Advanced Materials Research Vol. 506

Abstract: The atomic force microscope (AFM) was employed to study the significant effects of silver (Ag) nanoparticles-treated on the elastic cell wall of bacteria. In this study, the exposed Staphylococcus aureus was grown at 37 °C for 14 h. The cultures were centrifuged and cell pellets were resuspended in Milli-Q water to prepare final bacterial suspensions. A drop of bacterial suspension was deposited on polydimethylsiloxane (PDMS) sheet and allowed to air dry at room temperature before imaging. The cell suspension was collected at certain time intervals from the beginning of the test. The morphology of the cell surface compares between without treatment and Ag-treated cell suspension was investigated. The force mappings were obtained for the PDMS substrate and for the bacteria while scanning obliquely. The contribution of the internal osmotic pressure, to obtain a quantitative measure for the elasticity of the cell wall, had to be estimated. The pyramid-shaped AFM tip indented into a soft cell and the resulting bacterial surface was flat, and irreversible changed of bacterial cell structure. The investigation is attempted to understand pronounced effect of Ag nanoparticles on the individual gram-positive bacterial cell after treated with Ag nanoparticles.

Abstract: The objective of the present study was the qualitative comparison of hydroxyapatite (HAP) extracted from bio waste by different methods. Fish bones obtained from mango fish (Oreochromis niloticus) were used as natural source for HAP synthesis. Three different processes were applied to extract the natural HAP: annealing at 400-1000 °C (F400-F1000), H₂O₂ cleaning and NaOH cleaning. A combination of TGA/DSC analyses, XRD spectrometry, FTIR spectroscopy and scanning electron microscopy were utilized for characterization. They indicated that all methods have the ability to eliminate the organic compounds present in the fish bones. However, annealing of the bone sample was found to be more efficient approach in reducing the amount of organic phase; only inorganic phase was remained in F600, F800 and F1000. For the HAP crystallinity, treatment with H₂O₂, NaOH, and heating up to 400 °C did not create notable changes of HAP original crystallinity. On the contrary, HAP crystallinity was increased slowly from 400 to 600 °C, outstandingly from 600 to 800 °C and remained almost constant from 800 to 1000 °C.

Abstract: In this work, the effects of pH on the formation of hydroxyapatite (HA) and Sr-substituted HA (Sr-HA) were studied. Calcium nitrate tetrahydrate and strontium acetate were dissolved in ethanol at the Ca:Sr mole ratio of 9.5:0.5. Diammonium hydrogen phosphate was dissolved in deionized water. The two solutions were mixed thoroughly and the ammonium solution was added in order to adjust the pH of the solution. After precipitation, the system was subjected to the heat until the dried powder was obtained and then calcined at 600°C for 2 h. From XRD study, HA was found as the main phase in all calcined powders. The substitution of Sr for Ca in HA structure was confirmed by the shift of XRD peak to lower angles and the shifts of OH to higher wave number and PO₄ bands to lower wave numbers in FT-IR spectra.

Abstract: Pyrolysis is one form of energy recovery process which has the potential to generate oil, gas and char products. The char becomes an attractive by-product, with applications including production of activated carbons, which is useful as a ethylene sorbent for climacteric fruit packaging. In this work, activated carbon prepared from waste tire, produced as a by product of the bio-diesel extraction industry was prepared via chemical treatment with phosphoric acid (H₃PO₄) at three different char:H₃PO₄ ratios (1:1, 1:2 and 1:3) under fixed bed pyrolysis at 400, 500 and 600°C for 30 minutes in nitrogen (N₂) flow rate of 1000 mL/min and heating rate of 20°C/min. Result shows that char pyrolyzed at 800°C contained high fixed carbon and low volatile content favorable for subsequent activation process compared to other cases.(data not show here) Under the experimental conditions investigated, impregnation ratio of 1:2 were found to be suitable for producing high-surface area activated carbon. It was shown that H₃PO₄ did work effectively as dehydration reagent at approximately 600°C. The obtained carbons were characterized by nitrogen adsorptiondesorption isotherms at-196 °C. The surface area of activated carbons, which were determined by application of the BrunauerEmmettTeller (BET) and t-plot methods, were achieved as high as 833.50 m²/g. The chemically activated carbons were found to be mainly type II carbons and high adsorption property (Methylene blue adsorption = 622 mg/g and Iodine number = 899 mg/g).

