Systems, articles, and methods related to hydrophobic aerogels

Abstract

Articles, systems, and methods related to hydrophobic aerogels are generally described. Aerogels, including monolithic aerogels, may be exposed to hydrophobization agents such that the resulting article has advantageous hydrophobicity for window applications. Such articles may exhibit relatively high contact angles and / or relatively low water uptake in any of a variety of environments, including environments having relatively high humidities. In some embodiments, exposing the aerogel to hydrophobization agents do not substantially alter the optical properties of the aerogel.

Description

[0001] SYSTEMS, ARTICLES, AND METHODS RELATED TO HYDROPHOBIC AEROGELS RELATED APPLICATIONS

[0002] This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 63 / 761,341, filed February 21, 2025, and entitled “Systems, Articles, and Methods Related to Hydrophobic Aerogels,” which is incorporated herein by reference in its entirety for all purposes.

[0003] GOVERNMENT SPONSORSHIP

[0004] This invention was made with Government support under Contract No. 2037715 awarded by the National Science Foundation. The Government has certain rights in the invention.

[0005] TECHNICAL FIELD

[0006] Hydrophobic aerogels are generally described.

[0007] BACKGROUND

[0008] Poorly insulated windows and other desirably-transparent articles may exacerbate undesirable heat transfer between external environments and the interior of the structures, such as commercial and residential buildings, which they separate. Such heat transfer may result in increased energy expenditure as climate control systems may need to operate for longer durations of time. Conventional thermal insulation materials are generally not well suited for window applications as they do not have sufficient transparency. Accordingly, improved transparent insulation materials are needed.

[0009] SUMMARY

[0010] Hydrophobic aerogels are generally described. The subject matter of the present disclosure involves, in some cases, interrelated products, alternative solutions to a particular problem, and / or a plurality of different uses of one or more systems and / or articles.

[0011] One aspect of the present disclosure describes articles. In some embodiments, the article comprises: an aerogel comprising silica, wherein haze through at least a portion of the aerogel is less than or equal to 15%, and the aerogel has a water contact angle greater than or equal to 90 degrees.In some embodiments, the article comprises an aerogel comprising silica, wherein haze through at least a portion of the aerogel is less than or equal to 15%, and when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40 % for a duration of 1 hour, the aerogel is configured to uptake an amount of moisture that is less than or equal to 10% of the total mass of the aerogel prior to exposure to the environment.

[0012] In some embodiments, the article comprises: an aerogel comprising silica, wherein the aerogel, when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40 % for 1 hour, has a haze of less than or equal to 15 %.

[0013] In some embodiments, the article comprises: an aerogel comprising silica, wherein the aerogel has a volume greater than or equal to 800 cm3and a contact angle between the aerogel and a water droplet adjacent to the aerogel is greater than or equal to 90 degrees.

[0014] In some embodiments, the article comprises: an aerogel having a water contact angle greater than or equal to 90 degrees, and wherein haze through at least a portion of the aerogel is less than or equal to 15%.

[0015] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments of the disclosure when considered in conjunction with the accompanying figures. In cases where the present specification and a document incorporated by reference include conflicting and / or inconsistent disclosure, the present specification shall control.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying figures, which are schematic and are not intended to be drawn to scale unless otherwise indicated. In the figures, each identical or nearly identical component illustrated is typically represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of each embodiment of the disclosure shown where illustration is not necessary to allow those of ordinary skill in the art to understand the disclosure. In the figures:

[0018] FIG. 1A is a schematic diagram of a monolithic aerogel, according to some

[0019] embodiments.FIG. IB is a schematic diagram of a monolithic aerogel and an electromagnetic radiation pathway extending therethrough, according to some embodiments.

[0020] FIG. 1C is a schematic diagram of an aerogel and a water droplet adjacent thereto that generally describes the water contact angle of the aerogel, according to some embodiments.

[0021] FIG. 2A is a plot describing haze through aerogels having undergone hydrophobization, according to some embodiments.

[0022] FIGS. 2B-2C are images depicting water contact angle of a hydrophobic aerogel, according to some embodiments, and damage induced by water on a hydrophilic aerogel.

[0023] FIGS. 3A-3B are plots depicting haze and water contact angle of hydrophobic aerogels, according to some embodiments.

[0024] DETAILED DESCRIPTION

[0025] The present disclosure relates generally to improved aerogels and / or improved articles incorporating aerogels, for a variety of uses including but not limited to articles, systems, and / or methods for passing electromagnetic radiation (including visible light) while providing a degree of thermal insulation. Some aerogels disclosed herein have hydrophobic properties Aerogels are a class of materials that are generally known for their relatively high porosity, low thermal conductivity, and in some cases, relatively high transparency. Yet many prior aerogels exhibit compromised properties, and / or are difficult to make and / or use effectively. This disclosure describes significant advances in aerogels and related articles and uses.

[0026] In some embodiments, aerogels of this disclosure comprise a porous network including a framework material defining a plurality of pores (e.g., voids). The pores are generally of a material different from the framework. For example, within the pores of the porous network can be contained a solid, liquid, or a gas generally different in whole or in part from the framework that defines the pores (present surrounding the pores). In many instances, a gas is contained within the pores (e.g., air, an inert gas, or another gas or mixture of gases). In one set of common embodiments, the pores contain air.

[0027] Characteristics of an aerogel, such as the ratio of overall volume consumed by the pores relative to the volume of the framework (i.e., the porosity of the aerogel), and content of the pores, may limit thermal conduction through articles that include the aerogels allowing the aerogel and / or article to have a relatively low overall thermal conductivity, i.e., a high insulative quality. Accordingly, aerogels may be a promising material for any of a variety of insulation applications (e.g., thermal insulation and / or acoustic insulation).In certain instances, it is desirable that aerogels, or at least portions of aerogels, are at least partially transmissive of electromagnetic radiation at specific wavelengths, and / or within wavelength ranges (e.g., transparent to visible light having wavelengths greater than or equal to 360 nm and less than or equal to 780 nm). In some cases, it may be desirable that aerogels, or at least portions of aerogels, have relatively low haze so that light transmitted along an electromagnetic energy pathway through the aerogel is not excessively diffused. Aerogels having relatively low thermal conductivity and high transparency may be suitable to serve as a window or window component, a component of a solar thermal receiver, etc., e.g., an insulation layer for window applications (e.g., windows on commercial / residential buildings and / or vehicles).

[0028] Typically, aerogels are relatively hygroscopic and uptake water (e.g., moisture) when exposed to ambient environments, even those having relatively low humidities. After exposure to such environments, the aerogel may appear to have increased haze due to the presence of water and / or moisture within the porous structure of the aerogel. Moreover, transmittance through the aerogel may also be reduced after exposure to such environments. While aerogels are a promising transparent insulator for window applications, the hygroscopic properties are undesirable in window applications (e.g., residential and / or commercial windows), where the aerogel may be exposed to environments having a wide range of humidities. Over time, hygroscopic aerogels incorporated into window applications may exhibit increased haze and / or decreased transmittance as the aerogel uptakes water. In some cases, water uptake may affect properties including, but not limited to, mechanical properties and / or optical properties of the aerogel. For instance, a hygroscopic aerogel that is a transparent monolithic material may form a white (e.g., hazy), crumbly material when exposed to liquid water. Exposure to water vapor may lead to surface cracking and general deterioration of the aerogel. Moreover, since aerogels in window applications may be exposed to other harsh conditions (e.g., extreme temperatures, humidities, UV exposure) which may exacerbate degradation of the aerogel’s optical properties, it may be desirable to produce aerogels that can maintain their optical properties throughout a wide range of conditions.

