română ANGELA SPOIALĂ, CORNELIA-IOANA ILIE, GEORGIANA DOLETE, ROXANA-DOINA TRUȘCĂ, LUDMILA MOTELICĂ, OVIDIU-CRISTIAN OPREA, DENISA FICAI, ANTON FICAI, ECATERINA ANDRONESCU, LIA-MARA DIȚU
Abstract
The purpose of this article was to synthesize antimicrobial composite membranes using chitosan (CS) and zinc oxide (ZnO) nanoparticles as adsorbents for the removal of heavy metals. Chitosan/ ZnO composite membranes were prepared through the electrospinning method. The ZnO nanoparticles concentration from the CS/ZnO composite membranes was 1% and respectively, 5%. The synthesized membranes were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential thermal analysis (DTA), hydration capacity, antimicrobial assessments and, heavy metal retention through the inductively coupled plasma mass spectrometry (ICP-MS) analysis technique. The thickness of the as-prepared CS/ZnO composite membranes was 20µm (CS/ZnO 1%) and 30µm (CS/ZnO 5%). The appearance of the synthesized membranes indicated a smooth and uniform morphology, which suggested the integration of zinc oxide nanoparticles into the obtained membrane. Fourier transform infrared spectroscopic measurements showed the existence of relevant functional groups of both chitosan and ZnO in the composite membranes. ICP-MS measurements provided information regarding the capacity of retention of these membranes, indicating that CS/ZnO 5% had the highest retention rate. The as-obtained CS/ZnO composite membranes are expected to be used as adsorbent materials for water purification applications.
Keywords
ZnO; chitosan; nanocomposite membranes; antimicrobial; water purification
CRISTIAN PETCU, VASILICA VASILE
Abstract
The construction industry uses an ever-increasing amount of thermal insulation materials to meet the building sectors growing energy efficiency demands. Exclusive use of synthetic thermal insulation may lead to a complicated process of re-integrate demolition waste in the economy and potential environmental damage over time. The use of traditional natural materials is ecological and through an appropriate design of the buildings, it offers efficient construction elements. This paper attempts to increase the professionals awareness of some typical industry by-products (straw, sawdust, cellulose), with thermophysical characteristics interesting for the building sector. Besides the information needed for the usual engineering calculation, like thermal conductivity coefficient, we measured data needed for dynamic building simulation, such as thermal diffusivity, volumetric heat capacity, and specific heat capacity.
Keywords
thermal insulation; by-products; sustainability; building materials; sustainable buildings
ALI SABERI VARZANEH, MAHMOOD NADERI
Abstract
Curing and compaction are two major factors in the interface bond strength of concrete and repair mortars. Ignoring these two factors would create fine holes in the concrete-mortar interface and reduce the adhesion. Hence, the present study has aimed to evaluate the effects of initial pressure and fiber on adhesion between mortars and concrete substrates using the twist-off and pull-off tests. The effects of fibers on the shrinkage of mortars are also discussed. The influences of pre-pressure and fibers on the adhesion of the two layers were demonstrated using the scanning electron microscopy (SEM) and X-ray diffraction (XRD) methods. The results indicated that initial pressure had positive impacts on the interface shear and tensile bond strength in the twist-off and pull-off tests, and the effect of pre-pressure was greater on mortars with more aggregates. Moreover, fibers reduced the mortar shrinkage and increased the adhesion. Considering the high correlation between the twist-off and pull-off results, affordable and available twist-off apparatus can be employed instead of expensive pull-off apparatus to measure the concrete-mortar adhesion.
