Carbon-coated magnetic superfine iron particle and its manufacturing method

[0030] Example 1

[0031] Weigh 5g of sodium chloride and 5g of ferric oxide with an average particle size of 10nm, add 80g of steel balls with a diameter of 6mm, and dry them for 24 hours at a speed of 300 r/min, weigh 1g of ball-milled sodium chloride and The mixture of ferric oxide is laid flat on the bottom of the ark and placed in the constant temperature zone of the tubular reaction furnace. The outlet of the reaction furnace is at normal pressure. After 30 min of hydrogen with a flow rate of 30 ml/min, the temperature starts to rise, and the temperature rises at a rate of 20 °C/min. , control the temperature at 600 ℃, and reduce the reaction for 2hr. The hydrogen flow rate was adjusted to 5ml/min to reduce the temperature to 450°C, 100ml/min of nitrogen gas and 10ml/min of acetylene gas were introduced, the coating reaction was performed for 30min, the nitrogen and acetylene were turned off, and the temperature was lowered to room temperature under the protection of hydrogen, and the product was used up Washing with ionized water (until silver nitrate is added to the washing water without precipitation), and drying to obtain carbon-coated magnetic ultrafine iron particles.

[0032]According to the electron microscope analysis, the product is granular (see Figure 1), the particle size is less than 500nm, of which 200-500nm accounts for 70-80%, and the particles smaller than 200nm are about 20%; the vibration sample magnetometer tests its specific saturation magnetic strength 147emu/g , the residual magnetization is 1.9emu/g, and the saturation magnetization is 141emu/g after the product is placed for three months; the thermogravimetric balance (TG) analysis and test its anti-oxidation temperature is 410 ℃; X-ray diffraction test (see Figure 2) shows that The iron in the product exists in the α-Fe phase, and contains trace amounts of iron sulfide and iron oxide, of which the α-Fe content is 72%. The coated carbon has no obvious characteristic peaks in the X-ray spectrum, indicating that the coated carbon is amorphous carbon. exists, its content is 28%.

[0033] Example 2

[0034] Ball milling and reduction are with embodiment 1, and difference is that reduction reaction temperature is 500 ℃, and isolating agent is potassium chloride; carbon coating reaction condition is the same as embodiment 1, and difference is that carbon source acetylene is changed into each 50% of ethanol and acetylene ( Volume ratio).

[0035] According to the electron microscope analysis, the product is granular (see Figure 3), and the particle size of the product is mainly 20-300 nm; the vibration sample magnetometer tests its specific saturation magnetic strength of 143 emu/g and residual magnetization of 1.37 emu/g. After one month, the specific saturation magnetization was tested to be 139emu/g; the thermogravimetric balance (TG) analysis and test showed that the oxidation resistance temperature was 420°C; Trace amounts of iron sulfide and iron oxide, of which the α-Fe content is 71%, the coating layer carbon has no obvious characteristic peaks in the X-ray spectrum, indicating that the coating layer carbon exists as amorphous carbon, and its content is 29%.