[0029] As described in the present disclosure, the hygroscopic properties of the aerogel may be mitigated by subjecting the aerogel (e.g., the aerogel itself, the precursor mixture, and / or the gel from which the aerogel is derived) to any of a variety of suitable hydrophobization agents. By exposing aerogels, such as monolithic aerogels, to hydrophobization agents, it is possible to render the aerogel hydrophobic, thereby mitigating some of the aerogel’s hygroscopic properties. The resulting hydrophobic aerogel has desirable optical properties including but not limited torelatively high transmittance and relatively haze through the aerogel. Moreover, after the aerogel undergoes the hydrophobization treatment described herein, the optical properties of the aerogel surprisingly may not be significantly altered compared to the optical properties of an otherwise essentially identical aerogel not having undergone the hydrophobization treatment. Accordingly, such aerogels may be particularly advantageous in window applications, as the aerogels may be able to withstand environments of varying humidity without exhibiting substantial changes and / or degradation of the optical properties therethrough.

[0030] Thus, this disclosure generally describes aerogels having hydrophobic properties and related articles, including articles that are generally more insulative than otherwise comparative articles. Moreover, this disclosure provides improved processes for hydrophobizing aerogels (e.g., aerogels comprising silica).

[0031] In some embodiments, the aerogel is exposed to a hydrophobization agent. As used herein, “hydrophobization agent” may generally refer to any compound that increases the hydrophobicity of an aerogel, or at least a portion thereof, after exposure of the aerogel, a gel from which the aerogel is derived, or a precursor mixture from which the aerogel is derived, to the hydrophobization agent. In some embodiments, the hydrophobization agent comprises organosilicon compound. In some embodiments, the hydrophobization agent comprises a silane group, a siloxane group, and / or a silazane group. In some embodiments, the hydrophobization agent comprises hexamethyldisilazane (HMDZ), hexamethyldisiloxane (HMDSO), and / or methyltrimethoxysilane (MTMS). Other hydrophobization agents may also be used. Without wishing to be bound by any particular theory, the hydrophobization agent may react with residual hydroxyl groups present in the aerogel or on a surface thereof to form a region of nonpolar, organic groups (e.g., alkyl groups) thereby increasing the local hydrophobicity in that region. In some embodiments, when aerogels or surfaces thereof are exposed to the hydrophobization agent, the aerogel and / or surface of the aerogel may exhibit increased hydrophobicity. Advantageously, using the methods described in the present disclosure, the optical properties of the aerogel may be at least maintained after treating the aerogel with the hydrophobization agent.

[0032] In embodiments where the aerogel was exposed to the hydrophobization agent, the hydrophobization agent may be involved at any point during the fabrication of the aerogel in a manner that renders at least a portion of the aerogel hydrophobic. While the present disclosure generally describes exposure of aerogels to hydrophobization agents, it should be understood that in many embodiments, a porous network that has undergone gelation (e.g., a gel having liquid in its pores) may be instead exposed to the hydrophobization agent. In some cases, the gel,and / or the aerogel derived from the gel, may be formed from a mixture comprising the hydrophobization agent. In any case, the systems, articles, and processes described herein may produce aerogels having advantageous hydrophobicity and optical properties for window applications. Any description related to the exposure of the aerogel to the hydrophobization agent indicates that the aerogel itself, the precursor mixture from which the aerogel was derived, and / or the gel from which the aerogel was derived, was exposed to hydrophobization agent. For example, an aerogel that has been exposed to the hydrophobization agent may have undergone such exposure at the precursor stage (e.g., the precursor mixture comprises the hydrophobization agent), at the gelation stage (e.g., when the gel having liquid in at least some of its pores is exposed to the hydrophobization agent), and / or after the formation of the aerogel (e.g., when the porous network having predominantly gas in its pores is exposed to the hydrophobization agent).

[0033] In some embodiments, the aerogel is exposed to a mixture comprising the hydrophobization agent. By exposing the aerogel to the mixture, the aerogel may then be exposed to the hydrophobization agent. In some embodiments, the mixture comprises the hydrophobization agent and a solvent. In some embodiments, the solvent comprises methanol, ethanol, and / or isopropyl alcohol. Other solvents may be used. It should be appreciated that the aerogel may be exposed to the hydrophobization agent prior to critical point drying of the aerogel, at which point the porous network is effectively a gel rather than an aerogel, due to the presence of liquid in the porous network.

[0034] In some embodiments, the solvent may dilute the hydrophobization agent so that, after exposing the aerogel to the hydrophobization agent, the aerogel, or a portion thereof, exhibits increased hydrophobicity. In some cases, it may be advantageous to set the concentration of the hydrophobization agent, e.g., dilute it, so that, after the hydrophobization is exposed to the aerogel, the aerogel does not exhibit a substantial increase in haze. For example, after exposure to the hydrophobization agent (or a diluted mixture comprising the hydrophobization agent), the aerogel may exhibit haze that is no more than 5% (e.g., no more than 4%, no more than 3%, no more than 2%, no more than 1%, no more than 0.5%, no more than 0.5%) greater than the haze exhibited by the aerogel prior to the exposure to the hydrophobization agent. In some embodiments, the mixture comprises the hydrophobization agent at a concentration of greater than or equal to 0.1 wt%, greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 3 wt%, greater than or equal to 4 wt%, greater than or equal to 5 wt%, greater than or equal to 7.5 wt%, greater than or equal to 10 wt%, greater than or equal to 15 wt%, and / or greater than or equal to 20 wt%. In some embodiments, the mixture comprises the hydrophobization agent at a concentration of less than or equal to 20 wt%, less than or equal to-1- 15 wt%, less than or equal to 10 wt%, less than or equal to 7.5 wt%, less than or equal to 5 wt%, less than or equal to 4 wt%, less than or equal to 3 wt%, less than or equal to 2 wt%, less than or equal to 1 wt%, less than or equal to 0.1 wt%. Combinations of these ranges are possible (e.g., greater than or equal to 0.1 wt% and less than or equal to 20 wt%). Other ranges are also possible.

[0035] In some embodiments, the aerogel is exposed to the hydrophobization agent such that at least a portion of the aerogel is hydrophobic (e.g., exhibits hydrophobicity). In some embodiments, exposing the aerogel involves partially or entirely submerging the aerogel in the mixture. For example, a gel from which an aerogel may be derived can be submerged in a mixture comprising the hydrophobization agent, such that, after a drying process, the resulting aerogel may exhibit hydrophobicity. In some embodiments, the aerogel is submerged in a bath comprising the mixture for a duration of time and / or at a temperature greater than the ambient environment. For window applications, it may be advantageous for the entirety of aerogel, as opposed to only exterior surfaces of the aerogel, to have relatively high hydrophobicity.

[0036] Accordingly, by submerging the aerogel in the bath, the hydrophobization agent may be transported throughout the pores within the bulk of the aerogel rendering both exterior surfaces of the aerogel and the interior surfaces of the aerogel relatively hydrophobic. For example, as shown in FIG. 1A, article 100 comprises aerogel 102 having surface 103, thickness Tl, length LI, and width Wl. The volume of aerogel 102 is defined by thickness Tl, length LI, and width Wl. In some embodiments, the hydrophobicity of the aerogel may be essentially even throughout the aerogel. In other embodiments, the hydrophobicity may be uneven throughout the aerogel. For example, by exposing the entire volume of aerogel 102 to the hydrophobization agent, the bulk of aerogel 102 may exhibit hydrophobic properties. However, if only surface 103 of aerogel 102 is exposed to the hydrophobization agent, surface 103 will exhibit hydrophobic properties while other portions of the aerogel may be relatively hydrophilic. For window applications, it may be advantageous to therefore submerge the entire volume of the aerogel in the mixture comprising the hydrophobization agent so that the bulk of the aerogel exhibits hydrophobicity.

