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"Magnesium-based hydrogen storage alloy is one of the most attractive hydrogen storage materials for fuel cell-powered vehicle application. However, a high desorption temperature and slow kinetics limit its practical application. Extensive efforts are required to overcome these problems, one of which is inserting a metal oxide catalyst. In this work, we reported the current progress of using nano-silica (SiO2) as a catalyst to improve the thermodynamics and kinetics of magnesium hydride (MgH2). Nano-SiO2 was extracted from local rice husk ash (RHA) using the co-precipitation method. Then, the MgH2 was catalyzed with a small amount of nano-SiO2 (1 wt%, 3 wt%, and 5 wt%) and prepared using a high-energy milling technique. The microstructure and hydrogen desorption performance were studied using x-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The results of the XRD test showed that the milling process over 5 h reduced the material to a nanometer scale. Then, SEM images showed that the powders were agglomerated after 5 h of milling. Furthermore, it was also found that nano-SiO2 reduced the hydrogen desorption temperature of MgH2 to 338°C in 14.75 min when the 5 wt% variation of the catalyst was applied."

"Magnesium-based hydrogen storage alloy is one of the most attractive hydrogen storage materials for fuel cell-powered vehicle application. However, a high desorption temperature and slow kinetics limit its practical application. Extensive efforts are required to overcome these problems, one of which is inserting a metal oxide catalyst. In this work, we reported the current progress of using nano-silica (SiO2) as a catalyst to improve the thermodynamics and kinetics of magnesium hydride (MgH2). Nano-SiO2 was extracted from local rice husk ash (RHA) using the co-precipitation method. Then, the MgH2 was catalyzed with a small amount of nano-SiO2 (1 wt%, 3 wt%, and 5 wt%) and prepared using a high-energy milling technique. The microstructure and hydrogen desorption performance were studied using x-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). The results of the XRD test showed that the milling process over 5 h reduced the material to a nanometer scale. Then, SEM images showed that the powders were agglomerated after 5 h of milling. Furthermore, it was also found that nano-SiO2 reduced the hydrogen desorption temperature of MgH2 to 338°C in 14.75 min when the 5 wt% variation of the catalyst was applied."

"Mikroelektroda hydrogenated boron doped diamond (HBDD) dan oxidized boron doped diamond (OBDD) digunakan dalam studi penentuan distribusi ukuran nanopartikel Pt. Studi dilakukan menggunakan teknik kronoamperometri pada potensial tetap 0,516 V dengan mengamati arus transien yang muncul pada reaksi oksidasi hidrogen peroksida 1 mM dalam phosphate buffer solution (PBS) 50 mM sebagai hasil reaksi elektrokatalitik oleh nanopartikel Pt ketika menumbuk permukaan mikroelektroda. Batas minimum arus transien yang dideteksi oleh mikroelektroda HBDD dan OBDD masing-masing adalah 1,5 dan 2,5 nA. Arus transien yang dihasilkan memiliki korelasi dengan ukuran nanopartikel Pt. Ukuran nanopartikel Pt divariasikan dengan cara memvariasikan konsentrasi NaBH4 yang digunakan dalam pembentukan nanopartikel Pt. Hasil TEM menunjukkan bahwa kisaran ukuran nanopartikel Pt dengan variasi konsentrasi NaBH4 60, 90, 120, 150 mM masing-masing sebesar 5,33; 5,01; 4,62; dan 4,24 nm. Sementara itu pengukuran dengan teknik amperometri menggunakan mikroelektroda HBDD masing-masing sebesar 5,39; 5,15; 4,72 dan 4,40 nm, sedangkan menggunakan mikroelektroda OBDD masing-masing sebesar 5,36; 5,07; 4,70; dan 4,31 nm untuk nanopartikel Pt dengan NaBH4 60, 90, 120, 150 mM. Pengujian secara statistik dengan uji T menunjukkan bahwa hasil dengan teknik kronoamperometri diperoleh tidak berbeda secara signifikan dengan metode TEM mengindikasikan bahwa metode ini dapat digunakan untuk menentukan diameter nanopartikel Pt.

