Nanocomposite material for energy storage devices

Abstract

A method for synthesizing a MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material includes adding distilled water and HNO.sub.3 to a mixture of (NH.sub.4).sub.2MoO.sub.4, Al(NO.sub.3).sub.3.Math.9H.sub.2O, Mg(Ac).sub.2.Math.4H.sub.2O, and sucrose to form a reaction mixture, heating the reaction mixture to a reaction temperature ranging from 150 C. to 220 C. until a carbonized product is formed, grinding of the carbonized product to form a ground carbonized product, and calcining the ground carbonized product at a temperature range from 700 C. to 800 C. for a period of 2 to 4 hours to form the MoO.sub.3@ Al.sub.2O.sub.3MgO nanocomposite material. The MoO.sub.3 content of the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material is in a range from 1 wt. % to 20 wt. %. The MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has an AC conductivity greater than or equal to 110.sup.6 S/m when measured at 6 megahertz.

Claims

1. A method for synthesizing a MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material, comprising: adding distilled water and HNO.sub.3 to a mixture of (NH.sub.4).sub.2MoO.sub.4, Al(NO.sub.3).sub.3.Math.9H.sub.2O, Mg(Ac).sub.2.Math.4H.sub.2O, and sucrose to form a reaction mixture; heating the reaction mixture to a reaction temperature in a range of 150 C. to 220 C. until a carbonized product is formed; grinding the carbonized product to form a ground carbonized product; and calcining the ground carbonized product at a temperature in a range from 700 C. to 800 C. for a period of 2 to 4 hours to form the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material, grinding the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material to form a nanocomposite powder, pressing the nanocomposite powder under a pressure of from 110.sup.3 to 110.sup.2 kg/cm.sup.2 to form a nanocomposite tablet having a diameter of about 10 mm and a thickness of about 1 mm, and spreading a silver paste on both sides of the tablet; wherein the MoO.sub.3 content of the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material is in a range from 9 wt. % to 11 wt. % based on the total weight of the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material, and wherein the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has an AC conductivity greater than or equal to 110.sup.6 S/m when measured at 6 MHz.

2. The method of claim 1, wherein the (NH.sub.4).sub.2MoO.sub.4 is present in the reaction mixture in a range from 0.1 M to 1.0 M.

3. The method of claim 2, wherein the (NH.sub.4).sub.2MoO.sub.4 is present in the reaction mixture in a range from 0.2 M to 0.5 M.

4. The method of claim 1, wherein the sucrose is present in the reaction mixture in a range from 0.1 M to 1 M.

5. The method of claim 4, wherein the sucrose is present in the reaction mixture in a range from 0.45 M to 0.65 M.

6. The method of claim 1, wherein the Al Al(NO.sub.3).sub.3.Math.9H.sub.2O is present in the reaction mixture in a range from 0.5 M to 1.5 M.

7. The method of claim 6, wherein the AI Al(NO.sub.3).sub.3.Math.9H.sub.2O is present in the reaction mixture in a range from 0.9 M to 0.95 M.

8. The method of claim 1, wherein the Mg(Ac).sub.2.Math.4H.sub.2O is present in the reaction mixture in a range from 2.0 M to 2.7 M.

9. The method of claim 8, wherein the Mg(Ac).sub.2: 4H.sub.2O is present in the reaction mixture in a range from 2.2 M to 2.5 M.

10. The method of claim 1, wherein the HNO.sub.3 is present in the reaction mixture in a range from 1.8 M to 3.0 M.

11. The method of claim 1, wherein the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has an AC conductivity greater than or equal to 210.sup.6 S/m when measured at 6 MHz.

12. The method of claim 11, wherein the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has an AC conductivity greater than or equal to 410.sup.6 S/m when measured at 6 MHz.

13. The method of claim 1, wherein the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has a dielectric constant in a range of 7 to 11 when measured at 6 MHz.

14. The method of claim 13, wherein the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has a dielectric constant in a range of 8 to 10 when measured at 6 MHz.

15. The method of claim 14, wherein the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has a dielectric constant in a range of 8.5 to 9.5 when measured at 6 MHz.

16. The method of claim 1, wherein the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has a dielectric loss factor of less than or equal to 1.5 when measured at 6 MHz.

17. The method of claim 16, wherein the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has a dielectric loss factor of less than or equal to 1.0 when measured at 6 MHz.

18. The method of claim 17, wherein the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has a dielectric loss factor of less than or equal to 0.5 when measured at 6 MHz.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A more complete appreciation of this disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

(2) FIG. 1 is a schematic flow chart depicting a method of synthesizing a MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material, according to certain embodiments.

