română D. RENTERÍA-ZAMARRÓN , J. A. DÍAZ-GUILLÉN, D. A. CORTÉS-HERNÁNDEZ, S. M. MONTEMAYOR, C. M. LÓPEZ–BADILLO, J.C. DÍAZ-GUILLÉN , A. F. FUENTES
Abstract
A biomimetic method was used to improve bioactivity of Sr2SiO4. Strontium silicate was obtained by using a combination of techniques such as mechanical activation and reactive sintering, of a powder mixture of strontium carbonate and silicon dioxide. Single phase Sr2SiO4 was obtained after 6 h of mechanical milling of the starting reagents, followed by a uniaxial pressing and a thermal treatment in air at 1200 °C for 6 h. For the biomimetic treatment, samples were immersed in a simulated body fluid (SBF) for 7, 14 and 21 days on a bed of wollastonite powder and were characterized by SEM, EDS, XRD, FT-IR and TEM. For comparison purposes, experiments were also performed without using the bioactive powder bed. Results showed that a bone-like apatite layer was formed on strontium silicate after 21 days of immersion in SBF without a bed of wollastonite and slight layer of Ca, P-rich compound, using a bed of wollastonite powder, corroborating the viability of these oxides to be used as bioactive materials.
Keywords
Strontium silicate, Biomimetic method, Wollastonite, Mechanical activation, Reactive sintering
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Year
2020
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Issue
50 (1)
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Pages
10-16
E. H. SUJIONO, M. Y. DAHLAN, A. C. M. SAID, R. A. IMRAN, S. SAMNUR
Abstract
The crystal structure of Nd1.2FeO3 oxide material synthesized by varying calcination temperatures was determined using the X-ray diffraction method. Further analysis by Rietveld refinement using software Rietica showed that all of the samples have an orthorhombic phase structure. The lattice constants of each a sample with variation of calcination temperature is a = 5.581059 ± 0.000736 Å, b = 7.758627 ± 0.000947 Å, c = 5.448341 ± 0.000665 Å; a = 5.580203 ± 0.000695 Å, b = 7.756789 ± 0.000908 Å, c = 5.447646 ± 0.000626 Å; and a = 5.580402 ± 0.000704 Å, b = 7.758957 ± 0.000919 Å, c = 5.449350 ± 0.000634 Å, respectively. The results of lattice constant were associated with the value of Goodness of Fit (GoF) is 0.9101%, 0.8726%, and 0.9303%, respectively. That has a strong indication of a qualified matching between the NdFeO3 model numbers of COD 2003124 with the current experimental results. The value of FWHM and the crystal size of Nd1.2FeO3 samples are 0.22º and 372 nm. The results showed that the variation of calcination temperature has not a significant change in the crystal size and homogeneity of the atomic crystal structure. These results are confirmed by simulation of the atomic structure using the Diamond software, the dominant peak of hkl (121).
Keywords
X-ray diffraction; FWHM; Nd1.2FeO3; Rietveld refinement; Crystal Structure; Morphology
CRISTINA ILEANA COVALIU, IULIANA PĂUN, EUGENIU VASILE
Abstract
The paper presents the adsorption capacity of magnetite nanomaterial for a cationic surfactant removal from wastewater. Kinetic studies were performed by adding the magnetite nanomaterial to a wastewater solution of benzethonium chloride having the concentrations of 2 mg/L and 20 mg/L. The wastewater systems were investigated at 1, 2, 4, 6, 24 and 48 h. The highest removal efficiency (86,98%) was obtained for wastewater containing 2 mg/L benzethonium chloride concentration. The results obtained for the magnetite nanomaterial demonstrates the possibility of applying this nanomaterial for the removal of benzethonium chloride cationic surfactant from wastewater.
