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All Journal Science and Technology Indonesia Jurnal Elektronika dan Telekomunikasi Makara Journal of Science
Tony Kristiantoro, Tony
Pusat Penelitian Elektronika dan Telekomunikasi - LIPI
Biochemistry, Genetics & Molecular Biology Chemical Engineering, Chemistry & Bioengineering Electrical & Electronics Engineering Engineering Environmental Science Materials Science & Nanotechnology Physics

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Ketidakpastian Pengukuran pada Karakteristik Material Magnet Permanen dengan Alat Ukur Permagraph Kristiantoro, Tony; Idayanti, Novrita; Sudrajat, Nanang; Septiani, Ardita; Mulyadi, Dadang; -, Dedi
Jurnal Elektronika dan Telekomunikasi Vol 16, No 1 (2016)
Publisher : Indonesian Institute of Sciences

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (451.698 KB) | DOI: 10.14203/jet.v16.1-6

Abstract

Telah dilakukan perhitungan nilai ketidakpastian pengukuran pada karakteristik material magnet permanen menggunakan alat ukur Permagraph Magnet Physik Germany. Karakteristik magnet yang diukur adalah induksi remanen, Br (kG), gaya koersifitas induksi, HcB (kOe), gaya koersifitas polarisasi, HcJ (kOe), kuat medan remanen kiri, Hknee (kOe), produk energi maksimum, BHmax (MGOe), kuat medan produk energi maksimum, Ha (kOe), magnetik fluks, Ba (kG), kuat medan maksimum, Hmax (kOe). Sebelum menentukan nilai ketidakpastian dengan permagraph terlebih dahulu ditentukan nilai ketidakpastian dengan alat penunjang, yaitu jangka sorong dan neraca analitik. Selanjutnya akan didapat nilai ketidakpastian gabungan. Metoda ketidakpastian yang digunakan adalah dengan cara statistik dan berlaku hanya untuk serangkaian observasi. Penentuan nilai ketidakpastian dilakukan dengan cara melakukan pengukuran yang berulang sebanyak sepuluh kali terhadap sample yang sama. Metoda ini mengacu kepada ISO GUM dengan menggunakan evaluasi tipe A. Nilai ketidakpastian yang didapat untuk pengukuran dengan jangka sorong adalah ±0,0329 cm, neraca analitik ±0,0528 gr, dan untuk karakteristik magnet Br ±0,0648 kG, HcB ±0,0632 kOe, HcJ ±0,0628 kOe, Hknee ±0,0643 kOe, BHmax ±0,0631 MGOe, Ha ±0,1213 kOe, Ba ±0,0664 kG,Hmax ±0,0627 kOe. 
Aplikasi Magnet Berpengikat (Bonded) NdFeB untuk S-band Circulator pada Rentang Frekuensi 2,00-4,00 GHz Kristiantoro, Tony; Idayanti, Novrita
Jurnal Elektronika dan Telekomunikasi Vol 14, No 2 (2014)
Publisher : Indonesian Institute of Sciences

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (538.021 KB) | DOI: 10.14203/jet.v14.51-55

Abstract

Circulator merupakan perangkat elektronik yang memiliki fungsi penting pada suatu sistem pemancar dan penerima gelombang frekuensi radio (RF), di mana magnet permanen dapat berfungsi sebagai pengarah gelombang (waveguide). Penelitian ini bertujuan untuk menggantikan magnet permanen barium ferit (BaFe12O19) yang umumnya digunakan pada circulator dengan magnet permanen berpengikat (bonded) neodymium besi boron (NdFeB). Bahan baku yang digunakan adalah serbuk NdFeB crashed ribbon dengan menggunakan metode pengepresan green-compact yang divariasikan pada tekanan 25, 50, 75, dan 100 kg.cm-2 dan dilanjutkan proses pemanasan pada temperatur 200 C selama 60 menit. Karakterisasi sifat magnet dilakukan dengan Permagraph, diperoleh nilai intrinsik optimum dari sampel 100 kg.cm-2 , induksi remanen (Br) = 5,37 kG, koersifitas (HcJ) = 4,74 kOe, produk energi maksimum (BHmax) = 2,39 MGOe, dan densitas (ρ) = 4,89 gr.cm-3 . Hasil pengukuran kuat medan permukaan (B) dengan Gauss-meter menunjukkan nilai 800 G. Magnet dengan karakteristik optimum diterapkan pada circulator kemudian dikarakterisasi dengan Vector Network Analyzer dan menghasilkan voltage standing wave ratio (VSWR) = 1,354, isolasi = -17,165 dB dan kerugian penyisipan = -0,200 dB pada titik kerja 3,00 GHz, sehingga magnet berpengikat (bonded) NdFeB ini dapat diterapkan pada S-band circulator yang bekerja pada rentang frekuensi 2,00-4,00 GHz.
First-Principles Calculations of Thermoelectric Properties of Fe-Based Full- Heusler Fe2CuSi Nurlaela, Ai; Nanto, Dwi; Azhar, Anugrah; Yuniarti, Elvan; Kristiantoro, Tony; Dedi, Dedi
Makara Journal of Science Vol. 28, No. 3
Publisher : UI Scholars Hub