(3) FIG. 2 is a graph depicting the frequency influences on the alternating current (AC) conductivity of MoO.sub.3/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(4) FIG. 3 is a graph depicting dependency of MoO.sub.3/MgAl.sub.2O.sub.4 nanocomposite on AC conductivity frequency, according to certain embodiments.

(5) FIG. 4 is a graph depicting frequency dependence of dielectric constant of MoO.sub.3/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(6) FIG. 5 is a graph depicting frequency-dielectric loss () correlation for MoO.sub.3/MgAl.sub.2O.sub.4 nanocomposite, according to certain embodiments.

(7) FIG. 6 is a graph depicting Nyquist (Z-Z) plots for MoO.sub.3/MgAl.sub.2O.sub.4 nanocomposite at room temperature, according to certain embodiments.

DETAILED DESCRIPTION

(8) In the drawings, like reference numerals designate identical or corresponding parts throughout the several views. Further, as used herein, the words a, an and the like generally carry a meaning of one or more, unless stated otherwise.

(9) Furthermore, the terms approximately, approximate, about and similar terms generally refer to ranges that include the identified value within a margin of 20%, 10%, or preferably 5%, and any values therebetween.

(10) As used herein, the term dielectric loss factor refers to the energy dissipation per cycle in the material. Specifically, it quantifies the ratio of the energy lost as heat to the energy stored in the dielectric material during one cycle of the applied electric field. Higher tan indicates higher energy loss and lower efficiency in storing electrical energy.

(11) As used herein, the term dielectric constant refers to the measure of how much a material can store electrical energy in an electric field, relative to the amount of energy stored in a vacuum. It is a dimensionless quantity that indicates how easily a material can be polarized by an applied electric field.

(12) Aspects of the present disclosure are directed to a method of fabricating a MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material designed to improve the performance of semiconductor devices. The material is based on a unique composite structure, incorporates a combination of metal oxides and alumina, offering enhanced electrical conductivity and better frequency-dependent behavior. The composition and fabrication methods simplify the synthesis process while also leading to high efficiency and stability. The nanomaterial demonstrates improvements in electrical properties, such as an increase in AC conductivity and a more stable dielectric response over a range of frequencies. The present disclosure provides a solution for applications requiring high-frequency performance and greater material stability. In contrast to prior art, which often relies on complex synthesis routes and results in materials with lower conductivity at higher frequencies, the disclosed material circumvents these drawbacks by providing enhanced electrical performance, particularly in terms of frequency response and material stability, making it an ideal candidate for next-generation semiconductor technologies.

(13) FIG. 1 illustrates a flow chart of a method 50 for synthesizing a MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material. The order in which the method 50 is described is not intended to be construed as a limitation, and any number of the described method steps can be combined in any order to implement the method 50. Additionally, individual steps may be removed or skipped from the method 50 without departing from the spirit and scope of the present disclosure.

(14) At step 52, the method 50 includes adding distilled water and HNO.sub.3 to a mixture of (NH.sub.4).sub.2MoO.sub.4, Al Al(NO.sub.3).sub.3.Math.9H.sub.2O, Mg(Ac).sub.2: 4H.sub.2O, and sucrose to form a reaction mixture. The Al Al(NO.sub.3).sub.3.Math.9H.sub.2O provides the Al.sup.3+ ions needed to form Al.sub.2O.sub.3; the Mg(Ac).sub.2.Math.4H.sub.2O supplies the Mg.sup.2+ ions, (NH.sub.4).sub.2MoO.sub.4 provides the molybdenum oxide precursorThe sucrose acts as a carbon source to potentially aid in creating a porous structure. In some embodiments, glucose, citric acid, glycerol, tannic acid, polyvinyl alcohol (PVA), humic acid may also be used in place of sucrose to serve as the carbon source.

(15) Nitric acid is generally used to facilitate the dissolution of the mixture in water and helps in forming the reaction mixture; although other acids like hydrochloric acid (HCl), sulfuric acid (H.sub.2SO.sub.4), perchloric acid (HClO.sub.4), boric acid (H.sub.3BO.sub.3), phosphoric acid, hydrofluoric acid, hydrobromic acid, hydroiodic acid, perchloric acid, chloric acid, bromic acid, iodic acid, selenic acid, telluric acid, carbonic acid, silicic acid, boric acid, chromic acid, manganic acid, periodic acid, arsenic acid, antimonic acid, stannic acid, phosphorous acid, hypophosphorous acid, hypochlorous acid, chlorous acid, hypobromous acid, bromous acid, hypoiodous acid, iodous acid, perbromic acid, periodic acid, carbonic acid can be used as well.