Keywords
Twist-off, Pull-off, Pre-pressure, Bond, Fiber
SUMATHI A, ELAVARASI D , SARAVANA RAJA MOHAN K
Abstract
The current research was carried out on the effect of natural sand replaced by manufactured sand (M-sand) in fibrous concrete infiltrated with slurry under static and impact loading. The compressive strength, split tensile strength and impact strength of Slurry infiltrated fibrous concrete (SIFCON) with partial replacement of river sand by M-sand. Hooked end steel fibres of 10% by volume fraction and a constant slurry mix of 1:1 with water cement ratio of 0.4 were used. The low velocity impact response is conducted on 150 mm and 60 mm high cylindrical specimen diameters using the drop weight impact test device as per ACI Committee 544-89. By dropping a steel ball of 4.5 kg with a falling height of 457 mm with the use of a self-manufactured drop-hammer impact test setup, the replication of a low-velocity impact on the cylinder was achieved. The test results show that the strength and energy absorption capacity of SIFCON with 50% of natural sand substituted by M-sand significantly improved compared to all other replacement of M-sand. It was found that optimum replacement level of river sand by M-sand as 50%. Regression analysis has been developed from the experimental results to predict the first crack and ultimate energy absorption capacity of SIFCON. The analytical values from the regression model are well correlated with the experimental results.
Keywords
CUVINTE CHEIE (ENGLEZĂ)
VIRGIL PENTA, CAMELIA UNGUREANU, ANDREI BOGDAN STOIAN, CRISTIAN PIRVU
Abstract
Candida albicans is the most frequently isolated pathogen yeast and is present in the oral cavity of almost half of the population. Since there have been several seemingly contradictory studies on the effect of electricity on C. albicans behavior, we propose a new method of measurement: Electrochemical Impedance Spectroscopy (EIS) coupled with Surface Plasmon Resonance (SPR). Along with other electrochemical methods and high-resolution Atomic Force Microscopy (AFM) imagery we investigated the effect of electric potentials measured between metallic intraoral restorations materials on C. albicans.
Keywords
Candida albicans, biofilm, Surface Plasmon Resonance, Electrochemical Impedance Spectroscopy, Atomic Force Microscopy
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Year
2022
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Issue
52 (2)
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Pages
145-155
ANDRADA-ELENA ALECU, ȘTEFANIA-ANDREEA GIRJOABA, MIHAELA BEREGOI, SORIN-ION JINGA, CRISTINA BUSUIOC
Abstract
In this work, polyvinylidene fluoride was obtained in the form of one-dimensional structures with the help of electrospinning technique. Several types of precursor solutions were tested to find the optimal experimental conditions to produce smooth, continuous and beadless fibres, morphologically suitable for the development of piezoelectric scaffolds dedicated to tissue engineering applications. Thus, the influence of solvent type, polymer concentration, as well as electrospinning parameters (feeding rate, spinneret-collector distance, and applied voltage) was assessed and the best situation was the one with a 2:3 ratio between dimethylformamide and acetone, 20 % polymer concentration, 1 mL/h flow, 20 cm distance and 18 kV voltage. In the end, the fibres were loaded with barium titanate commercial particles, as first attempt to produce a piezoelectric composite with potential in the medical field.
Keywords
polyvinylidene fluoride, barium titanate, fibres, electrospinning, morphology
SEYED VAHID RAZAVI TOSEE , IMAN FARIDMEHR
Abstract
In this research, from zero to 100% every 10%, normal aggregates were replaced with heavy aggregate (a mixture of iron ore and barite) in the concrete. A total of 110 cylindrical specimens (15x30cm) and cubic specimens (15x15cm) were used to examine the specific gravity, compressive strength, and tensile strength of Heavyweight Concrete (HWC). The test results confirmed that by substituting Heavyweight Aggregate (HWA) iron ore and barite mixture for 10% (or higher) of regular aggregates, a specific weight greater than 2600 kg/m3 might achieve, and the resulting product classified as HWC. In the second phase of the research, to develop the Generalized Regression Neural Network (GRNN) for estimating compressive and tensile strength, 48 data records from the specimen tests were selected randomly to find the best network with minimum mean square error (MSE) and correlation coefficient. The results confirmed that the proposed informational model could adequately estimate the mechanical properties and simplify the design processes in computational intelligence structural design platforms in the future.
