română ANDREI TIBERIU CUCURUZ, ECATERINA ANDRONESCU, ANDREIA CUCURUZ, GEORGE PELIN
Abstract
The aim of this work was to prepare via in situ radical polymerization polymethacrylic acid/Al2O3 composite materials and to modify the structure of alumina with two silane coupling agents, 3-aminopropyl-trimethoxysilane (APTMS) and dichlorodimethylsilane (DMDCS). Also, the influence of silanization on the physico-mechanical properties of the resulting composite materials was studied. The surface modification of inorganic particles appears as an efficient technique to improve interactions between polymer matrix and nanoparticles.
The modification of alumina was investigated using transmission Fourier transform infrared spectroscopy that confirmed the success of the silanization procedure. The crystalline phase was identified using XRD analysis and the presence of alumina in the composite materials is demonstrated according to ASTM. Scanning electron microscopy revealed in all the analyzed samples alumina particles with spherical morphology that are embedded homogeneously in the organic polymer matrix. Also, the mechanical properties of composites were investigated based on xylene porosimetry and compression testing.
The composite materials synthesized in this study demonstrated a good potential for application in dentistry as dental resins or denture base materials.
Keywords
Alumina, Polymethacrylic acid, Composite materials, Denture base materials
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Year
2019
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Issue
49 (1)
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Pages
3-11
ELISABETA VASILESCU, VLAD GABRIEL VASILESCU, ION PĂTRAȘCU, BOGDAN GĂLBINAȘU
Abstract
The quality of metal - ceramic restorations is closely related to the quality of the metal - ceramic bond, where the rigidity of the metallic structure that prevents the occurrence of the flexural forces in the plating ceramic and in the interface area is an essential condition. Typically cast, the metallic component is made up of various metals and noble alloys or non-noble alloys.
Titanium and titanium alloys are at present an ideal solution due to their exceptional properties such as: corrosion resistance and high mechanical strength, density, thermal conductivity and reduced thermal expansion coefficient.
The research carried out aimed at studying the behavior of a new titanium alloy in metal - ceramic technology (Ti10Zr), a preliminary study on metal - ceramic bonding compared to conventional alloys (Ti6Al4V) and pure titanium (TiCp). The evaluation of the Ti10Zr-ceramic bond T22 Noritake was performed by mechanical tests, namely the shear resistance measurement and the determination of the final value of the force at which the ceramic component of the metal substructure is detached.
Mechanical tests were complemented by indirect, non - destructive methods of assessing the strength of metal - ceramic bonding.
The experimental results obtained confirm some results from the literature on the behavior of non - alloying alloys as substructures in metal - ceramic restorations, and on the other hand they can constitute novelty elements regarding the behavior of a new titanium alloy (Ti10Zr) as a component metallic in metal - ceramic technology.
Keywords
non - noble alloys, Ti10Zr bioalloy, metal - ceramic connection, mechanical tests metal – ceramic (M – C) prosthetic restoration, oxide, layer thickness, SEM analysis
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Year
2019
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Issue
49 (1)
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Pages
12-22
RADU KUNCSER, MARIA PARASCHIV, CRISTINA CIOBANU, OTTO BOSNIAK, MALINA PRISECARU, MOHAND TAZEROUT
Abstract
In this moment plastics provide a fundamental contribution in all activity fields: cars, aircraft, electronics, building, domestic daily activities, packing, etc. so the consumption of plastics has increased drastically. The disposal of plastic composite wastes is a serious environmental problem as they are not biodegradable. As a consequence, our work is focused in recycling of carbon fibers and glass fibers from waste composites through pyrolysis and partial oxidation.
