Elaboration and characterization of a refractory based on Algerian kaolin

A refractory material was elaborated from kaolin extracted from the region of Djebel Debbagh (Algeria). Kaolin grog was obtained by calcination at a temperature of 1350 °C during 1 h. It was used as aggregates with granulometric distribution composed of fine fraction (mean grain size: 100–250 μm) and coarse fraction (mean grain size: 1000–2500 μm). Crude kaolin (size < 75 μm) was also used as a binder with an amount representing 15% of the dry material. After a 9.28% moistening and a rotting of 1 day, cylindrical samples were shaped by uniaxial pressure at 80 MPa. The samples were submitted to a natural drying during 24 h, a stoving at 100 °C and a calcination at 600 °C during 1 h. They were fired at high temperatures between 1250 and 1450 °C.

An X-ray diffraction (XRD) analysis showed that the refractory samples are composed of mullite and silica. Silica is a mixture of a vitreous phase and cristobalite at 1300, 1350 and 1400 °C and becomes completely amorphous when the samples are fired at higher temperature (1450 °C). The sample porosity is about 30%. The mechanical tests carried out as a function of temperature revealed different behaviours of the material. From the ambient up to 600 °C, the refractory behaviour is pseudo-plastic caused by micro-cracking. Between 700 and 900 °C, the samples become more rigid. At 1000 °C, the material exhibits a visco-plastic behaviour. The amorphous phase governs the sample properties variation with temperature increasing. Its content varies between 28% and 34% according to the firing temperature. Thermal shock tests realized in water showed that the refractory samples present good thermal shock resistance.     

Graphene films with large domain size by a two-step chemical vapor deposition process

The fundamental properties of graphene are making it an attractive material for a wide variety of applications. Various techniques have been developed to produce graphene and recently we discovered the synthesis of large area graphene by chemical vapor deposition (CVD) of methane on Cu foils. We also showed that graphene growth on Cu is a surface-mediated process and the films were polycrystalline with domains having an area of tens of square micrometers. In this paper, we report on the effect of growth parameters such as temperature, and methane flow rate and partial pressure on the growth rate, domain size, and surface coverage of graphene as determined by Raman spectroscopy, and transmission and scanning electron microscopy. On the basis of the results, we developed a two-step CVD process to synthesize graphene films with domains having an area of hundreds of square micrometers. Scanning electron microscopy and Raman spectroscopy clearly show an increase in domain size by changing the growth parameters. Transmission electron microscopy further shows that the domains are crystallographically rotated with respect to each other with a range of angles from about 13 to nearly 30°. Electrical transport measurements performed on back-gated FETs show that overall films with larger domains tend to have higher carrier mobility up to about 16,000 cm(2) V(-1) s(-1) at room temperature.     

Initial Stage Oxidation and Surface Morphology of Modified 9Cr–1Mo Steel at High Temperatures in Air

Modified 9Cr–1Mo steel was oxidized in air at 550 and 750 °C for 25, 100, 250 and 500 h and the oxide scales formed were analysed. The surface morphology and the chemical state of the oxide scales were evaluated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The different exposure temperatures and time showed significant variations on the surface morphologies, the nature of oxide scale, and oxide constituents. The energy dispersive X-ray spectroscopic (EDS) analysis revealed the segregation of Mn at 750 °C even for short exposure time. Grazing incidence X-ray diffraction (GIXRD) patterns revealed the scales to be enriched with haematite and less intense magnetite peaks. Detailed XPS characterization indicated the presence of mixed oxides of iron (Fe), chromium (Cr) and manganese (Mn) in the oxide scales. The Fe–Cr spinel in the oxide scale offered resistance to oxidation of the steel, whereas Mn–Cr spinel was deleterious in nature as it promoted cracking and formation of blisters.     