[0037] In some embodiments, the aerogel is exposed to the hydrophobization agent at any of a variety of durations. In some embodiments, the aerogel is exposed to the hydrophobization agent for advantageously short durations which increases the throughput of fabrication processes for hydrophobic aerogels. In such embodiments, the hydrophobization process may be compatible with processes used to manufacture aerogel at commercial sizes and / or scales. In some embodiments, the aerogel is exposed to the hydrophobization agent for less than or equal to 24hours, less than or equal to 16 hours, less than or equal to 10 hours, less than or equal to 8 hours, less than or equal to 6 hours, less than or equal to 4 hours, less than or equal to 2 hours, less than or equal to 1 hours, and / or less than or equal to 30 minutes. In some embodiments, the aerogel is exposed to the hydrophobization agent for greater than or equal to 30 minutes, greater than or equal to 1 hour, greater than or equal to 2 hour, greater than or equal to 4 hour, greater than or equal to 6 hour, greater than or equal to 8 hour, greater than or equal to 10 hour, greater than or equal to 16 hours, and / or 24 hours. Combinations of these ranges are possible (e.g., less than or equal to 24 hours and greater than or equal to 30 minutes). Other ranges are possible.

[0038] In some embodiments, exposing the aerogel to the hydrophobization agent and / or the mixture comprising the hydrophobization agent may occur at an elevated temperature. For instance, the hydrophobization agent and / or the mixture may be heated such that when the aerogel is submersed in the hydrophobization agent and / or the mixture, the aerogel is exposed to it at an elevated temperature. In some embodiments, a bath comprising the hydrophobization agent may be heated. In some embodiments, the aerogel may be exposed to the hydrophobization agent and / or a mixture comprising the hydrophobization agent at a temperature of greater than or equal to 25 degrees Celsius, greater than or equal to 30 degrees Celsius, greater than or equal to 35 degrees Celsius, greater than or equal to 40 degrees Celsius, greater than or equal to 45 degrees Celsius, greater than or equal to 50 degrees Celsius, greater than or equal to 55 degrees Celsius, greater than or equal to 60 degrees Celsius, greater than or equal to 65 degrees Celsius, and / or greater than or equal to 70 degrees Celsius. In some embodiments, the aerogel may be exposed to the hydrophobization agent and / or a mixture comprising the hydrophobization agent at a temperature of less than or equal to 70 degrees Celsius, less than or equal to 65 degrees Celsius, less than or equal to 60 degrees Celsius, less than or equal to 55 degrees Celsius, less than or equal to 50 degrees Celsius, less than or equal to 45 degrees Celsius, less than or equal to 40 degrees Celsius, less than or equal to 35 degrees Celsius, less than or equal to 30 degrees Celsius, and / or less than or equal to 25 degrees Celsius. Combinations of these ranges are possible (e.g., greater than or equal to 25 degrees Celsius and less than or equal to 65 degrees Celsius). Other ranges are possible.

[0039] In some embodiments, the hydrophobization agent may be included in a silica precursor mixture (e.g., a solution) used to form the aerogel. In such embodiments, the hydrophobization agent may be added to the mixture comprising the silica precursor and solvent, which may then be used to prepare aerogels using the methods described herein or others. For example, MTMS may be added into the precursor mixture, along with a silica precursor (e.g., TMOS) or in lieu of the silica precursor. For instance, the precursor mixture may have a MTMS to TMOS weightratio of at least 5:95, at least 10:90, at least 15:85, at least 20:80 or more. In some embodiments, the hydrophobization agent is the precursor which forms the aerogel and / or the backbone thereof. While aerogels produced with a precursor solution comprising the hydrophobization agent may produce aerogels having relatively low haze, not all embodiments described herein are fabricated using such solutions. Rather, in some embodiments, as described elsewhere in the present disclosure, aerogels may be submerged in a mixture (e.g., a solution) comprising the hydrophobization agent.

[0040] In some embodiments, after exposing the aerogel to the hydrophobization agent, the optical properties of the aerogel may not be substantially altered. That is, the aerogel, prior to exposure to the hydrophobization agent, may have optical properties that are considered advantageous in window applications (e.g., relatively high transmittance and / or relatively low haze), and after exposure to the hydrophobization, the aerogel may continue to exhibit such properties. While some changes to the optical properties of the aerogel may be measurable after exposure to the hydrophobization agent, such changes may not render the aerogel unsuitable and / or undesirable for window applications. It should be appreciated that the methods described herein may render any of a variety of aerogels hydrophobic. In some cases, the aerogel comprises silica. In certain embodiments, the aerogel comprises cellulose.

[0041] In some embodiments, the haze along an electromagnetic radiation pathway traversing at least a portion of the aerogel is relatively low after exposure to the hydrophobization agent. In some embodiments, the electromagnetic radiation pathway may be a path for the transmission of electromagnetic radiation through at least a portion of the aerogel. In some embodiments, the electromagnetic radiation pathway is orthogonal to one or more surfaces of the aerogel and / or the substrate. For example, as shown in FIG. IB, electromagnetic radiation pathway 104 traverses a portion of aerogel 102. Accordingly, the haze of article 100 along electromagnetic radiation pathway 104 may be relatively low. In some embodiments, the electromagnetic radiation pathway is parallel to the thickness direction of the aerogel. For example, as shown in FIGS. 1A-1B, electromagnetic radiation pathway 104 is parallel to thickness T1 of aerogel 102. In a similar manner, transmittance through the aerogel and / or a portion thereof at at least one wavelength greater than or equal to 360 nm and less than or equal to 780 nm along the electromagnetic radiation pathway may be relatively high before and after the hydrophobization treatment.

[0042] In some embodiments, after exposure to the hydrophobization agent, the aerogel has a relatively low haze. In some embodiments, haze through at least a portion of the aerogel is less than or equal to 15%, less than or equal to 12.5%, less than or equal to 10%, less than or equal to7.5%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, and / or less than or equal to 2%. In some embodiments, haze through at least a portion of the aerogel is greater than or equal to 2%, greater than or equal to 3%, greater than or equal to 4%, greater than or equal to 5%, greater than or equal to 7.5%, greater than or equal to 10%, greater than or equal to 12.5%, and / or greater than or equal to 15%. Combinations of these ranges are possible (e.g., less than or equal to 15% and greater than or equal to 2%). Other ranges are also possible. In some embodiments, the haze of the aerogel can be measured as calculated in accordance with ASTM standard DI 003- 13 which is incorporated herein by reference in its entirety for all purposes. In some embodiments, the haze of the aerogel is measured through the shortest pathway through the aerogel. In some embodiments, the haze of the aerogel may be determined by measuring the haze, in accordance with ASTM standard D1003-13, through the thickness direction of the aerogel wherein the thickness direction of the aerogel is the shortest pathway through the aerogel. In some embodiments, the haze of the aerogel may be determined by measuring haze, in accordance with ASTM standard D1003-13, through an electromagnetic radiation pathway through the aerogel. When measuring haze of the aerogel in accordance with ASTM D1003-13, a hazemeter or a spectrophotometer may be used.

[0043] In some embodiments, the aerogel, after exposure to the hydrophobization agent, has a relatively high transmittance. In some embodiments, the article has a transmittance greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, and / or greater than or equal to 95% at at least one wavelength greater than or equal to 360 nm and less than or equal to 780 nm. In some embodiments, the article has a transmittance less than or equal to 95%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 75%, less than or equal to 70%, less than or equal to 65%, less than or equal to 60%, less than or equal to 55%, and / or less than or equal to 50% at at least one wavelength greater than or equal to 360 nm and less than or equal to 780 nm. Combinations of these ranges are possible (e.g., greater than or equal to 50% and less than or equal to 95%). Other ranges are also possible. In some embodiments, the transmittance of the aerogel is measured along the electromagnetic radiation pathway.

