Papers by Author: Bambang Sunendar Purwasasmita

Abstract: Hydrophobic textile is a type of smart fabrics. Some of it are commonly coated with small particles and finally treated by water repellent agent in terms of acquiring its hydrophobic property. This research describes how hydrophobic textile are formed from its initial form of fabrics and even yarn, which are fibers. Synthesis process was commenced through wet spinning of viscose rayon mixed with nanorod silica which has been formerly produced with sol gel method. These fibers were then coated with chitosan and dried out by vacuum instrument. Scanning Electron Microscopy (SEM) results showed that nanorod silica were well attached on the fibers. Followed by Energy Dispersive Spectroscopy (EDS) mapping characterization, silica particles were moderately dispersed on its surface, performing roughness and creating hydrophobic effect. In addition, several characterization methods correlated to water absorption of the fibers were conducted. Fibers swelling percentage decreased from 50.2% to 17.13%, while moisture regain (MR) number also decreased from 14.28 to 10.72.

Abstract: A series of experiments is made to produce silica, mixing with tin dioxide (SnO₂), and characterizing for application of waveguide device. Silica xerogels (SX) are prepared from raw materials derived from rice husks ash (RHA), which abundant in South East Sulawesi. The synthesis conditions have been optimized to obtain the ash of rice husks with the maximum silica content. SnO₂ are prepared from a commercial powder. The ceramic waveguide materials are produced by mixing SX and SnO₂ with various composition. The mixtures are molded to form the rectangular shape of 20 mm, 40 mm, and 5 mm in size. The samples will be sintered at different level of temperatures (from 300°C to 1200°C) by using microwave heating system as well as electric furnace. The microstructural of sintered samples were characterized on the basis of the experimental data obtained using densification measurement method (Archimedes method), crystallization (X-ray diffraction, XRD), microstructure (Scanning electron microscope, SEM). Optical and related properties such as the functional groups, structure, and absoption were characterized by using FTIR, Infrared and Raman Spectroscopy and absorption (UVVis). The permittivity and permeability will be calculated from S-parameters determined by using Vector Network Analyzer (VNA). Characterization results are presented in this paper and the others are will be published in another separated papers. Furthermore, the relationship between properties with SnO₂ content and sintering temperature is also studied.

Abstract: This study prepared Magnesium-Partially Stabilized Zirconia (Mg-PSZ) filler synthesis and direct foaming technique using egg whites, and impregnated by PMMA. The results were evaluated systematically by X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). XRD results denote that the powder sample of MgPSZ was successfully formed with various crystal size of tetragonal and monoclinic phase. SEM and TEM observations revealed that nanoparticles MgPSZ were in spherical and long rounded shapes. Furthermore, SEM observation revealed that the direct foaming method were also successful in the formation of porous structures which favourable for impregnation process by PMMA. The use of egg whites as a polymer precursor in both methods demonstrates that porous specimens contained nanosized, predominantly tetragonal, Mg-PSZ powders were successfully synthesized. This shall yield an interesting prospect towards cheap, reliable, and biocompatible product to resemble the modulus elasticity of dentin.

Abstract: In this study, novel composites materials composed of polymethyl methacrylate (PMMA) reinforced ZrO₂-Al₂O₃-SiO₂ filler system were developed. Zirconia-alumina-silica filler system were synthesized through sol-gel technique. Chitosan and trimethoxypropilsilane (TMPS) were used to modify the composites system. The resulting composites material were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and hardness test. SEM images displayed the composites particles in nanometer size with minor agglomeration. The XRD results revealed the presence of cubic and tetragonal phase of zirconia and also monoclinic silica phases in the composites system. These crystallographic characteristic could affect the mechanical properties of the composites. The hardness value for un-modified composites was 15.27 ± 0.25 VHN and for TMPS 19.43 ± 1.89 VHN and chitosan modification 18.75 ± 2.05 VHN, respectively. Therefore, these novel composites materials composed of PMMA reinforced filler system of zirconia-alumina-silica would provide the potential to apply in dental technology.

