فهرست مطالب

  • Volume:4 Issue:1, 2019
  • تاریخ انتشار: 1398/01/20
  • تعداد عناوین: 7
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  • N. Amani *, E. Noferesty Pages 1-11

    Nowadays, in modern societies, growing activities in construction affairs and their economic development have been resulted construction wastes and so much demolition in the past three decades. Most of these wastes have not been treated and therefore caused severe damages to the environment. In this research, after reviewing construction and demolition management methods and their accessories, the selected method, which is proportional with Iran circumstances and can be used as a design technique for disassembly in waste management, is suggested according to the implemented interviews and questionnaires. In this proposed method, it has been attempted to cover all economic, environmental, technical and social aspects of waste management in Iran and eliminated defects in methods offered in other studies. The present methodology is somewhat a descriptive manner that shows the recommended idea using sketch-up software, interviews and questionnaires in order to confirm the execution capability of the project. Results showed that design for disassembly (DfD) technique in the field of ceramic floors, wall tiles and building facades is capable of decreasing environmental pollutions as a result of construction materials and can also increase economic advantages in construct and deconstruct stages until a sustainable construct compatible with the environment is achieved.

    Keywords: Waste management, Construction, demolition waste, Sustainable development, Design for Disassembly (DfD) technique, Ceramic materials
  • A. R. Rezaei, I. Mobasherpour *, M. M. Hadavi Pages 12-17

    Magnesium has been used in aviation industries, automobile manufacturing, electronics and medical engineering due to its unique properties thus far. The main problem in its utilization is the high reactivity of magnesium with oxygen and humidity, which both changes its properties. The surface charge and different density results in difficulties in dispersion stability of the powder in an organic medium. Therefore, numerous methods have been applied to improve the chemical resistance and surface modification of the powder particles. The ball milling process as well as immersion in Ethylene Glycol (EG) was used in this study to increase chemical resistance and micro-sized powder dispersion stability in an organic medium. The x-ray powder diffraction analysis was applied to analyze the phase constitutions formed on the powder surface. Scanning electron microscope (SEM) was also utilized to obtain the morphology and the particle size. Moreover, the simultaneous thermal analysis was executed for determining thermal resistance and reactions, which both were measured dispersion stability before and after ball milling process. Results showed a decrease in average particle size from 100 to 7 μm. The chemical resistances and the stabilization increased in organic solvents.

    Keywords: magnesium powder, ball milling, ethylene glycol, chemical resistance
  • Z. Balak *, M. Azizieh Pages 18-23

    The aim of this work is to optimize the oxidation resistance of ZrB2-SiC-based composites with different additives. Effect of nine factors including SiC, Cf, MoSi2, HfB2 and ZrC contents, milling time of Cf (M.t) and SPS parameters such as temperature, time and pressure on oxidation resistance in four levels was investigated. Taguchi design was applied to explore effective parameters for achieving the highest oxidation resistance. Spark plasma sintering (SPS) was used for sintering. Oxidation resistance tests were carried out on all composites using box furnace at 1600 °C for 1 hr holding time. Then Taguchi design was applied to determine effect of each factor on it. It has been concluded that ZrC by 45% has the most significant the effect on the oxidation resistance and oxidation resistance decreases by ZrC ascent while HfB2 has positive effect on oxidation resistance of ZrB2-based ceramics. Among the SPS parameters, the temperature has the most effect on microstructure and eventually oxidation resistance. Pressure by 2.3% and M.t by 3.4% have the least effect on the oxidation resistance. Other factors such as SiC, Cf, temperature, HfB2, MoSi2 and time have 12.8%, 8.3%, 7.7%, 6.2%, 5.9% and 5.6% on the oxidation resistance respectively.

    Keywords: Oxidation resistance, spark plasma sintering, ZrB2-SiC, carbides, borides, chopped carbon fiber
  • R. Khoshhal * Pages 24-31

    Ilmenite is a valuable industrial mineral containing Fe and Ti elements. Two composites with different morphology and composition were produced using the reaction of synthesized ilmenite and aluminum. The molar ratios of 1:2 and 1:8 were selected. The critical temperatures of each molar ratio were determined using the Differential Thermal Analysis (DTA). The heat treatment of the systems with different molar ratios was conducted at selected temperatures on the activated primary powders. It was specified that in the molar ratio of 1:2, at first, FeTiO3 reacts with aluminum, which leads to the formation of Fe, TiO2 and Al2O3. At higher temperatures, Fe reacts with TiO2 and so spherical Fe2Ti forms in the matrix of TiO2 and Al2O3. It should be noted that in the molar ratio of 1:8, FeAl3, TiAl3 and Al2O3 form through the reaction of FeTiO3 and aluminum, as a matter of fact, none of their products do not change at higher temperatures.

