JP6654637B2 - Stabilization of hexagonal boron nitride nanoparticles - Google Patents

Description

  The present disclosure relates to a stabilizing composition comprising hexagonal boron nitride nanoparticles.

  Heat transfer fluids are used in many applications, especially as coolants or antifreezes. Examples of the use of heat transfer fluids include excess heat from stationary and self-propelled internal combustion engines, heat generated from electric motors and generators, processing and condensation heat (eg, in smelters and steam generation plants), electronics. Removal or exchange of heat from equipment or heat generated by the fuel cell system. In each application, the thermal conductivity and heat capacity of the heat transfer fluid is important.

  Historically, water has been the preferred fluid when considering heat transfer. However, water is often mixed with freezing point depressants (eg, alcohols or salts such as glycols) to obtain antifreeze properties. Such mixtures exhibit reduced heat transfer capabilities compared to pure water, but are still preferred over liquids such as organic oils, silicone oils, or synthetic esters.

  A heat transfer fluid having higher thermal conductivity is desired. Although water-based fluids and water / glycol-based fluids dominate the market, they do not always provide sufficient heat transfer performance. In particular, energy efficient applications and equipment require the development of heat transfer fluids with significantly higher thermal conductivity than those currently available. Fluids with suspended solids may exhibit higher thermal conductivity. Solids have a higher thermal conductivity than fluids. For example, solid copper, aluminum, copper oxide, and silicon oxide each have 401 W / m. K, 237 W / m. K, 76.5 W / m. K, and 1.38 W / m. It has a thermal conductivity of K. In contrast, the fluid water, monoethylene glycol, and typical oil each have 0.613 W / m. K, 0.252 W / m. K, and 0.107 W / m. It has a thermal conductivity of K. Since Maxwell's theoretical study was published in 1881, a number of theoretical and empirical studies have been performed on the effective thermal conductivity of dispersions containing solid particulates.

By incorporating the nanoparticles in the fluid, higher thermal conductivity can be provided. It has been proposed to use nanoparticles in fluids such as water, ethylene glycol, and engine oil to create a new type of processing fluid (nanofluid) with improved heat transfer capabilities. S. U. -S. See Choi, ASME Society, San Francisco, California, Nov. 12-17, 1995. Al ₂ O ₃ and a thermal conductivity measurement of the fluid containing CuO nanoparticles have been reported. S. U. -S. See Choi et al., ASME Transactions 280, 121, May 1999. Nanofluids containing only small amounts of nanoparticles have a significantly higher thermal conductivity compared to the same fluid without nanoparticles.

  However, dispersed nanoparticles, including hexagonal boron nitride nanoparticles, have poor stability, hindering the application of nanofluids as heat transfer fluids. So far, stability studies have focused on the choice of particle size and particle size distribution, as well as dispersion techniques.

S. U. -S. Choi, ASME Society, San Francisco, California, November 12-17 S. U. -S. Choi et al., ASME Transactions 280, 121, May 1999.

  Disclosed herein are stable compositions comprising hexagonal boron nitride nanoparticles, methods for preparing the stabilized compositions, and methods for exchanging heat using the compositions as heat transfer fluids. Is disclosed.

In a first embodiment, the composition comprises a continuous phase selected from the group consisting of water, an alcohol, and a mixture of water and an alcohol; hexagonal boron nitride nanoparticles dispersed in the continuous phase; and formula (I)

Or a salt thereof, wherein n is an integer of 50 to 200, and y is an integer of 20 to 200.

In a second embodiment, the composition comprises a continuous phase of water; hexagonal boron nitride nanoparticles dispersed in the continuous phase; and formula (I)

Or a salt thereof, wherein n is an integer of 50 to 200, and y is an integer of 20 to 200.

