Mas Ayu Elita Hafizah

Synthesis of strontium substituted barium titanate nanoparticles by mechanical alloying and high power ultrasonication destruction

This paper reports the particle and crystallite size characterizations of mechanically alloyed Ba(1-x)SrxTiO3 (BST) with x = 0.3 and 0.7 prepared with the assistance of a high-power sonicator. Analytical grade BaCO3, TiO2 and SrCO3 precursors with a purity of greater than 99 wt.% were mixed and milled using a planetary ball mill to a powder weight ratio of 10:1. Powders obtained after 20 hours of milling time were then sintered at 1200°C for 4 hours to form crystalline powders.These powders were further treated ultrasonically under a fixed 6.7 gr/l particle concentration in demineralized water for 1, 3, 5, 7 hours and a fixed ultrasonic irradiation time of 1 hour to the dispersion of 6.7; 20; 33.3 gr/l concentrations. As to the results of crystallite size characterization, it is demonstrated that the mean crystallite size of BST with x = 0.3 and 0.7 undergo a slight change after the first 1 hour irradiation time and then remain almost unchanged. This was in contrary to the particle size in which the mean ...

Study of aniline polymerization reactions through the particle size formation in acidic and neutral medium

In the present paper, we reported particle size kinetic studies on the conducting polyaniline (PANI) which synthesized through a chemical oxidative polymerization technique from aniline monomer. PANI was prepared using ammonium persulfate (APS) as oxidizing agent which carried out in acidic and neutral medium at various batch temperatures of respectively 20, 30 and 50 °C. From the studies, it was noticed that the complete polymerization reaction progressed within 480 minutes duration time. The pH of the solution during reaction kinetic reached values 0.8 – to 1.2 in acidic media, while in the neutral media the pH value reached values 3.8 – 4.9. The batch temperature controlled the polymerization reaction in which the reaction progressing, which followed by the temperature rise of solution above the batch temperature before settled down to the initial temperature. An increment in the batch temperature gave highest rise in the solution temperature for the two media which cannot be more than 50 °C. The final product of polymerization reaction was PANI confirmed by Fourier Transform Infra-Red (FTIR) spectrophotometer for molecule structure identification. The averages particle size of PANI which carried out in the two different media is evidently similar in the range 30 – 40 μm and insensitive to the batch temperature. However, the particle size of PANI which obtained from the polymerization reaction at a batch temperature of 50 °C under acidic condition reached ∼53.1 μm at the tip of the propagation stage which started in the first 5 minutes. The size is obviously being the largest among the batch temperatures. Whereas, under neutral condition the particle size is much larger which reached the size 135 μm at the batch temperature of 20 °C. It is concluded that the particle size formation during the polymerization reaction being one of the important parameter to determine particle growing of polymer which indicated the reaction kinetics mechanism of synthesize polyaniline.In the present paper, we reported particle size kinetic studies on the conducting polyaniline (PANI) which synthesized through a chemical oxidative polymerization technique from aniline monomer. PANI was prepared using ammonium persulfate (APS) as oxidizing agent which carried out in acidic and neutral medium at various batch temperatures of respectively 20, 30 and 50 °C. From the studies, it was noticed that the complete polymerization reaction progressed within 480 minutes duration time. The pH of the solution during reaction kinetic reached values 0.8 – to 1.2 in acidic media, while in the neutral media the pH value reached values 3.8 – 4.9. The batch temperature controlled the polymerization reaction in which the reaction progressing, which followed by the temperature rise of solution above the batch temperature before settled down to the initial temperature. An increment in the batch temperature gave highest rise in the solution temperature for the two media which cannot be more than 50 °C. The final...

Enhanced dielectric properties of Nanocrystalline Ba(1-x)SrxTiO3 (x=0 and 0.3) ceramics

In this paper, we report the enhancement of the dielectric constant of barium titanate (BTO) through partial substitution of strontium to barium and crystallite size reduction through a high power ultrasonic treatment. The sample under investigation is Ba1-xSrxTiO3 or BST with x = 0 and 0.3 compositions prepared through mechanical alloying of SrCO3, BaCO3 and TiO2 precursors as the feedstock. All mechanically alloyed samples were crystalline powders with a single phase as confirmed by an x-ray diffractometer (XRD). The mechanically alloyed materials were consisted of multi-crystallite particles as confirmed both by XRD data analysis and particle size evaluation. Subject to an additional ultrasonic treatment, the multi-crystallite particles were fragmented toward mono-crystallite particles with the mean crystallite size about 52 nm after 12 hours irradiation. Even a smaller mean crystallite size (18 nm) with a narrower crystallites distribution then that of BTO was obtained in Ba1-xSrxTiO3 with x = 0.3. Such a narrow crystallite size distribution with a small mean crystallite size has superior dielectric constant over those of BTO and doped BTO with a large mean crystallite size. The highest dielectric constant of 3000 was obtained at a frequency of 273 Hz in doped BTO after 12 hours ultrasonic irradiation. The value is 12 times higher than those of BTO and doped BTO with a large crystallite size.

