A method of obtaining a film of polymer nanocomposite

 

(57) Abstract:

The invention relates to the production of a film of polymer nanocomposite containing inorganic magnetic component, and can be used to create a magnetic recording media with high recording density, and magnetic sensors. Method for obtaining a film of polymer nanocomposite processing polymeric composition consisting of polyvinyl alcohol, water and mixtures of water-soluble salts of three - and ferrous iron at first, at least one water-soluble dialdehyde (crosslinking agent) at a pH of from 0 to 3. This is followed by a treatment with an aqueous solution of alkali with the introduction of alkali in quantity, at least, ensuring complete reaction of the alkaline hydrolysis of a mixture of iron salts with the formation of a mixture of magnetite and maghemite. The technical result is to obtain polymer nanocomposite with a wide range of compositions, and the phase can be locked and super-paramagnetic state.

The invention relates to the field of polymer film nanocomposite based on polyvinyl alcohol (PVA) having magnetic properties, goods the of eremita-Fe2O3). Such compositions can be used to create a magnetic recording media for high density recording and information storage and magnetic sensors. This common term "nanocomposite" is commonly used to microheterogeneous highly dispersed systems in the solid state of aggregation, containing two or more components, with the particle size of the dispersed phase, not exceeding ~ 100 nanometers (nm), which are distributed in a continuous dispersion medium, called the matrix.

It should be noted that nanoparticles of magnetite and maghemite in the polymeric matrix can be in two different magnetic States - blocked and superparamagnetic particles. Under super-paramagnetic state in the conventional sense of the term refers to the system state magnetic ordering of the nanoparticles at a temperature above the blocking temperature TBwhen this system behaves as a paramagnet. The blocked state means the state of the system magnetically ordered nanoparticles below TBwhen this system behaves like a ferromagnet, if the dispersed phase. ferromagnetic (I. P. Suzdalev, A. S. plachinda, C. N. Submitted by Jose Marcos, Y. C. Maximov, S. I. RAM the n magnetics. V. 29. 6. P. 2658, 1993). The analysis of the magnetic state of the particles of the nano-phase iron oxide has traditionally carried out by the method of gamma-resonance (mössbauer) spectroscopy in the presence or absence in the spectra of the magnetic hyperfine structure (sextet) or quadrupole doublet, characteristic, respectively, for States below and above TBand by measuring the magnetization in the presence or absence of magnetic hysteresis and related residual magnetization. Nanocomposite in the blocked state is promising for the creation of magnetic recording media, nanocomposite in super-paramagnetic state can be used in the development of magnetic sensors based on not too long ago discovered and intensively suceuses at the present time the so-called giant effect (negative or positive) magnetoresistance (GMR effect). The GMR phenomenon, characteristic of nanosystems in the super-paramagnetic state is a strong change in the electrical resistance of the composition (>1%) when overlaid magnetic field (A. E. Berkowitz, Phys. Rev. Lett. V. 68. P. 3745, 1992; A. E. Varfolomeev, A. C. Wolf, D. Y. Godovsky, G. A. Kapustin, M. A. Moskvin. JETP letters. So 67, vol. 1. S. 37, 1998).

Isvisit-Fe2O3and magnetite Fe3O4- with a particle size of 5.8 nm and the content of the dispersed component to 1.8% in the super-paramagnetic at room temperature condition by watering aqueous solution of PVA with a Sol of the above oxides, previously obtained by the alkaline hydrolysis of an aqueous solution of a mixture of three salts and ferrous iron in the presence of PVA (H. Pardoe, W. Chua-anusorn, T. G. St. Pierre, J. Dobson. J. Magn. Magn. Mater. V. 225. P. 41. 2001). The GMR effect in the resulting compositions were not studied.

A method of obtaining a film of polymer nanocomposite based on PVA and magnetic iron oxide of maghemite with a particle size of 5.2 to 10.7 nm and the content of the dispersed component to 21 vol.% by irrigation water solution of PVA with a Sol of maghemite, followed by drying. An aqueous solution of PVA - magamit was obtained by mixing aqueous solutions of PVA and Zola of maghemite previously obtained by the alkaline hydrolysis of an aqueous solution of a mixture of three salts and ferrous iron with the subsequent patsatsia formed precipitate of iron oxide in an acidic environment (P. Prene, E. Trong, J-P. Jolivet, J. Livage, R. Cherkaoui, M. Nogues, J-L. Dormann, D. Fiorani. IEEE Trans. on magnetics. V. 29. 6. P. 2658, 1993). The GMR effect in the received nanocomposite has not been investigated. All nanocomposite (except one) when commessage component of 0.53% received in a blocked state.

