arif nihat güllüoğlu - Academia.edu (original) (raw)

Papers by arif nihat güllüoğlu

Work-a Journal of Prevention Assessment & Rehabilitation, Jun 26, 2023

DergiPark (Istanbul University), Mar 1, 2019

This study examines the effects of additions of 0.5-5 v/v percentage multi-walled carbon nanotube... more This study examines the effects of additions of 0.5-5 v/v percentage multi-walled carbon nanotubes into the Ti-6Al-4V matrix by mechanical alloying at low rates and investigates the results of the different sintering conditions on the density, microstructure, and Creep behavior. Mechanical properties, microstructural and density of composite materials (Ti64 / CNT) produced by cold isostatic press molding method have been investigated. MWCNTs reinforced metal matrix composite powders were molded by cold isostatic pressing method using polyacrylonitrile (PAN) based binder. The binder decomposition was carried out by heat treatment. After molding, the specimens have been sintered at high temperature in high vacuum (10-2 bar). Metallographic experiments were carried out to examine density and microstructure. Experimental results indicate Ti-6Al-4V particulate can be sintered to up to 98,5% of calculated density. Maximum hardness was obtained 538 HV at 1300 o C for 3 hours and creep life inverse. By using SEM and X-ray diffractometer the characteristics of produced composite samples were investigated. Although Ti-6Al-4V alloys are used as biomaterial, this study aimed at using MWCNTs containing Ti-6Al-4V composites at high temperature applications. Because MWCNTs reinforced Ti-6Al-4V composites are cheaper and has lower weight than the other materials used in this kind of applications.

Journal of Mining and Metallurgy, Section B, 2013

In this paper, adsorption of gold from chloride media using commercial sorbent (Lewatit TP 214 (L... more In this paper, adsorption of gold from chloride media using commercial sorbent (Lewatit TP 214 (L-214)) and biomass residue (rice hull (RH)) were investigated. The different adsorption parameters, sorbent dosage, contact time, temperature and pH of solution on adsorption (%) were studied in detail on a batch sorption. Before the RH was activated, adsorption (%) was poor compared with L-214. However, after the RH was activated at 1000 °C under an argon atmosphere, the gold adsorption (%) increased four-fold. X-ray fluorescence (XRF) was used to explore the feasibility this material as an adsorbent for the removal of gold from aqueous solutions. The adsorption equilibrium data were best fitted with the Langmuir isotherm model. The maximum adsorption capacities, Q max , at 25 °C were found to be 93.46 and 108.70 mg/g for the activated rice hull (ARH) and L-214, respectively. Thermodynamic calculations using ΔH°, ΔS°, ΔG° and E a values indicate that the adsorption process was spontaneous and endothermic.

Journal of Composite Materials, Jul 28, 2016

The aim of this study is to investigate the effect of surface geometry for low-velocity impact ap... more The aim of this study is to investigate the effect of surface geometry for low-velocity impact applications. To achieve this purpose, aramid fiber-reinforced laminated polyester composite with various geometries such as cylindrical, elliptical, and spherical were prepared, and low-velocity impact properties were investigated numerically and experimentally. All properties such as orientation, fiber volume fraction, matrix material, and average thickness are the same in all samples. Experimental low-velocity impact behaviors of structure were determined by drop weight tester at low velocity 2.012 m/s. Simulations were carried out by LS-Prepost 4.2 and LS-Dyna v971 software. By this way, results of impact tests were verified and modeled with finite element method. Results of the impact tests showed that the elliptical samples have the highest energy absorption capability due to effective stress transfer capacity. According to experimental results, maximum energy absorption rate difference is 17% between elliptical 10 mm and cylindrical 5 mm geometries.