In one embodiment, the method for exchanging heat comprises: a. Generating heat in an automotive internal combustion engine; b. Flowing a stream to one side of a heat exchanger; c. Flowing the composition through another side of the heat exchanger; and d. Transfer of heat from the stream to the composition in a heat exchanger. In the method, the composition comprises a continuous phase selected from the group consisting of water, alcohol, and a mixture of water and alcohol; hexagonal boron nitride nanoparticles dispersed in the continuous phase;

Or a salt thereof, wherein n is an integer of 50 to 200, and y is an integer of 20 to 200.

  As used herein, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly indicates otherwise. .

In a first embodiment, the composition comprises a continuous phase selected from the group consisting of water, alcohol, and a mixture of water and alcohol; hexagonal boron nitride nanoparticles dispersed in the continuous phase; and formula (I)

Or a salt thereof, wherein n is an integer of 50 to 200, and y is an integer of 20 to 200.

In a second embodiment, the composition comprises a continuous phase of water; hexagonal boron nitride nanoparticles dispersed in the continuous phase; and formula (I)

Or a salt thereof, wherein n is an integer of 50 to 200, and y is an integer of 20 to 200.

  The compound having formula (I) is a triblock copolymer having a central hydrophobic block of polypropylene glycol surrounded by a hydrophilic block of polyethylene glycol. We believe that fluids containing hexagonal boron nitride nanoparticles exhibit increased thermal conductivity, but at the elevated temperatures typically encountered in heat transfer applications, such as about 70 ° C to 110 ° C or about 85 ° C. It was observed that the stability was not adequate between 0C and about 110C. We are surrounded by a hydrophilic block of polyethylene glycol in a continuous phase based on water, a continuous phase based on alcohol, or a continuous phase based on water / alcohol containing dispersed hexagonal boron nitride nanoparticles. It has been found that the incorporation of a triblock copolymer having a central hydrophobic block of polypropylene glycol can stabilize the dispersion of hexagonal boron nitride nanoparticles in a continuous phase at room and elevated temperatures. Thus, incorporation of the triblock copolymer can provide a composition that has not only significant thermal conductivity, but also improved stability. Thus, the composition is suitable for use as a heat transfer fluid.

  For example, the composition may be stable at room temperature for 12 hours. As another example, the composition can be stable for 12 hours at a temperature from about room temperature to about 85 ° C. As yet another example, the composition may be stable at a temperature from about 70 ° C to about 110 ° C or from about 85 ° C to about 110 ° C for 12 hours.

  Suitable salts of the compounds having formula (I) include alkali metal, ammonium and amine salts.

  The composition generally contains a large amount (ie, at least 80% by volume) of the continuous phase (ie, water, alcohol, or a mixture of water and alcohol). In one embodiment, the composition contains at least 85% by volume of the continuous phase. In another embodiment, the composition contains at least 90% by volume of the continuous phase. In a further embodiment, the composition contains at least 95% by volume of the continuous phase.

  If antifreeze properties are desired, alcohol acts as a freezing point depressant. If the continuous phase is an alcohol or a mixture of water and an alcohol, the alcohol may be a glycol. Glycols are ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, dipropylene glycol, tripropylene glycol, tetrapropylene glycol, pentapropylene glycol, hexapropylene glycol , Monoethylene glycol, or monopropylene glycol. Alternatively, the alcohol is selected from methanol, ethanol, propanol, butanol, furfurol, tetrahydrofurfuryl, ethoxylated furfuryl, dimethyl ether of glycerol, sorbitol, 1,2,6 hexanetriol, trimethylolpropane, methoxyethanol, and glycerin. You may. In one embodiment, methanol, ethanol, propanol, butanol, furfurol, tetrahydrofurfuryl, ethoxylated furfuryl, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, dipropylene Glycol, butylene glycol, glycerol, monoethyl ether of glycerol, dimethyl ether of glycerol, sorbitol, 1,2,6-hexanetriol, trimethylolpropane, methoxyethanol, or mixtures thereof are used.

