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The search for suitable synthesis methods and parameters capable of controlling the length, diameter, and yield of silver nanowires (AgNWs) is still an emerging strategy today. Therefore, a method for high-yield synthesis of long AgNWs via chromic chloride and a stable reaction environment was proposed. The results show that Cr3+ could restore the adsorbed atomic oxygen quickly and provide a high efficiency in the prevention of the oxidative etching, for the ion of Cr2+ oxidized to Cr3+ has a lower standard electrode potential, and a more stable reaction environment provided by the coupling method could avoid disturbing the growth of the {111} reactive sites of the wires; then, the yield and length of the AgNWs were improved. The length of the AgNWs was over 75 μm and even 160 μm; the yield of the AgNWs was over 90%, which provides the referable basis for the synthesis of ultralong AgNWs.

(NH4)2RuCl6is an important precursor in the synthesis of Ru powder with high-purity requirement. In this study, high-purity (>99.999 wt%) micro-sized (NH4)2RuCl6pieces were synthesized by distillation and precipitation from crude Ru powder. Then, the thermal decomposition behavior of the (NH4)2RuCl6pieces was investigated. The decomposition process included two stages. First, (NH4)2RuCl6was decomposed from 255.0°C to 314.0°C, with the endothermic peak located at 309.4°C. At this stage, HCl and NH3were released, while the dense micro-pieces were transformed to loosened micro-pieces due to the thermal decomposition. Then, the solid phase [(NH3)4Ru3Cl12] kept decomposing from 314.0°C to 352.7°C, HCl and N2were released, and agglomerated Ru particles were achieved. Thermogravimetric analysis-differential thermal analysis-mass spectrum coupling (TG-DTA-MS) was used to monitor the thermal decomposition process and identify the released gaseous phases, respectively. The solid phases in different stages were characterized by high-temperature X-ray diffraction (HTXRD). A good understanding of the processing and thermal decomposition of (NH4)2RuCl6is crucial in the creation of Ru products.

(NH 4 ) 2 RuCl 6 is one of the most important precursors for the preparation of Ru powder with high-purity requirement. In this study, high-purity (> 99.999 wt%) micro-spherical (from 2.3 to 10.4 μm) (NH 4 ) 2 RuCl 6 particles with controllable surface were synthesized by chemical separation method combined with spray drying process. After the chemical separation, high-purity (NH 4 ) 2 RuCl 6 precipitation was achieved, while the morphology, size and surface of (NH 4 ) 2 RuCl 6 particles were controlled by the spray drying process. The detailed influencing mechanisms of spray drying process, including gas/liquid rate, drying temperature and solution concentration, were investigated. Both gas/liquid rate and drying temperature influence the morphology and size of spray dried particles, while solution concentration is directly proportional to size of spray dried particles. It should be noted that the powder technology in this study could be applied to synthesize other high-purity spherical particles.

Nanoscale tungsten (W) powder is used in some special materials. In this study, a hollow superstructure W powder consisting of nanoparticles was synthesized by spray drying combined with two-step calcination from commercial (NH4)6W7O24·6H2O. The high-pressure gas (HPG) was the significant factor in spray drying process, which affect the BET surface area and average particles size of the spray-dried powders. The detailed influences of calcined steps and calcination temperature in the microstructure and average particles size of final W particles were investigated. The size distribution of as-synthesized nanoscale W particles with hollow superstructure was from 40 to 200 nm, and the average size was about 100 nm. The as-synthesized W powder shows good sintering properties. It should be noted that the powder technology in this study can be used to synthesize other powders with high-performance requirements. Graphical abstract .