Process for the preparation of alkali metal salts of oxalate-based chelating structures

Abstract

The application belongs to the technical field of compound preparation, and particularly relates to a preparation method of an alkali metal salt of an oxalate chelate structure, at least comprising the following steps: mixing tris(trimethylsilyl) phosphate, an oxalate and a phosphorus-containing or boron-containing fluorine compound in a first organic solvent, stirring and heating to obtain lithium phosphate, trimethyl fluorosilane gas, and difluorobisoxalate phosphate or difluorooxalate borate, filtering the reaction solution to obtain lithium phosphate solid and a difluorobisoxalate phosphate solution or a difluorooxalate borate solution; adding a second organic solvent for recrystallization after concentration; and obtaining difluorobisoxalate phosphate or difluorooxalate borate solid after filtration, and drying the solid under reduced pressure to obtain a finished product. The process is simple, and the cost is low. By-products lithium phosphate, potassium fluoride and hexamethyldisiloxane can be directly sold as products after purification. Therefore, the application has an atomic utilization rate close to 100%, no invalid waste, less three-waste emissions, and is friendly to the environment.

Description

Technical Field

[0001] This invention belongs to the field of compound preparation technology, specifically relating to a method for preparing alkali metal salts with oxalic acid group chelate structure, specifically including methods for preparing lithium difluorobis(oxalato)phosphate (sodium) and lithium difluoro(oxalato)borate (sodium). Background Technology

[0002] Electrolyte salts with oxalic acid groups as chelating agents and boron and phosphorus as central atoms are used in lithium-ion or sodium-ion battery systems. By forming a stable passivation film, they improve the structure and composition of the interfacial film, which helps reduce the battery's internal resistance and extend its lifespan, and are widely used, especially in power battery systems. The main oxalic acid group chelated electrolyte salts are lithium difluorobis(oxalato)phosphate (sodium) and lithium difluoro(oxalato)borate (sodium).

[0003] In the existing technology, the preparation processes of lithium difluorobis(oxalato)phosphate mainly include the following:

[0004] The first method involves reacting lithium oxalate with phosphorus pentafluoride (or producing hydrogen fluoride in situ with phosphorus pentachloride and anhydrous hydrogen fluoride). However, this method also generates lithium hexafluorophosphate, and the two products have similar solubility in the solvent, making separation difficult.

[0005] The second method involves reacting lithium hexafluorophosphate, anhydrous oxalic acid, and a hydrogen fluoride "scavenger," where the anhydrous hydrogen fluoride "scavenger" includes silicon tetrachloride, alkylchlorosilanes, and silazanes. However, this method suffers from high product acidity and chloride ion contamination, making purification difficult.

[0006] The third method involves preparing lithium difluorobis(oxalato)borate and lithium difluorooxalato)borate from lithium hexafluorophosphate and lithium bis(oxalato)borate under Lewis acid catalysis. However, the similar solubility of the two products necessitates multiple recrystallizations for effective separation. The preparation method for lithium difluorooxalatoborate is similar to that for lithium difluorobis(oxalato)phosphate, except that lithium hexafluorophosphate is replaced with lithium tetrafluoroborate, while other reaction conditions remain the same.

[0007] As can be seen from the above, the various preparation methods of lithium difluorobis(oxalato)phosphate and lithium difluoro(oxalato)borate in the existing technology have technical problems such as high separation difficulty and poor product quality.

[0008] In view of this, the present invention aims to provide a method for preparing alkali metal salts with oxalic acid group chelate structure. The process is simple and low-cost, and the byproducts, lithium phosphate, potassium fluoride, and hexamethyldisiloxane, can be directly sold as products after purification. Therefore, the present invention achieves near 100% atom utilization, generates no ineffective waste, produces minimal waste, and is environmentally friendly. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing alkali metal salts with oxalic acid group chelate structures. This method is simple, low-cost, and the byproducts—lithium phosphate, potassium fluoride, and hexamethyldisiloxane—can be directly sold as finished products after purification. Therefore, this invention achieves near 100% atom utilization, generates no waste, produces minimal emissions, and is environmentally friendly.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for preparing an oxalic acid group chelated alkali metal salt includes at least the following steps:

[0012] The first step involves mixing tris(trimethylsilyl) phosphate (the preparation method of which can be found in CN101870711 B), oxalate, and a phosphorus- or boron-containing fluorine compound in a first organic solvent, stirring, heating, and reacting to obtain lithium phosphate, trimethylfluorosilane gas, and difluorobis(oxalate) phosphate or difluorobis(oxalate) borate. The reaction solution is filtered to obtain solid lithium phosphate and difluorobis(oxalate) phosphate solution or difluorobis(oxalate) borate solution.

