Purification and Functionalization of Diamond Nanopowders
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1203-J17-52
Purification and Functionalization of Diamond Nanopowders Jong-Kwan Lim and Jong-Beom Baek School of Energy Engineering Ulsan National Institute of Science and Technology (UNIST), 100, Banyeon, Ulsan, 689-805 South Korea ABSTRACT Purification of diamond nanopowder (DNP) was conducted in a less-destructive mild polyphosphoric acid (PPA)/phosphorous pentoxide (P2O5). The wide-angle X-ray diffraction (XRD) showed that the intensity of the characteristic diamond d-spacing (111) at 2.07 Ǻ from purified DNP (PDNP) was fairly increased compared to pristine DNP, indicating that significant amount of carbonaceous impurities were removed. Chemical modification of pristine DNP and PDNP with 4-ethylbenzoic acid was carried out to afford 4-ethylbenzoyl-functionalized DNP (EBA-g-DNP) and PDNP (EBA-g-PDNP). The morphologies of EBA-g-DNP and EBA-g-PDNP from scanning electron microscopy (SEM) were further affirmed the feasibility of chemical modification. The results suggested that the reaction condition was indeed viable for the one-pot purification and functionalization of DNP. The resultant functionalized DNP could be useful for nanoscale additives. Hence, EBA-g-DNP and EBA-g-PDNP was brominated by using Nbromosuccinimide (NBS). The resultant α-brominated DNP and PDNP could be used as initiator for the atom transfer radical polymerization (ATRP) to introduce many polymers onto the surface of functionalized DNP and PDNP. 1. INTRODUCTION Carbon nanomaterials have received a great deal of attention since the discovery of the C 60 fullerene molecule [1] and the carbon nanotube [2]. Three-dimensional, carbon-based, nanostructured materials are generally various: (i) fullerene (0.7~3 nm); (ii) carbon nanopowders (≤30 nm); (iii) diamond nanopowders (3.2 nm). Amongst them, diamond nanopowders (DNP) are worth of investigating due to relatively new and thus less studied. DNP has unique properties such as highest hardness, highest thermal conductivity, low thermal expansion coefficient and low friction coefficient. DNP is generally produced by chemical vapor deposition (CVD), detonation and spark plasma sintering method [3]. Metal catalysts are generally necessary to activate materials (DNP: ≥95% trace metals basis). In consequence, DNP from those methods contains impurities such as metal catalyst particles, amorphous carbon and carbon nanoparticles. Therefore, DNP may have limited applications because it contains impurities. Lately, many purification methods have been reported to remove impurities from carbon soot [4,5]. For example, they are oxidation, thermal annealing, thermal oxidation, ultra-sonication, strong acid treatments and so on. Recently, less-destructive method for both purification and chemical modification of various carbon nanomaterials in a mild polyphosphoric acid (PPA)/phosphorous pentoxide (P2O5) medium have been developed [6]. Hence, as-received DNP was treated in PPA/ P2O5 to selectively remove persisting impurities. In the same purification condition, DNP and purified DNP (PDNP) were functionalized as f
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