Synthesis Of PMN Research Articles

The Mechano-Chemical Synthesis and Characteristics of PMN and PZT

Both PMN and PZT are perovskite oxides and typical functional materials applicable to various devices for its chemistry and physics properties. The conventional method solid-state reaction method has some drawbacks of high reaction temperature, large particle size and limited degree of chemical homogeneity. So, an easy, low cost and environmental method of synthesizing fine and homogenous powders is required. This paper discusses the synthesis of PMN and PZT by the new mechano-chemical method, the screw grinding method. Through experiments, it was found that the mechanism of mechano-chemical method and solid phase diffusion method were completely different, thus the pyrochlore phase was avoided, and the phase purity of powders was developed. And a higher power could greatly short the time of the mechano-chemical reaction time, improving the phase purity and the dispersion of the powder.

Abstract 5650: Interactions Between the Endogenous NO Synthase Inhibitor Asymmetric Dimethylarginine and the Leukocyte-derived Hemoprotein Myeloperoxidase

Background: ADMA and the NO oxidizing leukocyte-derived hemoprotein MPO are associated with cardiovascular diseases. ADMA and MPO per se coincide with increased oxidative stress and induction of inflammatory responses. Furthermore, the enzymes responsible for ADMA homeostasis (i.e. dimethylarginine dimethylaminohydrolase, DDAH) are regulated in a redox-sensitive fashion. Therefore, the aim of the study was to investigate whether there is an interaction between ADMA and MPO resulting in increased leukocyte (PMN) activation and reduced NO bioavailability. Methods: To test a direct leukocyte activating effect of ADMA, isolated human PMN were subjected to ADMA, SDMA, and fMLP -an inductor of NADPH oxidase activity- to determine PMN degranulation (MPO activity, MPO and elastase levels) and leukocyte superoxide production. NO synthase and DDAH activity was measured by GC-MS and LC-MS/MS, respectively. In vivo, the effect of chronic ADMA (250 μ mol/kg/d; 28 days) treatment on MPO concentrations was induced by osmotic minipumps in C57 mice. To test the effect of MPO on DDAH1 and -2 gene expression, taqman rtPCR technique was performed in liver and kidney tissue of MPO knockout mice. The effect of MPO on DDAH activity in vitro was studied using a recombinant DDAH enzyme. Results: ADMA and fMLP incubation -but not SDMA- significantly increased superoxide production, PMN degranulation and MPO release. Furthermore, ADMA but not SDMA was able to impair NO synthesis of PMN and enhanced PMN’s adhesion to cultured HUVECs in vitro. In vivo, chronic treatment with ADMA resulted in a significant increase of plasma MPO concentrations in C57 mice in contrast to vehicle-treated controls. DDAH1 gene expression was markedly increased in liver and kidney tissue of MPO knockout mice compared to C57 controls. In vitro, MPO and its product HOCl were able to impair recombinant DDAH activity, whereas inactivated MPO was not. Summary and conclusions: ADMA profoundly activates PMN resulting in increased degranulation and MPO release, superoxide production, and impaired NO synthesis. MPO modulates DDAH expression and impairs DDAH activity. Our data revealed a two-way interaction between the ADMA and MPO pathway, which may open a new avenue for treatment of cardiovascular disease.

Coupled TG–MS study on the intermediate for formation of PbO(t) from PbO(O) in synthesis of perovskite PMN–PT

Pb(OH) 2 was previously proposed as an intermediate in the synthesis of PMN [Pb(Mg 1/3Nb 2/3)O 3] and PMN–PT [0.9Pb(Mg 1/3Nb 2/3)O 3–0.1PbTiO 3] from a mixture of PbO, Nb 2O 5, Mg(NO 3) 2·6H 2O (w/w 0) TiO 2 by the modified mixed oxide method based on TG/DSC and XRD data. Coupled TG–MS of the precursor reveals that the intermediate is Pb 6O 5(NO 3) 2, not Pb(OH) 2 because the evolved gas was nitric oxide and oxygen, not water.

Hydrothermal synthesis of lead magnoniobate powder

Lead Magnoniobate (designated as PMN) is the most promising ferroelectric relaxor material. Hydrothermal synthesis of PMN under low temperature demonstrated positive results with niobium oxide as one of the starting materials. The as-prepared nanometer crystallized pyrochlore phase can be transformed into perovskite phase by heat treatment at elevated temperatures. Both of the powders before and after heat treatment were analysed by means of X-ray diffractometry (XRD), differential thermal analysis (DTA) and X-ray photoelectron spectroscopy (XPS).

Raman Spectroscopic Determination of Pyrochlore-Type Compound on the Synthesis and Decomposition of Sol-Gel-Derived Pb(Mg1/3Nb2/3)O3(PMN)

Raman spectroscopy was applied to the sol-gel-derived Pb(Mg1/3Nb2/3)O3(PMN) powder and thin film. Pyrochlore-type compound which forms on the synthesis of PMN contains Mg in the formula (Pb1.86Mg0.24Nb1.76O6.5) instead of Pb1.5Nb2O6.5, Pb2Nb2O7, or Pb2.8Nb2O7.8, which have been reported in the literature to form on the synthesis of PMN. It is rather difficult to distinguish these pyrochlore-type compounds by X-ray diffraction since thed-values of these compounds are very close to each other. From the result of Raman spectroscopy, it was also clarified that the pyrochlore-type compound formed by the decomposition of PMN thin film also contains Mg in the formula (Pb1.86Mg0.24Nb1.76O6.5).