Method for preparing gel composite material with piezoelectric property, and gel composite material and use thereof

Abstract

Provided are a method for preparing a gel composite material with a piezoelectric property, and the gel composite material and use thereof, which belongs to the field of intelligent road traffic. In the method, titanium-containing blast furnace slag and metal oxides (PbO and ZrO.sub.2) are sufficiently and uniformly mixed, an obtained mixture is calcined under a certain thermal system, on the theoretical basis of mineral-phase reconstruction-synergistic regulation of all valuable components, and the mixture is cooled to a room temperature with a furnace to obtain the gel composite material with a piezoelectric property.

Claims

1. A method for preparing a gel composite material with a piezoelectric property, specifically comprising the following steps: (1) crushing: crushing and grinding a titanium-containing blast furnace slag to powder; (2) uniform mixing: uniformly mixing the powdery titanium-containing blast furnace slag obtained in step (1) with lead and zirconium oxides to obtain a multi-component system mixture; and (3) modification and reconstruction: in a first stage, conducting heat preservation at 600° C.-768.8° C. for 0.5-1.5 h, in a second stage, accelerating heating to 800° C.-910° C. and conducting heat preservation for 1.5-2.5 h, in a third stage, cooling to 700° C.-768° C. and conducting heat preservation for 1.0-2.5 h, and cooling to a room temperature with a furnace to obtain a gel composite material containing a piezoelectric phase and a gel phase; wherein, the piezoelectric phase is PbZr.sub.x Ti.sub.1−xO.sub.3 (0<x<1), and the gel phase is Ca2MgSi2O7.

2. The method for preparing a gel composite material with a piezoelectric property according to claim 1, wherein in step (2), three elements Pb, Zr and Ti of the multi-component system mixture have a molar ratio of Pb:Zr:Ti at 1.1:0.52:0.48.

3. The method for preparing a gel composite material with a piezoelectric property according to claim 2, wherein in step (2), the lead and zirconium oxides are PbO and ZrO.sub.2 separately.

4. The method for preparing a gel composite material with a piezoelectric property according to claim 1, wherein the titanium-containing blast furnace slag has a mass percentage of TiO2 larger than 20%.

5. The method for preparing a gel composite material with a piezoelectric property according to claim 1, comprising the following steps: in step (3), in a first stage, conducting heat preservation at 700° C. for 1 h, in a second stage, accelerating heating to 800° C.-910° C. and conducting heat preservation for 2 h, in a third stage, cooling to 750° C. and conducting heat preservation for 1 h, and cooling to a room temperature with a furnace to obtain a gel composite material containing a piezoelectric phase and a gel phase.

6. The method for preparing a gel composite material with a piezoelectric property according to claim 5, wherein a heating rate of the first stage is 5-10° C./min, a heating rate of the second stage is larger than or equal to 10° C./min, and a cooling rate of the third stage is 5-10° C./min.

7. A gel composite material with a piezoelectric property obtained by method of claim 1, wherein the gel composite material contains a piezoelectric phase and a gel phase, wherein the piezoelectric phase is PbZr.sub.xTi.sub.1−xO.sub.3 (0<x<1) and accounts for 50-60% of a total mass of a system, and the gel phase is Ca.sub.2MgSi.sub.2O.sub.7 and accounts for 8-15% of the total mass of the system.

8. The gel composite material with a piezoelectric property according to claim 7, wherein in step (2) of the method, three elements Pb, Zr and Ti of the multi-component system mixture have a molar ratio of Pb:Zr:Ti at 1.1:0.52:0.48.

9. The gel composite material with a piezoelectric property according to claim 7, wherein in step (2) of the method, the lead and zirconium oxides are PbO and ZrO2 separately.

10. The gel composite material with a piezoelectric property according to claim 7, wherein the titanium-containing blast furnace slag has a mass percentage of TiO2 larger than 20%.

11. The gel composite material with a piezoelectric property according to claim 7, wherein in step (3) of the method, in a first stage, conducting heat preservation at 700° C. for 1 h, in a second stage, accelerating heating to 800° C.-910° C. and conducting heat preservation for 2 h, in a third stage, cooling to 750° C. and conducting heat preservation for 1 h, and cooling to a room temperature with a furnace to obtain a gel composite material containing a piezoelectric phase and a gel phase.

12. The gel composite material with a piezoelectric property according to claim 7, wherein a heating rate of the first stage is 5-10° C./min, a heating rate of the second stage is larger than or equal to 10° C./min, and a cooling rate of the third stage is 5-10° C./min.

