Investigation of coaxial laser cladding process parameters influence onto single pass clad geometry of tool steel

ArticleThis paper is devoted to the investigation of the influence of technological parameters on the single pass clad geometry and quality as well as elemental composition in the clad after coaxial laser cladding (CLC). The objects of the investigation are components of expensive machines and tools for presswork needed to be repaired, i.e. refurbished for the future application with the goal of effective using of material resources in production. Nowadays such repair of worn tools is an actual task due to tendency for thrifty management of resources at affordable cost. Experimental work was carried out using CLC system, which consists of industrial robot and a ytterbium fiber laser with a core diameter of 100 μm, integrated to the coaxial powder supplying cladding head. During research separate cladding tracks of metal powder AISI М2 (particle size 53–150 μm) were deposited on the top surface of steel plates, which were grinded before treatment. This work’s highlighted parameters for variation were laser scanning speed and laser beam focus plane distance. The clad geometry was examined on cross-sections with SEM. Elemental composition was determined by the X-ray spectroscopy analysis. Gladding beads with good surface quality were achieved. Cross-sectional observation presented that clads has a good fusion with the base material without exfoliation. Keyhole shape of molten substrate area was achieved, which leads to increase of the dilution value. The future research is needed to achieve stable quality of cladding, which is extremely necessary for industry

Development of local strontium ranelate delivery systems and long term in vitro drug release studies in osteogenic medium

Funding Information: The authors acknowledge financial support from the Latvian Academy of Sciences though the ERANet under the frame of EuroNanoMed-II (Nanoforosteo, Project number: Z/14/1187) and the Riga Technical University and Riga Stardiņš University Cooperation Research Project No. RTU/RSU-18. Publisher Copyright: © 2018, The Author(s).It has been recognized that the operative stabilization of osteoporotic fractures should be followed up with an appropriate osteoporosis treatment in order to decrease the risk of repeated fractures. Despite the good clinical results of strontium ranelate (SrRan) towards the osteoporosis treatment, high drug doses and long treatment period cause an increased risk of serious side effects. Novel local SrRan/poly(lactic acid) (SrRan/PLA) delivery systems containing from 3.57 ± 0.28 wt% to 24.39 ± 0.91 wt% of active substance were developed. In order to resemble the naturally occurring processes, osteogenic media (OM) was used as a release medium for long term (121 days) in vitro drug release studies and UV/VIS method for the determination of SrRan content in OM was developed and validated. Biomimetic calcium phosphate precipitates were found on the surface and in the pores of prepared delivery system after microcapsule exposure to OM for 121 days as well as SrRan particles, indicating that the release of the drug have not been completed within 121 days. In vitro cell viability evaluation approved no cytotoxic effects of microcapsule suspensions and extracts.publishersversionPeer reviewe

In-vitro bioactivity, biocompatibility and dissolution studies of diopside prepared from biowaste by using sol–gel combustion method

Diopside was synthesized from biowaste (Eggshell) by sol–gel combustion method at low calcination temperature and the influence of two different fuels (urea, l-alanine) on the phase formation temperature, physical and biological properties of the resultant diopside was studied. The synthesized materials were characterized by heating microscopy, FTIR, XRD, BET, SEM and EDAX techniques. BET analysis reveals particles were of submicron size with porosity in the nanometer range. Bone-like apatite deposition ability of diopside scaffolds was examined under static and circulation mode of SBF (Simulated Body Fluid). It was noticed that diopside has the capability to deposit HAP (hydroxyapatite) within the early stages of immersion. ICP-OES analysis indicates release of Ca, Mg, Si ions and removal of P ions from the SBF, but in different quantities from diopside scaffolds. Cytocompatability studies on human bone marrow stromal cells (hBMSCs) revealed good cellular attachment on the surface of diopside scaffolds and formation of extracellular matrix (ECM). This study suggests that the usage of eggshell biowaste as calcium source provides an effective substitute for synthetic starting materials to fabricate bioproducts for biomedical applications

Tough photo-cross-linked PCL-hydroxyapatite composites for bone tissue engineering

Acrylate-based photo-cross-linked poly(ε-caprolactone) (PCL) tends to show low elongation and strength. Incorporation of osteo-inductive hydroxyapatite (HAp) further enhances this effect, which limits its applicability in bone tissue engineering. To overcome this, the thiol-ene click reaction is introduced for the first time in order to photo-cross-link PCL composites with 0, 10, 20, and 30 wt % HAp nanoparticles. It is demonstrated that the elongation at break and ultimate strength increase 10- and 2-fold, respectively, when the photopolymerization mechanism is shifted from a radical chain-growth (i.e., acrylate cross-linking) toward a radical step-growth polymerization (i.e., thiol-ene cross-linking). Additionally, it is illustrated that osteoblasts can attach to and proliferate on the surface of the photo-cross-linked PCL-HAp composites. Finally, the incorporation of HAp nanoparticles is shown to reduce the ALP activity of osteoblasts. Overall, thiol-ene cross-linked PCL-HAp composites can be considered as promising potential materials for bone tissue engineering

Combining bioresorbable polyesters and bioactive glasses: Orthopedic applications of composite implants and bone tissue engineering scaffolds

International audienceThis overview showcases the current state of the art in the fabrication, properties and applications of bioactive glass-polyester composites for dentistry, craniomaxillofacial surgery, orthopedics and bone tissue engineering. The combination of these materials is a successful strategy to simultaneously modulate and optimize the degradation rate, mechanical properties, cell response and osteostimulation of bone substitutes. Two major approaches can be identified: bone regeneration or bone repair. The first is performed using porous scaffolding materials, the second one by dense molded implants. For both strategies, the synthesis, processing and characterization of materials are presented based on a comprehensive review of the available literature. Relevant recent in vitro and in vivo studies are also covered. Current and potential future applications of this interesting family of biocomposites are discussed. The literature search revealed a considerable body of work investigating the biological performance of these composites, evidencing the interest on the topic. In particular, the use of polyester/BG composites is well-studied in terms of material fabrication, as well as characterization of physicochemical and in vitro biological properties. On the other hand, there is much less evidence of translational research efforts. It is apparent that future research will have to focus on the collection of more in vivo and clinical data to broaden the knowledge of the time dependent performance of these materials in realistic condition