Key Engineering Materials Vol. 824

Abstract: Structural and spectroscopic properties of Ruhemann’s purple (RP) and its transition metal coordination complexes were calculated using theoretical chemistry techniques. The obtained information described RP and its coordination complexes with the transition metal ions [Cr(II), Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)]. The procedures involved calculations of what are called density functional theory (DFT) and time-dependent DFT (TD-DFT). These methods optimized what is called, in the codes of theoretical chemistry, the hybrid density B3LYP function employing the 6‐311++G(d,p) and LANL2DZ basis sets. The RP geometries, bond lengths, angles, quantum chemical parameters, and excitation spectra indicate that the RP is well able to coordinate with a transition element ion. Then the correlation of these theoretical results with experimental observations provides a detailed description of the structural and spectroscopic properties of RP compounds. The inclusion of solvent effects causes a blue shift in all theoretical excitation spectra. In summary, this work leads to an understanding of the characteristics of transition metal complexes with Ruhemann’s purple. These materials can be applied in forensic chemistry as reagents in developing latent fingerprints.

Abstract: The purpose of this work was to develop efficient ionochromic polydiacetylenes for lead ion (Pb²⁺) detection. The method developed used co-assemblies of polydiacetylene and anionic surfactant. The co-assemblies were prepared by mixing 10,12-pentacosadiynoic acid (PCDA) with sodium dodecyl sulphate (SDS) and subsequent UV irradiation-polymerization. The effects of mole ratio of PCDA to SDS, detection limit and stability were investigated. A color transition of poly(PCDA/SDS) co-assemblies with Pb²⁺ from blue to red was directly observed without the use of any technological equipment. However, Ni²⁺ and Fe³⁺ were non-responsive. The co-assemblies of poly(PCDA/SDS) showed rapid ionochromic response and selectivity to Pb²⁺ in aqueous solution. Based on this approach, the reagent has many advantages such as simple preparation, low cost, low chemical consumption and fast analysis. It is an alternative method for the development if sensing material for the detection of metal ions contaminating the environment.

Abstract: Monometallic catalysts have been prepared on nano-porous carbon support materials by way of hydrothermal carbonization of Cattail (genus Typha) leaves. The catalysts are for synthesis of biodiesel fuel. This research studied the effect of hydrothermal temperature (at 160-200 °C), reaction time (4-24 h) and the presence of KOH on the activated porosity of a carbon support. Then the type of loaded metal catalyst (Mn, Fe, Co, Ni, Cu and Pb), placed on the carbon support by an impregnation method, was investigated. This led to partial hydrogenation catalytic activity forming biodiesel. The carbonization temperature was studied in the range 500-900 °C for 2 hours. The samples were characterized by scanning electron microscopy, nitrogen sorption, fourier transform infrared spectroscopy and X-ray diffraction. The results indicated that the hydrothermal process at 200 °C for 12 hours exhibited the highest surface area, porosity and pore volume. This led to an appropriate distribution of metal on the carbon support surface.

Abstract: A low-cost process for the depolymerization of polyethylene terephthalate (PET) was investigated in this work by the development of catalysts derived from food wastes for the glycolysis reaction of post-consumable waste of drinking bottles. Bis (2-hydroxyethyl) terephthalate (BHET) is obtained as a product from the glycolysis of polyethylene terephthalate (PET). Calcium oxide (CaO) catalysts derived from shells were used in this reaction. The yield of bis (2-hydroxyethyl) terephthalate (BHET) was obtained and the purity of BHET was confirmed by NMR spectroscopy.

Abstract: Zeolite A and zeolite X was successfully synthesized from natural kaolin from Lampang province using calcination and two-step method of hydrothermal under the optimum conditions. Firstly, metakaolin was achieved by calcining the kaolin at 700 °C for 2 h. Secondly, hydrothermal experiments can be separated into two steps, the high temperature and short time of hydrothermal, metakaolin was mixed with NaOH to form hydrous sodium aluminosilicate, which was dissolved in dilute HCl. After the filtration, adjusted with deionized water to pH = 7 to form an amorphous aluminosilicate gel. Low temperature and longtime of hydrothermal, aluminosilicate gel was mixed with NaOH to form zeolite A and zeolite X. The optimum conditions for synthesis zeolite A is the high temperature and short time of hydrothermal with NaOH 8 M at 200 °C for 3 h and low temperature and longtime of hydrothermal with NaOH 1 M at 90 °C for 72 h. The optimum conditions for synthesis zeolite X is the high temperature and short time of hydrothermal with NaOH 8 M at 200 °C for 3 h and low temperature and longtime hydrothermal was NaOH 1 M at 90 °C for 120 h. The characterization of zeolite A and zeolite X were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy (FT-IR). Keywords: Zeolite A, zeolite X, Kaolin, Hydrothermal, Kaolin

