You will be shown an abstract from a materials science research paper. Your task is to extract all synthesis operations described in the abstract into a structured JSON format. Your output should be a JSON array. Each entry in the array should be a JSON object describing a single synthesis operation. This object should have the following fields:

- "trigger": A verbal predicate indicating a synthesis operation. This should be a string extracted directly from the abstract.
- "arguments": An array of arguments specifying aspects of the synthesis operation. Each entry in the array should be a length-2 array formatted as [<argument_text>, <argument_type>]. The `argument_text` should be a string extracted directly from the abstract. The `argument_type` should be one of the following types: ["Recipe_Precursor", "Atmospheric_Material", "Participant_Material", "Recipe_Target", "Solvent_Material"].

For instance, suppose an excerpt from the abstract reads:

Tetraethoxysilane (TEOS, 98%) and cetyltrimethylammonium bromide (CTAB, 98%) were purchased from Fluka. The MTTZ-siloxy derivative (triethoxysilyl-propyl-5-mercapto-1-methyl-tetrazole) was synthesized as previously described [38].

This excerpt includes two operations, which could be annotated as follows.

[{"arguments": [["Tetraethoxysilane", "Recipe_Precursor"], ["cetyltrimethylammonium bromide", "Recipe_Precursor"]], "trigger": "purchased"}, {"arguments": [["MTTZ-siloxy derivative", "Recipe_Target"]], "trigger": "synthesized"}]

In your response, please include the JSON and no other text.

Abstract:
10.1016/j.electacta.2014.12.157
Synthesis and electrochemical performance of ZnCo2O4 for lithium-ion battery application


All of the chemicals in our synthesis were analytical grade and were used without further purification. In a typical procedure, zinc acetate dihydrate and cobalt (II) acetate tetrahydrate with a Zn/Co molar ratio of 1:2 were added to a ball mill. Citric acid with a 120% mole fraction relative to the Zn and Co was then added into the ball mill. After adding a suitable volume of water, the ball mill was run for 4 h at 500 rpm to obtain the precursor. Then, the resultant mixture was dried at 80 degC in air, and the wine red precursor powder was collected and heat-treated in a muffle furnace at 400 degC and 500 degC, with the products designated as 400-ZCO and 500-ZCO, respectively.
[{"arguments": [["chemicals", "Participant_Material"]], "trigger": "used"}, {"arguments": [["zinc acetate dihydrate", "Recipe_Precursor"], ["cobalt (II) acetate tetrahydrate", "Recipe_Precursor"]], "trigger": "added"}, {"arguments": [["Citric acid", "Participant_Material"]], "trigger": "added"}, {"arguments": [["water", "Solvent_Material"]], "trigger": "adding"}, {"arguments": [["precursor", "Participant_Material"]], "trigger": "run"}, {"arguments": [["mixture", "Participant_Material"], ["air", "Atmospheric_Material"]], "trigger": "dried"}, {"arguments": [["powder", "Participant_Material"]], "trigger": "collected"}]