Hasil Pencarian  ::  Simpan CSV :: Kembali

"ABSTRACTThe purpose of this study is to explore the implementation of Government's Internal Control System in Islamic perspective. This research used descriptive method with Al-Qur'an, Hadith, regulations, books and articles as the sources of this research. Although Internal Control's Comprehensive Framework and Guidance developed by COSO in 1992, but it had implemented by muslim leader since Nabi Muhammad's era until Turki Utsmani Dynasty's era. Five components of Internal Control that formed by COSO and adopted by government in PP No.60 2008 are control environment, risk assessment, control activities, information and communication, and monitoring, each components have subcomponents; and for control environment we suggest to add with the spiritual, nature and style of leadership. The basic component of internal control is control environment, because it has a role as a protector for other components. If control environment has worked properly, then it will minimize a risk, control activities would be implemented simply, information and communication will run smoothly and internal control could be monitored periodically."

"Teknologi Solid Oxide Fuel Cell (SOFC) saat ini beroperasi pada temperatur tinggi. Pada kondisi lingkungan SOFC 800°C, fenomena oksidasi yang terjadi menyebabkan menurunnya performa interkoneksi SOFC. SanergyHT adalah ferritic steels yang dikembangkan oleh Sandvik dengan komposisi khusus untuk menghindari evaporasi kromium membentuk kerak Cr2O3. Untuk mengurangi pertumbuhan kerak oksida diperlukan pelapisan pada permukaan. Material pelapis yang dapat digunakan adalah fasa spinel. Dalam penelitian ini disintesis fasa spinel dengan komposisi (MnCo)3O4 sebagai material pelapis untuk SanergyHT. Untuk membentuk fasa spinel, mechanical alloying Mn-Co dilakukan selama 24 jam. Serbuk titanium (Ti) ditambahkan selama proses milling untuk menstabilkan fasa spinel. Serbuk SanergyHT dan serbuk bahan pelapis dipadatkan dengan SPS pada tekanan 30 MPa dan temperatur 1000°C. Selanjutnya dilakukan proses perlakukan panas pada temperatur 115°0C selama 5 jam. Uji oksidasi dilakukan selama 100 jam pada temperatur 800°C. Analisis fasa sebelum dan setelah oksidasi dilakukan dengan XRD, detail morfologi mikrostruktur dianalisis dengan SEM/EDX. Fasa spinel MnCo2O4 berhasil terbentuk setelah pengujian oksidasi. Terbentuk fasa spinel lainnya, yaitu Co3O4 dan Ti0.5MnCo1.5O4 akibat dari bahan paduan lapisan yang memiliki fasa metastabil. Perlakuan panas sebelum uji oksidasi mengizinkan atom-atom untuk saling berdifusi ke kondisi setimbangnya. Zona interdifusi yang terbentuk pada sampel dengan pemanasan lebih rendah (kurang lebih 14,32 dan 7,92 mikrometer) dibandingkan tanpa pemanasan (kurang lebih 19,89 dan 12,35 mikrometer). Penambahan Ti pada paduan MnCo dapat menggantikan fasa Mn3O4 menjadi TiMn2O4 dan memberikan orientasi kristal yang baik. Secara mikrostruktur, kehadiran Ti dapat menghalangi difusi yang terjadi antara lapisan dan substrat sehingga laju pertumbuhan fasa intermetalik metastabil menurun. Setelah uji oksidasi, perlakuan panas dapat secara efektif menghambat proses difusi oksigen sehingga memberikan ketahanan oksidasi yang baik. Sedangkan penambahan Ti setelah uji oksidasi membantu meningkatkan daya rekat kerak oksida, meminimalisir rongga yang terbentuk, dan menstabilkan proses difusi oksigen ke dalam lapisan.

---

Solid Oxide Fuel Cell (SOFC) technology currently operates at high temperatures. At 800°C SOFC environmental conditions, oxidation phenomenon may occur which cause the SOFC interconnect performance to deteriorate. SanergyHT are ferritic steels developed by Sandvik with a special composition to prevent chromium evaporation to form Cr2O3 scale. To reduce the growth of oxide scale required coating on the surface. Coating material that can be used is spinel phase. In this study, a spinel phase was synthesized with the composition (MnCo)3O4 as a coating material for SanergyHT. To form the spinel phase, mechanical alloying of MnCo was carried out for 24 hours. Titanium (Ti) powder is added during the milling process to stabilize the spinel phase. SanergyHT powder and coating material powder were compacted with SPS at 30 MPa and 1000°C. Heat treatment was carried out at 1150°C for 5 hours. The oxidation test was carried out for 100 hours at 800°C. Phase analysis before and after oxidation was carried out by XRD, microstructural morphological details were analyzed by SEM/EDX. The MnCo2O4 spinel phase was successfully formed after oxidation testing. Other spinel phases (Co3O4 and Ti0.5MnCo1.5O4) were formed due to the alloy materials has a metastable phase. The heat treatment before oxidation test allows the atoms to diffuse to an equilibrium state. The interdiffusion zone in sample with heat treatment is lower (around 14,32 dan 7,92 micrometer) than without heat treatment (around 19,89 dan 12,35 micrometer). The addition of Ti can replace Mn3O4 phase to TiMn2O4 and provide a good crystal orientation. From microstructural viewpoint, the presence of Ti can reduce the diffusion that occurs between the coating and the substrate, so the growth rate of the metastable intermetallic phase decreases. After the oxidation test, heat treatment can effectively inhibit the oxygen diffusion process thus providing good oxidation resistance. The addition of Ti helps increase the adhesion of the oxide scale, minimizes the voids formed, and stabilizes the process of oxygen diffusion into the coating"