[0013] The second step involves concentrating the difluorobis(oxalate) phosphate solution or difluorobis(oxalate) borate solution, then adding a second organic solvent for recrystallization. After filtration, the difluorobis(oxalate) phosphate solid or difluorobis(oxalate) borate solid is obtained, and then dried under reduced pressure to obtain the final product.

[0014] In this invention, the oxalic acid group chelated alkali metal salts are shown in structures (Ⅰ) and (Ⅱ):

[0015]

[0016] Where M = Li and Na.

[0017] As an improvement to the preparation method of the oxalic acid group chelate structure alkali metal salt of the present invention, the first organic solvent in the first step is at least one selected from acetonitrile, acetone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl acetate, propyl acetate, butyl acetate, diethyl ether, methyl tert-butyl ether, and ethylene glycol dimethyl ether.

[0018] As an improvement to the preparation method of the oxalate group chelate structure alkali metal salt of the present invention, the oxalate in the first step is lithium oxalate or sodium oxalate.

[0019] As an improvement to the preparation method of the oxalic acid group chelate structure alkali metal salt of the present invention, the phosphorus-containing fluorine compound in the first step is lithium hexafluorophosphate or sodium hexafluorophosphate.

[0020] As an improvement to the preparation method of the oxalate group chelated alkali metal salt of the present invention, the boron-containing fluorine compound in the first step is boron trifluoride or a boron trifluoride complex.

[0021] As an improvement to the preparation method of the oxalate group chelated alkali metal salt of the present invention, the boron trifluoride complex is at least one of the following: boron trifluoride dimethyl carbonate complex, boron trifluoride diethyl carbonate complex, boron trifluoride methyl ethyl carbonate complex, boron trifluoride diethyl ether complex, boron trifluoride acetonitrile complex, and tetrafluoroborate (a complex of boron trifluoride and a fluorine-containing salt).

[0022] As an improvement to the preparation method of the oxalic acid group chelated alkali metal salt of the present invention, the tetrafluoroborate is lithium tetrafluoroborate or sodium tetrafluoroborate.

[0023] As an improvement to the preparation method of the oxalate group chelated alkali metal salt of the present invention, in the first step, the stoichiometric molar ratio of the tris(trimethylsilyl)phosphate, oxalate and phosphorus- or boron-containing fluorine compound is 1:1:1 to 1:1.5:1.5; the reaction temperature of the first step is 25 to 80°C.

[0024] As an improvement to the preparation method of the oxalic acid group chelated alkali metal salt of the present invention, the second organic solvent in the second step is at least one selected from dichloromethane, dichloroethane, toluene, hexane, cyclohexane, and petroleum ether.

[0025] As an improvement to the preparation method of the oxalic acid group chelate structure alkali metal salt of the present invention, the trimethylfluorosilane gas obtained by the reaction is adsorbed by potassium hydroxide alkaline solution to obtain potassium fluoride and hexamethyldisiloxane.

[0026] Compared to existing technologies, the raw materials used in this invention are readily available and inexpensive. The production process is simple, avoids hazardous unit operations involving high temperature and high pressure, and the products are easy to separate and purify, achieving near 100% atom utilization. There is no ineffective waste, resulting in minimal emissions and making it environmentally friendly. Furthermore, the byproducts—lithium phosphate, potassium fluoride, and hexamethyldisiloxane—can be directly sold as finished products after purification. Therefore, this invention offers near 100% atom utilization, eliminates ineffective waste, minimizes emissions, and is environmentally friendly. Attached Figure Description

[0027] Figure 1 The nuclear magnetic fluorine spectrum of lithium difluorobis(oxalato) phosphate prepared in Example 1.

