Various aluminosilicate material have been used as precursor for geopolymer. Geopolymer gets its strength from the polycondensation of silicate and alumina. Metakaolin, calcinated kaolin, is pozzolan with the highest alumina and silicate purity. Indonesia, especially Bangka Island, has a large amount of kaolin deposit that being sold at low price. This price could be increased ten times when being sold as metakaolin. This study aimed to compare mechanical and metallurgical properties of commercial metakaolin and Bangka kaolin which calcinated at 700°C. Both metakaolins reacted with NaOH and waterglass as the activator followed by curing at room temperature for 7, 14 and 28 days and elevated temperature of 60°C for 4, 12 and 24 hours. Mechanical properties will be examined by compressive strength and flexural strength test, while the metallurgical properties will be evaluated with SEM, and TAM. The results of the mechanical test will be used to determine which geopolymer will perform well with the microstructure and thermal activity to support the finding. These attempts will be done in order to improve the properties of Bangka metakaolin geopolymer superior to commercial metakaolin.
CP Grade II titanium was first anodized in order to form TiO2 nanotubes, and then the TiO2 nano- tubes were coated with hydroxyapatite using the sol-gel method. The electrochemical properties of pure Ti, anodized TiO2 nanotubes, and HA-coated TiO2 nanotubes were investigated using poten- tiodynamic polarization and impedance tests. The sol-gel-coated HA nanoparticles were observed to sufficiently penetrate into the TiO2 nanotubes, and the polarization resistance of the HA-coated titanium nanotubes was higher than that of those that had just been anodized. In conclusion, the HA coating on the TiO2 nanotubes provides improved electrochemical properties and can be effective in overcoming the negative influence of passive TiO2 films.
Various This paper presents the results of the investigation on the use of Metakaolin (Al2Si2O2) as a supplementary cementing materials to improve the strength of cement. The most effective way to increase the strength of cement is the substitution of a proportion of cement with supplementary cementing materials. One of them was Metakaolin. Metakaolin was produced by thermal treatment calcination from Kaolin at 600-800 Celcius and has highest alumina and silicate purity. By added Metakaolin to Portland Cement type I (OPC), the amount of Calcium Silicate Hydrate (CSH) will increase through binding with Calcium Hydroxide (CaOH). There were two kinds of Metakaolin used in this investigation, commercial metakaolin named Metakaolin Metastar compared with Metakaolin Bangka which derived from Indonesia local resources, Bangka Island. Four Metakaolin replacement levels were employed in this investigation: 5%, 0%, 15%, and 20% with water per cement ratio 0.35, 0.40, and 0.50 both of Metakaolin Metastar and Metakaolin Bangka. The cement pastes cured at room temperature for 7, 14, and 28 days. The mechanical strength examined by compressive strength test, the microstructure were examined by SEM-EDS. The results of the study revealed both Metakaolin Metastar and Metakaolin Bangka enhanced the compressive strength of OPC. The most appropriate strength was obtained for a substitution of 20% metakaolin metastar which had 46,15% higher than OPC and 5% metakaolin Bangka which had 39,06% higher than OPC. The hydration rate was examined by Thermal Analysis Monitor. The results indicated that metakaolin metastar released higher heat than metakaolin Bangka. It can be concluded that Metakaolin metastar was more effective than metakaolin Bangka as additive in OPC.
Penelitian ini bertujuan untuk memahami teknik-teknik propaganda Politik Jalaluddin Rakhmat dalam kampanye pemilu tahun 2014. Metode penelitian yang digunakan adalah studi kasus. Pengumpulan data melalui wawancara mendalam, studi dokumentasi dan observasi lapangan. Teori yang digunakan adalah Teori Interaksionalisme Simbolik dan Teori Dramaturgis.
Hasil penelitian menunjukan Jalaluddin Rakhmat menggunakan berbagai tekhnik propaganda Politik dalam komunikasi politiknya yaitu sebagai berikut : (1). Penjulukan (name calling) yaitu memberi nama jelek kepada pihak lain; (2). Iming-Iming (glittering generalities) yaitu menggunakan kata-kata yang muluk,slogan-slogan, dan memutar balikan fakta; (3).transfer, yaitu melakukan identifikasi dengan lembaga-lembaga otoritas; (4).Testimonial yaitu pengulangan ucapan orang yang dihormati atau yang dibenci untuk mempromosikan atau meremehkan suatu maksud; (5). Merakyat (Plain foks) yaitu menempatkan diri sebagai bagian dari rakyat; (6). Menumpuk kartu (Card Stacking) yaitu memilih dengan teliti pernyataan yang akurat dan logis; dan (7). Gerobak Musik (bandwagon), yaitu mendorong Khalayak untuk bersama-sama orang banyak bergerak untuk mencapai tujuan atau kemenangan yang pasti.
Geopolymer material is an advanced material that is now being looked for its use as a refractory material, additive for building material, as well as other applications. Geopolymer is produced by polymerizing the precursor used in the process. One of the common precursors being used as geopolymer is metakaolin. The metakaolin was produced by thermal treatment (calcination) of kaolin minerals, which will convert its mineral structure from crystaline into amorphous and make it more reactive. This paper presents the fabrication and characterization of metakaolin using kaolin from Bangka island. The main structure of kaolin used in this study are kaolinite and muscovite according to XRD results obtained. Metakaolin was produced by thermal treatment using three different calcination temperatures ranged from 600 to 700 o C and calcined for 4 hours. Prior to calcination, some specimens will be mechanically milled using planetary ball mill for 15 minutes with the milling speed of 20.00 rad/s and will also be calcined with the same parameter. As a comparison, commercial metakaolin MetaStar also be used to compare it to all metakaolin produced. All metakaolin produced are characterized by XRD and SEM, and STA test will be performed to kaolin to examine its thermal behavior. The STA test performed to both milled and non-milled sample shows that dehydroxylation and reconstruction process occurs at temperature range of 460-520 o C and 520-640 o C for kaolin sample, and at temperature of 426-537 o C and 537-618 o C for milled kaolin sample. XRD pattern obtained shows that almost all metakaolin produced have the relatively similar pattern to each other as well as to MetaStar, with the main peak of quartz (SiO 2 ) at 2= 26.60 o to 26.65 o . The SEM results shows the characteristic layered-laminate plate-like structure of kaolin. Compared to another SEM results obtained, it can be concluded that there are no changes to the visible structure of metakaolin produced with the same kaolin used after calcination.
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