Investigation of Properties and Wear Behavior of HVOF Sprayed TiC-Strengthened Fe Coatings

High-velocity oxyfuel (HVOF) sprayed carbide based coatings (such as Cr₃C₂/NiCr) are industrially well established for wear protection applications. Due to their high carbide content of typically 75 wt.% and more, they provide very high hardness and excellent wear resistance. Unfortunately, costs for matrix materials such as nickel underlie strong fluctuations and are normally well above the prices for iron. Therefore an alternative concept to conventional carbides is based on TiC-strengthened low-cost Fe-base materials, which are already used for sintering processes. Depending on the carbon content, the Fe-base material can additionally offer a temperable matrix for enhanced wear behavior. The sprayability of TiC-strengthened Fe-powders with a gaseous and a liquid fuel driven HVOF system was investigated in this study. The resulting coatings were analyzed with respect to microstructure, hardness, and phase composition and compared with galvanic hard chrome, NiCrBSi, and Cr₃C₂/NiCr (80/20) coatings as well as with sintered Fe/TiC reference materials. Furthermore, the Fe/TiC coatings were heat treated to proof the retained temperability of the Fe matrix after thermal spray process. Tribometer tests (pin-on-disk tests) were conducted to determine wear properties.     

Characteristics of Mango Kernel Fats Extracted from 11 China-Specific Varieties and Their Typically Fractionated Fractions

11 China‐specific mango varieties, i.e., Tainong, Xiangya, Okrong, Keitt, Chiin Hwang, Guifei, Yuexi, Biantao, Guixiang, Zihua and Guire, were selected from South China, and the kernels were separated from pulps and then dried to extract mango kernel fats (MKF). 5.65–11.14 % of the fats could be obtained from dried kernels using hexane extraction, and their iodine values, slip melting points, triacylglycerols, sn‐2 fatty acids and micronutrients were analyzed. MKF were comprised predominantly of triacylglycerols reaching 85.09–92.72, and 78.28–84.37 % of oleic at the sn‐2 position. 29.99–55.44 % of SOS, 11.17–23.34 % of SOO and 13.10–19.79 % of POS occupied the main percentages of triacylglycerols, indicating MKF have diversified application after fractionation. Certain variety characterized as moderate values mentioned above, therefore, was selected and then fractionated by two‐stage processes to produce typical MKF fractions. The stearin (Fraction‐II) fractionated from the first solid fraction (Fraction‐I) with 68.09 % of SOS and 15.43 % of POS was more suitable as cocoa butter improver, while the olein (Fraction‐III) produced from the first liquid fraction was rich in SOO (45.59 %), POO (11.37 %) and OOO (11.14 %), which are considered as ideal cooking oil or frying fat ingredients. In addition, high amounts of micronutrients, including sterol, tocopherol and squalene, were also found in MKF ranged from 3837 to 7085, 81 to 916, and 164 to 941 mg/kg among different varieties, respectively. In particular, squalene levels were higher compared with most of other vegetable oils.     

Production of High-Melting Symmetrical Monounsaturated Triacylglycerol-Rich Fats from Mango Kernel Fat by Acetone Fractionation

1,3‐Distearoyl‐2‐oleoyl‐glycerol, 1‐palmitoyl‐2‐oleoyl‐3‐stearoyl‐glycerol and 1‐stearoyl‐2‐oleoyl‐3‐arachidoyl‐glycerol are typical high‐melting symmetrical monounsaturated triacylglycerols (Hm‐SMT) found in cocoa butter improver (CBI). These triacylglycerols help to increase the hardness of chocolate products in tropical climates. In the present study, natural CBI products were produced from mango (Mangifera indica, Linn) kernel fat (MKF) by selective three‐stage fractionation using acetone. The second stearin (fraction I) from the first precipitate of MKF by fractionation for 180 min at 15 °C contained 86.9% of Hm‐SMT, and the third stearin (fraction II) obtained from fraction I by further fractionation for 180 min at 18 °C was enriched with 94.4% Hm‐SMT. High percentages of such triacylglycerols in these products contributed to higher slip melting points (36.5–37.7 °C) than commercial cocoa butter and cocoa butter equivalent (26.7 and 27.9 °C). Also, their differential scanning calorimetry properties and solid fat content values were superior to those in traditional confectionery fats, indicating that the tailored stearins could be used as ideal CBI. In particular, the hard fat blends consisting of 55–70% cocoa butter (CB) and 30–45% fraction II were considered as the preferred heat‐resistant chocolate ingredients. In addition, the mixture of the oleins (fraction III) was rich in diunsaturated and triunsaturated triacylglycerols and showed similar thermal properties to super palm oil, thus making it more suitable as special fat ingredients and modified fat sources.     