Synthesis and Magnetic Characterization of Mn‐Ti Substituted SrO.6Fe2‐xMnx/2Tix/2O3 (x = 0.0–1.0) Nanoparticles by Combined Destruction Process

Single phased SrO.6Fe2-xMnx/2Tix/2O3 (x = 0.0; 0.5; and 1.0) nanoparticles, whose mean size was comparable with the crystallite size, were successfully fabricated through mechanical alloying and a subsequent ultrasonic destruction processes. The ultrasonic destruction process employed a transducer operated under amplitudes of 35, 45, and 55 μm. Results indicated that the mean particle size was not determined by the transducer amplitude, but the mechanical properties of the materials, as well as the initial size of the particles. After ultrasonic destruction, the mean sizes of the particles decreased to the range of 87–194 nm with a narrow distribution width. The mean particle sizes were about 1 to 3 times larger than the respective crystallite sizes. Such fine particles were aimed to decrease the coercivity, as was seen in the sample with x = 0, which showed a decrease in coercivity from 474 kA.m to 24 kA.m and 15 kA.m. A further reduction in the coercivity was observed in Mn-Ti substituted strontium hexaferrite.

The effect of milling time and sintering temperature on formation of nanoparticles barium strontium titanate

Nanoparticles of barium strontium titanate (BST) or Ba0.3Sr0.7TiO3 were synthesized by mechanical alloying and successive ultrasonic irradiation treatment. This research attempted to reduce the particles obtained through mechanical milling of mechanically alloyed powders to the particles with sizes in nanometer scale. The effectiveness of milling time on the synthesis of BST nanoparticles was confirmed by mean particle size evaluation which showed that a milling duration up to 60 h was required to bring down gradually the mean particle from 5.7 into 2.4 µm. The broadening lines of XRD pattern of the ultrasonically treated samples were analyzed using a high score plus (HSP) and a whole powder pattern modeling (WPPM) software to obtain the crystallite size distribution. The mean crystallite size of the treated particles was found 49 nm which is about 60 times lower than its mean particle size. It is shown that mechanical alloying through the sintering process followed by ultrasonic destruction will promote ...

Surfactant-assisted synthesis of Ba0.7Sr0.3TiO3 nanoparticles by mechanical alloying and ultrasonic irradiation

Ba0.7Sr0.3TiO3 nanoparticles were successfully synthesized by mechanical alloying and successive ultrasonic irradiation method with an addition of surfactant. Fine crystalline particles were first obtained after re-milled the sintered mechanically alloyed powders of BaCO3, TiO2 and SrCO3 precursors for 20 hours in which the size of particles was found below 300 nm. These fine particles were further refined their size under a high power ultrasonic treatment for 6 hours. Various types of surfactant namely amphoteric, cationic, anionic and non-ionic were brought into studies to find out their effectiveness in preventing the agglomeration due to strong attractive forces between fine particles. It was found that all surfactant prove effective to prevent the agglomeration. This was indicated in the distribution of particle size measurement in which mean size of particles added surfactants (139 nm–158 nm) was less than that of surfactant free (173 nm). However, among all surfactant which added in the media conta...

Structural modification of strontium hexaferrite through destruction process and ionic substitution

Synthesis of single phased SrO.6Fe2-xMnx/2Tix/2O3 (x = 0.0; 0.5; and 1.0) nanoparticles has been prepared through mechanical alloying, assisted with the ultrasonic destruction process. Monocrystalline particles were obtained when x = 0 treated with ultrasonic destruction at 55 μm of transducer amplitude. Average particle size and crystallite size were reduced significantly from 723 nm to ∼87 nm for x = 0. The particle size was not significantly reduced when x = 0.5 and x = 1 was changed. On the other hand, substitution of Ti elements on some of Fe elements expectedly had a major effect on reducing particle size. This was proven by larger size on both particle and crystallite size at x = 1 rather than x = 0.5, with comparison respectively 2:1 (in nm). In addition, a higher transducer power was required for modifying Strontium Hexaferrite (SHF) with more Ti elements and a bigger size of pre-ultrasonic destructed sample. It is concluded that the amplitude of the transducer in ultrasonic destruction process a...

Influence of Ionic Surfactants under Ultrasonic Irradiation to Reduce the Particle Size of Mechanically Alloyed La1-XSrX Fe0.5Mn0.25Ti0.25O3 Powders

In this study, nanoparticles La1-xSrxFe0.5Mn0.25Ti0.25O3 particles were prepared by two successive methods: the mechanical alloying (MA) with the successive sintering and the deagglomeration of MA powders in the demineralized water containing surfactant under ultrasonic irradiation. It is shown that MA powders have coarser particle size of a slightly less than 6 micron in average. Additionally, the particle size distribution was relatively broadening which indicates a large size variation in particle sizes. As MA powders were dispersed in the demineralized water and irradiated by a 40 KHz ultrasonic wave for 5 hours the particle size distribution was improve significantly, it has a narrow particle size distribution with a mean particle size almost 180 nm. The particle has crystallite with mean size 20-26 nm subject to XRD line broadening analysis. Thus, the particles can be called nanoparticles clusters. The study also indicated the breakup of nanoparticle cluster was no longer effective in a prolonged ultra sonication time and yet reagglomeration was obvious. However, the latter was not occurred in a disperse media containing surfactants. In this study, four types of surfactant were used and their influences to the particle sizes were evaluated. According to this study, the four types of surfactants could reduce further the particle size but in different pathways. Sodium Dodecyl Sulphate (SDS) as anionic surfactant reduced the sizes of nanoparticle clusters to almost 180 nm by one step ultra sonication. While cationic, non-ionic and amphoteric surfactants promoted the gel formation in the first place, the nanoparticle clusters were then obtained after an additional heating to breaking the gel form to dry powders. The present of gel was due to stabilization process of the particle to avoid any re-agglomeration between each fine particle. In this paper, we discussed a systematic material preparation towards nanoparticles clusters and the mechanism as well as influence of surfactants in particle size reduction for LSMFTO powders.