Nickel-silicon alloys

Nickel/silicon alloy (10% silicon, 3% copper, and 87% nickel) is fabricated only as castings and is rather brittle, although it is superior to the iron/silicon alloy with respect to strength and resistance to thermal and mechanical shock. It is comparable to the iron/silicon alloy in corrosion resistance to boiling sulfuric acid solutions at concentrations above 60%. Therefore, it is chosen for this and other arduous duties where its resistance to thermal shock justifies its much higher price compared with iron/silicon alloys. 

Miodownik, A. P., Watkin, J. S. and Gittus, J. H. (1979) Calculation of the driving force for the radiation induced precipitation of NiaSi in nickel silicon alloys , UKAEA Report ND> R-283(S), February. 

In 1925 Murray Raney (la) was granted a patent covering a new method of preparation of a nickel catalyst. A pulverized nickel-silicon alloy was reacted with aqueous sodium hydroxide to produce a pyrophoric, brownish nickel residue with superior catalytic properties. Upon investigation of other alloys of nickel and alkali-soluble metals, it was found that the aluminum alloy could be made with ease (lb) and was easily pulverized. The catalyst which is prepared by the action of aqueous sodium hydroxide on this nickel-aluminum alloy is known as... 

Nickel-silicon alloys with the chemical composition given in Table 4.36 are used in handling hot sulfuric acid, 50% nitric acid and mixtures of sulfuric and nitric... 

In 1925 and 1927 Raney patented a new method of preparation of an active catalyst from an alloy of a catalytic metal with a substance that may be dissolved by a solvent that will not attack the catalytic metal. First a nickel-silicon alloy was treated with aqueous sodium hydroxide to produce a pyrophoric nickel catalyst. Soon later, in 1927, the method was improved by treating a nickel-aluminum alloy with sodium hydroxide solution because the preparation and the pulverization of the aluminum alloy were easier. Some of most commonly used proportions of nickel and aluminum for the alloy are 50% Ni-50% Al, 42% Ni-58% Al, and 30% Ni-70% Al. The nickel catalyst thus prepared is highly active and now widely known as Raney Nickel, which is today probably the most commonly used nickel catalyst not only for laboratory uses but also for industrial applications.46... 

Six grams of 42% nickel, 58 % aluminum catalyst powder, all of which would pass a 150 mesh screen, was mechanically mixed in o porcelain mortar with ten grams of the elemental nickel powder for fifteen minutes. The calculated nickel content of the nickel aluminum powder was 2.52 grams, so that the added nickel was practically four times the nickel contained in the nickel aluminum alloy. The added nickel was not combined chemically with the aluminum, but was thoroughly mixed mechanically with the nickel aluminum powder. The six grams of 42% nickel, 58% aluminum powder had a calculated content of 3.48 grams of aluminum. Seven grams of 76% flake sodium hydroxide were used to make a 25% sodium hydroxide water solution. Potassium hydroxide or other caustic alkali solution may be used in place of sodium hydroxide and nickel carbonyl powder may be used in place of elemental nickel powder. Also, a nickel silicon alloy or an alloy of nickel with another alkali soluble metal may be used in place of the nickel aluminum alloy. 

In his first preparation from the nickel-silicon alloy he observed that the reaction was quite vigorous and that a greyish metallic solid, quite pyrophoric when dried and exposed to the air, settled out after the reaction subsided. Because of it pyrophoricity he concluded that pure nickel, not the inactive nickel oxide, had formed. On testing this material for catalytic activity for the hydrogenation of cottonseed oil in his rather simple laboratory test equipment (10), he reported that it was five times as active as the best nickel catalyst then in use. He applied for his first patent (11) in the United States on September 20, 1924 which issued December 1, 1925. Probably... 

With the successful preparation of a catalyst from the nickel-silicon alloy he gave thought to finding other alloys that might also work. He considered aluminum a good choice because it is readily dissolved by aqueous sodium hydroxide. But because of its high cost at the time, he thought that its use would never be practical. His concern for the economics of the... 

TABLE 11.60 Type N Thermocouples Nickel-14.2% Chromium-1.4% Silicon Alloy vs. Nickel-4.4% Silicon-0.1% Magnesium Alloy... 

Soft magnetic materials are characterized by high permeabiUty and low coercivity. There are sis principal groups of commercially important soft magnetic materials iron and low carbon steels, iron—siUcon alloys, iron—aluminum and iron—aluminum—silicon alloys, nickel—iron alloys, iron-cobalt alloys, and ferrites. In addition, iron-boron-based amorphous soft magnetic alloys are commercially available. Some have properties similar to the best grades of the permalloys whereas others exhibit core losses substantially below those of the oriented siUcon steels. Table 1 summarizes the properties of some of these materials. 

Copper—chromium and copper—nickel—silicon—chromium alloys are also precipitation hardenable. The precipitates are nickel sdicides, chromium silicides, and elemental chromium. If conductivity is critical, the chromium—silicon ratio should be held at 10 1 so that appreciable amounts of either element are not left in soHd solution in the copper after aging. Lithium can be used as a deoxidizer in copper alloys when conductivity is important. For a discussion of the principle of age- or precipitation-hardening copper alloys, see Copperalloys,wrought copperalloys. 

