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Bismuth sodium zirconate titanate ceramics with the formula Bi0.5Na0.5Zr1-xTixO3 [BNZT], where x = 0.3, 0.4, 0.5, and 0.6, were prepared by a conventional solid-state sintering method. Phase identification was investigated
using an X-ray diffraction technique. All compositions exhibited complete solubility of Ti4+ at the Zr4+ site. Both a decrease of unit cell size and phase transition from an orthorhombic Zr-rich composition to a rhombohedral crystal
structure in a Ti-rich composition were observed as a result of Ti4+ substitution. These changes caused dielectric properties of BNZT ceramics to enhance. Microstructural observation carried
out employing SEM showed that average grain size decreased when addition of Ti increased. Grain size difference of BNZT above
0.4 mole fraction of Ti4+ displayed a significant increase of dielectric constant at room temperature. 相似文献
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This research studied the effect of Nb doping on Bi0.5Na0.5[Ti0.41Zr0.59]O3 (when Nb concentration = 0.00, 0.01, 0.03, 0.05, 0.07 and 0.09 mol fraction). Nb doped BNTZ ceramics were fabricated using a conventional mixed-oxide method. All samples were calcined at a temperature of 700 °C for 2 h and sintered at a temperature of 900 °C for 2 h. X-ray diffraction patterns suggested that the compounds possessed rhombohedral perovskite structure. SEM micrographs indicated that average grain size decreased as the amount of Nb additives increased. The electrical resistivity showed a decreasing trend with increasing Nb concentration due to excess charge present in the sample. The dielectric constant and dielectric loss of samples showed no particular trend when Nb was added but the optimum was observed when 0.05–0.07 Nb mol fraction was present in BNTZ ceramics. In this study, both microstructure and donor-type effects played an important role in determining electrical resistivity and dielectric properties of these ceramics. 相似文献
3.
A martensitic NiTi foam was produced by hot isostatic pressing a blend of NiTi and NaF powders and subsequent dissolution of the NaF phase. The NiTi foam consists of 40 vol.% near-fully open pores, 240 μm in size, and with ragged surfaces due to incomplete NiTi powder densification. Near linear stress–strain curves are measured in compression with an average loading stiffness of 4 GPa, well below the unloading stiffness of 13 GPa because of detwinning on loading. Shape-memory recovery after unloading corresponds to 85–89% of the unloading plastic strain. After sintering at 1250 °C, the foam exhibits 20% porosity, smaller, smoother and partially-closed pores, and a shift in composition towards a martensite/austenite mixture at ambient temperature. This new composition allows for the activation of the superelastic effect in the austenite during loading and unloading resulting in average stiffnesses of 6–12 GPa, and the shape-memory effect in the martensite with 60–97% of the plastic strain recoverable. 相似文献
4.
Ampika Rachakom Panupong Jaiban Sukanda Jiansirisomboon Anucha Watcharapasorn 《Nanoscale research letters》2012,7(1):57
Lead-free bismuth sodium titanate zirconate (Bi0.5Na0.5Ti1-xZrxO3 where x = 0.20, 0.35, 0.40, 0.45, 0.60, and 0.80 mole fraction) [BNTZ] ceramics were successfully prepared using the conventional
mixed-oxide method. The samples were sintered for 2 h at temperatures lower than 1,000°C. The density of the BNTZ samples
was at least 95% of the theoretical values. The scanning electron microscopy micrographs showed that small grains were embedded
between large grains, causing a relatively wide grain size distribution. The density and grain size increased with increasing
Zr concentration. A peak shift in X-ray diffraction patterns as well as the disappearance of several hkl reflections indicated
some significant crystal-structure changes in these materials. Preliminary crystal-structure analysis indicated the existence
of phase transition from a rhombohedral to an orthorhombic structure. The dielectric and ferroelectric properties were also
found to correlate well with the observed phase transition. 相似文献
5.