Cmes-computer Modeling in Engineering & Sciences, Mar 1, 2000

Twins in growing crystals are due to excessive thermal stresses induced by the temperature gradie... more Twins in growing crystals are due to excessive thermal stresses induced by the temperature gradients developed during the growth process. Twinning is an important defect in advanced semiconductor crystals such as GaAS and InP. The objective of this study is to develop a computational model to predict the twin formation in the Gallium Arsenide (GaAs) crystals grown by the vertical gradient freeze method (VGF). A quantitative quasi-steady state thermal stress model is developed here for predicting the twinning formation in GaAs grown by VGF. The thermoelastic stresses in VGF grown crystal are calculated from a two-dimensional finite element analysis. Deformation twins form as a result of the high shear stresses acting on the twinning plane and in twinning direction. In the study, the resolved shear stress (RSS) distributions in the twin systems for different growth directions have been calculated. This investigation is expected to further the understanding of twinning formation during crystal growth for different growth direction. keyword: Twinning, crystal growth, the Gallium Arsenide, Vertical Gradient Freeze method.

Mining, metallurgy & exploration, May 1, 2013

Pistachio nut shells, an agricultural waste biomass, and Lewatit TP 214, a commercial sorbent, we... more Pistachio nut shells, an agricultural waste biomass, and Lewatit TP 214, a commercial sorbent, were investigated as adsorbents for the adsorption of platinum from dilute hexachloroplatinic acid solutions. Before the pistachio nut shells were carbonized, adsorption percentage was 65%, whereas Lewatit TP 214 ensured almost 100% adsorption. However, after the pistachio nut shell was carbonized at 1,000° C under an argon atmosphere, the platinum adsorption (%) increased twofold. The effects of such parameters as sorbent dosage, contact time, temperature and solution pH on adsorption were studied in detail in batch mode. The adsorption equilibrium data were best fitted with the Langmuir isotherm model. The maximum adsorption capacities, Q max , at 25° C were found to be 38.31 and 33.22 mg/g for the carbonized pistachio nut shell and Lewatit TP 214, respectively. The adsorption of platinum on both sorbents was found to be described by the pseudo-second-order kinetic model. The results indicated that the activated carbon prepared from pistachio nut shells can be effectively used for the removal of platinum from acidic solutions.

Integrated Ferroelectrics, Nov 11, 2010

Modification induced by energetic ion in polyvinylchloride (PVC)/carbon black (CB) composites was... more Modification induced by energetic ion in polyvinylchloride (PVC)/carbon black (CB) composites was studied using impedance gain-phase analyzer, differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and atomic force microscopy (AFM). Different ...

Acta Materialia, Jun 1, 1999

ÐThe generation and multiplication of dislocations in an indium phosphide (InP) single crystal gr... more ÐThe generation and multiplication of dislocations in an indium phosphide (InP) single crystal grown by the vertical gradient freeze (VGF) process is predicted using a crystallographic model. This model couples microscopic dislocation motion and multiplication to macroscopic plastic deformation during the crystal growth process. During growth of an InP crystal, dislocations are generated in the plastically deformed crystal as a result of crystallographic glide caused by excessive thermal stresses. The temperature ®elds are determined by solving the partial dierential equation of heat conduction in a VGF crystal growth system. The eects of growth direction and growth parameters (i.e. imposed temperature gradients, crystal radius and growth rate) on dislocation generation and multiplication in an InP crystal are investigated. Dislocation density patterns on the cross section of an InP crystal are numerically calculated and compared with experimental observations.

Karaelmas iş sağlığı ve güvenliği dergisi, Dec 30, 2019

Artan nüfus ile birlikte insan ihtiyaçlarının karşılanmasında inşaat sektörü kendisine bağlı ... more Artan nüfus ile birlikte insan ihtiyaçlarının karşılanmasında inşaat sektörü kendisine bağlı 200 den fazla alt sektör ile ekonominin lokomoti i olma özelliğini taşımaktadır. Sektör bünyesinde birçok meslek dalını kapsaması nedeniyle iş gücü kapasitesi oldukça yüksektir. I nşaat sektörü, tüm dünyada olduğu gibi ülkemizde de en büyük ve tehlikeli sektörlerinden biridir. Günümüzde gelişen teknoloji ile büyüyen ihtiyaçların sonucu olarak çalışanlar daha fazla iş kazasına maruz kalmakta, çalışanların sağlığına ve iş güvenliğine yönelik tehlikeler artmaktadır. Sektörde yaşanan kazalar her yıl çok sayıda yaralanma ve can kaybı ile sonuçlanmaktadır. I nşaat sektörü iş kazalarının sayısal çokluğu ve ölümle sonuçlanan kazaları bakımından diğer iş kolları arasında ilk sırada yer almaktadır. Bu çalışmada 2008-2017 yılları arasında Türkiye genelinde ve inşaat sek-töründe meydana gelen iş kazalarına ait veriler karşılaştırmalı olarak incelenerek analiz edilmiştir. Ayrıca, ülkemiz inşaat sektörü için hesaplanan kaza sıklığı ve ölümlü kaza sıklığı değerleri Avrupa birliği üye ülkeleri ile karşılaştırılarak mevcut durum mukayese edilmiştir.

