română ADRIAN-IONUȚ NICOARĂ, ALINA-IOANA BĂDĂNOIU, GEORGETA VOICU
Abstract
Intumescent materials have the ability to swell when are subjected to fire or thermal treatment. This type of materials is used for passive fire protection in buildings, providing thermal protection or sealing the penetrations in walls preventing fire spreading in adjacent rooms.
In this paper is presented the synthesis of intumescent alkali activated borosilicate inorganic polymers (AABSIPs) by the alkaline activation of waste glass powder (WGP) with NaOH or/and KOH solutions and borax additions.
The partial substitution of NaOH with KOH, in alkaline activator composition, improves the workability of fresh AABSIP pastes, as well as the volume increase during the intumescence process. By fine tuning of various parameters (alkali activator composition, water to solid ratio) is also possible to modify the activation temperature of intumescence process.
Keywords
Geopolymer, intumescent, fire protection, alkaline activation, waste glass
CRISTINA GHITULICĂ, SIMINA ȘTEFAN, OTILIA RUXANDRA VASILE, ROXANA TRUȘCĂ, IONELA ANDREEA NEACȘU, BOGDAN ȘTEFAN VASILE
Abstract
The aim of this study was to synthesize and characterize a ceramic material with a high porosity, which can be used as a support for the microorganisms’ colonies for water purification. Given the target application, in order to obtain a composition of the ternary system MgO - Al2O3 – SiO2, there were selected two natural materials: kaolin and talc powders. The chosen processing method involves mixing the ceramic powder with a porogen organic compound, in order to achieve a homogeneous suspension. Sintered ceramic samples were characterized in terms of ceramic properties, microstructure and phase composition using laser granulometry, Hg porosimetry, X-ray diffraction and scanning electron microscopy. The growth and activity of biofilm was investigated.
Keywords
silicates, environment, biomaterials, ceramic filter, microorganisms
MARIA P. NIKOLOVA, STEFAN VALKOV, RODICA IOSUB, EMIL YANKOV, PETER PETROV
Abstract
An approach to surface modification for direct formation of nanosized anatase over cathodic arc PVD deposited (Ti,Al,V)N coating at a temperature of about 150 °C is proposed. In order to determine the surface structure influence on the electrochemical properties, bare and coated samples were exposed to Ringer-Braun physiological solution. The aim was to compare their corrosion performance (impedance characteristics, obtained by means of EIS and cyclic voltammetry (CV)) during immersing over an extended period of time - 2 hours, 1 and 7-days while the average temperature was close to the human body level (37±1°C). The capacitive behavior of the coated sample indicates a phase angle close to 71º and slightly decreasing impedance modulus /Z/ because of disruption by the high initial hydration and ions diffusion from the saline. The corrosion resistance of the coated system decreases as a function of time as a result of the thin oxide dissolution and lack of re-passivation of the nitride. The characterization of the surface layer of the coating was obtained by scanning electron microscopy (SEM), glow discharge optical emission spectrometry (GDOES), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis of core electron levels.
Keywords
biomaterials, nanostructures, metallic materials, materials research, PVD coating
GEORGETA VELCIU, ALINA MELINESCU, VIRGIL MARINESCU, VICTOR FRUTH, CRISTIAN HORNOIU, MARIA PREDA
Abstract
Two types of La0,6Sr0,4Co3-δ and La0,5Sr0,5Co3-δ compositions were studied. The preparation of mixtures from La2O3, SrCoO3 and Co3O4 was made by mechanical activation. The obtained powders have a monomodal distribution of particle sizes and low dispersion. Reactions occurring in the formation of compounds in these mixtures were studied by complex thermal analysis. The two compositions have been sintered at a temperature of 1250°C. The mineralogical composition determined on thermally treated samples showed that in case La0,6Sr0,4Co3-δ compound a solid solution was formed with the cubic structure derived from LaCoO3, and for La0,5Sr0,5Co3-δ a solid solution with a hexagonal structure corresponding to SrCoO3. The samples formed single-phase at 12500C. The electrical conductivity measurements showed a semiconductor behavior for La0,6Sr0,4Co3-δ, and conductor behavior for La0,5Sr0,5Co3-δ.
