Multi-phase ceramic system

Abstract

Systems, methods, and other embodiments associated with multi-phase ceramic composites are described herein. Specifically, a multi-phase ceramic composite having a microstructure having at least one solid-state lubricant phase and at least one wear resistant material phase.

Claims

1. A method for making a multi-phase ceramic composite, the method comprising; providing a rare earth metal powder; providing an Al.sub.2O.sub.3 powder; mixing the rare earth metal powder first powder and the Al.sub.2O.sub.3 powder to form a mixed powder; drying the mixed powder; isostatically pressing the mixed powder to form a green component; and sintering the green component to form a sintered component; wherein the sintered component includes continuous networks of two phases, namely, a solid-state lubricant phase comprising gadolinium and a wear resistant phase comprising Al.sub.2O.sub.3, and wherein the two phases are randomly interspersed, wherein a molar ratio of the wear resistant phase to the solid state lubricant phase is between 0.3 and 2.0, wherein an entirety of the sintered component is constructed from constituents of the rare earth metal and Al.sub.2O.sub.3 powders.

2. The method of claim 1, wherein the solid-state lubricant phase comprises Gd.sub.4Al.sub.2O.sub.9 or Gd.sub.2O.sub.3.

3. The method of claim 1, wherein the mixing step is performed by wet milling the Al.sub.2O.sub.3 powder and the rare earth metal powder in ethanol.

4. The method of claim 3, wherein the sintering step is performed at 1450 degrees C. for 4 hours in air.

5. The method of claim 1, wherein the multi-phase ceramic composite comprises the solid-state lubricant phase, the wear resistant phase, and a third phase.

6. The method of claim 1, further comprising using the multi-phase ceramic composite in a joint prosthesis.

7. The method of claim 6, further comprising using the multi-phase ceramic composite on interacting surfaces of an artificial acetabular cup and a femoral head of a hip replacement.

8. The method of claim 1, wherein the molar ratio is less than 1.0.

9. The method of claim 8, wherein the solid state lubricant phase does not include aluminum.

10. A method for making a multi-phase ceramic composite, the method comprising; providing a Gd.sub.2O.sub.3 powder; providing an Al.sub.2O.sub.3 powder; mixing the Gd.sub.2O.sub.3 powder and the Al.sub.2O.sub.3 powder to form a mixed powder; drying the mixed powder; isostatically pressing the mixed powder to form a green component; and sintering the green component to form a sintered component; wherein the sintered component includes continuous networks of two phases, namely, a solid-state lubricant phase comprising Gd.sub.2O.sub.3 and a wear resistant phase comprising Al.sub.2O.sub.3, wherein the two phases are randomly interspersed throughout the multi-phase ceramic composite, wherein a molar ratio of the wear resistant phase to the solid state lubricant phase is between 0.3 and 2.0, wherein an entirety of the sintered component is constructed from constituents of the Gd.sub.2O.sub.3 powder and the Al.sub.2O.sub.3 powder.

11. The method of claim 10, wherein the mixing step is performed by wet milling the Al.sub.2O.sub.3 powder and the Gd.sub.2O.sub.3 powder in ethanol.

12. The method of claim 11, wherein the sintering step is performed at 1450 degrees C. for 4 hours in air.

13. The method of claim 10, wherein the multi-phase ceramic composite comprises the at least one solid-state lubricant phase, the at least one wear resistant phase, and a third phase.

14. The method of claim 10, further comprising using the multi-phase ceramic composite in a joint prosthesis.

15. The method of claim 14, further comprising using the multi-phase ceramic composite on interacting surfaces of an artificial acetabular cup and a femoral head of a hip replacement.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various systems, methods, and other embodiments of the disclosure. Illustrated element boundaries (e.g., boxes, groups of boxes, or other shapes) in the figures represent one example of the boundaries. In some examples one element may be designed as multiple elements or multiple elements may be designed as one element. In some examples, an element shown as an internal component of another element may be implemented as an external component and vice versa.

