Materials Engineering 2017

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Authors: Zane Grigale-Soročina, Ingmārs Birks, Mārtiņš Kalniņš
Abstract: Nail polish as a system used in cosmetics still faces stability issues. Pigment sedimentation and syneresis are the most common problems for solvent based systems. The scope of this research was to produce a working 'gel' dispersion for use as a suspension agent in nail polish systems. Various thixotropic agents (hectorite and bentonite clays and hydrophobic and hydrophilic silica grades) and methods (high shear homogenisation (HSH) and high pressure homogenisation (HPH)) were employed to affect this result. From the rheology results it is concluded, that the HPH ensures the development of the systems with the required viscosity recovery properties. It is also concluded that high shear developed systems with hydrophilic silica thixotropic agent are well suited for use as a suspension agent in nail polish formulations.
Authors: Michaela Gedan-Smolka, Katrin Schubert, Antje Täger, Hagen Marks
Abstract: For electrostatic coating application Sheet Molding Composites (SMC) have to be modified antistatically. By a novel approach several monomeric and polymeric ionic substances were incorporated into the duromeric bulk phase and tested in terms of its antistatic effectiveness. Furthermore the influence of selected additives on the SMC thickening and molding procedure as well as resulting mechanical properties of modified SMC-panels and the powder coating application were studied.
Authors: Zilgma Irbe, Armands Buss, Dagnija Loca, Lasma Malniece
Abstract: α-Tricalcium phosphate (α-TCP) is an important reactive component in calcium phosphate bone cements which are used for the bone tissue regeneration and augmentation. By thermally treating amorphous calcium phosphate (ACP) at relatively low temperatures (650–900 °C), it is possible to obtain sub-micrometre or nanosized α-TCP particles. In the current research, it is shown that the aqueous synthesis environment where ACP is precipitated has significant influence on the stability of ACP and the α-TCP content in the thermally treated products. During ACP synthesis pH must be kept basic. While it is possible to synthesize ACP if potassium hydroxide or sodium hydroxide is used to raise the pH of synthesis, ammonium ions also must be present in the solution to obtain α-TCP after thermal treatment of ACP. If sodium hydroxide is used, higher α-TCP content is obtained (compare 89 % and 66 %). Increase of Ca/P ratio stabilizes ACP and allows to obtain products with high α-TCP content. Increase of both calcium and phosphate ion concentration in the synthesis destabilizes ACP and reduces the amount of α-TCP in the product (twofold increase reduced α-TCP content from 89% to 2%).
Authors: Janis Zarins, Mara Pilmane, Elga Sidhoma, Ilze Salma, Janis Locs
Abstract: Variety of different bone substitutive materials are synthetized to improve bone healing potentials in pathological bone conditions. Physiologically active molecules within biomaterials, can initiate expression level of biomarkers, regulating bone remodeling. Aim of our study was to analyze bone healing process in bone defects followed by implantation with 5% strontium substituted hydroxyapatite (HAP) /tricalcium phosphate (TCP) 70/30 granules (group A) or HAP/TCP biphasic ceramic granules without strontium substitution (group B), or sham surgery affected bone (group C) in osteoporotic rabbits’ femur. Tissue samples from contralateral intact left leg were used for evaluation of systemic effects after surgery. Changes of bone volume were measured and appearance of OPG, NFkB-105, OC, COL-1, BMP-2/4, MMP-2, TIMP-2, IL-1 and IL-10-positive osteocytes in osteoporotic rabbits’ bone defect were evaluated. No statistical difference between groups of trabecular bone volume was detected. All analyzed markers showed higher appearance of positive osteocytes in groups A and B with comparison to control left leg (p<0.05). Only NFkB105-positive cells showed important difference between sham surgery affected leg and control one (p=0.034). Numerous OPG-positive cells appeared in group A, while moderate number of them was found in groups B and C (p=0.025; p=0.027). Numerous to abundant OC-positive osteocytes were detected in group A, while moderate in group C (p=0.034). Statistical difference of rest biomarkers between groups was not detected. We concluded that implantation of biomaterials in osteoporotic bone improves local bone regenerative properties. However, the notable increase of OPG-containing cells proves the increase of osteoclastogenesis suppression and gives the evidence for renew of bone functionality.
Authors: Halima Ait Mahamed, Hakim Aguedal, Hafida Hentit, Abdelkader Iddou, Khaled Mekhissi, Abdallah Aziz, Jean Claude Jumas, Andrei Shishkin
Abstract: This work presents the possible recovery and reuse, after treatment, of an iron-based sludge from wastewater treatment station in the removal of cadmium in aqueous solution. The sludge sustained a heat treatment (100 and 500°C) and was characterized by XRD, FTIR, BET and SEM witch shown an evolution in the morphology and the structure of the materials indicating the effect of the heat temperature. The material was then applied to remove cadmium in aqueous solution. The results show that the raw material gives the best results with a maximal adsorption capacity of 70.92 mg/g at pH=5.This study has shown us that it is possible to recover and reuse effectively sludge, from wastewater treatment plant, considered as a solid waste, in the removal of a pollutant such as cadmium in aqueous solution.
