Tribological Properties of TiO<Subscript>2</Subscript> Reinforced Nickel Based MMCs Produced by Pulse Electrodeposition Technique

Nickel–TiO₂ composite coatings were prepared under pulse current conditions by co-deposition of TiO₂ particles and nickel from a Watts type bath. The effect of TiO₂ particle concentration was studied on microhardness, friction coefficient and wear resistance. The morphological features and the structures were studied by scanning electron microscope, X-ray diffraction analysis and 3D profilometry facilities. A wide particle size range (between 95 and 140 nm) was chosen to provide a high dispersion and load bearing ability for the co-deposited layers. It was determined that increasing the particle concentration in the electrolyte dramatically increased the co-deposited TiO₂ particles in the coating. The results showed that the high concentration of TiO₂ particles in the electrolyte yielded the highest amount of particles co-deposited in the plating layer. The influence of the co-deposited TiO₂ volume on microstructure and tribological properties in the coating were investigated. The wear tests were carried out using a constant load by a reciprocating ball-on disk configuration. Wear loss and friction coefficients of Ni/TiO₂ composites were decreased by increasing TiO₂ content in the electrolyte because of the increasing content of TiO₂ in the deposited layer. The change in wear mechanisms by changing TiO₂ content was also determined.     

RELATIONSHIP BETWEEN ORGANIC MATTER,SULPHUR AND PHOSPHATE CONTENTS IN UPPER CRETACEOUS MARINE CARBONATES (KARABOGAZ FORMATION,SE TURKEY): IMPLICATIONS FOR EARLY OIL GENERATION

In this paper, we discuss the relationship between the organic matter, sulphur and phosphate contents of Upper Cretaceous marine carbonates (Karabogaz Formation) in the Adiyaman Petroleum Province of SE Turkey. The results of organic geochemical analyses of core samples obtained from the Karabogaz Formation suggest that phosphate deposition occurred in settings where the water column was oxic to sub-oxic. However, the preservation of organic matter was favoured in anoxic environments. Moreover, the presence of sulphur (especially sulphur incorporated into kerogen) in organic matter-rich layers led to early oil generation. The results of stepwise py-gc analyses are consistent with a model in which, with increasing maturity, S-S and C-S bonds are the first to be eliminated from the macromolecular kerogen structure. Study of the maturity evolution of S-rich kerogen by laboratory pyrolysis implies that marginally mature and/or mature kerogen in the Karabogaz Formation, which may be classified as classic “Type II” kerogen, was most probably Type II/S at lower maturity stages. This enabled oil generation to occur at relatively shallow burial depths and relatively early stages of maturation. It is reasonable to conclude that Type II/S kerogen, overlooked in previous studies, was abundant in TOC-rich intervals in the Karabogaz Formation. Early generation (and expulsion) from Type II/S kerogen may have sourced the sulphur-rich oils in the Adiyaman area oilfields.     

Hydrogen effects in a dual-phase microalloy steel

A dual-phase steel containing niobium, vanadium and titanium as microalloying elements was tested for hydrogen embrittlement (HE). The susceptibility to HE was observed to be closely related to the microstructural state. Hydrogenated specimens intercritically annealed at relatively low temperatures to develop martensite islands in a ferrite matrix basically exhibited quasi-cleavage fracture with some ductile dimpling. The mode of fracture in charged specimens quenched from higher intercritical annealing temperatures was predominantly intergranular fracture along prior austenite grain boundaries and cracking of martensite laths. The detrimental role of residual stresses, retained austenite and microalloying carbides in the process of HE is discussed.     

Corpora compilation for prosody-informed speech processing

Language Resources and Evaluation - Research on speech technologies necessitates spoken data, which is usually obtained through read recorded speech, and specifically adapted to the research needs....     