[0044] In some embodiments, the hydrophobicity of the aerogel may be determined by measuring the contact angle of the aerogel. In some embodiments, the contact angle of the aerogel is the angle between a water droplet placed on the surface of the aerogel and the surface itself. When a water droplet is placed on a surface (e.g., a surface on an aerogel), a solid-gasinterface (ysg), a solid-liquid interface (ysi), and a liquid-solid interface (yis) exists. The contact angle is the angle between the liquid-gas and solid-liquid interfaces. This is shown in FIG. 1C, where water droplet 106 is disposed on surface 103 of aerogel 102. Solid-gas interface ysg, a solid-liquid interface ysi, and liquid-gas interface yigforms between water droplet 106 and surface 103 of aerogel 102. Contact angle Al is the angle between liquid-gas interface yigand solid-liquid interface ysi. It is generally known that contact angles greater than or equal to 90 degrees indicate that the surface on which the droplet is disposed is relatively hydrophobic. Conversely, it is also generally known that contact angles less than or equal to 90 degrees indicate that the surface on which the droplet is disposed is relatively hydrophilic. It should be noted that the contact angle can be determined under static conditions (described above) but also under dynamic conditions (e.g., as the droplet wets the surface). In some embodiments, the contact angle is an advancing contact angle. That is, the contact angle is a measure of the angle between the liquid-gas interface and the solid-liquid interface as the droplet wets the surface of the aerogel. In some embodiments, the droplet (e.g., an aqueous droplet such as a water droplet) is adjacent to the surface of the aerogel.

[0045] The aerogels described in the present disclosure have undergone a hydrophobization process that renders the aerogel relatively hydrophobic. Accordingly, in view of at least the above, such aerogels may exhibit water contact angles greater than or equal to 90 degrees and may be referred to as hydrophobic aerogels. Hydrophobicity of the aerogels may substantially prevent and / or mitigate water uptake when exposed to moisture under any of a variety of conditions, as described herein. Moreover, the optical properties of the aerogel are not substantially altered after the hydrophobization process. Surprisingly, the optical properties of the resulting hydrophobic aerogels are not substantially altered after subsequent exposure to environments having high relative humidities.

[0046] In some embodiments, the aerogel, after exposure to the hydrophobization agent, exhibits any of a variety of suitable contact angles. In some embodiments, the aerogel has a contact angle greater than or equal to 90 degrees, greater than or equal to 95 degrees, greater than or equal to 100 degrees, greater than or equal to 105 degrees, greater than or equal to 110 degrees, greater than or equal to 115 degrees, greater than or equal to 120 degrees, greater than or equal to 130 degrees, greater than or equal to 140 degrees, greater than or equal to 150 degrees greater than or equal to 160 degrees greater than or equal to 170 degrees and / or greater than or equal to 180 degrees. In some embodiments, the aerogel has a contact angle less than or equal to 180 degrees, less than or equal to 170 degrees, less than or equal to 160 degrees, less than or equal to 150 degrees, less than or equal to 140 degrees, less than or equal to 130 degrees, less than or equal to120 degrees, less than or equal to 115 degrees, less than or equal to 110 degrees, less than or equal to 105 degrees, less than or equal to 100 degrees, less than or equal to 95 degrees, and / or less than or equal to 90 degrees. Combinations of these ranges are possible (e.g., greater than or equal to 90 degrees and less than or equal to 140 degrees). Other ranges are also possible. In some embodiments, the contact angle between a water droplet and the aerogel can be measured using a camera and / or an optical microscope configured to monitor the angle between the liquidgas and solid-liquid interfaces. In some embodiments, a contact angle goniometer may be used to measure the contact angle of a droplet on an aerogel.

[0047] In some embodiments, the aerogel may exhibit relatively high contact angles after exposure to elevated temperatures. In some embodiments, the aerogel, when used in window applications as a transparent insulation material, may be exposed to sunlight (e.g., direct or indirect sunlight) and / or elevated temperatures. In some embodiments, the aerogel may advantageously remain hydrophobic (e.g., exhibit a relatively high contact angle) despite exposure to such conditions. Moreover, during fabrication of aerogels, annealing processes may be used. Such annealing process may involve exposing the aerogels to relatively high temperatures (e.g., 190 degrees Celsius) for extended durations of time (e.g., 24 hours). Since such annealing processes may take place after hydrophobization of the aerogel, it is desirable for the hydrophobicity of the aerogel to withstand such temperatures. In some embodiments, the water contact angle of the aerogel is greater than or equal to 90 degrees, greater than or equal to 95 degrees, greater than or equal to 100 degrees, greater than or equal to 105 degrees, greater than or equal to 110 degrees, greater than or equal to 115 degrees, greater than or equal to 120 degrees, greater than or equal to 130 degrees, greater than or equal to 140 degrees, greater than or equal to 150 degrees, greater than or equal to 160 degrees, greater than or equal to 170 degrees, and / or greater than or equal to 180 degrees, after the aerogel is exposed to a temperature of greater than or equal to 190 degrees Celsius for at least 22 hours. In some embodiments, the water contact angle of the aerogel is less than or equal to 180 degrees, less than or equal to 170 degrees, less than or equal to 160 degrees, less than or equal to 150 degrees, less than or equal to 140 degrees, less than or equal to 130 degrees, less than or equal to 120 degrees, less than or equal to 115 degrees, less than or equal to 110 degrees, less than or equal to 105 degrees, less than or equal to 100 degrees, less than or equal to 95 degrees, and / or less than or equal to 90 degrees, after the aerogel is exposed to a temperature of greater than or equal to 190 degrees Celsius for at least 22 hours. Combinations of these ranges are possible. Other ranges are also possible.In some embodiments, the aerogel may exhibit relatively high contact angles after exposure to ultraviolet light (e.g., electromagnetic radiation having wavelengths between 100 nm and 400 nm). In some embodiments, the aerogel, when used in window applications, may be exposed to ultraviolet light through direct and / or indirect exposure to sunlight. Such exposure may degrade and / or deteriorate the hydrophobicity of conventional materials, but surprisingly, the aerogel described in the present disclosure may exhibit hydrophobicity despite such exposure. In some embodiments, the water contact angle of the aerogel is greater than or equal to 90 degrees, greater than or equal to 95 degrees, greater than or equal to 100 degrees, greater than or equal to 105 degrees, greater than or equal to 110 degrees, greater than or equal to 115 degrees, greater than or equal to 120 degrees, greater than or equal to 130 degrees, greater than or equal to 140 degrees, greater than or equal to 150 degrees greater than or equal to 160 degrees greater than or equal to 170 degrees and / or greater than or equal to 180 degrees. Combinations of these ranges are possible (e.g., greater than or equal to 90 degrees and less than or equal to 180 degrees). Other ranges are also possible.

