Microstructure and ferroelectric properties of soft-doped sol–gel derived PZT/SKN fibers

Sol–gel derived PZT/SKN fibers with a final composition of 0.98(PbO)_1+z (Zr_0.53Ti_0.47)O₂-0.02Sr(K_0.25Nb_0.75)O₃ and a PbO content of z = +0.04 and +0.14 in the spinning sol were sintered at different temperatures. Fiber stoichiometry, phase content and microstructure as well as the physical properties of the fibers were investigated. A fully densified microstructure independent from the initial PbO content was obtained for fibers sintered at 950 °C or higher. Enhanced porosity was found only for fibers sintered at 900 °C. The densification of the fiber batches at the lower temperatures is dominated by solid state sintering, while liquid phase sintering is promoted by sintering at temperatures above 900 °C. TEM investigations confirmed the homogeneous nature of the PZT/SKN fibers devoid of compositional gradients. Typical dielectric permittivity is in the range of 650–1000. The ferroelectric hysteresis loops are well pronounced showing typical soft-doped behavior with remanent polarization values in the range of 15 and 34 μC/cm² and coercivities of about 1.9 V/μm.     

人为本形次之——扬州老城保护的中德合作探索与实践

本文介绍了GTZ与扬州市政府合作开展老城保护与更新项目的过程,通过鼓励市民参与,引入社区行动规划(CAP)的方法,探索了一条更具科学性和实施性的老城保护之路。     

Photocatalytic reactors for treating water pollution with solar illumination. III: a simplified analysis for recirculating reactors

A solar photoreactor operated in the batch, recirculating mode is analyzed in terms of very simple observable variables such as the impinging photon flux, the incident area, the initial concentration, the flow rate, the reactor volume and a property defined as the Observed Photonic Efficiency. The proposed equipment is made of a tubular reactor, a tank, a pump and the connecting pipes. The analysis is formulated in terms of the photon input corresponding to an equivalent batch system that is derived as a new reaction coordinate for photoreactions. Employing several plausible approximations, the pollutant concentration evolution in the tank is cast in terms of very simple analytical solutions.Process photonic efficiencies are defined for the system operation and calculated with respect to the maximum achievable yield corresponding to the differential operation of the solar recirculating reactor.     

Materials research in Europe: Mapping excellence and looking ahead

The European Research Area has been established to coordinate national research policies and to encourage shared objectives, expertise, and resources throughout the European Union. To accomplish these goals, the European Research Area first needs knowledge of existing resources, fields of excellence, and potential for improvements as well as an idea of the direction of future research. This article describes the SMART project, established by the European Commission to identify important research topics for the future in the field of materials technology and to map materials research regions of excellence.     

N-异丙基丙烯酰胺凝胶在乙醇水溶液中的溶胀平衡

N-isopropylacrylamide (NIPAAm) was used to synthesize NIPAAm homopolymer (nonionized) and NIPAAm-sodium methacrylate copolymer (ionized). The swelling equilibria for both gels were obtained in aqueous solution of ethanol with concentration ranging from 0 to 100%(by mass) at 25℃. The swollen gel in water shrank first with the addition of a small amount of ethanol and then reswelled with further addition of ethanol showing not only a discontinuous volume phase transition but also a typical reentrant phenomenon. A thermodynamic model based on the UNIQUAC with the “free-volume“ contribution was applied to correlate and predict the swelling behavior of the poly(NIPAAM)-gels in ethanol-water mixture.     

Learning to learn during visual discrimination in group housed dwarf goats (Capra hircus).

Using an automated learning device, we investigated "learning to learn" by dwarf goats (Capra hircus) in what was for them a familiar environment and normal social settings. Nine problems, each consisting of four discriminable black symbols, each with one S+ and three different S-, were presented on a computer screen. Mean daily learning success improved over the course of the first four problems, and the improvement was maintained throughout the remaining five problems. The number of trials to reach the learning criterion decreased significantly beginning with problem four. Such results may be interpreted as evidence that the goats were developing a learning set. In the present case, the learning set appeared to have two components. One involved gaining familiarity and apparent understanding of the learning device and the basic requirements of the discrimination task. The second component involved learning potential error factors to be ignored, as well as learning commonalities that carried over from one problem to the next. Among the error factors, evidence of apparent preferences for specific symbols was seen, which had a predictable effect on performances. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimating the hydrolytic durability of cured wood adhesives by measuring formaldehyde liberation and structural stability

The durability of different commonly used thermosetting wood adhesives (UF, MUF, MUPF) was determined from the hydrolytically induced mass loss and the amount of liberated formaldehyde. Both methods showed high reproducibility. Different methodical aspects were investigated for further improvement. The hydrolytically induced mass loss and formaldehyde liberation depend on the particle size of the cured resins. Additionally, more severe hydrolytic conditions (time, pH, temperature) caused elevated mass losses and formaldehyde liberations. The hydrolytic stability of the cured resins could be well determined by gravimetric analysis. However, a distinct graduation of the adhesive durability according to formaldehyde liberation appeared to be more difficult. These findings were reinforced by correlating the hydrolytic indicators and wet strength properties of particle boards according to different test methods (V70, V100, EN 321, Werzalit cycle test).     

EUV‐Lithographie für zukünftige IC‐Chips. EUV‐Lithography for Future IC‐Technology

In the past the overwhelming success of the semiconductor industry was based on the realisation of ever smaller structures on chips in ever shorter periods. This allowed to increase the computational speed of the processors and the amount of data that can be stored in a memory chip. This reduction of the critical dimension was mastered within optical lithography by transition to smaller wavelengths. Those lithography technologies that are currently in the development or test phase, based on 193 nm or as well 157 nm laser sources, will not achieve dimensions around 50 nm. A fundamental change of technology is thus emerging. The currently favored basis for dimensions of 50 nm and below is EUV lithography, based on an optical technology with an exposure wavelength of 13,4 nm. This substantial reduction of the wavelength also implies a radical change of the methodology used up to now.