Some properties of silica-supported nickel catalysts

A literature survey has been made of earlier work on factors which have been found to influence the catalytic activity of supported metal catalysts. In particular an interaction has been shown to exist between the metal and its support in these catalysts. Two of the important factors which were shown to affect activity are the average metal crystallite size and the fraction of the metal present in a non-metallic form (for example as metal ions) in the catalyst. The earlier work consists almost exclusively of kinetic studies of heterogeneously catalyzed reactions. It is suggested that the conclusions are of a limited value owing to the widespread existence of the compensation effect, the fact that different test reactions may give contrasting results as to the relative activities of a series of catalysts and the belief that only a small fraction of the surface sites of a catalyst is generally involved in a given heterogeneous reaction. The work described in this thesis consists of an investigation of the effects of various factors on the isosteric heat of adsorption of an adsorbate per unit metal area on supported metal catalysts. The heat of adsorption per unit metal area provides a measure of the strength of the bond between the adsorbate and the surface atoms of the adsorbent. It was felt that this approach would give further insight into the factors affecting catalytic activity because the disadvantages, mentioned above, of kinetic studies would be eliminated

Production of Ultrafine, High-purity Ceramic Powders Using the US Bureau of Mines Developed Turbomill

Turbomilling, an innovative grinding technology developed by the U.S. Bureau of Mines in the early 1960's for delaminating filler-grade kaolinitic clays, has been expanded into the areas of particle size reduction, material mixing, and process reaction kinetics. The turbomill, originally called an attrition grinder, has been used for particle size reduction of many minerals, including natural and synthetic mica, pyrophyllite, talc, and marble. In recent years, an all-polymer version of the turbomill has been used to produce ultrafine, high-purity, advanced ceramic powders such as SiC, Si3N4, TiB2, and ZrO2. In addition to particle size reduction, the turbomill has been used to produce intimate mixtures of high surface area powders and whiskers. Raw materials, TiN, AlN, and Al2O3, used to produce a titanium nitride/aluminum oxynitride (TiN/AlON) composite, were mixed in the turbomill, resulting in strength increases over samples prepared by dry ball milling. Using the turbomill as a leach vessel, it was found that 90.4 pct of the copper was extracted from the chalcopyrite during a 4-hour leach test in ferric sulfate versus conventional processing which involves either roasting of the ore for Cu recovery or leaching of the ore for several days

Technical Advance: caspase‐1 activation and IL‐1β release correlate with the degree of lysosome damage, as illustrated by a novel imaging method to quantify phagolysosome damage

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142182/1/jlb0813.pd

A Study On Ultra Fine Grinding Of Silica And Talc In Opposed Fluidized Bed Jet Mill [TJ1345. S187 2008 f rb].

Fine grinding is normally carried out in energy intensive grinding mills such as jet mill. Besides size reduction, jet mill also induced mechanochemical effect on the ground product. Proses pengisaran halus biasanya dilakukan di dalam pengisar intensif tenaga seperti pengisar jet. Selain daripada pengurangan saiz, pengisar jet juga meghasilkan kesan mekanokimia terhadap partikel yang dikisar

Pengaruh Kehalusan Serbuk Pasir Silika Terhadap Kekuatan Tekan Mortar

Penelitian ini merupakan bagian dari penelitian beton ringan yang menggunakan serbuk pasir silika dan styrofoam. Kandungan mineral utama pasir silika berupa silikat (SiO2) dapat dipakai sebagai bahan tambahan dalam campuran beton untuk meningkatkan kekuatan. Dengan ini pasir silika diduga dapat bersifat pozzolanic dan bersifat amorf sehingga dapat dipakai sebagai cementitious material pada beton. Pasir silika dihaluskan menjadi serbuk pasir silika (sps) dengan dua tingkat kehalusan. Kehalusan I (sps I) sebesar 22,44 % tertahan pada saringan no.325 dan kehalusan II (sps II) sebesar 58,12 % tertahan pada saringn no.325. Penelitian ini diawali dengan pemeriksaan sifat fisika dan kimia serta XrayDifraction (XRD) material. Kemudian dilanjutkan dengan pengujian pasta (semen+air) dan mortar I (sps I+semen+air) serta mortar II (sps II+semen+air) dengan kadar sps 30% , 40% , 50% dari berat sps dan semen. Dari hasil pemeriksaan komposisi kimia dan sifat fisika, sps belum memenuhi spesifikasi ASTM C618-03 dan berdasarkan hasil pengujian XRD ternyata sps merupakan bahan yang bukan amorf sehingga sps tidak bersifat pozzolan tetapi hanya sebagai filler saja. Pada pengujian pasta dengan kadar sps 0 % dihasilkan kuat tekan umur 28 hari 63,267 Mpa. Pada pengujian mortar I dengan kadar sps 30%, 40% dan 50% dihasilkan kuat tekan umur 28 hari masing-masing 56,267 MPa, 40,933 MPa, 31,76 MPa. Untuk mortar II dengan kadar sps 30%, 40% dan 50% dihasilkan kuat tekan umur 28 hari masing-masing 40,467 MPa, 37,360 Mpa, 29,254 MPa

The Effect of Impurities on the Physical Properties of Oxychloride Cements

The rapidly increasing use of Stucco, a cement made by mixing magnesite with a solution of magnesium chloride, as an exterior for dwelling houses has given rise to an interesting study of its chemical and physical properties. As usually applied, the stucco is made according to the specifications of the Committee on Specifications for Plastic Magnesite, which recommended the following mixture to be standard: One part by weight of plastic calcined Magnesite; Two parts by weight of Standard Ground Silica; Five parts by weight of Standard Ottawa Sand. This is then mixed with a 22 degree Baume solution of magnesium chloride to the proper consistency. Various colored oxides may be added to color the cement as desired. The cementing properties of such mixture are due to the formation of an oxychloride compound of magnesium by the interaction between magnesite and the magnesium chloride solution, the sand acting only as a filler or as an attachment for the cement crystals

Modifications of powders properties by dry-coating: some examples of processes and products characteristics

International audienceDry-coating appears to be an interesting way to create new composite materials in various application areas, avoiding the use of solvents involved in traditional processes, like granulation. Moreover, dry coating processes can be performed on smaller particles sizes. Typical applications include, but are not limited to, altering flowability, solubility, dispersibility, wettability (hydrophilic/hydrophobic properties), electric, electrostatic, magnetic, optical, color, flavor, shape, etc. Particles with relatively large particle size (host particles, 1-500 µm) can be mechanically coated with fine particles (guest particles, 0,1-50 µm) in order to create new functionality or to improve their initial characteristics. In this study we present results obtained with various products and in particular more accurately in the case of silica host particles coated by magnesium stearate using two processes: the Hybridizer NSH0 of the Nara Machinery company and the Cyclomix of Hosokawa company. In this paper we describe the experimental investigation of an application of dry coating technique to change the surface properties of silica gel particles (d50 = 55 µm) coated with different mass ratio of magnesium stearate (MgSt; d50 = 4,6 µm): 1%, 5% and 15%. The products properties were characterised though different methods: particles size distribution (in order to examine the adhesion quality of the fine particles on host particles), flowability, wettability, Atomic Force Microscopy (AFM), and Electron Microscopy (ESEM). The flowability of the samples was characterized by measurements of the tapped and aerated densities. It has been shown in particular that the flowability of silica gel treated with and without MgSt in Hybridizer was not significantly affected and remained good. The wettability of silica gel was determined by measurements of the contact angle between the water drop and the powder bed prepared for each sample. The results obtained have shown that the coating of silica gel powder by hydrophobic magnesium stearate, can improve its hydrophobic properties