Cellulose nanocrystal-modified ceramic blank and preparation method thereof

Abstract

A cellulose nanocrystal-modified ceramic blank and a preparation method thereof are disclosed. Cellulose nanocrystals are added into a ceramic blank in gelcasting. The cellulose nanocrystal-modified ceramic blank comprises, by weight, 0.1 to 10 parts of cellulose nanocrystals, 0.1 to 30 parts of organic gel and 70 to 99 parts of ceramic powder. The cellulose nanocrystal has length of 100 to 300 nm, a diameter of 10 to 20 nm, a slenderness ratio of 10 to 15 , and an elastic modulus of 100 to 150 GPa. The drying strength of the ceramic blank with the cellulose nanocrystals is obviously improved.

Claims

1. A method of preparing a ceramic blank, comprising: (1) preparing a cellulose nanocrystal-water suspension wherein a mass percentage of cellulose nanocrystals in the cellulose nanocrystal-water suspension is 0.01-15 wt %, and a preparation method of the cellulose nanocrystal-water suspension comprises subjecting cotton linter to alkali treatment, sulfuric acid hydrolysis, centrifugal cleaning, and dialysis, wherein the cellulose nanocrystal has a length of 100-300 nm, a diameter of 10-20 nm, a slenderness ratio of 10-15, and an elastic modulus of 100-150 GPa; adding a monomer, a cross-linking agent, and a dispersant to the suspension in sequence and mixing them uniformly; and adjusting a pH value of the suspension with aqueous ammonia to 8-11 to obtain a premixed solution; (2) adding a ceramic powder to the premixed solution; and adding grinding balls therein to obtain a slurry after ball grinding treatment; (3) adding an initiator to the slurry; stirring the slurry uniformly; removing bubbles therefrom; pouring the slurry into a mold; and heating and curing the slurry at a temperature of 30-80 C. for 20-90 min to obtain a semi-product; and (4) taking the semi-product out of the mold; and machining and drying the semi-product to obtain a cellulose nanocrystal-modified ceramic blank.

2. The method of claim 1, wherein the ceramic powder is added to the premixed solution in a solid-liquid volume ratio of 1:0.3 to 1:2.4 in step (2).

3. The method of claim 1, wherein the monomer is acrylamide, N,N-dimethylacrylamide, N-hydroxymethacrylamide, or macromolecular chitosan; the cross-linking agent is N,N-methylene bisacrylamide; and the dispersant is a polyacrylic compound.

4. The method of claim 1, wherein the ball grinding treatment is performed for 30-120 minutes at a rotation speed of 200-600 rpm, and a mass ratio of the grinding balls to the ceramic powder is 1:1 to 3:1.

5. The method of claim 1, wherein the semi-product is first dried at a temperature of 20-80 C. for 10-24 hours, and then dried at a temperature of 80-120 C. for 12-48 hours.

6. A method of preparing a ceramic blank, comprising: (1) preparing a cellulose nanocrystal-water suspension, wherein a preparation method of the cellulose nanocrystal-water suspension comprises subjecting cotton linter to alkali treatment, sulfuric acid hydrolysis, centrifugal cleaning, and dialysis, wherein the cellulose nanocrystal has a length of 100-300 nm, a diameter of 10-20 nm, a slenderness ratio of 10-15, and an elastic modulus of 100-150 GPa; adding a monomer, a cross-linking agent, and a dispersant to the suspension in sequence and mixing them unifonnly; and adjusting a pH value of the suspension with aqueous ammonia to 8-11 to obtain a premixed solution; (2) adding a ceramic powder to the premixed solution; and adding grinding balls therein to obtain a slurry after ball grinding treatment; (3) adding an initiator to the slurry; stirring the slurry unifonnly; removing bubbles therefrom; pouring the slurry into a mold; and heating and curing the slurry at a temperature of 30-80 C. for 20-90 min to obtain a semi-product; and (4) taking the semi-product out of the mold; and machining and drying the semi-product to obtain a cellulose nanocrystal-modified ceramic blank, wherein the cellulose nanocrystal-modified ceramic blank comprises: 0.1-10 parts by weight of cellulose nanocrystals; 0.1-30 parts by weight of acrylamide compound; and 70-99 parts by weight of ceramic powder.

