Platinum alloys || What Platinum is Used for || Platinum Chemical Properties

platinum alloys are palladium, iridium, rhodium, ruthenium, gold and nickel. Pt is a chemical element, which is commonly known as elemental platinum, platinum belonging element, its chemical symbol Pt and it is one of the noble metal. 

The atomic weight is 195.078, which is slightly smaller than that of gold, with an atomic number of 78, which belongs to transition metals. 

It has a melting point of 1772°C, a boiling point of 3827 ± 100°C, a density of 21.45g / ㎝³(20°C), is soft and has good ductility, thermal conductivity and electrical conductivity. 

Sponge platinum is a gray sponge-like substance with a large specific surface area and a strong absorption capacity for gases (especially hydrogen, oxygen, and carbon monoxide). 

Powdered platinum black can absorb a large amount of hydrogen. Platinum chemically inert, stable in air and moist environment, is lower than 450 deg. C heating, the surface form two platinum oxide film, can react with sulfur, phosphorus, a halogen at a high temperature. 

Platinum is insoluble in hydrochloric acid, sulfuric acid, nitric acid and alkaline solutions, but soluble in aqua regia and molten alkali. The oxidation states of platinum are +2, +3, +4, +5, +6. Easy to form coordination compounds, such as [Pt (NH3)₂]Cl₂, K[Pt(NH₃)Cl₅].

Physical and chemical properties

Physical properties

Platinum is a silvery-white shiny metal, with a melting point of 1772°C, a boiling point of 3827 ± 100°C, a density of 21.45g / ㎝³ (20°C), softer, and has good ductility, thermal conductivity and electrical conductivity. Sponge platinum is a gray sponge-like substance with a large specific surface area and a strong absorption capacity for gases.

Platinum is a transition metal with high density and ductility, silvery-white color, metallic luster, hardness 4-4.5, and relative density of 21.45. The melting point is 1773°C. Fully ductile, can be drawn into very fine platinum wire and rolled into the extremely thin platinum foil.

Chemical properties

Extremely stable chemical properties, Insoluble in strong acid and alkali solution, does not oxidize in air. The first ionization energy is 9.0 electron volts. The valences are +2, +4 and +6. The melting point is 1772°C and the boiling point is 3827°C. The density is 21.46g /㎝³. 

Silver-white metal, soft and malleable. The crystal structure is a face-centered cube. Platinum has high chemical stability.

In addition to being soluble in aqua regia and molten alkali, it is also soluble in a mixture of hydrochloric acid and hydrogen peroxide, hydrochloric acid and perchloric acid. In addition, platinum is not as strong as ordinary strong acids at room temperature.

Alkali and other reagents. However, platinum is susceptible to corrosion at high temperatures. For example: for many oxidants, strong alkalis, heavy metals that are easily reduced, and sulfur, phosphorus, arsenic, etc., platinum is either destroyed or alloyed with it.

Do not heat or melt alkali metal oxides, sodium thiosulfate, phosphorous and sulfur-rich substances, and samples containing heavy metals (such as lead, tin, antimony, arsenic, mercury, copper, etc.) in platinum vessels. 

Do not use a large amount of super-oxidant, sodium (potassium hydroxide) as flux at high temperature. Platinum vessels are not allowed to handle halogens or substances that decompose halogens. But the following substances can dissolve platinum:

  • Aqua regia (a mixture of nitric acid and hydrochloric acid in a ratio of 1: 3 (volume ratio))

Although aqua regia can dissolve platinum, this is related to the state of platinum. Dense platinum dissolves very slowly in aqua regia at room temperature. It takes 4-5 hours for a platinum wire with a diameter of 1 mm to completely dissolve. 

Platinum black (platinum powder) can react with concentrated sulfuric acid when heated to form Pt (SO4)2, SO2 and water. Chloroplatinic acid is produced by dissolving platinum in aqua regia. The product of this reaction is H2PtCl.6, not previously considered nitrogen-containing platinum compounds. Chloroplatinic acid is a reddish-brown solid that can be obtained by evaporating its solution.

  • Pt + 4 HNO 3 + 6 HCl → H 2 PtCl 6 + 4 NO 2 + 4 H 2 O
  • Alkali metal cyanide

Alkali metal cyanides can also dissolve platinum. Platinum can react with halogens at high temperatures, but selenium, tellurium, and phosphorus react more easily with platinum. Dense metallic platinum is not oxidized in the air at any temperature.

  • Mixture of hydrochloric acid and hydrogen peroxide
  • Molten alkali
  • Mixture of hydrochloric acid and perchloric acid

Reaction with aqua regia: 3Pt + 4HNO3 + 18HCl = 3H2 [PtCl6] + 4NO ↑ + 8H2O

Dissolve the treated platinum concentrate or anode copper produced from electrolytic copper and nickel with aqua regia. After a series of chemical treatments, ammonium chloroplatinate can be obtained.

