Key Engineering Materials Vol. 835

Abstract: The present article presents cumulative works, which were carried out in the field of micro-alloying steel processing at Central Metallurgical R&D Institute (CMRDI) and/or full scale trials in collaboration with the Egyptian steel industry.It was agreed upon defining three main generations of processing micro-alloying steel. The 1^stgeneration starts officially on 1975 and continues up to 1995, where it deals with using Ti and V as micro-alloying elements for steel long products. On the year 1985, Central Metallurgical R&D Institute (CMRDI) succeeded to implement of HSLA V-micro-alloyed rebar steel grades at Delta steel mills instead of conventional rebar grades.The 2^nd generation was starting on late 1995 and continued to 2005. It was dealing mainly with low carbon content steel (0.04-0.08 %) for flat products (plate and sheet). The most successfully used micro-alloying element was Nb. Beside its precipitate forming effect, Nb is working as substitution solid solution strengthener. Moreover, it raises the recrystallization temperature (Tr). Mainly, micro-alloyed flat steels were developed to fulfill the requirements of the American Petroleum Institute (API) specifications 5L- Product Specification Levels (PSL1) and (PSL2) for manufacturing oil and natural gas pipelines. Meanwhile, a newly born Compact Slab Processing (CSP)-hot strip direct rolling technology was created. On years 2002, the metal forming department in CMRDI succeeded to implement controlled rolling of hot strip Nb-steel sheet at the Compact Slab Process (CSP) Machine in Alexandria National Iron and Steel (ANSDK) Company. Controlled hot rolling schedules were used and followed by early and late cooling at the run out table (ROT). Both contracts were fruitfully succeeded to introduce the API X52 grade at ANSDK Company, followed by X60, and X70 steel grades at Ezz Flat Steel (EFS) Company. The essential mechanical properties of the processed API steel sheets were matched with the API 5L-PSL2 specifications.The 3^rd generation was initially developed after 2005 and continued up to day. It deals with micro-alloying with special functional elements like Boron (B). Boron was favored as a micro-alloying element for bilateral effects. Boron carbide (B₄C) precipitates are the hardest after diamond, which would be reflected on raising the mechanical properties of the steel. Moreover, Boron was favorably used because it delays the temper embrittlement phenomena. On year 2014, the National for Military Industrialization authority requested from CMRDI to collaborate with Military Factory 100 to develop a technology package for processing armor steel plates. Trials were started with a 3^rd generation B-micro-alloyed steel alloy. Many other alloying elements were used beside Boron to develop extra high strength 6.0 mm thickness plates. Finish hot rolled plates were then subjected to a subsequent water quenching from 900 °C and followed by tempering at 250 °C for 20 min. Representation 50X50 cm² steel plates were successfully passed after 3 bullets in front and 3 bullets rear shooting.

Abstract: Renewable energy attracts many researchers as the non-renewable one has negative environmental impacts and limited availability. One of the main types of renewable energy is the blue energy where electricity is generated by water waves using triboelectric nanogenerators (TENGs). Thin films play an important role in the performance and therefore the efficiency of TENGs as they represent the electrodes between which electrons move producing electricity. In order to increase the generated electricity from TENGs, the properties of these electrodes should be modified. Therefore, in this paper, nano- and micro-size thin films are fabricated and characterized by measuring the geometrical parameters and electrical properties. Thin films are fabricated using aluminum with thicknesses 0.5 μm and 1.5 μm on acrylic substrate and 0.5 μm copper film on different types of dielectric materials including PVC and polystyrene. Atomic force microscopy is used to measure the geometrical parameters of the fabricated films including thickness and surface roughness. Also, Gwyddion software is used for the grain size evaluation. On the other hand, Keithley is used for measuring the electrical properties including electrical conductivity and sheet resistance. It is found that the electrical conductivity of aluminum films is inversely proportional to the thickness. The corresponding measured values of the electrical conductivity of the fabricated thinner and thicker aluminum films equal 1.7 x 10⁷ (Ω.m)^-1 and 1.4×10⁷ (Ω.m)^-1, respectively. Whereas, the electrical conductivity of the fabricated copper film equals 8.8×10⁷ (Ω.m)^-1. In addition, the temperature effects on the electrical conductivity are studied. Finally, simulation of a TENG using COMSOL software is accomplished in order to evaluate the electrical outputs of potential, charge, and energy.

Abstract: Despite that the conventional CSiMn TRIP steel has a promissing mechanical attributes, it has a limitations on the galvanizability of such grades of steel due to Silicon. Thus, aluminum as a strong candidate for substituting silicon has been introduced in this study accompanied by vanadium as a microalloying element. Microstructure of the studied steel was observed by using OM, and SEM. X-ray diffraction analysis, and tent-etching technique carried out on the studied steel to identify the fractions of the retained Austenite after thermal mechanical process, as well as its morphology. In addition, the mechanical properties in term of strength, ductility, strain hardening, and the rate of strain hardening were studied to define the influenced parameters throughout this alteration. The results refer to the possibility of complete replacement of silicon in TRIP steel with aluminum at the presence of vanadium as a micro alloying element.