  In certain embodiments, the continuous phase is a mixture of water and ethylene glycol. In another particular embodiment, the continuous phase is a mixture of water and ethylene glycol in a 50/50% by volume ratio.

  Hexagonal boron nitride nanoparticles are cylindrical in shape and their size can vary. Since hexagonal boron nitride nanoparticles have a columnar shape, their size is described by a combination of height and radius or diameter. For example, hexagonal boron nitride nanoparticles can have an average diameter of about 50 nm to about 350 nm, and an average height of about 5 nm to about 20 nm. In another example, hexagonal boron nitride nanoparticles can have an average sheet height of about 5 nm to about 20 nm, and an average sheet radius of about 50 nm to about 350 nm.

  The concentration of hexagonal boron nitride nanoparticles in the composition can vary. In one embodiment, the hexagonal boron nitride nanoparticles are present in the composition at a concentration of about 0.0001% to about 10% by volume. In another embodiment, the hexagonal boron nitride nanoparticles are present in the composition at a concentration of about 0.005% to about 0.5% by volume. In yet another embodiment, the hexagonal boron nitride nanoparticles are present in the composition at a concentration of about 0.05% to about 0.2% by volume.

  In compounds having formula (I), in one embodiment, n is an integer from 80 to 120 and y is an integer from 50 to 75. In certain embodiments, n is 100 and y is 65.

  The concentration of the compound having formula (I) in the composition may vary. In one embodiment, the compound having Formula (I) is present in the composition at a concentration from about 0.0001% to about 1% by volume. In another embodiment, the compound having Formula (I) is present in the composition at a concentration from about 0.2% to about 0.7% by volume. In certain embodiments, the compound having Formula (I) is present in the composition at a concentration of about 0.1% by volume.

  Neither the thermal conductivity nor the heat capacity of the composition is significantly affected by the presence of small amounts of common additives. Suitable additives include alkali metal salts as freezing point depressants, corrosion inhibitors, antiscalants, stabilizers, antioxidants, buffers, defoamers, dyes, or mixtures thereof. The composition may contain one or more additives in a total additive amount of about 0.01% to about 10% by weight. For example, one or more corrosion inhibitors may be present in the composition at a concentration of about 0.2% to about 10% by weight. Examples of alkali metal salts include salts of acids or mixtures of acids selected from the group consisting of acetic acid, propionic acid, succinic acid, betaine, and mixtures thereof. Examples of corrosion inhibitors include aliphatic carboxylic acids or salts thereof, aromatic carboxylic acids or salts thereof, triazoles, thiazoles, silicates, nitrates, nitrites, borates, phosphate molybdates, Or an amine salt. Examples of antioxidants include phenols such as 2,6-di-t-butylmethylphenol and 4,4'-methyl-en-bis (2,6-di-t-butylphenol); p, p-dioctyl Aromatic amines such as phenylamine, monooctyldiphenylamine, phenothiazine, 3,7-dioctylphenothiazine, phenyl-1-naphthylamine, phenyl-2-naphthylamine, alkylphenyl-1-naphthylamine, and alkyl-phenyl-2-naphthyl-amine And sulfur-containing compounds, such as dithiophosphates, phosphites, sulfides, and dithiometal salts such as benzothiazole, tin dialkyldithiophosphate, and zinc diaryldithiophosphate.

  The pH of the composition may be from about 7 to about 11.5. In one embodiment, the pH of the composition is from about 8.5 to about 10.5.

  The composition can be prepared by dispersing hexagonal boron nitride nanoparticles in a continuous phase (ie, water, alcohol, or a mixture of water and alcohol). The hexagonal boron nitride nanoparticles may be dispersed before or after the compound having formula (I) is added to the continuous phase. Any means known in the art can be used to disperse hexagonal boron nitride nanoparticles. In one embodiment, the nanoparticles are dispersed by sonication.