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Hydrogenated boron doped diamond (HBDD) and oxidized boron doped diamond (OBDD) microelectrodes were used in studyabout the determination of Pt nanoparticles size distribution. Chronoamperometry technique was used with a constant potential of 0.516 V to observe the transient currents generatedby the oxidation reaction of 1 mM hydrogen peroxide in 50 mM phosphate buffer solution catalyzed by Pt nanoparticles when attached the surface of microelectrode. The minimum limit of the transient current can be detected by HBDD and OBDD microelektrodes were 1.5 and 2.5 nA respectively. The transient current has correlation with the size of the Pt nanoparticles. Size of Pt nanoparticles was varied by the use of different of NaBH4 to synthesize the nanoparticles.

TEM results showed that the Pt nanoparticles with distribution size of 5.33; 5.01; 4.62; and 4.24 nm, respectively, could be synthesized by using NaBH4 concentrations of 60, 90, 120, 150 mM. On the other hand, the chronoamperomethry techniques using HBDD microelectrode showed Pt nanoparticles size distributions 5.39; 5.15; 4.72; and 4.40 nm, while using OBDD microelectrode showed 5.36; 5.07; 4.70; and 4.31 nm for Pt nanoparticles with NaBH4 concentrations of 60, 90, 120, 150 mM respectively. Statistic examination using T-test resulted no significant differences between the results using amperometry techniques and TEM, indicates that the method using both HBDD and OBDD microelectrodes can be used for the determination of Pt nanoparticle diameter."

"Baja Oxide Dispersion Strengthened (ODS) merupakan jenis baja yang diperkuat oleh dispersi oksida. Salah satu oksida yang dapat didispersikan adalah yttria (Y?O?). Pencampuran bahan prekursor dilakukan menggunakan metode metalurgi serbuk. Proses pemaduan mekanik dengan penggilingan (milling), utamanya sangat dipengaruhi waktu. Penelitian ini bertujuan untuk mengetahui pengaruh waktu milling terhadap ukuran butir dan pembentukan fasa austenitik pada serbuk prekursor FeNiCr - Y?O? dengan variasi waktu 10, 20 dan 30 jam. Planetary Ball Mill dengan parameter proses: ball to powder ratio (BPR) 12:1 dan frekuensi putar 25 hz digunakan untuk menggiling serbuk prekursor. Karakterisasi dilakukan dengan mikroskop elektron (SEM-EDS) dan difraksi sinar-X (XRD) untuk mengamati ukuran butir dan fase yang terbentuk. Hasil analisis menunjukkan bahwa analisis pola difraksi hanya menunjukkan fasa kristal ?-Fe (BCC) dan Nikel (FCC). Meskipun fasa austenitik tidak terbentuk, semakin lama waktu milling, ukuran butir rata-rata serbuk prekursor FeNiCr- Y?O? semakin kecil.

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Oxide Dispersion Strengthened (ODS) steel is a type of steel strengthened by oxide dispersion. One of the oxides that can be dispersed is yttria (Y?O?). Mixing of precursor materials is carried out using the powder metallurgy method. The process of mechanical alloying by milling is mainly influenced by time. This study aims to determine the effect of milling time on grain size and austenitic phase formation in FeNiCr - Y?O? precursor powders with time variations of 10, 20 and 30 hours. Planetary Ball Mill with process parameters: ball to powder ratio (BPR) 12:1 and rotating frequency 25hz was used to grind the precursor powder. Characterization was performed by electron microscopy (SEM-EDS) and X-ray diffraction (XRD) to observe the grain size and phases formed. The results showed that the diffraction pattern analysis showed only ?-Fe (BCC) and Nickel (FCC) crystal phases. Although the austenitic phase is not formed, the longer the milling time, the smaller the average grain size of the FeNiCr- Y?O? precursor powder."

"Indonesia memiliki potensi besar dalam memproduksi silikon karena memiliki deposit pasir silika yang melimpah di seluruh wilayahnya. Belum ada industri di Indonesia yang mampu mereduksi silika menjadi silikon. Hingga saat ini metode yang umum digunakan untuk mereduksi pasir silika menjadi silikon adalah dengan menggunakan metode karbotermik. Alternatif metode reduksi yang dapat digunakan di antaranya adalah metode reduksi magnesiotermik yang mampu menurunkan kebutuhan temperatur menjadi pada kisaran 500-950℃. Metode ini dilakukan dengan mereaksikan pasir silika (SiO2) dengan magnesium (Mg) pada temperatur terkontrol. Penelitian ini dilakukan dengan melakukan magnesiotermik terhadap sampel Mg-Si dalam bentuk serbuk padat dalam tungku selama 4 jam dan variasi temperatur 600℃, 700℃, dan 800℃. Sampel hasil pembakaran kemudian dilakukan pelindian menggunakan larutan HCl 6M di atas magnetic stirrer dengan kecepatan 650rpm dan suhu 80℃ selama 4 jam. Hasil pelindian kemudian disaring dan sampel dikarakterisasi menggunakan XRD, XRF, dan SEM-EDS. Data XRF yang menunjukkan adanya keberadaan silikon dalam sampel akhir mengindikasikan berhasilnya proses reduksi. Karakterisasi XRD pada sampel akhir menunjukkan kadar silikon dan bahwa temperatur optimum untuk mereduksi pasir silika adalah 600℃ dengan silikon 65,3%. Kemudian dengan didukung pengujian SEM-EDS, variabel temperatur 600℃ memiliki kehalusan lebih tinggi dan tingkat homogenitas tertinggi secara visual dibandingkan dengan hasil mikrostruktur sampel lainnya.

