Judul: Sintesis Nanosilika dari Abu Ketel Industri Gula Mengguakan Metode Ko-presipitasi dengan Template Pati.
Abstrak: Boiler ash is by product of the sugar industry which is not yet widely used. Boiler ash is highly silica content that can be utilized as nanosilica. The purpose of this study to synthesis nanosilica using boiler ash with the addition of tapioca and corn starch as a template. This research aims to know the effect of tapioca and cornstarch on characteristic of nanosilica, and also give information about the aplication of nanosilica with starch template. The researchs consist of four part that is preparation of material, synthesis of silica, synthesis of nanosilica, and characterization of nanosilica. 49,69% bagasse ash is composed of silica and after the furnace at a temperature of 7000 C the furnace ash containing 78,75% silica. Characteristics of nanosilika was multiphase consist of quartz, tridimit, and krisrobalit phase with cristobalite as the predominant phase.The most high crystallinity of nanosilika was 82,070% at treatment without addition of the template and the smallest crystallinity was 49,063% on addition corn starch at 33,33%. Starch contain of amylose that have contributed on decreasing cristalinity of nanosilica. Particle size of nanosilika was more homegen with the addition of corn starch when PDI’s number was above 0,1. Observation by SEM showed that the particle has polygonal form and looks spreads. Commonly, the effect of starch as a template was decreased the particle size, distrubution of particle, cristalinity, and cristal size. Characteristic of nanosilika that produced by starch’s template can aplicate as a silica-polymer nanocomposit and as a filler for ceramic’s material.
Keyword: boiler ash, co-presipitation, nanosilica, starch

Judul: Sintesis dan Pencirian Nanosilika Berbahan Dasar Abu Ketel Industri Gula dengan Variasi Waktu Aging dan pH Presipitasi.
Abstrak: Boiler ash from sugar cane industry contains silica that was synthesized to nanosilica using precipitation method. Precipitation pH and aging time are parameters that have influenced to nanosilica characterization. The purpose of this research was to synthesis nanosilica from boiler ash using precipitation method, determine the effect of precipitation pH and aging time variation on the characterization of nanosilica, determine the potential application based on characterization of nanosilica. The research was consist of three stages, preparation of boiler ash, extraction silica from furnace ash, and synthesis nanosilica. Boiler ash from sugar cane industry contained 49.69% silica and furnace ash contained 78.75% silica. Nanosilica was material or compound that have multifase characterization. Increase precipitation pH would increase amount of crystal phase, diffraction peak, and intensity of diffraction peak. Increase aging time would increase intensity of diffraction peak and amount of crystal phase. Degree of crystallinity has ranges 66.397–93.530%, average of crystal size has ranges 37.772–56.867 nm, average of particle size has ranges 214.04–698.24 nm, and PDI value has ranges 0.207–0.833. Increase precipitation pH and aging time would increase amount of siloksane groups and decrease amount of silanol groups. Nanosilica has potential application as a composit of electrolyte membrane DMFC (Direct Methanol Fuel Cell), composit of addition support layer membrane ultrafiltration, filler in ship rubber air bag, filler of composit resin, and SCM (Supplementary Cementitious Material) for concrete.
Keyword: aging time, boiler ash, nanosilica, precipitation, precipitation pH

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
Keyword: