The Synthesis of Alginate-Capped Silver Nanoparticles under Microwave Irradiation

Synthesis of silver nanoparticles (Ag-NP) was successfully performed within a few minutes by microwave irradiation of the precursor salt (AgNO3) and alginate mixed solution in one pot. Herein, alginate molecules acted as both a reducing and stabilizing agent for the preparation of the silver nanoparticles. The obtained nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy, particle size analysis (PSA), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). The pH and concentration ratio of the alginate/metal precursor salt greatly influenced the particle size and its distribution of Ag-NP. The higher the pH the higher the nucleation rate and the larger the electrostatic stabilization, while both of them were responsible for producing a smaller particle size and a narrower size distribution. A higher concentration ratio also yielded a smaller particle size and a narrower size distribution, but above the optimum ratio, the trend was conversely changed due to the reducing capability of the alginate, which was dominant above the optimum ratio, thus creating a high density of nuclei, allowing aggregation to occur. A lower ratio not only led to a higher tendency to produce larger particles, but also a higher probability of anisotropic particle shape formation due to the lack of reducing capability of the alginates

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 ?m. 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-1 to 24 kA.m-1 and 15 kA.m-1. A further reduction in the coercivity was observed in Mn-Ti substituted strontium hexaferrite

Magnetic and Microwave Absorption Characteristics of Ti2+-Mn4+ Substituted Barium Hexaferrite

Series of Ti2+-Mn4+ ions substituted BaFe12-2xTixMnxO19 samples with x = 0.0–0.8 have been studied to find out the effect of ion substitution on their microstructure, magnetic, and microwave absorption characteristics. The materials were synthesized through the mechanical alloying process. X-ray diffraction pattern for all sintered samples confirmed that the materials are single phase materials with BaFe12O19 structure. Referring to the results, it is shown that all samples that are subject to ultrasonic irradiation treatment characterized by a crystallite size distribution with the width get slimmer and mean crystallite size get smaller as the substitution level increased from x = 0 to x = 0.8. A sample of latter composition has fine crystals between 10–200 nm with the mean size of 42 nm. The effect of ionic substitution also affected the magnetic properties in which coercivity decreased proportionally with an increase of x value. The saturation magnetization increased to 0.41 T at x = 0.4, and then decreased for higher x values. Hence, the increase occurred only in samples with low-level substitutions of Ti2+-Mn4+ ions. Microwave absorption characterization clearly shows that the reflection loss (RL) value of Ti2+-Mn4+ substituted BaFe12-2xTixMnxO19 samples was enhanced from 2.5 dB in a doped free sample (x = 0) to 22 dB (~92% absorption) in a sample with x = 0.6 in the frequency range 8–12 GHz

Microwave-Assisted Synthesis of Alginate-Stabilized Gold Nanoparticles

An efficient and rapid method for preparation of Au nanoparticles (Au-NP) has been developed by direct microwave irradiation of metal precursor and alginate mixed solution in a single step. Here, alginate molecules act as both the reducing and stabilizing agents of Au-NP. The obtained nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy, particle size analyzer, fourier transform infrared spectroscopy, and transmission electron microscopy. The nanoparticles have a spherical form and perfectly capped with alginate when using alginate and chloro auric acid (HAuCl4) precursor in the concentration range of 0.50 to 0.75% (w/v) and 0.40 mM, respectively. The use of a lower concentration of alginate and/or higher concentration of HAuCl4 caused agglomeration to occur, thereby resulting in a bigger size of Au-NP and red shifting of surface plasmon resonance (SPR) peak to a higher wavelength

Microwave-Assisted Synthesis of Alginate-Stabilized Gold Nanoparticles

An efficient and rapid method for preparation of Au nanoparticles (Au-NP) has been developed by direct microwave irradiation of metal precursor and alginate mixed solution in a single step. Here, alginate molecules act as both the reducing and stabilizing agents of Au-NP. The obtained nanoparticles were characterized by ultraviolet-visible (UV-Vis) spectroscopy, particle size analyzer, fourier transform infrared spectroscopy, and transmission electron microscopy. The nanoparticles have a spherical form and perfectly capped with alginate when using alginate and chloro auric acid (HAuCl4) precursor in the concentration range of 0.50 to 0.75% (w/v) and 0.40 mM, respectively. The use of a lower concentration of alginate and/or higher concentration of HAuCl4 caused agglomeration to occur, thereby resulting in a bigger size of Au-NP and red shifting of surface plasmon resonance (SPR) peak to a higher wavelength

Theoretical Analysis of Interaction Energy in Alginate-Capped Gold Nanoparticles Colloidal System

Stability of Au/alginate nanocomposite was theoretically evaluated by computing various interactions energy which contributes in the system, including attraction and repulsion interaction. The results revealed that both polymer and electrostatic charges played a significant role in the stabilization, but the steric repulsion comes from polymer chain is a more effective stabilization mechanism than the electrostatic repulsion. Higher pH yielded in stronger electrostatic repulsion but when the alginate thickness is low the resulting nanocomposite was less stable in a long time period. Interaction energies for Au/alginate nanocomposite colloidal system was up to ~60 kT for alginate thickness of 1 nm, at very short particle-particle separation distance (< 1 nm). As the alginate thickness can be controlled by adjusting the alginate concentration, it can be concluded that the high stability of Au/alginate nanocomposite can be achieved by employing an appropriate amount of alginate concentration

THE MEASUREMENT OF POTENTIAL RISK OF FIRE AND EXPLOSION AT GAS STASION IN TO ANTICIPATE NON-MILITARY THREATS

Introduction: Gas stations (SPBU in Indonesia) have the potency for fire and explosion hazards due to the storage and distribution of flammable liquids, one of which is Pertamax. This can be a non-military threat in the dimension of public safety because if it occurs, the resulting loss could be very large in terms of material or life. This study aims to determine the risk of fire and explosion at Indonesian gas station. Methods: The risk assessment method used is the Dow's Fire and Explosion Index in a simulated case. Results: The potential for fire and explosion or the value of the Fire Explosion Index (F&EI) in the simulated case is 110,828. The exposure radius is 28,39 m and the damage factor to the Pertamax storage tank is 63%. The large area of the Exposure is 24 m2 with an area of 96 m3 of the bunker building volume. The value of the loss suffered by the company in the event of a fire and explosion in the Pertamax tank is Rp. 403.908.076,97. Conclusion: The results of the study have a risk level that is classified as Intermediate, so it is necessary to control risks such as increasing active protection and is expected to be an input in efforts to safeguard against non-military threats so as to reduce the impact of risks and losses that occur in the Pertamax storage tank