Papers by Keyword: Crystallinity

Abstract: Various polyurethane-based shape memory polymer was synthesized using polycaprolactone (PCL) as soft segment and, hexamethylene diisocyanate (HMDI) and isophorone diisocyanate (IPDI) as the hard segments. Palm kernel oil-based polyol was used to replace part of the petroleum-based polyol due to the increasing demand on renewable resources as a result of environmental awareness. The synthesis has been carried out using two step polymerization method. The effects of varying the molar ratio of IPDI/HMDI on material properties such as crystallinity, transition temperature, morphology, shape memory effect and tensile strength were investigated by using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), shape memory test and tensile test. A high IPDI content in SMPU results in better shape memory effect, whereas increasing HMDI content leads to a better chain flexibility. In this work, the incorporation of IPDI contributes to the formation of phase separation which enhance the formation of crystalline soft segment structure while the incorporation of HMDI as isocyanate tend to promote phase mixing which enhance the chain flexibility of the SMPU backbone.

Abstract: Bulk metallic glass matrix composites have emerged as new potential material for structural engineering applications owing to their superior strength, hardness and high elastic strain limit. However, their behaviour is dubious. They manifest brittleness and inferior ductility which limit their applications. Various methods have been proposed to overcome this problem. Out of these, introduction of foreign particles (inoculants) during solidification have been proposed as most effective. In this study, an effort has been made to delimit this drawback. A systematic tale has been presented which explain the evolution of microstructure in Zr_47.5Cu_45.5Al₅Co₂ and Zr₆₅Cu₁₅Al₁₀Ni₁₀ bulk metallic glass matrix composites with varying percentage of ZrC inoculant as analysed by secondary electron and back scatter electron imaging of as cast unetched samples. A support is provided to hypothesis that inoculation remain successful in promoting phase formation and crystallinity and improve toughness.

Abstract: To date, flexible, sensitive and biocompatible pressure sensors for fluctuation signals in human body have been mainly demonstrated for detecting body and muscle motion, pulse rate, heart rate and arterial blood pressure. However, because of the lack of sufficient sensitivity and flexibility, pulse signals with relatively low intensity cannot be identified and captured, such as signals derived from microcirculation in human body. As confirmed and validated by researchers, once PVDF and its copolymer based nanocomposite sensing material are applied in piezoelectric sensors, its sensitivity and piezoelectricity are highly relevant. Therefore, as one of the most effective methods to improve the permittivity and piezoelectricity of PVDF and its copolymer based nanocomposite, the effect of increasing the content of β-phase crystal was investigated in this work. In this project, the sensor possessing a novel sensing layer with the nanofiller was investigated and fabricated. The proposed sensor was designed in a simple but efficient sandwich structure. The sensing layer of the proposed sensor was made of polyvinylidene fluoride (PVDF) and polyvinylidenefluoride-trifluoroethylene (PVDF-TrFE) based nanocomposite with Zinc Oxide (ZnO) nanostructure acting as a filler portion which was fabricated by the method of Chemical Bath Deposition (CBD). The fabricated nanocomposite sensing layers were characterized. The microstructures and morphologies of pristine PVDF (P), PVDF-TrFE (PT), PVDF/ZnO (P/Z) and PVDF-TrFE/ZnO (PT/Z) with different concentration were characterized by Scanning Electron Microscope (SEM). The degree of crystallinity for P, PT, P/Z and PT/Z was obtained by X-ray Diffraction meter (XRD). In conclusion, PT exhibited better performance in both morphology and crystallinity as a sensing membrane material. More β‐phase in PT was obtained than that in P. ZnO, as a semiconductor filler, would have substantial influence on enhancing the dielectric constant by acting as a nucleating agent and forming a nanostructure with large aspect ratio.

Abstract: In this article, the supercritical carbon dioxide (Sc-CO₂) was used as a medium for hot-drawing of F-III fibers. The conditions of hot-drawing were selected to be the temperature of 250 °C, pressure of 14 MPa, time of 60 min, and different tensions, which were 0, 3, 4.5, 6, and 7.5 g·d^-1, respectively. All samples including the untreated and treated F-III fibers were characterized by a mechanical tester and X-ray diffraction (XRD). Results showed that the Sc-CO₂ and applied tension could both promote the crystallinity and degree of orientation of F-III fibers at a temperature below the Tg of F-III fibers in Sc-CO₂. Moreover, compared with the untreated, the tensile strength and modulus of treated F-III fibers tended to increase with the increase of tension in the range of 0 ~ 6 g·d^-1. In summary, this provided a new treatment mode for the hot-drawing of fibers.

Abstract: The aim of this work is to investigate the influence of sintering temperature on purity and crystallography properties of carbonated hydroxyapatite (CHAp). The CHAp was synthesized using a coprecipitation method. The snail shells (Pilla ampulacea) were processed to yield calcium oxide as the calcium source in synthesis. The CHAp powder then was sintered for 2 h in an air atmosphere at 400, 600, 800, and 1000°C. An X-Ray diffractometer (XRD), Fourier transform infrared (FTIR), scanning electron microscope (SEM), and energy dispersive x-ray (EDX) are used to investigate the physicochemical properties of CHAp. XRD, FTIR, and EDS results show primary phase is carbonated hydroxyapatite. Calcium oxide as a secondary phase is detected starting from 800°C. The crystallinity and crystallite size are increased along the increasing of sintering temperature. Drastic enhancement on these properties is shown at 600–800°C. However, there is no simple relation to the sintering temperature and lattice parameters. These results show that sintering temperature has an important role in the purity and crystallography properties of the CHAp.