Closest to the claimed is a method of obtaining a film of polymer nanocomposite processing polymeric composition consisting of a chemically unstitched PVA, water and mixtures of water-soluble salts of three (Fl3) and ferrous iron (FeCl2) in a molar ratio from 1 to 2, respectively, in an aqueous solution of alkali (caustic soda) with the introduction of alkali in quantity, at least, ensuring complete reaction of the alkaline hydrolysis of a mixture of iron salts with the formation of a mixture of magnetite and maghemite, allowing to obtain a film of the polymer nanocomposite with a maximum content of iron oxide 24 vol.%, at room temperature super-paramagnetic state (A. E. Varfolomeev, A. C. wolf, D. Y. Godovsky, G. A. Kapustin, M. A. Moskvin. JETP letters. So 67, vol. 1. S. 37, 1998 prototype). In the resulting nanocomposite detected by the GMR effect.

The disadvantages of this method are the poor mechanical properties of chemically unstitched compositions in the aquatic environment and associated challenges of their receipt, the relatively low content of iron oxides in the composition and the impossibility of obtaining nanocomposite with the dispersed phase in the locked sostojani.lechenie film polymer nanocomposite, characterized by an average particle size of from 10 to 20 nm in the presence of a wide range of concentrations of the dispersed component (up 47%), in which the phase can be locked and super-paramagnetic, and superparamagnetic particles in the state polymer nanocomposite has the property of strong changes its electrical resistance when overlaid magnetic field (GMR effect).

This technical result is achieved in that in the method of obtaining a film of polymer nanocomposite processing polymeric composition consisting of PVA, water and mixtures of water-soluble salts of three - and ferrous iron, the aqueous alkali solution with the introduction of alkali in amount of at least ensure complete reaction of the alkaline hydrolysis of a mixture of iron salts with the formation of a mixture of magnetite and maghemite, before treatment with the aqueous solution of alkali polymer composition is treated with at least one water-soluble dialdehyde at a pH of from 0 to 3 in the presence of acid as acidifying agent.

As the water-soluble dialdehyde can be used, for example, glyoxal ONSE (TH), succinoyl dialdehyde OHC(CH

Under these conditions, the processing composition, at least one dialdehyde can be conducted at room and at different temperatures. Processing can be performed in a wide range of pH values, for example from 0 to 3, preferably 1. In these conditions, the quantity of injected water-soluble dialdehyde in relation to the amount of PVA and the concentration of MDA in aqueous solution may vary within wide limits, provides different percentage of crosslinking of hydroxyl groups of PVA.

As the original PVA can be used any unstitched polymer in a wide range of molecular weights.

As a researcher who Oli iron, for example chlorides, sulfates, nitrates and other, preferably chlorides.

As the alkali can be used any water-soluble base, such as caustic soda, caustic potash, ammonia, and others, or their mixture.

The number of input mixture of water-soluble salts of three - and ferrous iron in relation to the number of PVS may vary within wide limits, thus providing different content of magnetic iron oxides in the resulting polymer nanocomposite.

The amount of water in the composition before treatment with the aqueous solution of alkali can be varied within wide limits, preferably from 5 to 97 wt.% with respect to the total weight of PVA and water. These limits are defined as the concentration used for the preparation of compositions of aqueous solutions of PVA and iron salts, and the presence or absence of a stage of drying the composition after its treatment with an aqueous solution of dialdehyde.

The amount of added alkali in aqueous solution it is necessary to take at least ensure complete reaction of the alkaline hydrolysis of a mixture of three salts and ferrous iron with the formation of a mixture of magnetite and maghemite in the polymeric matrix, or h is preferably from 6 to 10 mol/L.

The molar ratio of salt to three - and ferrous iron in aqueous solution can be varied within wide limits, preferably from 0.5 to 2.

The thickness of the film nanocomposite can be varied in a wide range from 1 to 300 μm (film from 1 to 5 μm on the substrate, which can be used, for example, glass or quartz plate, and the substrate covered with a conductive layer of ITO - mixed oxide of indium and tin; the film is from 5 to 300 μm in a free, i.e. associated with the substrate).