7. The method of claim 6, wherein the ceramic powder is added to the premixed solution in a solid-liquid volume ratio of 1:0.3 to 1:2.4 in step (2).

8. The method of claim 6, wherein the monomer is acrylamide, N,N-dimethylacrylamide, N-hydroxymethacrylamide, or macromolecular chitosan; the cross-linking agent is N,N-methylene bisacrylamide; and the dispersant is a polyacrylic compound.

9. The method of claim 6, wherein the ball grinding treatment is performed for 30-120 minutes at a rotation speed of 200-600 rpm, and a mass ratio of the grinding balls to the ceramic powder is 1:1 to 3:1.

10. The method of claim 6, wherein the semi-product is first dried at a temperature of 20-80 C. for 10-24 hours, and then dried at a temperature of 80-120 C. for 12-48 hours.

Description

DESCRIPTION OF THE EMBODIMENTS

(1) The technical solutions of the present disclosure will be further illustrated hereinafter with reference to specific embodiments. However, the specific embodiments disclosed herein shall not be considered as a limitation to the scope of the present disclosure.

(2) A cellulose nanocrystal is prepared by the following method.

(3) Cotton linter is treated by alkali to remove impurities, lignin, hemicellulose and other components. Purified cotton linter cellulose proceeds with strong acid hydrolysis by sulfuric acid aqueous solution (with a mass percentage of 65%) to remove an amorphous zone from the cellulose and remain a rigid crystalline zone therein. The hydrolysis time is 1 hour. The cellulose nanocrystal suspension after hydrolysis is centrifugal cleaned for 3 to 5 times by deionized water. After deionized water dialysis, a cellulose nanocrystal suspension is obtained, and cellulose nanocrystal powder is obtained after freezing and drying.

(4) The cellulose nanocrystal prepared therein has a rod-like shape, and has a length of 100 to 300 nm, a diameter of 10 to 20 nm, a slenderness ratio of 10 to 15, and an elastic modulus of 100 to 150 GPa.

Example 1

(5) (1) 3.75 g cellulose nanocrystal suspension (with a mass percentage of 1.5%) is weighed accurately, and N,N-dimethylacrylamide (3.75 g), N,N-methylene bisacrylamide (0.075 g), and ammonium polyacrylate (0.3 g) are added to the suspension in sequence. After stirring for 10 min, a pH value of the suspension is adjusted to 9.3 with aqueous ammonia, and a premixed solution is obtained.

(6) (2) Alumina powder (ball-shaped -Al.sub.2O.sub.3, white powder, d505 m, -Al.sub.2O.sub.3 content >99.8%) and the premixed solution are mixed with a solid-liquid volume ratio being 1:1. Grinding balls are added therein with a mass ratio of grinding balls to ceramic powder being 1.5:1, ball grinding for 30 min with a rotation speed of 500 rpm, and a slurry is obtained.

(7) (3) An initiator ammonium persulfate (0.0375 g) is added to the slurry. The slurry is stirred for 15 min, and bubbles are removed therefrom in vacuum. The slurry is then poured into a mold, and heated and cured at a temperature of 70 C.

(8) (4) After being cured, wet blank is taken out of the mold, machined, dried at a temperature of 40 C. for 12 h, and dried in vacuum at a temperature of 90 C. for 24 h to obtain a ceramic blank with a high strength.

Comparative Example 1

(9) 3.75 g water is weighed accurately to substitute the cellulose nanocrystal suspension in Example 1, and other steps are the same as those in Example 1. Another ceramic blank is prepared.

(10) It is shown that, a bending strength of the dried cellulose nanocrystal-modified ceramic blank in Example 1 is 30.19 MPa, which is increased by 51% compared with the ceramic blank in Comparative example 1. Meanwhile, a three-point bending deformation of the cellulose nanocrystal-modified ceramic blank in Example 1 after dried for 2 hours in a natural environment is 3 mm, which is increased by 71% compared with the ceramic blank in Comparative example 1 under a same condition.

Example 2

(11) (1) 15 g cellulose nanocrystal suspension (with a mass percentage of 1.5%) is weighed accurately, and distilled water (25 g) is added to the suspension to obtain a cellulose nanocrystal-water solution. The solution is stirred for 10 min, and N,N-dimethylacrylamide (7.5 g), N,N-methylene bisacrylamide (0.15 g), and ammonium polyacrylate (0.6 g) are added to the solution in sequence. After stirring for 10 min, a pH value of the suspension is adjusted to 9 with aqueous ammonia, and a premixed solution is obtained.