Abstract: Abstract. Designing highly protective and superior electrically conductive coatings from Cobalt-manganese doped/un-doped oxide materials (CMOs) is the main target of this study. The as-prepared nanopowders were synthesized via glycine nitrate process (GNP) at moderate annealing temperature afterword characterized using several techniques including X-rays diffraction (XRD), Field emission scanning electron microscopy (FE-SEM) and electrochemical impedance measurements at room temperature. The XRD results revealed a pure phase of spinel structure with particle size range 75-81 nm for the doped CMO samples. SEM micrographs exhibited morphology with fine aggregate of particles. The incorporation of different ions of Cu, Ni, Fe and Na into the CMOs structure showed a significant increase in the diffusivity of ions and remarkable improvement in the crystallinity. AC electrical conductivity was also measured for the compacted pellets after sintering at 850°C using the electrochemical impedance spectroscopy technique at room temperature. From the obtained results it could be concluded that the polarization resistance of pure and modified CMOs samples show similar behavior ranged from 5 to 6 k Ω.

Abstract: The purpose of this study aims to investigate the surface morphology and roughness of Aluminum induced glass texturing (AIT) substrate after different surface treatments. Aluminum layers were deposited in thickness 370 nm and 240 nm on corning glass sheet using Radio Frequency (RF) power. The effect of different concentrations of hydrofluoric acid (HF), 4%, 5% and 6% on morphology, optical absorption and surface roughness of glass was described. The dipping time of coated glass sheet in HF for 2 min and 5 min created very rough and soft surface, respectively. Optical absorption of AIT substrate after dipping in HF was measured. The optimum texturing process achieved by deposition of aluminum layer 240 nm of thickness and dipping the substrate in 5% HF. The AIT substrate was characterized by low angle X-ray diffraction (XRD), ultraviolet-visible spectrophotometer (UV-VIS), stylus profiler and scanning electron microscope (SEM).

Abstract: Ti-12Mo/ZrO₂ nanocomposites are fabricated using the powder metallurgy technique for the potential of aerospace applications. Titanium-12 wt. % molybdenum metal matrix composite containing various percentages of ZrO₂ (5, 10, and 15 wt. %) are prepared. The phase composition and microstructure of Ti-12Mo/ZrO₂ powder, as well as the consolidated composites), are investigated by both X-ray diffraction and scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) respectively. All the consolidated composites are characterized by measuring the density, Vickers hardness, and wear rate. XRD refers to no new phase are formed between Ti, Mo, and ZrO₂ during the sintering process. Also, a good microstructure is achieved. Results indicated that the density of the sintered composites is increased with increasing ZrO₂ percent up to 5 wt. %. On the other hand, the highest hardness and highest wear resistance are achieved for 5 wt. % ZrO₂ sample. The present work demonstrated that Ti-12Mo/ZrO₂ composites have a high potential for aerospace applications.

Abstract: This work deals with the deposited cadmium sulfide (CdS) quantum dots thin films on transparent conductive fluorine-doped tin oxide (FTO) substrates prepared by successive ionic layer adsorption and reaction technique (SILAR). QD deposition based on SILAR is easy, cheap and effective method which improves the surface quality and performance of QD-based devices. The effect of the number of cycles of SILAR on the morphology and size of the quantum dots has been investigated. SILAR technique was adopted for the deposition of CdS on anatase TiO₂ and the three main factors contributing to the performance of QDs processed by SILAR, namely the number of cycles used, the concentration of the precursor solution, and the reaction dipping time, are discussed. The structural, morphological and optical properties were studied using X-ray diffraction (XRD), Field emission scanning electron microscope (FESEM), Raman spectra analysis and UV-Vis NIR analysis, respectively. The particle size of CdS was calculated from XRD pattern using Debye Scherrer’s equation and the calculated particle size was 4.5-9.5 nm. Using CdSQDs, quantum dot sensitized solar cells (QDSSC) were fabricated on FTO substrates as being a transparent conductive oxide. Optical absorption property proved that the band gap energy value was about 2.44 eV. The result delivered from J-V curve revealed that the overall energy conversion efficiency increased with increasing the deposition cycles giving the best efficiency of 2.73 % at 7 cycles.

Abstract: This article reports the corrosion behavior of 904L weldment in sulfuric acid as a strong corrosive media. The corrosion behavior was studied by total immersion tests and potentidynamic polarization test. Total immersion test has been conducted at different acid concentrations typically: 1, 2, 4, 6, 8 and 18.4 M at 25°C. The effect of temperature (25- 100°C) on the weight loss measurements of the alloy samples was followed in the 4 M acid solution. On the other hand, potentiodynamic polarization tests were conducted in 2,5, 8 and 18.4 M H₂SO₄ solution. The potentiodynamic polarization test was also conducted in the practically used leaching medium (2 M H₂SO₄ + 10% monazite).Results show that the weight loss increases with the increase of acid concentration and reaches its maximum at 4 M H₂SO₄ and then gradually decreases. Meanwhile, the rise in temperatures results in the increase of weight loss. Potentiodynamic polarization tests indicate that the 5 M acid solution gives the highest corrosion rate of 0.6399 mm/Y. The leaching medium shows relatively higher corrosion rate (0.124 mm/y) than the corresponding 2 M H2SO4 without monazite (0.01712 mm/y).