Wear resistance of a Cr3C2-NiCr detonation spray coating

Coatings can be applied to surfaces to improve the surface characteristics over those of the bulk properties and are widely used in tribological applications either to reduce wear and/or to modify friction during contact. One of the foremost coating methods for combating wear is thermal spraying. To prolong the life of steel slab continuous casting rolls, Cr₃C₂-NiCr detonation spray coating was processed on the roll surface in a steelmaking plant in China. This article studies the mechanical properties and wear resistance of this coating. The abrasive and dry frictional wear testing were performed using a pin-on-disk tester. Experimental results show that the wear resistance of the coated samples, i.e., coating reduces the risk of seizure compared to uncoated samples, is much better than those of the uncoated steel at room and elevated temperatures with any load and sliding velocity. The coating wear mechanisms under different test conditions are discussed.     

The effects of the microstructural characteristics of Fe–0.33C–1.2Mn–xNb–xMo steels on hydrogen embrittlement fracture

International Journal of Fracture - The hydrogen embrittlement (HE) characteristics of Fe–0.33C–1.2Mn–xNb–xMo steels were investigated experimentally using various samples...     

Approaching Trap-Minimized Polymer Thin-Film Transistors

Semiconducting π-conjugated polymers are the most promising candidates for flexible electronics owing to their facile processability and mechanical robustness; however, achieving steep and stable switching operations in polymer thin-film transistors (TFTs) remains a serious challenge. Herein, it is shown that whole optimizations for eliminating interfacial carrier traps throughout the conductive path are necessary in achieving TFTs showing both exceptionally sharp switching and bias-stress-free characteristics. Inverted-coplanar-type TFTs composed of a highly lyophobic amorphous perfluoropolymer gate–dielectric interfaced with a push-coated semiconducting polymer layer are manufactured. The use of the dielectric allows the establishment of bias-stress-free characteristics with minimized contact resistance. Additionally, fairly sharp on/off switching TFTs with the smallest normalized subthreshold swing can be obtained by utilizing a particular donor–acceptor copolymer that involves a self-passivation mechanism working to achieve a trap-minimized interface. These findings have opened a way for low-power and robust device operations in polymer-based flexible electronics.     

Rapid discharge performance of composite electrode of hydrated sodium manganese oxide and acetylene black

Hydrated sodium manganese oxide was synthesized by reducing permanganate ion using ethanol by a sol–gel method. By including acetylene black in the synthetic reaction, we obtained composite materials in which sodium manganese oxide hydrate particles were small and mixed well with the acetylene black. We evaluated those composites as a lithium battery cathode and found that they showed 170 mA h g⁻¹ under 5 mA g⁻¹ and 117 mA h g⁻¹ under 5 A g⁻¹ on the basis of composite weight. This rapid discharge performance was probably caused by the favorable contact condition of the composite constituents.     

Photo-thermally cured eugenol-derived epoxy resins by simultaneous thiol-ene/thiol-epoxy/thiol-maleimide triple “click” reactions

Polyglycidyl ether of eugenol novolac (PGEEGN) was synthesized by the glycidylation reaction of eugenol novolac (EGN) with an average degree of polymerization of ca. 3. A mixture of PGEEGN and a pentaerythritol-based tetrathiol (S4P) was photo-polymerized at room temperature and subsequently thermally cured at 100–150 °C to produce a two-component cured product (PGEEGN-S4P). A similar curing reaction of glycidyl ether of eugenol (GEEG) and S4P produced another two-component cured product (GEEG-S4P). Furthermore, a mixture of PGEEGN, S4P and 4,4′-bismaleimidodiphenylmethane (BMI) was photo-polymerized at room temperature and subsequently thermally cured at 100–230 °C to produce a three-component cured product (PGEEGN-S4P-BMI). The FT-IR spectral analysis revealed that the thiol-ene and thiol-epoxy reactions progressed for GEEG-S4P and PGEEGN-S4P, and the thiol-ene, thiol-epoxy and thiol-maleimide reactions progressed for PGEEGN-S4P-BMI. The 5% weight loss temperatures of PGEEGN-S4P and PGEEGN-S4P-BMI were higher than that of GEEG-S4P. A higher order of T_g, tensile strength and modulus was PGEEGN-S4P-BMI?>?PGEEGN-S4P?>?GEEG-S4P. The oligomerization of eugenol units and incorporation of BMI were effective to improve thermal and mechanical properties of the GEEG/S4P curing system.     

Generation of hydroxyapatite patterns by electrophoretic deposition

Hydroxyapatite (HAp) patterns with distinct boundaries were generated by electrophoretic deposition (EPD) utilizing an insulating mask that partially blocks the electric field. For the EPD process, we selected two types of mask: a polytetrafluoroethylene (PTFE) board with holes and a resist pattern. A porous PTFE film, which differed from the mask PTFE, was employed as a substrate and attached to the mask. EPD was performed with a suspension of wollastonite particles in acetone, which were deposited on the substrate in the form of the patterned mask. The deposited wollastonite particles induced HAp patterns during a soak in simulated body fluid (SBF). As a result, minute HAp patterns, such as dots, lines, and corners were fabricated on the porous PTFE substrate with a minimum line width of about 100 μm.     