Experimental studies on mechanical properties of cellular structures using Nomex® honeycomb cores

An experimental method is presented to obtain the effective in-plane compliance matrices of cellular structures using Nomex® honeycomb cores without a priori assumptions such as orthotropy. In this method, firstly, uni-axial tension tests are carried out for different material orientations. The independent variables in these experiments are the material orientation and displacement of the actuator, while the main dependent variables are positions of the marker points and the force acting on the specimens. Marker tracking technique is used to determine the marker positions which are processed to get strain of the measuring domain, while the stress is estimated through external loading and core geometry. The analysis is confined to the measuring domain under near homogeneous stress and strain fields. The experiment results are processed with transformation and least squares functions to obtain all effective in-plane elastic parameters, which are compared with analytical solution based on deformation of idealized cell structure. Through this comparison, the effects of geometrical parameters of cell structure are discussed in detail. By means of the introduced method, the problem of lack of experimental studies on the effective in-plane compliances of cellular structures in the literature is expected to be solved.     

Adsorption of As(V) from Water Using Nanomagnetite

This paper describes a study of the removal of arsenate [As(V)] from aqueous solutions by adsorption on commercial nanomagnetite (NM). The influences of pH, initial arsenate [As(V)] concentration, and adsorbent concentration were investigated in multiple kinetic runs. The adsorption kinetics and isotherms were investigated in batch experiments. The experimental data were determined to be best described by the pseudosecond-order kinetic model. Langmuir and Freundlich isotherms were used to fit the adsorption data from equilibrium experiments. The findings have revealed that NM has high removal efficiency for arsenate, with its capacity to reduce an initial level of 300 to <5-μg/L As(V), i.e., below the limit (10-μg/L As) set for potable water by the World Health Organization.     

Cation deficiency associated with the chemical exfoliation of lithium cobalt oxide

Compositional changes associated with the chemical exfoliation of lithium cobalt oxide, a layered transition metal oxide, are discussed. Starting from a layered bulk structure, lithium cobalt oxide can undergo chemical exfoliation through a two-step method: treatment with a protic acid, then treatment with tetramethylammonium hydroxide (this intercalates the layered structure and yields exfoliated nanosheets). This work provides an in-depth analysis of compositional and structural changes occurring to the powder upon the first step to exfoliation, treatment with acid, revealing variations in vacancies and valence changes depending on the conditions used. Through coupled analysis of X-ray photoelectron spectroscopy, X-ray diffraction, UV-Vis absorption spectroscopy, and inductively coupled plasma-optical emission spectroscopy data, we illustrate that both lithium and cobalt ions are diffusing out the structure along with the dissolution of full unit cells. As such, nanosheets accessed from the bulk by this exfoliation process should not be considered simply as divisions of the original unit cell. This work provides fundamental insights on the stability of LiCoO₂ and the exfoliation of layered transition metal oxides, beyond the access of individual nanosheets, and is vital to determining structure-property relationships of chemically exfoliated nanosheets (eg, changes in valency which dictate catalytic activity, magnetic susceptibility, etc).     

Improving the strength of adhesively bonded joints through the introduction of various surface treatments

The aim of this paper is to model an interface adhesion and failure mechanism of single lap joints, subjected to tensile loading, focusing on the effects of various surface treatments, including surface characterization parameters, such as surface roughness and contact angle of adherend surfaces. The applied surface treatments are sandblasting, etching, anodic oxidation and hybrid processes. The influence of surface treatment techniques and conditions on single lap joint strength and interfacial properties is investigated by performing a static tensile test. A numerical approach, which is a cohesive zone model, is implemented using ABAQUS? and introduced to create a correlation between maximum interface traction and surface processing parameters, such as surface roughness and work of adhesion. As a result of experiments, an etching plus sanding process was found to provide the best single lap joint performance (8726 N), having surface roughness of Ra = 2.93 μm and work of adhesion, W_a = 119.4 mJ/m². Based on numerical solutions, a correlation between maximum interface traction and type of surface treatment process has been established, taking certain assumptions into consideration.     

A pre-feasibility case study on integrated resource planning including renewables

In recent years, economical and environmental constraints force governments and energy policy decision-makers to change the prominent characteristics of the electricity markets. Accordingly, depending on local conditions on the demand side, usage of integrated resource planning approaches in conjunction with renewable technologies has gained more importance. In this respect, an integrated resource planning option, which includes the design and optimization of grid-connected renewable energy plants, should be evaluated to facilitate a cost-effective and green solution to a sustainable future.