Abstract: The paper describes the process of recrystallization of portlandite of limestone mortar in calcite. The degree of crystallinity of calcite in limestone mortar of some medieval objects of the north of the Byzantine oecumene is shown through the example of Abkhazia and calcite in natural limestone and marble. The work provides a comparative analysis of the calcite crystallinity and the estimated age of the building objects according to historical and architectural data. It is proven that the higher the calcite crystallinity is the elder the lime mortar and, accordingly, the architectural object is.

Abstract: Tin-doped indium oxide or indium tin oxide (ITO) has many promising uses in applications, such as, transparent conductive oxides, flat panel displays, and energy-saving windows. In this work, nanorice particles of tin-doped indium oxide (ITO) were obtained by a simple sol-gel method. Indium salts and stannous fluoride precursors were mixed ultrasonically in an aqueous medium. The crystallinity and chemical bonds were studied by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). FTIR spectra before calcination showed the characteristic bonds of In–OH and Sn–OH at 1160 cm^-1 and 1380 cm^-1, respectively. After calcination at 400^°C for 2 h, these characteristic bonds disappeared, confirming the formation of crystalline oxide. Moreover, scanning electron micrographs revealed well-defined structure, called nanorice, emerging from controlled crystal growth at 85^°C for 90 min. The particle size of ITO was approximately 500 nm in length and diameter of 150 nm. The effect of crystallinity was studied by UV absorbance and NIR reflectance. These demonstrated promising results for use as energy-saving windows.

Abstract: A research has been conducted to activate natural zeolites from Mamasa, West Sulawesi with sulfuric acid and heating which is then used as a catalyst for cracking palm oil methyl esters. This type of research is preliminary research. The acidification process is carried out by mixing fine natural zeolites with 0.2 N H2SO4 solution, accompanied by heating at 110 °C. Then zeolite is calcined at 600 °C for 3 hours. The result of zeolite X-Ray diffraction (XRD) analysis shows that Mamasa natural zeolite has mordenite. The crystallinity of natural zeolites is 60.8%, increasing to 68.6% after activation. Catalytic cracking is carried out by heating methyl esters (biodiesel) and active zeolite zeolite catalysts in a fixed bed reactor in several temperature variations (140, 160, and 180 °C), reaction time of 5 minutes. The results of the saponification number analysis show that cracking products have a greater saponification number (224.4 mg KOH/g oil) compared to biodiesel before cracking (220.2 mg KOH/g oil), so it is assumed that the carbon cracking carbon chain is shorter.

Abstract: Titanium alloy & stainless steel are major materials for bone fracture fixation such as bone screws and plates in today's medical devices. However, the fixation devices made of metal not only have the risk of metal ion release to cause human allergies, but they also need to be removed by a second surgical operation making pain and the risk of the patient’s wound infection after the bone fracture healing. The biodegradable Polylactic Acid (PLA) bone screws & bone plates have the great advantage of not needing a second operation, but their insufficient strengths make them not be widely used in the current bone fracture fixation. In the study, we use PLA as the matrix and in-mod heat treatment with induction coils to increase the strength of bone screw & plate by improving crystallinity of material. Regarding ASTM F2502 “Standard Specification and Test Methods for Absorbable Plates and Screws for Internal Fixation Implants”, we measure bending loads of test pieces before and after in-mold heat treatment, and obtain the optimized process parameters by Taguchi method that will increase the bend load of PLA bone plates by 34.82%. These optimal parameters are the injection speed of 80 mm/s, the melt temperature of 205 °C, the heat treatment temperature of 110 °C and heat treatment time of 20 min.

Abstract: This work focuses on the effect of functionality of hydroxylated natural rubber (HNR) and its loading on crystallinity and mechanical properties of polylactic acid (PLA). HNR with hydroxyl groups of 9.09% by mole was prepared from natural rubber latex via epoxidation reaction and then the epoxy rings were cleavaged to produce the hydroxyl groups by using heating at the temperature of 70 °C. HNR4 with the hydroxyl groups of 15.25% by mole was prepared from ONR4 latex with M̅_n of 3.94 × 10³ g/mol and M̅_w of 5.06 × 10³ g/mol. PLA was then blended with the obtained HNR or HNR4 with different weight ratios of PLA:HNR = 70:30 and 60:40. It was found that hydroxylated natural rubber increased the crystallinity of molded PLA sheet from 7.54% to 18.20% for molded PLA:HNR = 70:30 sheet, to 25.16% for molded PLA:HNR = 60:40 sheet and to 24.38% for molded PLA:HNR4 = 70:30 sheet. Morphological analyses revealed the appearance of co-continuous phase in the molded PLA:HNR4 = 70:30 clearer than the molded PLA:HNR = 60:40 and molded PLA:HNR = 70:30 sheets. As a result, it clarified that the higher functionality of hydroxyl groups based on lowering the molecular-weight enhanced the compatibility between PLA and HNR. On the other hand, the mechanical properties of PLA:HNR4 = 70:30 were found to be the highest tensile strength (14.46 MPa), elongation at break (13.62%) and modulus (4.10 MPa) though PLA:HNR = 60:40 gave the highest impact strength of 163.98 J/m. This was believed that the hydroxylated natural rubber enhanced the crystallinity and impact strength of PLA through the interface interaction and/or chemical bonds between hydroxyl groups of HNR and carboxyl terminal groups of PLA.