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"Composited tile was made using marble particles, phenol resin and hcxamethy leneleiramine (HEXA) as the catalyst. The matrix and hardener of these materials were mixed on volume variation from 62.50 ml to 12?,()<) ml. and on variation of 25. 40 and 60 mesh. Samples were dried in a room temperature for 3 hours. The compressive strength and crystal structure were analysed. The results showed that compressive strength values were in range of 6.15 x I07 N/m" - 9.61 x Id7 N/n. and there were two crystal structures consisted of marble crystal and phenol crystal. The analysis was carried out by using the Rietveld semi quantitative analysis. The final crystal structure of marble is rhombothedral, where the lanice constants arc a h =- 4.969 A: c = 17.026 A. This results indicate that the composites and marble can he used to make tile, because they were lighter, stronger and the amount of crystals increases compared with the pure marble."

"Doping yttrium ions, Y3+ into ZrO2 produced Yttria-Stabilized Zirconia, YSZ. Various amount of yttrium ions could provide different ionic conductivity. This research investigated electrical conductivity of various YSZ composition, i.e., 4.5; 8.0 and 10% mol yttrium in ZrO2. The ZrO2 powder used was synthesized from zircon sand, a side product of tin mining plant, Bangka Island, Indonesia. Structural investigation on the prepared YSZ found that yttrium ion doping has changed the crystal structure of ZrO2 from monoclinic to cubic, even though the monoclinic and tetragonal are also still exist. The Y3+ doping changed the cell parameter of ZrO2 crystal. It indicates that the Y3+ entered into the ZrO2 structure and produced vacancy sites. The highest ionic conductivity is provided by 8% mol Yttrium doping or 8YSZ, i.e., 2.74×10-4 S.cm-1 at 700oC with an activation energy of 0.741 eV."

"ABSTRAKDimetil eter (DME) adalah salah satu bahan bakar alternatif terbarukan yang dapat menggantikan pemakaian energi fosil di Indonesia. Penggunaan senyawa ini menghasilkan pembakaran yang efisien serta ramah lingkungan. Akan tetapi, dimetil eter diketahui menyebabkan degradasi pada material karet, yang banyak digunakan sebagai sealant ataupun selang pada tempat penyimpanan bahan bakar dari mesin pembakaran. Hingga penelitian ini, setiap jenis material karet mengalami degradasi yang berbeda-beda sehubungan dengan senyawa ini. Oleh karena itu, penelitian ini utamanya ditujukan untuk menentukan jenis degradasi material karet, khususnya karet alam vulkanisat, terhadap dimetil eter. Selain itu, penelitian ini hendak melihat pengaruh komposisi filler dan petroleum oil dari karet alam vulkanisat terhadap degradasi tersebut. Eksperimen yang dilaksanakan mencakup: sintesis, uji degradasi, karakterisasi mekanis dan morfologi. Nilai komposisi filler yang dipakai untuk sintesis yaitu: 10, 30, dan 60 phr; sedangkan nilai komposisi petroleum oil yang dipakai adalah 0, 10, dan 20 phr. Uji degradasi karet alam vulkanisat dilakukan dengan merendam seluruh sampel dalam pressure vessel yang berisi dimetil eter cair, yang diperoleh dari proses pencairan fasa gasnya. Karakterisasi mekanis yang dilakukan mencakup: % perubahan massa, kekuatan tensile, elongasi maksimum, dan kekerasan. Karakterisasi morofologinya berupa pengamatan langsung dan scanning electron microscopy (SEM). Data-data karakterisasi tersebut menunjukkan bahwa karet alam vulkanisat mengalami degradasi jenis absorpsi dan ekstraksi oleh karena dimetil eter. Adapun penambahan komposisi filler ditemukan dapat mengurangi pengaruh degradasi, sedangkan penambahan komposisi petroleum oil justru memperparah degradasi. Namun demikian, petroleum oil juga dibutuhkan karena dapat membuat distribusi filler merata pada seluruh bagian karet alam vulkanisat. Maka dari itu, dengan meninjau keseluruhan data tersebut, didapatkan bahwa komposisi filler dan petroleum oil yang memberikan perlindungan paling optimal terhadap degradasi oleh dimetil eter masing-masing bernilai 30 phr dan 10 phr.

