CN101607722B - Method for synthesizing magnesium hydrate hexagonal nano-flake - Google Patents

Abstract

The invention discloses a method for synthesizing a magnesium hydrate hexagonal nano-flake, which comprises the following steps: dissolving certain mol of magnesium nitrate and hydrazine hydrate into deionized water, stirring the mixture sufficiently to form a white precipitate , putting the prepared solution into an autoclave with the filling degree of 80 to 90 percent, and processing the prepared solution at a temperature of between 150 and 200 DEG C for 6 to 24 hours; and finally, centrifuging and drying the well-processed solution to obtain a regular magnesium hydrate hexagonal nano-flake. The method uses the hydrazine hydrate as a mineralizing agent without the assistance of any complexing agent or surfactant to achieve the synthesis of the magnesium hydrate hexagonal nano-flake with a regular shape, and the nano-flake has the diameter of about 500 nanometers and the thickness of about 40 nanometers, and has a hexagonal flaky structure, uniform grain size and good dispersity. The method has certain significance for synthesizing magnesium hydrate nano-flakes industrially.

Description

A kind of synthetic method of magnesium hydrate hexagonal nano-flake

Technical field

The present invention relates to a kind of synthetic method of magnesium hydrate hexagonal nano-flake.

Background technology

The magnesium hydroxide function is extensive, as fire retardant have concurrently fire-retardant, press down functions such as cigarette, resistance drip, antiacid and filling, and itself is nonpoisonous and tasteless, does not produce toxic gas and etchant gas during burning, does not corrode mould, does not produce secondary pollution.Polymkeric substance such as PP, PA especially suitable and that processing temperature is high are used.Ordinary hydrogen magnesium oxide mostly is hexagonal structure or metamict crystals, maximum length is generally less than 5 with the ratio of minimum length in its crystal fragment, and the distortion value in (101) orientation is bigger, this makes when it is filled into when going in the plastics as fire retardant, physical strength influence to material is very big, especially shock strength and elongation descend a lot, and the processing flowability of resulting resin compound when melt-forming worsens simultaneously, and crazing usually appears in the products appearance after the moulding.Adopt nano-sized magnesium hydroxide to do fire retardant and can effectively avoid above-mentioned defective.

Nano-sized magnesium hydroxide can also medically also can be used as acid inhibitor etc. in chemical industry as catalyzer and make the raw material such as compound, glass-ceramic of other magnesium.Because magnesium hydroxide is the very strong compound of a kind of surface polarity, ordinary method synthetic product often is easy to reunite between big, the particle of specific surface area, dispersiveness and intermiscibility when directly influence is added in the polymer, influence the processing characteristics of matrix material, how to utilize simple, low cost process on a large scale the good magnesium hydroxide of processability just becoming the focus of people's growing interest.The method for preparing nano material commonly used has: synthetic methods such as direct precipitation method, sluggish precipitation, hypergravity and hydrothermal method.Wherein simple, and cost is low, output is big, be easy to advantage such as control with hydro-thermal technology, become a kind of effective ways that prepare nano material at present.Tradition Hydrothermal Preparation magnesium hydroxide generally is that mineralizer synthesizes magnesium hydroxide (Y.Ding, G.T.Zhang, H.Wu with sodium hydroxide, B.Hai, L.B.Wang, Y.T.Qian, Chem.Mater., 13,435-440 (2001)), but this method need be added certain dispersion agent, and it is inhomogeneous that it has the resultant particles dispersed, shortcomings such as out-of-shape (Y.D.Li, M.Sui, Y.Ding, G.H.Zhang, J.Zhuang, C.Wang, Adv.Mater.12 (11) (2000) 818).The novel hydro-thermal technology that this paper proposes as mineralizer, need not the auxiliary of any complexing agent or tensio-active agent with hydrazine hydrate, has realized magnesium hydrate hexagonal nano-flake synthetic of regular shape, and the synthetic magnesium hydroxide nanometer sheet of industry is had certain meaning.

Summary of the invention

The object of the present invention is to provide a kind of synthetic method of magnesium hydrate hexagonal nano-flake, be to be reactant with magnesium nitrate, hydrazine hydrate, synthetic by hydrothermal method, need not the auxiliary of any complexing agent or tensio-active agent, realized magnesium hydrate hexagonal nano-flake synthetic of regular shape.

The technical solution used in the present invention step is as follows:

1) magnesium nitrate is dissolved in the deionized water, the volumetric molar concentration of control magnesium nitrate is 0.01～0.2 mol, stirs;

2) adding mole number under the magnetic agitation in above-mentioned solution is the hydrazine hydrate (N of 1.2～3 times of mole numbers of magnesium nitrate ₂H ₄H ₂O), form white precipitate, continue to stir;

3) solution that will finally prepare is put into the teflon-lined autoclave, and compactedness is 80～90%, handles 6～24 hours down at 150～200 ℃;

4) with the solution centrifugal of handling well, the dry magnesium hydrate hexagonal nano-flake that has just obtained regular shape.

The beneficial effect that the present invention has is:

The present invention is to be reactant with the magnesium nitrate, hydrazine hydrate is a mineralizer, the magnesium hydrate hexagonal nano-flake that synthesizes regular shape by simple hydro-thermal technology, avoid the traditional water by the use of thermal means and need add the auxiliary of complexing agent or tensio-active agent, about 500 nanometers of this nanometer sheet diameter, about 40 nanometers of thickness are the hexagonal flake structure, uniform particle diameter has dispersed preferably.

