Composite material comprising a fibrous reinforcement and a poly(phospho-sialate) geopolymer matrix and associated manufacturing method

Abstract

A composite material containing a matrix and a fibrous reinforcement, in particular a textile embedded in the matrix. The matrix includes a geopolymer of the poly(phospho-sialate) type having the following formula I: (1) (—P—O—Si—O—Al—O—).sub.n in which n is greater than 2. The matrix further includes zirconium covalently bonded to the matrix, especially in the —ZrO form and/or in the —O—Zr—O form. The matrix has a melting temperature greater than 700° C., especially equal to or greater than 1200° C.

Claims

1. A composite material containing a matrix and a fibrous reinforcement, said matrix comprising a geopolymer of a poly(phospho-sialate) having a following empirical formula:
wSiO.sub.2:Al.sub.2O.sub.3:xP.sub.2O.sub.5:yZrO.sub.2 with 1.00≤w≤3.00, 0.20≤x≤2.00 and 0.02≤y≤0.03; and wherein said geopolymer matrix has a melting temperature greater than 700° C.

2. The composite material of claim 1, wherein the fibrous reinforcement is a textile embedded in said geopolymer matrix.

3. The composite material of claim 1, wherein the melting temperature is equal to or greater than 1200° C.

4. The composite material of claim 1, wherein said geopolymer matrix comprises a nanocomposite comprising three phases: a) a first polymeric phase comprising an acidic poly(phospho-sialate) geopolymer of formula (—P—O—Si—O—Al—O—).sub.n in which n is greater than 2 and a micronized filler of Al.sub.2O.sub.3; b) a second nodular phase consisting of nano spheres of amorphous SiO.sub.2 silica having a diameter of less than 2 microns; and c) a third phase comprising units of formula —Si—O—(P—O—Zr—O—P—O)—Al—O—[[Si—O—(P—O—Zr—O—P—O)—AI—O—]] and units of formula —P—O—Si—O—Al—O—)[[—Si—O—(P—O—Si—O—AI—)]] and serving as a cross-linking site between said first polymeric phase and said second nodular phase.

5. The composite material of claim 4, wherein the diameter of said amorphous SiO.sub.2 silica is less than 500 nm.

6. The composite material of claim 1, wherein said geopolymer further comprises at least one of a berlinite poly(alumino-phosphate) (Al-O—P—O—)[[ (AI-O—P—O—)]] geopolymer of empirical formula Al[[I]] PO.sub.4 [[AIPO.sub.4]] and a cristobalite poly(alumino-phosphate) (Al-O—P—O—)[[ (AI-O—P—O—)]] geopolymer of empirical formula AlPO.sub.4 [[AIPO.sub.4]].

7. The composite material of claim 4, wherein said geopolymer matrix further comprises zirconium phosphate (P—O—Zr—O—P—O)— in said first polymeric phase.

8. The composite material of claim 4, wherein a molar fraction (z/a number of moles of SiO.sub.2 in said geopolymer matrix) is greater than or equal to 0.025 and less than or equal to 0.3, z being a number of moles of zirconium phosphates present in said third phase.

9. The composite material of claim 8, wherein the molar fraction (z/the number of moles of SiO.sub.2 in said geopolymer matrix) is equal to y.

10. The composite material of claim 4, wherein a molar fraction (z / the number of moles of SiO.sub.2 in said geopolymer matrix) is less than 0.025, z being a number of moles of zirconium phosphates present in said third phase; and wherein said third phase contains more units of the formula —Si—O—(P—O—Si—O—P—O)—Al-O— than units of the formula —Si—O—(P—O—Zr—O—P—O)—Al-O—[[—Si—O—(P—O—Zr—O—P—O)—AI—O—]].

11. The composite material of claim 1, wherein said fibrous reinforcement is a textile comprising fibers selected among aluminosilicate fibers, alumina fibers, glass fibers, silica fibers, silicon carbide fibers, carbon fibers, graphite fibers and mixtures of at least two of the fibers.

12. The composite material of claim 4, wherein the diameter of the nano spheres of amorphous SiO.sub.2 silica is less than 500 nm.

