The effect of austenitizing time on martensite morphologies and magnetic properties of martensite in Fe–24.5%Ni–4.5%Si alloy

The effect of austenitizing time on the formation of martensite in Fe–24.5%Ni–4.5%Si alloy has been studied by means of transmission electronmicroscope (TEM), scanning electronmicroscope (SEM) and Mössbauer spectroscopy technique. TEM and SEM observations revealed that the martensite morphology was found to be closely dependent on the austenitizing time. The orientation relationship between austenite and thermally induced martensite was found as the Kurdjumov-Sachs type. The volume fraction changes of martensite and austenite phases, the hyperfine magnetic field of martensite phase and isomery shift values have been determined by Mössbauer spectroscopy. The Mössbauer study also revealed that the martensite volume fractions increased with increasing austenite grain size.     

Surface modification of polysulfone based hemodialysis membranes with layer by layer self assembly of polyethyleneimine/alginate-heparin: a simple polyelectrolyte blend approach for heparin immobilization

This study intends to improve blood compatibility of polysulfone (PSF) membranes by generating a nonthrombogenic surface through heparin immobilization. To achieve this task, the support membrane prepared from a blend of PSF and sulfonated polysulfone (SPSF) was modified with layer by layer (LBL) deposition of polyethyleneimine (PEI) and alginate (ALG) and heparin blended with ALG was immobilized only on the outermost surface of the LBL assembly. The results have shown that the adsorption of human plasma proteins and platelet activation on the LBL modified membranes decreased significantly compared with the unmodified PSF and PSF-SPSF blend membranes. Furthermore, blending ALG with a small amount of heparin remarkably prolonged the APTT values of heparin free PEI/ALG coated membranes. It is envisaged that the use of a blend of HEP and ALG only in the terminating layer of the LBL assembly can be an economical and alternative modification technique to create nonthrombogenic surfaces.     

Some characteristics of thermally induced martensite in Fe–30%Ni–3.6%Mo alloy

Kinetical, morphological and magnetic characteristics of thermally induced martensite in an Fe–30%Ni–3.6%Mo alloy has been studied by scanning electron microscopy, transmission electron microscopy and Mössbauer spectroscopy. Scanning electron microscope and transmission electron microscope observations revealed the occurrence of both athermal and isothermal martensitic transformation in the alloy. In addition, the magnetic properties of both the austenite and martensite phases were determined by the Mössbauer spectroscopy. The Mössbauer spectra showed a paramagnetic character for the austenite phase and an antiferromagnetic character for the martensite phase.     

Comparative Assessment of Ambient Air Quality of Major Cities of Pakistan

The deterioration of ambient air quality is one of the emerging environmental problems in developing countries of South Asia. Unplanned urbanization, population growth, degradation of vegetation cover and industrial and vehicular emissions, particularly in urban areas, have resulted in substantial rise in the level of air pollutants and emission sources. This study focused on monitoring of different cities as per traffic volume and flow. Air quality monitoring was conducted on hourly basis to determine the major parameters; i.e. PM₁₀, NO_x, SO₂, CO by using fixed station for 8 h from 1:30 pm to 9:30 pm. All the measuring values were then compared with the National Environment Quality Standards (NEQS) and Air Quality Index (AQI). Results revealed that the concentration of PM₁₀ at the selected areas of these cities ranged from 156 to 390 μg/m³, CO ranged from 1.18 to 6.01 mg/m³, and NO_x ranged from 32.65 to 129.47 μg/m³. It was evident that all these concentration had been higher than the permissible limits of NEQS, whereas only SO₂ was found within the permissible limits (15.60–110.52 μg/m³⁾. Air Quality Index (AQI) of all the designated points of cities was also assessed, and most of the vehicular and commercial areas had shown unhealthy and severe conditions ranging from 191 to 320, respectively.