  Also disclosed herein is a method for exchanging heat utilizing the compositions disclosed herein as a heat transfer fluid. Methods for exchanging heat include flowing a stream through one side of the heat exchanger; flowing a composition disclosed herein to another side of the heat exchanger; Exchanging heat from the flow to the composition. In one embodiment, the method further includes generating heat in the self-propelled internal combustion engine. In another embodiment, the method further includes generating heat in the stationary internal combustion engine. In yet another embodiment, the method further includes generating heat in the electric motor or generator. In a further embodiment, the method further includes generating heat by condensation or chemical reaction, for example, in a smelter, a steam generation plant, or a fuel cell.

Preparation of Nanofluids Nanofluids containing dispersed hexagonal boron nitride nanoparticles were prepared in the Examples (Examples 5-8) and Comparative Examples (Examples 1-4 and 9-11). Micron-sized hexagonal boron nitride particles were added to isopropanol and sonicated for 1 hour. Thereafter, the hexagonal boron nitride particles were centrifuged at 2000 RPM for 10 minutes. Unstripped particles separated at the bottom. Exfoliated hexagonal boron nitride nanoparticles in isopropanol were filtered and dried. Hexagonal boron nitride nanoparticles, with or without re-sonication, and the following triblock copolymers

Redispersed in an ethylene glycol / water solution (50/50% by volume) with or without.

[Example 1]
Nanofluids were prepared with 0.1% by volume of hexagonal boron nitride nanoparticles in a solution of ethylene glycol / water (50/50% by volume).

[Example 2]
Nanofluids were prepared with 0.05% by volume of hexagonal boron nitride nanoparticles in an ethylene glycol / water solution (50/50% by volume).

[Example 3]
Nanofluids were prepared using 0.2% by volume hexagonal boron nitride nanoparticles in an ethylene glycol / water solution (50/50% by volume).

[Example 4]
Nanofluids were prepared with 0.5% by volume of hexagonal boron nitride nanoparticles in an ethylene glycol / water solution (50/50% by volume).

[Example 5]
Nanofluids were prepared with 0.1% by volume of hexagonal boron nitride nanoparticles and 0.1% by volume of triblock copolymer in an ethylene glycol / water solution (50/50% by volume).

[Example 6]
Nanofluids were prepared with 0.1 vol% hexagonal boron nitride nanoparticles and 0.2 vol% triblock copolymer in an ethylene glycol / water solution (50/50 vol%).

[Example 7]
Nanofluids are prepared by sonication using 0.05 vol% hexagonal boron nitride nanoparticles and 0.1 vol% triblock copolymer in ethylene glycol / water solution (50/50 vol%) did.

[Example 8]
Nanofluids are prepared by sonication using 0.2% by volume hexagonal boron nitride nanoparticles and 0.1% by volume triblock copolymer in an ethylene glycol / water solution (50/50% by volume) did.
[Example 9]

  Nanofluids were prepared by sonication using 0.1% by volume of hexagonal boron nitride nanoparticles in a solution of ethylene glycol / water (50/50% by volume).

[Example 10]
Nanofluids were prepared by sonication using 0.2% by volume hexagonal boron nitride nanoparticles in a solution of ethylene glycol / water (50/50% by volume).

[Example 11]
Nanofluids were prepared by sonication using 0.2% by volume of hexagonal boron nitride nanoparticles in a solution of Halvoline® XLC / water (50/50% by volume).

Stability Testing The nanofluids were stored at both room temperature and 85 ° C, and their stability was visually observed after 12 hours at both temperatures. The stability of the nanofluids is shown in the table below. The term "stable" means that no precipitation was observed. The term "unstable" means that precipitation was observed in the container containing the nanofluid.

  The results in the table show that the triblock copolymer stabilized the dispersion of hexagonal boron nitride nanoparticles in the nanofluids of Example Examples 5-7 both at room temperature and at elevated temperature of 85 ° C. 2 shows that the dispersion of hexagonal boron nitride nanoparticles in the nanofluid was stabilized at room temperature. In contrast, the nanofluids of Comparative Examples 1-4 and 9-11 without the triblock copolymer were not stable at both room temperature and 85 ° C.

