A CHEMICAL ROUTE TO THE SYNTHESIS OF Bi1-xMgxFeO3 (x=0.1 and x=0.07) NANOPARTICLE WITH ENHANCED ELECTRICAL PROPERTIES AS MULTIFERROIC MATERIAL

Bismuth ferrite (BiFeO3) is one of multiferroic material group, but it is difficult to produce BiFeO3 in single phase as multiferroic material because it occurs leakage of current arising from non stoichiometric. So, to minimize it, it has already been engineering processed to synthesis BiFeO3 doped by Mg to produce Bi0.9Mg0.1FeO3 and Bi0.93Mg0.07FeO3. It used sol-gel method to produce the ceramics. The result of TGA/DTA(Thermo Gravimetric Analysis/Differential Thermal Analysis) test shows that the temperature of calcination is about of 150 and 175oC and temperature of sintering is about of 650oC. Characterization of the powder has already been done by using X-Ray Diffraction (XRD) test and electrical properties test. The results of XRD test show that the powder of Bi0.9Mg0.1FeO3has minimum impurities with total oxide of 6.9% (bismite 3.5% and silenite 3.4%) at calcination temperature of 175oC for 4 hours and sintering at 650oC for 6 hours. Meanwhile at same parameter, Bi0.93Mg0.07FeO3 has more oxide phases with total oxide of 14.5% which consists of silenite (2.5%) and Bi2O4 (12%). Presence of oxide phases could cause leakage of current decreasing electrical properties. The values of electrical saturation polarization for ceramic having minimum total oxide (Bi0.9Mg0.1FeO3) is higher than ceramic having more oxide (Bi0.93Mg0.07FeO3). The value of electric saturation polarization for Bi0.9Mg0.1FeO3 is of 0.26 kv/cm and for Bi0.93Mg0.07FeO3 is of 0.11 kV/cm.

Pengendapan Uranium dan Thorium Hasil Pelarutan Slag II

Proses peleburan timah menghasilkan limbah berupa slag II dalam jumlah besar. Slag II sebagai terak pada proses peleburan timah masih mengandung beberapa unsur utama antara lain 0,0619% uranium, 0,530% thorium, 0,179% P2O5, dan 6,194% logam tanah jarang (LTJ) oksida total. Berdasarkan fakta tersebut, maka sangat menarik untuk meneliti pengolahan slag II, terutama untuk memisahkan uranium dan thorium yang terkandung di dalamnya. Uranium dan thorium dilarutkan dengan pelarut asam (H2SO4). Recovery pelarutan slag II dari hasil peleburan timah pada kondisi optimum adalah 98,52% uranium, 83,16% thorium, 97,22% fosfat, dan 69,62% LTJ. Uranium, thorium, LTJ, dan fosfat yang telah terlarut diendapkan agar masing-masing unsur terpisah. Faktor yang mempengaruhi kesempurnaan reaksi pada pengendapan antara lain reagen yang digunakan, pH reaksi, suhu, dan waktu. NH4OH digunakan sebagai reagen pengendapan dengan kondisi optimum proses pada pH 4. Suhu dan waktu reaksi tidak mempengaruhi proses. Recovery pengendapan yang dihasilkan adalah 93,84% uranium dan 84,33% thorium. Tin smelting process produces waste in the form of large amount of slag II. Slag II still consist of major elements such as 0.0619% uranium, 0.530% thorium, 0.179% P2O5 and 6.194% RE total oxide. Based on that fact, the processing of slag II is interesting to be researched, particularly in separating uranium and thorium which contained in slag II. Uranium and thorium dissolved using acid reagent (H2SO4). Percentage recovery of uranium, thorium, phosphate and RE oxides by dissolution method are 98.52%, 83.16%, 97.22%, and 69.62% respectively. Dissolved uranium, thorium, phosphat, and RE were each precipitated. The factors which considerable affect the precipitation process are reagent, pH, temperature, and time. NH4OH is used as precipitation reagent, optimum condition are pH 4. Temperature and time reaction did not influence this reaction. Percentage recovery of this precipitation process at optimum condition are 93.84% uranium and 84.33% thorium.

A Correlation between Si Surface Micro-Roughness and Atomic Concentration on Surface: Application to Micro-Roughness Measurement of Si

ABSTRACTWe have developed a new method of evaluating Si surface micro-roughness, by forming thin oxide in HCI/H2O2 solution and then measuring the concentration of chlorine atoms or the total charge in this oxide. It is shown that this oxide does not affect the surface micro-roughness, and the surface concentration of chlorine atoms incorporated in this oxide and the total oxide charge are proportional to the surface micro-roughness, as obtained by AFM. From these correlations, it is possible to evaluate the surface microroughness for large areas compared with the areas of AFM measurement.