Effect of hot pressing on processing and properties of BBN ceramics

BBN (BaBi₂Nb₂O₉) is very interesting and promising lead free material with relaxor properties in capacitors, sensors and actuators.     

Interactive video technology: Enhancing professional learning in initial teacher education

The University of Sussex In-School Teacher Education Project (InSTEP) uses interactive video technologies to enhance initial teacher education programmes for science trainee teachers. With four Internet Protocol cameras and mounted microphones in both school laboratories and the university teaching room, trainees and their tutors have access to live interaction with schools. This paper presents some of the findings of a 2 year evaluation of InSTEP aimed at identifying the benefits for trainee teachers. There has been an increase in the use of video material for teacher training purposes, however, trainee teachers are often intimidated by carefully selected extracts featuring experienced teachers. InSTEP activities are live and capitalise on all the opportunities associated with normal classroom practice. Literature points to InSTEP-type activities having the potential to enhance the development of trainees’ observation skills, develop reflective thinking, to provide authentic illustrations of classroom practice, enable remote observation and facilitate the coaching of trainees by mentors. A fourth generation model of evaluation was undertaken with data generated by semi-structured interviews with university tutors and mentors supported by a questionnaire and group interviews with the trainees. Our main findings point to InSTEP enhancing and accelerating the growth of trainee teachers’ professional knowledge through enabling reflective practice, facilitating collaborative learning and supporting the development of the language of pedagogy.     

Dielectric properties of BaBi2Nb2O9 ceramics

The crystal structure and dielectric properties as a function of temperature for Ba-based with Bi-layered structure BaBi₂Nb₂O₉ (BBN) ceramics were investigated. The obtained results confirmed the relaxor ferroelectric behavior of the studied ceramics, including a strong frequency dispersion of the permittivity maximum and a visible shift of its temperature with frequency. Analysis of the real and imaginary part of permittivity allowed us to determine the values of Burn’s temperature and of the freezing temperature characterizing the relaxor ferroelectrics. The physical processes, responsible for the relaxor behavior of the studied ceramics are discussed. The additional low frequency dielectric dispersion at high temperatures in the paraelectric phase range was also observed. Correlation between this dispersion and the thermally stimulated depolarization current was ascertained.     

Thermochemical Treatment--Technologies for Recovery and Utilisation of Materials

The arc furnace technology is an ideally suited process for the treatment of hazardous and problematic waste. The operation conditions of the arc furnace can be adapted for optimal transformation of the waste material input into raw materials and usable products. The process can significantly reduce the impact of contaminated wastes and industrial residues, and enable material conversion and separation. Thus, the products of the process have various applications. The capability of the process is illustrated with three examples, the treatment of bottom ash and filter ash from waste incineration plants, of stainless steel slags and of chromium containing residues from the refractory industry.     

Long-term storage stability of selected potato starch – Non-starchy hydrocolloid binary gels

All 3, 4 and 5% potato starch gels containing either κ-carrageenan, guar gum or xanthan gum were prepared and their stability in terms of rheological and textural properties was checked on 30 day storage. It was shown that rheology of these binary potato starch – non-starchy hydrocolloid mixtures could be controlled by anionic character of the admixed hydrocolloid. Depending on the hydrocolloid added, gels made of the tuber starch can either retain their pattern typical for tuber starches or turn into that typical for gels of cereal starches. Hydrocolloids added plasticity to the binary gels but it was lost to a significant extent within the first day of storage. Resulting gels with dominating elastic character are rheologically and texturally fairly stable for subsequent 30 days of storage. Generally, hydrocolloids stabilized potato starch gel on long-time storage to the extent dependent on the gel concentration.     

Diffusion of polymer chains in porous media. A Monte Carlo study

In order to determine the structure and the dynamical properties of branched polymers in a random environment an idealized model was developed and studied by means of the Monte Carlo method. All atomic details were suppressed and the chain was represented as a sequence of identical beads. The model chains were star-branched with three arms of equal length. The chains were embedded to a simple cubic lattice and the polymer systems were confined between two parallel surfaces. The confining surfaces were attractive for polymer segments. A set of irregular obstacles was also introduced into the slit which can be viewed as a model of porous media. A Metropolis sampling algorithm employing local changes of chain conformation was used to sample the conformational space. It was shown that the mean dimensions of the chain depend strongly on the strength of surface's attraction and the concentration of obstacles. It was found that the size of the chains scales with the exponent close to the 2-dimensional case rather than to the 3-dimensional system. The long-time (diffusion) dynamic properties of the system were studied. The differences in the mobility of chains depending on the confinement, on the filling of the slit and on the internal macromolecular architectures were shown and discussed. The possible mechanism of chain's motion was shown: during the migration of the chain in the obstacles dense environment it can be trapped in the region of local lower density of obstacles (a ‘cavity’) and after some time it can leave the place moving into another cavity.     

Hole expansion in a variety of sheet steels

Expanding pierced holes is a common forming practice and problems during these operations are not unusual. A damczyk and Michal have previously developed an equation for maximum hole expansion of HSLA steels, for holes in the sheared then deburred condition. This paper expands the work of the above authors. Nineteen ferritic, ferritic stainless, and austenitic stainless steels were evaluated for hole expansion using various hole-edge conditions. It was found that the behavior of steels having finished holes is very different than those tested in the as-sheared condition. Relationships between hole expansion and tensile-mechanical properties were developed for both conditions.