Interlaboratory proficiency testing: Intercomparison in relation to the measurement of alumina,iron(III) oxide and Titania present in homogenised china clay

For establishing technical competence in testing and calibration, a laboratory has to participate in proficiency testing (PT) program from time to time. An intercomparison in the field of chemical analysis using classical and instrumental methods of analysis has been carried out by 17 accredited as well as non accredited laboratories in India as per requirement of National Accreditation Board for Testing and Calibration Laboratories(NABL), New Delhi. Central Glass and Ceramic Research Institute(CGCRI), Kolkata acted as a nodal laboratory and conducted this PT programme during 2000–2001. This paper reports the analytical results and statistical evaluation of the results using Z-score.     

Atomistic and electrical simulations of a GaN-AlN-(4H)SiC heterostructure optically-triggered vertical power semiconductor device

In this paper, a comprehensive simulation study is conducted to investigate the switching characteristics, gain, and breakdown voltage of a GaN-AlN-(4H)SiC based optically-triggered (OT) heterostructure vertical power semiconductor device (PSD). It comprises a 1 nm AlN buffer layer between the GaN and SiC heterointerface to achieve a reasonable compromise between lattice mismatch and lower forward drop. The results are compared with an all-(4H)SiC OT PSD. The all-(4H)SiC homostructure PSD is based completely on SiC and has no buffer layer. Further, it has the same structure, dimensions, and doping densities as that of the GaN-AlN-(4H)SiC based heterostructure PSD. While there have been studies on GaN-AlN-SiC lateral heterostructures, their primary focus has been on lateral conduction in the GaN structure with a thick (typically >300 nm) AlN buffer layer residing on top of a SiC substrate. Such an approach will not be useful for our vertical PSD because of the thick AlN layer. As such, first, a scaled molecular dynamics simulation (MDS) is carried out in DMol³ emulating the GaN-AlN-(4H)SiC heterointerface pn junction of the vertical PSD (with 1 nm AlN buffer) to assess the possibility of vertical conduction and stability of the heterointerface by calculating the density of states (DOS) at the Fermi level and the potential energy, respectively. Subsequently, detailed electrical simulations of the GaN-AlN-(4H)SiC and all-(4H)SiC vertical PSDs are carried out in Silvaco to assess their switching performances, gain, on-state drop, and blocking capabilities. The overall results indicate that, the GaN-AlN-(4H)SiC vertical PSD provides superior switching performance and optical absorption compared to the all-(4H)SiC vertical PSD, while the latter provides better gain. The blocking capabilities and forward drops are found to be comparable for both the PSDs from a practical standpoint.     

Numerical investigation of wall heat conduction effects on catalytic combustion in split and continuous monolith tubes

The optimum length of a monolith tube is one for which near-hundred percent conversion is attained, and at the same time, the catalyst over the entire length of the tube is utilized. In practice, the length is adjusted by stacking monolith plugs end-to-end. In this study, the repercussions of such a practice are investigated numerically with the goal to determine if a tube of length 2L demonstrates the same behavior as two tubes of length L each, stacked end-to-end. Catalytic combustion of methane–air mixture on a platinum catalyst is considered. The studies are conducted using a multi-step reaction mechanism involving 24 surface reactions between 19 species. Two different materials are considered for the walls of the monolith tube, namely silicon carbide and cordierite. Both steady state and transient simulations are performed. Results indicate that the ignition and blowout limits can be significantly different between split and continuous tubes when the wall is made up of a high thermal conductivity material, such as silicon carbide. For steady state combustion, for both wall materials, the point of attachment of the flame to the wall is altered by splitting the tube—the effect being more pronounced for silicon carbide and at relatively high Reynolds numbers. These results imply that axial heat conduction, or lack thereof due to thermal contact resistance, through the walls of the monolith results in thermal non-equilibrium between the solid and fluid phase, and subsequently affects ignition and flame stability in catalytic combustion.     

E-SPART Analyzer for Mars Mission: A New Approach in Signal Processing and Sampling

This paper introduces a novel electrical single particle aerodynamic relaxation time (E-SPART) analyzer for dust particle analysis in the Mars mission. The new E-SPART analyzer is based on a stationary-fringe laser Doppler velocimeter that can simplify the system hardware and reduce its physical size and weight. This paper presents the new operational principle and the signal processing methods. The requirement of the size of sensing volume is discussed by considering pedestal removal and the required time duration of a Doppler signal burst. Experimental results are given to confirm the effectiveness of the principle.     

Characterization of a continuous CO<Subscript>2</Subscript> laser-welded Fe-Cu dissimilar couple

Continuous CO₂ laser welding of an Fe-Cu dissimilar couple in a butt-weld geometry at different process conditions is studied. The process conditions are varied to identify and characterize the microstructural features that are independent of the welding mode. The study presents a characterization of the microstructure and mechanical properties of the welds. Detailed microstructural analysis of the weld/base-metal interface shows features that are different on the two sides of the weld. The iron side can grow into the weld with a local change in length scale, whereas the interface on the copper side indicates a barrier to growth. The interface is jagged, and a banded microstructure consisting of iron-rich layers could be observed next to the weld/Cu interface. The observations suggest that solidification initiates inside the melt, where iron and copper are mixed due to convective flow. The transmission electron microscopy (TEM) of the weld region also indicates the occasional presence of droplets of iron and copper. The microstructural observations are rationalized using arguments drawn from a thermodynamic analysis of the Fe-Cu system.     