The treatment of the polymer composition of at least one water-soluble dialdehyde at a pH of from 0 to 3 in the presence of acid as acidifying agent prior stage of processing aqueous alkali solution allows to obtain a polymer nanocomposite with a wide range of compositions to 47% vol. as in blocked and superparamagnetic particles, and superparamagnetic particles in a state of composition show the GMR effect. If a different sequence of the above operations to get nanocomposite having a set of such properties is not possible.

Example 1

1 g of PVA with a molecular mass M= 6104dissolve the e add 10 ml of an aqueous solution, containing 2.38 g (8,810-3mole) Fl36N2Oh and 0.88 g (4,410-3mole) FeCl2H2O (molar ratio Fe+3/Fe+2=2). The resulting solution was thoroughly stirred for 20 min, then the mixture quickly add a mixture of 5 ml of water, 0.25 ml of 96% sulfuric acid and 2,810-2g (2,810-4mole) of glutaric dialdehyde (pH of the solution is equal to 1). The resulting mixture was thoroughly stirred for 10 min, then poured into a plastic Petri dish with a diameter of 9.7 see After 1 h the solution flows gelation throughout the volume of the polymer composition with the formation of transparent jelly, painted with iron salts in the yellow-orange color. The above number of DG has a 5% blending PVA with education acetylenic links. The water content relative to the total weight of PVA and water in the resulting gel is 97%. The obtained gel in a Petri dish treated with 50 ml of 10-molar aqueous solution of sodium hydroxide. Upon contact of the polymer composition with the aqueous alkali solution gel is painted in black color, which is caused by the occurrence of in situ reaction of the alkaline hydrolysis of a mixture of iron salts in polymer gel with the formation of iron oxides. The Petri dish with the reaction system the alkali drained and the resulting polymer composition, containing the phase iron oxides, thoroughly washed with Petri dish with distilled water for 24 h, after which the pH of the resulting nanocomposite becomes 6.5. The resulting nanocomposite dried in a Petri dish for 4 days at room temperature, then dried and the sample is removed from the Petri dishes. Get smooth film polymer nanocomposite thickness of 110 μm, intensely colored in black, with a content of iron oxide 18 vol.%, with a particle size of iron oxides, a particular method of scattering of x-rays, 18-20 nm. According to mössbauer spectroscopy and magnetization measurements disperse phase of iron oxide in the obtained nanocomposite at room temperature is in a blocked state. This is indicated by the presence of hyperfine structure (sextet) in mössbauer spectra, as well as the value of the residual magnetization of the obtained sample, at 6.7 S2/kg.

Example 2

Prepare the PVA gel containing a mixture of three salts and ferrous iron, in the same way as in example 1. Then the gel is dried in a Petri dish at room temperature for 4 days. The dried smooth, transparent, colored geldi separated from the Petri dishes and immersed in 50 ml of 6 molar aqueous solution of alkali (sodium hydroxide). When this film immediately acquires a black color due to the formation of nano-phase iron oxides. After 20 h, the film is removed from the alkali solution, washed with distilled water for 24 h until neutral, then dried between sheets of filter paper under the load. The thickness of the resulting film nanocomposite is 105 μm, the content of iron oxides in the composition of 17 vol.%, the average particle size of the nano-phase iron oxides, a specific method of scattering of x-rays is 10 nm. According to mössbauer spectroscopy and magnetization measurements disperse phase of iron oxide in the obtained nanocomposite at room temperature is in the super-paramagnetic state. This is indicated by the presence in the mössbauer spectra of the sample Central quadrupole doublet, and the absence of hysteresis in the magnetization curve and the associated residual magnetization.