Abstract: Generally, it is difficult to generate a high-performance pure blue emission organic light-emitting diode (OLED). That is because the intrinsically wide band-gap makes it hard to inject charges into the emitting layer in such devices. To solve the problem, carbazole derivatives have been widely used because they have more thermal stability, a good hole transporting property, more electron rich (p-type) material, and higher photoconductivity. In the present work, novel copolymers containing donor-acceptor-acceptor-donor (D-A-A-D) blue compounds used for OLEDs were investigated. The theory of the geometrical and electronic properties of N-ethylcarbazole (ECz) as donor molecule (D) coupled to a series of 6 acceptor molecules (A) for advanced OLEDs were investigated. The acceptors were thiazole (TZ), thiadiazole (TD), thienopyrazine (TPZ), thienothiadiazole (TTD), benzothiadiazole (BTD), and thiadiazolothienopyrazine (TDTP). The ground state structure of the copolymers were studied using Density Functional Theory (DFT) at B3LYP/6-31G(d) level. Molecular orbital analysis study indicated 3 investigated copolymers (ECz-diTZ-ECz, ECz-diTD-ECz, ECz-diBTD-ECz) have efficient bipolar charge transport properties for both electron and hole injection to the TiO₂ conduction band (4.8 eV). In addition, the excited states electronic properties were calculated using Time-Dependent Density Functional Theory (TD-DFT) at the same level. Among these investigated copolymer ECz-diTZ-ECz and ECz-diTD-ECz showed the maximum absorption wavelengths (λ_abs) with blue emitting at 429 and 431 nm, respectively. The results suggested that selected D-A-A-D copolymers can improve the electron- and hole- transporting abilities of the devices. Therefore, the designed copolymers would be a promising material for future development of light-emitting diodes, electrochromic windows, photovoltaic cells, and photorefractive materials.

Abstract: In this work, encapsulation technology—nanoemulsions (NEs) and nanostructured lipid carriers (NLCs)—was applied for color masking of betel nut extract for oral and skin applications. Types and extents of surfactant and lipid as well as homogenization process showed essential roles on physical properties of the encapsulated betel nut extract. Comparing to solution of betel nut extract in methanol, the degree of lightness of the optimized NE and NLC formulations improved more than 44 time compared to unencapsulated formulation. The optimized NE and NLC were most stable at 25 °C. Extreme storage conditions of 4 and 45 °C resulted in phase separation and color change, respectively. However, total phenolic and antioxidant activity were found stable during the stability test in all storage conditions. This work has shown a great potential use of nanoencapsulation technology in color masking plus maintain activities of betel nut extract for food as well as cosmetic application.

Abstract: Chromium aluminum nitride (CrAlN) has been extensively studied because of high hardness, high oxidation and corrosion resistance, and good wear resistance. However, utilizing substrate treatments such as heating and voltage biasing during film deposition usually leads to relatively high surface roughness that affects wear rates. It has been found that sputter deposition at low substrate temperatures can produce nano-grain coatings with enhanced structure and mechanical properties. For this reason, the CrAlN in this study was prepared by a reactive co-sputtering technique without the substrate treatments. Effects of Al content on structure and mechanical properties were investigated by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectrometry, atomic force microscopy, X-ray photoelectron spectroscopy, and nanoindentation. The results suggest that these CrAlN films formed as solid solutions by substitution of Al for Cr in the CrN crystalline structure. The deposition with increasing Al but fixed N leads to N deficiency, therefore at high Al content these films form under 1:1 stoichiometric nitride. This lowers film crystallinity and hence refined film morphology. Surface roughness and hardness of the films decreased from 5.737 to 1.135 nm and from 31.69 to 26.56 GPa, respectively. However, the solid solution strengthening arising from the further increase of the Al content causes these values to rebound to 2.466 nm and to 30.16 GPa.

Abstract: In this study, the effect of high Ca fly ash on the corrosion behavior and microstructure of Al6061 alloy matrix composite was investigated. The Al6061 matrix composites containing 5, 7, and 10 wt% of fly ash particles were prepared by the stir casting process. The corrosion behavior was investigated using potentiodynamic polarization measurement using 5 wt% NaCl. The results revealed that the I_corr increased from 2.44 µA/cm² to 8.60 µA/cm² as the fly ash concentration increased from 5 wt% to 10 wt%. This increase of I_corr indicates an increase of the corrosion rate. The corrosion mainly occurs at the interface between fly ash particles and Al 6061 matrix.