[0028] Figure 2 The nuclear magnetic fluorine spectrum of lithium difluorooxalateborate prepared in Example 3. Detailed Implementation

[0029] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0030] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0031] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0032] Example 1

[0033] This embodiment provides a method for preparing lithium difluorobis(oxalato)phosphate, the principle of which is as follows:

[0034]

[0035] It includes the following steps:

[0036] In the first step, 1000 mL of dimethyl carbonate, 157.5 g (0.5 mol) of tris(trimethylsilyl) phosphate, and 76.5 g (0.75 mol) of lithium oxalate were added to a 2000 mL reaction flask. Then, 57 g (0.375 mol) of lithium hexafluorophosphate in a dimethyl carbonate solution was added in portions. The mixture was heated to 60 °C and stirred for 12 hours. The generated trimethylfluorosilane was adsorbed using potassium hydroxide solution. The mixture was filtered under reduced pressure to obtain a white lithium phosphate solid and a colorless filtrate. The lithium phosphate was washed three times with dimethyl carbonate, and the filtrates were combined. The filter residue was dried under reduced pressure to obtain 56.8 g of a white solid.

[0037] In the second step, the filtrate was concentrated under reduced pressure and then recrystallized with dichloromethane. After filtration and drying under reduced pressure, 92.6 g of a white solid was obtained, with a yield of 98%. The recovered dimethyl carbonate solution was reused in the next cycle. The lithium difluorobis(oxalato)phosphate obtained in this example had a purity of 99.9%, Cl < 5 ppm, and SO42-. 2- <5ppm, K<1ppm, Mg<1ppm, Ca<1ppm, Fe<1ppm, Hg ND, Cr<1ppm.

[0038] In this process, trimethylfluorosilane is adsorbed with potassium hydroxide solution, and after the reaction, the mixture is separated to obtain hexamethyldisiloxane (purity 99.5%) and potassium fluoride aqueous solution. The potassium fluoride aqueous solution is concentrated and crystallized, and then centrifuged to obtain white crystals.

[0039] The NMR spectrum of lithium difluorobis(oxalato)phosphate prepared in this embodiment is as follows: Figure 1 As shown.

[0040] Example 2

[0041] This embodiment provides a method for preparing sodium difluorobis(oxalato) phosphate, the principle of which is as follows:

[0042]

[0043] It includes the following steps:

[0044] In the first step, 1000 mL of dimethyl carbonate, 157.5 g (0.5 mol) of tris(trimethylsilyl) phosphate, and 100.5 g (0.75 mol) of sodium oxalate were added to a 2000 mL reaction flask. Then, 63 g (0.375 mol) of sodium hexafluorophosphate in a dimethyl carbonate solution was added in portions. The mixture was heated to 60 °C and stirred for 12 hours. The generated trimethylfluorosilane was adsorbed using potassium hydroxide solution. The mixture was filtered under reduced pressure to obtain a white sodium phosphate solid and a colorless filtrate. The white sodium phosphate solid was washed three times with dimethyl carbonate, and the filtrates were combined. The residue was dried under reduced pressure to obtain 80.4 g of a white solid.

[0045] In the second step, the filtrate was concentrated under reduced pressure and then recrystallized with dichloroethane. After filtration and drying under reduced pressure, 98.5 g of a white solid was obtained, with a yield of 98%. The recovered dimethyl carbonate solution was reused in the next cycle. The sodium difluorobis(oxalato)phosphate prepared in this example had a purity of 99.9%, Cl < 5 ppm, and SO42-. 2- <5ppm, K<1ppm, Mg<1ppm, Ca<1ppm, Fe<1ppm, Hg ND, Cr<1ppm.

[0046] In this process, trimethylfluorosilane is adsorbed with potassium hydroxide solution, and after the reaction, the mixture is separated to obtain hexamethyldisiloxane (purity 99.5%) and potassium fluoride aqueous solution. The potassium fluoride aqueous solution is concentrated and crystallized, and then centrifuged to obtain white crystals.