Parichat Tanthakit Ampika Nakrachata-Amorn John F. Scamehorn David A. Sabatini Chantra Tongcumpou Sumaeth Chavadej 《Journal of surfactants and detergents》2009,12(2):173-183
In this study, the impact of water hardness and builder on the phase diagrams of motor oil microemulsions and the detergency
of oil removal from a polyester/cotton blend was investigated. Water hardness and builder were found to have insignificant
effects on the microemulsion phase diagram with motor oil. A mixed surfactant system of two parts C14–15(PO)3SO4Na, and 98 parts C12–14H25–29O(EO)5H of the total actives at 4% salinity was used to study the effect of water hardness and builders sodium tripolyphosphate
(STPP) or ethylenediaminetetraacetic acid (EDTA) on detergency at 30 °C at a total active concentration of 0.3%. This formulation
is in the Winsor Type III microemulsion regime. The microemulsion-based formulation resulted in better detergency than a leading
commercial liquid laundry detergent at all concentrations up to 0.5% actives. The microemulsion-based formulation showed a
plateau in detergency at >80% oil removal above 0.1% actives. The total oil removal decreased with increasing water hardness
while the interfacial tension increased. When hard water was used in laundering, the total oil removal improved with increasing
concentrations of STPP or EDTA up to stoichiometric levels, with STPP being slightly more effective than EDTA on a molar basis.
Even high builder concentration could not improve hard water detergency to that of soft water. A significant fraction of oil
removal occurred in the rinse steps vs. the wash step. Increasing water hardness reduced this fractional oil removal in the
rinse steps, but it was still over half of total oil removal at 1,000 ppm water hardness.
相似文献
Sumaeth ChavadejEmail: Email: |
6.
Lead-free bismuth sodium titanate zirconate (Bi0.5Na0.5Ti1?xZrxO3 or BNTZ) solid solutions with varied composition of x=0.50, 0.55, 0.58, 0.60, 0.63, 0.65, 0.68, 0.70, 0.73, 0.75 and 0.78 mol fraction were obtained using a conventional mixed-oxide method. XRD analysis indicated that the increase in concentration of Zr led to compositions across morphotropic phase boundary region. A quantitative structural investigation was carried out using the X-ray powder diffraction data. The rhombohedral phase was found to dominate for x<0.68 with space group R3c. In the morphotropic phase boundary (MPB) region i.e. 0.68≤x≤0.75, it was demonstrated that coexistence of rhombohedral and orthorhombic phase was observed. For x=0.78, the phase was completely orthorhombic with space group Pmna. Furthermore, the dielectric properties showed some enhanced activity of dipole movement at MPB boundaries which supported the presence of MPB region in this material system. 相似文献
7.
Ampika Bansiddhi David C. Dunand 《Journal of Materials Engineering and Performance》2011,20(4-5):511-516
Porous NiTi was produced by sintering pre-alloyed NiTi powders (with small Ni addition to form Ni-rich composition) with NaCl powders which are removed to create 40-60 vol.% macropores which are open to the surface, blocky in shape, and 100-400 ??m in size. The microporosity present between the NiTi powders is infiltrated by an in situ created NiTi-Nb eutectic liquid which, after solidification, densifies the NiTi powders into dense struts. This processing technique allows for separate control of the macroporous structure, and the densification and composition of the NiTi struts. 相似文献
8.
When NiTi powder compacts containing Nb wires are heated above 1 170 °C, each Nb wire reacts with adjacent NiTi powders to form a eutectic liquid which wicks into the space between the remaining NiTi powders. This creates a macropore at the location of the Nb wire while eliminating the microporosity between NiTi powders which is filled with a NiTi/Nb eutectic phase after solidification. This novel method produces – in a single step and without applied pressure – a dense NiTi matrix with elongated pores suitable for shape memory or superelastic applications such as bone implants, dampeners and actuators. 相似文献
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