جستجوی مقالات مرتبط با کلیدواژه « additive » در نشریات گروه « فنی و مهندسی »

The polymer modified cementitious tile adhesives are very significant in construction sector. In order to considerably improve the bond qualities of the tile adhesive in polymer modified mortars, the proportions of constituent ingredients should be carefully selected. Consequently, to design high performance tile adhesives, interactions between all the components, such as the adhesion mechanisms between the polymers film and the substrate and the effect of various additives should be recognized. The effect of vinyl acetate ethylene (EVA), high alumina cement (HAC), and additives such as calcium formate and polycarboxylate on the adhesion qualities of ceramic tile adhesive was explored in this study. The findings indicated that these ingredients had an impact on the mortars' adhesive properties, and it is necessary to find their optimal amounts in order to achieve the maximum adherence. The results showed that the tensile strength of mortar was increased with increasing the polymer amounts. A microstructural analysis revealed that the polymer was distributed homogenously throughout the mortar.  The optimum amount of the used high alumina cement was determined 3 wt.%. Additionally, increasing the amount of accelerator and super plasticizer increased the tensile strength of ceramic tile adhesive by approximately 20-30%.

In this study, two inorganic additives with perovskite structure have been used as additives in fabrication of perovskite solar cells (PSCs). Ba2In2O5·(H2O)x and Ba2(In1.8Cr0.2)O5·(H2O)y was applied in perovskite precursor solution for synthesis of photo absorption layer in PCSs by a one-step solution method with solvent engineering technique. Cr-substituted and pristine Ba2In2O5·(H2O)x were prepared by solid-state and soft chemistry methods like the procedures in previous work, and utilized to improve the crystal structure and morphology of perovskite layer of PSCs. The morphology of the new perovskite layers was studied by FE-SEM, and XRD analysis. The results showed using 2 wt % of additives in precursor solution of fabricated PCSs increased the open-circuit voltage (Voc) of cells, also the power-conversion efficiency of the cells improved from 7.8 % to 9.7, and 9.3 % by using both additives respectively. Cr-substituted and pristine Ba2In2O5·(H2O)x could modify the coverage of perovskite film on the TiO2 layer and consequently improve the photovoltaic stability and performance of perovskite solar cells.

Based on various sources and experiences, the main phases of clinker have a significant impact on the technical characteristics of cement and its performance in the resulting concrete. The interaction of clinker phases with concrete admixtures is also obvious, but the effect of each of these phases and their optimal values for optimal concrete performance is complicate. Therefore, in this study, this issue was an extensive laboratory operation was designed. In the first phase, during three months, weekly sampling of two-kiln clinker of the cement factory was performed. Then, through 25 clinker samples taken, 11 samples were selected whose phase values were varied. During the second phase, laboratory cementation was performed under the same conditions using 11 clinker samples. A sample of high-consumption super plasticizer additive was also prepared. In the third phase, physical and chemical analysis of cement samples was performed. During the fourth phase, 22 concrete mixtures with 11 cement samples were prepared, so that 11 mixtures with the title of control (without additives) and 11 mixtures with the title of additives. Slump loss tests, air content, compressive strength of hardened concrete of 7, 28 and 90 days were performed on concrete mixtures and optical characteristics of fresh concrete mixtures were recorded for comparison. Based on the results, comparing the effect of C3S clinker on the compressive strength of standard mortar and concrete showed that there is no direct correlation between C3S and compressive strength (mortar and concrete), but it can be said that with each percentage increase of C3S clinker, about 1.5 unit (kg/cm2), 7 and 28 days strength of concrete increases. However, with the increase of C3S from about 57% onwards, the decrease in concrete strength is clearly seen, which can be referred to the negative effect of excessive C3S phase (due to the solubility of concrete and increasing the w/c ratio). Based on the results of air determination experiments of fresh concrete mixtures containing additives and its declining trend in this study, it was found that the optimal value of C3A is about 5-6%.

In this study, pure phase nanostructured strontium-doped lanthanum manganite, La0.75Sr0.25MnO3 (LSM), with a hexagonal structure was synthesized by sonochemical method. Then, XRD and SEM estimated the size of the LSM nanopowders. The results are exhibited that products synthesized in this method are compatible with particle size and morphology. Magnetic measurement was done by vibrating sample measurement (VSM) on LSM nanoparticles at room temperature. According to the results obtained from VSM displayed the saturation magnetization of LSM nanoparticles exhibited a maximum of 24.25 emu/g at room temperature. Then, the influence of LSM nanoparticle as an additive on the film morphology of CH3NH3PbI3 and the performance of perovskite solar cells was examined. We explore by using 5wt % of additive can increase the short current density (Jsc) from 14.45±0.55 to 18.29±0.38 mA/cm2 (~ 26.5 % enhancement) and power-conversion efficiency (PCE) from 8.33±0.40 to 12.41±0.35 (~ 49 % enhancement). Moreover, the morphology, and band gap of the new perovskite layer was improved.

In this study, we use metal-organic frameworks (MOFs), TMU-60 ([Zn (OBA)(L*). DMF]L*=5,6-di(pyridine-4-yl)-1,2,3,4 – tetrahydropyrazine) (compound I), and TMU-60-Cd (compound II), with excellent conductivity as additives in perovskite solution. The presence of cadmium in the structure of TMU-60-Cd can significantly enhance the conductivity of the framework. These frameworks can transfer the electron between the structures. Therefore, the use of these frameworks in perovskite solar cells could have a positive effect on electron transfer. However due to the creation of a lot of voids during the formation of perovskite layer, the power-conversion efficiency (PCE) of resulting PCSs were weaker than the pristine PCS. The results revealed that using even small amounts of TMU-60, and TMU-60-Cd caused a significant reduction in PCE, and the short current densities (Jsc), while improving the stability of the perovskite film, and the device. The absorption, and morphology of the new perovskite layer was also studied by UV–Vis spectroscopy, FE-SEM, and XRD.

Magnetic chitosan nanocomposites are one of the more recent advanced groups of adsorbents used to remove contaminants from waste water. In this research, N- Nicotinyl-N', N"-bis (Hexamethylenyl) phosphoric triamide (HE) was used as an additive to form a new nanocomposite with the structure of chitosan / 5% Fe3</sub>O4</sub> Nps/10% HE resulting in the highly efficient removal of Cd(II) ions from an aqueous solution. Several techniques were applied to characterize the new-fabricated nanocomposite: X-ray Powder Diffraction (XRD), Energy Dispersive X-ray Spectroscopy (EDX), Field Emission Scanning Electron Microscopy (FE-SEM), Fourier transform infrared (FTIR) and vibrating sample magnetometer (VSM). Atomic Absorption Spectroscopy (AAS) was used to measure the removal percentage of Cd(II) ions from the contaminated water samples. Results showed that 15 mg of the nanocomposite could remove Cd(II) ions with a rate of 99.9% from 20 mL of its 100 ppm aqueous solution in pH=9 with contact time of 1h. Furthermore, the same amount of the nanocomposite was applied to remove Cd(II) ions from 20 mL of a real wastewater sample with a pH=9 and the same contact time. The resulting removal rate of Cd(II) ions was 99.5%.