Keywords
Material Science, Material Property, Material Structure
HARIDASA ANAYAK, N KRISHNAMURTHY, SHAILESH RAO A
Abstract
In recent years, the coating of different materials inside the cylinder liner has emerged as a prime focus of research among the scientists as it improves the efficiency of the engine. In this paper, the coating material, YSZ + Al2O3 with equal proportion were coated on the cast iron substrate using two bonding materials (Iron Nickel Aluminium composite powder (Metco 452) and Nickel Aluminium cermet (Metco 410 NS)) with the three-coating thickness of 100µm, 200µm and 300µm. Initially, the wear characteristics were carried out and properties like the coefficient of friction (CoF), wear rate for different load conditions were determined. The analyses of the worn sample were studied in details with the aid of SEM images. Further, the scratch studies for the worn samples were also carried out.
Keywords
plasma spraying, wear, microhardness, coating thickness, the coefficient of friction
MD INSIAT ISLAM RABBY , SITI UJILA MASURI, N.M.S. HASSAN, SK MAHAFUJUR RAHMAN, TAZEEN AFRIN MUMU, MAHFUZ ALAM
Abstract
A triangular corrugated pipe was studied numerically along with Al2O3-water, CuO-water, and SiC-water nanofluids, to identify the thermal capacity for laminar flow. Ansys fluent software and steady-state control volume method were applied for simulation purposes. Hence, different volume fractions (1% - 5%) of CuO, Al2O3, and SiC nanoparticles were considered to mix with water to suspend nanofluids. 400 to 1200 Reynolds number with a constant wall heat flux of 1000 W/m2 were considered to calculate the heat transfer rate. In addition, the required pumping power for such enhancements was determined as well. The simulation results highlighted that corrugated pipe provided highest improvement in heat transfer with increase in Reynolds number compared to straight pipe. Consequently, the mixing of nanoparticles in the working fluid showed more enhancement. For the corrugated pipe, at Re =1200, CuO-water, Al2O3-water, and SiC-water nanofluids showed a maximum 11.94%, 8.96%, and 9.15% enhancement respectively of Nusselt number compared to water. Furthermore, CuO-water, Al2O3-water, and SiC-water nanofluids showed enhancement in pumping power compared to water. Additionally, a correlation to predict the Nusselt number for nanofluid and triangular corrugated pipe was also developed by using Buckingham π Theorem, which showed good agreement with numerical results. However, it can be concluded that corrugated pipe, along with nanofluids, provide enhancement in heat transfer for the laminar developed region of a pipe.
Keywords
Nusselt number; nanofluids, volume concentration, Buckingham π Theorem, pumping power
SATISHKUMAR SENGOTTAIYAN, SURESH PARAMASIVAM
Abstract
The health risks connected with the use of asbestos-based brake linings have sparked research into the use of environmentally benign agro-based biomaterials as reinforcing agents in composite materials used in the manufacturing of brake pad linings. The purpose of this research is to determine the feasibility of employing coconut shell (CS) powder in the manufacturing of asbestos-free brake lining materials. The powders, in conjunction with the appropriate fillers, were utilised in the manufacture of the brake lining. The compositions of the reinforcing powders were varied between 20% and 35%, those of the resin binder were varied between 58 and 43%, and those of the filler metal and curing agents were maintained constant. Weighed, prepared, mixed, cured, and moulded these materials. Water and oil absorption, compressive strength, hardness, and wear tests were performed on the created composite materials. The research indicated that increasing the amount of reinforcing elements leads in an increase in the samples water and oil absorption. Compressive strength of the composite rose proportionately with the addition of up to 35% composition. The coefficient of friction tested was determined to be within an acceptable range. Additionally, when combined with other fillers and confined, CS powder shown great potential for brake lining manufacturing.
Keywords
Coconut shell (CS), Brake linings, Compressive strength, Hardness, wear
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Year
2022
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Issue
52 (4)
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Pages
368-373