28—A STUDY OF THE OMISSION OF THE FIRST DRAWING PASSAGE IN JUTE-PROCESSING

The jute section of the textile industry normally uses three drawing passages for the production of hessian-type yarns. The work reported in this paper shows that the first drawing passage can be eliminated if adequate care is taken at the carding stages to produce sliver of good regularity, composed of longer and finer filaments. A device developed for producing thinner slivers to suit the second drawing frame without reducing the normal production of the finisher card is described.     

Assessment of molecular events during in vitro re-epithelialization under honey-alginate matrix ambience

Re-epithelialization is one of the most important stages of cutaneous regeneration and its success requires supportive micro-ambience which may be provided with suitable bio-matrix. Biocompatibility and efficacy of such bio-matrix in re-epithelialization could be explored by multimodal analysis of structural and functional attributes of in vitro wound healing model including evaluation of prime molecular expressions of the epithelial cells during repair. Present study examines the influence of honey-alginate and alginate matrices on re-epithelialization in keratinocyte (HaCaT) population in a 2-D wound model. Cellular viability, proliferation and cell–cell adhesion status were assessed during wound closure using live/dead cell assay and by evaluating expressions of Ki67, p63 and E-cadherin along-with % change in cellular electrical impedance. Efficacy of honey-alginate matrix in comparison to only alginate one was demonstrated by a quicker reduction in wound gap, improved cellular viability, enhanced expressions of Ki67, p63 and its isoforms (TAp63, ΔNp63) as well as E-cadherin. Faster restoration of electrical attribute (% of impedance change) after wounding also indicated better impact of honey-alginate matrix in re-epithelialization.     

Measurement of Surface Topography,Packing Density,and Surface Charge Distribution of an Electrostatically Deposited Powder Layer by Image Analysis of Fluorescent Latex Spheres

A novel method of nonintrusive measurement of surface profile, packing density, and surface charge distributions of a powder layer deposited on a substrate is reported. The method employs the deposition of electrostatically charged monodispersed fluorescent latex spheres (FLS), approximately 2 m in diameter, on the surface of: (1) the substrate before deposition, (2) the powder layer after deposition, and (3) the film formed by curing the powder layer. The surface topography in all cases was mapped using an epi-fluorescent microscope with a vertical resolution of - 2 m in the z axis and - 10 m in the x and y axes. An area of 1 cm 2 1 cm is scanned in 1 mm segments, providing approximately 100 data points per cm 2 for the surface topography. For each measurement of surface topography, the substrate was positioned on the microscope stage in a manner such that the reference points (x, y, and z) remained the same for all measurements of the substrate. The surface profiles, with respect to the same reference points, were plotted using Origin 6.0 software for 3D presentation of the topography. The method was also applied to map the surface charge density distribution of electrostatically charged surfaces. The FLS imaging method provides a new tool for examination of surface profiles, packing density, and charge distribution of powder layers on a microscopic scale not provided by optical or atomic force/electrostatic force microscopy (AFM/EFM). While AFM and EFM are very effective in providing similar information with nanometer resolution, they cannot be directly applied on a larger macroscopic scale to study powder layers and for a larger surface area (up to 1 cm 2 or greater) involving deposited particles in the range of 1-50 m in diameter. For AFM, the range in the z-axis is limited to - 3 m and the x-y scan area is limited to 100 m 2 100 m. The FLS method has a much wider range but it is operated manually; an automated scanning process is required for rapid measurement. A comparison of the FLS and EFM techniques as they apply to analyzing charge distribution on coal surfaces is presented.     

Layered silicate-polymer nanocomposite coatings via radiation curing process for flame retardant applications

Polymer-clay nanocomposite (PCN) films were fabricated by uniformly dispersing organically modified montmorillonite clay (Cloisite 20A and 30B) in varying concentrations of 2%, 5%, 10% and 15% (w/w) in an optimized composition of aliphatic urethane acrylate (AUA)–Trimethylolpropane triacrylate (TMPTA) mixture by ultra-sonication followed by ⁶⁰Co-gamma radiation induced curing. Radiation doses were optimized to obtain non-tacky, homogeneous thin films, which were subsequently characterized by UV–vis spectrophotometry, X-ray diffraction (XRD), small angle X-ray scattering (SAXS), Fourier transform infrared spectrometry (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. Gloss of the PCN films decreased, and fracture toughness and hardness of PCN films improved with the incorporation of the clay in the PCN coatings. Limiting Oxygen Indices (LOIs) of the samples were calculated from the thermogravimetric analyses data to ascertain the efficacy of the PCN films as potential flame retardant materials.     

Synthesis of methyl boron nitride film as low-k insulating film for LSI interconnection

Low dielectric constant (k) materials for the ULSI interconnect insulator are required to meet the fast development of high-speed devices. We have investigated low-k material of boron nitride containing methyl (methyl boron nitride) by using tris-di-methyl-amino-boron (TMAB) gas. The dielectric constant (k) of the film decreases with decreasing RF plasma power and the k value of the methyl BN film can be achieved as low as 1.8 at 10 W RF plasma power.Absorption band of the film was observed at 2960 cm^? 1 due to unsymmetrical stretching mode of C–H in CH₃. It is thought that increasing C–H bond with low polarizability and reducing CN bond with high polarizability can realize a lower k value. The film has also high resistivity of more than 1 × 10⁹ Ω cm and sufficient Young modulus of more than 26 GPa for the interlayer of LSI interconnection. There is a possibility that the dielectric constant can be decreased keeping the BN structure with high strength. The methyl BN film is an extremely attractive material as low-k material of next generation devices.