Hasil Pencarian  ::  Simpan CSV :: Kembali

Abstrak :
ABSTRAK
Karya tulis ini melaporkan hasil proses pembentukan nanopartikel Ba0.7Sr0.3TiO3 dan Ba0.3Sr0.7TiO3 melalui pemaduan mekanik dan destruksi ultrasonik daya tinggi. Proses destruksi ultrasonik dilaksanakan dalam 3 kondisi berbeda yaitu menggunakan variasi rasio diameter transduser dan reaktor 1:1.4, 1:1.6, dan 1:1.8 terhadap media mengandung partikel kosentrasi 3.0 gr/l selama waktu destruksi 3 jam. Secara spesifik, tujuan dari penelitian ini adalah mempelajari efek rasio diameter transduser dan diameter reaktor (dt/Dr) terhadap pembentukan nanopartikel Ba0.7Sr0.3TiO3 dan Ba0.3Sr0.7TiO3. Karakterisasi partikel yang diperoleh menggunakan XRD, PSA, dan SEM. Hasil identifikasi fasa material dari evaluasi difraksi sinar X memastikan bahwa material Ba0.7Sr0.3TiO3 dan Ba0.3Sr0.7TiO3 adalah material berfasa tunggal dan destruksi ultrasonik tidak menyebabkan perubahan fasa material. Kedua material berbeda dalam ukuran rata-rata partikel sebelum destruksi ultrasonik yaitu 538 nm untuk partikel Ba0.7Sr0.3TiO3 dan 480 nm untuk partikel Ba0.3Sr0.7TiO3. Kedua nilai ukuran rata-rata partikel ini mengalami penurunan selama proses destruksi ultrasonik. Namun, ukuran partikel terkecil masing-masing material adalah 38 nm dan 24 nm diperoleh pasca destruksi dengan (dt/Dr) adalah 1.8. Ukuran rata-rata partikel ini hampir sama dengan ukuran rata kristalitnya masing-masing 22 nm dan 14 nm. Dengan demikian hanya terdapat 1 kristalit dalam masing-masing partikel. Dapat disimpulkan bahwa nanopartikel baik material Ba0.7Sr0.3TiO3 maupun Ba0.3Sr0.7TiO3 dapat dihasilkan dari dua tahapan proses yaitu tahapan sintesis dengan pemaduan mekanik dan tahapan destruksi dengan metode destruksi ultrasonik daya tinggi. Partikel monokristalit Ba0.7Sr0.3TiO3 dengan ukuran 38 nm dan Ba0.3Sr0.7TiO3 dengan ukuran 24 nm telah dihasilkan dari destruksi ultrasonik menggunakan parameter proses (dt/Dr) 1.8 dalam durasi destruksi selama 3 jam.

---

ABSTRACT
We report results of research on the formation of Ba0.7Sr0.3TiO3 and Ba0.3Sr0.7TiO3 nanoparticles through the mechanical alloying process and followed by high power ultrasonic destruction. Ultrasonic destruction process carried out in three different modes of the transducer and reactor diameter ratios respectively 1:1.4, 1:1.6, and 1:1.8 against the media containing particles of 3.0 g/l concentration during 3 hours destruction time. The specific goal of this work was to study the effect of transducer and reactor diameter ratio (dt/Dr) on the formation of Ba0.7Sr0.3TiO3 and Ba0.3Sr0.7TiO3 nanoparticles. Particle characterizations were carried out under the employment of XRD, PSA, and SEM. Results of material phase identification by XRD ensure that the synthesized Ba0.7Sr0.3TiO3 and Ba0.3Sr0.7TiO3 material are both single phase. In addition, the ultrasonic destruction to the particle materials did not cause the phase change. Prior to ultrasonic destruction, the two materials are different in their average particle size in which Ba0.7Sr0.3TiO3 and Ba0.3Sr0.7TiO3 respectively has particles with mean sizes 538 nm and 480 nm. The average value for both particles was decreased during ultrasonic destruction. However, the smallest mean particle size of each material was 38 nm and 24 nm which were obtained after the ultrasonic destruction by (dt/Dr) of 1.8. These average sizes are almost equal to the average size of their crystallites which are respectively 22 nm and 14 nm. Thus there is only one crystallite within each particle. It can be concluded that both Ba0.7Sr0.3TiO3 and Ba0.3Sr0.7TiO3 nanoparticles can be produced by a two-stage process. The first stage is a phase formation by mechanical alloying and the formation of Ba0.7Sr0.3TiO3 and Ba0.3Sr0.7TiO3 nanoparticle obtained in the second stage in which the particle sizes were further reduced by the high power ultrasonic destruction. Single crystallite particles with a mean size of 38 nm for Ba0.7Sr0.3TiO3 and that of 24 nm for Ba0.3Sr0.7TiO3 have been successively obtained by ultrasonic destruction process with a parameter (dt/Dr) of 1.8 within 3 hours destruction time.

Abstrak :
Quenching process is performed as part of heat-treatment for steels in order to enhance mechanical properties, by rapid cooling to room temperature. Quenching is done to obtain certain properties or microstructure by inequilibrium cooling to prevent any phase transformation to occur, thus giving the desired phase at room temperature. In recent developments, the addition of microparticles to the quench media, referred to as microfluid, is done to improve its thermal conductivity which in turn, accommodate heat dissipation. Lab-grade carbon powders were added as the nanoparticle to a water-based quench media. Microparticles were synthesized using the top-down method, where size reduction of the particles was done by grounding using a planetary ball mill for 15 hours at 500 rpm. Particle size, composition, and morphology of the particles were measured by Field-Emission Scanning Electron Microscope (FE-SEM), and Energy Dispersive X-Ray Spectroscopy (EDX). Water-based microfluids with volumes of 100ml were produced using the two-step method, by mixing carbon nanoparticles at 0.1%, 0.3%, and 0.5% in various concentration of anionic surfactant Sodium Dodecylbenzene Sulfonate of 1%, 3% and 5% respectively. Austenization of AISI 1045 or JIS S45C steels at 1000ºC were done prior to quenching. Results of the hardness value corresponds to the severity of the quenching mediums, with peak hardness of 845 HV for 0.1% carbon with 1% SDBS, 848 HV for 0.3% carbon with 3% SDBS and 878 HV for 0.5% carbon with 3% SDBS. The hardness value shows a significant improvement over hardness results without SDBS addition. Excess surfactant addition, however, yields a lower hardness due to the re-agglomeration of particles