Geopolymer is widely known as an environmentally-friendly construction material due to the remarkably low emission of CO2 in its manufacturing process. This inorganic polymer can be produced via two precursors: solid component and alkaline activator. In the present work, the studied program was divided into two steps. In Step 1, the molarity of NaOH was investigated. The calcined-kaolin from Lampang city (Thailand source) was used as base alumino-silicate material. In addition, the concentrations of NaOH (5M, 10M, 15M and 20M) were utilized as alkaline activator for geopolymerization. After mixing, the geopolymer slurry was casted into a size of a 50 mm ´ 50 mm ´ 50 mm steel mold. The curing condition of all specimens was maintained at 60°C for 7 days. The compressive strength of all specimens was tested. The utilization of 10M of NaOH yielded the highest compressive strength with the value of 22.01 MPa. In Step 2, 10M of NaOH was fixed and used as alkaline activator. In this case, the amount of waste glass (0%, 10%, 20%, 30%, 40% and 50% by weight) was studied on partial calcined-kaolin replacement. However, the compressive strength of all samples slightly changed with an increasing weight percentage of waste glass (0% - 20 %). The highest compressive strength of 20 wt% waste glass was 25.22 MPa. Although, all samples showed a Si-O-Al bond in the FTIR result, indicating the geopolymer degree strenghened. However, the compressive strength of samples tended to decrease with an increase in the amount of waste glass (30 to 50 wt%) as a result of micro-cracks observed and distributed in the samples.

La4-xSrxNi3O10±δ (x = 0, 0.05, 0.1, 0.2, 0.3, 0.5 and 1) compositions synthesized via citrate gel method have been investigated as a candidate cathode for intermediate temperature SOFC. The n = 3 RP single phase of La4-xSrxNi3O10±δ (x = 0, 0.05, 0.1 and 0.2) can be achieved after calcined at 1000°C for 4 hrs in air. The further addition of Sr with x 0.3 leads to obtain La2-xSrxNiO4±δ and NiO as the second phase. La4Ni3O10±δ based material shows the highest electrical conductivity with a value of 124 S/cm at room temperature. With Sr dopant, both of transition temperature and the electrical conductivity of La4Ni3O10±δ decrease and further decrease with increasing the amount of Sr. The electrical conductivity at 250°C of La4-xSrxNi3O10±δ (x = 0, 0.05 and 0.1) is 100, 94 and 75 S/cm respectively. For x = 0.3, 0.5 and 1, it reduces to the values of 28, 7 and 4 S/cm, respectively because of the lower conductivity phase of La2-xSrxNiO4±δ.

The effect of Sr doped La4-xSrxNi3O10±δ (x = 0, 0.05, 0.1, 0.2 and 0.3) has been investigated as an intermediate temperature SOFC cathode material. The Ruddlesden-Popper (RP) compositions of n = 3 were successfully synthesized via citrate gel method. The single phase of sintered La4-xSrxNi3O10±δ (x = 0, 0.05, 0.1 and 0.2) powders was confirmed as an orthorhombic structure. However, this structure changes to more symmetry with an increasing amount of Sr dopant. With x = 0.3, the phases of La1.7Sr0.3NiO4 as n = 1 RP and NiO appear without n = 3 RP. La3.95Sr0.05Ni3O10±δ shows the highest electrical conductivity with a value of 140 S/cm at room temperature. Nevertheless, the electrical conductivity of La4-xSrxNi3O10±δ decreases and further decreases with increasing amount of Sr. The conductivity values at 200°C of La4-xSrxNi3O10±δ (x =0, 0.05 and 0.1) are 89, 113 and 101 S/cm, respectively. For x = 0.3, the conductivity decreases lower than x 0.1 with its value of 36 S/cm because of the low conductivity phase of n = 1 RP.

Rice husk ash was used as an active-SiO2 source for the production of low-cost metakaolin based geopolymer. For cost reduction, active-SiO2 from husk ash was used as an alternative Na2SiO3 activator replacement. The starting materials such as metakaolin, husk ash and NaOH with SiO2/Al2O3 ratios of 1.58 - 1.95 were studied and calculated by XRF results. The fast hardening of geopolymer from husk ash occurred after curing at room temperature for 24 hrs. The strength of all samples was enhanced by increasing the amount of active-SiO2 from husk ash. The geopolymer from husk ash with SiO2/Al2O3 ratio of 1.95 showed high compressive strength with a value of 25 MPa. The production cost of geopolymer from husk ash was decreased with the value of 84.78%. Husk ash is an alternative natural active-SiO2 for replacing Na2SiO3 activator in the geopolymer manufacturing process, indicating a decrease in the cost of the process.