Detailed Description
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
The invention provides zirconia ceramic, which comprises a zirconia matrix, a stabilizer and a toughening agent, wherein the stabilizer is one or more of yttrium oxide, erbium oxide, neodymium oxide and samarium oxide, and the toughening agent is niobium oxide and/or tantalum oxide; based on the total molar weight of the zirconia ceramics, the content of the stabilizing agent is 2-4mol%, the content of the toughening agent is 0.45-1.4mol%, and the difference between the molar percentages of the stabilizing agent and the toughening agent is 1.5-2.6 mol%. By controlling the contents of the stabilizer and the toughening agent, the zirconium oxide ceramic has good toughness, good impact resistance and good thermal aging resistance.
In the present invention, the composition of the above zirconia ceramic may be a ceramic containing zirconia, yttria and niobia; alternatively, zirconium oxide, yttrium oxide, and tantalum oxide; alternatively, zirconium oxide, erbium oxide, and niobium oxide; alternatively, zirconium oxide, erbium oxide, and tantalum oxide; alternatively, zirconium oxide, neodymium oxide, and niobium oxide; alternatively, zirconium oxide, neodymium oxide, and tantalum oxide; alternatively, zirconium oxide, samarium oxide and niobium oxide; alternatively, zirconium oxide, samarium oxide, and tantalum oxide; or zirconium oxide, and two or more of yttrium oxide, erbium oxide, neodymium oxide and samarium oxide, and niobium oxide and/or tantalum oxide.
In the invention, in order to further improve the toughness, the impact resistance and the thermal aging resistance of the zirconia ceramic, preferably, the content of the stabilizer is 2.5-3.5mol%, and the content of the toughening agent is 0.65-1.15 mol%; further preferably, the difference of the molar percentage of the stabilizer and the toughening agent is 1.9-2.4 mol%.
In the present invention, preferably, the zirconia ceramic has a hardness of 1150Hv, preferably 1170-1260 Hv; the drop hammer height of the zirconia ceramics is more than 26 cm; in the test result of the thermal aging resistance of the zirconia ceramic, after the zirconia ceramic is subjected to heat leveling at 1100-1200 ℃, the zirconia ceramic can still keep the drop height before the heat leveling.
The invention also provides a preparation method of the zirconia ceramic, which comprises the following steps:
(1) adding water, a dispersing agent and a binder into composite powder containing zirconium oxide, a stabilizing agent and a toughening agent for wet milling to obtain slurry, wherein the stabilizing agent is one or more of yttrium oxide, erbium oxide, neodymium oxide and samarium oxide, and the toughening agent is niobium oxide and/or tantalum oxide; based on the total molar weight of the composite powder, the content of the stabilizer is 2-4mol%, the content of the toughening agent is 0.45-1.4mol%, and the difference between the molar percentages of the stabilizer and the toughening agent is 1.5-2.6 mol%;
(2) and drying and sintering the slurry to obtain the zirconia ceramic.
In the present invention, zirconia, yttria, erbium oxide, neodymium oxide and samarium oxide in the stabilizer, and niobium oxide and/or tantalum oxide may each be provided in the form of a high purity oxide powder. For example, yttria and zirconia can be prepared by using a tetragonal zirconia powder (median particle diameter of 0.3-0.6 μm, specific surface area of 7-13 m) stabilized with 2-4mol% yttria2In terms of/g), wherein the content of yttrium oxide is based on zirconium oxide. The erbium oxide can be pure erbium oxide powder (the median diameter is 3-7 μm). The neodymium oxide can adopt pure neodymium oxide powder (the median diameter is 3-7 μm). The samarium oxide can be pure samarium oxide powder (samarium oxide)Median particle size of 3-7 μm). Niobium oxide can be niobium pentoxide (with a median particle size of 8-10 μm) powder. The tantalum oxide can be tantalum pentoxide powder (with a median particle size of 8-10 μm).
