Microstructural and thermal investigations of HfO2 nanoparticles

Fast, microwave-assisted synthesis of monodisperse HfO2 nanoparticles

“…However, most of these methods are unfavorable because of a long reaction time, a broad size distribution, the agglomerated state of the particles or the large diameter. In addition, there is often need for a second calcination step to crystallize the particles which aggravates agglomeration (Chaubey et al 2012;Boyle et al 2012;. Some synthesis methods (Dahal and Chikan 2012;Tang et al 2004) yield unagglomerated and crystalline (sub 10 nm) particles but have the drawback that they use large quantities of surfactants and expensive precursors.…”

“…Even the use in biological applications should not be excluded because of the negligible cytotoxicity of HfO2 (Field et al 2011). Hafnium oxide nanoparticles have already been synthesized with a variety of methods, such as surfactant based (Dahal and Chikan 2012;Tang et al 2004;Chaubey et al 2012;Tirosh and Markovich 2007), hydrothermal (Stefanic et al 2005), microwave assisted hydrothermal (Eliziario et al 2009), ultrasonically assisted hydrothermal (Meskin et al 2007), solvothermal (Pinna et al 2004;Pucci et al 2009;Boyle et al 2012;Buha et al 2010), precipitation ) and sonochemical synthesis . However, most of these methods are unfavorable because of a long reaction time, a broad size distribution, the agglomerated state of the particles or the large diameter.…”

Oxide or carbide nanoparticles synthesized by laser ablation of a bulk Hf target in liquids and their structural, optical, and dielectric properties

“…The most common traditional methods of synthesis of hafnia nanoparticles in solution, involve the reaction of hafnium(IV) ethoxide with benzyl alcohol [7], the reaction of hafnium tetrachloride (HfCl 4 ) with potassium hydroxide (KOH) and 3,4-dihydroxy hydrocinnamic acid (DHCA) [8] or just with sodium hydroxide (NaOH) [9], the reaction of hafnium (IV) isopropoxide with HfCl 4 and trioctylphosphine oxide (TOPO) as the strongly coordinating solvent [10] or the reaction of hafnium(IV) tert-butoxide with ammonia (NH 4 OH) in the presence of surfactant [11]. These methods require long reaction times and high temperatures [7,8,10], annealing at usually high temperatures under controlled gas atmospheres of the as synthesized originally amorphous nanoparticles in order to crystallize them [9,11] or vigorous washing procedures in order to remove from the nanoparticles' surfaces the coordinating ligands (such as for instance TOPO) which are used during their synthesis [10].…”

“…These methods require long reaction times and high temperatures [7,8,10], annealing at usually high temperatures under controlled gas atmospheres of the as synthesized originally amorphous nanoparticles in order to crystallize them [9,11] or vigorous washing procedures in order to remove from the nanoparticles' surfaces the coordinating ligands (such as for instance TOPO) which are used during their synthesis [10].…”

“…It has attracted investigations in recent years for ultra-high temperature applications such as in cutting tools, rocket nozzles, space/air craft and thermal-field emitters [12]. It is usually synthesized by the reaction of powder mixtures of some source of carbon such as phenolic resin, citric acid monohydrate, graphite powder and others, with some source of Hf such as pure Hf metal, Hf hydride (HfH 2 ), hafnia or HfCl 4 [11][12][13][14][15].…”