(2) FIG. 1A illustrates one embodiment of a multi-phase ceramic composite.

(3) FIG. 1B illustrates another embodiment of a multi-phase ceramic composite.

(4) FIG. 2A illustrates a diagram of one embodiment of a multi-phase ceramic composite for use in total hip replacement.

(5) FIG. 2B illustrates an x-ray image of one embodiment of a multi-phase ceramic composite for use in a total hip replacement.

(6) FIG. 3 illustrates one embodiment example of a wear specimen for wear testing associated with multi-phase ceramic composites.

(7) FIG. 4A is a graph illustrating the wear behavior, measured in millimeters of a cobalt chromium alloy over time.

(8) FIG. 4B is a graph illustrating the wear behavior, measured in millimeters of a eutectic solidified Al.sub.2O.sub.3GdAlO.sub.3 composite over time.

(9) FIG. 5 is a graph illustrating the friction coefficient of composite material as a function of the force exerted on the composite compositions containing Gd.sub.2O.sub.3Al.sub.2O.sub.3 and Y.sub.2O.sub.3Al.sub.2O.sub.3.

(10) FIG. 6 is a wear couple summary for different composites subjected to a force of ten Newtons.

(11) FIG. 7A illustrates wear scarring of a CoCr alloy substrate after wear testing.

(12) FIG. 7B illustrates wear scarring of one embodiment of a multi-phase ceramic composite after wear testing.

DETAILED DESCRIPTION

(13) Embodiments or examples illustrated in the drawings are disclosed below using specific language. It will nevertheless be understood that the embodiments or examples are not intended to be limiting. Any alterations and modifications in the disclosed embodiments and any further applications of the principles disclosed in this document are contemplated as would normally occur to one of ordinary skill in the pertinent art. Described herein are examples of systems, methods, and other embodiments associated with multi-phase ceramic composites. The rare earth oxides consists of the 15 lanthanide elements along with Y.sub.2O.sub.3 and Sc.sub.2O.sub.3. They exhibit similar phase formation behavior with Al.sub.2O.sub.3. The composition may be altered using rare earth substitution for Yttrium or Gadolinium.

(14) FIG. 1A illustrates one embodiment of a multi-phase ceramic composite 100.

(15) Specifically, in the embodiment illustrated in the electron micrograph of FIG. 1, the multi-phase ceramic composite 100 is an Al.sub.2O.sub.3GdAlO.sub.3 microstructure. In this embodiment, the Al.sub.2O.sub.3GdAlO.sub.3 microstructure may be fabricated using directional solidification from the melt produced in-situ composite. The Al.sub.2O.sub.3GdAlO.sub.3 microstructure is a dual phase ceramic composite 100 having continuous networks of two phases including a dark phase 110 and a light phase 120. The dark phase 110 is a solid-state lubricant, GdAl.sub.2O. The light phase 120 is a wear resistant material, Al.sub.2O.sub.3. The continuous networks of the dark phase 110 and the light phase 120 may be randomly interspersed. Alternatively, the continuous networks of the dark phase 110 and the light phase 120 may be arranged in a pattern.

(16) FIG. 1B illustrates another embodiment of a multi-phase ceramic composite 130 densified by solid state sintering. Specifically, the embodiment is illustrated as electron micrograph. The multi-phase ceramic composite 130 has a molar ratio of Al.sub.2O.sub.3/Gd.sub.2O.sub.3 of O.6. Powders of Al.sub.2O.sub.3 and Gd.sub.2O.sub.3 were mixed by wet milling in ethanol. Mixed powder was dried, and green rods were fabricated by isostatic pressing the powder. Green rods were reactive sintered at 1450 C. for 4 hours in air.

