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Muhammad Waziz Wildan

Department of Mechanical and Industrial Engineering, Faculty of Engineering, Universitas Gadjah Mada. Jl. Grafika 2, Yogyakarta 55281, Indonesia

Author-ID : 3514573

Engineering Industrial & Manufacturing Engineering Mechanical Engineering

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Compressive Strength and Thermal Conductivity of Porous Mullite Ceramics Muhammad Waziz Wildan; F Marpaung
Journal of Material Processing and Characterization Vol 1, No 1 (2020): Articles
Publisher : Departmen Teknik Mesin dan Industri, Fakultas Teknik, Universitas Gadjah Mada

Porous ceramics are a form of ceramic material with widespread applications, such as filters, isolators, and acoustics. This research aimed to investigate the compressive strength and thermal conductivity of porous mullite ceramics (3Al2O3.2SiO2 or Si2Al6O13) produced using dry yeast powder as a PFA (pore-forming agent). Kaolin powder (Al2O3.2SiO4.2H2O or Al2Si2O5(OH)4) was used as a raw material for producing mullite ceramics. Kaolin powder and dry yeast powder were mixed at a variety of dry yeast powder weight fractions: 0%, 5%, 10%, 15%, 20%, and 25%. The composition was mixed using Turbula Mixer for 1 hour. The cylindrical green body (diameters of 12 mm, 15 mm, and 30 mm) of every constituent was formed by the uniaxial pressing method at 10 MPa. Monolithic kaolin was sintered at variable temperatures (1,100 oC, 1,200 oC, 1,300 oC, 1,400 oC, 1,450 oC) for 2 hours then subjected to several tests for its density. From the bulk density tests, it was found that the optimum temperature for 2-hour sintering was 1,450 oC. This temperature was then used for the sintering process of the kaolin specimens which contained dry yeast powder. Testing was performed on the microstructure, bulk density, burning waste in mass and volume, compressive strength, and thermal conductivity. According to the literature, kaolin will transform into mullite (3Al2O3.2SiO2 or Si2Al6O13) and cristobalite (SiO2) at 1,450 oC. It was found that with the increase in the content of dry yeast powder as PFA in the mixture with kaolin, the bulk density decreased (from 2.44 gr/cm3 to 1.521 gr/cm3), the porosity increased (from 23.77% to 52.48%), the compressive strength decreased (from 38.04 MPa to 4.51 MPa), and the thermal conductivity decreased (from 3.76 W/moC to1.34 W/moC), each from yeast powder content 0% to 25%.

A Preliminary Study of Extraction and Characterization of Nanocrystalline Cellulose (NCC) from Ramie Fiber K Kusmono; Muhammad Waziz Wildan; Mochammad Noer Ilman
Journal of Material Processing and Characterization Vol 1, No 1 (2020): Articles
Publisher : Departmen Teknik Mesin dan Industri, Fakultas Teknik, Universitas Gadjah Mada

Nanocrystalline cellulose (NCC) is today’s one of rapidly growing nanocomposite reinforcing materials. This is thanks to some advantages that come with it over anorganic nanocomposite reinforcing materials, for example, nanoclay, nanosilica, nanoalumina, carbon nanotubes, among others. Some of the advantages of NCC are environment-friendliness due to being organic-compound-based, high mechanical property, and easy manufacturing. NCC can be extracted from natural cellulose sources, such as natural fiber, wood, and animals. One of the natural fibers rich in cellulose content, in this case around 80%, is fiber of ramie which is ubiquitous in Indonesia. It is well known that the acid hydrolysis method is an easy route to NCC fabrication. A number of chemical treatments like de-waxing, bleaching, and alkaline treatment are typically performed prior to acid hydrolysis process. The effect of such chemical treatments as precursors of alkaline hydrolysis on ramie fiber characteristics was investigated in this research. Firstly, ramie fiber was cut 1 cm in size, then grinded and sieved. The fiber was then subjected to de-waxing process by adding it into a toluene-ethanol solution (1:2). Then, it was submitted to bleaching with 0.7% sodium chlorite (NaClO2) solution at 75 °C for 1 hour. Lastly, the fiber was subjected to an alkaline treatment in 2% NaOH solution for 2 hours. Characterization with FT-IR, XRD, and TGA of the fiber which had underwent a number of surface treatments was conducted. Results show that the chemical treatments had successfully removed amorphous components like lignin and hemicellulose from the ramie fiber. Chemical treatments were proven able to increase the crystallinity index and thermal stability of ramie fiber.

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