Preparation method of multifunctional full-biomass aerogel with light-heat conversion capability

Abstract

The application discloses a preparation method of multifunctional full-biomass aerogel with light-heat conversion capability, and the multifunctional full-biomass aerogel with light-heat conversion capability is obtained through the following steps: cross-linking cellulose nanofibers with hydroxyapatite nanowires, adding inkfish powder as an optical absorption material, and then freeze-drying; the aerogel prepared by the application has excellent light-heat conversion efficiency, excellent mechanical stability and chemical stability, low cost, simple preparation process, and uses full-biomass materials, and has the advantages of environmental friendliness, no secondary pollution, non-toxicity and harmlessness, and simple preparation process, and has a wide application prospect in seawater desalination, wastewater treatment, organic dye solution treatment and oil-water separation.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of materials, and relates to a water treatment biomass aerogel, in particular to a preparation method of a multifunctional full-biomass aerogel with light-heat conversion capability. BACKGROUND

[0002] Water is the most important natural resource on earth, and is closely related to human survival environment and society. Three quarters of the total area of the earth is covered by water, but seawater accounts for 97.5%, and freshwater resources only account for 2.5%. Industrialization and the rapid growth of population have led to serious water pollution and shortage of freshwater resources. Water pollution and shortage of freshwater resources make it a hot spot to extract clean freshwater from abundant seawater and treat wastewater. The sources of water pollution include domestic wastewater, factory pollution, use of chemical fertilizers, heavy metal wastewater, medical waste liquid and the like.

[0003] Seawater desalination and wastewater treatment are currently the best methods to solve the shortage of water resources and poor water quality. However, the existing aerogel materials have many problems such as low light absorption, poor light-heat conversion capability, insufficient water transmission capability, poor elastic performance and the like. Ming et al. cleverly assembled a 3D porous macroscopic aerogel monolith by using 2D Ti3C2Tx (MXene) through a graphene oxide (GO) assisted process, as an independent solar-driven GMA, to realize efficient and all-round water purification. (Carbon, 2020, 167, 85-295) Noureen et al. loaded Ag3VO4 nanoparticles on reduced graphene oxide as a carrier, which has the remarkable characteristics of large specific surface area, high porosity and surface roughness. The aerogel is prepared in a simple method and can be used for water purification integrated system of solar steam power generation, photocatalytic degradation / disinfection of organic pollutants and seawater desalination. (Nano Today, 2024, 54, 102130). Wang et al. prepared a MXene-based composite aerogel, which has a porous structure interconnected with each other, wide and high solar absorption, good wettability and photothermal performance. The aerogel is reasonably designed in structure and composition, and the water evaporation heat is reduced. The solar steam generator based on the aerogel shows an excellent water vapor evaporation rate of up to 2.31 kgm -2 h -1 -2 under one sun irradiation. The aerogel also has good adsorption capacity to remove heavy metal ions in water and good antibacterial capacity, which should help to treat the solar steam generator in complex working environment. The above methods have problems such as high price of materials used for preparing the aerogel material, complicated preparation process and the like, which are not conducive to large-scale preparation. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application aims to provide a preparation method of multifunctional full-biomass aerogel with light-heat conversion capability, which has simple preparation process, low cost and can be applied on a large scale.

[0005] The present application is realized by the following technical solutions:

[0006] A preparation method of multifunctional full-biomass aerogel with light-heat conversion capability, cellulose nanofiber and hydroxyapatite nanowire are dissolved in an alkaline solution to form a uniform slurry, then squid powder and a crosslinking agent are added and stirred uniformly, and then the mixture is placed in a refrigerator for freezing, and then the frozen mixture is dried to obtain the multifunctional full-biomass aerogel with light-heat conversion capability; wherein the mass ratio of cellulose nanofiber, hydroxyapatite nanowire and squid powder is (3-4):(1-2):(1-3), and the mass ratio of the alkaline solution to cellulose nanofiber is (90-2):1.

[0007] Further, the alkaline solution is sodium hydroxide and / or potassium hydroxide.

[0008] Further, the crosslinking agent is epichlorohydrin and / or glutaraldehyde.

[0009] Further, the freezing time is 2-10h, and the freeze-drying time is 24-48h.

