ALCOHOL-BASED ORGANOGEL AS NANOFLUID MEDIUM

Abstract

An organogel including a base fluid, cetyl alcohol, and a gelling agent provided in an amount to cause the fluid to change from a liquid state to a gelled state at temperatures below at least 25° C. A nanofluid including an organogel and a nanoparticle component which permits the nanofluid to change from a liquid state to a gelled state at temperatures below at least 25° C., the gelled state helping to maintain the nanoparticle component suspended throughout the base fluid; and a method for preparing a gelled nanofluid.

Claims

1. An organogel comprising: a base fluid, cetyl alcohol, and a gelling agent provided in an amount to cause the fluid to change from a liquid state to a gelled state at temperatures below at least 25° C.

2. The organogel according to claim 1, wherein the base fluid is 2-hexyl-1-decanol or 2-n-octyl-1-dodecanol.

3. The organogel according to claim 1, wherein the concentration of cetyl alcohol is 1% to 15% by weight based on the total weight of the organogel.

4. The organogel according to claim 1, wherein the gelling agent is sodium oleate.

5. The organogel according to claim 1, wherein the concentration of the gelling agent is 0.1% to 2% by weight based on the total weight of the organogel.

6. The organogel according to claim 1, wherein a higher concentration of cetyl alcohol allows gelling at a higher temperature.

7. A nanofluid comprising: the organogel according to claim 1, and a nanoparticle component, wherein the nanofluid is configured to change from a liquid state to a gelled state at temperatures below at least 25° C., the gelled state helping to maintain the nanoparticle component suspended throughout the base fluid.

8. The nanofluid according to claim 7, wherein the base fluid for the organogel is 2-hexyl-1-decanol or 2-n-octyl-1-dodecanol.

9. The nanofluid according to claim 7, wherein the concentration of cetyl alcohol is 1% to 15% by weight based on the total weight of the organogel.

10. The nanofluid according to claim 7, wherein the gelling agent in the organogel is sodium oleate.

11. The nanofluid according to claim 7, wherein the concentration of the gelling agent is 0.1% to 2% by weight based on the total weight of the organogel.

12. The nanofluid according to claim 7, wherein the nanoparticle component is selected from the group consisting of molybdenum disulfide, nanodiamond, graphite, tungsten disulfide, hexagonal boron nitride, nanoparticles of materials with lamellar structure, and nanoparticles of soft metals, and combinations thereof.

13. The nanofluid according to claim 7, wherein the nanoparticle concentration is from 0-15% by weight based on the weight of the nanofluid.

14. A method of preparing a gelling nanofluid, the method comprising the steps of: preparing an organogel containing a base fluid, cetyl alcohol, and a gelling agent, combining the organogel with a nanoparticle component, to form a gelling nanofluid; and cooling the gelling nanofluid to a temperature of less than 25° C., which changes from a liquid state to a gelled state at temperatures below 25° C., the gelled state helping to maintain the nanoparticle component suspended throughout the base fluid.

15. The method according to claim 14, wherein the base fluid in the organogel is 2-hexyl-1-decanol or 2-n-octyl-1-dodecanol.

16. The method according to claim 14, wherein the concentration of cetyl alcohol in the organogel is 1% to 15% by weight based on the total weight of the organogel.

17. The method according to claim 14, wherein the gelling agent is sodium oleate.

18. The method according to claim 14, wherein the concentration of the gelling agent in the organogel is 0.1% to 2% by weight based on the total weight of the organogel.

19. The method according to claim 14, wherein the nanoparticle component is selected from the group consisting of molybdenum disulfide, nanodiamond, graphite, tungsten disulfide, hexagonal boron nitride, nanoparticles of materials with lamellar structure, and nanoparticles of soft metals, and combinations thereof.

20. The method according to claim 14, wherein the nanoparticle concentration is from 0-15% by weight based on the weight of the nanofluid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0023] FIG. 1A shows gelling of organogels containing 10% cetyl alcohol (CA) and 1% sodium oleate (SO) at 25° C. in time intervals. FIG. 1B shows gelling of organogels containing 10% cetyl alcohol (CA) and 1% sodium oleate (SO) at 10° C. in time intervals.