Keywords
solid solution, electrical conductivity, SEM
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
I.M. SUTJAHJA , A. O. SILALAHI, S. WONORAHARDJO, D. KURNIA
Abstract
Determination of thermal conductivity based on temperature history (T-history) method is low in cost and can be applied directly to some samples, as it depends only on the number of temperature sensors used in a measurement. However, very little published data has reported the solid and liquid thermal conductivities of phase-change materials (PCMs) based on this analytical method. The thermal conductivity based on T-history data is related to other thermophysical parameters of the PCM, such as the solid and liquid specific heats and the latent heat of the solid–liquid phase transition. This report analyses the solid and liquid thermal conductivities of CaCl2·6H2O as an inorganic PCM, using thermophysical parameters obtained from two methods of analysis, namely the T-history method proposed by Zhang et al. and its improvement by Hong et al. (Z/H) and Marin et al. (M) based on the temperature-dependent enthalpy curve. The data predict the enhancement of thermal conductivity with 1 wt.% ZnO nanoparticles as a dopant, which permit effective heat transport in the material in response to environmental heat.
Keywords
Phase-change material (PCM), CaCl2·6H2O+ ZnO dopant, T-history method, solid and liquid specific heats, heat of fusion, enthalpy-temperature curve, solid and liquid thermal conductivities
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
ZENO GHIZDAVET, ALINA CORNELIA BACIU, DANIELA ILIE, MIRELA IONELA LECHES
Abstract
A technological issue was addressed in the part I of the paper, i.e. recipes of different proportions of materials were used to obtain ceramic bodies (seven raw mixtures). Shaped materials were fired in industrial tunnel kilns for biscuit/glost firing. Resulting ceramic bodies were tested for industry-relevant properties. Correlations composition-properties for the ceramic body were, initially, empirically identified, by observation. Regression analysis was used, afterwards, to scientifically quantify these correlations. Results confirm the existence of fair to up to strong correlations composition – properties; therefore, properties can be easily obtained by using the composition of the raw mix. In industry, these simple calculations can serve as a preliminary assessment of the properties, to reduce the amount of experimental efforts, given a set of raw materials. Multiple-Criteria Analysis was used to show that it is possible to select, on a scientifically basis, the best available alternative of the raw materials’ proportions used i.e. the alternative that fulfills most requirements, as concerning properties. In a future, second part of the paper, the correlation processing – properties will be explored to demonstrate the influence of grinding on the glaze properties.
Keywords
tableware ceramics, correlations, Multiple-Criteria Analysis
ADRIAN VOLCEANOV, RĂZVAN STATE, COSMIN MĂRCULESCU, ENIKÖ VOLCEANOV
Abstract
Pyrolysis and gasification as well as the product upgrading can be performed by conventional heating or microwave heating, the latter being preferred lately due to its advantages, such as fast heating and start-up or short processing time. The resulting products from gasification and pyrolysis have certain limitations and cannot be used for application in their current state. Pyrolysis and gasification are accompanied using catalysts to improve the yields or quality of reaction products.
The main goal of our research was to study the synthesis and structural characterization of ZSM-5 zeolite type catalysts, as well as to simulate their potential behavior in pyrolysis and gasification process of different vegetal waste.
As starting raw material has been used ZSM-5 zeolite that was subjected to protonation to obtain HZSM-5 form of zeolite. Then, substitution of H from protonated form with different transitional metals (Me = Ni, Mo, Co, Fe2+, Fe3+) was employed. The purpose was to establish the catalytic ability of Me-ZSM-5 substituted zeolite during pyrolysis.