Keywords
magnetite nanomaterial, adsorbent, cationic surfactant, waste water
LĂCRĂMIOARA-RALUCA BIVOL, VALERIU-GABRIEL GHICA, EUGENIU VASILE, CRISTINA ILEANA COVALIU, DAN GHEORGHE, MIRCEA-IONUŢ PETRESCU, GHEORGHE IACOB, MIHAI BUZATU
Abstract
The work analyzes an artwork painted on a metal plate as a substrate in order to establish its authenticity. In the lower-right side is to be noticed a signature alongside a date (‘’Lecca 1866‘’), whilst on the reverse, in the upper-central part, there is another signature under which there is an inscription in Greek language (‘’Ο ΑΓΙΟΣ ΑΝΤΩΝΙΟΣ (phonetictranscription AGIOS ANTONIOS) 1866‘’. The signatures, dates and the inscription on the front and reverse sides of the paintings were added long after the original painting was carried out. The outcome is showing the work was repainted almost entirely on tin-plated iron sheet. The work includes a brief study on the work and activity of painter C. Lecca. The history of the use of metal supports in easel painting is also investigated. A complex metallographic analysis was performed on the metal support (i.e. optical microscopy and SEM-EDX). X-ray fluorescence spectrometry (XRF) analyzes were carried on the paint layer.
Keywords
metal support, iron sheet, SEM - EDX, XRF
VALERIU-GABRIEL GHICA, EUGENIU VASILE , COSMINA CARATA, CRISTINA ILEANA COVALIU MIRCEA-IONUŢ PETRESCU, GHEORGHE IACOB, MIHAI BUZATU
Abstract
In the present work, button cell batteries with silver content were sectioned, introduced in an ultrasonic bath in an acidic medium (acetic acid) and the resulting paste, after washing and filtration, was analyzed to identify the constituent elements in order to establish the silver recovery technology. The samples were analyzed by Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDXS). X-ray Diffraction Data (XRD) data were obtained using a Panalytical X’PERT MPD X‐ray diffractometer. The operation of separating the paste with silver content from the steel case was carried out using an ultrasonic cleaning process in an acid environment. Half-sectioned faucets were placed in an Emmi12-HC ultrasonic cleaning bath; chlorinated water and acetic acid (CH3COOH) 0.5 M were used as the cavitating medium (solvent). The process took place at room temperature, no heating source being required. Analysis carried out on the recovered slurry with X-ray diffractometer revealed the presence of silver (as Ag and AgCl) and manganese (as Mn2O3). Zinc was completely dissolved in the solution. The silver chloride obtained can be processed metallurgical in order to recover the silver (cementation with zinc and then the silver is subjected to electrolytic refining).
Keywords
spent button cells, silver - oxide, recovery, SEM - EDXS, XRD
A.SOBEȚKII, M. T. OLARU, U. CINDEMIR, L.ÖSTERLUND, A. STĂNOIU, C.E SIMION, S.E. BEJAN, R.E. IRIMESCU
Abstract
Thin nanostructured films are the state-of-the-art materials for detection of very low limits of toxic gases. The work presents a comparison between the properties of WO3 thin films obtained by two different deposition techniques: Advanced Gas Deposition (AGD) and DC Reactive Sputtering. Films have been characterized by XRD, SEM and XPS. WO3-based sensors have selective sensitivity in H2S detection at operating temperature of 200°C and relative humidity specific to field applications. The potential interferences with CO2, SO2 and NH3 are negligible, highlighting the application potential of WO3.
Keywords
Gas sensing, Tungsten trioxide, Advanced Gas Deposition, DC Reactive Sputtering
ADRIAN VOLCEANOV, RĂZVAN STATE, COSMIN MĂRCULESCU, ENIKÖ VOLCEANOV
Abstract
For present time, declining petroleum resources, accompanied by an increasing demand for oil and chemicals by emerging economies, as well as environmental and political concerns about fossil fuels, it has become essential to develop energy-efficient processes for the sustainable production of fuels and chemicals using alternative resources. In this respect, biomass (including vegetal waste from different industries and agriculture) is considered the renewable energy source with the highest potential regarding energy needs of modern society, for both the developed and developing economies. It represents a sustainable source of organic carbon and biofuels, which generate significantly fewer greenhouse gas emissions than fossil fuels, and can even be neutral in CO2 production balance, when efficient methods are developed.