13. A method of manufacturing a fiber-reinforced composite material of claim 1, comprising: preparing a resin by mixing, at a temperature substantially equal to 20° C., phosphoric acid H.sub.3PO.sub.4, alumina hydroxide Al(OH).sub.3, amorphous nodular silica SiO.sub.2 comprising on its surface zirconium oxide and water H.sub.2O, in a following molar ratios: P.sub.2O.sub.5/SiO.sub.2 greater than or equal to 0.20 and less than or equal to 0.66; SiO.sub.2/Al.sub.2O.sub.3 greater than or equal to 1.0 and less than or equal to 3.0; P.sub.2O.sub.5/Al.sub.2O.sub.3 greater than or equal to 0.20 and less than or equal to 2.0; and leaving an obtained mixture to stand for 1 to 2 hours; impregnating a textile with the resin, the textile comprising fibers selected among aluminosilicate fibers, alumina fibers, glass fibers, silica fibers, silicon carbide fibers, carbon fibers, graphite fibers and mixtures of at least two of the fibers; preparing a composite material by curing the textile impregnated with the resin at a temperature above 80° C. in an autoclave and under vacuum; and post-curing the composite material at a temperature greater than or equal to 100° C.

14. The manufacturing method of claim 13, wherein said zirconium oxide is in a form of at least one of —ZrO— and —Zr—OH.

15. The manufacturing method of claim 13, wherein the textile impregnated with the resin is cured at a temperature above 118° C. and below 260° C.

16. The manufacturing method of claim 13, wherein the amorphous nodular silica SiO.sub.2 has on its surface 2% to 10% by mole of zirconium in a form of at least one of —Zr—O— and —Zr—OH.

Description

DETAILED DESCRIPTION OF THE EMBODIMENTS

(1) The present invention, its characteristics and the various advantages that it provides will become clearer upon reading the following description, which refers to the following examples, which are provided for illustration and without any limitation.

EXAMPLES

Comparative Example 1

(2) Comparison of a Composite According to the Invention with a Composite as Described in Example 1 of Document WO 96/28398 and a Composite Obtained by the Sintering Technique Described in the Publication of Xue-Jin Yang et al. In 2015

(3) A composite material is prepared according to the invention comprising a carbon fiber fabric and a matrix as indicated in Example 4 below. Another composite material is prepared in accordance with Example 1 of WO 96/28398 and another material is prepared as described in the 2015 publication of Xue-Jin Yang et al. One compares the behavior of these two composites as follows. The composites are heated to 600° C. for a period of 1 to 6 hours. The residual mass of the fibers is then calculated from the loss of the weight of the matrices alone as a function of time. The results are summarized in Table 1.

(4) TABLE-US-00001 TABLE I Time in WO Present Xue-Jin hours 96/28398 invention Yang 0  0% 0%  0% 1  9% 3% 1-3% 3 25% 4% — 6 34% 6% —

(5) It can be seen from the results in Table 1 that the acidic poly(phospho-sialate) matrix (—P—O—Si—O—Al—O—).sub.n, prepared according to the present invention, greatly limits the oxidation of carbon fibers, compared to a poly(sialate) alkaline matrix.

Comparative Example 2: Preparation of a Poly(Phospho-Siloxonate) Matrix

(6) A resin is therefore prepared to produce a geopolymer by mixing silica fume and an aqueous solution of phosphoric acid H.sub.3PO.sub.4 at 75% (mass concentration). The resin is poured into a mold and then cured at 250° C. The thermal evolution of this poly(phospho-siloxonate) is then monitored with a scanning electron microscope (SEM) after curing at 250° C., 700° C. and 1000° C. The results are presented in Table II below.

(7) TABLE-US-00002 TABLE 2 250° C. 700° C. 1000° C. Strong presence the SiO.sub.2 the matrix is of SiO.sub.2 nanospheres, molten; it is nanospheres of dimensions a glass; zero of all >2 microns have nanosphere dimensions. disappeared of SiO.sub.2
It is noted that the geopolymerization reaction takes place between 250° C. and 700° C., but that the poly(phospho-siloxonate) (—Si—O—P—O—Si—).sub.n geopolymer softens and melts at a temperature below 1000° C. In fact, if one refers to the phase diagrams, one notices that in the SiO.sub.2—P.sub.2O.sub.5 system, there exists an eutectic at 980° C. corresponding to the empirical chemical formula 2SiO.sub.2.P.sub.2O.sub.5 (see Phase Diagrams For Ceramists, FIG. 364, American Ceramic Society, 1964). It cannot therefore be used as a matrix for thermostable thermostructural composite materials, such as those developed in the present invention, because of its relatively low softening temperature.

