CN109306521B - Manufacturing method of electrically conductive Ca12Al14O32:2e-electron compound - Google Patents

Abstract

Electrically conductive Ca₁₂Al₁₄O₃₂:2e^‑The preparation process of electronic compound belongs to the field of mayenite type inorganic electronic compound material technology. Mixing CaCO₃Powder and Al₂O₃The powders are mixed uniformly in a mass ratio of 27:15 and subjected to chemical reaction at 1450 ℃ to synthesize Ca₁₂Al₁₄O₃₃With Ca₃Al₂O₆Eutectic precursor, Ca in the precursor₁₂Al₁₄O₃₃With Ca₃Al₂O₆The mass ratio of (2): 1; uniformly mixing the eutectic precursor and metal Al simple substance powder, and then carrying out mechanical alloying in an Ar gas environment for 15 min; the powder after mechanical alloying reacts in situ to synthesize the electric conduction Ca₁₂Al₁₄O₃₂:2e^‑The preparation method can obtain the electronic compound with the electron concentration reaching the theoretical maximum value of 2.3 × 10 within 5 minutes²¹cm^‑3Polycrystalline Ca with a relative density of 99.8%₁₂Al₁₄O₃₂:2e^‑The method is simple and efficient, the preparation period is extremely short, the cost is low, and batch production is easy to realize.

Description

Manufacturing method of electrically conductive Ca12Al14O32:2e-electron compound

technical field

The invention belongs to the technical field of mayenite-type inorganic electronic compound materials, in particular to a method for preparing Ca ₁₂ Al ₁₄ O ₃₂ :2e ^- electronic compound materials by utilizing chemical reaction-spark plasma sintering (SPS)-.

Background technique

Dodecacalcium heptaaluminate (Ca ₁₂ Al ₁₄ O ₃₃ ) is a typical phase in the hydration product of high alumina cement. It has good electrical insulation and belongs to the cubic crystal system. In 1915, it was synthesized by Rankin and Wright using CaO and Al ₂ O ₃ , and later Eitel and Bussem determined that the stoichiometric ratio of CaO to Al ₂ O ₃ was 12:7, and one unit cell contained two Ca ₁₂ Al ₁₄ O ₃₃ molecules, there are 66 oxygen ions in the unit cell containing 2 molecules, two of which are enclosed in the cage space formed by the lattice framework in the form of free oxygen, available [Ca ₂₄ Al ₂₈ O ₆₄ ] (O ^2- ) ₂ to represent the chemical formula of a unit cell, the positively charged [Ca ₂₄ Al ₂₈ O ₆₄ ] ⁴⁺ part is the main frame part of the lattice, in order to maintain electrical neutrality, 2 O ^2- Randomly occupy any 2 of the 12 cage cavities, because O ^2- has weak binding force to the positively charged framework [Ca ₂₄ Al ₂₈ O ₆₄ ] ⁴⁺ , so it can shuttle in the cage cavities. The adjacent cages communicated with each other by means of holes (about 0.1 nm in diameter) on the cage wall. Under certain conditions, free O ^2- can migrate to other places, and can also be replaced by other monovalent anions (such as H ^- , F ^- , Cl ^- , OH ^- ) and e ^- to generate various kinds of Ca ₂₄ Al ₂₈ O ₆₆ derivative. The resulting derivatives still retain the original crystal structure of Ca ₂₄ Al ₂₈ O ₆₆ . When part of O ^2- in the cage cavity in Ca ₂₄ Al ₂₈ O ₆₆ is replaced by electron e ^- , the cage cavity will contain O ^2- and electron e ^- , that is, [Ca ₂₄ Al ₂₈ O ₆₄ ](O ^2- ) _2-x (e ^- ) _2x , when it is completely replaced by electron e ^- , it will form an electronic compound [Ca ₂₄ Al ₂₈ O ₆₄ ] ⁴⁺ :4e ^- (abbreviation: C12A7:e ^- ) with good electron conduction Moreover, it can exist stably in the atmospheric environment below 400 °C, and has shown good application potential in the fields of catalysts, ion etching, and cathode field electron emission.

At present, the research on C12A7:e ^- electronic compounds mainly focuses on the exploration of preparation methods and performance optimization. The reduction synthesis under high temperature CO/ _CO2 mixed atmosphere, the direct reduction synthesis in graphite crucible and the use of active metals have been reported. The preparation time of methods such as reduction synthesis at high temperature is usually more than 30h, so how to shorten the preparation time and optimize the emission performance has become a problem to be solved for this system

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a simple and efficient preparation method for rapidly preparing high-purity conductive Ca ₁₂ Al ₁₄ O ₃₂ : 2e ^- electronic compound. The preparation method provided by the invention is simple and fast, the preparation period is greatly shortened, and the preparation process does not need to introduce a gaseous or solid reducing agent, which is a clean preparation process and is beneficial to mass production and application.

