Papers by Keyword: Strontium

Abstract: Effect of the synthesis temperature on strontium-modified cobalt ferrite nanoparticles using co-precipitation method has been conducted. Molarity composition of strontium is 10%, chosen to substitute in the cobalt ferrite nanoparticles. Synthesis temperature treatment (75 °C, 85 °C, and 95 °C) is tuned the crystalline structures and magnetic properties of the cobalt ferrite nanoparticles. XRD result showed that the pattern of characteristics appropriates ICDD 22-1086, which describes that all peaks are pristine cobalt ferrite. Furthermore, crystallite size decreases with increasing synthesis temperature, i.e., 25.32 nm, 23.55 nm, and 22.65 nm at the temperatures of 75 °C, 85 °C, and 95 °C, respectively. FTIR obtained shows an absorption band at around 590 cm^-1 (tetrahedral site) and 387 cm^-1 (octahedral site), which is absorption from the original cobalt ferrite. VSM test also revealed changing magnetic properties with synthesis temperature treatment. In addition, squareness ratio showed that the magnitudes were greater than 0.5, which indicates single-domain magnetic. Hence, the adjustment of the synthesis temperature at 95 °C has the highest potential to advance applications such as photocatalytic and/or antibacterial due to its smallest crystallite size.

Abstract: Polymethyl methacrylate (PMMA) is a polymer that is a suitable biomaterial for applications such as bone cement and replacement hip joints because it is inert, non-toxic, and has good mechanical properties. Hydroxyapatite (HA) is among the most thoroughly investigated bioceramics because its composition is similar to that of human bone and it has excellent biocompatibility and osteoconductive properties. Moreover, HA can be modified to regulate its physiochemical properties. In this study, boron and strontium were co-substituted into HA (SrBHA) to improve its biological characteristics. Previous studies have shown that strontium can increase bone density, although it negatively affects bone production. Moreover, boron helps to regulate the calcium balance to prevent bone loss. PMMA/SrBHA composites were prepared with different concentrations of SrBHA powder and the effects on the mechanical properties of the composites were investigated. The composites were fabricated using twin-screw extruders and compressed into test specimens using compression molding machinery. When the SrBHA powder concentration was <10 phr, the SrBHA particles were uniformly dispersed throughout the composite via a continuous polymer matrix reaction. Moreover, this concentration produced the greatest increase in compressive strength compared to the sample with no SrBHA (127.4 MPa). The composites were analyzed using energy-dispersive X-ray analysis, Fourier-transform infrared spectroscopy, and X-ray diffraction to determine the dispersion of the reinforced nanoparticles. Scanning electron microscopy (SEM) was used to analyze the dispersion of the SrBHA powder inside the matrix and to determine the causes of the fractures. The SrBHA powder improved the mechanical properties of PMMA, which is critical for applications in biomedical components. The mechanical tests and SEM analysis indicated that PMMA/SrBHA composites could be used for replacement joints and orthopedic implants.

Abstract: SBA-15 was modified with strontium before being functionalized with HPW acid to investigate its performance and stability in the glycerolysis of lauric acid. The physical and chemical characteristics of the catalyst were analyzed using Fourier Transformed Infrared (FTIR), Scanning Electron Morphology (SEM), BET surface analysis, Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD). The collective evidence and finding from material characterizations, including the successfully formed and retained SBA-15 mesopores after modification twice, SrO formation and disappearance, post-SrO modification and HPW incorporation, respectively, further strengthen the claim of the strong anchoring of HPW onto the SBA-15 via the strontium-salt bridge. The reusability of the lauric acid conversion was also evaluated. The superior stability of the synthesized catalyst (HPW/SrSBA-15) was demonstrated with minimal to no change in both lauric acid conversion (75.34%) and monolaurin yield (38.9%). Such a result was attributed to the good interaction between HPW and SBA-15 via strontium modification and proved that the catalyst does not undergo severe deactivation and showed good catalytic activity in recycled use.

Abstract: Mechanical strengths and electrical conductivity are the very important engineering properties of lightweight aluminum (Al) alloys used in automobiles, especially for battery-powered electric vehicles (BEV). However, the main issue is that the mechanical properties and the electrical conductivity of Al alloys are mutually exclusive. This study aims to simultaneously improve both the tensile properties and the electrical conductivity of the squeeze as-cast Al-6wt% Si-3wt% Cu by modifying its microstructure with the addition of nickel (Ni) and strontium (Sr). In comparison to those of the alloy free of Sr and Ni, the additions of 0.03 wt.% Sr and 0.5 wt.% Ni in the Al-6Si-3Cu alloy significantly improved the ultimate tensile strength, yield strength and electrical conductivity. This was because the addition of Ni element, as a transition element, collaborated with Cu to form fine intermetallic Al-Cu-Ni phases for dispersion strengthening. Also, the modification of the Si morphology from micron needles to nanoparticles by the Sr addition enhanced both the strengths and electrical conductivity of the developed alloy.