[0010] Further, the cellulose nanofiber and hydroxyapatite nanowire solution is stirred for 18-24h.

[0011] Further, the cellulose nanofiber is prepared by the following method:

[0012] The cellulose-containing raw material is dried, lignin is removed and extracted with an inorganic solution in a heated oil bath magnetic stirrer, and then the dried material is crushed with a crusher to obtain cellulose nanofiber.

[0013] Further, the cellulose-containing raw material is crop straw, flax, cotton, industrial hemp and wood; the raw material is placed in a vertical air drying oven, the temperature of the oven is 60-100 DEG C, and the drying time is 24-48h.

[0014] Further, the inorganic solution for removing lignin is a mixture of sodium chlorite and acetic acid or a mixture of sodium chlorite and propionic acid; the concentration of the inorganic solution for removing lignin is 0.005-3.0g / mL, and the mass ratio of the inorganic solution for removing lignin to the cellulose-containing raw material after drying is (50-300):1.

[0015] The solvent for extracting the cellulose nanofiber is one or more of a mixture of sodium hydroxide and potassium hydroxide; the concentration of the cellulose nanofiber solution is 0.005-3.0 g / mL, and the mass ratio of the cellulose nanofiber solution to the extracted cellulose is (50-300):1.

[0016] Further, the heating oil bath magnetic stirrer has a holding temperature of 50-200 DEG C and a holding time of 4-20 h.

[0017] Further, the hydroxyapatite nanowire is prepared by the following method: 10 mL of a sodium hydroxide solution with a concentration of 0.05 g / mL, 10 mL of a calcium chloride solution with a concentration of 0.0176 g / mL and 10 mL of a sodium dihydrogen phosphate anhydrous solution with a concentration of 0.023 g / mL are added drop by drop into 7.128 g of oleic acid and 9 mL of anhydrous ethanol under stirring, and hydrothermal reaction is carried out for 12-24 h; a vertical air blast drying oven is used for drying at 180 DEG C for 24 h, and the hydroxyapatite nanowire is obtained.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] The application discloses a preparation method of multifunctional full-biomass aerogel with light-heat conversion capability, which comprises the following steps: mixing and stirring cellulose nanofiber and hydroxyapatite nanowire, adding a crosslinking agent, and finally adding cuttlefish powder to improve the light absorbance, and then mixing, freeze-drying and obtaining the multifunctional full-biomass aerogel with light-heat conversion capability.

[0020] The three-dimensional space network structure of the prepared aerogel can increase the refraction of light, has excellent light-heat conversion efficiency, enhances the light absorption capacity and utilization rate, and avoids energy waste.

[0021] The aerogel has excellent underwater super-oil-repellent performance, can eliminate the influence of oil stains on the surface, and has excellent mechanical stability, almost zero plastic deformation after continuous compression, and excellent evaporation performance.

[0022] The aerogel prepared by the application has excellent photo-thermal conversion efficiency, excellent mechanical stability and chemical stability, low cost, simple preparation process, and all the applied materials are biomass materials, and has the advantages of environmental friendliness, no secondary pollution, non-toxic and harmless, and simple preparation process, and has a wide application prospect in seawater desalination, wastewater treatment, organic dye solution treatment and oil-water separation. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the picture of the aerogel prepared by the application in the working room state and the picture of the highest surface temperature;

[0024] Figure 2 is the mass loss curve of the aerogel prepared by the application under 1 sun;

[0025] Figure 3(a) is the curve of the aerogel prepared by the application applying and releasing external force and the actual picture;

[0026] Figure 3(b) is a schematic diagram of plastic deformation of the aerogel prepared by the application after continuous repeated compression for 5000 times;

[0027] Figure 4 is the schematic diagram of the treatment of water in organic dye by the aerogel prepared by the application;

[0028] (a) is the light absorption waveform diagram of methylene blue solution before and after evaporation;(b) is the light absorption waveform diagram of rhodamine B solution before and after evaporation;

[0029] Figure 5 is the schematic diagram of oil-water separation by the aerogel prepared by the application;

[0030] Figure 6 is the schematic diagram of self-desalination performance of the aerogel prepared by the application;

[0031] Figure 7 is the preparation flow chart of the aerogel of the application;

[0032] Figure 8 is the working mechanism schematic diagram of the aerogel prepared by the application. DETAILED DESCRIPTION

[0033] The application will be further described in detail below in combination with specific examples, which are an explanation of the application rather than a limitation.