The resulting nanocomposite characterized by the presence of the negative effect of giant magnetoresistance average of 10-12% in the 10 kilooersted (EC) when the absolute value of the change in resistance 2108Ohms, and the value of the magnetoresistive senses the/SUB> = 1105dissolved in 19 ml of distilled water and get a 5% aqueous solution of PVA. To the resulting solution in the beaker add 12 ml of an aqueous solution containing 1.2 g (310-3mole) of Fe2(SO4)3and 1.67 g (610-3mole) FeSO47H2O (molar ratio Fe+3/Fe+2= 1). The resulting solution was thoroughly stirred for 30 min, then the mixture quickly add a mixture of 2.3 ml of water, and 2.7 ml of concentrated hydrochloric acid and 110-2g (1,710-4mol) of glyoxal (pH 0). The resulting mixture was thoroughly intensively stirred for 5 min, then poured into a plastic Petri dish with a diameter of 9.7 see After 30 min the solution flows gelation throughout the volume of the polymer composition with the formation of transparent jelly, painted with iron salts in the yellow-orange color. The above number TH provides 3% blending PVA with education acetylenic links. The water content relative to the total weight of PVA and water in the resulting gel is 97%. The obtained gel in a Petri dish treated with 7.5 ml of 4 molar aqueous solution of sodium hydroxide for 20 hours (the minimum amount required for complete hydrolysis of the Sol mixture is get a smooth film polymer nanocomposite thickness of 120 μm, intensely colored in black, with a content of iron oxide 19%. Structural and magnetic characteristics of the obtained nanocomposite the following: the particle size of nano-phase iron oxides 18-20 nm, the residual magnetization of 6.0 S2/g, in mössbauer spectra present the hyperfine structure (sextet), which indicates the locked state of the iron oxides in the sample.

Example 4

1 g of PVA with a molecular mass M= 5104dissolved in 11.5 ml of distilled water and get 8% aqueous solution of PVA. To the resulting solution in a beaker, add 20 ml of an aqueous solution containing 9 g (2,610-2mol) Fe(NO3)36N2O and 6 g (2,610-2mol) Fe(NO3)26N2(The molar ratio of Fe+3/Fe+2=1). The resulting solution was thoroughly stirred for 60 min, then the mixture quickly add a mixture of 5 ml of water, with 0.27 ml of concentrated hydrochloric acid and 1,910-2g (2,2410-4mole) actinophage dialdehyde (pH of the solution is equal to 1). The resulting mixture was thoroughly stirred for 15 min, then poured into a plastic Petri dish with a diameter of 9.7 see After 2 h the solution flows gelation throughout the volume of polymer clay is related to the amount of DM provides 4% blending PVA with the formation of the gel, contains 97% water relative to the total weight of PVA and water. The obtained gel in a Petri dish treated with a mixture of 50 ml of 10-molar aqueous sodium hydroxide solution and 50 ml of 5 molar sodium hydroxide solution for 20 h in a closed vessel, then the alkali solution is drained and the resulting polymer composition comprising a phase iron oxides, thoroughly washed with Petri dish with distilled water for 48 h until neutral. The obtained gel-like nanocomposite dried in a Petri dish for 5 days at room temperature, then dried and the sample is removed from the Petri dishes. Get smooth film polymer nanocomposite thickness of 280 μm, intensely colored in black, with a content of iron oxide 47% vol. and the particle size of nano-phase specific method of scattering of x-rays, 15-18 nm. According to mössbauer spectroscopy and magnetization measurements disperse phase of iron oxide in the obtained nanocomposite at room temperature is in a blocked state. This is indicated by the presence of hyperfine structure (sextet) in mössbauer spectra, as well as the value of the residual magnetization of the obtained sample of 8 Am2/knymi water and get a 6% aqueous solution of PVA. To the resulting solution in the beaker add 3.3 ml of an aqueous solution containing 0,051 g (1,8710-4mole) Fl36N2Oh and 0.104 g g (3,7310-4mole) FeSO47H2O (molar ratio Fe+3/Fe+2= 0,5). The resulting solution was thoroughly stirred for 20 min, then the mixture quickly add a mixture of 5 ml of water, 0.05 ml of 80% acetic acid and the mixture 1,710-2g (1,710-4mol) DG and 110-2g (1,710-4mole), the pH of the solution is equal to 3. The resulting mixture was thoroughly stirred for 10 min, then poured into a Petri dish. After 3 h the solution flows gelation throughout the volume of the polymer composition with the formation of a light yellow transparent jelly. The above number of dialdehydes provides 6% blending PVA with education acetylenic links. The water content relative to the total weight of PVA and water in the resulting gel is 96%. The obtained gel in a sealed Petri dish treated at room temperature with 10 ml of 6 molar aqueous solution of ammonia for 20 hours of the polymeric composition acquires a reddish-brown color due to the formation of nano-phase iron oxides, then a solution of ammonia drained and received the profiled water for 24 h until neutral. The resulting nanocomposite dried in a Petri dish for 3 days at 30oWith, then the sample is removed from the Petri dishes. Get smooth film polymer nanocomposite thickness of 95 μm, painted in red-brown color, with a content of iron oxide 1%, with a particle size of nano-phase iron oxides 17-19 nm. According to mössbauer spectroscopy and magnetization measurements of the dispersed phase in the received nanocomposite at room temperature is in the super-paramagnetic state. This is indicated by the absence of magnetic hysteresis and residual magnetization, and the mössbauer spectra of the obtained sample Central quadrupole doublet.