The present invention adopts spark plasma sintering (SPS) technology to synthesize high-purity Ca ₁₂ Al ₁₄ O ₃₂ :2e ^- electronic compound bulk by in-situ reaction, and the specific steps are as follows:

1, the manufacture method of electric conductivity type Ca ₁₂ Al ₁₄ O ₃₂ : 2e ^- electronic compound, is characterized in that, comprises the following steps:

1) The CaCO ₃ powder and the Al ₂ O ₃ powder are mixed uniformly in a material ratio of 27:15, and a chemical reaction is carried out at 1450 ° C to synthesize the Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors, (The substance ratio of Ca ₁₂ Al ₁₄ O ₃₃ to Ca ₃ Al ₂ O ₆ in this precursor is 2:1), wherein the holding time is 2h.

2) The Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors prepared in step 1) and the metal Al elemental powder are prepared according to the amount of Ca ₁₂ Al ₁₄ O ₃₃ :Ca ₃ Al ₂ O ₆ :Al substance After mixing at a ratio of 2:1:1.5, mix the Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors prepared in step 1) with the metal Al elemental powder in the amount of 2:1:1.5 After mixing, mechanical alloying was carried out in an Ar gas environment for 15 min.

3) The powder after mechanical alloying in step 2) is loaded into a cemented carbide mold, pre-formed, placed in a spark plasma sintering device, and the in-situ reaction is performed to synthesize electric conductivity type Ca ₁₂ Al ₁₄ O ₃₂ ^: 2e- Electronic compound; the reaction conditions are: the sintering temperature is 950-1050° C., the pressure in the reaction chamber is 5Pa, the axial pressure is 50MPa, and the reaction time is 5min. After the reaction, a polycrystalline Ca ₁₂ Al ₁₄ O ₃₂ ^: 2e -electron compound bulk with an electron concentration of ~2.3×10 ²¹ cm ^-3 is obtained;

2. The method is used to prepare an electrical conductivity type Ca ₁₂ Al ₁₄ O ₃₂ ^: 2e -electron compound.

Among them, the model of spark plasma sintering equipment used in step 2) is SPS-5.0MK-V.

The present invention has the following characteristics:

The invention can rapidly prepare the Ca ₁₂ Al ₁₄ O ₆₄ : 2e ^- polycrystalline bulk through the spark plasma sintering process, and the electron concentration can directly reach the theoretical maximum value of ~2.3×10 ²¹ cm ^-3 , so it can be quickly and efficiently prepared The high-quality Ca ₂₄ Al ₂₈ O ₆₄ : 4e ^- block does not require the use of reducing agents, does not introduce impurities and pollution, and is a pure preparation process; the method has a simple preparation method, a short production cycle, and is easy to mass-produce .

Description of drawings

Fig. 1. The actual photo of the Ca ₁₂ Al ₁₄ O ₃₃ -Ca ₃ Al ₂ O ₆ eutectic precursor prepared in the embodiment.

Fig. 2. The actual photo of the Ca ₁₂ Al ₁₄ O ₃₂ : 2e ^- block prepared in the example.

Fig. 3. Ca ₁₂ Al ₁₄ O ₃₂ : 2e ^- polycrystalline XRD pattern prepared in Example.

Fig. 4 is a SEM photograph of the Ca ₁₂ Al ₁₄ O ₃₂ : 2e ^- polycrystalline cross-section prepared in the example.

Fig. 5. The UV-NIR absorption spectrum of Ca ₁₂ Al ₁₄ O ₃₂ : 2e ^- polycrystalline powder prepared in the example.

Detailed ways

Example 1

1) The CaCO ₃ powder and the Al ₂ O ₃ powder are mixed uniformly in a material ratio of 27:15, and a chemical reaction is carried out at 1450 ° C to synthesize the Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors, (The substance ratio of Ca ₁₂ Al ₁₄ O ₃₃ to Ca ₃ Al ₂ O ₆ in this precursor is 2:1), wherein the holding time is 2h.

2) The Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors prepared in step 1) and the metal Al elemental powder are prepared according to the amount of Ca ₁₂ Al ₁₄ O ₃₃ :Ca ₃ Al ₂ O ₆ :Al substance After mixing at a ratio of 2:1:1.5, mechanical alloying was carried out in an Ar gas environment for 15 min.

3) The powder after mechanical alloying in step 2) is loaded into a cemented carbide mold, pre-formed, placed in a spark plasma sintering device, and the in-situ reaction is performed to synthesize electric conductivity type Ca ₁₂ Al ₁₄ O ₃₂ ^: 2e- Electronic compound; the reaction conditions are: the sintering temperature is 950° C., the pressure in the reaction chamber is 5Pa, the axial pressure is 50MPa, and the reaction time is 5min. After the reaction, a polycrystalline Ca ₁₂ Al ₁₄ O ₃₂ ^: 2e -electron compound bulk with an electron concentration of ~2.3×10 ²¹ cm ^-3 is obtained;

After testing, the prepared Ca ₁₂ Al ₁₄ O ₃₂ : 2e ^- block has a relative density of 97.8% and an electron concentration of 2.3×10 ²¹ /cm ³ .