Abstract: Rice husk is a form of agricultural biomass that provides an abundant silicon dioxides source. This study use rice husk ash as a material to prepare silica. Silica powder has been synthesized by the refluxing of rice husk ash with HCl 1,2 and 3 M at different time (60 and 120 min.) and subsequently adjusting the pH using 1 M. NaOH. The silicon dioxide extraction yield reached 85% and was effect by concentration of HCl solution and reaction time. The structure of the obtained silica powder were characterized by X-Ray Fluorescence (XRF), X-Ray diffraction (XRD), CIE L*a*b* (Visible spectrophotometer) and Scanning Electron Microscope (SEM). The highest purity of silica sample were 98.7% SiO₂, CIE L*a*b* = 94.79 +0.48 +1.24, ∆E ≈ 3.28 (white power) and 2Ɵ = 22^o (silica). Particle had a uniform size less than 3 μm. The objective of the next study will applied synthesized silica that enhances the print quality of the printing substrates.

Abstract: The strong enhancement when applying near-infrared excitation wavelengths, of totally symmetric modes of heme derivatives including β-hematin (malaria pigment), was hypothesized to be due to supramolecular interaction. Specifically, the intensity of the electron density or oxidation state marker band, ν₄, is in part strongly affected by CH(((X hydrogen bonding interactions when X is an electron-donating entity. Chlorotetra (p-methoxyphenyl) porphyrinatoiron (III), Fe (TMPP)Cl, is a model compound that supports this hypothesis. The single crystal X-ray structure of Fe (TMPP)Cl, recrystallized by vapor diffusion of diethyl ether into dichloromethane solution, was determined. There are π_por···π_por interactions and numerous additional supramolecular interactions in the form of CH···Cl and CH···O, and CH···π hydrogen bond interactions. The corresponding resonance Raman intensity of Fe (TMPP)Cl exhibited great enhancement of the ν₄ band when using 780 and 830 nm laser sources supporting the correlation of the strong CH(((X hydrogen bonding interaction and the strong resonance Raman enhancement of totally symmetric modes, especially ν₄, observed in malaria pigment supramolecular arrays when applying near-infrared wavelengths.

Abstract: Recent years, propolis has plenty of biological and pharmacological properties and its mechanisms of action have been widely investigated. There is a substantive database on the biological activity and toxicity of propolis indicating it may have many antibiotic, antifungal, antiviral and antitumor properties, among other attributes. The one-step incorporation of propolis into nanofibrous mats of polycaprolactone (PCL) by electrospinning was demonstrated. In this research, the preparation of the PCL nanofibers films added ethanolic extract propolis (EEP) by electrospinning technique was studied. The EEP content was varied from 0, 2, 4, 6, 8 and 10%. The morphology was observed by a scanning electron microscope (SEM). The functional group was investigated by FT-IR

Abstract: Glutinous rice starch (GRS) is produced from glutinous rice which is commonly cultivated in the Northeast of Thailand. GRS contains two types of glucose polymers which are amylose and amylopectin. Glutinous rice starch nanofibers (GNF) can be produced by an electrospinning technique. This is not a complicated method but needs a high voltage power supply. The aim of this study was to understand the production of GNF and physical-chemical properties of GNF. The morphology of GNF was examined by scanning electron microscopy. The characteristics of GNF are high porosity, flake multi-layers and a high swelling power. The Electrospinning technique did not change the chemical structure of GRS based on an FT-IR evaluation. This research revealed the basic characteristics of electrospun glutinous starch for use in various applications in the future.

Abstract: In the present study the effects of metal oxide nanoparticles addition on the microstructure, physical properties of the HA ceramics were investigated. Many techniques were used for the analysis. X-ray diffraction analysis revealed a co-exist phases between hydroxyapatite and tricalcium phosphate in the sintered samples. Addition of NiO resulted an increase in the lattice parameters of the tricalcium phosphates due to the bigger radii atom (Ni) substitution for the small radii atom (Ca). Energy dispersive spectroscopy suggested that most of NiO particles located at grain boundary, resulting in an improvement of hardness of the samples

Abstract: Porous alumina (Al₂O₃) ceramics were fabricated by powder injection moulding process. The feedstocks, composed of 44 50 vol% of Al₂O₃ powder, could be prepared using a composite binder, consisting of polyethylene glycol (PEG) and polyvinyl butyral (PVB). Debindings were carried out using a combination of water leaching of the PEG and thermal debinding of the PVB. It was observed that the removal of the PEG was fast at the initial stage and more than 90 wt% of the PEG could be removed within 4 hours. Sintering was performed in argon atmosphere at 1600 °C. The sintered specimens had apparent porosity in range of 26-32 %, depending on the feedstock compositions. The flexural strength values were in range of 90-140 MPa while the hardness values were in range of 5-9 GPa. It was found that both the strength and hardness of the specimens were increased with increasing powder loading.