Being one of the oldest electric welding processes, the resistance spot welding offers practical ... more Being one of the oldest electric welding processes, the resistance spot welding offers practical and time saving applications in the field of joining metals of several manufacturing industries such as automotive, white goods and machinery. Even light weight metals, i.e. aluminum and magnesium has lately been taking attention of researchers and producers, the steels, especially austenitic stainless steels are still being used in wide range of applications due to their combination of excellent corrosion resistance with comparably low price, good machinability, reasonable weldability and good mechanical properties. Spot welding process is controlled by three essential parameters; mechanical (pressure), electric (heat) and electronics (time). In this study, AISI 304 and 316L stainless steel sheets of 1 mm of thickness were used as welding metals. Thus, AISI 304 welding metal couples, AISI 316L welding metal couples and AISI 304 and 316L welding metal couples were selected to ensure a co...

Archives of materials science and engineering, 2014

Polymers and Polymer Composites, 2009

Poly(styrene-co-acrylonitrile) (SAN) which is a random, amorphous, linear copolymer produced by c... more Poly(styrene-co-acrylonitrile) (SAN) which is a random, amorphous, linear copolymer produced by copolymerising styrene and acrylonitrile was investigated experimentally. Specimens were supplied from a private company and they were analysed using a differential scanning calorimetry machine (DSC). The behaviour of the material in creep, tension and hardness experiments was investigated experimentally at several temperatures. The creep response of SAN was also evaluated.

Scripta Metallurgica, 1989

Polymer-Plastics Technology and Engineering, 2008

... Consequently, it can be said that the proposed model is suitable for use in the applications ... more ... Consequently, it can be said that the proposed model is suitable for use in the applications showing linear viscoelastic behavior. ACKNOWLEDGMENT. ... 104M130. Thanks are also due to O. Yenici and Ismail Topcu for their help. REFERENCES. ...

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2009

Modelling and Simulation in Materials Science and Engineering, 1993

... frequency and state of the applied stress, the following steps during evolution of dislocatio... more ... frequency and state of the applied stress, the following steps during evolution of dislocation ... nature of the problem, the dislocation at the origin and its neighboring dislocation ... The effect of frequency on the dislocation structures during cyclic deformation has been simulated with ...

Journal of Non-Crystalline Solids, 2010

In this study, composite films consisting of an insulating polymethyl methacrylate (PMMA) polymer... more In this study, composite films consisting of an insulating polymethyl methacrylate (PMMA) polymer matrix and metal powder (Cu) additive were prepared by solution costing method. These films were irradiated with 140 MeV silver ions at the fluences of 1 Â 10 11 ions/cm 2 and 1 Â 10 12 ions/cm 2. The radiation induced changes in dielectric, structural and surface properties of PMMA/Cu composites were studied using impedance/gain phase-analyzer, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). It was observed that the dielectric properties and ac electrical conductivity increased significantly with the concentration of dispersed metal powder (Cu) and also with the fluence. This reveals that ion beam irradiation creates free radicals, unsaturation etc. due to emission of hydrogen and/or other volatile gases, which makes the polymer more conductive. XRD analysis of the pristine and irradiated samples shows that the crystallinity improved upon irradiation at low fluence and deteriorated on further increase of the fluence, which could be attributed to cross linking of polymer chains at low fluence and degradation at higher fluence. High energy ion beam irradiation of semicrystalline polymer composite films changes its Tg behavior as observed from DSC analysis. This result is also corroborated with the results of XRD. The average surface roughness and topography of surfaces changed with the concentration of filler and also with the ion fluence as revealed from AFM/SEM analysis.