13. A cement concrete, wherein the cement concrete comprises the gel composite material with a piezoelectric property according to claims 7.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 is a thermodynamic curve diagram of relevant reaction in a modification and reconstruction process of the present disclosure;

[0046] FIG. 2 is a thermodynamic curve diagram in a modification and reconstruction process of the present disclosure;

[0047] FIG. 3 is a scanning electron microscope image of a sample obtained in example 1;

[0048] FIG. 4 is a scanning electron microscope image of a sample obtained in example 2;

[0049] FIG. 5 is a scanning electron microscope image of a sample obtained in example 3;

[0050] FIG. 6 is a scanning electron microscope image of a sample obtained in example 4;

[0051] FIG. 7 is an X-ray diffraction image of mineral-phase reconstruction under different calcination temperatures of the present disclosure;

[0052] FIG. 8 is a piezoelectric coefficient d.sub.33 of a sample under different calcination temperatures in the present disclosure; and

[0053] FIG. 9 is a gel active component content of a sample under different calcination temperatures in the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0054] The present disclosure is further described below with reference to specific examples.

[0055] Table 1 Modification and reconstruction process technological parameters in examples and a comparative examples

[0056] A titanium-containing blast furnace slag block was crushed and ground in a grinding tank for 60 s, after drying, 16.472 g of the ground material was weighed and mixed with 24.844 g of analytically pure lead oxide and 6.493 g of analytically pure zirconium dioxide, an obtained mixture was ground with an agate mortar for 30 min or more to ensure that the components were fully and uniformly mixed, and a muffle furnace is used as a heating device. In the first stage (heating stage), the mixed powder was heated to 700° C. at a heating rate of 5° C./min and heat preservation was conducted for 1 h; in the second stage, heating was conducted to 800-910° C. at a heating rate of 10° C./min and heat preservation was conducted for 2 h; and in the final stage, heat preservation was conducted at 750° C. for 1 h. After cooling to a room temperature with a furnace, a gel composite material sample with a piezoelectric property was obtained and the powder changed from gray to orange after calcination. A thermodynamic curve diagram of relevant reaction in a modification and reconstruction process was shown in FIG. 1 and a thermodynamic curve diagram in a modification and reconstruction process was shown in FIG. 2.

[0057] According to different temperatures in the second stage of the modification and reconstitution process, four examples and one comparative example were set as shown in Table 1.

[0058] Performance Tests

[0059] (1) EDS Energy Spectrum Analysis

[0060] Table 2 EDS energy spectrum analysis results (at %) of samples in each example

[0061] FIGS. 3-6 are scanning electron microscope images of the samples obtained in examples 1-4, respectively. It can be seen from FIG. 3 that there were three areas with different contrasts: gray area Sp1, black area Sp2, and gray white area Sp3. The black area in FIGS. 4-5 is an epoxy plane. Combined with an SEM-EDS energy pectrum analysis in Table 2: in FIG. 5, Sp1 presented a vein shape, main elements were Ca and Ti, and the atomic percentage content was 96.21%, which was a perovskite phase, and a small amount of Zr and Pb entered the mineral phase; main elements in Sp2 were Ca, Al, Mg and Si, and a small amount of a PZT phase was contained, that is, diopside in a titanium slag reacted with PbZrO.sub.3 to generate PbTiO.sub.3 and a feldspar phase; and Sp3 presented gray-white lines and was also in a process of transformation from the diopside phase to the feldspar phase, which reflected an initial stage of mineral-phase reconstruction. In FIG. 4, the Pb content in Sp1 reached 38.06% and Zr/Ti=1.406, such that a trigonal phase (zirconium-rich) PZT and a PZT phase with partially dissolved Ca existed in Sp1. The contents of Si and Al were both higher than 11%, such that a feldspar phase containing Pb also existed. In Sp3, Zr/Ti≈1, indicating a PZT phase at an MPB phase boundary. In FIG. 5, the Pb content in Sp3 was as high as 39.69%. The PZT phases in Sp1 and Sp3 both contained a zirconium-rich PZT phase and an MPB type PZT phase, and the feldspar phase in Sp1 wrapped the PZT phase. In FIG. 6, the volatilization of PbO led to a decrease in the Pb content, a titanium-rich PZT phase existed in Sp1, thus a zirconium-rich state was shifted to a titanium-rich state due to thermolability of PbZrO.sub.3. Most of Sp1 and 3 belong to a Pb-containing silicate phase and a part of a PZT phase.