(16) In some embodiments, the sucrose is present in the reaction mixture in a range from 0.1 to 1 M, more preferably 0.45 to 0.65 M, and yet more preferably about 0.584 M. In some embodiments, the concentration of (NH.sub.4).sub.2MoO.sub.4 in the reaction mixture in a range from 0.1 to 1.0 M, preferably about 0.2 to 0.5 M. In some embodiments, the concentration of Al(NO.sub.3).sub.3.Math.9H.sub.2O present in the reaction mixture is in a range from 0.5 to 1.5 M, more preferably 0.9 to 0.95 M, and yet more preferably 0.930 M. In some embodiments, the concentration of Mg(Ac).sub.2: 4H.sub.2O in the reaction mixture is in the range from 2.0 to 2.7 M, more preferably 2.2 to 2.5 M, and yet more preferably 2.36 M. The HNO.sub.3 is present in the reaction mixture in a range from 1.8 to 3.0 M.

(17) At step 54, the method 50 includes heating the reaction mixture to a reaction temperature in a range of 150 to 220 C. until a carbonized product is formed. In some embodiments, heating of the reaction mixture can be performed by using heating appliances such as ovens, microwaves, autoclaves, hot plates, heating mantles and tapes, oil baths, salt baths, sand baths, air baths, hot-tube furnaces, and hot-air guns. The heating is carried out until all the water is evaporated and the carbon source has degraded.

(18) At step 56, the method 50 includes grinding the carbonized product to form a ground carbonized product. The grinding may be carried out using any suitable means, for example, ball milling, blending, etc., using manual method (e.g., mortar) or machine-assisted methods such as using a mechanical blender, or any other apparatus known to those of ordinary skill in the art. In a preferred embodiment, the carbonized product is ground in a mortar to obtain the ground carbonized product.

(19) At step 58, the method 50 includes calcining the ground carbonized product at a temperature in a range from 700 to 800 C., more preferably 720 to 820 C., and yet more preferably 750 C. for a period of 2 to 4 hours, 2.5 to 3.5 hours, and yet more preferably 3 hours to form the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material. The calcination is carried out by heating it to a high temperature under a restricted supply of ambient oxygen. This is performed to remove impurities or volatile substances and to incur thermal decomposition. Typically, the calcination is carried out in a furnace, preferably equipped with a temperature control system, which may provide a heating rate of up to 50 C./min, preferably up to 40 C./min, preferably up to 30 C./min, preferably up to 20 C./min, preferably up to 10 C./min, preferably up to 5 C./min. During calcination, any carbon source material left further decomposes, leaving behind a porous structure, and the metal salts convert to oxides, forming the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material. The properties of the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material produced are the same as those described above. The product of calcination may retain a carbonaceous residue obtained from the carbonization of the sucrose and the subsequent calcination of the carbonized product. As the calcination of the present disclosure will conventionally occur in the absence of activators or templating agents for the carbonized product, it is considered that the retained carbonaceous residue will comprise amorphous carbon. In certain embodiments, the nanocomposite may comprise amorphous carbon in an amount up to about 2 wt. %, based on the weight of the nanocomposite. For example, the nanocomposite may comprise amorphous carbon in an amount up to about 1 wt. % or up to about 0.5 wt. %, based on the weight of the nanocomposite.

(20) The MoO.sub.3 content of the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material is in a range from 1 to 20 wt. %, preferably in a range from 5 to 15 wt. %, preferably in a range from 9 to 11 wt. %, more preferably 10 wt. % of the total weight of the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material.

(21) In some embodiments, the MoO.sub.3@ Al.sub.2O.sub.3MgO nanocomposite material has an AC conductivity greater than or equal to 110.sup.6 S/m, preferably greater than or equal to 210.sup.6 S/m, preferably greater than or equal to 310.sup.6 S/m, preferably greater than or equal to 410.sup.6 S/m, when measured at 6 MHz. In some embodiments, the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has a dielectric constant in a range of 7 to 11, preferably 8 to 10, preferably 8.5 to 9.5, preferably around 9 when measured at 6 MHz. In some embodiments, the MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material has a dielectric loss factor of less than or equal to 1.5, preferably less than or equal to 1.0, preferably less than or equal to 0.5 when measured at 6 MHz.

EXAMPLES

(22) The following examples demonstrate a method for synthesizing a MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material. The examples are provided solely for illustration and are not to be construed as limitations of the present disclosure, as many variations thereof are possible without departing from the spirit and scope of the present disclosure.

