Periodic system ΙΙΙ Group A sub group Lanthanide, a rare earth element. The gray and lively metal is the highest natural abundance among lanthanide metals. The bent cerium strip often sparks. Atomic number 58. Stable nuclide: 136, 138, 140, 142. Gray metal, malleable. Density: 6.9 for square crystals and 6.7 for cubic crystals. Melting point 799 ℃, boiling point 3426 ℃. Cerium is a silver gray active metal, and its powder is prone to spontaneous combustion in air and soluble in acids. The name cerium comes from the English name of the asteroid Ceres. The content of cerium in the crust is about 0.0046%, which is the highest abundance among rare earth elements. Cerium metal is mainly used as a reducing agent.

Chinese name: Cerium English name: Cerium Symbol: Ce Serial number: 58 CAS number: 7440-45-1 Cycle: 6 Element partition: f Atomic mass: 140.116 Density: 6689 kg/m3 Melting point: 1071 K (798 ° C) Boiling point: 3699 K (3426 ° C) Discovered by: Claprot

Element Description

Gray metal with ductility. Melting point 799 ℃, boiling point 3426 ℃. Density: 6.76 grams/cm3 for cubic crystals and 6.66 grams/cm3 for hexagonal crystals. The peripheral Electron shell is arranged 4f15d16s2. The first Ionization energy is 5.47 Electronvolt. The chemical properties are active and can be burned in the air by scraping with a knife (pure cerium is not prone to spontaneous combustion, but it is highly prone to spontaneous combustion when slightly oxidized or formed into an alloy with iron); When heated, it burns in air to form Cerium(IV) oxide. Can react with boiling water, soluble in acids, insoluble in alkalis. When subjected to low temperature and high pressure, a diamagnetic substance appears, which is 18% denser than the ordinary form of cerium. Cerium is the most abundant metallic element among rare earth elements. There are four isotopes: 136Ce, 138Ce, 140Ce, 142Ce. 142Ce is radioactive α Radioactive body with a half-life of 5 × 1015.

compound

Cerium aluminum cerium aluminum is what we usually refer to as Ce aluminum, which is a new type of pure cerium (Ce) system

Aluminum composite coating. It mainly includes cerium (Ce) series pure aluminum coating and Oxirene ester paint coating. The cerium (Ce) series pure aluminum coating is a thermal spraying coating with aluminum as raw material and cerium (Ce) element added. The Oxirene ester paint coating is a sealing layer and a functional coating of the cerium Ce aluminum Thermal spraying layer. The weight percentage of cerium (Ce) added to the pure aluminum coating is 0.05-0.50% (wt), other impurities iron+copper+silicon ≤ 0.30% (wt), and the remainder is aluminum, which can also be used to add the element magnesium. The production method of the pure aluminum coating is: processing into wire or powder, using Thermal spraying technology to make Ce aluminum spray coating on the steel surface. The Oxirene ester paint coating takes Oxirene ester resin as raw material, and adds silicon carbide and aluminum powder or aluminum powder slurry. As the sealing layer, intermediate layer and surface layer of Ce series aluminum coating, Oxirene ester paint can also replace one or all of them with other paint coatings. A cerium (Ce) series pure aluminum composite coating, mainly including: cerium (Ce) series pure aluminum coating and Oxirene ester paint coating, which is characterized in that the cerium (Ce) series pure aluminum coating is a thermal spraying coating with aluminum as raw material and cerium (Ce) element added, and the Oxirene ester paint coating is a sealing layer and a functional coating of the cerium Ce aluminum Thermal spraying layer.

Cerium silicon carbide (CC): Cerium silicon carbide is a type of furnace material in which a small amount of cerium silicon carbide is added without adding salt

The appearance of cerium oxide (CeO2) smelted is similar to that of green silicon carbide, with a microhardness of 36.29Gpa. Compared with green silicon carbide, its cerium silicon carbide has higher microhardness, single particle compressive strength, toughness, etc. Due to the improved physical properties of cerium silicon carbide, its grinding effect has also been improved to some extent. Experiments have shown that when grinding titanium alloys, the cutting efficiency of cerium silicon carbide is nearly twice that of green silicon carbide, and the spark is smaller; When grinding cast iron, when the feed amount is 0.01mm, the durability of cerium silicon carbide grinding wheel is 18.9% higher than that of green silicon carbide grinding wheel, and the grinding ratio is 9.6% higher. When the feed amount is 0.02mm, its durability is 27.4% higher, and the grinding ratio is 74.1% higher. From this, it can be seen that the effect of using cerium silicon carbide to grind the feed amount of cast iron is more significant than that of green silicon carbide. The effect of grinding hard alloy is similar to that of green silicon carbide, while the effect of grinding difficult to grind high-speed steel such as CO5Si M5Al 5F-6 is similar to that of single crystal corundum.