[0048] In some embodiments, the aerogel, when exposed to an environment under any of a variety of conditions, may uptake a relatively low amount of water. As previously mentioned, aerogels are known to be hygroscopic, and accordingly, in the presence of moisture, typical aerogels may uptake moisture, thereby increasing the overall mass of the aerogel. In some embodiments, a comparison between the initial mass of the aerogel and the final mass of the aerogel after exposure to moisture may indicate the extent of which the aerogel absorbed such moisture. Hydrophobic aerogels may not uptake a substantial amount of moisture, and accordingly, the mass of a relatively hydrophobic aerogel after exposure to a relatively humid environment may not be substantially higher than the initial mass thereof. In some embodiments, the aerogel, when exposed to an environment having a temperature of 25 degrees Celsius (or at least 25 degrees Celsius, at least 30 degrees Celsius, at least 35 degrees Celsius, at least 40 degrees Celsius, or at least 45 degrees Celsius, and / or up to 50 degrees Celsius, up to 55 degrees Celsius, or up to 60 degrees Celsius), a pressure of 1 atm, and a relative humidity of 40% (or at least 40%, at least 45%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, and / or up to 95%, up to 97%, or up to 99.9%) for a duration of 1 hour (or at least 1 hour, at least 2 hours, at least 5 hours, at least 10 hours, at least 15 hours, at least 20 hours, at least 24 hours, or up to 2 days, up to 3 days, or up to 7 days), the aerogel is configured to uptake an amount of moisture (e.g., water) that is less than or equal to 10% (or less than or equal to 7.5%, less than or equal to 5%, less than or equal to 4.5%, less than or equal to 4%, less than or equal to 3.5%, less than or equal to 3%, less than or equal to 2.5%, less than or equal to 2%, less than or equal to1.5%, or less than or equal to 1%, and / or greater than or equal to 0.1%, greater than or equal to 0.2%, or greater than or equal to 0.5%) of the total mass of the aerogel prior to exposure to the environment. Combinations of these ranges are possible (e.g., less than or equal to 10% and greater than or equal to 0.1%). Other ranges are also possible. In some embodiments, the amount of moisture may be determined by evaluating the mass of water in the aerogel after exposure to the environment, as described elsewhere in the disclosure.

[0049] Water uptake by the aerogel may be determined by measuring a final mass of an aerogel after exposure to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for a duration of 1 hour. The difference between the final mass of the aerogel and the initial mass of the aerogel prior to the exposure of the aerogel to the environment may then be divided by the initial mass of the aerogel, and the resulting quotient is multiplied by 100 to obtain the percentage of moisture the aerogel uptakes. In some embodiments, when an aerogel uptakes water, the water may be absorbed, adsorbed, and / or otherwise transported into the porous network of the aerogel.

[0050] In some embodiments, the aerogel, when exposed to an environment under any of a variety of conditions, may exhibit relatively low haze through at least a portion of the aerogel. As described elsewhere in the present disclosure, the optical properties of typical aerogels may degrade when exposed to relatively humid environments. Surprisingly, the optical properties of the aerogels described herein, having undergone hydrophobization, may not degrade and / or deteriorate when exposed to relatively humid environments. For example, when a hydrophobic aerogel having a relatively low haze (e.g., a haze of 15% or less) is exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for 1 hour, the aerogel may continue to exhibit a relatively low haze (e.g., a haze of 15% or less) after the 1 hour has ended. In some embodiments, when exposed to an environment having a temperature of 25 degrees Celsius (or at least 25 degrees Celsius, at least 30 degrees Celsius, at least 35 degrees Celsius, at least 40 degrees Celsius, or at least 45 degrees Celsius, and / or up to 50 degrees Celsius, up to 55 degrees Celsius, or up to 60 degrees Celsius), a pressure of 1 atm, and a relative humidity of 40% (or at least 40%, at least 45%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, and / or up to 95%, up to 97%, or up to 99.9%) for 1 hour (or at least 1 hour, at least 2 hours, at least 5 hours, at least 10 hours, at least 15 hours, at least 20 hours, at least 24 hours, or up to 2 days, up to 3 days, or up to 7 days), the aerogel has a haze less than or equal to 15% (or less than or equal to 12.5%, less than or equal to 10%, less than or equal to 7.5%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, or less than or equal to 2%, and / or greater than or equal to 0.01%, greater than or equal to 0.05%, orgreater than 1%). Combinations of these ranges are possible (e.g., less than or equal to 15% and greater than or equal to 1%). Other ranges are also possible. Haze through the aerogel and / or through a portion thereof may be measured as described elsewhere in the present disclosure.

[0051] In some embodiments, when the aerogel is exposed to humid environments, the aerogel does not exhibit a significant increase in haze. For example, when a hydrophobic aerogel having a relatively low haze (e.g., 5% haze) is exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for 1 hour, the aerogel may exhibit only a relatively small increase in haze (e.g., from 5% haze to less than 15% haze), if any at all, after the 1 hour has ended. In some embodiments, the aerogel, when exposed to an environment having a temperature of 25 degrees Celsius (or at least 25 degrees Celsius, at least 30 degrees Celsius, at least 35 degrees Celsius, at least 40 degrees Celsius, or at least 45 degrees Celsius, and / or up to 50 degrees Celsius, up to 55 degrees Celsius, or up to 60 degrees Celsius), a pressure of 1 atm, and a relative humidity of 40% (or at least 40%, at least 45%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, and / or up to 95%, up to 97%, or up to 99.9%) for 1 hour (or at least 1 hour, at least 2 hours, at least 5 hours, at least 10 hours, at least 15 hours, at least 20 hours, at least 24 hours, or up to 2 days, up to 3 days, or up to 7 days), the aerogel exhibits no more than a 15% (or no more than 12.5%, no more than 10%, no more than 7.5%, no more than 5%, no more than 2%, or less) increase in haze.

[0052] In some embodiments, the aerogel, when exposed to an environment having a temperature of 25 degrees Celsius (or at least 25 degrees Celsius, at least 30 degrees Celsius, at least 35 degrees Celsius, at least 40 degrees Celsius, or at least 45 degrees Celsius, and / or up to 50 degrees Celsius, up to 55 degrees Celsius, or up to 60 degrees Celsius), a pressure of 1 atm, and a relative humidity of 40% (or at least 40%, at least 45%, at least 50%, at least 60%, at least 70%, at least 80%, at least 90%, and / or up to 95%, up to 97%, or up to 99.9%) for 1 hour (or at least 1 hour, at least 2 hours, at least 5 hours, at least 10 hours, at least 15 hours, at least 20 hours, at least 24 hours, or up to 2 days, up to 3 days, or up to 7 days), the aerogel exhibits an increase in haze by no more than a 15 percentage points (or no more than 12.5 percentage points, no more than 10 percentage points, no more than 7.5 percentage points, no more than 5 percentage points, no more than 2 percentage points, or less). For example, when an aerogel exhibiting 2% haze is exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for 1 hour, the aerogel may exhibit a haze of 17% (e.g., an increase of 15 percentage points), after the 1 hour has ended.

[0053] In some embodiments, the aerogel has a relatively large volume and / or a surface having a relatively large area calculated by a length, a width, and / or a thickness of the aerogel. Forexample, as shown in FIG. 1A, aerogel 102 has length LI, width Wl, and thickness Tl. Aerogel 102 has a relatively large volume equivalent to the product of the multiplication of width Wl, length LI, and thickness TL Aerogel 102 also has surface 103 having a relatively large area equivalent to the production of the multiplication of width Wl and length LI. In some embodiments, the length and / or the width of the aerogel is greater than or equal to 12 in, greater than or equal to 18 in, greater than or equal to 24 in, greater than or equal to 36 in, greater than or equal to 48 in, greater than or equal to 60 in, greater than or equal to 72 in, or greater than or equal to 100 in. In some embodiments, the length and / or the width of the aerogel is less than or equal to 1000 in, less than or equal to 500 in, less than or equal to 250 in, less than or equal to 100 in, less than or equal to 72 in, less than or equal to 60 in, or less than or equal to 48 in. Combinations of these ranges are possible (e.g., greater than or equal to 12 in and less than or equal to 1000 in). Other ranges are possible. It should be understood that the dimensions described above generally refer to dimensions of a monolithic portion of the aerogel rather than the sum of dimensions of two or more portions of aerogel (e.g., aerogel particles). For example, turning once again to FIG. 1A, aerogel 102, being monolithic, has length LI, width Wl, and thickness TL

