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This paper reports a study of a wiki-based collaborative writing project conducted between two Taiwanese universities. A total of 100 sophomore students from two English writing classes used the wiki with group members to collaboratively produce online picture books. The aims of the study were to examine student perception, their engagement in the project, and their overall writing development. Various sources of data, including the questionnaires, archived changes of wiki pages, and pre- and post-project essay writing scores were collected and analyzed. The results showed that students' general opinions toward the project were positive. Students particularly appreciated the experience of collaborating with peers. However, the students found it challenging to negotiate a common work schedule and to reach group agreement. Students' engagement in the collaborative writing project varied, due in large part to their diverse English proficiency levels. Specifically, more proficient English writers appeared to be more engaged in the writing tasks, while less proficient writers tended to contribute by offering story ideas and arranging layouts. In the end, students' writing skills on average improved more as a result of the frequent writing practice and peer editing tasks, rather than from the completion of the online picture books. [ABSTRACT FROM AUTHOR]

Local dopant compositions within individual α-Sialon grains were measured by analytical electron microscopy (AEM) in hot-pressed CaxSi12-3xAl3xOxN16-x (x = 0.3-1.4) ceramics. The reduction of local x values from the nominal dopant compositions is about 40% in general, and it reaches 60% for the end member (x = 1.4) which contains inclusions of AlN-based 21R phase. This results exhibit stronger departures from x than the previous report of 30% dopants missing in α-Sialon phase by electron probe micro-analysis (EPMA) [J Eur Ceram Soc 19:1637, 1999]. Amorphous films of ∼1 nm thick were commonly found at grain boundaries (GBs), which could only take a small fraction of undetected dopants while the film composition exhibits a quite different behavior. The general presence of GB films can rationalize the discrepancy between AEM and EPMA results by their differences in probe size and detection geometry, while the much larger gap in the end member suggests the existence of Ca-rich glasses in the intergranular regions. By excluding this end member, a linear relation between dopant solution and lattice expansion is restored in α-Sialon structure, which leads to 20 and 80% increases of the expansion coefficients from those given in the previous and original reports, respectively. This study not only demonstrated the necessity of solubility study in ceramics by AEM refinement, but also opens a new front to correlate the solution behavior with the intergranular glass/amorphous structures, both were regarded so far as largely independent. [ABSTRACT FROM AUTHOR]

A proper powder preparation was used to develop α-Sialon single crystals as seeds. The microstructure and fracture toughness of seed-containing α-Sialon ceramics sintered by hot-pressing were investigated. The specimen without seeding consisted of fine grains and a small amount of coarse grains. Specimens seeded with α-Sialon single crystal particles presented a large amount of elongated α-Sialon grains. The aspect ratio and the amount of elongated α-Sialon grains can be tailored by using different sizes and amounts of the seeds. The fracture toughness of seed-containing α-Sialon ceramics is improved, which is attributed to grain pullout and bridging of elongated grains. [ABSTRACT FROM AUTHOR]

Two R-α-sialon (R0.6Si9.3Al2.7O0.9N15.1, R=Nd and Er) compositions were first fired at 1750°C/25 min and 1650°C/2 h respectively for completion of the α → α′ phase transformation. Elongated α-sialon grain morphology was developed in both samples after being re-fired at 1800°C for different periods of time. The growth in width of R-α-sialon grains is controlled by diffusion in the liquid, while the length growth tends to be interfacial reaction controlled. The anisotropic growth of R-α-sialon is attributed to the large difference in the growth rate constant between the length and the width directions of the grain. [ABSTRACT FROM AUTHOR]

The influence of processing on microstructural development of Ca α-sialon composition (Ca xSi12−3 xAl3 xO xN16− x) with x = 1.8 was studied by dwelling at different intermediate temperatures before reaching the final sintering temperature. The microstructural observation results have showed the different aspect ratios of elongated grains obtained by the various processing conditions, reflecting the effect of the number of nuclei of α-sialon on morphology of grains during sintering. Improved toughness was achieved by applying low temperature dwelling for Ca α-sialon compositions with low x values. The toughness showed an increase of 33% and 16% for x = 0.6 and 1.0 compositions respectively with middle dwelling processing at 1350°C for 3 h before reaching 1750°C for 1 h by hot-pressing. [ABSTRACT FROM AUTHOR]

Examines the formation behavior of strontium barium niobate (SBN) synthesized by conventional mixed-oxide and molten salt synthesis methods. Difference in phase assemblage; Cell dimensions of SBN; Phase analysis of the synthesized SBN powders.