Comparative Example 3: Fiber Composite Comprising a Matrix Consisting of Poly(Alumino-Phosphate) (—AI—O—P—O—).SUB.n

(8) An alumina hydrate Al(OH).sub.3 with a particle size of less than 10 microns is selected and reacted with a 75% aqueous solution of phosphoric acid H.sub.3PO.sub.4 (mass concentration). Then a textile is impregnated with the resin thus obtained. The fabric is made of alumina fibers (Nextel fibers from the company 3M). The whole is cured in an autoclave using well-known technologies applied to organic matrix composites or alkaline geopolymer composites. The prior art teaches us that the geopolymerization temperature of poly(alumino-phosphate) AIPO.sub.4 is above 118° C., and the examples described in the above-mentioned textbook indicate temperatures of 113° C., 123° C. and 133° C. Then a 700° C. heat post-treatment is carried out. This produces a solid composite material. Next, samples are cut in the fiber direction of the textile in order to carry out mechanical tests. These samples are used to determine the 3-point bending strength at room temperature and also at 800° C., according to ASTM C1341-06, and tensile strength, according to ASTM C1275. The results are presented in Table 3.

(9) TABLE-US-00003 TABLE III Ambient at Temperature 800° C. 3-point bending 118 106 strength (MPa) Tensile strength (MPa) 109 82
From the results in Table IIl, it can be seen that the values are lower than those of prior art composite materials obtained with an alkaline poly(sialate) matrix, which are in the range of 200 MPa to 350 MPa at room temperature. These values are also much lower than those required by the industry for this type of thermostructural composite.

(10) Throughout the application, oxide ratios are mole ratios, and indicated parts are by weight.

EXAMPLES OF IMPLEMENTATION OF THE PRESENT INVENTION

Example 1

(11) A matrix for composite materials, labeled Nr51, is prepared using a reaction mixture containing: H.sub.2O: 5.30 moles; P.sub.2O.sub.5: 0.56 moles; SiO.sub.2 doped with zirconium oxide: 1.78 moles; Al.sub.2O.sub.3: 1 mole.

(12) Al.sub.2O.sub.3 comes from an aluminum hydroxide Al(OH).sub.3 powder; SiO.sub.2 comes from amorphous nodular silica prepared by electrofusion and doped with 2% by weight of ZrO.sub.2, P.sub.2O.sub.5 comes from an aqueous solution of phosphoric acid at 75% mass concentration. The molar ratio of the reactive oxides is equal to:

(13) TABLE-US-00004 P.sub.2O.sub.5/SiO.sub.2 0.31 SiO.sub.2/Al.sub.2O.sub.3 1.78 P.sub.2O.sub.5/Al.sub.2O.sub.3 0.56

(14) The mixture is left to mature for 1 to 2 hours, then cured at 120° C. in a closed mold and removed from the mold and dried at 250° C. for 3 hours. The sample is then heat-treated in an air oven at 700° C. for 3 hours.

(15) Usually, to determine the mineralogical nature and composition of a ceramic-type material, the worker in the field uses X-ray diffraction analysis. The applicant has made a number of X-ray diffraction diagrams on the matrices described in the examples of the present invention. Unfortunately, they are useless. Actually, for the ternary system SiO.sub.2/P.sub.2O.sub.5/Al.sub.2O.sub.3, which is the case of the present invention, it is impossible to differentiate between a quartz type silica from an alumina phosphate of berlinite type, a trydimite type silica from a trydimite type alumina phosphate, a cristobalite type silica from a cristobalite type alumina phosphate. Indeed, it is well known by the workers in the field that these various types of silica have the same molecular structure, an isostructural phenomenon, as the various types of alumina phosphate. They exactly have the same X-ray diffraction pattern. To overcome this difficulty, the applicant chose the scanning electron microscopy SEM, ×3000 magnification, coupled with EDS analysis. The results are presented in Table 4 below with EDS analysis carried out on 3 points.

(16) Point “A” is pointed on a nodular silica with a size of 3 microns, point “B” in an amorphous zone which contains a handful of silica spheres with a diameter of 500 nm to 1 micron, point “C” in an amorphous zone with no visible sphere at this stage of the SEM magnification.

(17) Table IV: SEM EDS analysis, atomic composition percent in the nano-composite, sample Nr51.

