Papers by Keyword: Strontium

Abstract: Prussian blue analogue nickel ferrocyanide (NiPB) decorated carbon nanotube sponge (CNT sponge) was prepared as a newly designed spongiform adsorbent. This composite material was characterized by scanning electron microscopy (SEM), inductively coupled plasma (ICP) and tested in adsorption experiments. Results show that the CNT-NiPB sponge was equipped with large holes and porous structure, a large number of MWNTs and NiPB particles uniformly deposited on the surface and internal cavities. This adsorbent CNT-NiPB sponge showed a good adsorption selectivity of cesium and strontium in mixed aqueous solution, which is mainly induced by the ion exchange reaction of NiPB and metal ions. The novel spongiform adsorbent might have a promise prospect in radioactive wastewater treatment applications.

Abstract: The paper considers carbon, silicon and aluminum reduction of barium and strontium from natural materials by thermodynamic modeling in conditions of out-of-furnace steel treatment. X-rays phase and differential thermal methods of analysis were applied to investigate the samples of natural barium and strontium containing material. A process flowsheet of steel treatment by barium-strontium modifier in induction furnace was developed on the basis of carried out research.

Abstract: In the course of our investigations, AlSi8Cu3 foundry alloy was alloyed in different strontium and antimony concentrations. The mechanical properties of structure developed during the given cooling conditions as well as the effect of strontium and antimony on the modification of eutectic Si were investigated by a computer image analysis and by using a scanning electron microscope. Samples with a wall-thickness of 8 mm cast in the course of the experiment-series were used for our investigations. A part of our long-term research work is described in our present paper.

Abstract: In this study, modification of aluminium silicon eutectic alloy by grain modifier, strontium was investigated on conventional and slope cast A356 alloy. A356 alloy with addition of 0 to 0.97 wt.% Sr was prepared by conventional and slope casting in melting furnace. The molten metal of A356 alloy was casted into steel mould. Microstructure was observed using SEM. Phase analysis was done using XRD. Microhardness was conducted using Vicker microhardness. Microstructure of conventional cast displayed dendritic structure whereas slope cast displayed globular structure. Addition of Sr refined eutectic structure in both conventional and slope cast alloy. Phase analysis revealed the presence of Al2Sr phase in conventional cast Al-6Si-0.97Sr. Microhardness of the conventional cast alloy decreased with increasing of Sr up to 0.97 wt.%.

Abstract: Bioactive glass of the type CaO–SrO–P₂O₅–SiO₂ was obtained by the sol-gel processing method. Three samples containing 0 mol%, 5 mol% and 10 mol% of SrO were synthesized. The obtained bioactive glasses were characterized by the techniques such as, X-ray diffraction (XRD) and scanning electron microscope (SEM) and the effect of SrO/CaO substitution on in vitro biological properties of the synthesized glasses were evaluated and biocompatibility of the samples was measured using MTT assay. The results showed that incorporation of Sr in the obtained glass network did not result in any structural alteration of it due to the similar role of SrO compared with that of CaO. In vitro experiments with human osteosarcoma cell lines (MG-63) and MTT assay indicated that bioactive glass incorporating 5 mol% of Sr in the composition is non-toxic and revealed good biocompatibility.

Abstract: Hydroxiapatite (HA), one of the most widely employed bioceramic bone substitutes, when applied on its nanostructured form (nHA) may contribute to achieve a crystalline structure which is closer to the size and morphology of biological apatite. Furthermore, HA might also be doped with several different cations with biological effects including Sr2+. Therefore, a biomaterial based on nanostructured HA containing 1% Strontium (nSrHA) could present interesting biological properties, as strontium is described as a modulator of both osteoblast and osteoclast activities, presenting an important regulatory role on bone resorption. However, such modifications may also affect the biocompatibility of this material, which should be accessed initially by in vitro methods. Therefore, the present work aimed to evaluate the in vitro biocompatibility of 1% nSrHA discs with human primary osteoblasts through a multiparametric assay which assesses simultaneously metabolic activity (XTT assay), membrane integrity (NR test) and cell density (CVDE). Extracts of nSrHA, latex fragments (positive control), polystyrene beads (negative control) and nHA (for comparison) were prepared and exposed to 104 cells for 24h at 37°C/5% CO₂ on test plates, according to ISO 10993-5:2009, on quintuplicates. Cells exposed to unconditioned media were used as experimental control. After exposure, cells were tested for viability with a commercial multiparametric kit (In Cytotox, Xenometrix, Germany). The positive and negative controls presented the expected results, validating the assay. Both nHA and SrnHA were considered biocompatible, since the presented a cell viability after exposure statistically similar to the experimental control. In conclusion, the synthesized nSrHA discs are cytocompatible and, consequently, adequate for further in vitro tests on cell adhesion, proliferation and differentiation.