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Indonesia has great potential in silicon production due to abundant deposits of silica sand throughout the country. However, the processing of silica sand into silicon for solar cell applications is still rare in Indonesia due to the high energy requirement of the process. Currently, the most common method used to reduce silica sand into silicon is the carbothermic method. An alternative reduction method that can be used is the magnesiothermic reduction method, which can significantly lower the temperature required to the range of 500-950°C. This method involves the reaction of silica sand (SiO₂) with magnesium (Mg) at controlled temperatures. This research focuses on conducting magnesiothermic reduction on Mg-Si samples in the form of solid powder in a furnace for 4 hours at various temperatures of 600°C, 700°C, and 800°C. The resulting burned samples are then subjected to leaching using a 6M HCl solution with the assistance of a magnetic stirrer operating at 650 rpm and a temperature of 80°C for 4 hours. The leached samples are subsequently filtered and characterized using XRD, XRF, and SEM-EDS techniques. The XRF data indicates the presence of silicon in the final sample, indicating the success of the reduction process. XRD characterization of the final sample reveals the silicon content, and the optimum temperature for reducing silica sand is found to be 600°C silicon content of 65.3%. Supported by SEM-EDS analysis, the 600°C temperature variable exhibits higher fineness and the highest level of visual homogeneity compared to other sample microstructures."

"Pengetahuan mengenai manfaat klinis kadar magnesium serum baru dimulai akhir-akhir ini sering dengan adanya analisis dan penemuam bahwa kadar magnesium abnormal pada gangguan kardiovaskuler,metabolik dan neuromuskuler."

"Pengetahuan mengenai manfaat klinis kadar magnesium serum baru dimulai akhir-akhir ini setting dengan adanya analisis dan penemuan bahwa kadar magnesium abnormal pada gangguan kardiovaskuler, metabolik dan neuromuskuler. Meskipun kadarnya di serum lidak menggambarkan kadar magnesium tubuh, tetapi saat ini yang dikenal Iuas penggunaannya hanya pemeriksaan kadar magnesium serum. Magnesium eritrosil saat ini dinilai lebih sensitif dari pada magnesium serum, karena magnesium eritrosit dapat mewakili penilaian status magnesium intrasel. Menurun NCCLS (National Committee for Clinical Laboratory Standards) setiap laboratorium dianjurkan memiliki nilai rujukan sendiri untuk pemeriksaan yang dikerjakannya, termasuk juga pemeriksaan magnesium. Nilai rujukan yang didapat sesuai dengan populasi dan dipengaruhi oleh metode serta teknik pemeriksaan. Penelitian ini bertujuan untuk menidapatkan nilai rujukan magnesium dalamn serum dan plasma serta mendapatkan nilai rujukan magnesium intrasel yaitu magnesium eritrosit dengan metode pemeriksaan langsung dan mengtlahui perbandingan hasil pemeriksaan antara magnesium serum dengan plasma. Bahan darah diambii dari 114 peserta donor darah di Unit Transfusi Darah Daerah (UTDD) Budhyarto PMl DKl Jakarta, terdiri dari 57 orang pria dan 57 orang wanita berusia antara 17-65 tahun, secara klinis sehat menurut kriteria donor darah PMl. Darah diambii dari selang blood set, langsung dimasukkan 4 mL ke dalam tabling vakum tanpa antikoagulan untuk pemeriksaan magnesium serum dan 3 mL kedalam tabling vakum dengan antikoagulan lithium heparin untuk pemeriksaan magnesium eritrosit dan plasma. Penetapan kadar magnesium dilakukan dengan alat kimia klinis olomatis Hitachi 912 dengan metode Xylidil Blue dengan prinsip kolorimetri.Pada penelitian ini didapatkan tidak ada perbedaan bermakna untuk hasil pemeriksaan magnesium ekstrasel memakai bahan serum maupun plasma heparin. Nilai rujukan untuk magnesium serum atau plasma adalah 1.30 - 2.00 mEtq/L dan magnesium eritrosit adalah 4.46-7.10 mEq/L. (Med J Iiidones 2006; 15:229-235).