[0054] In some embodiments, the aerogel has a volume greater than or equal to 400 cm3, greater than or equal to 800 cm3, greater than or equal to 1000 cm3, greater than or equal to 1200 cm3, greater than or equal to 1500 cm3, greater than or equal to 2000 cm3, greater than or equal to 2500 cm3, greater than or equal to 3000 cm3, greater than or equal to 4000 cm3, greater than or equal to 5000 cm3, greater than or equal to 7500 cm3, and / or greater than or equal to 10000 cm3. In some embodiments, the aerogel has a volume less than or equal to 100000 cm3, less than or equal to 50000 cm3, less than or equal to 10000 cm3, less than or equal to 7500 cm3, less than or equal to 5000 cm3, less than or equal to 4000 cm3, less than or equal to 3000 cm3, less than or equal to 2500 cm3, less than or equal to 2000 cm3, less than or equal to 1500 cm3, less than or equal to 1200 cm3, less than or equal to 1000 cm3, less than or equal to 800 cm3, and / or less than or equal to 400 cm3. Combinations of these ranges are also possible (e.g., greater than or equal to 400 cm3and less than or equal to 100000 cm3). Other ranges are also possible.

[0055] In some embodiments, the aerogel described herein may have any of a variety of suitable densities. In some embodiments, the aerogel has a density of less than or equal to 350 kg / m3, less than or equal to 300 kg / m3, less than or equal to 250 kg / m3, less than or equal to 200 kg / m3, less than or equal to 150 kg / m3, less than or equal to 100 kg / m3, or less than or equal to 50 kg / m3. In some embodiments, the aerogel has a density of greater than or equal to 50 kg / m3, greater than or equal to 100 kg / m3, greater than or equal to 150 kg / m3, greater than or equal to200 kg / m3, greater than or equal to 250 kg / m3, greater than or equal to 300 kg / m3, or greater than or equal to 350 kg / m3. Combinations of these ranges are possible (e.g., less than or equal to 350 kg / m3and greater than or equal to 50 kg / m3). Other ranges are also possible.

[0056] In some embodiments, the aerogel has a relatively low thermal conductivity. In some embodiments, the aerogel has a thermal conductivity that is sufficiently low such that the aerogel may serve as a transparent insulation material. In some embodiments, the thermal conductivity of the aerogel is less than or equal to 25 mW / mK, less than or equal to 22.5 mW / mK, less than or equal to 20 mW / mK, less than or equal to 17.5 mW / mK, less than or equal to 16 mW / mK, less than or equal to 15 mW / mK, less than or equal to 10 mW / mK, or less than or equal to 5 mW / mK. In some embodiments, the thermal conductivity of the aerogel is greater than or equal to 0.1 mW / mK, greater than or equal to 1 mW / mK, greater than or equal to 5 mW / mK, greater than or equal to 10 mW / mK, greater than or equal to 15 mW / mK, less than or equal to 16 mW / mK, greater than or equal to 17.5 mW / mK, greater than or equal to 20 mW / mK, greater than or equal to 22.5 mW / mK, or greater than or equal to 25 mW / mK. Combinations of these ranges are possible (e.g., less than or equal to 25 mW / mK and greater than or equal to 0.1 mW / mK). Other ranges are possible.

[0057] In some embodiments, the thermal conductivity of an aerogel (e.g., a monolithic aerogel) may be determined using a calibrated hot plate method. For example, a 4 inch by 4 inch region of the aerogel, having a known thickness, may be placed on a hot plate with a reference material, having a known thermal conductivity and disposed on top of the aerogel sample. The hot plate may then be turned on to a setpoint of 40 degrees Celsius, and a container of ice may be placed on the reference material. Thermocouples may be used to monitor the temperature of the container of ice, the reference material, the aerogel, and the hotplate. The thermal conductivity of the sample may then be calculated using Equation 1 shown below, where Ti is the temperature at the interface of the hotplate and the aerogel sample, T2 is the temperature at the interface between the aerogel and the reference material, T3 is the temperature at the interface of the reference material and the container of ice, T4 is the temperature of the container of ice, ki is the thermal conductivity of the aerogel sample, k2 is the thermal conductivity of the reference material, ti is the thickness of the aerogel sample, and t2 is the thickness of the reference material.

[0058]

[0059] In some embodiments, the aerogel has a relatively small mean pore radius. Without wishing to be bound by any particular theory, aerogels having a relatively small mean pore radius may be advantageously transparent to light and / or have a surprisingly low thermalconductivity. In some embodiments, the aerogel has a mean pore radius of less than or equal to 10 nm, less than or equal to 8 nm, less than or equal to 6 nm, less than or equal to 5 nm, or less than or equal to 4 nm. In some embodiments, the aerogel has a mean pore radius of greater than or equal to 1 nm, greater than or equal to 2 nm, greater than or equal to 3 nm, greater than or equal to 4 nm, greater than or equal to 5 nm, greater than or equal to 6 nm, greater than or equal to 8 nm, or greater than or equal to 10 nm. Combinations of these ranges are possible (e.g., less than or equal to 10 nm and / or greater than or equal to 1 nm). Other ranges are possible.

[0060] In some embodiments, the aerogel has a relatively small mean scattering radius. In some embodiments, the aerogel has a mean scattering radius of less than or equal to 5 nm, less than or equal to 4 nm, less than or equal to 3 nm, less than or equal to 2 nm, or less than or equal to 1 nm. In some embodiments, the aerogel has a mean scattering radius of greater than or equal to 0.1 nm, greater than or equal to 1 nm, greater than or equal to 2 nm, greater than or equal to 3 nm, greater than or equal to 4 nm, or greater than or equal to 5 nm. Combinations of these ranges are possible (e.g., less than or equal to 5 nm and greater than or equal to 0.1 nm). Other ranges are also possible.

[0061] In some embodiments, the mean scattering radius and / or the pore size of the aerogel may be measured by using small angle x-ray scattering (SAXS) and / or by Brunauer-Emmett-Teller analysis (BET).

[0062] In some embodiments, the aerogel has a relatively low mean particle radius. In some embodiments, the aerogel has a mean particle radius of less than or equal to 2 nm, less than or equal to 1.75 nm, less than or equal to 1.5 nm, less than or equal to 1.25 nm, less than or equal to 1 nm, less than or equal to 0.75 nm, or less than or equal to 0.5 nm. In some embodiments, the aerogel has a mean particle radius of greater than or equal to 0.1 nm, greater than or equal to 0.5 nm, greater than or equal to 0.75 nm, greater than or equal to 1 nm, greater than or equal to 1.25 nm, greater than or equal to 1.5 nm, greater than or equal to 1.75 nm, or greater than or equal to 2 nm. Combinations of these ranges are possible (e.g., less than or equal to 2 nm and greater than or equal to 0.1 nm). Other ranges are also possible.

[0063] In some embodiments, the aerogel has a relatively high porosity. The relatively high porosity of the aerogel, in some embodiments, may allow the aerogel to have an advantageously low thermal conductivity such that it may serve as a thermal and / or acoustic insulator. In some embodiments, the aerogel has a porosity greater than or equal to 90%, greater than or equal to 92%, greater than or equal to 94%, greater than or equal to 96%, greater than or equal to 98%, or greater than or equal to 99%. In some embodiments, the aerogel has a porosity less than or equal to 99%, less than or equal to 98%, less than or equal to 96%, less than or equal to 94%, less thanor equal to 92%, or less than or equal to 90%. Combinations of these ranges are possible (e.g., greater than or equal to 90% and less than or equal to 99%). Other ranges are possible.