Abstract: Calcium phosphate is a widely used material as coating for metallic implants. This research describes a biomimetic coating techniques based on deposition of calcium phosphate films on a Ti6Al4V plates that was used to study the effect of strontium additive on the behavior of hMSCs. In this study, strontium additive was homogenously deposited onto calcium phosphate films on a Ti6AlV plates by using a biomimetic techniques. Strontium affected composition and morphology of calcium phosphate deposited on a Ti6Al4V plates to a varying degree, according to concentration of solutions used. The effect of strontium additive on proliferation and differentiation of hMSCs depended on the solution and concentration tested. In general, all individual three coatings showed decreased hMSCs proliferation. Strontium additive demonstrated a significant increase in differentiation into osteogenic lineage when compared with the control and calcium phosphate films without strontium additive. However, no cytotoxic effect of strontium additive in the concentrations tested was detected. The Fourier transform infrared spectra showed that this new coating closely resembles bone mineral. The techniques illustrated in this study mimics bone mineral containing strontium additive, making it constructive for studying basic processes of in vitro bone formation. The results showed in this study can be used for changing bone graft substitutes by addition of strontium additive on implants in order to affect their performance in bone repair and regeneration. Also, the system can aid rapid bone formation around the implant, reducing therewith the patient’s recovery time after surgery.

Abstract: In this work we show the effect of various concentrations of strontium and antimony on the level of modification in the Al-Si alloy. The scale of the modification rate was determined in two ways: thermal analysis was performed and the images of the samples. The eutectic temperature registered during the analysis were compared to the eutectic temperature of the unmodified alloy and on the basis of them was determined which samples are registered as modified, which are not. On the basis of the results of the cooling curves the partially modified category was introduced, if the ΔT value is less than 9°C and more than 7.5°C. The samples made of the alloys were examined with a computer image analysis and the samples were grouped on the basis of the size of the eutectic silicon phases. The aim of our research work was the examination of cross-effects of strontium and antimony.

Abstract: Aluminium AC4B alloy is widely used in automotive industries for various components. However, when this alloy is used to produce motorcycle cylinder head by Low Pressure Die Casting (LPDC) process, high reject rate was often found due to shrinkage, porosity and misrun. Addition of grain refiner and modifier is an alternative for this problem, through the control of solidification process that results in grain refining and microstructure modification. This study was aimed to investigate the effect of combination of 0.02 wt. % Sr modifier with variation of Ti grain refiner on the characteristics of AC4B alloy and the reject rate of cylinder head components. The Ti grain refiner was varied 0.063, 0.083 and 0.108 wt. % Ti and added at the holding furnace prior to LPDC process. A series of test was conducted including hardness test from the thin and thick regions of the part, tensile test, fluidity test, vacuum test as well as observation of microstructure by using optical microscope and Scanning Electron Microscopy (SEM) equipped with Energy Dispersive X-Ray Analysis (EDAX). The results showed that the higher the Ti content, the higher the hardness for both thin and thick areas, the lower the fluidity of the molten metal. At the maximum level of Ti of 0.108 wt. % and 0.02 wt. % Sr, the reject rate was significantly reduced from 3.59 % to 1.38 %.

Abstract: Effect of strontium (Sr) addition on the microstructure and the mechanical properties of semi-solid A356 aluminum alloy produced by GISS process were investigated in this study. Strontium addition resulted in both grain refinement and modification of eutectic Si. The maximum average ultimate tensile strength and elongation of 291.06 MPa and 17.31%, respectively, were obtained from the T6 heat-treated specimen containing 0.08wt%Sr. The excessive addition of strontium (0.2wt%Sr), however, seemed to deteriorate the mechanical properties of the alloy as a result of the Al₂Si₂Sr particle formation.