Example 6

1 g of PVA with a molecular mass M= 6104dissolved in 19 ml of distilled water and get a 5% aqueous solution of PVA. To the resulting solution in a beaker, add 10 ml of an aqueous solution containing 2.38 g (8,810-3mole) Fl36H2Oh and 0.88 g (4,410-3mole) Fl24H2(The molar ratio of Fe+3/Fe+2=2). The resulting mixture was thoroughly stirred for 10 min, and then 3.5 ml of the mixture was poured into a plastic Petri dish with a diameter of 9.7 cm (or neckarau composition with the formation of transparent jelly. The obtained gel in a Petri dish treated with 10 ml of 10-molar aqueous sodium hydroxide solution, and then the Petri dish with the reaction system is covered with a lid to prevent evaporation of water and leave for 20 h at room temperature, after which the alkali solution is drained and the resulting polymer composition comprising a phase iron oxides, thoroughly washed with Petri dish with distilled water for 24 hours of Received nanocomposite dried in a Petri dish for 1 day at room temperature, then dried and the sample is removed from the Petri dishes. Get a smooth film of transparent polymer nanocomposite, painted in red-brown color with a thickness of 10 μm with a content of iron oxide 18%. Structural and magnetic characteristics of the obtained nanocomposite the following: the particle size of nano-phase iron oxides 18-20 nm, the residual magnetization of 5.8 S2/kg, in mössbauer spectra present the hyperfine structure (sextet), which indicates the locked state of the iron oxides in the sample.

Example 7

1 g of PVA with a molecular mass M= 6104dissolved in 19 ml of distilled water and get a 5% aqueous solution of PVA. To the resulting solution in x is 88 g (4,410-3mole) Fl24H2(The molar ratio of Fe+3/Fe+2=2). The resulting solution was thoroughly stirred for 20 minutes and Then 3 ml of the obtained mixture of 0.52 ml of a mixture consisting of 5 ml of water, 0.25 ml of 96% sulfuric acid and 2,810-2g (2,810-4mole) of glutaric dialdehyde (pH of the resulting solution is equal to 1). The resulting mixture was thoroughly stirred for 5 minutes 1 ml of the mixture to collect in a pipette and put on carefully-fat glass substrate (glass plate 3 cm in diameter) set in a horizontal position on a special centrifuge to obtain thin films, and then centrifuge include (mode - 5000 rpm for 1 min). After turning off the centrifuge glass substrate coated with the liquid mixture is removed and left at room temperature. After 2 h the glass plate with the film of the dried gel containing a mixture of salts of iron, dipped for 15 min in 20 ml of a 10 molar solution of sodium hydroxide. Then the glass plate with the polymer nanocomposities washed with distilled water for 1 h and allowed to dry completely at room temperature. The thickness of the obtained film nanocomposite on the glass substrate, a certain method the p particles of the dispersed phase is 10 nm. According to mössbauer spectroscopy (the presence in the spectrum of the Central quadrupole doublet) phase of iron oxide in the obtained nanocomposite at room temperature is in the super-paramagnetic state.

A method of obtaining a film of polymer nanocomposite processing polymeric composition consisting of polyvinyl alcohol, water and mixtures of water-soluble salts of three - and ferrous iron, the aqueous alkali solution with the introduction of alkali in quantity, at least, ensuring complete reaction of the alkaline hydrolysis of a mixture of iron salts with the formation of a mixture of magnetite and maghemite, characterized in that before the treatment with the aqueous solution of alkali polymer composition is treated with at least one water-soluble dialdehyde at a pH of from 0 to 3 in the presence of acid as acidifying agent.

 

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