(18) TABLE-US-00005 TABLE IV Elements Point A Point B Point C Al 10.48 44.92 52.25 Si 76.46 27.25 19.10 P 9.11 26.81 28.02 Zr 3.95 1.48 0.23

(19) Point “A” shows the nodular silica sphere covered by the zircono-phosphate cross-linking phase —Si—O—(P—O—Zr—O—P—O)—Al-O—. Point “B” corresponds to the first polymeric phase which after computation contains approximately: 1 mole of zircono-phosphate (P—O—Zr—O—P—O)—, 25 moles of poly(phospho-sialate) (—P—O—Si—O—Al—O—), 9 moles of unreacted Al.sub.2O.sub.3 and 1 mole of silica SiO.sub.2 (small spheres of 500 nm). For point “C” the breakdown is as follows: 19 moles of poly(phospho-sialate) (—P—O—Si—O—Al—O—), 12 moles of Al.sub.2O.sub.3 and 9 moles of AlPO.sub.4 poly(alumino-phosphate) (Al-O—P—O—).

Example 2

(20) A new acidic geopolymer matrix (Nr50) is prepared as in Example 1, but with a reaction mixture containing: H.sub.2O: 3.50 moles; P.sub.2O.sub.5: 0.37 moles; SiO.sub.2: 1.18 moles; Al.sub.2O.sub.3: 1 mole; Al.sub.2O.sub.3 comes from an alumina hydroxide Al(OH).sub.3 powder; SiO.sub.2 comes from amorphous nodular silica prepared by electrofusion and doped with 2% by weight of ZrO.sub.2; P.sub.2O.sub.5 comes from a solution of phosphoric acid at 75% concentration in water. The molar ratio of the reactive oxides is equal to:

(21) TABLE-US-00006 P.sub.2O.sub.5/SiO.sub.2 0.31 SiO.sub.2/Al.sub.2O.sub.3 1.18 P.sub.2O.sub.5/Al.sub.2O.sub.3 0.37

(22) The results of the EDS-SEM analysis are listed in Table 5 below with EDS analysis conducted on 3 points: point “A” is pointed on a nodular silica with a 2-micron size, point “B” corresponds to an amorphous zone which contains a handful of silica spheres with a diameter of 500 nm to 1 micron, point “C” is an amorphous zone with a handful of spheres visible at this stage of SEM magnification.

(23) Table V: SEM EDS analysis, atomic composition percent in the nano-composite, sample Nr50.

(24) TABLE-US-00007 TABLE V Elements Point A Point B Point C Al 15.02 49.25 45.26 Si 69.16 31.73 36.40 P 11.09 18.79 18.05 Zr 4.31 0 0

(25) In sample Nr50, point “A” shows the nodular silica sphere covered by the zircono-phosphate cross-linking phase —Si—O—(P—O—Zr—O—P—O)—Al-O—. Point “B” corresponds to the first polymeric phase which after computation contains approximately: 18 moles of poly(phospho-sialate) (—P—O—Si—O—Al—O—), 13 moles of silica SiO.sub.2 (silica nano-spheres) and 9 moles of unreacted Al.sub.2O.sub.3. For point “C” the breakdown is as follows: 18 moles of poly(phospho-sialate) (—P—O—Si—O—Al—O—)+18 moles SiO.sub.2+5.5 moles of Al.sub.2O.sub.3.

(26) In these two matrices Nr51 and Nr50, the first polymeric phase of the nano-composite constituting the geopolymer matrix essentially comprises poly(phospho-sialate) (—P—O—Si—O—Al—O—), 18 to 25 moles, with 5 to 12 moles of a micronized Al.sub.2O.sub.3 filler, and 0 to 9 moles of poly(alumino-phosphate) (Al-O—P—O—), AlPO.sub.4. It should be noted that poly(alumino-phosphate) (Al-O—P—O—), AlPO.sub.4, is not the main component of the polymeric phase of this acidic geopolymer, the predominant component is poly(phospho-sialate) (—P— O—Si—O—Al—O—).

Example 3

(27) A new acidic geopolymer matrix (Nr13) is manufactured as in Examples 1 and 2, but with a reaction mixture containing: H.sub.2O: 3.50 moles; P.sub.2O.sub.5: 0.37 moles; SiO.sub.2: 2.02 moles; Al.sub.2O.sub.3: 1 mole.