Show Abstract | Download Original | Original Source | Check in Google Scholar

Abstract

A first-principle study using density functional theory (DFT) and Boltzmann transport was conducted to evaluate the thermoelectric (TE) properties of an Fe-based full-Heusler alloy. The compound studied is Fe2CuSi with a Cu2MnAl-type structure. The electronic properties of Fe2CuSi were obtained using DFT calculations by running the Quantum ESPRESSO (QE) package. By contrast, TE properties, including electron thermal conductivity, electric conductivity, and Seebeck coefficient, were computed using a semi-empirical Boltzmann transport model solved through the BoltzTraP software at 50–1,500 K temperature range. The spin-orbit coupling effect on these properties was also evaluated, demonstrating notable effects on the results. Multiple electronic bands crossing the Fermi level for both spin directions were confirmed by the density of state curve, indicating the metallic behavior of Fe2CuSi. The magnitude of the figure of merit was determined by the Seebeck coefficient, electric conductivity, and electron thermal conductivity. In this study, the maximum dimensionless figure of merit was 0.027, reached at 1,000 K for the spin-down channel.
Significant Reduction in Lattice Thermal Conductivity of (PbTe)0.95 - (PbS)0.05 Thermoelectric Materials Through Liquid Silicon Quenching Ginting, Dianta; Nurlela, Ai; Nanto, Dwi; Mashadi; Sudiro, Toto; Kristiantoro, Tony; Rhye, Jong-Soo
Science and Technology Indonesia Vol. 10 No. 4 (2025): October
Publisher : Research Center of Inorganic Materials and Coordination Complexes, FMIPA Universitas Sriwijaya

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.26554/sti.2025.10.4.1087-1095

Abstract

Thermoelectric materials are game-changers, that have the ability to transform waste heat into electrical energy, making them a potential renewable energy solution to reduce reliance on fossil fuels. The standard metric for evaluating thermoelectric materials is the dimensionless figure of merit, ZT, which is markedly influenced by lattice thermal conductivity (ĸl ). Higher thermal transport through the lattice lowers the ZT value, reducing the material’s efficiency. Therefore, finding ways to decrease ????l is critical for boosting thermoelectric performance. In our research, we explored an innovative approach by applying a quenching technique using liquid silicon to reduce thermal conductivity (ĸT ) due to lattice vibrations. We compared the lattice conductivity (ĸl ) of materials with and without this liquid silicon quenching process. The results were striking: at 300 K, quenching lowers the lattice thermal conductivity by about 40.1 %, and at 800 K, it is still reduced by roughly 24.7%compared with pristine PbTe. Even more impressive, when compared to non-quenched (PbTe)0.95 − (PbS)0.05 alloys, at 300 K, the silicon-quenched sample attains an additional ĸl reduction of roughly 16.1 %, while at 800 K the extra decrease is about 13.0%. These findings highlight that liquid silicon quenching is a highly effective method for lowering ĸl of PbTe thermoelectric materials. This approach paves the way for developing next-generation thermoelectric materials that are more efficient, particularly for eco-friendly waste heat recovery applications. Our work opens new possibilities for sustainable energy innovation.
Co-Authors -, Dedi Azhar, Anugrah Dedi Dedi Dwi Nanto, Dwi Ginting, Dianta Mashadi Mulyadi, Dadang Nanang Sudrajat, Nanang Novrita Idayanti Nurlaela, Ai Nurlela, Ai Rhye, Jong-Soo Septiani, Ardita Toto Sudiro Yuniarti, Elvan