[0024] FIG. 2A shows gelling of organogels containing 5% CA and 1% SO at 25° C. in time intervals. FIG. 2B shows gelling of organogels containing 5% CA and 1% SO at 10° C. in time intervals.

[0025] FIG. 3A shows gelling of nanofluids containing 10% CA+1% SO and 4% MoS.sub.2 (molybdenum disulfide) nanoparticles at 25° C. in time intervals. FIG. 3B shows gelling of nanofluids containing 10% CA+1% SO and 4% MoS.sub.2 (molybdenum disulfide) nanoparticles at 10° C. in time intervals.

[0026] FIG. 4A shows gelling of nanofluids containing 5% CA+1% SO and 4% MoS.sub.2 nanoparticles at 25° C. in time intervals. FIG. 4B shows gelling of nanofluids containing 5% CA+1% SO and 4% MoS.sub.2 nanoparticles at 10° C. in time intervals.

[0027] FIG. 5 shows viscosity of organogels containing 10% CA with varied concentration of SO, i.e., 0.1%, 0.5%, and 1%, against temperature; the control solution without SO is also shown.

[0028] FIG. 6 shows elasticity of organogels containing 10% CA with varied concentration of SO, i.e., 0.1%, 0.5%, and 1%, against temperature; the control solution without SO is also shown.

[0029] FIG. 7 shows viscosity changes for organogels containing 5% CA with varied concentration of SO, i.e. 0.1%, 0.5% & 0.1% against temperature; the control solution without SO is also shown.

[0030] FIG. 8 shows modulus changes for organogels containing 5% CA with varied concentration of SO, i.e. 0.1%, 0.5% & 0.1% against temperature; the control solution without SO is also shown.

[0031] FIG. 9 shows the average scar diameter against the maximum Hertzian contact stress in extreme pressure (EP testing) for various solutions: the base fluid 2-hexyl-1-decanol (HD), the base fluid with 5% and 10% CA, the base fluid with 5% and 10% CA and 4% MoS.sub.2.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0032] The details of embodiments of the presently disclosed subject matter are set forth in the accompanying description below. Other features, objects, and advantages of the presently disclosed subject matter will be apparent from the specification, figures, and claims. All publications, patent applications, patents, and other references noted herein are incorporated by reference in their entirety.

[0033] The present disclosure relates to an alcohol-based organogel as a medium for temperatures-sensitive nanofluid gels. The alcohol-based organogel contains a base fluid, cetyl alcohol, and a gelling agent provided in an amount to cause the fluid to change from a liquid state to a gelled state at temperatures below at least 25° C.

[0034] The present disclosure also relates to a nanofluid containing the organogel and a nanoparticle component, which changes from a liquid state to a gelled state at temperatures below at least 25° C., the gelled state helping to maintain the nanoparticle component suspended throughout the base fluid.

[0035] Further, a method of preparing a gelling nanofluid is provided. The method includes the steps of: preparing an organogel by combining a base fluid, cetyl alcohol and a gelling agent, combining theorganogel with a nanoparticle component at temperatures up to 50° C., to prepare a nanofluid, and cooling the nanofluid to a temperature of less than 25° C. The nanofluid changes from a liquid state to a gelled state at temperatures below 25° C. The gelled state helps to maintain the nanoparticle component suspended throughout the base fluid.

[0036] The base fluid in the organogel may be 2-hexyl-1-decanol or 2-n-octyl-1-dodecanol, or similar alcohols. The gelling agent may be sodium oleate, alginic acid, sodium linoleate, or mixtures thereof.

[0037] For example, the alcohol-based organogel is formed from a solution of cetyl alcohol (CH.sub.3(CH.sub.2).sub.15OH) with a concentration range of 0-25% by weight in the solvent 2-hexyl-1-decanol (C.sub.16H.sub.34O) or 2-n-octyl-1-dodecanol at a temperature range of 30-50° C. The addition of sodium oleate (C.sub.18H.sub.33O.sub.2Na)(SO) with a weight concentration of 0.1-5% by weight and the cooling down in the temperature range of 5-25° C. produced the alcohol-based organogel.