[0062] The ribbon and vein PZT phases were tightly wrapped by the feldspar phase, while the larger-sized and irregular PZT phases were mostly distributed in an outer layer of particles. Combined with the EDS analysis, it can be seen that the Zr content in an outer PZT phase was significantly higher than that in an inner PZT phase. The difference in composition of the PZT phase meant that a formation mechanism was not single: a titanium source came from perovskite and diopside, and reaction was conducted to generate zirconium-rich Pb(Zr.sub.0.7Ti.sub.0.3)O.sub.3, MPB-type PbZr.sub.0.58Ti.sub.0.42O.sub.3 and (Pb, Ca)Zr.sub.xTi.sub.1−xO3 (partially dissolved Ca).

[0063] (2) XRD Detection

[0064] The gel composite material obtained in examples 1-4 was tested. An X-ray diffraction pattern was shown in FIG. 7 (TS represented an untreated titanium-containing blast furnace slag). An XRD phase analysis showed that characteristic peaks of 3-Pb(Zr.sub.0.7Ti.sub.0.3)O.sub.3 and 4-Ca.sub.2(Mg.sub.0.75Al.sub.0.25)(Si.sub.1.75Al.sub.0.25O.sub.7) appeared at 800° C., the zirconium-rich Pb(Zr.sub.0.7Ti.sub.0.3)O.sub.3 was gradually transformed into PbZr.sub.0.58Ti.sub.0.42O.sub.3 with rise of a temperature, that is, transformation from a trigonal phase to a tetragonal phase occurred, such that a crystal structure was near an MPB phase boundary. After the mineral-phase reconstruction, Ca(Mg, Al)(Al, Si).sub.2O.sub.6 in the titanium slag was transformed into Ca.sub.2(Mg.sub.0.75Al.sub.0.25)(Si.sub.1.75Al.sub.0.25O.sub.7). At 910° C., intensity of characteristic peaks of PZT decreased since Pb was compounded with different silicates and the PZT content was reduced. With increase of temperatures, peak positions and peak shapes remained basically unchanged, but intensity of a diffraction peak gradually increased, the shape was symmetrical and sharp, and the peak gradually approached an MPB morphology phase boundary.

[0065] It can be seen from a partial enlarged view of the characteristic peak at 29-33° that as the temperature increased, the peak position near 2θ≈31° gradually shifted to the left. According to a Bragg formula: 2dsinθ=nλ, an interplanar spacing and a lattice constant increased, zirconium-rich Pb(Zr.sub.0.7Ti.sub.0.3)O.sub.3 gradually transformed into MPB-type PbZr.sub.0.58Ti.sub.0.42O.sub.3, Zr.sup.4+ had a radius of 0.072 nm, Ti4+ had a radius of 0.0605 nm, and in Pb(Zr.sub.0.7Ti.sub.0.3)O.sub.3, the Zr.sup.4+ and the Ti.sup.4+ had average ionic radius of 0.06855 nm, after transformation, the average ionic radius was 0.06717 nm, such that a lattice constant and a lattice distortion increased, and a peak position shifted to a low angle. It can be seen from a right side of FIG. 7 that there was an asymmetric structure in a peak shape, indicating that there were multiple “contributions” to the peak, namely Pb(Zr.sub.0.7Ti.sub.0.3)O.sub.3 (trigonal phase), PbZr.sub.0.58Ti.sub.0.42O.sub.3 (MPB) and Ca.sub.2(Mg.sub.0.75Al.sub.0.25)(Si.sub.1.75Al.sub.0.25O.sub.7).

[0066] (3) Piezoelectric Property Detection

[0067] Piezoelectric effect: when subjected to a mechanical stress from a certain direction, electrical polarization occurred internally to generate a potential difference. A larger d.sub.33 value indicated that more charges were generated inside, the electrical polarization was stronger and the potential difference was larger, which meant a better mutual coupling property between a mechanical stress and a dielectric property.

[0068] The piezoelectric coefficient d.sub.33 of examples 1-4 was shown in FIG. 8. It can be concluded that d33 slightly increased in a range of 700-800° C., reached a maximum value of 6.0 pC/N at 870° C. during 800-870° C. and reduced to 4.5 pC/N at 910° C. It should be emphasized that a piezoelectric property of the second stage of the comparative example 1 was lower than that of the four examples when heat preservation was conducted at 700° C.