(17) The Al.sub.2O.sub.3Gd.sub.2O.sub.3 microstructure is a multi-phase ceramic composite 130 with a phase content (wt. %) 30.74% Al.sub.2O.sub.3, 24.1% Gd.sub.2O.sub.3, 26.74% GdAlO.sub.3 and 18.4% Gd.sub.4Al.sub.2O.sub.9. The Al.sub.2O.sub.3GdAlO.sub.3 microstructure 130 is a dual phase ceramic composite 100 having continuous networks of two phases including a dark phase 140 and a light phase 150. The dark phase is Gd.sub.2O.sub.3. The light phase 140 is Al.sub.2O.sub.3. The dark phase 150 is GdAlO.sub.3 and/or Gd.sub.4Al.sub.2O.sub.9. The distribution of the phases are randomly interspersed. Specimens of the multi-phase ceramic composite 100 may be cut from a sintered rod.

(18) Tribological properties of the multi-phase ceramic composite 100 can be measured under a severe environment and compared to tribological properties of commercial CoCr alloy hip prosthesis. The tribological properties of the multi-phase ceramic composite 100 were found to be superior to CoCr alloy. As discussed above, under the severe conditions of non-lubrication, the multi-phase ceramic composite 100 outperformed the CoCr alloy under the same load condition.

(19) While two phases have been described, the multi-phase ceramic composite 100 may include a greater number of phases. Moreover, the materials used to form the composite may be different based on the desired wear properties. For example, as discussed above, other rare earth oxides may exhibit similar phase formation behavior with Al.sub.2O.sub.3. Accordingly, these other rare earth oxides may be used in multi-phase ceramic composites.

(20) A quantitative analysis of the plurality of phases can be conducted using x-ray diffraction. In one embodiment, the x-ray diffraction data is analyzed using the Rietveld method. The method is based on a least-squares fit between step-scan data of a measured diffraction pattern and a simulated X-ray-diffraction (XRD) pattern. The simulated XRD pattern is calculated from based, at least in part, on crystal-structure parameters of each component phase. The simulated XRD pattern may also be calculated based on a scale factor for each constituent phase to adjust the relative intensities of the reflections, parameters describing the peak profile and the background, parameters simulating the instrumental aberrations as well as effects resulting: from size-related strain, preferred orientation, and particle size. The phase abundances of the constituent phases may be directly calculated from the Rietveld model. Therefore, quantitative analysis can be performed without the need of experiments utilizing standard samples for calibration.

(21) The table below shows the phase content of example multi-phase ceramic compositions reactively sintered at 1450 C. for 4 hrs in air.

(22) TABLE-US-00001 Al.sub.2O.sub.3/Gd.sub.2O.sub.3 Al.sub.2O.sub.3 GdAlO.sub.3 Gd.sub.4Al.sub.2O.sub.4 Gd.sub.2O.sub.3 Molar Ratio wt % wt % wt % wt % 3.3 39.04 60.96 0 0 0.6 30.74 26.74 18.40 24.10 0.3 0 21.57 32.76 45.66

(23) FIG. 2A illustrates a diagram of one embodiment of a multi-phase ceramic composite for use in total hip replacement 200. The hip includes the pelvis 210 having an artificial acetabular cup 220. Specifically, the acetabular cup 220 is anchored in the pelvis 210. The artificial acetabular cup 220 is composed of a shell in which a liner is inserted that provides the load bearing articulating surface. The femoral head 230 moves within the artificial acetabular cup 220. The femoral head 230 is anchored in the femur by a stem 240. This modular design allows the use of different materials that are suitable for the application.

(24) The defective hip joint is replaced with the artificial acetabular cup 220, the femoral head 230, and the stem 240, which replace the damaged natural articulating surfaces. The movement of the femoral head 230 in the artificial acetabular cup 220 is aided by the low friction so that the femoral head 230 and artificial acetabular cup 220 can withstand wear and oscillating mechanical load. Accordingly, a multi-phase ceramic composite may be used on the surface of the acetabular cup 220 and the surface of the femoral head 230 such that the friction between the surface of the acetabular cup 220 and the surface of the femoral head 230 is reduced and the hip joint is able to withstand wear.