It is slowly burned at 1000°C to decompose to obtain spongy platinum. Platinum is subjected to chemical reactions such as hydrogenation, dehydrogenation, isomerization, cyclization, dehydration, dehalogenation, oxidation, and cracking, as well as a contact method to produce sulfuric acid, ammonia oxidation to produce nitric acid, ammonia and methane to produce hydrocyanic acid, and to prepare cyclohexane. 

It is used as a catalyst in the production of vitamins. Reforming naphtha with a platinum catalyst can increase the octane number of gasoline products. Platinum and its alloys are resistant to oxidation and corrosion at high temperatures and are used to make crucibles, evaporation dishes, electrodes, nozzles, reactors, and so on. Platinum and platinum-rhodium alloys are used as wire and thermocouples for high-temperature furnaces in the metallurgical, glass, and ceramic industries. Platinum is also used in jewelry.

Classification

Platinum, also known as platinum, is a Group VIII platinum element of the periodic table, a tin-white metal, with an atomic number of 78, a relative atomic mass of 195.09, a density of 21.45 g/cm³, a melting point of 1769°C, and a boiling point of 3800°C. Pure platinum has good high-temperature oxidation resistance and chemical stability and is easy to form. Platinum compounds are used as catalysts in the fields of the chemical industry, pharmaceuticals, refining, and automobile exhaust purification.

Natural platinum

Platinum minerals containing impurities such as iron, iridium, and palladium are silver-white or dark gray and belong to the equiaxed crystal system. They are irregular granular or scaly aggregates with a density of 13.35 ~ 19g/cm³ and are rich in ductility. Chemical composition: Pt crystal is a natural element mineral of the Equiaxed crystal system. Also known as platinum, the so-called platinum in ancient Chinese books refers to silver, not platinum. 

In addition to Pt, natural platinum often contains iron, which is called crude platinum ore when it reaches 9 ~ 11%; it is called iron platinum ore when it is higher, up to 28%. It also often contains nickel, gold, copper, palladium, iridium and rhodium. The highest palladium content is 21.8 ~ 30.0%, and iridium is 27.79 ~ 29.0.

Sponge Platinum

Gray sponge metal with platinum mass fraction ≥99.9%, divided into three grades according to platinum content: SM-Pt99.99, SM-Pt99.95, and SM-Pt99.9, generally smelted by fire and warm methods System.

High-purity sponge platinum

Gray sponge-like metals with platinum mass fraction ≥99.995% are divided into two grades according to platinum content: SM-Pt99.995 and SM-Pt99.999, which are generally prepared after separation and purification from various platinum-containing materials for the chemical industry, electrical instruments, precision alloys and temperature measurement materials.

Ultrafine platinum powder

Contain platinum ≥99.95%, average particle size 7.0m / g, bulk density is 0.4 ~ 0.7g / cm, tap density is 0.7 ~ 1.1g / cm-3.

Platinum iridium alloy

The platinum-based iridium-containing binary alloy is a continuous solid solution at high temperature. When it is slowly cooled to 975 ~ 700 ℃, solid-phase decomposition occurs, but the phase equilibrium process proceeds slowly. Iridium is volatile and oxidizable, which can significantly improve the corrosion resistance of platinum. 

The alloy has the characteristics of high hardness, high melting point, high corrosion resistance and low contact resistance.

Platinum silver alloy

The peritectic reaction of platinum-based silver-containing binary alloy occurred at 1185°C and 45% Ag. The alloy has high strength, good elasticity and low elastic after-effect, small resistivity, low thermoelectric potential, heat resistance, corrosion resistance, non-magnetism, stable performance, smelting and processing of platinum-silver alloys are difficult, and high-frequency induction heating furnaces are generally used Hydrogen protection smelting. The ingot must be homogenized and processed into plates and wires.

Platinum molybdenum alloy

The platinum-based binary alloy containing molybdenum has a platinum-enriched solid solution with a Face-Centered cubic structure, and the resistivity increases linearly with the increase in molybdenum content. The tensile strength of the platinum-molybdenum alloy is 922N/ mm-2, the resistivity is 0.64Ω.mm-2/m, and the temperature coefficient of resistance is 2.4× 10⁻⁴/℃. 

Use high-frequency induction heating furnace for hydrogen protection smelting, condensing and exhausting several times, casting and cold processing into wires and sheets after hot forging. Platinum and molybdenum alloys are mainly used as thermocouple materials.

They have high thermoelectric potential and good stability and can work in nuclear fields. The operating temperature is 1500 ~ 1600 ℃. In addition, platinum-molybdenum alloys can also be used as potentiometer windings and high-temperature strain materials.

Platinum rhenium alloy

A platinum-based rhenium-containing binary alloy undergoes a simple peritectic reaction at a temperature of 2450°C, and is protected by hydrogen in a high-frequency furnace for smelting. After hot blooming, it is cold processed into material. 