[0047] Example 3

[0048] This embodiment provides a method for preparing lithium difluorooxalate borate, the principle of which is as follows:

[0049]

[0050] It includes the following steps:

[0051] In the first step, 1000 mL of diethyl carbonate, 157.5 g (0.5 mol) of tris(trimethylsilyl) phosphate, and 76.5 g (0.75 mol) of lithium oxalate were added to a 2000 mL reaction flask. A solution of 70.5 g (0.75 mol) of lithium tetrafluoroborate in diethyl carbonate was added in portions. The mixture was heated to 60 °C and stirred for 12 hours. The generated trimethylfluorosilane was adsorbed using potassium hydroxide solution. The mixture was filtered under reduced pressure to obtain a white lithium phosphate solid and a colorless filtrate. The white lithium phosphate solid was washed three times with diethyl carbonate, and the filtrates were combined. The filter residue was dried under reduced pressure to obtain 57.4 g of a white solid.

[0052] In the second step, the filtrate was concentrated under reduced pressure and then recrystallized with dichloroethane. After filtration and drying under reduced pressure, 106.9 g of white solid was obtained, with a yield of 99%. The recovered diethyl carbonate solution was reused in the next cycle. The lithium difluorooxalate borate prepared in this example had a purity of 99.9%, Cl < 5 ppm, and SO42-. 2- <5ppm, K<1ppm, Mg<1ppm, Ca<1ppm, Fe<1ppm, Hg ND, Cr<1ppm.

[0053] In this process, trimethylfluorosilane is adsorbed with potassium hydroxide solution, and after the reaction, the mixture is separated to obtain hexamethyldisiloxane (purity 99.5%) and potassium fluoride aqueous solution. The potassium fluoride aqueous solution is concentrated and crystallized, and then centrifuged to obtain white crystals.

[0054] The NMR spectrum of lithium difluorooxalatoborate prepared in this embodiment is as follows: Figure 2 As shown.

[0055] Example 4

[0056] This embodiment provides a method for preparing sodium difluorooxalate borate, the principle of which is as follows:

[0057]

[0058] It includes the following steps:

[0059] In the first step, 1000 mL of ethyl acetate, 157.5 g (0.5 mol) of tris(trimethylsilyl)phosphate, and 201 g (0.75 mol) of sodium oxalate were added to a 2000 mL reaction flask. A solution of 165 g (0.75 mol) of sodium tetrafluoroborate in diethyl carbonate was added in portions. The mixture was heated to 60 °C and stirred for 12 hours. The generated trimethylfluorosilane was adsorbed using potassium hydroxide solution. The mixture was filtered under reduced pressure to obtain a white sodium phosphate solid and a colorless filtrate. The white lithium phosphate solid was washed three times with diethyl carbonate, and the filtrates were combined. The filter residue was dried under reduced pressure to obtain 81.2 g of a white solid.

[0060] In the second step, the filtrate was concentrated under reduced pressure and then recrystallized with dichloroethane. After filtration and drying under reduced pressure, 118.8 g of a white solid was obtained, with a yield of 99%. The recovered diethyl carbonate solution was reused in the next cycle. The sodium difluorooxalate borate obtained in this example had a purity of 99.9%, Cl < 5 ppm, and SO42-. 2- <5ppm, K<1ppm, Mg<1ppm, Ca<1ppm, Fe<1ppm, Hg ND, Cr<1ppm.

[0061] In this process, trimethylfluorosilane is adsorbed with potassium hydroxide solution, and after the reaction, the mixture is separated to obtain hexamethyldisiloxane (purity 99.5%) and potassium fluoride aqueous solution. The potassium fluoride aqueous solution is concentrated and crystallized, and then centrifuged to obtain white crystals.