[0034] The application discloses a preparation method of a multifunctional full-biomass aerogel with photo-thermal conversion capability, and specifically comprises the following steps:

[0035] Step 1, the raw material containing cellulose is dried, and lignin is removed and extracted with an inorganic solution in a heated oil bath magnetic stirrer, and then freeze-dried and broken by a crusher to obtain cellulose nanofiber;

[0036] Step 2, 10 mL of sodium hydroxide solution, 10 mL of calcium chloride solution and 10 mL of anhydrous sodium dihydrogen phosphate solution are added dropwise into the prepared oleic acid and ethanol solution in sequence, stirred, hydrothermally reacted for 12-24 h, and then freeze-dried to obtain hydroxyapatite nanowires.

[0037] Step 3, the obtained cellulose nanofiber and hydroxyapatite nanowires are dissolved in water, stirred to form a uniform slurry, then squid powder is added, and then a crosslinking agent is added and placed in a refrigerator.

[0038] Step 4, after freeze-drying, a multifunctional biomass aerogel with light-heat conversion capability is obtained.

[0039] (1) The raw material of cellulose nanofiber is placed in a vertical air drying oven, the temperature of the vertical air drying oven is 60-100℃, and the drying time is 24-48h. The dried cellulose raw material is placed into a lignin-removing inorganic solution with a concentration of 0.005-3.0g / mL, and the mass ratio of the lignin-removing inorganic solution to the dried cellulose-containing raw material is 50:1-300:1. The temperature of the heated oil bath magnetic stirrer is 50-200℃, and the holding time is 4-20h. Then the cellulose is extracted, the concentration of the extracted cellulose nanofiber solution is 0.005-3.0g / mL, and the mass ratio of the cellulose solution to the extracted cellulose is 50:1-300:1. The temperature of the heated oil bath magnetic stirrer is 60℃, the holding time is 4h, and the freeze-drying time is 24-48h. The raw material of cellulose nanofiber is derived from crop straw, flax, cotton, industrial hemp and wood, but is not limited to these. The lignin-removing inorganic solution is a mixture of sodium chlorite and acetic acid or a mixture of sodium chlorite and propionic acid. The solvent for extracting cellulose nanofiber is a mixture of one or more of sodium hydroxide and potassium hydroxide.

[0040] (2) 10 mL of sodium hydroxide solution, 10 mL of calcium chloride solution and 10 mL of anhydrous sodium dihydrogen phosphate solution are added dropwise into the prepared oleic acid and ethanol solution in sequence, stirred, hydrothermally reacted for 12-24 h, and then freeze-dried to obtain hydroxyapatite nanowires.

[0041] (3) The extracted cellulose nanofiber and hydroxyapatite nanowire are dissolved in an alkaline solution with a solution concentration of 0.01-2.0 g / mL. The solution of the dissolved cellulose nanofiber and hydroxyapatite nanowire has a cellulose mass ratio of 90:1-2:1, and the crosslinking agent has a solution mass ratio of 1:24-1:6. A uniform slurry is obtained. The inorganic substance added in the dissolving agent is a mixture of one or more of KOH and NaOH. The crosslinking agent of the cellulose nanofiber and hydroxyapatite nanowire is a mixture of one or more of epichlorohydrin and glutaraldehyde.

[0042] (4) The obtained uniform slurry is frozen for 2-10 h, and then freeze-dried, wherein the freeze-drying time is 24-48 h. Finally, a multifunctional full-biomass aerogel with light-heat conversion capability is obtained.

[0043] Example 1

[0044]

[0045]

[0046] The cellulose raw material is placed in an oven for drying, and the temperature of the oven is 60°C. The drying time is 24 h. The mass of the cellulose raw material is 30 g. The dried cellulose raw material is added to a sodium chlorite solution with a concentration of 0.02 g / mL and 2 mL of acetic acid. The temperature of the heating oil bath magnetic stirrer is 90°C, and the holding time is 8 h. After removing the lignin, the cellulose is extracted. The lignin-removed raw material is added to a NaOH solution with a concentration of 0.05 g / mL. The temperature of the heating oil bath magnetic stirrer is 60°C, and the holding time is 4 h. The freeze-drying time is 24 h.