Example 2

1) The CaCO ₃ powder and the Al ₂ O ₃ powder are mixed uniformly in a material ratio of 27:15, and a chemical reaction is carried out at 1450 ° C to synthesize the Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors, (The substance ratio of Ca ₁₂ Al ₁₄ O ₃₃ to Ca ₃ Al ₂ O ₆ in this precursor is 2:1), wherein the holding time is 2h. 2) The Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors prepared in step 1) and the metal Al elemental powder are prepared according to the amount of Ca ₁₂ Al ₁₄ O ₃₃ :Ca ₃ Al ₂ O ₆ :Al substance After mixing at a ratio of 2:1:1.5, mechanical alloying was carried out in an Ar gas environment for 15 min.

3) The powder after mechanical alloying in step 2) is loaded into a cemented carbide mold, pre-formed, placed in a spark plasma sintering device, and the in-situ reaction is performed to synthesize electric conductivity type Ca ₁₂ Al ₁₄ O ₃₂ ^: 2e- Electronic compound; the reaction conditions are: the sintering temperature is 1000° C., the pressure in the reaction chamber is 5Pa, the axial pressure is 50MPa, and the reaction time is 5min. After the reaction, a polycrystalline Ca ₁₂ Al ₁₄ O ₃₂ ^: 2e -electron compound bulk with an electron concentration of ~2.3×10 ²¹ cm ^-3 is obtained;

After testing, the relative density of the prepared Ca ₁₂ Al ₁₄ O ₃₂ :2e ^- block is 98.5%, and the electron concentration is 2.3×10 ²¹ /cm ³ .

Example 3

1) The CaCO ₃ powder and the Al ₂ O ₃ powder are mixed uniformly in a material ratio of 27:15, and a chemical reaction is carried out at 1450 ° C to synthesize the Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors, (The substance ratio of Ca ₁₂ Al ₁₄ O ₃₃ to Ca ₃ Al ₂ O ₆ in this precursor is 2:1), wherein the holding time is 2h. 2) The Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors prepared in step 1) and the metal Al elemental powder are prepared according to the amount of Ca ₁₂ Al ₁₄ O ₃₃ :Ca ₃ Al ₂ O ₆ :Al substance After mixing at a ratio of 2:1:1.5, mechanical alloying was carried out in an Ar gas environment for 15 min.

3) The powder after mechanical alloying in step 2) is loaded into a cemented carbide mold, pre-formed, placed in a spark plasma sintering device, and the in-situ reaction is performed to synthesize electric conductivity type Ca ₁₂ Al ₁₄ O ₃₂ ^: 2e- Electronic compound; the reaction conditions are: the sintering temperature is 1050° C., the pressure in the reaction chamber is 5Pa, the axial pressure is 50MPa, and the reaction time is 5min. After the reaction, a polycrystalline Ca ₁₂ Al ₁₄ O ₃₂ ^: 2e -electron compound bulk with an electron concentration of ~2.3×10 ²¹ cm ^-3 is obtained;

After testing, the prepared Ca ₁₂ Al ₁₄ O ₃₂ : 2e ^- block has a relative density of 99.8% and an electron concentration of 2.3×10 ²¹ /cm ³ .

Claims (1)

1. the manufacture method of electric conductivity type polycrystalline Ca ₁₂ Al ₁₄ O ₃₂ : 2e ^- electronic compound bulk, is characterized in that, comprises the following steps: 1) The CaCO ₃ powder and the Al ₂ O ₃ powder are mixed uniformly in a material ratio of 27:15, and a chemical reaction is carried out at 1450 ° C to synthesize the Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors, The material ratio of Ca ₁₂ Al ₁₄ O ₃₃ to Ca ₃ Al ₂ O ₆ in this precursor is 2:1, and the holding time is 2h; 2) The Ca ₁₂ Al ₁₄ O ₃₃ and Ca ₃ Al ₂ O ₆ eutectic precursors prepared in step 1) and the metal Al elemental powder are prepared according to the amount of Ca ₁₂ Al ₁₄ O ₃₃ :Ca ₃ Al ₂ O ₆ :Al substance After mixing at a ratio of 2:1:1.5, mechanical alloying was carried out in an Ar gas environment for 15 minutes; 3) The powder after mechanical alloying in step 2) is loaded into a cemented carbide mold, pre-pressed and formed, placed in a spark plasma sintering device, and the in-situ reaction is performed to synthesize electric conductivity type polycrystalline Ca ₁₂ Al ₁₄ O ₃₂ : 2e ^- Electronic compound block; reaction conditions are: sintering temperature is 950-1050°C, reaction chamber pressure is 1-5Pa, axial pressure is 50MPa, and reaction time is 5min.

Images