[0062] Example 5

[0063] This embodiment provides a method for preparing lithium difluorobis(oxalato)phosphate, which includes the following steps:

[0064] In the first step, 1000 mL of methyl ethyl carbonate, 0.5 mol of tris(trimethylsilyl) phosphate, and 0.77 mol of lithium oxalate were added to a 2000 mL reaction flask. A solution of 0.378 mol of lithium hexafluorophosphate in methyl ethyl carbonate was added in portions. The mixture was heated to 70 °C and stirred for 8 hours. The generated trimethylfluorosilane was adsorbed using potassium hydroxide solution. The mixture was filtered under reduced pressure to obtain a white lithium phosphate solid and a colorless filtrate. The lithium phosphate was washed three times with methyl ethyl carbonate, and the filtrates were combined. The residue was dried under reduced pressure to obtain a white solid.

[0065] In the second step, the filtrate is concentrated under reduced pressure, then toluene is added for recrystallization. After filtration, the solution is dried under reduced pressure to obtain a white solid. The recovered dimethyl carbonate solution is then reused in the next cycle.

[0066] In this process, trimethylfluorosilane is adsorbed with potassium hydroxide solution, and after the reaction, the mixture is separated to obtain hexamethyldisiloxane and potassium fluoride aqueous solution. The potassium fluoride aqueous solution is concentrated and crystallized, and then centrifuged to obtain white crystals.

[0067] Example 6

[0068] This embodiment provides a method for preparing sodium difluorobis(oxalato) phosphate, the principle of which is as follows:

[0069]

[0070] It includes the following steps:

[0071] In the first step, 1000 mL of acetonitrile, 0.5 mol of tris(trimethylsilyl)phosphate, and 0.78 mol of sodium oxalate were added to a 2000 mL reaction flask. A 0.38 mol sodium hexafluorophosphate solution was added in portions to the acetonitrile solution. The mixture was heated to 55 °C and stirred for 9 hours. The generated trimethylfluorosilane was adsorbed using potassium hydroxide solution. The mixture was filtered under reduced pressure to obtain a white sodium phosphate solid and a colorless filtrate. The white sodium phosphate solid was washed three times with acetonitrile, and the filtrates were combined. The residue was dried under reduced pressure to obtain a white solid.

[0072] In the second step, the filtrate is concentrated under reduced pressure, then hexane is added for recrystallization. After filtration, the solution is dried under reduced pressure to obtain a white solid. The recovered dimethyl carbonate solution is then reused in the next cycle.

[0073] In this process, trimethylfluorosilane is adsorbed with potassium hydroxide solution, and after the reaction, the mixture is separated to obtain hexamethyldisiloxane and potassium fluoride aqueous solution. The potassium fluoride aqueous solution is concentrated and crystallized, and then centrifuged to obtain white crystals.

[0074] Example 7

[0075] This embodiment provides a method for preparing lithium difluorooxalate borate, which includes the following steps:

[0076] In the first step, 1000 mL of propyl acetate, 0.5 mol of tris(trimethylsilyl)phosphate, and 0.78 mol of lithium oxalate were added to a 2000 mL reaction flask. A solution of 0.76 mol of boron trifluoride in propyl acetate was added in portions. The mixture was heated to 40 °C and stirred for 10 hours. The generated trimethylfluorosilane was adsorbed using potassium hydroxide solution. The mixture was filtered under reduced pressure to obtain a white lithium phosphate solid and a colorless filtrate. The white lithium phosphate solid was washed three times with propyl acetate, and the filtrates were combined. The filter residue was dried under reduced pressure to obtain a white solid.

[0077] The second step involves concentrating the filtrate under reduced pressure, adding cyclohexane for recrystallization, filtering, and drying under reduced pressure to obtain a white solid.

[0078] In this process, trimethylfluorosilane is adsorbed with potassium hydroxide solution, and after the reaction, the mixture is separated to obtain hexamethyldisiloxane and potassium fluoride aqueous solution. The potassium fluoride aqueous solution is concentrated and crystallized, and then centrifuged to obtain white crystals.