Keywords
recycling, carbon fiber, glass fiber
MERUYERT KAYGUSUZ
Abstract
The sol-gel process has received a great deal of attention in the past decade due to advantages such as low temperature processing and high homogeneity of final products. The preparation of TiO2-SiO2-GLYMO composite by the sol–gel method is efficient at producing thin, transparent multi-component oxide layers. In this study, the preparation of TiO2-SiO2-GLYMO composite and its characterization were investigated. TiO2-SiO2-GLYMO nanocomposite was prepared from tetraethoxysilane (TEOS), titanium n-butoxide (TBO) and GLYMO (3-glycidoxypropyl)-trimethoxysilane) catalyzed with acid. Scanning electron microscopy (SEM) was employed to characterize the surface properties of composite films. The chemical structure of the composite was evaluated by means of Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Particle size was determined by a particle sizer. In summary, transparent and uniform nano colloidal TiO2-SiO2-GLYMO composite solutions were successfully synthesized though the sol-gel method. The turbidity values of the TiO2-SiO2-GLYMO composites were in the range of 8.4±0.4–12.7±0.6 ntu, and the pH values were in the range of 4.8 to 5.2. The particle sizes of the obtained composites were in the range of 5.9±1.3–22.1±1.2 nm. It was determined that the viscosity of the TiO2-SiO2-GLYMO composite solutions was approximately equal to 3-7 mPas. The thin transparent coatings obtained from these solutions were evenly distributed.
Keywords
TiO2-SiO2-GLYMO nanocomposite, Sol-gel, Leather, Finishing, Coating
VASILE MÎNZATU, CORNELIU MIRCEA DAVIDESCU, ADINA NEGREA, PETRU NEGREA, MIHAELA CIOPEC, COSMIN VANCEA
Abstract
Cellular glass is an insulation material that competes with polymeric and fibrous insulators on the market, having significant advantages such as the constant insulation efficiency, fire protection, corrosion and moisture resistance and long term dimensional stability. The present paper proposes a green solution to harness the exhausted composite adsorption material resulted from the removal of arsenic from wastewaters, by vitrification using two types of common recycled glasses: window panes and cathode ray tubes (CRT). Based on the high carbon amount present in the exhausted adsorption material, it was used as porogen material for cellular glasses. The apparent porosity, determined using the saturation under vacuum method, ranged between 40.25 - 62.15%. The optimal porous microstructure, having small uniform pores (under 150 m) and narrow dimensional scattering, was obtained using both exhausted adsorption material and silicon carbide. The hydrolytically stability, measured according to the ISO 719/1985, classifies all the investigated glasses in HGB1-HGB3 stability classes. The arsenic, lead and iron ions leachability were determined in accordance with the American Extraction Procedure Toxicity Test. No discernable losses of arsenic or lead (in the case of samples containing CRT recycled glass) were measured, regardless of time or environment’s pH. The amount of iron extracted after 28 days was very low, ranging from 0 to 0,056 % of the total iron. The thermal conductivity of the obtained cellular glasses range from 0.092 to 0.133 W/mK, classifying them as insulators. These results confirm the viability of the proposed alternative for immobilizing the exhausted adsorption material containing arsenic together with common recycled glasses as cellular glasses having high chemical stability and good thermal conductivity with multiple economic advantages.
Keywords
arsenic adsorption, arsenic wastes, glass recycling, cellular glass
COSMIN MIHAI MIRIŢOIU, CRISTIAN OLIVIU BURADA
Abstract
In this paper it is experimentally determined, using some known methods, the loss and damping factors, equivalent dynamic Young modulus and flexural rigidity for composite platbands with natural reinforcement. There were created created the next samples: from hemp and cotton, with 15 mm width and 4 respectively 6 mm thickness. Four layers were used for the cotton fibers with different proportion for the epoxy resin, obtaining samples with the mass of 38 and 98 grams. Four and five layers for the hemp fibers were used, obtaining samples with the mass of 38 and 98 grams. In addition to the dynamic values, the static mechanical characteristics (tensile strength, yield strength, static elasticity modulus, and so on) by tensile testing were obtained.