Etude de l'élimination des ions Cu (II) de la solution aqueuse par sorption sur la zéolithe a study of the removal of Cu (II) from aqueous solution by sorption on Zeolite A

The objective of this study is to present the results of removal of copper by the method of sorption on zeolite A. The batch experiments were conducted for both the kinetics for the sorption isotherms. The experimental variables studied were pH, contact time at different initial concentrations, the amount of sorbent, temperature and stirring speed. The sorption capacity depends on the pH and mass of sorbent, but the temperature and stirring rate showed no influence. Several mechanisms of retention of copper on the zeolite could be competitive (ion exchange, complexation or precipitation and sorption). The modeling of experimental data on kinetics showed that the model of pseudo‐second order describes satisfactorily the sorption on the zeolite, and that the limiting step of the speed distribution intraparticle. Statistical analysis of the constants for Langmuir‐Freundlich equation has shown that this model seems most appropriate to describe this phenomenon of sorption, which indicates the heterogeneity of the surface sorption of the zeolite. Copyright © 2011 Canadian Society for Chemical Engineering     

Improving long term oxidation protection for γ‐TiAl substrates

In previous work, a thermal spray multilayer system consisting of Zirconia (ZrO₂) and MCrAlY top coat showed promising results regarding the oxidation behavior of the Gamma Titanium Aluminides substrates tested, which encouraged further research activities. Diffusion of substrate material was successfully inhibited by a ceramic Zirconia coating. A building up of a dense and stable oxide layer could be achieved by additional application of an MCrAlY top coat, leading to improved oxidation resistance and thus showing feasibility. In this work the main focus for development was put on enhancing adhesion and lowering residual stresses of the coatings in order to allow long term and cyclic testing without delamination taking place. Being a very brittle material, Gamma Titanium Aluminides require special surface treatment to enable roughening which is crucial for a strong mechanical bond between substrate and coating. Alternatives to conventional grit blasting as a standard preparation method were investigated. These were micro‐abrasive blasting and blasting at elevated temperature (≈300–550°C) to allow a more ductile behavior. The paper will highlight the implications by means of these measures and will also show the present development status of the multilayer system.     

Breast cancer screening and related attitudes among Filipino-American women

This study assessed mammography screening rates and related attitudes and intervention preferences in Filipino-American women, a group that has been neglected in cancer control research. Face-to-face interviews were conducted in English and Tagalog with a convenience sample of 218 Filipino women 50 years and older residing in Los Angeles. Sixty-six % had ever had a screening mammogram, 42% had had one in the past 12 months, and 54% in the past 2 years. These rates are about 20% lower than those found among African-American and white women in the 1994 California Behavioral Risk Factor Survey. Women who had received a doctor's recommendation to obtain a mammogram, women stating that they were very likely to obtain a mammogram if a physician recommended it, and women who felt very comfortable requesting a mammogram from a physician were more likely to have been screened. Women who had friends and relatives who had obtained mammograms those stating that their friends and relatives would be very supportive of their getting a mammogram, and those who felt that it was very worthwhile to obtain a mammogram were also more likely to have been screened. The following variables were negatively related to the outcome: concern over cost, the attitude that mammograms are only needed in the presence of symptoms, perceived inconvenience of taking the time and difficulties getting to the mammography facility, and embarrassment. Implications for interventions to increase breast cancer screening are discussed.     

A traditional Sudanese fermented camel's milk product, Gariss, as a habitat of Streptococcus infantarius subsp. infantarius

Samples of the traditional Sudanese fermented camel's milk product Gariss representing 9 different regions in Sudan were microbiologically characterized using an integrated approach including phenotypic and genotypic methods. Lactic acid bacteria [log(CFU/g)=7.76-8.66] and yeasts [log(CFU/g)=6.05-7.79] were detected in high numbers. A total of 180 LAB isolates were identified of which 123 isolates were found to belong to the Streptococcus bovis group. Thirteen representative isolates were characterized by PCR amplification and sequencing of the housekeeping genes rpoB and sodA and the streptococcal glucosyltransferase gene (gtf). All thirteen isolates were identified as Streptococcus infantarius subsp. infantarius, a potential human pathogen. The gene encoding the virulence determinant gtf was detected in 10 of the 13 tested strains. The same isolates were able to survive exposure to 0.3% (w/v) oxgall for 4 h and pH=2.7 for 1-4 h. Also Lactobacillus fermentum were detected in high numbers, whereas Enterococcus faecium and Lactobacillus helveticus were detected more occasionally. The yeast microflora in all Gariss samples consisted of Kluyveromyces marxianus and Issatchenkia orientalis with the former being predominant in 7 out of 9 samples.     

Dynamic strain aging during creep of α-Zr

In the temperature range 723 to 823 K (450° to 550°C) annealed, crystal bar α-Zr exhibits anomalous behavior with respect to both single stress and incrementally stressed creep tests. The nature and extent of the anomalous behavior depends on temperature, stress, and impurity content. Specimens with low oxygen content exhibit: 1) normal, three-stage creep behavior during single stress tests, and 2) normal transients during incremental stress and temperature tests. Specimens with higher oxygen contents exhibit: 1) multi-stage creep curves whose shapes depend on temperature and stress, 2) inverse transients following stress and temperature increments, and 3) peaks in activation energy-tempera-ture curves. The nature of the anomalous behavior is consistent with a model for strain aging in which the possibility of localized depletion of the strain aging species exists. In the material being studied oxygen is probably responsible for the observed effects. R. D. WARDA, formerly of Department of Metallurgy, University of British Columbia