Elena Manuela Stanciu

Wood-plastic composites based on HDPE and ionic liquid additives

The improvement of wood-plastic composites properties by additives and compatibilizers is a critical issue to produce value-added materials. High-density polyethylene-wood composites have been obtained through compression molding at 140xa0°C, using two types of additives, namely methyltrioctylammonium bis (trifluoromethylsulfonyl)imide and trihexyltetradecylphosphonium bis (2,4,4-trimethylpentyl) phosphinate room temperature ionic liquids. The ionic liquids improve the interfacial adhesion between the wood and the polymer phases, contributing to an increased stability of the material to water action and to an improved impact resistance and tensile strength in comparison with the reference. Also, the FTIR spectroscopy tests have proven a higher resistance of the ionic liquid-containing composites to accelerated photooxidation. Preliminary screening tests have also proven the antifungal character of the ionic liquids used in this study against brown rot (Postia placenta). This study opens new insights in the domain of polymeric composite materials, through documenting the possibility of blending new types of chemically distinct materials, difficult to be achieved by traditional functionalization/derivatization routes.

Dual Coating Laser Cladding of NiCrBSi and Inconel 718

This paper presents an alternative approach to obtaining crack- and pore-free NiCrBSiFeCuMoC hard coatings on a low alloy steel substrate through coaxial laser cladding, by using Inconel 718 as a buffer layer between the hard coating and the base material. The presence of the buffer layer reduces the overall cracking susceptibility of the hardfacing material by reducing the compressive stresses developed during the cladding process and ensuring a more uniform heat distribution gradient at the surface of the material than the base metal alone, which provides an additional hardness and wear coefficient increase of 7% and improves the corrosion resistance of the obtained materials by 20%, in comparison with the reference sample obtained without an intermediate layer, by using the same operational parameters and minimizes elemental dilution with the substrate. Our method could prove useful in increasing the quality and life cycle of expensive high-performance hard-coated materials, especially those working under demanding operational and environmental conditions.

Influence of the Electric Field Voltage on the Microhardness of the Layers Coated by Thermal Spraying

This study focuses on the analysis of the electric field voltage influence on the microhardness of the layers coated by thermal spraying. Based on the fact that the loads that are oppositely signed are attracted, an electric device of electric field generating in alternating current is developed, the electric field being generated between the metalizing gun and the work piece. Any metallic body that crosses the electric field is loaded with electric loads, which are yielded by an electric discharge when meeting the oppositely signed load. Thus, the physical and chemical properties of the layers coated by thermal spraying are improved by enhancing the powders displacement speed and by the appearance of micro weldings at the impact between the powder and the metalizing piece. After the samples analysis, an improvement of the diffusion zone is noticed and also an increasing of the microhardness for the samples at which the following voltages are used U = 30; 50; 70 [. In order to achieve the experimental samples, the CastoDyn DS8000 thermal spraying unit, the standard metallization module SSM 10 and the nickel based powder ProXon 21021 were used.

Edge Fillet Laser Welding of AISI 304 Stainless Steel

This investigation concerns the influence of key parameters of laser welding on the geometry and microstructural properties of the weld bead. The study is intended to restrain the interval field of the welding parameters and to investigate the welded joints achieved through this technique. A 3,3 kW Nd:YAG laser together with a Rofin welding head and an ABB 6-axes robot were used for this investigation. The tests highlight the major influence of the laser spot diameter on the geometry of weld bead. The experiments were made on various samples of AISI 304 thin sheets. In depth characterization of the weld area was conducted by means of optic and electronic microscopy and EDS analyses.

Photocatalytic performance of copper-based coatings deposited by thermal spraying

Visible light-activated photocatalysts are gaining general importance in advanced methods for removing persistent organic compounds. In this study, two types of composite oxide-metal coatings are obtained on copper substrates through thermal spraying of an aluminum bronze powder with different time-of-flight distances between the spraying nozzle and the substrate (150 and 200xa0mm). The surfaces of the coatings consist of nanopatterned α-Fe2O3 and CuxO produced by oxidation of the metal phase during the thermal spraying process. The optical band gap energies of the coating assemblies are 2.573 and 2.131xa0eV, respectively, and the Brunauer–Emmett–Teller (BET) specific surface areas are 4.65 and 4.87xa0m2xa0g−1, respectively. The photocatalytic performance of the two types of thermally sprayed coatings in the visible region is studied using methylene blue as a model compound. The coatings present remarkable stability in aqueous environments, good hydrophilicity, high photodegradation rates (0.20–0.26xa0h−1), high organic dye mineralization efficiencies (75.69 and 92.36%) and unaltered methylene blue removal efficiencies during three successive 12xa0h photodegradation cycles (91–99.60%).

Pulsed Laser Cladding of Ni Based Powder

The aim of this paper is to optimize the operational parameters and quality of one step Metco Inconel 718 atomized powder laser cladded tracks, deposited on AISI 316 stainless steel substrate by means of a 1064 nm high power pulsed laser, together with a Precitec cladding head manipulated by a CLOOS 7 axes robot. The optimization of parameters and cladding quality has been assessed through Taguchi interaction matrix and graphical output. The study demonstrates that very good cladded layers with low dilution and increased mechanical proprieties could be fabricated using low laser energy density by involving a pulsed laser.

Obtaining and Characterization of Polyolefin-Filled Calcium Carbonate Composites Modified with Stearic Acid

In order to obtain high performance calcium carbonate-reinforced HDPE and PP composites, the dispersibility and compatibility of the inorganic phase in the polymer has been achieved through surface treatment of the amorphous calcium carbonate filler with stearic acid. The surface coating of the inorganic phase has been proved by XRD and FTIR spectroscopy, through forming of an intermediate layer of calcium stearate which acts as a surfactant, efficient in providing an optimum compatibility with the dominatingly hydrophobic polymer matrix, as determined from the structural information obtained through samples cross-sections analysing.

A Comparison of Flame Coating and Laser Cladding Using Ni Based Powders

This paper addresses to the characterization of Ni based coatings realized by two different processes e.g. thermal spray coating and laser cladding. For the relevance of the experimental tests, the same base material, AISI 5140 and Metco 15E powder was used. The results highlight the advantages and disadvantages of the both techniques. The cladded layer obtained through laser cladding is pore and crack free, being characterized by a high hardness and a very good adherence to the substrate, while the flame coating presents oxides inclusions, high porosity, lower hardness and minimal dilution with the substrate as resulted from the EDS analyses. In depth characterization of the samples is made using optical and scanning electron microscopy, EDS analysis and microhardness testing.