[0069] (4) Gel Activity Detection

[0070] The content of the gel active component was shown in FIG. 9. It can be concluded that with extension of leaching time, the leaching amount gradually increased, but a dissolution rate decreased. The leaching amount of a sample after heat preservation at 910° C. for 1 h was the largest and can reach 14.67%. The leaching amount of the titanium slag at different time points was maintained at a low standard, indicating that the hydration activity of the reconstructed and modified titanium slag had a high correlation with a leaching percentage, which effectively improved the hydration activity of a silicate in the original titanium slag. Titanium-containing diopside acted as a hydration inert phase and its participation in the hydration process resulted in a poor gel property of C-S-H (calcium silicate hydrate). After the mineral phase was reconstructed, the titanium-containing diopside was transformed into the feldspar phase, which had a good gelling activity. After the mineral-phase reconstruction, the structures of the perovskite and the diopside changed, which promoted the formation of the feldspar phase. The expression of the gel activity was closely related to a dissolution behavior of Ca.sup.2+, Si.sup.4+ and Al.sup.3+ in a water system and an EDTA-alkali solution can selectively dissolve a silicate phase and an aluminate phase. During the dissolution process, fine particles were continuously formed by breaking, wrapped silicate particles were continuously released, thus the contact with the EDTA-alkali solution was accelerated and a reaction rate was slightly faster in an early stage. The perovskite in the original titanium slag had poor reactivity and strong acid and alkali resistance, while the various mineral phases in the titanium slag were embedded and wrapped with each other, and difficult to dissociate and had low reactivity and a limited contact and reaction area with the EDTA-alkali solution. When an extreme small amount of the diopside reacted with the EDTA-alkali solution to form a chelate complex, the wrapped perovskite was released, such that the leaching percentage slowed down in a later stage and the leaching amount tended to be stable. It was indicated that the hydration activity of the silicate can be properly improved after mineral-phase modification and reconstruction.

[0071] Table 3 Proportion of gel phase in samples of each example

[0072] Item Example 1 Example 2 Example 3 Example 4 Mass percentage of gel phase/% 12.27 12.22 11.49 14.67

[0073] It should be noted that a product of comparative example 1 had basically no gel properties after searching under a low piezoelectric property.

[0074] In particular, it was measured that the piezoelectric phase of the samples in each example accounted for 50-60% of the total mass of the system.

[0075] (5) Dissolution Evaluation of Heavy Metals

[0076] Table 4 Dissolution amount of metal ions in samples prepared in each example/(mg/L)

[0077] Item Example 1 Example 2 Example 3 Example 4 Pb 0.29 0.23 0.26 0.35 Ti 0.22<0.02<0.02 0.12

[0078] According to the standard of CB 5083.3-2007, the content of lead element in the tertiary soil is ≤500 mg/kg and the leaching standard of a hazardous waste is ≤5 mg/L. It can be seen from Table 4 that the Pb leaching amount of the obtained PZT/titanium-containing blast furnace slag-based composite material under different conditions met the national safety standard.

[0079] In order to clarify leaching characteristics of Pb in the samples, the content of lead and titanium elements in the samples was measured as shown in Table 5 below:

[0080] Table 5 XRF (wt %) of samples prepared in each example

[0081] Item Example 1 Example 2 Example 3 Example 4 PbO 49.412 48.519 49.581 49.526 TiO.sub.2 6.581 6.643 6.541 6.425

[0082] It can be seen from Table 5 that each group of samples had a relatively high lead content whose mass percentage accounted for about 49% of the system. It can be concluded that the leaching amount of lead was not necessarily related with the content of lead, but was closely related with an endowed form, a texture structure and a leaching capacity of a PZT phase and a Pb-containing silicate phase in each group of samples.

[0083] It can be seen from Table 4 that the leaching amount of titanium ions was ≤0.22 mg/L. After a mineral-phase reconstruction of free TiO.sub.2 in the titanium-containing blast furnace slag, the TiO.sub.2 was endowed in the titanium slag system in a form of a PZT solid solution, a chemical property was relatively stable and only extremely weakly water solubility existed.

[0084] In the above examples, only different holding temperatures in the second stage are compared and other parameters such as the heating rate, the holding time and the cooling rate are all best embodiments. The product of the present disclosure can be prepared within the scope of the claims of the present disclosure, but a piezoelectric property and a gel property are not best. The examples listed in the present disclosure are only one of the embodiments of the present disclosure and do not limit the embodiments described in the present disclosure. As long as modifications or equivalent substitutions are made without departing from the spirit and principle of the present disclosure, the scope of the claims of the present disclosure shall be covered. For example, scopes of the reaction temperatures and the reaction time in each step of the present disclosure are reasonable and preferable. In fact, the reaction temperatures and the reaction time both have a broad scope and as long as the product of the present disclosure can be prepared, the values not in the scope of the present disclosure belong to one embodiment not mentioned in the present disclosure.