Partial characterization, sperm association and significance of N- and O-linked glycoproteins in epididymal fluid of rhesus monkeys (Macaca mulatta)

The present study investigated regional modifications of glycosylation status, sperm association and functional significance of N- and O-linked glycoproteins in epididymal luminal fluid of the rhesus monkey (Macaca mulatta). The predominant glycoproteins of the epididymal luminal fluid that increase in the extent of glycosylation or unmasking of exposed epitopes in a region-specific, maturation-dependent manner, included those of 150, 116, 68, 64, 58 (N- and O-linked) and 170 kDa (O-linked). The higher expression of 40 (N-linked), 38 (N- and O-linked) and 60, 56 and 33 kDa (O-linked) glycoproteins in the proximal caput epididymal fluid was followed by alteration or reorganization of 60, 38 and 33 kDa (O-linked) glycoproteins in the distal segments of the epididymis. The association of epididymal fluid glycoproteins with maturing spermatozoa was identified by generating polyclonal antiserum against monkey caudal sperm membrane in female albino rabbits. The antiserum crossreacted strongly with 58 and 33 kDa epididymal fluid glycoproteins of monkeys and also reacted with 116, 68, 58, 56 and 33 kDa glycoproteins from Triton X-100 extracts of human spermatozoa, indicating the presence of antigenically related components in both species. The functional significance of epididymal fluid glycoproteins in sperm functions was investigated by raising antiserum against a heavily glycosylated 58 kDa glycoprotein (MEF1) of caudal epididymal fluid, which crossreacted with the Triton X-100 extracts of epididymal spermatozoa of monkey and ejaculated human spermatozoa on immunoblots. In an in vitro micro-sperm agglutination assay, anti-MEF1 serum agglutinated both rat caudal epididymal spermatozoa and human spermatozoa. MEF1 seemed to be involved in fertilization as demonstrated by inhibition of fertility (100%) in female albino rabbits and rats immunized with this protein. A sperm-agglutinating 58 kDa glycoprotein of rhesus monkey epididymis with functional significance in fertility was identified, thus indicating that it is a potential candidate for contraceptive vaccine development.     

Value Addition to Sulfate Waste Pickle Liquor of Steel Industry Using Hydrometallurgical Processes

The solvent extraction of concentrated acid was investigated from sulfate waste pickle liquors using Cyanex 923 (trialkylphosphine oxide (TRPO); manufactured by Cytec Industries Inc., Woodland Park, NJ; provided by Cyanamid Canada Inc. (Markham, Canada)) as an extractant. The effect of various parameters was studied such as extractant concentration, organic-to-aqueous phase ratio, temperature. and retention time on acid extraction from the waste pickle liquor to the organic phase, After the saturation of the organic phase with sulfuric acid, stripping studies were performed to back-extract the pure acid into the aqueous phase. The raffinate of the solvent extraction process that contains both ferrous and ferric iron as well as trace impurities was subjected to oxidation and hydrothermal treatment to precipitate iron with a well-defined pseudo-cubic morphology and a high coercivity value that renders it suitable for high-grade ferrite production.     

Characterization of Oxide Dispersed AlCoCrFe High Entropy Alloy Synthesized by Mechanical Alloying and Spark Plasma Sintering

The present study deals with phase evolution of oxide dispersed AlCoCrFe high entropy alloy during mechanical alloying and spark plasma sintering. Mechanical alloying of AlCoCrFe resulted in a single BCC phase. However, ordering of BCC phase with evolution of chromium carbide and sigma phase were observed after spark plasma sintering. High hardness of 1,050 ± 20 HV₁ and 1,070 ± 20 HV₁ was observed for AlCoCrFe high entropy alloy without and with oxide dispersion, respectively. Significant contribution from solid solution strengthening effect in high entropy alloys appears to have overwhelmed the effect of oxide dispersion on hardness.     

Compact inductive energy storage pulse power system

An inductive energy storage pulse power system is being developed in BARC, India. Simple, compact, and robust opening switches, capable of generating hundreds of kV, are key elements in the development of inductive energy storage pulsed power sources. It employs an inductive energy storage and opening switch power conditioning techniques with high energy density capacitors as the primary energy store. The energy stored in the capacitor bank is transferred to an air cored storage inductor in 5.5 μs through wire fuses. By optimizing the exploding wire parameters, a compact, robust, high voltage pulse power system, capable of generating reproducibly 240 kV, is developed. This paper presents the full details of the system along with the experimental data.     

A design approach for systems based on magnetic pulse compression

A design approach giving the optimum number of stages in a magnetic pulse compression circuit and gain per stage is given. The limitation on the maximum gain per stage is discussed. The total system volume minimization is done by considering the energy storage capacitor volume and magnetic core volume at each stage. At the end of this paper, the design of a magnetic pulse compression based linear induction accelerator of 200 kV, 5 kA, and 100 ns with a repetition rate of 100 Hz is discussed with its experimental results.