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The interest in the clinical importance of serum magnesium level has just recently begun with the analysis and findings of abnormal magnesium level in cardiovascular, metabolic and neuromuscular disorder. Although the serum level does not reflect the body magnesium level, but currently, only serum magnesium determination is widely used. Erylhrocyte magnesium is considered more sensitive than serum magnesium as it reflects intracelhdar magnesium status. According to NCCLS (National Committee for Clinical Laboratory Standards) every laboratory is recommended to have its own reference range for the tests it performs, including magnesium determination. The reference range obtained is appropriate for the population and affected by the method and technique. This study aimed to find the reference range of serum and plasma magnesium and also intracelhdar magnesium i.e. erythrocyte magnesium by direct method, and compare the results of serum and plasma magnesium. Blood was taken from 114-blood donor from Unit Transfusi Darah Daerah (UTDD) Budhyarto Palang Merah Indonesia (PMl) DKl Jakarta, consisted of 57 male and 57 female, aged 17 - 65 years, clinically healthy according to PMl donor criteria. Blood was taken from blood set, collected into 4 ml vacuum tube without anticoagulant for serum magnesium determination and 3 ml vacuum tube with lithium heparin for determination of erythrocyte and plasma magnesium Determination of magnesium level was performed with clinical chemistry auto analyzer Hitachi 912 by Xylidil Blue method color/metrically. This study showed no significant difference between serum and heparinized plasma extra cellular magnesium. The reference range for serum or plasma magnesium was 1.30 - 2.00 mEq/L and for erythrocyte magnesium was 4.46 - 7.10 mEq/L (MedJIndones 2006; 15:229-35)."

"Proses elektrolisis temperatur tinggi telah diaplikasikan untuk mendapatkan bubuk magnesium dari hidromagnesit dan magnesium oksida sebagai material umpan. Dalam proses elektrolisis, garam MgCl2 hidrat dipanaskan hingga 750 °C - 850 °C hingga menjadi lelehan elektrolit. Beda tegangan antara elektroda sebesar 0 - 12 V diberikan untuk mendapatkan bubuk magnesium. Ditemukan bahwa bubuk magnesium terbentuk pada katoda Pt sebagaimana warna dari lelehan garam berubah dari putih menjadi abu-abu seperti warna Mg. Pembentukan Mg juga diindikasikan dengan kenaikan arus pada pembacaan amperemeter. Sayangnya, proses dilakukan pada kondisi udara terbuka dan kemudian bubuk Mg segera teroksidasi menjadi bubuk MgO. Disimpulkan meskipun tidak ada bukti puncak-puncak difraksi dari Mg pada pola XRD dari sampel, bubuk Mg berhasil dihasilkan selama proses. Kata kunci: elektrolisis, magnesium.

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High temperature electrolysis process has been applied to obtain magnesium powders from hydromagnesite and magnesium oxide as the feed materials. In the electrolysis process, hydrat MgCl2 salts were heated to 750 °C - 850 °C towards molten electrolyte. Voltage between electrodes of 0 - 12 V was then applied for obtaining Mg powders. It was found that Mg powders formed in the Pt cathode as color of molten salts changed from white to grey which is similar to that of Mg. Formation of Mg was also indicated by a current rise as read in amperemeter. Unfortunately, the process was carried out under open atmosphere and thus Mg powders were immediately oxidized to MgO powders. It is concluded that despite no evidence of diffraction peaks for Mg in XRD pattern of the sample, the Mg powders were successfully produced during process. Keywords: electrolysis, magnesium."