(12) (2) Alumina powder (ball-shaped -Al.sub.2O.sub.3, white powder, d505 m, -Al.sub.2O.sub.3 content >99.8%) and the premixed solution are mixed with a solid-liquid volume ratio being 1:1. Grinding balls are added therein with a mass ratio of grinding balls to ceramic powder being 1.5:1, ball grinding for 30 min with a rotation speed of 400 rpm, and a slurry is obtained.

(13) (3) An initiator ammonium persulfate (0.075 g) is added to the slurry. The slurry is stirred for 15 min, and bubbles are removed therefrom in vacuum. The slurry is then poured into a mold, and heated and cured at a temperature of 70 C.

(14) (4) After being cured, wet blank is taken out of the mold, machined, dried at a temperature of 40 C. for 12 h, and dried in vacuum at a temperature of 90 C. for 24 h to obtain a ceramic blank with a high strength.

Comparative Example 2

(15) 15 g water is weighed accurately to substitute the cellulose nanocrystal suspension in Example 2, and other steps are the same as those in Example 2. Another ceramic blank is prepared.

(16) It is shown that, a bending strength of the dried cellulose nanocrystal-modified ceramic blank in Example 2 is 30.9 MPa, which is increased by 55% compared with the ceramic blank in Comparative example 2. Meanwhile, a three-point bending deformation of the cellulose nanocrystal-modified ceramic blank in Example 2 after dried for 2 hours in a natural environment is 2.5 mm, which is increased by 43% compared with the ceramic blank in Comparative example 2 under a same condition.

Example 3

(17) (1) 30 g cellulose nanocrystal suspension (with a mass percentage of 1.5%) is weighed accurately, and distilled water (10 g) is added to the suspension to obtain a cellulose nanocrystal-water solution. The solution is stirred for 10 min, and N,N-dimethylacrylamide (7.5 g), N,N-methylene bisacrylamide (0.15 g), and ammonium polyacrylate (0.6 g) are added to the solution in sequence. After stirring for 10 min, a pH value of the suspension is adjusted to 9.2 with aqueous ammonia, and a premixed solution is obtained.

(18) (2) Alumina powder (ball-shaped -Al.sub.2O.sub.3, white powder, d505 m, -Al.sub.2O.sub.3 content >99.8%) and the premixed solution are mixed with a solid-liquid volume ratio being 1:1. Grinding balls are added therein with a mass ratio of grinding balls to ceramic powder being 1.5:1, ball grinding for 30 min with a rotation speed of 400 rpm, and a slurry is obtained.

(19) (3) An initiator ammonium persulfate (0.075 g) is added to the slurry. The slurry is stirred for 15 min, and bubbles are removed therefrom in vacuum. The slurry is then poured into a mold, and heated and cured at a temperature of 70 C.

(20) (4) After being cured, wet blank is taken out of the mold, machined, dried at a temperature of 40 C. for 12 h, and dried in vacuum at a temperature of 90 C. for 24 h to obtain a ceramic blank with a high strength.

Comparative Example 3

(21) Water 30 g is weighed accurately to substitute the cellulose nanocrystal suspension in Example 3, and other steps are the same as those in Example 3. Another ceramic blank is prepared.

(22) It is shown that, a bending strength of the dried cellulose nanocrystal-modified ceramic blank in Example 3 is 24.7 MPa, which is increased by 25% compared with the ceramic blank in Comparative example 3. Meanwhile, a three-point bending deformation of the cellulose nanocrystal-modified ceramic blank in Example 3 after dried for 2 hours in a natural environment is 2.9 mm, which is increased by 66% compared with the ceramic blank in Comparative example 3 under a same condition.

Example 4

(23) (1) 40 g cellulose nanocrystal suspension (with a mass percentage of 1.5%) is weighed accurately, and N,N-dimethylacrylamide (7.5 g), N,N-methylene bisacrylamide (0.15 g), and ammonium polyacrylate (0.6 g) are added to the suspension in sequence.

(24) After stirring for 10 min, a pH value of the suspension is adjusted to 9.4 with aqueous ammonia, and a premixed solution is obtained.