     

Review on carbon-derived,solid-state,micro and nano sensors for electrochemical sensing applications

The aim of this review is to summarize the most relevant contributions in the development of electrochemical sensors based on carbon materials in the recent years. There have been increasing numbers of reports on the first application of carbon derived materials for the preparation of an electrochemical sensor. These include carbon nanotubes, diamond like carbon films and diamond film-based sensors demonstrating that the particular structure of these carbon material and their unique properties make them a very attractive material for the design of electrochemical biosensors and gas sensors.Carbon nanotubes (CNT) have become one of the most extensively studied nanostructures because of their unique properties. CNT can enhance the electrochemical reactivity of important biomolecules and can promote the electron-transfer reactions of proteins (including those where the redox center is embedded deep within the glycoprotein shell). In addition to enhanced electrochemical reactivity, CNT-modified electrodes have been shown useful to be coated with biomolecules (e.g., nucleic acids) and to alleviate surface fouling effects (such as those involved in the NADH oxidation process). The remarkable sensitivity of CNT conductivity with the surface adsorbates permits the use of CNT as highly sensitive nanoscale sensors. These properties make CNT extremely attractive for a wide range of electrochemical sensors ranging from amperometric enzyme electrodes to DNA hybridization biosensors. Recently, a CNT sensor based fast diagnosis method using non-treated blood assay has been developed for specific detection of hepatitis B virus (HBV) (human liver diseases, such as chronic hepatitis, cirrhosis, and hepatocellular carcinoma caused by hepatitis B virus). The linear detection limits for HBV plasma is in the range 0.5–3.0 µL^? 1 and for anti-HBVs 0.035–0.242 mg/mL in a 0.1 M NH₄H₂PO₄ electrolyte solution. These detection limits enables early detection of HBV infection in suspected serum samples. Therefore, non-treated blood serum can be directly applied for real-time sensitive detection in medical diagnosis as well as in direct in vivo monitoring.Synthetic diamond has been recognized as an extremely attractive material for both (bio-) chemical sensing and as an interface to biological systems. Synthetic diamond have outstanding electrochemical properties, superior chemical inertness and biocompatibility. Recent advances in the synthesis of highly conducting nanocrystalline-diamond thin films and nano wires have lead to an entirely new class of electrochemical biosensors and bio-inorganic interfaces. In addition, it also combines with development of new chemical approaches to covalently attach biomolecules on the diamond surface also contributed to the advancement of diamond-based biosensors. The feasibility of a capacitive field-effect EDIS (electrolyte-diamond-insulator-semiconductor) platform for multi-parameter sensing is demonstrated with an O-terminated nanocrystalline-diamond (NCD) film as transducer material for the detection of pH and penicillin concentration. This has also been extended for the label-free electrical monitoring of adsorption and binding of charged macromolecules. One more recent study demonstrated a novel bio-sensing platform, which is introduced by combination of a) geometrically controlled DNA bonding using vertically aligned diamond nano-wires and b) the superior electrochemical sensing properties of diamond as transducer material. Diamond nano-wires can be a new approach towards next generation electrochemical gene sensor platforms.This review highlights the advantages of these carbon materials to promote different electron transfer reactions specially those related to biomolecules. Different strategies have been applied for constructing carbon material-based electrochemical sensors, their analytical performance and future prospects are discussed.     

The effect of nitrogen flow rate on TiBN coatings deposited on cold work tool steel

TiBN coatings have high hardness and high adhesion. Due to these excellent properties there has been increasing interest in TiBN coatings. In this study, TiBN coatings were deposited on AISI D2 cold work tool steel and silicon wafers by closed field unbalanced magnetron sputtering (CFUBMS). The structural, mechanical and adhesion properties of these coatings were analysed by X-ray diffraction, scanning electron microscopy, microhardness test, indentation test and scratch tests. TiBN coatings produced by magnetron sputtering exhibited a dense and columnar structure. These results indicate that TiB₂, TiN and h-BN exist in crystalline forms at all coatings. The highest hardness was obtained at the lowest nitrogen flow rate. Very few cracks were observed at the edge of the indentation marks at the highest nitrogen flow rate. The highest critical load obtained with scratch test was identified as 102?N.     

Nanocrystalline diamond film for biosensor applications

In this study, we have developed a novel capacitive biosensor based on interdigitated gold nanodiamond (GID-NCD) electrode for detection of C-reactive protein (CRP) antigen. CRP is one of the plasma proteins known as acute-phase proteins and its levels rise dramatically during inflammatory processes occurring in the body. It has been reported that CRP in serum can be used for risk assessment of cardiovascular diseases. The antibodies immobilization were confirmed by fourier transform spectroscopy (FTIR) and contact angle measurements. In this capacitive biosensor, nanocrystalline diamond acting as a dielectric layer between the electrodes. The CRP antigen detection was performed by capacitive/dielectric-constant measurements. Our results showed that the response of NCD-based capacitive-based biosensor for CRP antigen was dependent on both concentration (25–800 ng/ml) as well as frequency (50–350 MHz). Furthermore, using optimized conditions, the biosensors developed in this study can be potentially used for detection of elevated level of risk markers protein in suspected subjects for early diagnosis of disease.     