There are two types of platinum-rhenium alloys: PtRe8 and PtRe14. PtRe8 is a high-temperature thermocouple material. When paired with rhodium, the instantaneous temperature can reach 1800°C and when paired with platinum, it is 1600°C. PtRe14 alloy is used as an electrical contact material.

Platinum cobalt alloy

Platinum-based cobalt-containing binary alloys, at high temperatures, platinum and cobalt can be infinitely soluble. Its solid solution is a face-centered cubic lattice, which is slowly cooled to 833°C, and an orderly transformation begins to occur in the alloy. 

Platinum and cobalt alloys are extremely magnetic, have high magnetic stability, and have good chemical resistance. Neither potassium hydroxide nor hot concentrated sulfuric acid can corrode them. The alloy is mainly used in aerospace, marine, aviation instruments, measuring instruments, electronic clocks, magnetrons, etc.

Platinum copper alloy

The platinum-based copper-containing binary alloy is a continuous solid solution at high temperatures. At low temperatures, there is an orderly transformation in the range of 3% ~ 93% copper composition, and the phase structure changes from cubic lattice to rhombohedral, resulting in the alloy. Significantly strengthened. Products are PtCu2.5, PtCu5,

PtCu8.5, PtCu15, PtCu25 and other alloys are smelted in a high-frequency induction heating furnace or an intermediate-frequency induction heating furnace. After the ingots are homogenized, they are processed into materials, which are mainly used to manufacture electrical contacts and resistance materials.

Platinum nickel alloy

The platinum-based nickel-containing binary alloy is a continuous solid solution at high temperatures and generates two superstructure compounds below about 645°C. Platinum-nickel alloys include alloys such as PtNi2, PtNi5, PtNi10, and PtNi20. When heated in an oxidizing atmosphere, nickel is selectively oxidized. It is smelted with argon protection in a high-frequency induction heating furnace and can be processed into wires and sheets.

Platinum ruthenium alloy

Binary alloys containing ruthenium based on platinum include alloys such as PtRu4, PtRu5, PtRu10, and PtRu14. Ruthenium improves anti-corrosion ability and strong anti-discoloration ability. Ruthenium selectively oxidizes and volatilizes above 900 ℃. Use high-frequency induction heating furnace to protect smelting.

Platinum rhenium alloy

A platinum-based rhenium-containing binary alloy. Osmium has the effect of improving the hardness and resistivity of the alloy. The platinum-rhenium alloy is smelted by argon gas protection in a high-frequency furnace, and then cold-rolled into the material after hot rolling. 

preparation

  • Enrichment: Gravity is the main method for enriching platinum minerals. The relative density of platinum ore is relatively large, and it can be effectively enriched by using chute, jig, shaker and wind beneficiation. Natural platinum, like natural gold, has a small surface wettability, and flotation with xanthate as a collector. After enrichment, the concentrate is obtained.
  • Refining: Traditional refining methods are based on processes such as dissolution, reduction, precipitation, and calcination. The platinum concentrate is dissolved with aqua regia, platinum, palladium, and gold enter the solution, and gold is reduced from the obtained solution with ferrous sulfate, and pure gold can be obtained by electrolysis. Ammonium chloride is added to the solution to precipitate platinum as ammonium chloroplatinate, and crude platinum is obtained by calcination, and then refined by sodium bromide hydrolysis. The traditional dissolving and precipitating method have long and complicated processing steps, the separation of metals is incomplete, and it is difficult to obtain high-purity products. Low metal recovery and high cost. The extraction process that began in 1970 uses cl2 / HCl mixture as a medium to achieve the complete leaching of precious metals, which improves the separation efficiency, shortens the processing time, and ensures that high-purity products are obtained. Therefore, modern processes for platinum refining are based on solvent extraction.

Purpose

Platinum has a wide range of applications due to its high chemical stability (insoluble in any acids and bases except aqua regia) and its catalytic activity. It can be combined with cobalt to make strong magnets. Mostly used to make corrosion-resistant chemical instruments, such as various reaction vessels, evaporation dishes, crucibles, electrodes, platinum mesh, etc.

Platinum and platinum-rhodium alloys are often used as thermocouples to measure temperatures from 1200 to 1750°C. It can also be used to make jewelry. Platinum can be used as a catalyst in chemical reactions such as hydrogenation, dehydrogenation, isomerization, cyclization, dehydration, dehalogenation, oxidation, and cracking. 

In medicine, it can be used as an anticancer drug, and platinum compounds such as cisplatin are used for cancer chemotherapy.

  • Electronic materials, surfactants.
  • Storage and transportation
  • Store dry and sealed at room temperature.
  • Danger statement
Danger code F
Levels of danger R11
Security Level S16
UN number 3089

Sanjay Bhandari

Hello Friends, My name is Sanjay Bhandari. I am a chemistry Teacher.

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