The 1.5‐ to 3‐mol%‐Y2O3‐stabilized tetragonal ZrO2 (Y‐TZP) and Al2O3/Y‐TZP nanocomposite ceramics with 1 to 5 wt% of alumina were produced by a colloidal technique and low‐temperature sintering. The ...influence of the ceramic processing conditions, resulting density, microstructure, and the alumina content on the hardness and toughness were determined. The densification of the zirconia (Y‐TZP) ceramic at low temperatures was possible only when a highly uniform packing of the nanoaggregates was achieved in the green compacts. The bulk nanostructured 3‐mol%‐yttria‐stabilized zirconia ceramic with an average grain size of 112 nm was shown to reach a hardness of 12.2 GPa and a fracture toughness of 9.3 MPa·m1/2. The addition of alumina allowed the sintering process to be intensified. A nanograined bulk alumina/zirconia composite ceramic with an average grain size of 94 nm was obtained, and the hardness increased to 16.2 GPa. Nanograined tetragonal zirconia ceramics with a reduced yttria‐stabilizer content were shown to reach fracture toughnesses between 12.6–14.8 MPa·m1/2 (2Y‐TZP) and 11.9–13.9 MPa·m1/2 (1.5Y‐TZP).
CeCl3·7H2O and GdCl3·6H2O that were dissolved in water were precipitated with urea (NH2CONH2) to produce matrix agglomerates for three‐component nano‐reactors. Mixing hexamethylenetetramine with ...dilute nitric acid resulted in the formation of well‐dispersed nano‐particles of cyclotrimetilene trinitramine (C3H6N6O6) (RDX) in the solvent. Nano‐reactors were produced by impregnating the nano‐C3H6N6O6 into the matrix agglomerates of an intermediate complex of cerium and gadolinium compounds. Blast initiation of the C3H6N6O6 resulted in extremely rapid detonation and gaseous products formation at temperatures of 2000°–5000°C, which were compressed into a volume nearly equal to the initial volume of each RDX nano‐particle. Multiple “nano‐blasts” occurred in the volume of each nano‐reactor. The impact of the blast waves led to fragmentation of the surrounding matter. The evolution of a large volume of gaseous products dissipated the heat of the process and limited temperature increase, thus reducing the possibility of local sintering among the primary particles. The short‐term high temperature generated during the blasts enhanced the solid solubility of the metal oxides. Uniform aggregates of 22∼74 nm consisting of 6∼14 nm crystallites of gadolinia in ceria solid solution were synthesized.
Here we demonstrate a unique processing technique which is based on engineering multi-component ceramic nanopowders and composites with precise morphology by nano-explosive ...deagglomeration/calcination. Multiple nano-explosions of impregnated cyclotrimethylene trinitramine deagglomerate the nanopowder due to the highly energetic impacts of the blast waves, while the solid-solubility of one component into the other is enhanced by the extremely high local temperature generated during the nano-explosions. We applied this technique to produce nanosize agglomerate-free ceria–gadolinia solid solution powder with uniform morphology and an average aggregate size of 32
nm, and 8
mol% yttria-doped zirconia aggregates with an average size of 53
nm impregnated with platinum (2–14
nm).
A uniformly aggregated 3 mol% yttria‐stabilized tetragonal zirconia nano‐powder (3Y‐TZP) was prepared using thermal hydrolysis and the ultrasonic deagglomeration technique. The possibility of ...nano‐engineering of Pt–3Y‐TZP composite aggregates was studied. The as‐synthesized Pt nano‐particles (∼2 nm) were impregnated into zirconia nano‐aggregates (20–45 nm). The morphology manipulation technique allowed production of the composite zirconia‐based aggregates in which a significant fraction of the Pt particles was embedded into the densified zirconia aggregates. Using the colloidal technique and low‐temperature (1150°C) sintering, we prepared the Pt‐zirconia (0.5–1.5 wt% of platinum) nano‐composites with average 3Y‐TZP grain sizes of 120 nm, and with the platinum grains size in the range of 20–60 nm. The catalytic properties of composite Pt–3Y‐TZP nano‐composites were studied and described.
We demonstrate a processing technique based on the synthesis of ceramic nanopowders and simultaneous impregnation with metallic nanoparticles by multiple 'nano-blasts' of embeded cyclotrimethylene ...trinitramine in preliminary engineered multi-component nano-reactors. 'Nano-blasts' of impregnated cyclotrimethylene trinitramine deagglomerate the nanopowder due to the high energetic impacts of the blast waves, while the decomposition of compounds and their solid-solubility is enhanced by the extremely high local temperature generated during the nano-explosions. We applied this technique to produce nanosized agglomerate-free 8 mol% yttria-doped cubic zirconia aggregates with an average size of 53 nm impregnated with 10 mass% of platinum particles of 2-14 nm.
Three different methods of synthesis of ceria-gadolinia (CGO) nanopowders are presented. We established a technique of the synthesis of uniformly aggregated, agglomerate-free CGO in which ...ceria-gadolinia composite nano-aggregates (15-40 nm) are prepared by nucleation and crystallization of ceria on the surface of preliminary synthesized, hydrolyzed and ultrasonically de-agglomerated gadolinia (3-17 nm). Nano-size aggregates (12-65 nm) of CGO were produced during subsequent non-isothermal calcination. The incorporation of the small concentrations of gadolinia in the ceria lattice was studied using the electron spin resonance technique. It was confirmed that Gd3+ occupies the sites of both cubic and axial symmetry. With increasing concentration, Gd3+ forms a defect complex with the oxygen vacancy.
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