In the present invention, step (1) is carried out by grinding powders of the above-mentioned oxides as raw materials to reduce the particle diameter and obtain a slurry. The grinding process is wet grinding, and the specific process can comprise the following steps: mixing the powder of the oxides and water into slurry, ball-milling and mixing, and then grinding and crushing to make the particle size median of the oxides to be nano-scale (such as 250-500 nm). More specifically, the oxides are added with water in a ball milling tank according to the content of the oxides for ball milling for 8-10h, then a dispersing agent and water are added in a sand mill for sand milling for 8-10h, finally a binding agent (such as PVA and/or polyethylene glycol 4000) with a proper proportion is added, and then stirring is carried out for 2-4 h. Ball milling pots and sand mills use an inner liner of zirconia ceramic and zirconia milling balls. The selected particle size of the zirconia grinding balls, the proportion of the grinding balls with different particle sizes, the weight ratio of the grinding balls to the powder and the amount of water can be controlled to realize the expected particle size of the oxide.
In the present invention, various oxide feeds make up the powder. The feeding amount of various oxides finally meets the composition requirements of the obtained zirconia ceramics. Preferably, the content of the stabilizer is 2.5-3.5mol%, and the content of the toughening agent is 0.65-1.15 mol%.
In the invention, in order to further improve the toughness, the impact resistance and the thermal aging resistance of the zirconia ceramic, the difference between the molar percentages of the stabilizer and the toughening agent is preferably 1.9-2.4 mol%.
In the present invention, preferably, in step (1), the dispersant is selected from at least one of hypromellose, sodium carboxymethylcellulose, and triethanolamine; the binder is selected from polyvinyl alcohol and/or polyethylene glycol 4000. The dispersing agent can promote the components in the powder to be uniformly mixed. The binder is beneficial to the formability of the powder. Preferably, the binder is polyvinyl alcohol (PVA) and polyethylene glycol 4000 (PEG 4000), and the molar ratio of polyvinyl alcohol to polyethylene glycol 4000 is 1: 1-2, preferably 1: 1. In the present invention, the dispersant and the binder are commercially available.
In the present invention, the dispersant is preferably added in an amount of 0.005 to 0.5% by weight, preferably 0.01 to 0.1% by weight, based on the powder.
In the present invention, the binder is preferably added in an amount of 0.5 to 5% by weight, preferably 2 to 5% by weight, of the powder.
In the present invention, preferably, the solid content of the slurry is 20 to 60% by weight, preferably 25 to 55% by weight. A better abrasive effect can be achieved.
In the present invention, various drying methods, for example, spray drying, may be used in the step (2) to form a spherical powder having high flowability. The air inlet temperature of spray drying is preferably 220-280 ℃, the air outlet temperature is preferably 100-120 ℃, and the centrifugal rotating speed is 10-20 r/s.
In the present invention, after the slurry is dried in the step (2), molding may be performed, followed by sintering. The molding can adopt dry pressing, isostatic pressing, injection molding, hot-press molding and other molding modes. Preferably dry pressing molding, a press with 180 and 220 tons of tonnage can be used for molding by using the oil pressure of 6-10MPa, such as the shape of a rear cover of a mobile phone. The sintering procedure comprises: raising the temperature from room temperature to 600 ℃ for 2h after 400min, raising the temperature from 600 ℃ to 1150 ℃ after 300min and preserving the heat for 2h, raising the temperature from 1150 ℃ to 1300 ℃ for 2h after 150min, raising the temperature from 1300 ℃ to 1450-1600 ℃ after 50min and preserving the heat for 1-2h, then reducing the temperature to 900 ℃ after 150min, and finally naturally cooling to room temperature.
In the invention, the zirconia ceramics obtained after sintering also comprises the steps of flat grinding and polishing, and processing and cutting into final products by using a laser. The zirconia ceramics are large-area thin-sheet ceramics and can deform in processing, so that heat leveling treatment is required under the conditions of 1100-1200 ℃. The prior art zirconia ceramics have poor strength, toughness and impact resistance after heat leveling. The zirconia ceramic has good toughness, good impact resistance and good thermal aging resistance (namely, the performance of the zirconia ceramic is kept unchanged before and after heat leveling treatment) by controlling the contents of the stabilizer and the toughening agent in the zirconia matrix.