(28) Al.sub.2O.sub.3 comes from an alumina hydroxide Al(OH).sub.3 powder); SiO.sub.2 comes from amorphous nodular silica prepared by electrofusion and doped with 4% by weight of ZrO.sub.2, P.sub.2O.sub.5 comes from a solution of phosphoric acid at 75% concentration in water. The molar ratio of the reactive oxides is equal to:

(29) TABLE-US-00008 P.sub.2O.sub.5/SiO.sub.2 0.18 SiO.sub.2/Al.sub.2O.sub.3 2.028 P.sub.2O.sub.5/Al.sub.2O.sub.3 0.37

(30) This Nr13 matrix is used for the making of a fiber-reinforced composite material. The above-mentioned reaction mixture is used to impregnate a satin-type fabric made of fibers containing more than 99% by mass of alumina (Nextel® Fabric 610 marketed by the company 3M). Six pieces of the obtained impregnated fabric are superimposed on a flat support, alternating the warp and weft directions of the fabric. The laminated composite thus obtained and its support is placed in a vacuum bag. Once the vacuum is created (pressure less than or equal to 100 mbar in absolute), the whole unit is placed in an autoclave under a pressure of 6 bars, at 150° C. (first cure). After having left the unit for 6 hours in the above-mentioned vacuum and temperature conditions, the composite is removed from the mold and subjected to a 3-hour postcuring at 700° C. Then, samples are cut in the direction of the fibers of the textile in order to perform mechanical tests. The results of these tests are summarized in Table 6 below.

(31) These samples are used to determine the 3-point bending strength at room temperature and 800° C., according to ASTM C1341-06 and the tensile strength, according to ASTM C1275. The results obtained for the composite specimens of Example 3 are listed in Table 6 below.

(32) TABLE-US-00009 TABLE VI Ambient at Temperature 800° C. 3-point bending 339 255 strength (MPa) Tensile strength (MPa) 214 170

Example 4

(33) Composite plate samples are prepared as in Example 3. They are exposed to a temperature of 1000° C. or 1200° C. for 100 hours. The samples are then allowed to return to room temperature before measuring their flexural strength. The mass loss is also measured to determine whether the fibers have been degraded. The results are summarized in Table 7 below.

(34) Table VII: Thermal ageing results for the composite material from example 4; flexural strength (MPa), modulus GPa and residual mass in %.

(35) TABLE-US-00010 TABLE VII number Flexural of strength Modulus Residual samples (MPa) (GPa) mass Initial state 3 356 73 100 After thermal 3 317 71 99.7 aging 100 hours at 1000° C. After thermal 3 166 80 98.8 aging 100 hours at 1200° C.

(36) It can be seen from the results in Table 7 that the flexural strength decreases only moderately (10.9% from the initial state) with ageing at 1000° C. If we refer to Table 2, which shows the melting of the poly(phospho-siloxonate) geopolymer (—Si—O—P—O—Si).sub.n between 900° C. and 1000° C., we can see that the zirconium oxide (ZrO—ZrO.sub.2) doping has fulfilled its function since the strength is practically unchanged at 1000° C. This strength decreases with aging at 1200° C., but remains sufficiently high, much higher than the composite materials of the prior art, such as the one described above in Table 3. The modulus remains almost constant. The composite has lost less than 2% of mass whatever the temperature of ageing.

(37) Any worker in the field will easily understand the benefits to be gained from the manufacturing method of fiber-reinforced composite materials based on an acidic poly(phospho-sialate) geopolymer matrix, more specifically when comparing the thermal properties of materials containing Nextel type alumina fiber. He will also note the benefits of the present invention for carbon-based Cf/SiC composites. In fact, it can be seen from the results in Table 1 that the acidic poly(phospho-sialate) matrix (—P—O—Si—O—Al—O—).sub.n, according to the present invention, significantly minimizes the oxidation of carbon fibers, compared to an alkaline poly(sialate) matrix. The economic benefits of the method according to the invention are therefore obvious. Of course, this geopolymer matrix can also be used with all the other fibrous reinforcements known by the worker in the field as well as with many other reinforcements that allow the manufacture of composite materials. One can mention for example mica flakes and similar particulates designed to fabricate materials stable at high temperatures.

(38) The worker in the field may also add to the reaction mixtures any extra mineral or organic material known for its capacity to increase the impregnation and/or reduce the amount of air trapped in the matrix. Various modifications may thus be introduced by the worker in the field to the acid geopolymeric matrix and to the method which has just been described simply as an example, whilst staying within the terms of the invention.