"Bahan interkoneksi solid oxide fuel cell (SOFC) yang paling unggul adalah baja tahan karat feritik (ferritic stainless steel). Namun, terdapat masalah dalam penggunaan baja tahan karat feritik sebagai bahan interkoneksi, yaitu terbentuknya lapisan Cr2O3 yang akan menghasilkan spesies gas Cr(VI), di mana ini akan menurunkan kinerja SOFC. Untuk mengatasi masalah tersebut, dibutuhkan lapisan pelindung spinel berbahan NiFe untuk menekan pertumbuhan Cr2O3. Penelitian ini membahas pembentukan fasa spinel dan oksida dari lapisan NiFe dan NiFeCu yang dibentuk dengan proses mechanical alloying paduan lapisan, spark plasma sintering (SPS), perlakuan panas, dan oksidasi. Pembentukan fasa dan struktur kristal diamati dengan x-ray diffraction (XRD). Struktur mikro diamati menggunakan scanning electron microscope dan electron dispersive x-ray (SEM-EDX). Setelah proses SPS, dihasilkan beberapa fasa dari XRD diantaranya Fe-Cr, Fe-Ni pada lapisan NiFe, Fe-Ni-Cu pada lapisan NiFeCu serta beberapa fasa oksida (FeO dan Fe3O4). Fasa oksida terbentuk akibat proses mechanical alloying dilakukan dalam keadaan tidak vakum dan penggunaan temperatur tinggi pada SPS mendorong terjadinya oksidasi. Perlakuan panas atau heat treatment meningkatkan tingkat kompaksi antara substrat dan pelapis pada sampel sebelum dioksidasi. Doping Cu mampu meningkatkan kerapatan fasa Fe-Ni(-Cu) atau area terang pada paduan di lapisan. Fasa spinel Fe2NiO4 terbentuk setelah uji oksidasi pada temperatur 800C selama 100 jam, diikuti dengan fasa Fe2O3. Perlakuan panas dan doping Cu menghasilkan lapisan oksida Fe2O3/Fe3O4 pada lebih merata dan seragam. Perlakuan panas dapat meningkatkan resistansi oksidasi lapisan NiFeCu setelah oksidasi, ditandai dengan adanya pori pada lapisan oksida yang dihasilkan.

---

The most superior solid oxide fuel cell (SOFC) interconnect material is ferritic stainless steel. However, there is a problem in using ferritic stainless steel as an interconnection material, namely the formation of a layer of Cr2O3 which will produce Cr(VI) gas species, which will reduce SOFC performance. To overcome this problem, a protective layer of spinel made from NiFe is needed to suppress the growth of Cr2O3. This research discusses the formation of spinel and oxide phases from NiFe and NiFeCu layers formed by mechanical alloying of coating alloys, spark plasma sintering (SPS), heat treatment, and oxidation. Phase formation and crystal structure were observed by x-ray diffraction (XRD). The microstructure was observed using a scanning electron microscope and electron dispersive x-ray (SEM-EDX). After the SPS process, several phases were produced from XRD including Fe-Cr, Fe-Ni in the NiFe layer, Fe-Ni-Cu in the NiFeCu layer and several oxide phases (FeO and Fe3O4). The oxide phase is formed as a result of the mechanical alloying process carried out in a non-vacuum state and the use of high temperatures in SPS encourages oxidation. Heat treatment increases the degree of compaction between the substrate and the coating on the sample prior to oxidation. Cu doping can increase the density of the Fe-Ni(-Cu) phase or the bright area of ​​the alloy in the coating. The Fe2NiO4 spinel phase was formed after an oxidation test at 800°C for 100 hours, followed by the Fe2O3 phase. Heat treatment and Cu doping resulted in a more even and uniform layer of Fe2O3/Fe3O4 oxide on it. Heat treatment can increase the oxidation resistance of the NiFeCu layer after oxidation, indicated by the presence of pores in the resulting oxide layer."