Wavelength Multiplexing of Microsphere Resonators Used to Characterize Nanolayers
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method. While the average bending strength of the untreated alloy was 245 MPa, the average bending strength of the alloy treated with the magnetic field was 430 MPa, roughly a 75% increase. The elastic modulus remained unchanged. Scanning electron microscopy observations of the fracture surfaces of the treated specimens showed typical ductile fracture characteristics. The fracture surfaces of the untreated specimens clearly showed brittle characteristics with microcracks, the researchers reported. In order to understand the underlying mechanism, C.W. Wu in the Department of Mechanical Engineering at Dalian said that the research group performed electron probe microanalysis on the untreated and treated samples. The untreated alloy consists of NiAl, Cr(Mo), and Heusler phases. These do not change when the alloy is heated to 900ºC. In the magneticfield-treated samples, the Heusler phases at the NiAl/Cr(Mo) grain boundaries were partly dissolved into the NiAl and Cr(Mo) phases. In addition, small Heusler phase particles at the Cr(Mo) and matrix phase interfaces partially dissolved into the NiAl matrix (see Figure 1). The researchers speculated that the dissolution of the Heusler phase due to the highmagnetic-field treatment contributed to the improvement in bending strength and ductility of the alloy. The exact mechanism, however, remains unclear. GOPAL RAO
Metalorganic Building Block Enables Synthesis of Four Supramolecular Isomers While supramolecular isomerism is widely encountered in the field of crystal engineering, the majority of these that have been reported require a co-existence of different guest components for production. An elementary system of supramolecular isomers that has been encountered is the zero-dimensional ring-like, one-dimensional zigzag, and helical chains that can be derived from a stoichiometry of 1:1 metal/ligand molar ratio. Now, X.-M. Chen and colleagues from Sun Yat-Sen University in China have fabricated low-dimensional supramolecular isomerism (chairs, zippers, and chains) of 0D/1D coordination polymers without the use of guest components. By using a binary Cu +1 triazolate [Cu+1(2-Hpytz)]x (2-Hpytz = 3,5-di-(2pyridyl)-1,2,4-triazolate) pre-designed, metalorganic building block, the researchers isolated four types of air-stable crystals of different colors and/or shapes. Crystallographic studies revealed the stoichiometry of 1:1 (metal/ligand) for all 264
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Figure 1. ORTEP drawing (50% A: 0.5 – y, x – 0.5, z – 0.25) of a single 41 helix in Complex IV (a). Top (b) and side (c) views of two adjacent helical chains in space-filling modes. ORTEP stands for Oak Ridge thermal-ellipsoid plot program. Reproduced with permission from Chemical Communications (2005), p. 1258; DOI: 10.1039/b416095a. © 2005 Royal Society of Chemistry.
complexes isolated. The researchers’ findings were reported in the March 1 issue of Chemical Communications (p. 1258; DOI: 10.1039/b416095a). The different complexes were synthesized based on the different conformations of the coordinating ligands. Complex I
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