"Dalam penatalaksanaan trauma maksilofasial diperlukan material implan sampai terjadi penyembuhan tulang. Magnesium memiliki potensi sebagai material implan tulang, dengan syarat memiliki laju biodegradasi yang baik. Proses equal channel angular pressing (ECAP) merupakan salah satu metode untuk memperbaiki sifat biodegradasi dari material logam.Tujuan: Mengkaji proses biodegradasi magnesium ECAP pada cairan fisiologis.Metode: Laju biodegradasi dan tingkat evolusi hidrogen didapatkan dari uji perendaman pada larutan DMEM dengan metode weight loss dan spektrometri dengan menggunakan dua belas spesimen magnesium ECAP dan enam spesimen magnesium murni sebagai kontrol. Pola biodegradasi didapatkan dari analisis struktur permukaan mikro. Analisis data menggunakan uji T independen.Hasil: Terdapat perbedaan yang signifikan antara laju biodegradasi dan tingkat evolusi hidrogen antara magnesium ECAP dengan magnesium murni. Magnesium ECAP memiliki pola biodegradasi yang homogen.Kesimpulan: Magnesium ECAP memiliki laju biodegradasi dan tingkat evolusi hidrogen yang lebih baik dibandingkan dengan magnesium murni.

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Implant material are used in the management of maxillofacial trauma until bone healing occur. Magnesium has the potential to be a bone implant material, but it requires a good biodegradation rate. The process of equal channel angular pressing (ECAP) is a method to improve the biodegradation properties of metallic materials.

Purpose: To observe the biodegradation process of magnesium ECAP in physiological fluid.

Method: The biodegradation and hydrogen evolution rate were obtained from immersion test in a DMEM solution, using weight loss and spectrometric method within twelve magnesium ECAP specimens and six specimens of pure magnesium as a control. Biodegradation pattern were obtained from the micro surface structures analysis. The result was statistically analyzed with independent T test.

Results: There were significant difference between the biodegradation and hydrogen evolution rate between magnesium ECAP and pure magnesium. Magnesium ECAP has a homogeneous biodegradation pattern.

Conclusion: Magnesium ECAP has better biodegradation and hydrogen evolution rate than pure magnesium."

"Magnesiummerupakan suatu material yang berpotensi digunakan sebagai biomaterial logam yang dapat terdegradasi. Syarat magnesium dapat digunakan sebagai material implan biodegradable adalah laju degradasimagnesiumharus sesuaidenganlaju penyembuhandarijaringan yang terlibat.Umumnya magnesium memiliki laju degradasi yang cepat, hal ini merupakan kekurangan magnesium yang tidak diinginkan.Aplikasimagnesiumsebagai implanyang terdegradasiterhambatkarena tingkattinggidegradasilingkungan fisiologisdan kerugiankonsekuen dalamsifat mekanik. Oleh karena itu, proses Equal Channel Angular Pressing (ECAP) yang dilakukan padamagnesium diharapkan akanmengurangiukuran butir yang dapat menurunkanlaju degradasidan meningkatkansifat mekanis magnesium.Tujuan: Menganalisasifat mekanismagnesium ECAP dalam cairan fisiologis.Metode:Sifat mekanis magnesium ECAP dianalisis setelah dilakukan perendaman dalam larutan DMEM dengan menggunakan masing-masing sepuluh sampel magnesium ECAP dan lima sampel magnesium untuk uji tarik dan uji kekekrasan. Sifat mekanis di analisis menggunakan nilai ultimate tensile strength (UTS) pada uji tarik dan vickers hardness number (VHN) pada uji kekerasan.Hasil: Kekuatan dan kekerasan magnesium meningkat setelah proses ECAP.

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Magnesium has thepotential to be used asdegradable metallic biomaterial. For magnesium to be used as biodegradable implant materials, their degradation rates should be consistent with the rate of healing of the affected tissue, the release of the degradation products should be within the body?s acceptable absorption levels. Conventional magnesium degrades rapidly, which is undesirable. The successful applications of magnesium as degradable implants are mainly inhibited due to their high degradation rates in physiological environment and consequent loss in the mechanical properties. Equal channel angular pressing (ECAP) was applied to a pure magnesium. This processes will be decreasing grain size, decreasing degradation rates and increasing mechanical properties.

Purpose: To analyze the mechanical properties of magnesium ECAP in physiological fluid.

Method:The mechanical properties were obtained from immersion test in a DMEM solution, within ten magnesium ECAP specimens and five specimens of pure magnesium as a control. Mechanical properties were analyzed using the value of ultimate tensile strength (UTS) with tensile testing and vickers hardness number (VHN) with hardness testing.

Results:The ultimate tensile strength and hardness magnesium increased after ECAP, and the mechanical properties of the magnesium ECAP decreased in physiological fluid."