[0047] Oleic acid 7.128 g, anhydrous ethanol 9 mL, sodium hydroxide solution concentration 0.05 g / mL, calcium chloride solution concentration 0.0176 g / mL, anhydrous sodium dihydrogen phosphate concentration 0.023 g / mL, respectively, 10 mL is added in turn. The temperature of the vertical air drying oven is 180°C, and the reaction time is 24 h. The cellulose nanofiber and hydroxyapatite nanowire are dissolved in a NaOH solution with a concentration of 0.1 g / mL (25 mL). The stirring time is 18 h. 2 mL of glutaraldehyde is added. After adding 0.3 g of cuttlefish powder, the freezing time is 5 h, and the freeze-drying time is 48 h. Finally, a multifunctional full-biomass aerogel with light-heat conversion capability is obtained. As shown in FIG. 1, under the intensity of 1 sun, the surface temperature of the hydrogel rapidly rises to 41.9°C. It has good light-heat conversion capability. Figure 1

[0048] Example 2

[0049]

[0050] ​The cellulose raw material was dried in an oven at a temperature of 80°C for 36 h. The cellulose raw material had a mass of 30 g. The dried cellulose raw material was added to a sodium chlorite solution with a concentration of 0.1 g / mL and 2 mL of acetic acid. The mixture was heated in an oil bath magnetic stirrer at a temperature of 120°C for 6 h. After the lignin was removed, the cellulose was extracted. The lignin-removed raw material was added to a NaOH solution with a concentration of 0.1 g / mL. The mixture was heated in an oil bath magnetic stirrer at a temperature of 60°C for 4 h. The mixture was freeze-dried for 30 h.

[0051] Oleic acid 7.128 g, anhydrous ethanol 9 mL, sodium hydroxide solution with a concentration of 0.05 g / mL, calcium chloride solution with a concentration of 0.0176 g / mL, anhydrous sodium dihydrogen phosphate with a concentration of 0.023 g / mL, 10 mL was added in turn. The temperature of the vertical air drying oven was 180°C, and the reaction time was 24 h. The cellulose nanofiber and hydroxyapatite nanowire were dissolved in a KOH solution with a concentration of 0.6 g / mL (25 mL), stirred for 20 h, and then 2 mL of epichlorohydrin was added. After 0.1 g of cuttlefish powder was added, the mixture was frozen for 7 h and freeze-dried for 30 h. A multifunctional all-biomass aerogel with light-to-heat conversion capability was obtained. As shown in FIG. 1, the water evaporation amount of the hydrogel reached 1.92 kg m Figure 2 -2 .

[0052] Example 3

[0053]

[0054]

[0055] The cellulose raw material was dried in an oven at a temperature of 100°C for 24 h. The cellulose raw material had a mass of 30 g. The dried cellulose raw material was added to a sodium chlorite solution with a concentration of 3.0 g / mL and 2 mL of propionic acid. The mixture was heated in an oil bath magnetic stirrer at a temperature of 60°C for 12 h. After the lignin was removed, the cellulose was extracted. The lignin-removed raw material was added to a NaOH solution with a concentration of 3.0 g / mL. The mixture was heated in an oil bath magnetic stirrer at a temperature of 60°C for 4 h. The mixture was freeze-dried for 48 h.

[0056] ​Oleic acid 7.128 g, anhydrous ethanol 9 mL, sodium hydroxide solution concentration 0.05 g / mL, calcium chloride solution concentration 0.0176 g / mL, anhydrous sodium dihydrogen phosphate concentration 0.023 g / mL, respectively, 10 mL was added in turn, the temperature of the vertical air drying oven was 180℃, and the reaction time was 24 h. The cellulose nanofiber and hydroxyapatite nanowire were dissolved in a NaOH solution (25 mL) with a solution concentration of 0.5 g / mL, stirred for 18 h, 2 mL of epichlorohydrin was added, then 0.1 g of cuttlefish powder was added, frozen for 3 h, and freeze-dried for 40 h, to obtain a multifunctional full-biomass aerogel with light-heat conversion capability. As shown in FIGS. 3(a) and 3(b), when compressed to a deformation of 80% under water, the maximum pressure reached 15.2 kPa, and after 5000 cycles of compression, there was almost no plastic deformation.