[0038] Selected nanoparticles such as molybdenum disulfide (MoS.sub.2), nanodiamond, graphite, tungsten disulfide (WS.sub.2), hexagonal boron nitride (hBN), nanoparticles of materials with lamellar structure, and nanoparticles of soft metals such as silver, with a concentration of 0-15% by weight based on the weight of the organogel, are dispersed in the solution by sonication before gelling. When cooled at the desired temperature, the resultant is a gelled nanofluid that inhibits nanoparticle settlement often encountered in typical nanofluids.

[0039] By controlling the percentage of the cetyl alcohol in the organogel, the temperature at which the nanofluid is gelled can be controlled. A higher concentration of cetyl alcohol used in the method allows gelling at a higher temperature. For instance, with 1% concentration of sodium oleate, the solution containing 10% cetyl alcohol gelled at 25° C. while the solution containing 5% cetyl alcohol did not gel at 25° C., but it gelled at 10° C. Similarly, for a given concentration of the cetyl alcohol in the organogel, the gelling temperature can be controlled by varying the percentage of sodium oleate from 0.1 to 2%. Thus, the storage temperature requirement of the resultant nanofluid can be controlled. The present alcohol-based nanofluid has demonstrated a greater that 20% higher load capacity in extreme pressure testing compared with the organogel without nanoparticles and is suitable for lubrication and cooling applications such as cutting fluids.

Examples

[0040] The present invention is explained below in further detail with reference to Examples. However, the scope of the invention is not limited to these Examples. Unless otherwise specified all parts and percentages are by weight, and the reported measurements and other data were obtained under ambient conditions.

[0041] Gel Preparation

[0042] Solutions containing various percentages of cetyl alcohol (CA; purchased from Fisher Scientific) from 1% to 15% by weight in 2-hexyl-1-decanol (HD; purchased from Sigma Aldrich) were initially made. HD has a molecular formula of C.sub.16H.sub.34O and a molecular weight of 242.44 g/mol. CA has a molecular formula of CH.sub.3(CH.sub.2).sub.15OH and a molecular weight of 242.44 g/mol. To ensure that cetyl alcohol is completely dissolved in the solution, the mixture was warmed up to 50° C. while it was mechanically stirred. It was then sonicated by a sonicator probe for 5 to 10 minutes, Then, the solution was cooled down to room temperature. The solution remained transparent as long as the cetyl alcohol percentage did not exceed 15% by weight. For concentrations higher than 15% by weight of CA in HD, the solution started to become translucent. The solution gelled when sodium oleate (SO; purchased from Sigma Aldrich) is added in the concentration range of 0.1%4% to the solution. SO has a molecular formula of C.sub.18H.sub.33O.sub.2Na, and a molecular weight of 304.44 g/mol. SO forms bundles of cylindrical micelles which are made of SO fibers. The fibers dissolve and interact with CA molecules to form the gel. Cetyl alcohol has a longer chain than 2-hexa-1-decanol and therefore plays a critical role in gels formation because the solvophobic force of SO decreases with the increasing length of alcohol molecules. The gelator molecules (SO and CA molecules) interact with non-covalent interactions including hydrogen bonds, coordination bonds and van der Waals forces.

[0043] Rheology Measurements

[0044] A drop of the sample was placed on the Rheometer's controlled temperature plate, from 15 to 45° C. for 5 minutes. HR-3 Discovery Hybrid Rheometer was used to carry out the rheological measurements.

[0045] Extreme Pressure Test (EP)

[0046] In order to investigate the load-carrying properties of the alcohol-based organogel and the nanofluid in the liquid phase, extreme pressure testing (EP) according to ASTM D 2783-03 standard was carried out. Lubrication and Load-Carrying properties of organogel and nanofluids were carried out using Koehler TR-30H four-ball tester. In the test, a top ball was loaded on three lower balls and rotated against them under the applied load while the ball assembly was flooded with the organogel or nanofluid. A series of 10-second-duration tests were conducted at increasing loads until welding occurred. The rotating speed according to the EP test standard was 1760 rpm. It corresponds to 150 surface feet per minute (sfpm) sliding speed at the contact points.