(25) FIG. 2B illustrates an x-ray image of one embodiment of a multi-phase ceramic composite for use in a total hip replacement 250. Specifically, the femoral head 260 and a stem 270. Because the stem 270 provides bone integration. Titanium alloys are however not hard enough for low-friction wear-resistant acetabular cup (not shown) and femoral surfaces. Therefore, other materials are utilized to meet the requirements for the articulating interface between the femoral head 260 and acetabular cup. While the example in FIGS. 2A and 2B is related to total hip replacement, multi-phase ceramic compositions may be utilized in other joints, prosthesis, as well as other high friction and wear applications, such as drilling.

(26) FIG. 3 illustrates one embodiment example of a wear specimen for wear testing associated with multi-phase ceramic composites. The multi-phase ceramic material may be fabricated as a blocks of substrate 310. A pin 320 can be cut from the block of substrate 310. For example, the pin may have the dimensions of 3 millimeters by 3 millimeters by 10 millimeters. The pin 320 may then be set in epoxy as the wear specimen 330.

(27) FIG. 4A is a graph 400 illustrating the wear, measured in millimeters of a cobalt chromium (CoCr) alloy over time. The graph 400 illustrates the results of wear experimentation on a cobalt chromium alloy couple. In one embodiment, wear testing may be performed using a wear machine, where CoCr pin and block, are described above with respect to FIG. 3. A linear oscillatory motion may be used for testing. The linear wear of the pin and friction coefficient was measured continuously during the experiments. The coefficient of friction is defined as the ratio between the measured lateral force to the applied normal force. In one embodiment, the wear may be measured at weekly intervals.

(28) The linear wear of the CoCr alloy was measured over 768 hours of testing. The linear wear rate progressively decreased with time. During the first week of testing, the CoCr alloy exhibited the highest wear rates of 4.210.sup.5 m/hr to 2.410.sup.6 m/hr. As illustrated in graph 400, after 416 hours of testing a steady state wear rate of 4210.sup.8 m/hr was observed. The initial transitory period can be attributed to the original surface roughness of the bodies in contact and disappeared rapidly as the wear process modified the surface in contact.

(29) FIG. 4B is a graph 450 illustrating the wear of a multi-phase ceramic composite. Specifically, the graph 450 illustrates wear measured in millimeters of Al.sub.2O.sub.3GdAlO.sub.3 over time. As discussed above, the wear was measured at weekly intervals unless the machine stopped due to software issues. The linear wear of the Al.sub.2O.sub.3-GdAlO.sub.3 after 912 hours of wear experimentation is illustrated. Unlike the wear of the CoCr alloy, illustrated in graph 400, there is no aggressive wear at the start of testing. Linear wear rate was steady 2.410.sup.7 m/hr until 408 hours. After 408 hours, the linear wear decreased by a factor of forty and the wear rate changed to 6.010.sup.9 m/hr. Comparing the final linear wear rates of CoCr alloy, shown in graph 400 of FIG. 4A, wear rate is seven times higher than Al.sub.2O.sub.3GdAlO.sub.3, shown in graph 450 of FIG. 4B.

(30) FIG. 5 is a graph illustrating the friction coefficient of composite material as a function of the force exerted on the composite material. The friction coefficient is measured as a function of time. The friction coefficient exhibits dependency upon load, friction increased with load ranging from 0.02 to 0.5. The friction coefficient is 50% lower than CoCr alloy at load of 10 newtons.

(31) FIG. 6, which includes rows 600, 610, 620, 630, 640, 650, 660, 670, 680, 690, is a wear couple summary for different composites subjected to a force of ten newtons. While Al.sub.2O.sub.3GdAlO.sub.3 has been given as an example of a multi-phase ceramic composite, other composites may also be used. Row 600 is a summary of the wear and friction coefficient of typical composite material CoCr. However, the multi-phase ceramic composites discussed herein are shown to have less wear and lower coefficients of friction. For example, pin and disc combination of Al.sub.2O.sub.3Gd.sub.2O.sub.3 at row 610 showed less wear and demonstrated a lower coefficient of friction. Likewise, pin and disc combination Al.sub.2O.sub.3Y.sub.2O.sub.3 at row 670 showed less wear and demonstrated a lower coefficient of friction.