Authors: Belkacem Bouacherine, Abdelkader Iddou, Hafida Hentit, Jean Claude Jumas, Abdallah Aziz, Andrei Shishkin
Abstract: This work is in addition to the various works undertaken by the researchers, using biomass as adsorbent. However, the aim of this study is the recovery of a marine material alga: Ulva lactuca) that we were able to transform into adsorbent with treatment under physical carbonization and chemical activation. The ability of treated and untreated Ulvala ctuca, to remove hexavalent chromium Cr (VI) ions in aqueous solutions was investigated. The influence of pH, sorbent dose, initial concentration, temperature, and contact time has been studied in batch process. The materials are characterized by FTIR and SEM analysis. The highest Cr (VI) removals (100%) were achieved at pH of 3, particle size of less than 250μm, dose of 1 g/L, and equilibrium time of 180 minutes. Thermodynamic results indicated that the Cr (VI) adsorption process was spontaneous and exothermic. The adsorption data fit well with Langmuir isotherm model with a maximum adsorption capacities (qmax) of untreated and treated Ulva lactuca were between 0.6 and 2 mg/g. Higher Cr (VI) removal revealed the practical applicability of Ulva lactuca in water and wastewater treatment systems.
Authors: Laura Neimane, Andrejs Skagers
Abstract: Sinus floor augmentation operations with calcium phosphate materials are performed when natural maxillary bone quality and quantity fail to be able to support titanium dental implants. Sinus floor augmentation can be done in one step operation when titanium implant is inserted at the same time when calcium phosphate materials. This type surgery can be done if there is enough maxillary alveolar bone height to stabilize the implant. If there is not enough bone then two step maxillary floor augmentation is performed when dental implant is placed after few months. Calcium phosphate materials are often used for maxillary sinus augmentation. These materials cause remineralization of residual maxillary alveolar bone [1]. That can be observed histologically [2,3]. However histological evaluation often means interference. Radiological investigation can be used to examine postoperatively augmented area. Nowadays cone beam computed tomography (CBCT) is the radiological method of choice for maxillofacial region due to low radiation and high quality images. There was no date found in literature on maxillary bone remineralization measured in voxel grey value density (VV) on CBCT. Rotation movement of CBCT cause beam hardening artifacts [4,5] that can alter correct measurements of bone and augmentation zone radiodensity. The aim of this study was to calculate remineralization of maxillary alveolar bone after augmentation with calcium phosphate materials radiologically and degree of artifacts created by titanium dental implant in CBCT images.
Authors: Mustafa Arda, Metin Aydogdu
Abstract: In the present study, buckling of eccentrically loaded nanobeams in which the load is not applied at the centroid of cross section, has been studied. Eringen’s Nonlocal Elasticity Theory has been used in the formulation of governing equation of motion of the nanobeam. Simply supported and free boundary conditions for nanobeam have been taken consideration. The effect of nonlocal parameter, eccentricity of the load, nanobeam length on the buckling deflection and critical buckling load on nanobeam have been investigated. Present results can be useful in the design of nano-structures.
Authors: Radomila Konečná, Ludvík Kunz, Pavel Pokorný, Gianni Nicoletto
Abstract: Growth of long fatigue cracks in Ti6Al4V alloy manufactured by direct metal laser sintering (DMLS) was investigated. Two DMLS systems, EOSINT M270 and EOSINT M290, with different process parameters were used for production of CT specimens having three different orientations of crack propagation with respect to the DMLS build direction. The as-built specimens were stress relieved at 740 °C. The fatigue crack growth curve and the threshold values of the stress intensity factor for crack propagation were experimentally determined. It has been found that the chosen DMLS processing parameters and the used stress relieving procedure results in material exhibiting isotropic crack growth behavior, i.e. the crack growth was found to be independent of the DMLS build direction. The fatigue crack growth rates and the threshold values for the crack growth were compared with published results characterizing the as-built material and material after different post processing heat treatments.
Authors: Kristjan Juhani, Jüri Pirso, Marek Tarraste, Mart Viljus, Sergei Letunovitš
Abstract: Present paper discusses the influence of spark plasma sintering (SPS) on the microstructure and perfomances of chromium carbide based cermets. The effect of SPS parameters (temperature, pressure) is discussed. It is shown that SPS enables to produce more fine grained chromium carbide based cermets compared to conventional liquid phase sintering. Hardness and fracture toughness are exhibited.

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