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"Manganite perovskite has a wide variety of potential applications as an advanced material, for example, in magnetic random access memory, spintronics, magnetoelectric, magnetic field sensors and cooling technology, based on magnetism and magnetic materials. In work on cooling technology, magnetic materials show a magnetocaloric effect. Manganite perovskite has some fundamental properties, such as Curie temperature, magnetic entropy change, temperature span and relative cooling power. Current works report detailed properties of manganite perovskite in La0.7Ca0.3MnO3 doped with Cu, which show magnetocaloric effects. The samples were synthesized by a conventional solid state reaction. A small amount of doping Cu 1%~3% at a Mn site maintains the First-Order Magnetic Transition (FOMT) without leading into the Second-Order Magnetic Transition (SOMT). Maximum magnetic entropy change increased as the Cu-doped decreased. Introducing a small percentage of Cu-doped on La0.7Ca0.3Mn1-xCuxO3 also implies decreasing the Curie temperature, TC. For all samples under external application in a field of 10 kOe, these resulted in a slightly wider temperature span and the Relative Cooling Power (RCP) of about 39 J/kg to 47 J/kg as the Cu-doped decreased. The small amount of Cu-doping on La0.7Ca0.3MnO3 keeps the rate of relative cooling power in a wider temperature range. It may be beneficial for cooling technology based on magnetism and magnetic materials."

"Modern technology for refrigerators and coolers is based on the chemical gas Chlorofluorocarbon (CFC) compression method that is indicative of a high consumption of electricity. The CFC is also understood as a reason for global warming. One of the solutions to this issue is magnetic refrigeration technology, which is environmentally friendly because it does not use any hazardous chemicals or ozone depleting/greenhouse gases. Magnetic refrigeration technology is based on the magnetocaloric effect of magnetic refrigerant materials. Exploring the magnetocaloric effect of magnetic refrigerant materials is important because these contain many of the physical properties needed for magnetic refrigeration technology. Herein, the present work reports on the magnetocaloric effect of La0.7Ca0.3Mn1?xSnxO3 (x = 0.0, x = 0.02 and x = 0.04) compound samples produced with the solid state reaction technique. Curie temperature TC obtained for the La0.7Ca0.3Mn1?xSnxO3 (x = 0.0, x = 0.02 and x = 0.04) are 260 K, 176 K and 170 K with -?SM max of 4.32 J×kg-1×K-1, 1.61 J×kg-1×K-1 and 1.24 J×kg-1×K-1 and a refrigerant capacity of 48 J/kg, 41.43 J/kg and 28.53 J/kg for x = 0.0, x = 0.02 and x = 0.04, respectively. A small addition of Sn-doped resulted in a significant decrease of more than 80 K on the Curie temperature scale compared to that of La0.7Ca0.3MnO3. The large gap in the decreasing magnetic temperature phase transition might be useful as an option of metal/transition metal doped for tuning the Curie temperature of magnetic refrigerant materials."

"Telah dilakukan sintesa B4C dengan cara mengubah komposisi asam sitrat dan karbon aktif dari suatu komposisi tertentu yang telah diketahui sebelumnya. Untuk pencampuran digunakan ballmill. Karakterisasi dilakukan dengan menggunakan XRD dan FTIR. Hasil XRD memperlihatkan bahwa dengan penambahan asam sitrat, jumlah B4C yang terbentuk naik dan dengan penambahan karbon aktif, jumlah B4C relatif turun sedikit. Data FTIR menunjukkan bahwa penambahan asam sitrat maupun karbon aktif memperlihtakan adanya ikatan-ikatan B - C. Bila dibandingkan dengan data XRD maupun FTIR dari B4C Aldrich, telah terbentuk dengan baik B4C.

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It has been synthesized B4C by varying citric acid and activated carbon from predetermined composition. Material mixing was done by ballmill. Characterizations of the samples were done by means of XRD and FTIR. XRD diagram showed that B4C increased by increasing citric acid and by increasing activated carbon the number of B4C decreased. FTIR data showed that by increasing citric acid or activated carbon, the bond B - C appeared. By comparing data from B4C Aldrich, the samples showed similarity."