The aim of the present work is to investigate the kinetic properties of Co-B nanoparticles which are deposited on graphene sheets by simultaneous chemical reduction of Co þ2 and graphite oxides using NaBH 4 as the reducing agent. The reduced CoÀB/ graphene nanocomposites were characterized by X-ray diffraction, and the effects of the concentration of NaBH 4 , NaOH, and hydrolytic temperature were discussed in detail. The results show that the concentration of NaBH 4 and NaOH indeed exerted a significant impact on the hydrogen generation rate of Co-B/graphene catalysts. Reaction rate of hydrolysis first rises up and then decreases subsequently with the rising of NaOH and NaBH 4 concentration. The results show that the Co-B/graphene catalyst has the high catalytic activity with activation energy of 52.45 kJÁmol À1 , and showed high resistance against deterioration and stability as a function of time. The present method is promising for the synthesis of effective supported catalysts for hydrolysis of NaBH 4 . V C 2015 AIP Publishing LLC.
Ductile cast irons have several engineering and manufacturing advantages compared to other cast materials such as steels. These include high damping capacity, wear resistance, to and lower manufacturing cost. The combination of good mechanical properties and casting abilities of ductile cast iron makes its usage successful in structural applications especially in the energy and automotive industries. In this study, the influence of the section thickness on the microstructure and hardness of spheroidal graphite cast iron was investigated with a cascaded model using the full mold casting method. By the high linear correlation coefficient, R2 > 0.90, it was observed that the section thickness directly affected the microstructure and hardness. An increase in the cross-sectional thickness decreases hardness and number of graphite nodules per square millimeters, however, percentage of ferrite was increased.
The release of Cu into water is an immediate concern that negatively affects environmental health. To eliminate this problem, the adsorption of Cu(II) on varying substances has been studied widely for two decades. The utilization of low-cost adsorbents obtained from industrial wastes hits two targets with one arrow. In the present study, ferrochrome ash (FCA) obtained from the baghouse filters of ferrochrome facilities was utilized to adsorb Cu(II) for the first time in the literature. To achieve this goal, initially the FCA was characterized by XRD, XRF, SEM, EDS, and BET analyses, and then washing and grinding pretreatment was conducted to eliminate the Cr dissolution and increase the surface area of the FCA. Adsorption experiments were conducted in 100–1000 mg/L Cu(II) solution on 0.4–8 g/L FCA for 0–300 min. As a result, it was concluded that a maximum adsorption capacity was obtained as 298.75 mg/g, which makes the FCA an applicable adsorbent for Cu(II) adsorption. Additionally, a pH range of 3–6 is favorable. The Cu(II) adsorption on FCA fits the pseudo-second order (PSO) kinetics and Freundlich isotherm models well. The Cu(II)-adsorbed FCA was investigated by SEM, EDS, and FT-IR analyses. According to the results, it can be deduced that the adsorption mechanism is chemisorption, which involves the valency forces between the metal and the adsorbent.
The spheroidization of the silicon eutectic phase in aluminum is an important parameter for casting and significantly influences the material properties. Sr has been used for a long time for eutectic modification in aluminum and many researches have been made on this subject. In this study, the effect of holding time after Sr addition on the mechanical properties and eutectic phase modification of the aluminum were investigated. 200 ppm Sr was chosen as the amount of Sr and the holding times were chosen as 20, 40 and 80 minutes. Tensile test was performed for the determination of mechanical properties and ultimate tensile strength and percentage of elongation values were measured. In order to quantify eutectic modification, the length / width (aspect ratio) ratios of eutectic silicon particles were measured. In addition, Bifilm Index of the molten metal was determined with the reduced pressure test (RPT). With the increase in the holding time, an increase in the aspect ratio and in the Bifilm Index was measured. It has been observed that the tensile strength and elongation values have decreased as the holding time has increased. Alüminyumdaki silisyum ötektik fazının küreselleşmesi, döküm için önemli bir parametredir ve malzeme özelliklerini önemli ölçüde etkiler. Sr alüminyumda ötektik modifikasyon için uzun süredir kullanılmaktadır ve bu konuda birçok araştırma yapılmıştır. Bu çalışmada Sr ilavesinden sonra bekletme süresinin alüminyumun mekanik özelliklerine ve ötektik faz modifikasyonuna etkisi incelenmiştir. Modifikasyon için 200 ppm Sr, bekletme süreleri ise 20, 40 ve 80 dk. olarak seçilmiştir. Mekanik özelliklerin tespiti için çekme testi yapılarak çekme dayanımı ve uzama değerleri ölçülmüştür. Ötektik modifikasyonu ölçmek için, ötektik silisyum partiküllerinin boy/en oranları ölçülmüştür. Ek olarak, sıvı metalin Bifilm indeksi vakum altında katılaştırma testi (VAK) ile ölçülmüştür. Bekleme süresindeki artışla birlikte, en boy oranında ve Bifilm indeksinde artış gözlenmiştir. Çekme dayanımı ve uzama değerlerinin ise tutma süresi arttıkça azaldığı gözlenmiştir.
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