(25) (2) Alumina powder (ball-shaped -Al.sub.2O.sub.3, white powder, d505 m, -Al.sub.2O.sub.3 content >99.8%) and the premixed solution are mixed with a solid-liquid volume ratio being 1:1. Grinding balls are added therein with a mass ratio of grinding balls to ceramic powder being 1.5: 1, ball grinding for 30 min with a rotation speed of 400 rpm, and a slurry is obtained.

(26) (3) An initiator ammonium persulfate (0.075 g) is added to the slurry. The slurry is stirred for 15 min, and bubbles are removed therefrom in vacuum for 10 min.

(27) The slurry is then poured into a mold, and heated and cured at a temperature of 70 C. for 60 min.

(28) (4) After being cured, wet blank is taken out of the mold, machined, dried at a temperature of 40 C. for 12 h, and dried in vacuum at a temperature of 90 C. for 24 h to obtain a ceramic blank with a high strength.

Comparative Example 4

(29) 40 g water is weighed accurately to substitute the cellulose nanocrystal suspension in Example 4, and other steps are the same as those in Example 4. Another ceramic blank is prepared.

(30) It is shown that, a bending strength of the dried cellulose nanocrystal-modified ceramic blank in Example 4 is 27.8 MPa, which is increased by 39% compared with the ceramic blank in Comparative example 4. Meanwhile, a three-point bending deformation of the cellulose nanocrystal-modified ceramic blank in Example 4 after dried for 2 hours in a natural environment is 3.9 mm, which is increased by 124% compared with the ceramic blank in Comparative example 4 under a same condition.

Example 5

(31) (1) 10 g cellulose nanocrystal suspension (with a mass percentage of 2%) is weighed accurately, and distilled water (30 g) is added to the suspension to obtain a cellulose nanocrystal-water solution. The solution is stirred for 10 min, and acrylamide (7.5 g), N,N-methylene bisacrylamide (0.15 g), and ammonium polyacrylate (0.6 g) are added to the solution in sequence. After stirring for 10 min, a pH value of the suspension is adjusted to 9 with aqueous ammonia, and a premixed solution is obtained.

(32) (2) Alumina powder (ball-shaped -Al.sub.2O.sub.3, white powder, d505 m, -Al.sub.2O.sub.3 content >99.8%) and the premixed solution are mixed with a solid-liquid volume ratio being 1:1. Grinding balls are added therein with a mass ratio of grinding balls to ceramic powder being 1.5:1, ball grinding for 30 min with a rotation speed of 400 rpm, and a slurry is obtained.

(33) (3) An initiator ammonium persulfate (0.075 g) is added to the slurry. The slurry is stirred for 15 min, and bubbles are removed therefrom in vacuum. The slurry is then poured into a mold, and heated and cured at a temperature of 70 C.

(34) (4) After being cured, wet blank is taken out of the mold, machined, dried at a temperature of 40 C. for 12 h, and dried in vacuum at a temperature of 90 C. for 24 h to obtain a ceramic blank with a high strength.

Comparative Example 5

(35) 10 g water is weighed accurately to substitute the cellulose nanocrystal suspension in Example 5, and other steps are the same as those in Example 5. Another ceramic blank is prepared.

(36) It is shown that, a drying strength of the ceramic blank prepared by the acrylamide gelcasting system in Comparative example 5 is 46.62 MPa, while a bending strength of the dried cellulose nanocrystal-modified ceramic blank in Example 5 is 58.85 MPa, which is increased by 26.2% compared with the ceramic blank in Comparative example 5. Meanwhile, a three-point bending deformation of the cellulose nanocrystal-modified ceramic blank in Example 5 after dried for 2 hours in a natural environment is 3.1 mm, which is increased by 77% compared with the ceramic blank in Comparative example 5 under a same condition.

(37) According to the present disclosure, the mechanical properties of the cellulose nanocrystal-modified water-based gelcasting ceramic blank can be significantly improved, and the ceramic blank prepared therein is easy to process. The mechanical properties of the ceramic blank in other examples are all better than those in corresponding comparative examples, and they will not be illustrated in detail here.

(38) The technical effect of the present disclosure can be realized by all raw materials, upper limit, lower limit, and values therebetween of the raw materials, as well as upper limit, lower limit, and values therebetween of process parameters, such as the drying temperature, the rotation speed, and so on. The examples are described in an exemplary manner rather than an exhaustive manner.