Although the compositions and methods disclosed herein have been described with reference to specific embodiments, those skilled in the art will recognize that those skilled in the art may depart from the spirit and scope of the appended claims. It is intended to cover various changes and substitutions that can be made without.

Claims (20)

A continuous phase selected from the group consisting of water, alcohol, and a mixture of water and alcohol;
Hexagonal boron nitride nanoparticles dispersed in the continuous phase,
Formula (I)

Or a salt thereof, wherein n is an integer of 50 to 200, and y is an integer of 20 to 200.   2. The composition of claim 1, wherein n is an integer from 80 to 120 and y is an integer from 50 to 75.   The composition of claim 1, wherein n is 100 and y is 65. The hexagonal boron nitride nanoparticles, 5 nm or et 2 0 nm average sheet height, with an average sheet radius及beauty 5 0 nm or et 3 50 nm, the composition according to any one of claims 1 to 3. The hexagonal boron nitride nanoparticles, an average diameter of 5 0 nm or et 3 50 nm, with a及beauty 5 nm or et 2 average height of 0 nm, the composition according to any one of claims 1 to 4.   The composition according to any of the preceding claims, wherein the continuous phase is water or water and ethylene glycol.   7. The composition of claim 6, wherein the continuous phase is a 50/50% by volume water and ethylene glycol.   7. The composition of claim 6, wherein said continuous phase is water. Freezing point depressant, corrosion inhibitors, water stain preventing agent, a stabilizer, further comprising anti-oxidants, buffers, antifoaming agents, dyes or additives selected from the mixture or Ranaru group thereof, according to claim 9. The composition according to any one of 1 to 8.   The corrosion inhibitor is an aliphatic carboxylic acid or a salt thereof, an aromatic carboxylic acid or a salt thereof, triazole, thiazole, silicate, nitrate, nitrite, borate, phosphomolybdate, amine salt, and the like. 10. The composition according to claim 9, wherein the composition is selected from the group consisting of a mixture. The corrosion inhibitor may contain 0 . It is present in the composition at a concentration of 2 wt% to 1 0% by weight The composition of claim 10. Not precipitate for 12 hours at a temperature ranging from room temperature or al 8 5 ° C., composition according to any one of claims 1 to 11. The hexagonal boron nitride nanoparticles may contain 0 . 0001 vol% to 1 0 is present at a concentration in volume% in said composition A composition according to any one of claims 1 to 12. The hexagonal boron nitride nanoparticles may contain 0 . 005 volume% to 0. 14. The composition of claim 13, wherein the composition is present in the composition at a concentration of 5% by volume. The hexagonal boron nitride nanoparticles may contain 0 . 05 volume% to 0. 15. The composition of claim 14, wherein the composition is present in the composition at a concentration of 2% by volume. Compounds of formula (I) is 0. It is present in the composition at a concentration of 0001 vol% to 1 vol%, the composition according to any of claims 1 to 15. Compounds of formula (I) is 0. 2 vol% to 0. 17. The composition of claim 16, wherein the composition is present in the composition at a concentration of 7% by volume. Before or after the addition of adding the compound having formula (I) in the continuous phase, comprising dispersing a pre Symbol hexagonal boron nitride nanoparticles by the continuous phase, according to any one of the claims 1 to 17 A method for preparing the composition of a. Generating heat in the self-propelled internal combustion engine;
b. Flowing a stream to one side of the heat exchanger;
c. Flowing the composition to another side of the heat exchanger;
d. A method for exchanging heat comprising transferring heat from the stream to the composition in the heat exchanger,
The method, wherein the composition is according to any of the preceding claims.   Use of a composition according to any of the preceding claims as a heat transfer fluid.