Process for the production of star-tracking reticles

Reticles designed with quartz bases are masked with desired pattern and then are coated with highly adherent layers of chromium, chromium silver alloy, silver, copper, and black chromium (mixture of chromium and chromium oxides). Black chromium final layer produces required nonreflective surface

The Interpretation of Experimental Observation Data for the Development of Mechanisms based Creep Damage Constitutive Equations for High Chromium Steel

It is very important to design a safe factor or estimating the remain lifetime for electric power plant components of steam pipes which mostly manufacture by high chromium steels and work at high temperature and low stress level. The author will develop the mechanisms based on creep damage constitutive equations for high chromium steel under lows stress in initial stage: (1) Creep cavities mostly formed attaching with the precipitation of Laves phase or on grain boundary for high chromium steel under low stress. The Laves phase should play an active role in the nucleation of creep cavities and suggest to explore the function between cavity nucleation and the evolution of Laves phase; (2) The dominant cavity nucleation mechanism is adapted to high chromium steels under low stress level; (3) Brittle intergranluar model is appropriate for high chromium steels at high temperature under low stress level; (4) High density number of cavity of crept test high chromium steel at high temperature under low stress could be as fracture criterion

New alloys to conserve critical elements

Based on availability of domestic reserves, chromium is one of the most critical elements within the U.S. metal industry. New alloys having reduced chromium contents which offer potential as substitutes for higher chromium containing alloys currently in use are being investigated. This paper focuses primarily on modified Type 304 stainless steels having one-third less chromium, but maintaining comparable oxidation and corrosion properties to that of type 304 stainless steel, the largest single use of chromium. Substitutes for chromium in these modified Type 304 stainless steel alloys include silicon and aluminum plus molybdenum

PABRIK CHROMIUM TRIOXIDE DARI SODIUM DICHROMATE DAN ASAM SULFAT

Perencanaan pabrik chromium trioxide ini diharapkan dapat berproduksi dengan kapasitas 42.000 ton chromium trioxide/tahun dalam bentuk kristal. Pabrik beroperasi secara continuous selama 330 hari dalam setahun. Kegunaan terbesar dari chromium trioxide adalah pada bidang industri pengolahan logam, seperti : pelapisan logam, elektroplating logam, dan sebagainya. Kegunaan lain pada industri kimia proses seperti : industri keramik, industri kaca, spektrophotoscopy, serta industri instrumentasi di Indonesia. (wikipedia.org). Secara singkat, uraian proses dari pabrik chromium trioxide sebagai berikut : sodium dichromate diencerkan, kemudian direaksikan dengan asam sulfat membentuk chromium trioxide. Larutan chromium trioxide kemudian difiltrasi untuk memisahkan sodium sulfat. Setelah filtrasi, larutan chromium trioxide kemudian dipekatkan samapi 60%, dikristalisasi, dan dikeringkan pada dryer. Pendirian pabrik berlokasi di Manyar, Gresik dengan ketentuan : Bentuk Perusahaan : Perseroan Terbatas Sistem Organisasi : Garis dan Staff Jumlah Karyawan : 210 orang Sistem Operasi : Continuous Waktu Operasi : 330 hari/tahun ; 24 jam/hari Analisa Ekonomi : * Massa Konstruksi : 2 Tahun * Umur Pabrik : 10 Tahun * Fixed Capital Investment (FCI) : Rp. 20.990.809.000 * Working Capital Investment (WCI) : Rp. 23.935.227.000 * Total Capital Investment (TCI) : Rp. 44.926.036.000 * Biaya Bahan Baku (1 tahun) : Rp. 263.838.739.000 * Biaya Utilitas (1 tahun) : Rp. 9.155.932.000 - Steam = 272.592 lb/hari - Air pendingin = 418 m3/hari - Listrik = 9.960 kWh/hari - Bahan Bakar = 2.736 liter/hari * Biaya Produksi Total (Total Production Cost) : Rp. 287.222.719.000 * Hasil Penjualan Produk (Sale Income) : Rp. 326.909.875.000 * Bunga Bank (Kredit Investasi Bank Mandiri) : 19% * Internal Rate of Return : 23,63% * Rate On Investment : 24,87% * Pay Out Periode : 3,9 Tahun * Break Even Point (BEP) : 34

Production of a chromium Bose-Einstein condensate

The recent achievement of Bose-Einstein condensation of chromium atoms [1] has opened longed-for experimental access to a degenerate quantum gas with long-range and anisotropic interaction. Due to the large magnetic moment of chromium atoms of 6 {$\mu$}B, in contrast to other Bose- Einstein condensates (BECs), magnetic dipole-dipole interaction plays an important role in a chromium BEC. Many new physical properties of degenerate gases arising from these magnetic forces have been predicted in the past and can now be studied experimentally. Besides these phenomena, the large dipole moment leads to a breakdown of standard methods for the creation of a chromium BEC. Cooling and trapping methods had to be adapted to the special electronic structure of chromium to reach the regime of quantum degeneracy. Some of them apply generally to gases with large dipolar forces. We present here a detailed discussion of the experimental techniques which are used to create a chromium BEC and alow us to produce pure condensates with up to {$10^5$} atoms in an optical dipole trap. We also describe the methods used to determine the trapping parameters.Comment: 17 pages, 9 figure

Oxidation of Columbium-Chromium Alloys at Elevated Temperatures

Screening studies of the oxidation characteristics of binary alloys of columbium (Ref. 1) showed that chromium was an additive element worthy of intensive study. The screening studies showed that chromium additions were especially helpful in decreasing the oxidation rate of columbium at 10000deg C and were somewhat less beneficial at 12000deg C. It is the purpose of this investigation to study the oxidation characteristics of binary columbium-chromium alloys in more detail

Kinetics of chromium ion absorption by cross-linked polyacrylate films

Three cross-linked ion exchange membranes were studied as to their ability to absorb chromium ion from aqueous chromium III nitrate solutions. Attention was given to the mechanism of absorption, composition of the absorbed product, and the chemical bonding. The membranes were: calcium polyacrylate, polyacrylic acid, and a copolymer of acrylic acid and vinyl alcohol. For the calcium polyacrylate and the copolymer, parabolic kinetics were observed, indicating the formation of a chromium polyacrylate phase as a coating on the membrane. The rate of absorption is controlled by the diffusion of the chromium ion through this coating. The product formed in the copolymer involves the formation of a coordination complex of a chromium ion with 6 carboxylic acid groups from the same molecule. The absorption of the chromium ion by the polyacrylic acid membranes appears to be more complicated, involving cross-linking. This is due to the coordination of the chromium ion with carboxylic acid groups from more than one polymer molecule. The absorption rate of the chromium ion by the calcium salt membrane was found to be more rapid than that by the free polyacrylic acid membrane