[0064] In some embodiments, the aerogel comprises silica. In some embodiments, the aerogel comprises at least 10 wt% (e.g., at least 20 wt%, at least 30 wt%, at least 40 wt%, at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt%) silica. Silica, in some embodiments, comprises silicon dioxide (SiCh). Aerogels comprising silica may have relatively high transparency, in some cases, making them desirable for use as a transparent insulator in windows. In some embodiments, the aerogel is a silica aerogel.

[0065] In some embodiments, the aerogel comprises one or more additives that may improve one or more properties (e.g., haze, transparency, mechanical properties such as rupture strength, etc.). In some embodiments, the one or more additives comprises particles (e.g., fiber, macroscale particles, microparticles, nanoparticles, etc.) capable of altering one or more properties of the aerogel.

[0066] Any of a variety of suitable substrate may be used to form the article described herein. In some embodiments, the substrate is a transparent substrate. In some embodiments, the substrate comprises glass or a transparent polymer including but not limited to acrylic and / or polycarbonate. In some embodiments, the substrate comprises a glass sheet. In some embodiments, the glass sheet comprises ultra-thin glass (e.g., willow glass) or glass that is typically found in window applications (e.g., 6mm thick glass sheets). While the substrate itself may be relatively transparent, one or more coatings may be deposited onto the substrate, before or after coupling of the aerogel to the substrate, such that the transparency of the substrate is reduced. For example, in some embodiments, the substrate may also have a low emissivity (low-E) coating. A low emissivity coating may reduce the transmittance of the substrate, but is still desirable in many window applications. In some embodiments, the substrate is a laminated substrate and / or a patterned substrate.

[0067] The substrate may have an appropriate size and thickness suitable for interior and / or exterior window applications. Accordingly, the substrate may be suitable in insulated glass units (IGUs) or the like. In some embodiments, the substrate has a size that is substantially the same as the size of the aerogel. In some embodiments, the substrate has any of a variety of suitable thicknesses. In some embodiments, the thickness of the substrate is greater than or equal to 0.1 mm, greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 2 mm, greater than or equal to 3 mm, greater than or equal to 4 mm, greater than or equal to 5 mm, or greater than or equal to 6 mm. In some embodiments, the thickness of the substrate is less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4 mm, less than or equalto 3 mm, less than or equal to 2 mm, less than or equal to 1 mm, less than or equal to 0.5 mm, and / or less than or equal to 0.1 mm. Combinations of these ranges are possible (e.g., greater than or equal to 0.1 mm and less than or equal to 6 mm). Other ranges are also possible.

[0068] The substrates described herein may undergo any of a variety of treatments and / or processes to render the substrates more desirable for window applications. In some embodiments, the substrate may be tempered, annealed, and / or heat treated. As one example, tempered glass when fractured creates fractured pieces that are typically not as sharp as fractured pieces derived from non-tempered glass. Tempered glass may be therefore desirable because it is safer after a fracture event than non-tempered glass.

[0069] In some embodiments, the article comprises two or more substrates. In some embodiments, the aerogel is coupled to a first substrate and positioned proximate to a second substrate, the second substrate having the same or different material as the first substrate, such that an IGU is formed. A gap may be present between the aerogel and at least one of the substrates. In some embodiments, the gap may be evacuated of any gas once present in the gap, or the gap may be filled with a gas including but not limited to air, argon, nitrogen, or the like. In some embodiments, the IGU comprises an aerogel- substrate composite, wherein the aerogel (e.g., the hydrophobic aerogel) is coupled to one or more substrates. In some embodiments, the aerogel is laminated between the first substrate and the second substrate such that no gap exists between the aerogel and the first and second substrate.

[0070] The following examples are intended to illustrate certain embodiments of the present invention, but do not exemplify the full scope of the invention.

[0071] EXAMPLE 1

[0072] In this example, the hydrophobization of aerogels comprising silica are generally described. Silica aerogels are generally known to be susceptible to water due, at least in part, to their hydrophilicity. Hydrophilic aerogels may undergo changes from a glassy, relatively transparent material to a white, crumbly material upon exposure to water. Without wishing to be bound to any particular theory, water may infiltrate pores of the hydrophilic aerogel causing them to collapse and compromise the optical and / or mechanical properties of the aerogel.

[0073] Accordingly, hydrophobization of otherwise hydrophilic aerogels may be desirable to limit damage to aerogels upon exposure to water.

[0074] Materials and MethodsTo fabricate the aerogel, methanol, tetremethylorthosilicate precursor, and 0.5M aqueous ammonium hydroxide were combined in a reaction vessel in a mass ratio of 5.14:1.32:1, respectively. The resulting mixture was poured into a mold, covered, and allowed to age for 10 minutes. During this process, the mixture underwent gelation, and the consistency (e.g., viscosity) of the mixture was observed to change from a free-flowing solution to a hardened, jello-like consistency. The gels were allowed to age in the mold for 2 additional hours in a larger sealed container filled with methanol vapor so that evaporation from the gel was substantially prevented. The gel was then demolded and submerged in a bath consisting of 85% methanol and 15% 0.5M aqueous ammonium hydroxide (m / m). The bath was heated at 60°C for 16 hours.

[0075] To increase the hydrophobicity of the silica gels, hexamethyldisilazane (HMDZ) was used as a hydrophobization agent. To determine effective concentration of HMDZ solutions, silica gels were submerged in a solution (e.g., a bath) comprising methanol and various mass concentrations (0 wt%, 5 wt%, 10 wt%, and 20 wt%) of HMDZ. The solution was heated to a temperature of 60°C, and the gel was submerged in the solution for 16 hours.

[0076] After exposing the silica gels to the hydrophobization bath, the silica gels were subjected to two 24-hour rounds of solvent exchange using pure methanol. The gels were then loaded into a critical point dryer (CPD). The CPD was charged to a pressure of 1500 psi. Methanol was then removed from the pressure vessel by venting the system at constant pressure. Once the desired methanol concentration was reached, the vessel was then heated to 38 degrees Celsius at constant pressure to achieve supercriticality. After the desired temperature was reached, the supercritical carbon dioxide was vented at elevated temperatures resulting in dried aerogels. The aerogels were then annealed at 200 degrees Celsius for 24 hours.

[0077] Then, the hydrophobicity of the aerogels were evaluated by measuring the haze after exposing the aerogels to a high humidity environment for 24 hours. The high humidity environment involved placing the aerogels in a closed container comprising water. The relativity humidity of this environment approached 100%.

[0078] To determine effective durations of which the aerogel was submerged in the bath, silica gels were submerged in a solution comprising 5 wt% HMDZ and methanol for a variety of durations including 2 hours, 4 hours, 6 hours, and 8 hours. The solution was heated to a temperature of 60 °C. Then, the hydrophobicity of the aerogel was evaluated by measuring the haze after exposing the aerogel to a high humidity environment for 24 hours and water contact angle.

[0079] ResultsHaze data is shown in FIG. 2A depicting the haze through aerogels treated with HMDZ solutions of various concentrations before and after exposure to a high humidity environment. The results indicate that exposing aerogels to a 5 wt% HMDZ solution in methanol does not substantially change the haze through the aerogel and results in a relatively high water contact angle, as described below. The results also indicate that higher concentrations (e.g., 10 wt% or 15 wt%) may lead to increased haze through the aerogel after exposure to the solution. FIG. 2B shows that an aerogel treated with a 5 wt% HMDZ solution exhibits a water contact angle of 120 degrees, while FIG. 2C shows that aerogels that have not been exposed to HMDZ form a white, hazy spot at the location of the water droplet.