Abstract: Zr-Al-Si posts were successfully synthesized using biotemplate of eggshell membrane by sol-gel method and strengthening with matrix of polymethyl methacrylate (PMMA). The dental posts made were analyzed with the scanning electron microscope (SEM), three point bending and microvickers hardness tester. There are two methods used to synthesized Zr-Al-Si posts, with calcination and without calcination. The synthesized mechanism is discussed here.

Abstract: Treatment for bone cancer has begun to be experimented with ferrimagnetic for magnetic induction hyperthermia. On the other hand, composites of bioceramics and biopolymer have been studied for scaffold as these materials resemble the structure of bone. The current study investigated the magnetization of calcium aluminum ferrite magnetic (CaAl₄Fe₈O₁₉) incorporated in carbonate apatite, alginate and chitosan, that serves as a scaffold. CaAl₄Fe₈O₁₉ powder were synthesized using calcium nitrate, aluminium nitrate and ferrous chloride using the sol-gel method. Combining the carbonate apatite/chitosan/alginate compoiste and CaAl₄Fe₈O₁₉ using the freeze-dry method has produced carbonate apatite/alginate/chitosan/CaAl₄Fe₈O₁₉ composite scaffolds. The CaAl₄Fe₈O₁₉ powder and the scaffolds were observed using SEM (scanning electrone microscope) and their magnetization were measured using VSM (vibrating sample magnetometer). It was shown that the scaffold is a composite structure of CaAl₄Fe₈O₁₉ particles, having diameter ranging from 0.5 to 2 µm, embedded in the pore walls of the carbonate apatite/alginate/chitosan matrix. The saturation magnetization Ms and remanence magnetization Mr of the CaAl₄Fe₈O₁₉ particles were 20 and 2.0 emu/g, whereas, those of the magnetic scaffold were 4.3 and 2.0 emu/gr. The addition of the carbonate apatite/alginate/chitosan composite into CaAl₄Fe₈O₁₉ decreased the fraction and/or magnetic of the CaAl₄Fe₈O₁₉ particles.

Abstract: The global need of biomaterial products especially in bone clinical application increases every year. The gold methods like autograft and allograft have some limitations in the application such as the availability of donor sites, antigenicity issues, the high cost, etc. To solve the problems, many researches and activities in the field of biomaterial have been conducted continuously in the past decades to develop the proper synthetic materials for bone substitutes which have properties similar to bone tissue. In this research, the synthesis of biocomposite for bone scaffold application prepared by freeze drying method has been done successfully. The materials used are biopolymer (alginate and chitosan) and bioceramics (carbonate apatite) with certain mixing variations. SEM result showed that the pores obtained by freeze drying method can mimic the pores of actual bone thus they will be able to resemble cells microenvironment, enhance interface interaction, and support cell proliferation. The existence of carbonate apatite on the scaffold’s surface can be observed with particle size of 0.05 – 1 μm and has been dispersed evenly. These results are in good agreement with FT-IR analysis that indicates the presence of PO₄^3– functional group on the scaffold at wave numbers 569 and 1041.56 cm^–1 and CO₃^2– functional group at wave number 1411.89 cm^–1. The in vitro biological evaluation of HeLa cells which exposed to extract solution of scaffold (in some variations of concentration) indicated that the scaffold obtained was not cytotoxic to the HeLa cells.