Example 1: Preparation of 10% MoO.SUB.3.@ Al.SUB.2.O.SUB.3.MgO Nanohybrids

(23) According to the present disclosure, about 10.0 grams (g) of sucrose, 17.46 g of Al Al(NO.sub.3).sub.3.Math.9H.sub.2O, 25.41 g of Mg(Ac).sub.2.Math.4H.sub.2O and the appropriate amount of ammonium molybdate were transferred to a beaker of 500 milliliters (mL). In the powder mixture, 50 mL of distilled water (DW) and 5 mL of nitric acid (HNO.sub.3) were added and heated to a temperature of 100 C. until the mixture turned into a clear solution. Further, the temperature was raised to about 150 C. to 200 C. and heated until the sucrose was carbonized. The resulting black product was ground in a mortar, calcined at 700 C. for 3.0 hours, and the 10% MoO.sub.3@Al.sub.2O.sub.3MgO triple nanocomposite was then collected.

Example 2: Electrical Measurements

(24) A two-probe method was used to measure the electrical conductivity (EC) of tablets that are 10 millimeters (mm) in diameter and about 1 mm in thickness. The tablets were made by pressing powder under a pressure of 210.sup.3 kg/cm.sup.2. Further, silver paste was spread on both surfaces of the tablet, and the tablets were placed in an oven to remove any moisture. Under room temperature conditions, the electrical conductivity, dielectric constant, dielectric loss, and impedance were measured by a programmable automatic LCR bridge (model HIOKI IM 3536) at a fixed voltage of 1.0 volt (V) and frequencies between 1000 hertz (Hz) and 2 megahertz (MHz). The frequency-dependent complex dielectric function may be expressed by equation (1):
**()=()j()(1)
with j=1, the imaginary part of the permittivity was represented by , while the real part was represented by . Equation (2) and equation (3) were used to approximate the values for and :
=Cd/As(2)
()=() tan (3)
where, (=8.8610.sup.12 F/m) represents the free space permittivity, d represents thickness, As represents cross-section area, tan represents dissipative factor and (2f) represents electric field frequency.

(25) The AC method distinguishes between a plurality of mechanisms, such as electrode response, grain boundary conduction, and grain conduction. In addition, grain conduction contributes to the overall conductivity of a material. The frequency dependence of AC conductivity for the MoO.sub.3/MgAl.sub.2O.sub.4 nanocomposite was analyzed at room temperature, as shown in FIG. 2. Equation (4) was utilized to determine the AC conductivity of each sample:
.sub.AC=.sup.0 tan (4)
where .sup.0 represents vacuum permittivity, represents the dielectric constant, and tan represents the loss tangent.

(26) FIG. 2 illustrates that AC conductivity increases with frequency, particularly at higher frequencies, due to the greater pumping power delivered to charge carriers by the high frequency. Hence, AC conductivity is highest at higher frequencies [See: Su, F., et al., mpg-C(3)N(4)-Catalyzed selective oxidation of alcohols using O(2) and visible light, J. Am. Chem. Soc., 2010 Nov. 24; 132 (46): 16299-301]. An increase in the hopping rate of charge between the charge carriers was sufficient to enhance conductivity without increasing the number of charge carriers.

(27) The Koops model predicts the behavior of the nanocomposite as a multilayer capacitor of grains and grain boundaries [See: Yan, S. et al., Photodegradation Performance of g-C3N4 Fabricated by Directly Heating Melamine, Langmuir, 2009, 25, 17, 10397-10401]. The Koops model may explain the increase in AC conductivity with temperature and frequency. A practically continuous plateau region was observed at lower frequencies, attributed to the resistive grain boundaries, which hindered the hopping of electronic charge carriers between boundaries. However, the conductive grains were more active at higher frequencies, allowing charge carriers to hop between neighboring ions.

(28) The release of trapped charge carriers from localized regions resulted in increased high-frequency conductivity, a stronger applied field, and higher migration and movement of the released charge carriers in multiple directions. The conduction behavior of material was influenced by liberated charge carriers and electron mobility among many metal ions [See: Maheshwaran, G. et al., Fabrication of self charging supercapacitor based on two dimensional bismuthene-graphitic carbon nitride nanocomposite powered by dye sensitized solar cells, Journal of Energy Storage, Volume 56, Part A, 2022, 105900].

(29) Materials used in semiconductors have the following frequency-dependent relationship, as depicted by equation (5):
.sub.AC()=A.sup.s(5)
where A and s are constants.

