Judul: Synthesis and Characterization of Fluorapatite with Variations in Sintering Temperature Based on Rice Snail Shells Using the Precipitation Method
Abstrak: Kerusakan pada gigi merupakan salah satu contoh kurangnya unsur kalsium pada tubuh kita, karena kalsium berperan dalam perkembangan tulang dan gigi. Cangkang keong sawah dapat digunakan sebagai prekursor untuk pembentukan fluorapatit (FAp). Penelitian ini bertujuan menyintesis dan mengkarakterisasi FAp dari cangkang keong sawah dengan metode presipitasi serta mengetahui pengaruh variasi suhu sintering. Metode penelitian ini dilakukan melalui tahapan preparasi cangkang keong sawah, Sintesis FAp dengan variasi suhu sintering (600 °C, 800 °C, dan 1000 °C) dengan metode presipitasi. Hasil sintesis FAp dikarakterisasi dengan X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) serta Scanning Electron Microscope Energy Dispersive X-Ray (SEM-EDX). Hasil penelitian menunjukkan bahwa fluorapatit yang disintering dengan suhu 1000 °C memiliki nilai kristalinitas yang paling tinggi berdasarkan hasil XRD. Spektrum FTIR dari FAp suhu 1000 °C diidentifikasi memiliki gugus -OH, OH-F, dan -PO43-. Hasil analisis SEM-EDX menunjukkan fluorapatit dengan suhu 1000 °C memiliki bentuk seperti batang dan jarum serta memiliki rasio molaritas Ca/P sebesar 13,18 dan P/F sebesar 4,29., Synthesis and Characterization of Fluorapatite with Variations in Sintering Temperature Based on Rice Snail Shells Using the Precipitation Method. Supervised by IRMA HERAWATI SUPARTO and CHARLENA Tooth decay is an example of a lack of calcium in our bodies, because calcium plays a role in the development of bones and teeth. Rice snail shells can be used as a precursor for forming fluorapatite (FAp). This study aims to synthesize and characterize FAp from rice field snail shells using the precipitation method and to determine the effect of variations in sintering temperature. This research method was carried out through the stages of preparation of rice snail shells, FAp synthesis with various sintering temperatures (600 °C, 800 °C, and 1000 °C) with the precipitation method. The results of the FAp synthesis were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) and Scanning Electron Microscope Energy Dispersive X-Ray (SEM-EDX). The results showed that fluorapatite sintered at 1000 °C had the highest crystallinity value based on XRD results. The FTIR spectrum of FAp at 1000 °C was identified as having -OH, OH-F, and -PO43- groups. The results of SEM-EDX analysis showed that fluorapatite at a temperature of 1000 °C had a shape like rods and needles and had a Ca/P molarity ratio of 13.18 and P/F of 4.29.
Keyword: Fluorapatite, Crystallinity, Precipitation, Rice Fields Snail Shell

Judul: Variation of Sintering Temperature in the Synthesis of Fluorapatite Made from Snail Shells (Achatina fulica) Using the Sol-Gel Method
Abstrak: Karies gigi dapat menyebabkan gigi berlubang, keropos, bahkan patah. Perlu adanya penanganan terhadap karies gigi berupa pencabutan dan penggantian gigi alami dengan implan. Fluorapatit dapat digunakan sebagai bahan implan gigi. Fluorapatit dapat disintesis menggunakan bahan dasar cangkang bekicot. Cangkang bekicot memiliki kandungan kalsium karbonat sebesar 98%. Penelitian ini bertujuan mengidentifikasi karakteristik fluorapatit dan mengetahui pengaruh variasi suhu sintering pada sintesis fluorapatit berbahan cangkang bekicot dengan metode sol gel. Variasi suhu sintering yang digunakan, yaitu 700, 900, dan 1100 °C. Hasil penelitian menunjukkan fluorapatit yang disintering pada suhu 900 °C memiliki hasil terbaik. Fluorapatit 900 °C memiliki persentase kristalinitas tertinggi berdasarkan hasil spektrum XRD sebesar 83% dengan fase apatite pada sudut 31,8126°, ukuran kristal 79 nm, dan ukuran partikel 0,5 µm. Analisis FTIR pada fluorapatit 900 °C menunjukkan adanya gugus fungsi OH, OH-F, dan PO43-. Fluorapatit 900 °C menunjukkan morfologi seperti bunga karang dengan bunga berbentuk heksagonal dan rasio molaritas Ca/P sebesar 1,67., Dental caries can cause cavities, porous, and even broken teeth. There is a need for the treatment of dental caries in the form of extraction and replacement of natural teeth with implants. Fluorapatite can be used as a dental implant material. Fluorapatite can be synthesized from snail shells. A snail shell contains 98% calcium carbonate. This study aims to identify the characteristics of fluorapatite and determine the effect of variations in sintering temperature on the synthesis of fluorapatite made from snail shells using the sol-gel method. Variation of sintering temperature used is 700, 900, and 1100 °C. The results showed that fluorapatite synthesized with the sintering temperature of 900 °C had the highest crystallinity based on the results of the XRD spectrum of 83% with the apatite phase at an angle of 31,8126%, crystal size of 79 nm, and particle size of 0,5 µm. FTIR analysis on the sample showed the presence of OH, OH-F, and PO43- functional groups. The sample showed a spongy surface morphology with hexagonal-shaped flowers. A Ca/P molarity ratio of 1,67.
Keyword: cangkang bekicot, fluorapatit, implan gigi, kristalinitas, sol gel

Judul: Penentuan Nilai Eigen dan Vektor Eigen dari Matriks Tridiagonal 2-Toeplitz dengan Pendekatan Polinomial Chebyshev
Abstrak: The eigenvalues and eigenvectors of a matrix can be determined by finding its characteristic polynomials. The characteristic polynomials of a tridiagonal 2-Toeplitz matrix is shown to be closely connected to polynomials which satisfy the Chebyshev recurrence relationship. If the order of the matrix is odd, then the eigenvalues are found explicitly in terms of the Chebyshev zeros and the eigenvectors are found in terms of the polynomials satisfying the recurrence relationship. For even ordered matrices, the situation is more complicated. The problem in these cases is that although the Chebyshev recurrence formula is still applied, its initial values are not generating Chebyshev polynomials
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