Understanding of effects of changes in the particle size of the matrix material on the mullite whisker growth during the production of porous mullite is crucial for better design of new porous ceramics materials in different applications. Commercially, raw materials such as Al2O3/SiO2 and Al(OH)3/SiO2 are used as starting materials, while AlF3 is added to fabricate porous mullite through reaction sintering process. When Al2O3 is used as a starting material, a porous microstructure can be identified, but a more developed needle shaped microstructure is identified in the specimen using Al(OH)3, which has excellent reactivity. The specimen using Al2O3/SiO2 composite powder does not undergo mulliteization even at 1,400 oC, but the specimen using the Al(OH)3/SiO2 composite powder had already formed complete mullite whiskers from the particle size specimen milled for 3 h at 1,100 oC. As a result, the change in sintering temperature does not significantly affect formation of microstructures. As the particle size of the matrix materials, Al2O3 and Al(OH)3, decreases, the porosity tends to decrease. In the case of the Al(OH)3/SiO2 composite powder, the highest porosity obtained is 75% when the particle size passes through a milling time of 3 h. The smaller the particle size of Al(OH)3 is and the more the long/short ratio of the mullite whisker phase decreases, the higher the density becomes.

The purpose of this study is to investigate the current status of the creation of indoor gardens in elementary, middle, and high-schools in Gyeongsangnam-do (province) as part of a program to make schools comfortable and beautiful, and for use as base line data when introducing indoor gardens to schools. The participating schools comprised all 536 elementary, 306 middle, and 191 high schools in Gyeongsangnam-do, and the study was conducted between Dec. 20th, 2014 and July 23rd, 2015. The results demonstrate that indoor gardens were introduced to Gyeongsangnam-do schools in 2010, and, since then, 35 elementary and 3 middle schools have created indoor gardens, which is a low adoption rate. Eight-four percent of these indoor gardens were created for appreciation purposes only, without rest facilities. Indoor plants were the main material used for scene configurations, followed by rocks and sculptures. Taking into consideration that 92% of all indoor gardens were created in elementary schools, the current location of gardens near the main entrance, mainly for appreciation purposes, should be changed to areas in which students can play and rest, which would lead to an increase in students’ usage rate.