MPB Phase Transition and Microstructure of (1 – x)PMN–xPZT Activated by 0.05BZN Ceramics

The relaxor ferroelectric materials can be found in morphotropic phase boundary (MPB) existing between tetragonal and cubic phase. Since the MPB shifts to other phases by adding ceramics composition. [(1 – x)Pb(Mg_1/3 Nb_2/3)O₃–x Pb(Zr_0.52Ti_0.48)O₃] were doped by 0.05Ba(Zn_1/3 Nb_2/3)O₃ when x = 0.4, 0.3, and 0.2 ceramics, which prepared by using a two–step sintering process. The MPB transitions were studied by the use of XRD. The samples, at x = 0.4, were in MPB and then gradually shifted to cubic phase at x = 0.2. The microstructure of samples fracture found that the largest grain size of 4.51 μm for x = 0.2. This study using TEM technique which demonstrated a crystalline morphology with the largest crystal size about 1.293 μm at x = 0.3. These results also revealed that not only the ferroelectric phase shifted to relaxor behavior with decreasing PZT contents in PMN–PZT system but also activated by BZN, which led to the presence of the relaxor behavior.     

Formation of the Perovskite Phase in the PbMg1/3Nb2/3O3─PbTiO3 System

The reaction sequences during calcination of oxide mixtures were studied for the PbMg_1/3Nb_2/3O₃─PbTiO₃ (PMN-PT) system. The effect of reactivity and composition of the starting mixtures was investigated. In the present study, a B-site-deficient, cubic pyrochlore phase in the PbO-Nb₂O₅ system was formed at 500°C. The perovskite phase of PMN was formed at 7007deg;C through the diffusion of MgO into the pyrochlore phase. The lattice parameter of the pyrochlore phase decreased as this transformation to perovskite progressed.     

Phase development and dielectric responses in PMN–BNT ceramics

(1 − x)Pb(Mg_1/3Nb_2/3)O₃–x(Bi_0.5Na_0.5)TiO₃ ceramics were prepared by the conventional mixed-oxide method. All compositions show complete perovskite solid solutions and the structure to change from cubic to rhombohedral at x = 0.5. The dielectric constant and dielectric loss tangent were measured as a function of both temperature and frequency. The results indicated a relaxor ferroelectric behavior for all ceramics. The temperature at maximum of the dielectric constant of PMN–BNT ceramics were seen to increase with increasing BNT content. Moreover, the broadest dielectric peak occurs at x = 0.9, which leads to a morphotropic phase boundary in this system.     

退火对PMN—PT系陶瓷电学性能的影响

研究了退火对（１－ｘ）ＰＭＮ－ｘＰＴ（ｘ＝０－０．３４）陶瓷介电和压电性能的影响。分析了机理。结果表明，在ＰＴ含量较低时，退火使介电常数稍有提高；ＰＴ含量较高，接近准同型相界时，退火使介电常数有较大提高，尤其在居里温度附近，介电常数有显著提高。     

Nanoporous aluminum oxide affects neutrophil behaviour

This study evaluates neutrophil responses on aluminum oxide membranes. Using an in vitro cell culture system, we have found that the pore size (20 and 200 nm in diameter) of alumina membranes have a significant effect on leukocyte morphology and activation. Specifically, our results show that 20-nm pore-size membranes were more potent in triggering PMN spreading and extending of pseudopodia than 200-nm pore-size membranes. The morphological changes are also associated with cell activation. In fact, adherent neutrophils on 20-nm pore-size membranes elicit much stronger initial oxygen free radical production. Overall, our results point out that membrane pore size significantly affects the extent of cellular responses of adherent neutrophils.     

PMN基铁电陶瓷电镀镍性能失效及恢复研究

针对铌镁酸铅（PMN）基弛豫铁电陶瓷电镀镍后性能失效行为,采用介温谱、绝缘电阻测量及高温退火方法进行了研究。实验表明,PMN基驰豫铁电镀镍后会出现介电常数下降、介质损耗和绝缘电阻增大,随电镀时间延长,试样失效程度增加。电镀失效试样经过500℃、2.5h空气退火后,性能完全恢复,分析认为,电镀过程中产生的活泼原子氢吸附在资体上,将瓷体中的某些金属元素还原,产生氧空位和自由电子,导致陶瓷电性能失效。而经过适当的氧化气氛退火后,失效试样被重新氧化,使得电性能恢复。     

EFFECT OF SHEAR STRESS ON PLATELET-PMN LEUKOCYTE INTERACTIONS

A cone and plate viscometer, Coulter counter, and spectrophotometer were used to study platelet modulation of polymorphonuclear leukocyte (PMNL) function caused by controlled shear stress. Aggregation and release of the enzymes β-glucuronidase and lactate dehydrogenase (LDH) were observed. PMNL suspensions in buffer (1.0 × 10⁷ cells/ml, final concentration) did not show any aggregate formation or enzyme release at shear stresses below 150 dynes/cm² for an exposure time of 1 minute. However, supernatant plasma from sheared platelets initiated PMNL aggregation and β-glucuronidase release at moderate shear stresses (150 dynes/cm² for 1 minute). These stress-induced alterations were compared with chemotactic factor and calcium ionophore A23187 induced functional changes. LDH release was less than 3% in all the experiments indicating little overt lysis. The shear-induced enzyme release was enhanced by cytochalasin B and heparinized samples showed greater effects than citrated samples. The use of a cyclooxygenase inhibitor (acetylsalicyclic acid, 50 μM) did not suppress the aggregation of PMNLs after shear. However, preincubation with lipoxygenase inhibitors (nordihydroguaiaretic acid, 10 μM, and U-60257, 10 μM) suppressed aggregation and enzyme release. The formation of arachidonic acid metabolites activated by shear stress was documented by reversed phase-high pressure liquid chromatography. Thus, an interaction between C-12 and C-5 lipoxygenase enzymes can promote the formation of leukotriene B₄ and these data strongly support the possibility of a cooperation between platelet and PMNL arachidonic acid metabolites in shear-induced PMNL functional changes.     

PMN-PFW基陶瓷的制备及介电性能研究

用二次合成法制备了 0 .2 4 Pb(Fe2 / 3W1 / 3) O3- 0 .0 6 Pb(Fe1 / 2 Nb1 / 2 ) O3- 0 .5 6 Pb(Mg1 / 3Nb2 / 3) O3- 0 .14 Pb Ti O3固溶体陶瓷 ,分别研究了预烧温度和烧结温度对其预烧粉体和陶瓷的相组成的影响 ,详细研究了烧结温度及掺锰对PMN- PFW基陶瓷介电性能的影响