Regarding the technologies for vegetable biomass valorization, fast pyrolysis is one of the most viable perspectives, if the quality of the products (gas, liquid and char) is improved.
Pyrolysis and gasification as well as the product upgrading can be performed by conventional heating or microwave heating. Both processes require the use of catalysts to improve the yields or quality of reaction products. The purpose of present paper was to establish the catalytic ability of montmorillonite (MMT) after doping with different transitional metals (Me = Ni, Mo, Co, Fe2+, Fe3+), following a procedure developed in a previous paper [1].
There were performed X-ray diffraction analysis and Fourier Transformed Infrared (FTIR) spectroscopy before and after pyrolysis process upon the Me-MM catalysts to verify composition and to establish their structural and morphological characteristics. Morphological characteristics were determined by Scanning Electron Microscopy (SEM) together with Energy Dispersive X-ray Analysis (EDAX) for elemental distribution and analysis.
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 and were considered satisfactory and the initial tests on both thermochemical and microwave assisted pyrolysis seem to be promising.
Keywords
pyrolysis, catalyst, synthesis, characterization doped montmorillonite
BERK UYSAL, SELEN ȘEN, AYBEN TOP
Abstract
In this study, ZnO samples were synthesized using zinc acetate and urea with a method containing sonication, sol-gel transition and calcination steps. Urea to zinc acetate mole ratio values were changed as 0, 0.5, 1, and 2 and corresponding calcined samples were denoted as UZ-0, UZ-0.5, UZ-1, and UZ-2, respectively. Scanning electron microscopy (SEM) images indicated globular and rod-like structures. Aspect ratios of the nanorods increased as urea to zinc acetate ratio increased from 0 to 1 whereas nanoparticles with sizes of 70 ± 20 nm were observed for UZ-2 sample. Brunauer, Emmett and Teller (BET) surface area values of the samples varied between 9 and 25 m2/g and increased as initial urea amount increased. Band gap energies of the samples ranged between 3.24 and 3.29 eV. Four major peaks at about 400, 420, 480 and 530 nm with different intensities were observed in the photoluminescence (PL) spectra of the samples. All the samples removed rhodamine B by both adsorption and photodegradation. The highest visible light induced photodegradation rate was exhibited by UZ-2 sample having the highest surface area and it is attributed to superior charge separation properties of this sample under visible light.
Keywords
ZnO, nanostructures, optical properties, photocatalyst, N-doping
DANUTĖ VAIČIUKYNIENĖ, LEONAS JAKEVIČIUSB, ARAS KANTAUTASC, VITOLDAS VAITKEVIČIUS, VILIMANTAS VAIČIUKYNAS
Abstract
To explain some aspects about the mechanism of zeolite synthesis from reagent materials, law temperature (100oC) hydrothermal reaction was performed in alkali solutions by using sonochemically-assisted pre-treatment method. This pre-treatment method reduces the formation times of zeolites. Clear-to-the-eye sodium aluminosilicate gels and solid sodium aluminosilicate mixtures were used as raw materials. By using sodium aluminosilicate gels, it is observed that after hydrothermal treatment and sonication up to 10 minutes samples exhibit a rise in the crystallinity of Na-A zeolite up to 1.44 times, compared to a sample without sonication. When solid components as raw materials were used, the application of ultrasound irradiation and hydrothermal treatment resulted in the replacement of Na-A zeolite crystals to Na-X zeolite, which is a more stable zeolitic phase. In both cases Na-A zeolite was not detected in the synthesized products by using only sonication without the using of hydrothermal treatment. It was observed that the Na-A zeolite crystallization level is higher for samples which were obtained from the raw material of aluminosilicate gel.
