To reveal the prior-austenite grain boundaries in micro-alloyed steels there is different techniques. This study has been carried out over a wide range of temperature (950-1150 οC) and it has been found that the tested procedure based on the combination of heat treatment and thermal etching (TE) method give excellent results for the Titanium and Titanium free medium carbon micro-alloyed steels at all the austenitization conditions tested.

The naphtha cracking process experiences problems such as fouling in the cracked gas compressor, and the accumulation of coke on the furnace coils, which require the use of exhaustive energy resources and costs to maintain the process. Several attempts have been carried out to solve this process in ethylene plants, but reducing fouling and energy costs during naphtha cracking remains a challenge. This study involves a simulation experiment that covers the addition of steam and carbon dioxide to the naphtha cracking process based on realworld data extracted from an ethylene plant in Libya, in order to investigate the effects of the addition of CO2 towards mitigating fouling in the cracked gas compressor, as well as coke accumulation on the coils inside the furnace, and in turn the energy resources and costs involved in the process. The key role of the addition of steam is the fractional elimination of the accumulated coke that leads to various issues within the reactor, such as the low heat transfer and the decrease in pressure. In this study, the diluting media CO2 is employed along with steam in order to investigate its effect on operating conditions and the main products’ yields. Two simulation models were constructed to investigate the thermal cracking process of ethylene in the existence of CO2 and steam. The first model involved only steam, and represented the standard design. The second model involved the addition of both CO2 and steam. After evaluation and comparison of both models, promising results reveal that the addition of CO2 and steam during the naphtha cracking process mitigate costs and energy resources required to …

Because of their persistency and toxicity, dyes and heavy metal ions discharged to water bodies have become a worrisome issue. Therefore, to secure the innate beauty of our planet and to conserve our non-renewable natural resources, specifically, water, it is essential to check and/or to minimize heavy metal ion and dye concentrations before discharge. Adsorption is considered as a robust and widely acclaimed water decontamination technology. In material science research, much attention has been focused on graphene, a carbon allotrope with a two-dimensional sheet-like structure possessing unique structural properties that has been utilized in various research areas. Herein, we present recent developments, specifically focusing on the use of graphene and its derivatives as an adsorbent for dye and heavy metal ion removal from aqueous phase. A historical overview, synthesis methodologies, structural …

This study aimed to investigate how safranin-O can be removed from aqueous solutions by adsorption on pineapple peels. The effect of solution pH, initial dye concentration, contact time and adsorbent dose were studied. The optimum adsorption capacity of 26.08 mg/g was achieved under the experimental condition of pH, temperature and contact time of 6, 293K and 80 min, respectively. Also further analysis revealed that 93.24% of safranin-O was significantly removed at 120 mg/L dye concentration in 80 minutes contact time. From the result of the isotherm studies, it was revealed that the equilibrium data is well fitted to Freundlich model while the adsorption kinetic data showed that the adsorption process was well described by the pseudo-second order kinetic model. Finally, it can be deduced that pineapple peels had a great potential in adsorbing and removal of safranin-o from aqueous solution. 

In this present work, crystalline growth conditions of oriented carbon nanotubes based on chemical vapor deposition (CVD) were optimized. The crystallinity and degree of alignment of the grown carbon nanotubes (CNTs) were characterized by field emission scanning electron microscopy, transmission electron microscopy, and Raman spectroscopy. The effects of four variables, namely, deposition time, deposition temperature, annealing process, and concentration of the precursor on the crystallinity of the CNTs, were explored. Furthermore, the correlation of parameters with the growth mechanism was examined using response surface methodology in an attempt to determine the complex interactions between the variables. A total of 30 runs, including predicting and consolidation runs to confirm the results, were required for screening the effect of the parameters on the growth of the CNTs. On the basis of the investigated model, it was found that the crystallinity of the CNTs grown by the CVD method can be controlled via restriction of the effective parameters.