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ABSTRACTDimethyl ether (DME) is one of the renewable energy that could replace the usage of fossil fuel in Indonesia. The usage of this compound could produce efficient and environmental-friendly combustion. However, based on previous research, dimethyl ether is found to cause degradation on rubber-based materials, which are used as sealant or hose inside the fuel tanker of combustion engines. Until this research, it is found that each types of rubber has suffered different kinds of degradation that caused by dimethyl ether. Therefore, the main goal of this research is to determine what kind of degradation will happen on rubber, especially vulcanized natural rubber, that cause by dimethyl ether. Moreover, this research is going to see the effect of filler and petroleum oil composition contained in vulcanized natural rubber against that degradation. There are three parts of experiments will conducted: synthesis, degradation testing, mechanical and morphology characterization. The variation value of filler composition used are 10, 30, and 60 phr; while the variation value of petroleum oil composition are 0, 10, and 20 phr. Degradation testing is done by immersing all samples inside pressure vessel that have been filled with liquid dimethyl ether, which produced from its gas by liquefaction process. Mechanical characterization that observed includes: % change of mass, tensile strength, maximum elongation, and hardness. On the other side, morphology characterization is done by direct observation and scanning electron microscopy (SEM). Those datas reveals that vulcanized natural rubber suffer absorption and extraction, two types of degradation, because of dimethyl ether. Increasing of filler composition could reduce the impact of degradation, while increasing of petroleum oil composition will give the opposite results. However, it is also found that petroleum still must needed to make distribution of filler goes through all parts of rubber. Therefore, based on these datas, we get that 30 phr of filler and 10 phr of petroleum pil will give the optimal protection on vulcanized natural rubber against degradation caused by dimethyl ether."

"Bahan penyerap radar atau Radar Absorbent Material adalah salah satu material maju untuk keperluan teknologi siluman. Penambahan sejumlah kecil clay terhadap komposit Epoksi/E-Glass telah terbukti dapat membuat bahan penyerap gelombang elektromagnetik lebihbaik dibandingkan bahan komposit Epoksi/E-glass. Penelitian ini, yang merupakan kelanjutan dari penelitian sebelumnya mengenai penyerapan gelombang elektromagnetik, bertujuan mempelajari sifat tarik, sifat tekuk, dan permukaan patahan komposit Epoksi/E-glass/Clay.. Empat jenis sampel dibuat, yaitu, komposit Epoksi/E-Glass dan Epoksi/E-Glass/Clay dengan komposisi clay 1 wt%, 3 wt %, dan 5 wt %, yang difabrikasi dengan metode hand lay-up. Berdasarkan hasil uji tarik dan uji tekuk, nilai kuat tarik dan kuat tekuk tertinggi diperoleh pada komposit Epoksi/E-glass/Clay dengan fraksi beratclay 3 wt %, yang berturut-turut kenaikan kuat tarik dan kuat tekuknya sebesar 182,24% dan 23,5% terhadap komposit Epoksi/E-glass/Clay. Sedangkan nilai modulus tarik dan modulus tekuk pada komposit Epoksi/E-glass/Clay dengan fraksi berat clay 3 wt % memiliki nilai 11,5 GPa dan 6,04 GPa secara berturut-turut. Pengamatan permukaan patahan menggunakan Scanning Electrons Microscope menunjukkan jenis-jenis mode kegagalan yang terjadi adalah fiber pull-out, delaminasi, kegagalan matriks, fiber patah, dan keretakan mikro pada matriks. Selain itu, sisa matriks yang cukup banyak di fiber pada komposit Epoksi/E-glass/Clay dibanding komposit Epoksi/E-glass menunjukkan ikatan interfacial yang lebih baik saat sejumlah kecil clay ditambahkan.

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Radar Absorbent Materials are one of new advanced materials to be used in stealth technology. It was an evidence that the addition of a small amount of clay in Epoxy/E-glass composites provided a better electromagnetic wave absorber materials compared to Epoxy/E-glass composites. This research, which was a continuation of the previous research about electromagnetic wave absorption, aimed to study the tensile and flexural properties,as well as the modes failure of Epoxy/E-glass/Clay composites. Four different samples were made; they were Epoxy/E-Glass and Epoxy/E-Glass/Clay with 1 wt %, 3 wt %, and 5 wt % clay loadings. The samples were fabricated with a hand lay-up method. Tensile and flexural test results showed that the highest tensile and flexural strengths were obtained on the Epoxy/E-glass/Clay with 3 wt % clay?s weight fraction, which was increased up to 182,24 % and 23,5 % respectively from the tensile strength and flexural strength of Epoxy/E-glass composites. The tensile and flexural modulus values of Epoxy/E-glass/Clay composites with 3 wt % clay?s weight fraction were 11,3 GPa and 6,04 GPa respectively. An observation of fracture surface using Scanning Electrons Microscope showed that the failure modes that occurred on the fracture surfaces were fiber pull-out, delamination, matrix failure, fiber fracture, and matrix micro-cracks. Moreover, some amount of remaining matrix on the glass fiber at Epoxy/E-glass/Clay composites compared to Epoxy/E-glass composites showed that a better interfacial bond was obtained when a small addition of clay were added."