Particle generation by cosolvent spray pyrolysis: Effects of ethanol and ethylene glycol
- PDF / 791,001 Bytes
- 11 Pages / 584.957 x 782.986 pts Page_size
- 57 Downloads / 181 Views
Howard Glicksman Department of Microcircuit Materials, DuPont Electronic Technologies, Research Triangle Park, North Carolina 27709
Sheryl Ehrmana) Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742 (Received 27 March 2012; accepted 29 June 2012)
A cosolvent spray pyrolysis process was used for the generation of micrometer-sized pure copper particles. Ethylene glycol (EG) and ethanol (ET) were selected as cosolvents, and their effects on particle morphology and composition were systematically investigated. Experimental results showed that oxide-free copper particles could be generated at temperatures greater than 400 °C with either cosolvent. Hollow particles with cracks were generated with ET at temperatures from 400 to 1000 °C, whereas EG promoted the formation of porous particles at temperatures up to 600 °C and hollow shell particles with smooth surfaces at 875 and 1000 °C. Results from short residence time experiments indicated that, during the generation process, lamellar and fragment-like copper hydroxy nitrate [Cu2(OH)3NO3] precipitated when EG and ET were used respectively. Cu2(OH)3NO3 then decomposed to cupric oxide (CuO) and cuprous oxide (Cu2O). Finally the oxides were reduced to copper (Cu) in the reducing atmosphere created by EG and ET.
I. INTRODUCTION
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.248
micrometers by adjusting the salt concentration in the precursor. In addition, temperature and carrier gas flow rate are two important operating parameters for the control of particle morphology.20 To achieve the desired conductivity and product reliability, copper particles free of copper oxide are required. To produce oxide-free particles using spray pyrolysis, a reducing environment is required to prevent the formation of a stable oxide.21–24 Use of 10 vol% hydrogen was reported for copper nanoparticle generation, but hydrogen with a concentration from 4 to 75 vol% (in air at 1 atm) leads to a risk of explosion.25 In 2003, Kim et al. reported the generation of copper nanoparticles using N2 as a carrier gas and ethanol (ET) as a cosolvent.26 Under the reported conditions, the ET decomposes providing a reducing environment.27–30 The flash point of ET is 14 °C, however, which makes ET a National Fire Protection Association (NFPA) class 3 flammable material. For industrial applications, use of materials that have a flash point above 100 °C is preferred. Ethylene glycol (EG) has a flash point of 111 °C,31 and is NFPA class 1 flammable material requiring preheating before ignition.32 In this work, we report generation of micrometer-sized copper particles with either EG or ET at different temperatures. The effects of the cosolvent and temperature on particle morphology and composition were monitored, and the reaction process was investigated.
2540
Ó Materials Research Society 2012
Micrometer- and submicrometer-sized copper particles are used in electromagnetic interference packaging,1 in electronically conductive paste
Data Loading...