In this work, the estimation capacity of the response surface methodology (RSM), in the catalytic naphtha reforming to enhance the octane number of reformats via isomerization reaction pathway and minimize the aromatization activity over tri-metallic modified Pt-Re/Al2O3 catalyst were investigated by applying Design of experiment (DOE). The parent bimetallic catalysts were modified using a relatively inactive metal (Sn) by means of employing non-conventional method of anchoring technique called controlled surface reaction (CSR) method in order to favor the intimate contact of Sn with the active phase to suppress the metallic character of Pt metal. The correlations between RON, aromatization and isomerization activities with three reaction variables namely temperature (480-510oC), pressure (10-30 bar) and space velocity LHSV (1.2-1.8 h-1) were presented as empirical mathematical models via reforming of a complex mixture (80oC -185oC). Numerical results indicated that the minimum aromatization activity was 20% when reaction temperature was 460oC and pressure of 35 bar. Results also show that maximum isomerization activity of 58% was achieved when pressure is 30 bar and space velocity is 1.8 h. it has been found that optimum value of RON = 89 was attained at 449.9oC, 32 bar and 1.7 h-1. However, high operating pressure and low reaction temperature significantly decrease the aromatization activity coupled with substantial decrease in RON which can be enhanced by producing high yield of isomers.  

The effect of a relatively inactive metal on the texture properties and catalytic performance of bi-metallic platinum–rhenium (Pt–Re)–S/Al2O3–Cl catalyst was investigated. The concentration of introduced tin (Sn) varied between 0.06 and 0.32 % (weight basis). The parent and modified catalysts were characterized using the following techniques; BET, X-ray diffraction, SEM–EDX, and atomic absorption spectroscopy/inductively coupled plasma spectroscopy. The bi-metallic and tri-metallic catalysts were also screened for their activity and selectivity in the reforming of n-octane under the following conditions: T = 480 °C, p = 10 bar, WHSV = 3.3 h⁻¹ and H2:HC = 4.5. Results showed that, on n-octane conversion, selectivity have changed favorably i.e., low selectivity to aromatics but high selectivity to iso-paraffins and olefins. In addition, less cracking products were detected and high liquid yields (LYs) were obtained. However, there is a strong and closely linear correlation between aromatics and octane number. The results of this work showed that catalyst with Sn >0.14 and <0.32 performed the best catalyst i.e., no major effect on research octane number, LY and selectivity with the addition of more Sn.

This work is focused on nucleation stages during isothermal austenite transformation in two types of Vanadium micro-alloyed steels. Isothermal treatment was carried out in the temperature range 350 to 600οC. Metallographic evaluation using optical and scanning electron microscopy (SEM) enabled determination of the nucleation curves of isothermally decomposed austenite. Three curves are found to be relevant to this initiation stage of transformation: first curve is related to grain boundary nucleated ferrite (GBF), second curve is related to intra-granularly nucleated ferrite (IGF) and the third to pearlite (P) curve. GBF and IGF curves are divided into two regions, which represents the high temperature and the low temperature segments as consequence of either displacive nature of transformation or diffusion transformation. Addition of Ti to V – micro-alloyed steel in this work seems to be balanced by a slightly higher C and Mn content, leading to limited effect on nucleation stage of austenite decomposition.

In this contribution, vertically aligned carbon nanotubes were synthesized by chemical vapor deposition (CVD). The effects of intrinsic disorders constructed by mobile surface contaminants on the structural perfection of carbon nanotubes (CNTs) were investigated. The results indicated a complete picture on the effect of the involved parameters on the lattice defects of modulated CNTs based on the cooling step. Raman scattering showed that the different cooling methods of the CVD preforms altered the bound complex defects of the structure of the CNTs. Moreover, an array of CNTs was removed from the silicon substrate by applying the neutralized cooling method on the CVD, while the vertical and parallel orientations were retained. The FESEM images, coupled with Raman spectroscopy results, confirm the morphological improvements of the growth CNTs based on the neutralized cooling method.

The demand for economical steels has increased over past years. Steels are expected to have as lean chemistry as

possible and to be easier to fabricate. At the same time they are expected to have properties at least equal to steels which

are being substituted. These demands have been, at least in part, met by V microalloyed medium carbon forging steels

in order to substitute traditional quenched and tempered (Q+T) steels. In spite of some lower toughness, V microalloyed

medium carbon forging steels broaden its application due to considerable energy save by eliminating the heat treatment

from the production route. During continuous cooling, dominantly acicular ferrite microstructure is formed. Main

characteristics of acicular ferrite are intragranular nucleation and strongly disorganized microstructure with a larger

ability to deflect cracks. Acicular ferrite is, therefore, widely recognized to be a desirable microstructure due to good

mechanical properties [5]. On the other hand, generally, data related to isothermal decomposition seems to be lacking.

Therefore, the aim of the present study is to clarify the influence of transformation temperature and time on austenite

isothermal decomposition in V-microalloyed forging steels.