The invention provides zirconia ceramics prepared by the preparation method. The zirconia ceramic has good toughness, good impact resistance and good thermal aging resistance.
The invention also provides an application of the zirconia ceramic in preparing electronic product shells or ornaments.
The present invention will be described in detail below by way of examples, but the present invention is not limited to the following examples.
Fracture toughness Kic: indenter indentation method (diamond indenter, force 10kg, pressure test time 15 s).
Hardness Hv: a hardness meter and an indentation method (a diamond indenter, a force of 10kg, a pressure test time of 15 s).
Drop hammer impact: the sample was placed on a platform using a drop hammer impact tester (manufacturer CKSI, model E602 SS), the center of the sample was hammered with a drop hammer weighing 60g, starting from a height of 5cm, and increasing in height of 5cm each time if no crack occurred, until the sample was visually observed to crack, and the height value was recorded.
Aging rate: the ratio of the drop weight impact height of the sample after being subjected to 1100 ℃ heat leveling to the drop weight impact height before being subjected to heat leveling.
Compactness: taking the average pit number (more than 20 μm) in the range of 10X 10mm on the large surface of the polished sample
XRF detection: the element content of the polished sample was measured using an energy dispersive X-ray fluorescence spectrometer EDX-7000.
Example 1
Raw materials: 200g of composite powder containing 3mol% of yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)1mol%。
Adding water into the raw materials in a ball milling tank, ball milling for 8h, then adding 0.02wt% of hydroxypropyl methylcellulose and water into a sand mill, carrying out sand milling for 10h, and finally adding 4wt% of binder (PEG 4000 and PVA with a molar ratio of 1: 1) of powder, stirring for 0.5h to form slurry for spraying, wherein the solid content is 25 wt%;
feeding the slurry into a spray tower for spray drying (the inlet air temperature is 250 ℃, the outlet air temperature is 110 ℃, and the centrifugal rotating speed is 15 revolutions per second) to form spherical powder with stronger fluidity for dry pressing, and then performing dry pressing (a press with 200 tons of tonnage uses the oil pressure of 8 MPa);
and (2) heating the formed powder from room temperature to 600 ℃ for 2h after 400min, heating from 600 ℃ to 1150 ℃ for 300min and keeping the temperature for 2h, heating from 1150 ℃ to 1300 ℃ for 150min and keeping the temperature for 2h, heating from 1300 ℃ to 1450 ℃ and 1600 ℃ after 50min and keeping the temperature for 1-2h, then cooling to 900 ℃ after 150min, and finally sintering in the air in the process of naturally cooling to room temperature.
And (3) carrying out CNC (computer numerical control) machining, then carrying out heat smoothing at 1100 ℃, grinding, polishing and laser cutting to obtain a final sample, wherein the size of the final sample is 150 x 75 x 0.6mm, and the shape and the size of the mobile phone rear cover are obtained.
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 68.4wt% of Zr, 4.1wt% of Y, and 1.45wt% of Nb.
Example 2
The preparation method is the same as example 1, except that the raw materials: 200g of composite powder containing 3mol% of yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)1.35mol%。
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 67.8wt% of Zr, 4wt% of Y and 1.9wt% of Nb.
Example 3
The preparation method is the same as example 1, except that the raw materials: 200g of composite powder containing 3mol% of yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)0.5mol%。
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 69.2wt% of Zr, 4.1wt% of Y, and 0.7wt% of Nb.
Example 4
The preparation method is the same as example 1, except that the raw materials: 200g of zirconia powder containing 2.5mol% of yttria, wherein niobium pentoxide (chemical formula Nb)2O5)0.5mol%。
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 69.5wt% of Zr, 3.5wt% of Y, and 0.7wt% of Nb.
Example 5
The preparation method is the same as example 1, except that the raw materials: 200g of a composite powder containing 2.5mol% of yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)1mol%。
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 69wt% of Zr, 3.4wt% of Y, and 1.44wt% of Nb.
Example 6
The preparation method is the same as example 1, except that the raw materials: 200g of composite powder containing 3.5mol% yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)1mol%。
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 67.8wt% of Zr, 4.85wt% of Y, and 1.43wt% of Nb.