[0057] Example 4

[0058]

[0059]

[0060] The cellulose raw material was dried in an oven, the temperature of the oven was 60℃, and the drying time was 36 h. The mass of the cellulose raw material was 30 g, the dried cellulose raw material was added to a sodium chlorite solution with a concentration of 0.5 g / mL and 2 mL of acetic acid, the temperature of the heating oil bath magnetic stirrer was 150℃, and the holding time was 4 h. After removing the lignin, the cellulose was extracted, and the lignin-removed raw material was added to a NaOH solution with a concentration of 0.005 g / mL. The temperature of the heating oil bath magnetic stirrer was 60℃, and the holding time was 4 h. The freeze-dried for 30 h.

[0061] Oleic acid 7.128 g, anhydrous ethanol 9 mL, sodium hydroxide solution concentration 0.05 g / mL, calcium chloride solution concentration 0.0176 g / mL, anhydrous sodium dihydrogen phosphate concentration 0.023 g / mL, respectively, 10 mL was added in turn, the temperature of the vertical air drying oven was 180℃, and the reaction time was 18 h. The cellulose nanofiber and hydroxyapatite nanowire were dissolved in a NaOH solution (25 mL) with a solution concentration of 0.06 g / mL, stirred for 24 h, 2 mL of epichlorohydrin was added, then 0.2 g of cuttlefish powder was added, frozen for 8 h, and freeze-dried for 24 h, to obtain a multifunctional full-biomass aerogel with light-heat conversion capability. As shown in FIGS. 4(a) and 4(b), the ultraviolet spectrophotometer diagram and the physical diagram of the organic dye solution (methylene blue and rhodamine B) and the condensed water after evaporation proved that the pollution of organic dyes could be removed. Figure 4

[0062] Example 5

[0063] ​

[0064] The cellulose raw material was dried in an oven at 80℃ for 36 hours. 30g of the dried cellulose raw material was added to a 0.5g / mL sodium chlorite solution and 2mL acetic acid. The mixture was then heated in an oil bath with a magnetic stirrer at 100℃ for 6 hours to remove lignin. Subsequently, cellulose extraction was performed. The lignin-free raw material was added to a 0.05g / mL KOH solution and heated in an oil bath with a magnetic stirrer at 60℃ for 4 hours. The mixture was then freeze-dried for 36 hours.

[0065] Oleic acid 7.128 g, anhydrous ethanol 9 mL, sodium hydroxide solution 0.05 g / mL, calcium chloride solution 0.0176 g / mL, and anhydrous sodium dihydrogen phosphate 0.023 g / mL were added dropwise in 10 mL increments respectively. The reaction was carried out in a vertical drying oven at 180℃ for 24 h. Cellulose nanofibers and hydroxyapatite nanowires were dissolved in 25 mL of NaOH solution with a concentration of 0.032 g / mL and stirred for 20 h. Then, 2 mL of epichlorohydrin was added, followed by 0.3 g of cuttlefish powder. The mixture was then frozen for 5 h and freeze-dried for 36 h to obtain a multifunctional biomass aerogel with photothermal conversion capabilities. Figure 5 As shown, it has a good separation effect on oil-water mixtures.

[0066] Example 6

[0067]

[0068]

[0069] like Figure 7 As shown, the cellulose raw material was placed in an oven and dried at 80℃ for 24 hours. The cellulose raw material weighed 30g. The dried cellulose raw material was added to a 0.1g / mL sodium chlorite solution and 2mL acetic acid. The mixture was kept at 150℃ for 8 hours using a heated oil bath with a magnetic stirrer to remove lignin. Subsequently, cellulose extraction was performed. The lignin-free raw material was added to a 0.08g / mL NaOH solution and kept at 60℃ for 4 hours using a heated oil bath with a magnetic stirrer. The mixture was then freeze-dried for 24 hours.

