Generation of Ultrafine Particles by Spark Discharging

Figures & data

FIG. 1 Schematics of the spark generator (with permission of L. Mölter, PALAS, Karlsruhe, Germany).

FIG. 2 Set-up for determining particle size distributions and number concentrations.

FIG. 3 Dependence of the modal diameters of ultrafine aerosols on the discharge frequency for operation parameters shown in Table 1.

FIG. 4 Size distributions of ultrafine aerosols generated for operation parameters listed in Table 1.

TABLE 1 Characteristics of ultrafine aerosols generated for various operation parameters of the generator

	Operation conditions				Particle characteristics			Mass-related surface area		Volume-related surface area
Particle material	(Discharge frequency Hz)	Argon flow rate (lpm)	Nitrogen flow rate (lpm)	Air flow rate (lpm)	Modal diameter (nm)	Number concentration (cm^−3)	Mass concentration (μg m^−3)	BETm (m^2 g^−1)	ASAm (m^2 g^−1)	BETv (m^2 cm^−3)	ASAv (m^2 cm^−3)
Carbon	3	6.3	17	170	25	10^6	25	750	47	1425	90
Carbon	300	6.3	17	125	70	10^7	115	750	17	1425	32
Carbon	300	6.3	0	125	150	n.a.	n.a.	n.a.	n.a.	n.a.	n.a.
Silver	300	3.5	0	125	20	3 × 10^6	133	20	11	210	115
Iridium	140	6.3	0	125	18	2.5 × 10^6	83	n.a.	n.a.	n.a.	n.a.
Iridium	500	6.3	0	125	22	3 × 10^7	480	123	5.1	2766	102
Ferric oxide	20	5.4	17	165	35	10^6	40	300	10	1560	57
Cadmium oxide	6	3.5	17	165	35	10^6	65	50	9.2	408	75
Cadmium oxide	300	3.5	17	125	50	8 × 10^6	420	n.a.	n.a.	n.a.	n.a.

FIG. 5 Size distribution of a carbon aerosol of 10⁷ cm^{− 3} number concentration at the inlet and outlet of the exposure chamber.

FIG. 6 Micrographs of ultrafine particles: (a) silver particles, (b) cadmium oxide particles, (c) iron oxide particles, (d) iridium particles, and (e) carbon particles. (Continued)

FIG. 7 Surface areas of ultrafine particles of different modal diameter and composition.