To establish composition and structural-morphological characteristics of Me-ZSM-5 catalysts there were performed X-ray analysis and Fourier Transformed Infrared (FTIR) spectroscopy before and after pyrolysis process. The results have shown the preservation of structural features even after use, confirming their good stability after calcination at 6000C, the simulated temperature of pyrolysis. Morphological analyses have been done using Scanning Electron Microscopy (SEM) together with Energy Dispersive X-ray Analysis (EDAX) for elemental distribution and analysis.
The results were considered satisfactory and the first tests on both thermochemical and microwave assisted pyrolysis seem to be very promising.
Keywords
pyrolysis, catalyst, zeolite, synthesis ZSM-5
DOREL RADU, OVIDIU DUMITRESCU, IRINA PINCOVSCHI
Abstract
In the Na2O–Al2O3 system, six glasses were synthesized having the (35–x)Na2O·xAl2O3·65B2O3 molar composition, where x = 0; 5; 10; 12.5; 15; 17.5. For these synthesized glasses the following physical properties were measured: density; refractive index; linear thermal expansion coefficient; glass transition temperature. The structural compactness, the molar volume and the volume of oxygen ion, considered as structural characteristics for the first level of analysis (atomic), at a sub-nanometric scale, were also calculated. The correlation analysis of the properties indicated that these structural characteristics, even at this atomic level, sub-nanometric, influence the physical properties considered at a macroscopic scale. Moreover, the dependency graphs show a series of particular points (return points) that suggest structural transformation areas generated by the [BO3]-> [BO4] and [AlO6] -> [AlO4] transformations, according to the chemical composition of the glasses.
Keywords
Na2O–Al2O3 glasses, structural compactness, properties, correlations, sub-nanometric scale
TAHA H. ABOOD AL-SAADI , ZAINAB HASHIM MAHDI, ISAM TAREQ ABDULLAH
Abstract
Foamed geopolymer (inorganic polymers materials) were successfully produced from alkali activated glass waste powder, after thermally treated at temperatures between 500 and 700ºC for 1 hour. These geopolymers were synthesized by mixing the mixed color glass waste powder with (potassium hydroxide and sodium silicate) solutions. Thermal treatment of these new materials at temperatures ranging from 500ºC to 700ºC recorded an important volume increase 18-41%, during to a foaming process specific for sodium or potassium silicate (aluminate) hydrates. For these compositions and due to foaming process, the increase of volume is noticed at 600ºC and partial melting occurs at 700ºC. The formation of glass foams leading to large changes in volume associated with different sizes of open porosity. This method for creating a foaming geopolymers represents a novel reuse of the waste glass in engineering applications as thermal and sound insulations coupled with low cost and environmental benefits.
Keywords
glass waste, foamed geopolymers, alkali activators, thermal treatments
YIGITALP OKUMUS, GOKTUG GUNKAYA
Abstract
In this study, the aim is to synthesize borosilicate glass powder with a particle size of approximately 50nm by the sol-gel method to be used as a hierarchical surface agent in hydrophobic coatings. Precursors used in the sol-gel reaction are Tetraethoxysilane (TEOS) as a source of silicon, boric acid as a source of boron and potassium hydroxide as a source of alkali. For this purpose, process optimization was simply investigated in three stages; solution, catalysis and reaction temperature parameters, respectively. In the first stage of the study, gelling behavior and amorphous structure formation were examined by using solutions prepared with different solvents at different pH values. The solution, which had an ethyl alcohol-water mixture as a solvent with an acidic start and alkaline second step, was found to be suitable. In the second step, the effect of catalysis was investigated by changing the catalyst type and amount in the solution which was found to be most suitable in the previous stage. Ammonium hydroxide and urea solutions that contain ammonium groups were used as catalysts. It was observed that the urea solution did not function as a catalyst due to its neutral character versus the base character of the ammonium hydroxide. In the last step of the study, the effect of reaction temperature was investigated. Upper and lower temperatures are limited due to the solution-based process. A temperature close to room temperature was included in the experiment in order to increase the controllability of the temperature. The gelation behavior at all stages was recorded with photoshoots of tilted beakers, the amorphous structures were examined using x-ray diffractometer (XRD) and microstructures were visualized with scanning electron microscopy (SEM). As a result of all the steps, a solution mixture of ethyl alcohol with a water molar ratio of 44.6: 33.9 and a starting pH of 2.3, a catalyst solution of 0.102 mol of ammonium hydroxide and a reaction temperature 30°C, were determined as optimal parameters.