Keywords
damping factor, loss factor, Young modulus, bast, seed, hemp, cotton
T.P. MASHIFANA , F.N. OKONTA, F. NTULI
Abstract
The generation and disposal of phosphogypsum (PG) is a worldwide challenge, due to the environmental pollution posed by the material. The contaminants laden in the material are the major limitations for the utilisation of PG. Other materials considered as wastes such as fly ash (FA) and basic oxygen furnace slag (BOF slag) are generated by numerous industrial activities and disposed into environment. This study investigated the use of three wastes materials for the development of a composite applicable for road construction. Two types of PG were investigated, namely citric acid treated PG (TPG), for the removal of the contaminants and raw PG (RPG). Lower content PG containing 20% and 30% were investigated and modified with FA, Lime (L) and BOF slag. The effect of particle size distribution (PSD) on unconfined compressive strength development, durability of the composites and hydration products contributing to strength development were studied. Modification of PG with FA-L-BOF slag significantly improved the unconfined compressive strength of PG. The PG content of 20% for the RPG and TPG yielded the highest strengths of 7.4 MPa and 5.4 MPa, respectively when cure at elevated temperatures. Normal curing of the composites over 7 days and 28 also showed an increase in strength development. Particle size played a significant role in the unconfined compressive strength development. Kieserite, calcium aluminium sulphate and calcite were the predominant hydration products formed during the curing process.
Keywords
Phosphogypsum, environment, hydration, fly ash, slag
LEONID DVORKIN, VADIM ZHITKOVSKY , YURI RIBAKOV, OLEH BORDIUZHENKO , ANTON STEPANUK
Abstract
The paper deals with the features of obtaining a composite binder containing cement kilns dust, blast furnace slag and Portland cement, in which increased complex activation of blast-furnace granulated slag is achieved, due to the increased content of alkalis in cement dust, as well as the effects of hydroxide and calcium sulphate, contained in the cement. The influence of composition, fineness of grinding and content of chemical additives on the hydration degree and strength of low water demand binders was studied. The optimal relationships between the binder composition and the required fineness of the grinding are established, which ensure the strength characteristics and the hardening speed. The influence of superplasticizers naphthalene formaldehyde and polycarboxylate types, which provide low water demand of binder and high fineness of its grinding, is studied. Using the method of the experiment mathematical planning, equations for the regression of compressive and flexural strengths in different compensations were obtained, which allow predicting strength, taking into account the composition and features of the technology for obtaining the binder.
Keywords
binder, dust, kiln, grinding, hydration degree, strength
RADHIKA SRIDHAR, RAVI PRASAD
Abstract
This paper describes an experimental study on the behavior of engineered cementitious composites (ECC) accompanied by compressive, flexural and uni-axial tensile strength. In this experimental program, six sets of ECC mixtures with 2% total volume fraction of fibers were produced for each set of mixture and was proportioned to have the same material quantity such as silica sand, micro-silica and cement in order to determine the optimal percentage of polyvinyl alcohol (PVA) and steel fibers (SF). ECC mix proportion is designed experimentally by adjusting the amount of micro-silica and silica sand by conducting four-point bending, compressive and uni-axial tensile strength test of the ECC specimens. The test results emphasize that there is an improvement in ultimate flexural strength and ultimate tensile strength of the hybrid fiber reinforced cementitious composites with the addition of 1.5% of PVA and 0.5% of Steel fibers. High tensile strain capacity of about 25% has attained for the addition of 2% of PVA fibers, which indicates a superior ductility behavior of ECC specimens. Furthermore, the experimental results emphasize that there is a good correlation between flexural deflection capacity and tensile strain capacity.
Keywords
Hybrid fiber, four-point bending, uni-axial tensile, PVA, ECC
HÜSNÜGÜL YILMAZ ATAY, BERK ENGİN
Abstract
In our previous studies, we observed excellent flame retardant properties of mineral reinforced polymer composites. However, it was investigated that some mechanical properties of the composites were deteriorated concurrently with adding minerals. In this study, it was aimed to improve those features by using glass fibers and glass spheres. Polyproplyene is used as a matrix material. Huntite hydromagnesite and glass fibers/spheres were embedded to the matrix in different loading levels. Prior to the composite production, crushing, grinding and screening processes were applied to the mineral. After fabrication of the mineral and glass fibers/spheres reinforced polyproplyene composite samples, they were characterized by using Scanning Electron Microscope - Energy Dispersive X-Ray Spectroscopy (SEM-EDS) to investigate the elemental analysis and morpology. Tensile and flexural tests were applied to determine the mechanical behaviours. Finally Flame retardancy test was undertaken to observe the flame retardant properties of the composites. It was concluded that the use of glass fibers is a beneficial way to improve mechanical properties of mineral reinforced flame retardant composites.