[0047] Evaluation

[0048] The gel formation over time is shown for solutions containing 10% CA and 5% CA in FIGS. 1A-1B and 2A-2B, respectively. In both cases, the SO concentration was 1% by weight. As the temperature decreased from 25° C. (FIGS. 1A and 2A) to 10° C. (FIGS. 1B and 2B), the gelling time decreased. FIGS. 3A-3B and FIGS. 4A-4B show gel formation over time for nanofluids containing the organogel with addition of 4% by weight of molybdenum disulfide (MoS.sub.2) nanoparticles. The organogel contained either 10% CA or 5% CA and 1% SO by weight. As the temperature decreased the gelling time also decreased.

[0049] The viscosity of the alcohol-based organogels was studied using a rheometer. FIG. 5 and FIG. 6 shows the viscosity and the modulus for the organogels containing 10% CA and varied concentrations of SO, i.e. 1%, 0.5% and 0.1%. The viscosity of the solution without any SO was also determined as a control (FIG. 5). As the concentration of SO is increased, the viscosity dependence on temperate changes from being linear to bilinear, with a clear transition temperature below which the viscosity increases with a sharp slope. The transition temperature shifts to a higher value as the concentration of SO increases. The modulus also shows a similar transition, but not with sharp slope changes and magnitude increases as the viscosity (FIG. 6).

[0050] FIGS. 7 and 8 show the temperature-dependence of the viscosity and the modulus, respectively, for the organogel containing 5% CA with varied concentrations of SO, i.e. 1%, 0.5% and 0.1%. In FIG. 7 it was noted that for 5% CA, SO concentrations less than 1% do not produce gelation. Accordingly, the viscosity profile for these lower concentrations is similar to the control (no SO), but it has a similar bilinear slope at the 1% SO concentration. The viscosity without any SO was measured and shown in FIG. 7 as a control. The modulus data shown in FIG. 8 also shows an increase in modulus when the SO concentration was 1.0%.

[0051] Lubrication and Load-Carrying Properties of Organogel and Nanofluids

[0052] In order to investigate the load-carrying properties of the alcohol-based organogel and the nanofluid in the liquid phase, extreme pressure testing (EP) according to ASTM D 2783-03 standard was carried out. The results of the EP testing is presented in FIG. 9. The steel balls tested using as lubricant only the base fluid 2-hexyl-1-decanol (HD) and the base fluid 2-hexyl-1-decanol (HD) with 5% CA experienced rapid increase in the scar diameter at 4.7 GPa. This rapid increase is associated with the onset of welding and results in the stoppage of the testing. However, when HD solutions containing 5% CA is mixed with 4% MoS.sub.2 nanoparticles, welding in not experienced even when the contact stress is increased to values of 5.0, 5.5, and 5.7 GPa.

[0053] 2-Hexyl-1-decanol (HD) is used as a base fluid for the organogel in which various concentrations cetyl alcohol is dissolved. Then, by adding varied concentration of sodium oleate (SO), gelling of the solution is obtained. 2-Hexyl-1-decanol (HD) can be replaced by 2-n-octyl-1-dodecanol. The concentration of cetyl alcohol is 1% to 15% by weight. The concentration of the SO is 0.1% to 2%. The higher concentration of cetyl alcohol allows gelling at a higher temperature.

[0054] The alcohol-based organogels are used as medium for dispersion of nanoparticles such as MoS.sub.2 and hBN with known solid lubrication properties to develop gelled nanofluids. The temperature sensitive organogels inhibit the settlement of nanoparticles at the desired storage temperatures.

[0055] While the subject matter disclosed herein has been described in connection with what is presently considered to be practical example embodiments, it is to be understood that the present disclosure is not limited to the disclosed embodiments, and covers various modifications and equivalent arrangements included within the spirit and scope of the appended claims.