the size of 0.015 to 0.15 μm determined by performing electron microscopic studies.

4. Temperature sterilization powder Fe-Ag 100 -120oC is installed on derivatograph 0 1500 D firm "Paulik. Erdei" /Hungary/ method thermogravity stick Preudomanas aerugin and is characterized by a zone of action of the antibiotic monomitsina.

Example. Pre-cook 4 solution, each separately with stirring on a magnetic stirrer, and cooled to 5oC.

Solution 1. 63 g of dihydrate oxalic acid, 375 g of sucrose, 375 g of distilled water, 375 ml of ethyl alcohol.

Solution 2. 0.17 g of silver nitrate, 20 g of iron sulfate heptahydrate, 63 ml of acetic acid, diluted 1:3, 125 g of sucrose, 1.25 ml of ethanol, 120 ml of distilled water. Solution 2 is the seed, namely particle silver metal obtained in the recovery of silver ions in iron II.

Solution 3. 252 g of dihydrate oxalic acid, 4000 ml of distilled water.

Solution 4. 305 g of iron sulfate heptahydrate, 1500 ml of distilled water.

Then the prepared solutions are mixed in the following order: a solution of 2 enter solution 1. The mixture and the solution 4 is added to solution 3. Mixing of the solutions carried out with stirring for 30 minutes the resulting suspension defend for 2 h and filtered. The precipitate is washed with hot water to remove sucrose, and then 200 ml of acetone. The obtained powder of the metal oxalate is dried in air at room temperature and then thermally decompose in robaut argon. The muffle is placed in a thermal oven. Termovosstanovleniyu samples are in the environment of hydrogen for 4 h in the temperature range 220 -400oC. When cooled heat-treated samples blow them first with argon, then air. As a result of implementation of the proposed method, the obtained product is a ferromagnetic powder Fe-Ag particles which have a high degree of dispersion l of 0.15 to 0.15 microns, having a hydrophilic surface, as evidenced by the heat of wetting Q 1000,5 erg/cm2, corrosion resistance that is characterized by the almost constancy of the magnetic properties of Hc320 a; K 0,236 -0,237 and content of metallic iron 58 wt. measured during 6 months of storage of the powder Fe-Ag at room temperature without any precautions: can withstand the temperature sterilization 100 120oC. When the magnetization in a constant magnetic field from 4 to 120 kA/m powder Fe Ag acquires bactericidal properties, manifested effectively when exposed to Pseudomonas aeruginosa Preudomanas aeruginosa zone of growth inhibition of 15 to 30 mm

Thus, the proposed method provides receiving ferromagnetic powder Fe-Ag. The resulting powder has particles of a high degree thesis/cm2, corrosion resistance that is characterized by the almost constancy of the magnetic properties and the content of metallic iron, measured periodically during 6 months of storage of the powder Fe-Ag at room temperature without any precautions that can withstand the temperature sterilization 100 120oC.

Comparative analysis shows that the powders obtained by the proposed method

exceed the powders obtained by a known method;

for corrosion resistance by about 20%

dispersity 10 times.

It should be noted that the powder Fe-Ag acquires new properties:

plate-like particle shape;

hydrophilic surface;

withstands heat sterilization 100 120oC that meets medicine and biology. These properties are not attained, the powder obtained by a known method.

The advantage of the proposed method is that the powder Fe-Ag for magnetization in a constant magnetic field from 4 to 120 kA/m becomes bactericidal properties, manifested effectively when exposed to Pseudomonas aeruginosa /zone growth delay of 15 to 30 mm, while the powder obtained by spanopoulou powder iron-silver, including the recovery of salts of iron and silver, wherein the pre-exercise preparation centers of crystallization by recovery in a solution of silver ions ions of divalent iron with subsequent deposition on the particles of silver oxalate iron, and recovery is carried out by heat treatment of the obtained particles in a reducing environment.

2. The method according to p. 1, characterized in that the deposition of oxalate of iron is carried out at 5 to 10oC.


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