Keywords
Flame retardant; Polymeric composites; Mechanical properties; Glass fibers; Glass spheres; Huntite hydromagnesite
ECATERINA MATEI, CRISTINA ILEANA COVALIU, ANDRA PREDESCU, GEORGE COMAN, CLAUDIA DRĂGAN, CRISTIAN VASILE NIȚU, CRISTIAN PREDESCU
Abstract
A Fe3O4@SiO2@TiO2 composite type was obtained using two synthesis methods in order to select the optimal method for future environmental applications, especially for the degradation of organic pollutants compounds found in water. Thus, a nanostructured magnetic core of Fe3O4 was coated with a SiO2 protective layer and subsequently functionalized using a Ti precursor. The functionalization process was developed both by the hydrothermal method (to obtain Fe3O4@SiO2@TiO2 -A) and by the sol-gel method, followed by evaporation (to obtain Fe3O4@SiO2@TiO2 -E). In both cases, the material was calcinated at 550 °C to obtain the stable form of anatase, known for its photocatalytic properties. It was found, following structural, morphological and stability investigations, that a composite with well-controlled homogeneity was obtained in the case of Fe3O4@SiO2@TiO2-E having also a higher tendency of agglomeration, which resulted in an increased particle sizes compared to Fe3O4@SiO2@TiO2 -A. Investigations on both composite materials have sustain their future use in photocatalytic processes.
Keywords
magnetic composite, photocatalyst, titanium dioxide, silicon oxide
I.V. MATSUKEVICH, I. ATKINSON, S.V. BASARAB, G. PETCU, S. PETRESCU, V. PARVULESCU, V. FRUTH
Abstract
The aim of the paper is to obtain nanocomposites based on magnesium oxide and metal nanoparticles, as well as to establish the influence of the preparation methods on the properties and photocatalytic activity of these materials. Magnesium oxide was obtained by two preparation methods namely precipitation and combustion synthesis. The obtained samples were characterized from the structurally, morphologically and compositionally point of view. Further, nanocomposites based on obtained MgO, were prepared by reducing metal ions to zero-valent metal nanoparticles immobilized on the surface of the MgO carrier (Cu and Ni). The photocatalytic activity of the synthetized nanocomposites was evaluated by monitoring the degradation of amoxicillin (AMX) aqueous solution under irradiation (365 nm).
Keywords
MgO, metal nanoparticles, nanocomposite, photocatalytic activity
ENIKÖ VOLCEANOV, ADRIAN VOLCEANOV
Abstract
The densification of pure Al2O3 and Al2O3–SiC composites (with 5%,10%, 20% and 30 % SiC) manufactured by the SPS process was remarkably enhanced due to additional diffusion mechanisms induced by the spark plasma even at low temperature (830 oC - 1050oC). The densification enhancement was attributed to the acceleration of the diffusion process due to additional mass-transport mechanisms induced by the spark plasma. The onset for densification of Al2O3– SiC composites was delayed with increasing amounts of SiC compared with the pure Al2O3 compact, respectively. The delay of the densification is thought to be due to the decrease in the grain boundary and lattice diffusivity, resulting from the second phase SiC dispersion. Therefore, in the composite case, higher temperatures for fully densification should be required to supplement the decrease in the diffusivity, compared with pure Al2O3. The thermal conductivity of SiC material is higher than that of Al2O3 particularly at elevated temperatures and consequently, the addition of SiC might be expected to promote heat transfer from the graphite die to the compacts. Finally, the enhancement of densification for the SPS process can also be attributed by considering the additional diffusion due to Joule heating, impact force and the electric field effect in which the diffusion of ions for sintering is accelerated by an applied electric field. It is reported that the generation of spark plasma at the insulating particle-to-particle contact points enhance densification. The monoclinic moganite-SiO2 was identified in the composite with 10% SiC particles as well as rombohedral α-Al2O3 and distortioned hexagonal and rhombohedral SiC polytypes. Also, a hexagonal AlC0.5O0.5 compound was revealed in the composites with 5-20% SiC and cubic Si was identified only in the composition with 30% SiC
Keywords
Spark plasma sintering, Al2O3–SiC ceramic, densification behavior, microstructure