(32) FIG. 7A illustrates wear scarring of a CoCr alloy substrate after wear testing. Specifically, the wear scarring 700 on the substrate of the CoCr alloy occurred after 768 hours of testing. Wear grooves are observed. Definitive scarring 700 is approximately 0.45 mm in depth. The small particles removed by wear cause groove formation. Accordingly, a large amount of particle debris was generated. Particles are harder than the metal, abrasively wearing the surface.

(33) FIG. 7B illustrates wear scarring 750 of one embodiment of a multi-phase ceramic composite after wear testing. FIG. 7B shows the scarring after 912 hours of testing. Wear depth is about is about 0.1 mm, of depth observed for CoCr alloy. Accordingly, the scarring 750 of the multi-phase ceramic composite is considerably less than the scarring 700 illustrated in FIG. 7A.

(34) The following includes definitions of selected terms employed herein. The definitions include various examples and/or forms of components that fall within the scope of a term and that may be used for implementation. The examples are not intended to be limiting. Both singular and plural forms of terms may be within the definitions.

(35) References to one embodiment, an embodiment, one example, an example, and so on, indicate that the embodiment(s) or example(s) so described may include a particular feature, structure, characteristic, property, element, or limitation, but that not every embodiment or example necessarily includes that particular feature, structure, characteristic, property, element or limitation. Furthermore, repeated use of the phrase in one embodiment does not necessarily refer to the same embodiment, though it may.

(36) While for purposes of simplicity of explanation, illustrated methodologies are shown and described as a series of blocks. The methodologies are not limited by the order of the blocks as some blocks can occur in different orders and/or concurrently with other blocks from that shown and described. Moreover, less than all the illustrated blocks may be used to implement an example methodology. Blocks may be combined or separated into multiple components. Furthermore, additional and/or alternative methodologies can employ additional, not illustrated blocks. The methods described herein is limited to statutory subject matter under 35 U.S.C 101.

(37) To the extent that the term includes or including is employed in the detailed description or the claims, it is intended to be inclusive in a manner similar to the term comprising as that term is interpreted when employed as a transitional word in a claim.

(38) While example systems, methods, and so on have been illustrated by describing examples, and while the examples have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the systems, methods, and so on described herein. Therefore, the disclosure is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Thus, this application is intended to embrace alterations, modifications, and variations that fall within the scope of the appended claims, which satisfy the statutory subject matter requirements of 35 U.S.C. 101.

(39) Various operations of embodiments are provided herein. The order in which one or more or all of the operations are described should not be construed as to imply that these operations are necessarily order dependent. Alternative ordering will be appreciated based on this description. Further, not all operations may necessarily be present in each embodiment provided herein.

(40) As used in this application, or is intended to mean an inclusive or rather than an exclusive or. Further, an inclusive or may include any combination thereof (e.g., A, B, or any combination thereof). In addition, a and an as used in this application are generally construed to mean one or more unless specified otherwise or clear from context to be directed to a singular form. Additionally, at least one of A and B and/or the like generally means A or B or both A and B. Further, to the extent that includes, having, has, with, or variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term comprising.

(41) Further, unless specified otherwise, first, second, or the like are not intended to imply a temporal aspect, a spatial aspect, an ordering, etc. Rather, such terms are merely used as identifiers, names, etc. for features, elements, items, etc. For example, a first channel and a second channel generally correspond to channel A and channel B or two different or two identical channels or the same channel.

(42) Although the disclosure has been shown and described with respect to one or more implementations, equivalent alterations and modifications will occur based on a reading and understanding of this specification and the annexed drawings. The disclosure includes all such modifications and alterations and is limited only by the scope of the following claims.