Example 7
The preparation method is the same as example 1, except that the raw materials: 200g of composite powder containing 3.5mol% yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)1.2mol%。
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 67.5wt% of Zr, 4.8wt% of Y, and 1.69wt% of Nb.
Comparative example 1
The preparation method is the same as example 1, except that the raw materials: 200g of composite powder containing 3mol% of yttria-stabilized zirconia.
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 69.9wt% of Zr and 4.1wt% of Y.
Comparative example 2
The preparation method is the same as example 1, except that the raw materials: 200g of composite powder containing 3mol% of yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)0.3mol%。
The prepared sample was subjected to high-energy XRF detection, and the composition elements contained 69.3wt%, Y4.1 wt%, and Nb 0.43 wt%.
Comparative example 3
The preparation method is the same as example 1, except that the raw materials: 200g of composite powder containing 3mol% of yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)1.6mol%。
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 67.4wt% of Zr, 4.1wt% of Y, and 2.3wt% of Nb.
Comparative example 4
The preparation method is the same as example 1, except that the raw materials: 200g of a composite powder containing 2.15mol% of yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)0.15mol%。
The prepared sample is subjected to high-energy XRF detection, and the composition elements comprise 70.5wt% of Zr, 3wt% of Y and 0.2wt% of Nb.
Comparative example 5
The preparation method is the same as example 1, except that the raw materials: 200g of composite powder containing 4mol% of yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)1mol%。
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 67.1wt% of Zr, 5.4wt% of Y, and 1.43wt% of Nb.
Comparative example 6
The preparation method is the same as example 1, except that the raw materials: 200g of a composite powder containing 2mol% of yttria-stabilized zirconia, wherein niobium pentoxide (chemical formula Nb)2O5)1mol%。
The prepared sample was subjected to high-energy XRF detection, and the constituent elements contained 69.7wt% of Zr, 2.7wt% of Y, and 1.45wt% of Nb.
TABLE 1
| |
Hardness (Hv)
|
Toughness (Mpam0.5)
|
Number of pits (individual)
|
Drop hammer before heat smoothing (cm)
|
Drop hammer (cm) after heat smoothing
|
Aging Rate (%)
|
| Example 1
|
1210
|
12.2
|
0
|
30
|
30
|
0
|
| Example 2
|
1170
|
13.2
|
0
|
27
|
27
|
0
|
| Example 3
|
1260
|
9.5
|
0
|
26
|
26
|
0
|
| Example 4
|
1250
|
10.1
|
0
|
29
|
29
|
0
|
| Example 5
|
1205
|
12.6
|
0
|
27
|
27
|
0
|
| Example 6
|
1230
|
11
|
0
|
27
|
27
|
0
|
| Example 7
|
1215
|
12
|
0
|
26
|
26
|
0
|
| Comparative example 1
|
1290
|
5.5
|
0
|
22
|
22
|
0
|
| Comparative example 2
|
1290
|
8
|
0
|
23
|
23
|
0
|
| Comparative example 3
|
1140
|
14
|
0.15
|
24
|
24
|
0
|
| Comparative example 4
|
1270
|
12
|
0
|
30
|
15
|
50
|
| Comparative example 5
|
1250
|
7.5
|
0
|
21
|
21
|
0
|
| Comparative example 6
|
1203
|
12.5
|
0
|
30
|
20
|
33 |
As can be seen from Table 1, the zirconia ceramic provided by the invention has the characteristics of good hardness, low density, good toughness, high strength and thermal aging resistance. The difference between the mol percentage content of the stabilizer and the mol percentage content of the toughening agent is controlled within the range of 1.5-2.6mol%, the thermal aging resistance and the strength of the zirconia ceramic can be further improved, while the content of the toughening agent and the stabilizer of the comparative example is not within the range of the invention, and the comprehensive performance of the obtained zirconia ceramic is inferior to that of the zirconia ceramic of the invention.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various technical features described in the above embodiments can be combined in any suitable manner without contradiction, and the invention is not described in any way for the possible combinations in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.