Effect of V,Nb, Ti and graphite additions on the hydrogen desorption temperature of magnesium hydride

In this study the effects of mechanical milling with 5 wt.% of additives (V, Nb, Ti and Graphite) on the hydrogen desorption temperature of the magnesium hydride (MgH₂) were studied. The powder mixtures were mechanically milled for 2 h. X-ray diffraction (XRD), scanning electron microscope (SEM), and optical microscope (OM) techniques were used for the structural and morphological characterization of powders. Differential scanning calorimeter (DSC) was used to investigate the effects of the mechanical milling with additives on the hydrogen desorption temperature of the magnesium hydride powder. DSC results show that the hydrogen desorption temperatures of mechanically milled MgH₂ with additives are depressed about ∼40–50 °C compared with that of as-received MgH₂. The particle size analysis results indicate that decrease of the particle size of powders leads to a decrease of the hydrogen desorption temperature. Moreover, increasing specific surface area can also contribute to a decrease on the hydrogen desorption temperature.     

Refuse-derived fuels as a renewable energy source in comparison to coal,rice husk,and sugarcane bagasse

The calorific potential of refuse-derived fuels (RDFs) was investigated with different coals, rice husk, and sugarcane bagasse. Carbon-sulfur analysis, gross calorific value (kJ/kg), and proximate analysis (%) were carried out. Total carbon of coal samples was found to be in the range from 62.65 to 79.19%, while RDF samples were ranged from 40.21 to 57.34% which were almost similar to rice husk (49.13%) and sugarcane bagasse (46.13%). Comparison of the total sulfur content of the coal (Duki) (10.52%) was very high as compared to RDF samples ranged from 0.17 to 0.46% and almost similar to rice husk (0.34%) and sugarcane bagasse (0.187%), while other coal samples ranged from 2.1 to 4.5%. The gross calorific value of the coal (Duki) (6,163 kJ/kg) was higher to other coal samples ranged from 4,935 to 4,972 kJ/kg, while found to be almost double to rise husk (3,518 kJ/kg), sugarcane bagasse (3,285 kJ/kg), and RDF samples (3,125–4,689 kJ/kg). The moisture content, volatile matter, and ash content were found higher in RDF 1 (42.14%), RFD 2 (66.55%), and coal (stone) (33.14%), respectively. Appropriate gross calorific value and very low sulfur content of the RDFs, especially RDF 2, appeared adequate to be used as a fuel with a lesser pollution potential and as an alternative fuel in mega cement industry of Pakistan.     

Hydrogen treated TiO2 nanoparticles onto FTO glass as photoanode for dye-sensitized solar cells with remarkably enhanced performance

Hydrogen treatment is a facile and efficient approach for the enhancement in the functioning of TiO₂ nanoparticles for dye-sensitized solar cells (DSSC). In this work, TiO₂ nanoparticles have been synthesized in the hydrogen environment followed by the deposition onto FTO glass substrates with various film thickness as photoanodes for DSSC. The synthesized hydrogen treated TiO₂ nanoparticles based photoanodes have showed significantly improved photocurrent in the resulting fabricated devices. SEM and TEM analyses have confirmed the particle size and morphology of TiO₂ nanoparticles at various magnifications. The crystalline structure and phase identification were studied by XRD analysis and Raman spectroscopic measurements. The UV–Vis spectroscopy analysis was carried out to find the response of samples for ultraviolet and visible light. The current-voltage measurements have confirmed the improvement of photocurrent that is principally due to improved photo-activity of hydrogen treated TiO₂ nanoparticles. Moreover, hydrogen treated TiO₂ nanoparticles-based photoanode with the film thickness of 11.65 μm has remarkably enhanced power conversion efficiency of 6.05% in DSSCs. The ability of highly photoactive hydrogen treated TiO₂ nanoparticles will provide the new openings in different fields that include photo-electrochemical water splitting and in many other applications.