Keywords
Sol-gel, glass powder, catalysis
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
LIGIA TODAN, DOREL CRIŞAN, NICOLAE DRĂGAN, DANIELA C. CULIȚĂ, CRINU CIUCULESCU, SANDA MARIA DONCEA
Abstract
In this paper the adsorption of pyridine, a toxic pollutant, on naturally occurring clay, namely bentonite, was studied at a basic pH and room temperature. Sodium saturated bentonite as well as modified with a cationic surfactant were used and the results compared. The influence of contact time and of the initial pollutant concentration on the pyridine uptake was determined by GC-MS. The adsorbents were characterized before and after being in contact with the pyridine solution by BET specific surface area and porosity, XRD and FTIR analysis.
The hydroxyl groups of bentonite in contact with pyridine solution led to protonated pyridine forms which can be responsible for hydrogen bonds formation and electrostatic interactions with the clay and for surfactant removal. Chemical adsorption prevailed over the partition/physical adsorption in both cases and the process followed the pseudo-second-order kinetics with the Freundlich isotherm model representing well the equilibrium adsorption data. The equilibrium adsorptive efficiency was 82.88% for the surfactant modified bentonite and 97.82% for sodium bentonite, the latter being a better alternative for sequestering pyridine from solution.
Keywords
bentonite, infrared spectroscopy, X-ray diffraction, kinetics, pyridine adsoption
ZENO GHIZDĂVEȚ, ALINA CORNELIA BACIU, ANTON FICAI, DIANA ANCA TIT
Abstract
This second part of the paper aims to identify the influence of the mechanical processing of the raw mix on glaze properties.
Preliminary tests on grindability were run on each main raw material, showing an initial, large dispersion of the grains size distribution between raw materials at the lowest number of mill rotations. As the number of rotations increases, it was found that the mechanical behavior tends to link to the hardness of the raw materials. Specifically, grains size distributions fall into two different groups of very close, almost identical values: one group for the raw materials having a higher hardness (sand, feldspar) and the other for the lower hardness materials (dolomite and calcium carbonate).
Two sets of raw materials compositions, one for obtaining matte glaze and the other for obtaining glossy glaze were used; each of them was grinded in a laboratory, planetary ball mill at the same number of mill rotations (1000, 2000, 3000, 5000, 7000, 10000 and 13000 rotations) and grain size distributions were measured. The resulting raw mixes were used to glaze already-made ceramic biscuits. Glost firing was made in an industrial tunnel kiln at 1200°C and it was followed by the investigation of optical properties. Also, glaze thermal expansion was measured.
Results reveal that the particle size distribution of the raw mixtures strongly influence glaze color parameters and glaze thermal expansion. This shows a direct influence of the particles size on the investigated properties, as they interact with light. Specifically, as the grinding gets more advanced, the smallest crystals can enter the melt so lowering the number of crystalline particles existing in the glaze. On the other hand, smaller particles scatter the light more than bigger ones; consequently, they behave like opacifiers.
FTIR images of the glazes surface show that the glazes contain a considerable number of crystalline particles embedded in the vitreous matrix. FTIR spectra and maps revealed a decrease in transmittance as the fineness increases.
According to the results, there is no reason to increase the number of rotations higher than 7000 rotations.
Keywords
tableware ceramics, grinding, glaze, color