[0079] Example 8

[0080] This embodiment provides a method for preparing sodium difluorooxalate borate, which includes the following steps:

[0081] In the first step, 1000 mL of diethyl ether, 157.5 g (0.5 mol) of tris(trimethylsilyl) phosphate, and 201 g (0.75 mol) of sodium oxalate were added to a 2000 mL reaction flask. 0.78 mol of boron trifluoride diethyl ether complex was added in portions. The mixture was heated to 45 °C and stirred for 7 hours. The generated trimethylfluorosilane was adsorbed using potassium hydroxide solution. The mixture was filtered under reduced pressure to obtain a white sodium phosphate solid and a colorless filtrate. The white lithium phosphate solid was washed three times with diethyl carbonate, and the filtrates were combined. The filter residue was dried under reduced pressure to obtain a white solid.

[0082] In the second step, the filtrate is concentrated under reduced pressure, then recrystallized with petroleum ether, filtered, and dried under reduced pressure to obtain a white solid. The recovered diethyl carbonate solution is then reused in the next cycle.

[0083] In this process, trimethylfluorosilane is adsorbed with potassium hydroxide solution, and after the reaction, the mixture is separated to obtain hexamethyldisiloxane and potassium fluoride aqueous solution. The potassium fluoride aqueous solution is concentrated and crystallized, and then centrifuged to obtain white crystals.

[0084] The technical solution of this invention uses readily available and inexpensive raw materials, has a simple production process, does not involve dangerous unit operations involving high temperature and high pressure, and the product is easy to separate and purify, with a near 100% atomic utilization rate.

[0085] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and changes to the present invention should also fall within the protection scope of the claims of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A method for preparing an alkali metal salt with an oxalic acid group chelate structure, characterized in that, It should include at least the following steps: The first step involves mixing tris(trimethylsilyl) phosphate, oxalate, and a phosphorus- or boron-containing fluorine compound in a first organic solvent, stirring, heating, and reacting to obtain lithium phosphate, trimethylfluorosilane gas, and difluorobis(oxalate) phosphate or difluorobis(oxalate) borate. The reaction solution is filtered to obtain solid lithium phosphate, and difluorobis(oxalate) phosphate solution or difluorobis(oxalate) borate solution. The second step involves concentrating the difluorobis(oxalate) phosphate solution or difluorobis(oxalate) borate solution, then adding a second organic solvent for recrystallization; after filtration, the difluorobis(oxalate) phosphate solid or difluorobis(oxalate) borate solid is obtained, and then dried under reduced pressure to obtain the final product. The oxalate mentioned in the first step is lithium oxalate or sodium oxalate; The phosphorus-containing fluorine compound in the first step is lithium hexafluorophosphate or sodium hexafluorophosphate; In the first step, the boron-containing fluorine compound is boron trifluoride or a boron trifluoride complex; The boron trifluoride complex is at least one of the following: boron trifluoride dimethyl carbonate complex, boron trifluoride diethyl carbonate complex, boron trifluoride methyl ethyl carbonate complex, boron trifluoride diethyl ether complex, boron trifluoride acetonitrile complex, and tetrafluoroborate. The tetrafluoroborate is lithium tetrafluoroborate or sodium tetrafluoroborate.

2. The method for preparing alkali metal salts with oxalic acid group chelate structure according to claim 1, characterized in that: The first organic solvent mentioned in the first step is at least one selected from acetonitrile, acetone, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl acetate, propyl acetate, butyl acetate, diethyl ether, methyl tert-butyl ether, and ethylene glycol dimethyl ether.

3. The method for preparing alkali metal salts with oxalic acid group chelate structure according to claim 1, characterized in that: In the first step, the stoichiometric molar ratio of the tris(trimethylsilyl)phosphate, oxalate, and phosphorus- or boron-containing fluorine compound is 1: 1:1 to 1:1.5:1.5; the reaction temperature of the first step is 25 to 80℃.

4. The method for preparing alkali metal salts with oxalic acid group chelate structure according to claim 1, characterized in that: The second organic solvent mentioned in the second step is at least one of dichloromethane, dichloroethane, toluene, hexane, cyclohexane, and petroleum ether.

5. The method for preparing alkali metal salts with oxalic acid group chelate structure according to claim 1, characterized in that: The trimethylfluorosilane gas obtained from the reaction was adsorbed by potassium hydroxide alkaline solution to obtain potassium fluoride and hexamethyldisiloxane.

Images