[0080] To evaluate effective durations of the HMDZ bath, aerogels were exposed to a 5 wt% HMDZ solution for a variety of durations. The resulting haze through the aerogel and water contact angles after such exposures are shown in FIGS. 3A-3B. It should be noted that exposure for 0 hours indicates a control sample that was not exposed to HMDZ. Aerogels exposed to a HMDZ solution for 4 hours showed relatively minimal changes to haze after exposure to high humidity environments and had a water contact angles of approximately 120 degrees.

[0081] Additional experimentation was carried out to determine the thermal stability of the hydrophobization treatment. Hydrophobic aerogels were prepared as described above and subjected to 24-hour periods of annealing at 250°C, 225°C, and 200°C. A preliminary experiment showed that annealing at 300°C erased hydrophobic treatment. Annealing at 250°C also erased hydrophobicity and 225 °C resulted in partial erasure. However, gels annealed at 200°C retained their hydrophobicity, indicating that the treatment is thermally stable up to 200 degrees Celsius.

[0082] While several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily envision a variety of other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each of such variations and / or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of theappended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, and / or methods, if such features, systems, articles, materials, and / or methods are not mutually inconsistent, is included within the scope of the present invention.

[0083] The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.”

[0084] The phrase “and / or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Other elements may optionally be present other than the elements specifically identified by the “and / or” clause, whether related or unrelated to those elements specifically identified unless clearly indicated to the contrary. Thus, as a non-limiting example, a reference to “A and / or B,” when used in conjunction with open-ended language such as “comprising” can refer, in one embodiment, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.

[0085] As used herein in the specification and in the claims, “or” should be understood to have the same meaning as “and / or” as defined above. For example, when separating items in a list, “or” or “and / or” shall be interpreted as being inclusive, i.e., the inclusion of at least one, but also including more than one, of a number or list of elements, and, optionally, additional unlisted items. Only terms clearly indicated to the contrary, such as “only one of’ or “exactly one of,” or, when used in the claims, “consisting of,” will refer to the inclusion of exactly one element of a number or list of elements. In general, the term “or” as used herein shall only be interpreted as indicating exclusive alternatives (i.e. “one or the other but not both”) when preceded by terms of exclusivity, such as “either,” “one of,” “only one of,” or “exactly one of.” “Consisting essentially of,” when used in the claims, shall have its ordinary meaning as used in the field of patent law.

[0086] As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition alsoallows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, “at least one of A and B” (or, equivalently, “at least one of A or B,” or, equivalently “at least one of A and / or B”) can refer, in one embodiment, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

[0087] As used herein, “wt%” is an abbreviation of weight percentage. As used herein, “at%” is an abbreviation of atomic percentage.

[0088] Some embodiments may be embodied as a method, of which various examples have been described. The acts performed as part of the methods may be ordered in any suitable way.

[0089] Accordingly, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include different (e.g., more or less) acts than those that are described, and / or that may involve performing some acts simultaneously, even though the acts are shown as being performed sequentially in the embodiments specifically described above.

[0090] Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements.

[0091] In the claims, as well as in the specification above, all transitional phrases such as “comprising,” “including,” “carrying,” “having,” “containing,” “involving,” “holding,” and the like are to be understood to be open-ended, i.e., to mean including but not limited to. Only the transitional phrases “consisting of’ and “consisting essentially of’ shall be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

CLAIMSWhat is claimed is:

1. An article, comprising:an aerogel comprising silica, wherein haze through at least a portion of the aerogel is less than or equal to 15%, and the aerogel has a water contact angle greater than or equal to 90 degrees.

2. An article, comprising:an aerogel comprising silica, wherein haze through at least a portion of the aerogel is less than or equal to 15%, and when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for a duration of 1 hour, the aerogel is configured to uptake an amount of moisture that is less than or equal to 10% of the total mass of the aerogel prior to exposure to the environment.

3. An article, comprising:an aerogel comprising silica, wherein the aerogel, when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for 1 hour, has a haze of less than or equal to 15%.

4. An article, comprising:an aerogel comprising silica, wherein the aerogel has a volume greater than or equal to 800 cm3and a contact angle between the aerogel and a water droplet adjacent to the aerogel is greater than or equal to 90 degrees.

5. An article, comprising:an aerogel having a water contact angle greater than or equal to 90 degrees, and wherein haze through at least a portion of the aerogel is less than or equal to 15%.

6. The article of any one of claims 1-5, wherein at least a portion of the aerogel is exposed to a hydrophobization agent such that at least a portion of the aerogel is hydrophobic.

7. The article of claim 6, wherein the hydrophobization agent comprises methyltrimethoxysilane (MTMS), hexamethyldisiloxane (HMDSO), and / or hexamethyldisilazane (HMDZ).

8. The article of any one of claims 1-7, wherein the water contact angle of the aerogel is greater than or equal to 90 degrees, after the aerogel is exposed to a temperature of greater than or equal to 190 degrees Celsius for at least 22 hours.

9. The article of any one of claims 1-8, wherein the water contact angle of the aerogel is greater than or equal to 90 degrees, after the aerogel is exposed to ultraviolet light for at least 22 hours.

10. The article of any one of claims 1-9, wherein, when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for 1 hour, the aerogel has a haze of less than or equal to 10%.

11. The article of any one of claims 1-10, wherein, when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for 1 hour, the aerogel has a haze of less than or equal to 2%.

12. The article of any one of claims 1-11, wherein, when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for a duration of 1 hour, the aerogel is configured to uptake an amount of moisture that is less than or equal to 4% of the total mass of the aerogel prior to exposure to the environment.

13. The article of any one of claims 1-12, wherein, when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for a duration of 1 hour, the aerogel is configured to uptake an amount ofmoisture that is less than or equal to 3% of the total mass of the aerogel prior to exposure to the environment.

14. The article of any one of claims 1-13, wherein, when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for a duration of 1 hour, the aerogel is configured to uptake an amount of moisture that is less than or equal to 2% of the total mass of the aerogel prior to exposure to the environment.

15. The article of any one of claims 1-14, wherein the aerogel is monolithic.

16. The article of any one of claims 1-15, wherein the aerogel has a volume greater than or equal to 400 cm3.

17. The article of any one of claims 1-16, wherein the aerogel has a volume greater than or equal to 1000 cm3.

18. The article of any one of claims 1-17, wherein the aerogel has a volume greater than or equal to 1200 cm3.

19. The article of any one of claims 1-18, wherein the aerogel has a thermal conductivity less than or equal to 25 mW / mK.

20. The article of any one of claims 1-19, wherein the aerogel has a thermal conductivity less than or equal to 20 mW / mK.

21. The article of any one of claims 1-20, wherein the aerogel has a thermal conductivity less than or equal to 16 mW / mK.

22. The article of any one of claims 1-21, the article further comprising a first substrate and a second substrate, wherein the aerogel is positioned between the first and second substrate.

23. An insulated glass unit comprising the article of any one of claims 1-22.

24. The article of any one of claims 1-23, wherein the aerogel has a mean scattering radius less than or equal to 10 nm.

25. The article of any one of claims 1-24, wherein the aerogel has a mean pore radius of less than or equal to 5 nm.

26. The article of any one of claims 1-25, wherein the aerogel has a mean particle radius of less than or equal to 2 nm.

27. The article of any one of claims 1-26, wherein the aerogel, when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for 1 hour, exhibits no more than a 15% increase in haze.

28. The article of any one of claims 1-27, wherein the aerogel, when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for 1 hour, exhibits no more than a 10% increase in haze.

29. The article of any one of claims 1-28, wherein the aerogel, when exposed to an environment having a temperature of 25 degrees Celsius, a pressure of 1 atm, and a relative humidity of 40% for 1 hour, exhibits no more than a 5% increase in haze

Images