Abstract: Barium hexaferrite is categorized as hexagonal ferrite material with ferrimagnet properties. Barium hexaferrite has high coercivity, curie temperature, anisotropy magnetic field, and chemical stability that is often used as permanent magnet. It can be synthesized by using bottom up or top down method. The bottom up method of sol-gel has potential advantages in industry application compared to the top down method because of low energy requirement, more homogeneous product, and low time consuming to achieve nanometer size. The development of sol-gel method by using tapioca and chitosan as surfactant increases the quality of the product. Tapioca is used to increase anisotropy properties of particles by changing the particles shape into rodlike shape whereas chitosan is used to stabilize them at small size. Molar ratio of Fe³⁺/Ba²⁺ is set on 12 and the ratio of tapioca/chitosan is set on 1/3, 1/2, and 1. Iron (III) nitrate is used as Fe³⁺ source whereas barium nitrate is used as Ba²⁺ source. Condensation is done by heating up the sol system in the oven at 100^OC. The product then is calcined at 1000^OC with holding time of 3 hours. The calcined product is then characterized by X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), and Vibrating Sample Magnetometer (VSM). XRD result shows that the hematite phase has still been formed. The occurrence of the phase indicates that the reaction between iron and barium is uncompleted. SEM images show the existence of needle and rod-shaped particles with diameter of 200nm–550nm. It explains that tapioca can be used as rodlike template. The increase of tapioca tends to enlarge the rod-shaped particle and remove the needle-shaped particle. VSM result shows that the highest value of Br is found in the sample of tapioca/chitosan with the ratio of 1/3 and the value of 24 emu/g. The fact indicates that the optimal ratio of tapioca/chitosan is 1/3.

Abstract: Bacterial cellulose-based carbon nanotube has been synthesized by catalytic graphitization method. Bacterial cellulose (BS) is a source of cellulose produced from fermentation of medium by Acetobacter xylinum. Since it contains unbranch polymer linked by β-1.4 glucopyronose with hydroxil groups, BS is able to use as precursor in synthesis of carbon nanotube. Due to catalytic graphitization, chitosan served as coupling agent and dispersant of catalyst and various concentration of catalyst FeCl3.6H2O also were used. Graphitization was conducted in furnace with inert nitrogen gas atmosphere at 800°C for 2 hours. SEM-EDS were used to evaluate the morphology and semi-quantitative analysis of sample. TEM was used to determine the microstructures and crystallographic. When the chitosan was added 0.5%, its served as coupling agent and dispersant of catalyst with BS. Chitosan improved physical properties, relieved its brittleness, and caused the optical properties of BS. Catalyst of FeCl3.6H2O was used to assist the formation and growth of carbon nanotube. The amount of carbon was not affected by time aging. 0.1 M FeCl3.6H2O was the optimum concentration to produce carbon nanotube with 81, 58% the mass of carbon, plane orientation (002) (100) and the diameter of carbon nanotube is 25 nm.

Abstract: In the present investigation, nanocrystalline silica xerogel (NSX) powders were produced from an amorphous silica xerogel (ASX) extracted from sago waste ash. The NSX powders have been calcined at 1200oC, milled and then annealed at temperatures ranging from a room temperature to 1200oC. Their properties (and most notably the size of the particles) have been characterized on the basis of the experimental data obtained using thermal analysis (DSC/TGA), X-ray diffraction (XRD), Infrared and Raman spectroscopy. For the crystalline silica xerogel powders the results show a narrow distribution of the particle sizes centered around an average value of 636  67 nm. The DSC analysis of NSX indicates that in the temperature range from a room temperature to 300oC five distinct stages of the crystallization process take place, which are delimited by the transition temperature of 38oC, 92oC, 129oC, 168oC, and 246oC, respectively. Above 300oC, the crystalline phase is similar to an amorphous silica xerogel (ASX), i.e. cristoballite-like and tridymite-like crystalline silica phases confirmed by the XRD analysis. It has been observed that the characteristic band of cristoballite is strongly dependent on the thermal history and the NSX transforms into a stable form at a temperature of 1200oC. Both the Raman and the FTIR spectra elucidate the bonding system of the constituent atoms and groups (such as Si, O and OH) and throw light on their underlying structure. The obtained results are important for optimization of the parameters of the technological processes for production of nanocrystalline silica glass ceramics used as a host matrix for luminescence materials, each of which requires a specific porosity and structure.