Stock Powder Research Articles

Formation of detonation coatings based on titanium aluminide alloys and aluminium titanate ceramic sprayed from mechanically alloyed powders Ti—Al

The phase formation of the detonation coatings from the different Ti–50Al feed stock powders were investigated. The powders were prepared by milling of TiAl (γ) ingot and mechanical alloying of the Ti and Al elementary powders. The application of the nanocomposite powder materials which were activated by the mechanical alloying made the phase formation process in the coatings more universal and adjustable due to more active and sensitive response of powder material to a gas environment. It is shown that from the mechanically alloyed powder Ti–50Al, it is possible to consolidate by the detonation spraying method the ceramic coating based on the compound Al 2TiO 5 at oxidizing influence of the working gas environment on the powder. Coating based on the titanium aluminides with inclusions TiN can be formed at nitriding influence of the working gas environment on the powder. At the use of the cast microsize powder TiAl (γ), its phase composition is inherited by the coating.

Household consumption of stock cubes and stock powder in the Vaal Triangle of SA

This is the pilot study of a larger project in which fortification was evaluated in a clinical intervention trial in the Vaal Triangle of South Africa. The main purpose is to determine the suitability of stock cubes and stock powder as possible vehicles for fortification. A questionnaire was developed to determine stock cube and stock powder consumption patterns and handed out to the 802 subjects in the randomly selected sample, after testing for reliability. The results showed that 97 per cent of respondents (n=802) used stock cubes or powder daily in cooking, mainly stews, with the total consumption being 26 per cent chicken, 24 per cent beef, 15 per cent oxtail, 12 per cent mutton, 12 per cent tomato and 11 per cent vegetable. Stock cubes (79 per cent) were more popular than stock powder (21 per cent). From a consumption point of view, compared with other staple foods such as wheat flour, sugar and maize meal, stock cubes and/or stock powder are consumed on a daily basis by 97 per cent respondents and might thus be suitable vehicles for delivering micronutrients to many population groups without major changes in food production or changes in customary diets.

Part I: characterization of Cr 3C 2-25% NiCr reactive plasma sprayed coatings produced at different pressures

The present work was performed with the aim of characterizing various plasma sprayed Cr 3C 2–NiCr coatings produced by using different processing pressures between 300 and 1200 mbars, in a nitrogen controlled atmosphere CAPS system. X-Ray diffraction was carried out on all coatings by using Bragg–Brentano geometry. The phases identified in the as-supplied powder Cr 3C 2/Ni–Cr were fcc Ni–Cr and orthorhombic Cr 3C 2. In contrast to the original powder, the coatings showed evidence of Cr 3C 2, Ni–Cr and either Cr 6.2C 3.5N 0.3 or Cr 3C 1.52N 0.48 carbo-nitride phases depending on the ratio of C/N in the coating. The presence of Cr 7C 3 and CrO 2 was also identified in the coatings deposited at atmospheric pressure. The volume fraction of carbide plus nitride phase in the coating was always less than the volume fractions of the carbide phase in the original feed stock powder. The volume fraction of carbide plus nitride phase was found to depend quite markedly on the spraying parameters such as pressure, power input, spraying distance and substrate cooling. The results have been presented in terms of spraying efficiency, ξ. The highest value of ξ (86.4%) was obtained for coatings produced at 1200 mbar pressure, a spraying distance of 120 mm, without N 2 cooling and the lowest value (25.2%) was found for the coatings deposited at 300 mbar for the same spraying distance but with N 2 cooling. The presence of graphitic carbon was detected in all samples especially for specimens where the fraction of carbide plus carbo-nitride phases was the greatest. The influence of spraying parameters such as pressure, power input, spraying distance and substrate cooling on the microstructure was determined. The highest microhardness value of 2296 HV 50 was found for the carbide plus carbo-nitride phase contained in the specimens produced at 1200 mbar spraying pressure, 120-mm spraying distance and substrate heating at 600°C.

Powder Preparation and Sintering Characteristics of Rare‐Earth Sesquisulfide Ceramics

Dense ceramics were prepared from rare‐earth sesquisulfides. Extremely fine‐grained precursor oxides were synthesized by evaporative decomposition of solutions. The sesquisulfides were synthesized by direct reaction of the oxides with flowing H2S in the presence of graphite. These reactive, fine‐grained, EDS‐derived sulfides could be sintered into ceramic compacts that achieved 92–98% of theoretical density. In comparison, the same processing conditions with 25–50 m stock powder produced ceramics with only 70–80% of theoretical density.

Studies on Atherosclerosis : II. Clinical Investigation on Lipid Mobilizer

The author reported in the preceding paper (Studies on Atherosclerosis : Part 1) that the combined administration of lanolin and lipid mobilizer induces marked lipemia as well as atherosclerosis in the rabbits. Studies on lipid mobilizer (LM) in man have been reported by clinical findings with the quantitative changes of LM. The author attempted to measure the amount of LM in the human blood serum and to clearify its part in the development of atherosclerosis. Material and Methods 1) In vitro measurement of LM. LM was obtained and purified after Seifter's method from 2ml of the blood serum obtained from the hungry patients in the early morning. The amount of serum LM was evaluated according to its character to inhibit the activity of lipoprotein lipase. 0.3ml of lipoprotein lipase solution was added with 0.3ml of 10% human albumin solution (pH 8.5), 0.3ml of lipid mobilizer solution and 4.0ml of diluted cow's milk (1 in 600, dilutant : 0.25M NH3-NH4Cl, pH 3.5 diluted three times with saline), and incubated at 37°C for two hours. After the procedure the turbidity was compared. 2) Purification of lipoprotein lipase. Periepididymal and perirenal adipose tissue of male rats were put in the cold acetone (O°C, 30 times as much as the tissue), and homogenized at O°C, and then centrifuged in 6000 rpm for 20 minutes. The supernate was discarded. The precipitate was repeatedly washed in cold acetone and ether, and then dried under the decreased pressure in low temperature. This stock powder was dissolved in 0.025M NH3NH4Cl buffer solution (pH 8.6) at O°C and left for 60 minutes, and centrifuged in 8000 rpm for 30 minutes, and then the supernate was diluted in a proper way every time for use. 3) Preparation of anti-β-lipoprotein. Human blood serum containing a large amount of β-lipoprotein was added with 20 times as much volume of 4mg/dl dextran sulfate in physiological saline solution containing sodium citrate. 15-60 minutes later, this mixture was centrifuged in 6000 rpm for 30 minutes. The supernate was discarded. The same procedure was repeated 5 or 6 times to get the pure β-lipoprotein. 15-20 mg dose of this preparation was injected in to the rabbit subcutaneously 15 times. After the procedure, anti-β-lipoprotein-seurm was obtained. This serum reacted specifically with β-lipoprotein to form a single precipitation zone in agar gel double diffusion method (after Ouchterlony). 4) Patients with coronary disease, hypertension and cerebrovascular disease were subjected to this experiment. Healthy adult persons were examined as the control.