[0070] Oleic acid 7.128 g, anhydrous ethanol 9 mL, sodium hydroxide solution concentration 0.05 g / mL, calcium chloride solution concentration 0.0176 g / mL, and anhydrous sodium dihydrogen phosphate concentration 0.023 g / mL were added dropwise in 10 mL increments respectively. The reaction was carried out in a vertical drying oven at 180℃ for 24 h. Cellulose nanofibers and hydroxyapatite nanowires were dissolved in 25 mL of NaOH solution with a concentration of 1.44 g / mL and stirred for 20 h. Then, 2 mL of epichlorohydrin was added, followed by 0.3 g of cuttlefish powder. The mixture was then frozen for 2 h and freeze-dried for 48 h to obtain a multifunctional biomass aerogel with photothermal conversion capabilities. Figure 6 and Figure 8 As shown, the aerogel has a self-cleaning function. When 1g of NaCl solid is placed on its surface, it completely disappears within 50 minutes, indicating that it can achieve a self-cleaning function when there is salt contamination on its surface.

Claims

1. A method for preparing multifunctional all-biomass aerogels with photothermal conversion capability, characterized by: Cellulose nanofiber and hydroxyapatite nanowire are dissolved in an alkaline solution to form a uniform slurry, then inkfish powder and a crosslinking agent are added and stirred uniformly, and then the mixture is placed in a refrigerator for freezing, and then freeze-dried to obtain a multifunctional biomass aerogel with light-to-heat conversion capability. The mass ratio of cellulose nanofiber, hydroxyapatite nanowire and inkfish powder is (3-4):(1-2):(1-3), and the mass ratio of alkaline solution to cellulose nanofiber is (90-2):

1.

2. The method for preparing multifunctional all-biomass aerogels with photothermal conversion capability according to claim 1, characterized in that: The alkaline solution is sodium hydroxide and / or potassium hydroxide.

3. The method for preparing multifunctional all-biomass aerogels with photothermal conversion capability according to claim 1, characterized in that: The crosslinking agent is epichlorohydrin and / or glutaraldehyde.

4. The method for preparing multifunctional all-biomass aerogels with photothermal conversion capability according to claim 1, characterized in that: The freezing time is 2-10h, and the freeze-drying time is 24-48h.

5. The method for preparing multifunctional all-biomass aerogels with photothermal conversion capability according to claim 1, characterized in that: The stirring time of the cellulose nanofiber and hydroxyapatite nanowire solution is 18-24h.

6. The method for preparing the multifunctional all-biomass aerogel with photothermal conversion capability according to claim 1, characterized in that... The cellulose nanofiber is prepared by the following method: The cellulose-containing raw material is dried, lignin is removed and extracted with an inorganic solution in a heated oil bath magnetic stirrer, then dried, and then crushed with a crusher to obtain cellulose nanofiber.

7. The method for preparing the multifunctional all-biomass aerogel with photothermal conversion capability according to claim 6, characterized in that: The cellulose-containing raw material is crop straw, flax, cotton, industrial hemp and wood; the raw material is placed in a vertical air drying oven, the temperature of the oven is 60-100℃, and the drying time is 24-48h.

8. The method according to claim 6, wherein the method is characterized by: The inorganic solution for removing lignin is a mixture of sodium chlorite and acetic acid or a mixture of sodium chlorite and propionic acid; the concentration of the inorganic solution for removing lignin is 0.005-3.0g / mL, and the mass ratio of the inorganic solution for removing lignin to the dried cellulose-containing raw material is (50-300):

1. The solution for extracting cellulose nanofiber is one or more of sodium hydroxide and potassium hydroxide; the concentration of the solution for extracting cellulose nanofiber is 0.005-3.0g / mL, and the mass ratio of the solution for extracting cellulose nanofiber to the extracted cellulose is (50-300):

1.

9. The method according to claim 6, wherein the method is characterized by: The temperature of the heated oil bath magnetic stirrer is 50-200℃, and the holding time is 4-20h.

10. The method for preparing the multifunctional all-biomass aerogel with photothermal conversion capability according to claim 1, characterized in that... The hydroxyapatite nanowire is prepared by the following method: 10mL of 0.05g / mL sodium hydroxide solution, 10mL of 0.0176g / mL calcium chloride solution and 10mL of 0.023g / mL anhydrous sodium dihydrogen phosphate solution are added dropwise into 7.128g of oleic acid and 9mL of anhydrous ethanol, stirred, hydrothermally reacted for 12-24h, and then dried in a vertical air drying oven at 180℃ for 24h to obtain hydroxyapatite nanowire.

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