(30) A sudden hopping of the charge carriers results in translational motion if s<1, while a localized hopping of the species was indicated by s>1 [See: Rao, B. et al., Effect of sintering conditions on resistivity and dielectric properties of NiZn ferrites, Journal of Materials Science, 1997, 32, 6049-6054]. The effect was caused by the relaxation resulting from the movement of electrons or atoms by tunneling or hopping between equilibrium locations. The exponent s was determined by graphing the natural logarithm of .sub.AC () against the natural logarithm of (), as shown in FIG. 3.

(31) The value of s was 0.6081, which indicated that correlated barrier hopping (CBH) was the most likely mechanism in the MoO.sub.3/MgAl.sub.2O.sub.4 nanocomposite. In general, the relation between the conduction mechanism and s(f) behavior may suggest a suitable model for the conduction mechanism.

(32) The frequency dependence of the for the MoO.sub.3/MgAl.sub.2O.sub.4 nanocomposite at room temperature is illustrated in FIG. 4, which shows a dispersion in values as the frequency increased. At lower frequencies, the decline in values occurs very quickly, whereas at higher frequencies, approaching a constant value takes a longer time.

(33) Further, charge polarization may generally be referred to as the storage of some energy in a substance when exposed to an external electric field. The stored energy was represented by the real component of the dielectric constant. To evaluate the behavior of microstructural entities such as grains and grain borders, it was vital to examine the dielectric constant. Hence, FIG. 4 illustrates the effect of frequency on the of the examined materials at specific temperatures. The graph indicated that for the nanocomposite, decreased with an increase in frequency. The decline in was rapid at lower frequencies but more gradual at higher frequencies. The observed dielectric behavior may be explained by the hopping process and the idea of polarization [See: Sivakumar, D. et al., Structural Characterization and Dielectric Studies of Superparamagnetic Iron Oxide Nanoparticles, Journal of the Korean Ceramic Society, 55, 3]. The composite was presumed to include distinct regions (grains and grain boundaries), with the conductivity of the grains being higher than that of the grain boundaries. As a result, higher values were linked to charge accumulation at the grain boundaries. According to Koops' theory, the interfacial polarization of the Maxwell-Wagner type was used to interpret the dielectric dispersion curves. These models suggested that the composite was made up of conductor-rich grains separated by conductor-poor grain boundaries, with the grain boundaries being more effective at low frequencies and the grains becoming more effective at higher frequencies.

(34) In general, dielectric loss specifies the amount of energy dissipated due to the movement of charge carriers. FIG. 5 shows the variation of with frequency for the MoO.sub.3/MgAl.sub.2O.sub.4 nanocomposite at room temperature. The behavior obtained is comparable to that of the real part of the dielectric constant, which decreases as frequency increases. In the low-frequency range, the value dropped sharply, while it remained low in the high-frequency range. The aforementioned trend may be explained by the fact that the samples exhibited higher resistivity at low frequencies due to the grain boundaries, requiring more energy for charge hopping between cations, which resulted in higher losses. At higher frequencies, where the samples exhibited lower resistivity due to the grains, less energy was required for charge hopping between cations at the octahedral sites. The polarization of space charges may have contributed to the reduction in dielectric loss as frequency increased.

(35) Further, impedance spectroscopy may be an efficient technique for correlating the electrical properties with the microstructure of substrates. In general, electrochemical impedance spectroscopy (EIS) spectra depicts distinct semicircles in the complex impedance plane, reflecting different relaxation times. The impedance responses from the grain boundaries and the grains may overlap if the variation in time constants among the processes is less than 100. FIG. 6 shows the complex impedance spectra for the MoO.sub.3/MgAl.sub.2O.sub.4 nanocomposite, depicting a single depressed semicircle in the complex impedance plots at 303 K [See: Ahmed, M. et al., Rare earth doping effect on the structural and electrical properties of MgTi ferrite, Materials Letters, Volume 57, Issues 26-27, 2003].

(36) The aspects of the present disclosure provide the method for synthesizing a MoO.sub.3@Al.sub.2O.sub.3MgO nanocomposite material. In particular, 10 wt. % M003@MgAl.sub.2O.sub.4 nanomaterials were synthesized using the method described herein. The electrical conductivity values for the nanomaterials increased with increasing frequency, indicating their semiconducting behavior. The variation of dielectric constant (), dielectric loss (), and AC conductivity for the examined nanomaterials at different frequencies was evaluated. Both dielectric constant () and dielectric loss () were decreased with the increase of frequency, while the AC conductivity increased. The hopping of electrons and holes is suggested to be the electrical conduction mechanism. Hence, the 10 wt. % MoO.sub.3/MgAl.sub.2O.sub.4 nanomaterials developed in accordance with the present disclosure, depicted desirable characteristics, rendering them fit for use in supercapacitors, energy storage applications, and electrical applications.

(37) Numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.