Description of drawings

Fig. 1 is the XRD figure spectrum of embodiment 1 products therefrom;

Fig. 2 is the stereoscan photograph of embodiment 1 products therefrom;

Fig. 3 is the original position XRD figure spectrum between 100～370 ℃ in the embodiment 2 gained samples, wherein (a) 100 ℃; (b) 200 ℃; (c) 300 ℃; (d) 330 ℃; (e) 370 ℃;

Fig. 4 is the transmission electron microscope photo of embodiment 3 gained samples;

Fig. 5 is a stereoscan photograph of implementing Comparative Examples gained sample.

Embodiment

Embodiment 1:

Get 1.58 gram magnesium nitrate (Mg (NO ₃) ₂2H ₂O) be dissolved in 80 ml deionized water, the magnesium nitrate volumetric molar concentration is 0.107 mol, stirs after 3 minutes, adds 0.642g hydrazine hydrate (N ₂H ₄H ₂O, purity 80%), the hydrazine hydrate volumetric molar concentration is 0.1284 mol, forms white precipitate, continues to stir 8 minutes, and the above-mentioned solution for preparing is put into the teflon-lined autoclave, and compactedness is 80%, and the liner volume is 100 milliliters.This solution was handled 24 hours down at 150 ℃, the solution centrifugal of handling well, drying, obtained the magnesium hydrate hexagonal nano-flake of regular shape.Fig. 1 is the XRD figure spectrum of this product, each diffraction peak position and magnesium hydroxide (Mg (OH) among the figure ₂) standard card (JCPDS No.07-0239) unanimity, illustrate that the gained sample is the Mg (OH) of single phase ₂Fig. 2 (a), 2 (b) are the stereoscan photograph of this routine products therefrom, product is the hexagonal flake structure as can be seen from Fig. 2 (b), about 500 nanometers of diameter, about 40 nanometers of thickness, particle diameter is even, good dispersity.

Embodiment 2:

0.1472 gram magnesium nitrate is dissolved in 80 ml deionized water, and the magnesium nitrate volumetric molar concentration is 0.01 mol, stirs after 4 minutes, adds 0.15 gram hydrazine hydrate (N ₂H ₄H ₂O, purity 80%), the hydrazine hydrate volumetric molar concentration is 0.03 mol, forms white precipitate, continues to stir 10 minutes, and the above-mentioned solution for preparing is put into the teflon-lined autoclave, and compactedness is 80%, and the liner volume is 100 milliliters.This solution was handled 15 hours down at 200 ℃, the solution centrifugal of handling well, drying.Fig. 3 is the original position XRD figure between 100～370 ℃ of this products, as can be seen from the figure, at 2 θ is that obvious diffraction peak is arranged about 38 °, when temperature was lower than 330 ℃, along with temperature raises, this diffraction peak intensity weakened gradually, when temperature rises to 370 ℃, this diffraction peak disappears, and the result shows that dehydration reaction has taken place magnesium hydroxide between 330 ℃ to 370 ℃.Magnesium hydroxide is heated the heat that dehydration reaction absorbs 0.77kJ/g takes place, thereby has suppressed the rising of temperature, reduces combustionvelocity, and produced simultaneously water vapour can dilute inflammable gas, plays effective fire retardation.

Embodiment 3:

3.128 gram magnesium nitrates are dissolved in 85 ml deionized water, and the magnesium nitrate volumetric molar concentration is 0.2 mol, stirs after 5 minutes, adds 2.125 gram hydrazine hydrate (N ₂H ₄H ₂O, purity 80%), the hydrazine hydrate volumetric molar concentration is 0.4 mol, forms white precipitate, continues to stir 12 minutes, and the above-mentioned solution for preparing is put into the teflon-lined autoclave, and compactedness is 90%, and the liner volume is 100 milliliters.This solution was handled 6 hours down at 200 ℃, the solution centrifugal of handling well, drying.Fig. 4 is the transmission electron microscope photo and the electron diffraction pattern figure (illustration) of sample, can clear observe out from Fig. 4, and product is that size distribution is laminar uniformly.Analyzing as can be known from electron diffraction pattern, product has hexagonal structure.

Comparative Examples:

1.58 gram magnesium nitrates are dissolved in 80 ml deionized water, the magnesium nitrate volumetric molar concentration is 0.107 mol, stir after 5 minutes, add 0.41g sodium hydroxide, the sodium hydroxide volumetric molar concentration is 0.1284 mol, forms white precipitate, continue to stir 10 minutes, the above-mentioned solution for preparing is put into the teflon-lined autoclave, and compactedness is 80%, and the liner volume is 100 milliliters.This solution was handled 24 hours down at 150 ℃, the solution centrifugal of handling well, drying.Fig. 5 is the stereoscan photograph of this routine products therefrom, magnesium hydroxide particle out-of-shape as can be seen, and be easy to reunite.

Claims (1)

1. the synthetic method of a magnesium hydrate hexagonal nano-flake is characterized in that the step of this method is as follows:

1) magnesium nitrate is dissolved in the deionized water, the volumetric molar concentration of control magnesium nitrate is 0.01～0.2 mol, stirs;

2) in above-mentioned solution, add under the magnetic agitation mole number be the hydrazine hydrate of 1.2～3 times of mole numbers of magnesium nitrate as mineralizer, form white precipitate, continue to stir;

3) solution that will finally prepare is put into the teflon-lined autoclave, and compactedness is 80～90%, handles 6～24 hours down at 150～200 ℃;

4) with the solution centrifugal of handling well, the dry magnesium hydrate hexagonal nano-flake that has just obtained regular shape.

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