A versatile solution-phase, precursor route to surface-mazelike hierarchical structures

In this work, surface-mazelike Zn O, Cu, and Ni hierarchical structures were synthesized via a versatile ethylene glycol- mediated solvothermal method. The structure evolution of these materials bore striking similarities, including(1) initial formation of metal alkoxides precursors and(2) subsequent structural evolution of products from tiered plates to jigsaw puzzles; then to extrusion ridges, nests and spindles; and thereafter to final mazelike structures driven by persistent thermal decomposition of preformed precursors. Based on their unique surface morphologies in sinuous asymmetry, it is anticipated that such mazelike hierarchical structures may shed new light on the development of morphology-controlled adsorption and heterogeneous catalysts.

Precursor route synthesis and thermal contraction of compounds ZrW_(2-x)Mo_xO_8 (x=0, 0.4, 0.6, 0.8, 1.2, 1.6)

A series of title compounds as well as their precursors were synthesized by precursor route. Their PXRD patterns were characterized with ZrW2O8 or ZrMo2O8 model by Rietveld method. The thermal contractions of the compounds were determined according to the variable-temperature PXRD data and NTE coefficients were presented. The two-phase mixture of ZrW0.4Mo1.6O8 was also analyzed individually.

A New Orthorhombic Phase of ZrW_(1.6) Mo_(0.4)O_8 at Ambient Pressure

Nanocrystallite δ ′ ZrW 1.6 Mo 0.4 O 8 was prepared in the precursor route synthesis. The characterization by means of powder X ray diffraction (XRD) and selected area electron diffraction (SAED) showed it crystallized in a orthorhombic crystal system with a =0.896 9(7) nm, b =0.701 1(8) nm, c =0.596(1) nm. The possible space group is Pnnm (58) or Pnn2 (34). The compound crystallizes in a metastable phase during the synthesis process depending on temperature and crystallization time.

o-ZrW_(1.6)Mo_(0.4)O_8:A Novel Orthorhombic Intermediate Phase Formed During the Synthesis of the Negative Thermal Expansion Cubic ZrW_(1.6)Mo_(0.4)O_8 Material by the Precursor Dehydration Route

The mechanism of the precursor dehydration route was revealed for the synthesis of NTE c-ZrW_ 1.6 Mo_ 0.4 O_8. The hydrate precursor was dehydrated at 473 K and transformed to a NTE cubic compound above 800 K. A novel intermediate phase o-ZrW_ 1.6 Mo_ 0.4 O_8 occurs between the temperature range of 573—800 K. The XRD pattern of novel intermediate was refined with the structural model of LT-ZrMo_2O_8 by using Rietveld method. The residuals are R_ wp =7.80% and R_p=5.79%. The space group is Pmn2_1 and the lattice parameters are a=0.5917(4) nm, b=0.7273(4) nm, c=0.9148(6) nm, and Z=2.

A Novel Method to Fabricate Steel-Al Foam Sandwich Panel with Metallic Bonding

Al foam sandwich panel(AFS) with metallic bonding was fabricated by foaming a hotpressed three-layer composite with two steel facesheets and a melt route precursor as core. The melt route precursor was fabricated by dispersing undecomposed blowing agent into molten Al, followed by solidification. Microstructures of the joints during fabrication process were analyzed by scanning electron microscopy(SEM) and energy dispersive spectroscopy(EDS). Static three-point bending was conducted to evaluate joint quality of the AFS. It was found that a primary bonding was achieved by hot-pressing and significant diffusion layer of Fe-Al intermetallic compounds was sustained between steel and Al foam core by foaming. Damage modes of the AFS under three-point bending were dominated by indentation, plastic hinges, core shear and crack. Delamination between steel and foam was absent, implying that reliable metallic bonding was achieved. This method allows for producing large-scale AFS with steel facesheets.