The addition of beryllium and silicon to nickel-palladium alloys gives very good high-temperature brazes, especially for alloys containing aluminium and titanium. 

One can readily note the close correlation between the observed variations of the catalytic activity and the evolution of surface nickel concentration (Figure 3A). However, the dramatic difference between the activity of nickel rich alloys [(Nl Sl2) and (Nl2Sl) ] and silicon rich Intermetalllcs [(Nl.Sl.) and (filSl.) ] tar exceeds... 

Almond shell Aluminium, atomized Aluminium, flake Aluminium-cobalt alloy Aluminium-copper alloy Aluminium-iron alloy Aluminium-lithium alloy Aluminium—magnesium alloy Aluminium-nickel alloy Aluminium-silicon alloy Aluminium acetate... 

Nickel-chromium-molybdenum-copper-silicon alloy C, in galvanic series, 7 805t... 

Most structural PMCs consist of a relatively soft matrix, such as a thermosetting plastic of polyester, phenolic, or epoxy, sometimes referred to as resin-matrix composites. Some typical polymers used as matrices in PMCs are listed in Table 1.28. The list of metals used in MMCs is much shorter. Aluminum, magnesium, titanium, and iron- and nickel-based alloys are the most common (see Table 1.29). These metals are typically utilized due to their combination of low density and good mechanical properties. Matrix materials for CMCs generally fall into fonr categories glass ceramics like lithium aluminosilicate oxide ceramics like aluminnm oxide (alnmina) and mullite nitride ceramics such as silicon nitride and carbide ceramics such as silicon carbide. 

Energy losses in soft magnetic materials arise due to both hysteresis and eddy currents, as described in the previous section. Eddy current losses can be reduced by increasing the electrical resistivity of the magnetic material. This is one reason why solid-solution iron-silicon alloys ( 4% Si) are used at power frequencies of around 60 Hz and why iron-nickel alloys are used at audio frequencies. Some magnetically soft ferrites (see Section 6.2.2.1) are very nearly electrical insulators and are thus immune to eddy current losses. Some common soft magnetic materials and their properties are listed in Table 6.19. Soft magnetic alloys are described further in Section 6.2.1.6. 

Materials of Construction. Resistance of alloys to concentrated sulfuric acid corrosion increases with increasing chromium, molybdenum, copper, and silicon content. The corrosiveness of sulfuric acid solutions is highly dependent on concentration, temperature, acid velocity, and acid impurities. An excellent summary is available (114). Good general discussions of materials of construction used in modem sulfuric acid plants may be found in References 115 and 116. More detailed discussions are also available (117—121). For nickel-containing alloys Reference 122 is appropriate. An excellent compilation of the relatively scarce literature data on corrosion of alloys in liquid sulfur trioxide and oleum may be found in Reference 122. 

SAE 780 tin, silicon, and copper alloy, and SAE 770 using tin, copper, and nickel are aluminum alloys which have been widely used in medium- and heavy-duty diesels (6). With silicon and cadmium incorporated for improved compatibility, both SAE 781 and 782 are used as an 0.5 mm to 3.0 mm overlay on a steel backing with a thin electroplated babbitt overlay. Traditional 6% tin—aluminum is also used as the SAE 780 alloy with an oveday. Eleven percent silicon alloys are used for highly loaded diesel bearings in Europe. 

Assay of beryllium metal and beryllium compounds is usually accomplished by titration. The sample is dissolved in sulfuric acid. Solution pH is adjusted to 8.5 using sodium hydroxide. The beryllium hydroxide precipitate is redissolved by addition of excess sodium fluoride. Liberated hydroxide is titrated with sulfuric acid. The beryllium content of the sample is calculated from the titration volume. Standards containing known beryllium concentrations must be analyzed along with the samples, as complexation of beryllium by fluoride is not quantitative. Titration rate and hold times are critical therefore use of an automatic titrator is recommended. Other fluoride-complexing elements such as aluminum, silicon, zirconium, hafnium, uranium, thorium, and rare earth elements must be absent, or must be corrected for if present in small amounts. Copper—beryllium and nickel—beryllium alloys can be analyzed by titration if the beryllium is first separated from copper, nickel, and cobalt by ammonium hydroxide precipitation (15,16). 

Charcoal [7440-44-0] - [GASOLINE AND OTHER MOTOR FUELS] (Vol 12) -calcium carbide om [CARBIDES - CALCIUM CARBIDE] (Vol 4) -m nickel processing [NICKEL AND NICKEL ALLOYS] (Vol 17) -production [WOOD] (Vol 25) -m pyrotechnics [PYROTECHNICS] (Vol 20) -for silicon production [SILICON AND SILICON ALLOYS - CHEMICALAND METALLURGICAL] (Vol 21) -use m military smoke [CITEMICALS IN WAR] (Vol 5) - [CHEMICALS IN WAR] (Vol 5)... 

Chromizing and Related Diffusion Processes. Chromizing is similar to aluminizing. A thin corrosion and wear resistant coaling is applied to low cost steels such as mild steel, or to a nickel-based alloy. In the related boroni/ing process, a thin boron alloy is produced for extreme hardness, wear, and corrosion resistance. Siliconizing is yet another process used especially lor coaling of the refractory metals Ti. Nb. Ta. Cr. Mo. and W. 

---