Keywords
Na-A zeolite synthesis; sonication; hydrothermal synthesis
I. GOMOIU, R. RADVAN, L.GHERVASE, I. MOHANU, M. ENACHE, S. NEAGU, R.RUGINESCU, R. COJOC
Abstract
Both this paper and the identitification of the proper methods for cleaning of mural paintins and mortars (either originals or for restoration) have the great significance that aims scientific conservation and restoration of historical monuments. The review analyses both the main methods curently used for clening, pointing their efficiency in restoration activity, bioclening and case studies. Mechanical, physical, chemical and biological methods are used in the cleaning activity. The mechanical methods are based on the use of soft brushes and the physical ones on the use of the laser. For chemical cleaning, organic solvents, microemulions and gels are applied on the pictorial layer and mortars.
The findings show that biocleaning based on bacterial metabolic products perform better in this field. Green and nondestructive methodology for biocleaning of aged materials and deposits on murals based on products that contain gels with immobilized enzymes, active on salted surfaces is proposed. The new green technology based on metabolites (hydrolases and polysaccharides) obtained from non-pathogenic microorganisms grown under controlled conditions will be developed in the frame of the project “Murals biocleaning by new innovative green products based on microbial metabolites”.
The case studies are regarding to: in situ biocleaning of mural paintings, of the murals restored with resins, of the extracted murals, bioremoving of sulphates, nitrates and graffiti.
Keywords
cleaning, biocleaning, mural paintings, green methodologies, case studies
ILEANA MOHANU, ROXANA FECHET, IONELA PETRE, NICOLETA CÎRSTEA, DAN MOHANU, IOANA GOMOIU
Abstract
Applied more than a decade ago, within an interdisciplinary project carried out at the cave church from Corbii de Piatră (14th century), Argeș County, the conservation-restoration materials created by CEPROCIM were intended for a future intervention to consolidate the support of the murals inside a unique medieval monument of exceptional value. Monitoring the behavior of new materials applied in situ was required in the case of a monument characterized by a severe microclimate, with considerable variations in temperature and humidity, caused by the condensation and infiltration, generating a large process of biodeterioration. The observations made in situ were corroborated with laboratory analyzes, using specific investigation techniques: X-ray diffraction, scanning electron microscopy coupled with X-ray dispersive energy and optical microscopy. In the absence of measures to improve microclimate conditions and the continues degradation processes (crystallization of salts, biological contamination) was found to maintain the functional qualities of new materials applied in situ.
Keywords
microclimate monitoring, restoration material, rupestral church, degradations
CRISTINA ANDREEA VÎJAN, ALINA BĂDĂNOIU, ADRIAN IONUȚ NICOARĂ, IULIA BARCAN
Abstract
This paper presents the influence of oxide component (magnesia or calcined dolomite) on the setting time and compressive strengths of phosphate cements in which the phosphate precursor was sodium dihydrogen phosphate. These cements were used for the immobilization of two simulated wastes with Ni or Pb content. The presence of Ni or Pb in these cements determines a decrease of the early compressive strengths (after 1 day of hardening). The leaching test (SR EN 12457-4) performed on the cements with waste content hardened for 28 days shows the immobilization of these two heavy-metals in both types of phosphate cements (based on magnesia or calcined dolomite); nevertheless, for the phosphate cements based on calcined dolomite (with/without Ni or Pb waste) an important strength loss is recorded at longer periods of time (28 days, 1 year) most probably due to the delayed CaO hydration with volume expansion. X ray diffraction was used to identify the crystalline compounds formed in hydrated cements and Scanning Electron Microscopy (SEM) coupled with EDS (Energy Dispersive Spectroscopy) to assess the microstructure and elemental composition of identified phases.
Keywords
magnesia, calcined dolomite, sodium phosphate, nickel, lead, waste