    Keywords: Ilmenite, Aluminum, Reaction sequence, Phase transformation, Molar ratio
  • H. Shokrvash *, A. Massoudi, R. Yazdani, rad Pages 32-39

    Immiscible metals due to their inherent specs are insoluble over the steady state. Developing an innovative approach to this issue would be fascinating and challenge the overriding rules. Herein, we proffer the principles of synthesis of Cu-Nb nanocomposites using electrochemical deoxidation route. This method consists of the cathodic electrolysis of the nanoparticles Cu-Nb2O5 through the molten salt electrolyte medium; which lead to the oxygen-free nanocomposites following the reduction of Nb2O5 and atomic translocation of Cu/Nb. Analysis of as-synthesized specimens by X-ray diffraction implies the Nb2O5 is reduced into Nb and all reflections of Cu are shifted to low-angles. Moreover, elemental analysis by energy dispersive spectrometry (EDS) illustrates the high solubility of Nb in Cu and Cu in Nb structure, which their crystallinity is consistent with the XRD. These findings confirm the electro-synthesis is a key technique for reduction of nanometer oxides, the substantial increase of solubility, and nano-alloying of immiscible metals.

    Keywords: Electro-deoxidation, Immiscible Metals, Oxide Precursor, Nanocomposites, Nano-alloy
  • L. Nikzad *, H. Majidian, S. Ghofrani, T. Ebadzadeh Pages 40-44

    A co-precipitation method was used for synthesis of pure MgTiO3 ceramic powder with Mg(NO3)2.6H2O, TiCl4 or C12H28O4Ti and NaOH as raw materials. In this method, solutions of 1 M, Mg (NO3)2 6H2O and 2 M, NaOH were prepared. A stoichiometric amount of Ti precursors from TiCl4 or C12H28O4Ti was weighted. Solutions of Mg (NO3)2. 6H2O and Ti precursor were added dropwise to NaOH solution under stirring.. The gelatinous white precipitate was calcinated at temperature range of 500-1000 °C. Moreover, the sintering process was performed at temperature range of 950-1350 °C. The results show that in the presence of TiCl4, pure MgTiO3 does not form, but using C12H28O4Ti, pure MgTiO3 with particle size less than 200 nm obtains at calcination temperature of 800 °C. Thus, the density of this sample is optimum (95% relative density) at a sintering temperature of 1050 °C and it has good dielectric properties including εr =16.2 and Q= 110000 GHz.

    Keywords: Magnesium titanate, co- precipitation, Microwave dielectric, sintering
  • F. S. Torknik *, G. M. Choi, A. Maghsoudipour, M. Keyanpour, Rad Pages 45-51

    With the aim of promoting the Ni/Ce0.8Gd0.2O2-δ (Ni/GDC20) cermet anodic performance of low temperature solid oxide fuel cell (LT-SOFC) [1], nanostructuring platinum nanoparticles on NiO/GDC composite was done by single-step wet-infiltration of hexachloroplatinic acid hexahydrate (H2PtCl6.6H2O) precursor on NiO/GDC20 composite. The anodic polarization resistance was measured using symmetric Ni–GDC20|GDC20|Pt electrolyte-supported cell at a temperature range of 400 to 600 °C. Microstructural refinement was studied by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) techniques in comparison to the bare anode before and after hydrogen reduction at 600 °C and also after anodic performance test. Nanostructuring Pt-nanoparticles with an average particle size of 12.5 nm on Ni/GDC20 anode indicated the lack of electrocatalytic enhancement with the addition of platinum for H2 oxidation reaction in LT-SOFC.

    Keywords: LTSOFC, Ni-GDC20 Anode, Platinum Infiltration, Pt-Nanoparticles, H2PtCl6.6H2O