Preparation of reformed MgO filler with high humidity resistance by a hydrothermal coating technique.

Figures & data

Figure 1. SEM photographs of the starting MgO (RF-98)

Figure 2. TG curves of Mg(OH)₂ (brucite), 4MgCO₃-Mg(OH)₂-4H₂O (hydromagnesite), and MgCO₃ (magnesite)

Table 1. Summary of the reaction results in the water

RunNo.	Solvent	Temperature(°C)	CO2 pressure(MPa)	Reaction products (wt%)				Amount of magnesite (%)*
				magnesite	hydromagensite	brucite	Total
1	water	30	5	5.1	19.5	4.9	29.5	17.3
2	water	120	5	46.7	9.2	3.5	59.4	78.6
3	water	175	5	33.4	3.2	1.6	38.2	87.4
4	water	120	1	2.2	19.6	9.1	30.9	7.1
5	water	175	1	33.9	6.1	4.2	44.2	76.7
6	water	175	5**	60.6	2.5	3	66.1	91.7

*: Amount of magnesite among the total reaction products

**: CO₂ gas was suppled after the temperature reached 175°C.

Figure 3. SEM photographs of each product in Table 1. (bar = 5 µm)

Figure 4. SEM photographs of the reaction products obtained by stopping the reaction at 80°C. (bar = 50 µm). (b). heating rate at 5°C/min, (b) heating rate at 2.5°C/min

Table 2. Summary of the reaction results with the addition of ethanol

RunNo.	Solvent	Temperature(°C)	CO2 pressure(MPa)	Reaction products (wt%)				Amount of magnesite (%)*
				magnesite	hydromagensite	brucite	Total
7	EtOH 80 wt%	30	5	0.7	0.5	0.2	1.4	50.0
8	EtOH 80 wt%	120	5	7.9	3.1	0.7	11.7	67.5
9	EtOH 80 wt%	175	1	4.6	1.1	0.7	6.4	71.9
10	EtOH 80 wt%	175	5	5.2	1.2	0.1	6.7	77.6
11	EtOH 50 wt%	175	5	12.5	1.4	0.7	14.6	85.6
12	NMP 80 wt%	175	5	4.4	0.6	0.2	5.2	84.6

*: Amount of magnesite among the total reaction products.

Figure 5. SEM photographs of each product in Table 2. (bar = 1 µm)

Figure 6. Cross-sections of the MgO particles reformed at 175°C in 50 wt% ethanol (a), and 80 wt% ethanol (b)

Figure 7. Surface photographs of the PPS plates after humidity resistance test. PPS plates include unreformed MgO(a), reformed MgO with 10 wt% magnesite (b) and 30 wt% magnesite (c)