Abstract: For the first time, the time dependences of the temperature of aluminum, zinc and zinc-aluminum alloys alloyed with II A group elements under spontaneous cooling mode were obtained; an anomalous course and two characteristic times of the cooling process were found, and their mechanism was explained; the temperature dependence of the thermophysical properties of the investigated metals and alloys was established; the temperature dependence of the coefficients of convective heat transfer and radiation of Al, Zn and Zn55Al and Zn5Al alloys was experimentally determined; the influence of the concentration of II A group elements and temperature on the heat capacity and thermodynamic functions of Zn55Al and Zn5Al alloys was revealed.

Abstract: This study concerns the evaluation of the bioactivity and cells response of strontium (Sr) doped sol-gel derived S53P4 bioglass due to Sr induced osteoblast. Moreover it prevents in-vitro osteoclastic activity and is clinically used as osteoporosis treatment. The different amount of Sr was doped into the S53P4 bioglass formulation (53.82%SiO₂-1.72%P₂O₅-22.64%Na₂O-(21.76-x)%CaO-x%SrO) (x=0, 3 and 5 mol %) and synthesized via sol-gel method. These samples were denoted as 0Sr, 3Sr and 5Sr respectively. After soaking in Hank's balanced salt solution (HBSS) for 7 and 14 days, the apatite formation was examined using X-ray powder diffraction (XRD) and scanning electron microscope (SEM) techniques. Proliferation and alkaline phosphatase activity were evaluated using osteoblastic cell line MC3T3-E1. The XRD and SEM findings confirmed the hydroxyapatite (HA) structure on the bioglass surface after soaking. More intense HA peaks were observed in 3Sr specimen on 7 day while in 5Sr specimen on 14 day. Meanwhile, 3Sr specimen showed the highest cells proliferation and ‌ significant difference in alkaline phosphatase (ALP) activity than 0Sr and 5Sr. As a result, this finding indicates that S53P4 bioglass with 3 mol % SrO (3Sr) is a good candidate for bone tissue engineering because it allows for optimum cell proliferation and ALP activity while also having a high bioactivity efficiency.

Abstract: The article examines a number of regularities in the production of primary cast ingots of AlSi7Mg, AlSi7MgSr, AlSi11Mg, and AlSi11MgSr. Peculiarities of melting and cast of these alloys, as well as the effect silicon and strontium have on the formation of the shrinkage cavities, have been explored. It has been demonstrated that strontium, when used as a modifier, changes not only the morphology of silicon, but also the nature of solidification and shrinkage of the alloy. Defects formed in the ingots manufactured from near – eutectic AlSi11MgSr alloy have been studied in greater detail.

Abstract: Strontium (Sr) stimulates osteoblast and inhibits osteoclast activities in-vitro and is used clinically as a treatment for osteoporosis. In this research, the effect of Sr substitution on the apatite formation of sol-gel derived bioactive glass (BG) (55.90SiO₂-1.72P₂O₅ -21.67Na₂O - (20.69-x) CaO -x SrO) (x=0, 5 and 8 mol. %) were investigated. The synthesized Sr doped BG samples were treated in Hank's Balanced Salt Solution (HBSS) for 14 days to study the bioactivity. The achieved samples were evaluated by X-ray powder diffraction (XRD) and Scanning electron microscope (SEM). In XRD, the hydroxyapatite (HA) crystalline peak for 8% Sr-BG is less compared with others. When Sr amount is increased to 8%, the low crystalline peaks of HA were detected although the same soaking duration. FTIR spectra supported the delay precipitation of calcium phosphate (CaP), especially for the specimen containing 8% Sr. After 14 days soaking, SEM images confirmed the bioactivity of the synthesized samples by the formation of apatite on the glass surface.

Abstract: Nodular graphite cast iron or known as spheroidal graphite cast iron structurally has a spherical graphite morphology with a matrix consisting of a ferrite-pearlite phase. In general, cast iron has a main alloy consisting of carbon and silicon where both elements have an influence on the potential of graphitization and castability. In this work, the influence of strontium (Sr) added to molten cast iron with a composition of 0, 0.04, 0.06 and 0.08 wt% to graphite morphology were studied. The sample obtained will be carried out a characterization process by observing macro and microstructures using optical microscope equipped with image data processing software that displays graphite fraction, size, form and nodularity. Analysis showed that Sr addition increase in nodularization of graphite from 19.6 % to 31.5% at 0.08 wt% Sr addition.

Abstract: Cements have been used to encapsulate low and intermediate level radioactive wastes. Here, phosphate-modified calcium aluminate (CAP) cement is explored as an encapsulant for strontium radioanuclide-containing wastes. Electron microscopy indicates strontium chloride, used in place of strontium radionuclides, increases porosity in CAP possibly due to increased viscosity of CAP cement during mixing. X-ray diffraction analysis detects formation of halite phase suggesting strontium chloride reacts with cement to form sodium chloride not usually detected in CAP systems as well as formation of an amorphous phase in CAP cement when thermally treated at 90°C.