Nanostructure of pure iron anodically oxidized in borate buffer solution and annealed by infrared radiation

The behavior of oxide film on pure iron passivated in a borate buffer solution and subsequently radiated by infrared light (IR) was investigated in comparing to that by just IR annealing without passivation, and was evaluated by film structure, etc. The effect of thermal annealing over 250 degrees C was observed with gamma-Fe2O3 grain growth and sharp increase in surface roughness, film thickness and oxygen content. An ellipsometric parameter of tan psi was sensitively reflected by annealing effect, and tan psi curve had a shoulder at 150 degrees C for 5 min and a peak of tan psi was shifted from 350 nm to 450 nm in wavelength. This shift was also caused by the formation of gamma-Fe2O3, because the peak was also observed in tan psi of the bulk Fe2O3 family. Passivation effects at 800 mV prior to IR annealing on thickness and oxygen content changed at 150 degrees C, and decreased tan psi at 350 nm and excessive film growth over 250 degrees C, and increased oxygen content under 100 degrees C and surface roughness at 50-250 degrees C. The terrace width with atomic scale flatness was slightly increase by passivation prior to IR annealing at 50-250 degrees C, and the maximum terrace width reached larger than 10 nm by passivation and IR annealing at 100 degrees C for 30 min.     

Random exchanges of non-conserved amino acid residues among four parental termite cellulases by family shuffling improved thermostability

There have been two major problems preventing applications of termite cellulases; one was difficulty for their hetelologous overexpression, and another is their low thermostability. We previously achieved adaptation of termite cellulase genes to an overexpression system of Escherichia coli by family shuffling of four orthologous cDNAs (Biosci. Biotechnol. Biochem., 2005; 69: 1711-1720). Using the adapted mutant cDNAs as parental genes combined with native-form cDNAs, we performed further family shuffling and obtained mutant cDNAs, which gave enzymes with improved thermostability. The best-evolved clone (PA68) was improved by 10 degrees C in maximum stability (retaining 90% original activity for 30 min incubation) from the parental enzymes, and kept 54% of its original activity for 150 min at 50 degrees C, whereas the most thermostable enzyme amongst the parents (A18) retained 30% of its original activity. PA68 showed 889 (micromoles of reducing sugars/min/mg of protein) in V(max) and 560 (micromoles of reducing sugars/min/mg of protein) in the specific activity against carboxymethylcellulose, which corresponds to 9.8 and 13.1 times of those of one of the ancestral enzymes rRsEG. In summary, we improved thermostability of the termite cellulase and increased the V(max) value and specific activity by combining only cDNAs encoding enzymes adapted for normal temperatures.     

Four-point probe resistance measurements using PtIr-coated carbon nanotube tips

We performed four-terminal conductivity measurements on a CoSi2 nanowire (NW) at room temperature by using PtIr-coated carbon nanotube (CNT) tips in a four-tip scanning tunneling microscope. The physical stability and high aspect ratio of the CNT tips made it possible to reduce the probe spacing down to ca. 30 nm. The probe-spacing dependence of resistance showed diffusive transport even at 30 nm and no current leakage to the Si substrate.     

Inhibitory mechanisms of glycoprotein fraction derived from Miscanthus sinensis for the immediate phase response of an IgE-mediated cutaneous reaction

OBJECTIVE: To determine the risk factors for colonization or infection with methicillin-resistant Staphylococcus aureus in human immunodeficiency virus (HIV)-infected patients. DESIGN: Retrospective matched-pair case-control study. SETTING: Continuity clinic and inpatient HIV service of a university medical center. POPULATION: Patients with HIV infection from the general population of eastern and coastal Texas and from the Texas Department of Criminal Justice. DATA COLLECTION: Patient charts and the AIDS Care and Clinical Research Program Database were reviewed for the following: age, race, number of admissions, total hospital days, presence of a central venous catheter, serum albumin, total white blood cell count and absolute neutrophil count, invasive or surgical procedures, any cultures positive for S. aureus, and a history of opportunistic illnesses, diabetes, or dermatologic diagnoses. Data also were collected on the administration of antibiotics, antiretroviral therapy, steroids, cancer chemotherapy, and subcutaneous medications. RESULTS: In the univariate analysis, the presence of a central venous catheter, an underlying dermatologic disease, lower serum albumin, prior steroid therapy, and prior antibiotic therapy, particularly antistaphylococcal therapy or multiple courses of antibiotics, were associated with increased risk for colonization or infection with methicillin-resistant S. aureus. Multivariate analysis yielded a model that included presence of a central venous catheter, underlying dermatologic disease, broad-spectrum antibiotic exposure, and number of hospital days as independent risk factors for colonization or infection with methicillin-resistant S. aureus. CONCLUSIONS: In our HIV-infected patient population, prior hospitalization, exposure to broad-spectrum antibiotics, presence of a central venous catheter, and dermatologic disease were risk factors for acquisition of methicillin-resistant S. aureus.