Discovering History

In 1752, Swedish chemist Kronstede discovered a new ore. Spanish mineralogist Don Faustu de Eruye thought it was a silicate of calcium and iron after analysis. In 1803, the German chemist Klaprault analyzed the ore and determined that there was a new metal oxide, called ochra (ocher earth), and the ore was called ochroite because it appeared ochre when it was burned. At the same time, Swedish chemist J ö ns Jakob Berzelius (1779-1848) and Swedish mineralogist Wilhelm Hisinger (1766-1852) also found the same new element oxide, which is different from yttrium earth. Yttrium earth is soluble in Ammonium carbonate solution and turns red when burning on the Gas lighting flame, while this earth is insoluble in Ammonium carbonate solution and does not turn red when burning on the Gas lighting flame. So it is called ceria (cerium earth), the element is named cerium (cerium), the element symbol is set as Ce, and the ore is called cerite (cerite) to commemorate the discovery of an asteroid Ceres at that time. In fact, this type of cerium silicate is a hydrated salt containing 66% to 70% cerium, while the rest are compounds of calcium, iron, and yttrium.

Ochra (ochre earth) and ceria (cerium earth) are oxides of the same element. The latter is adopted; The former has been discarded.

synthetic method

Cerium is the most abundant rare earth metal in the Earth's crust. Metal cerium can be obtained by reducing cerium oxide with calcium or electrolyzing cerium chloride.

70g of Cerium(III) chloride and 18.5g of calcium are thoroughly mixed under inert atmosphere, shaken and loaded into a tantalum crucible or pressed into a cylinder by a power driven press and placed in a tantalum crucible. The crucible is equipped with a perforated tantalum cover for ventilation, and placed in a closed MgO crucible (d=0.0508m, h=0.1778m). Then place it in a quartz tube (d=0.11615m), with one end of the tube fused and sealed, and the other end polished and embedded in a 55/50 conical joint. Seal the quartz tube with paraffin in a vacuum system (0.133Pa). Fill Ar (first purify the overheated metal uranium) to P=101.325kPa, and heat it to 550-600 ℃ using a 6kW induction furnace to cause the reaction to occur (based on a sudden increase in the temperature of the tantalum crucible). After 5 minutes, reach 1000 ℃ and maintain for 13 minutes until the rare earth metal produced is completely agglomerated. Cool to room temperature, soak the tantalum crucible in water to remove CaCl2 and Ca, and keep the rare earth metal melt block at the bottom (1% to 3% Ca)

Content distribution

Cerium mainly exists in monazite and bastnaesite, as well as in fission products of uranium, thorium, and plutonium. It is often obtained by reducing cerium oxide with magnesium powder or by electrolyzing molten cerium chloride.

Basic properties

Relative atomic mass: 140.12

Common valence:+3,+4

Electronegativity: 1.12

Peripheral Electron configuration: 4f15d16s2

Extranuclear Electron configuration: 2,8,18,20,8,2

Isotope and radiation: Ce-134 [3016d] Ce-136Ce-138Ce-139 [137.6d] * Ce-140Ce-141 [32.5d] Ce-142Ce-143 [1.4d]

Ce-144 [284.6d]

Electron affinity and energy: 0KJ • mol-1

First Ionization energy: 528KJ • mol-1

The second Ionization energy: 1047KJ • mol-1

The third Ionization energy: 1880KJ • mol-1

Single substance density: 6.773g/cm3

Single substance melting point: 795.0 ℃

Boiling point of single substance: 3257.0 ℃

Atomic radius: 2.7 angstroms

Ionic radius: 1.14 (+3) angstrom

Covalent radius: 1.65 angstrom

Common compound: CeO2CeCl3

Atomic volume: (cubic centimeters/mole): 20.67

Element content in seawater: (ppm): Pacific surface 0.0000015

Element content in the sun: (ppm): 0.004

Content in the crust: (ppm): 68

Element Atomic mass: 140.1

Crystal structure: The crystal cells are face centered cubic cells, each containing 4 metal atoms.

The propagation rate of sound in it: (m/S) 2100

Oxidation state: Maince+3

OtherCe+4

Ionization energy (kJ/mol)

M-M+527.4

M+- M2+1047

M2+- M3+1949

M3+- M4+3547

M4+- M5+6800

M5+- M6+8200

M6+- M7+9700

M7+- M8+11800

M8+- M9+13200

M9+- M10+14700

Cell parameters:

A=362pm

B=362pm

C=599pm

α= 90 °

β= 90 °

γ= 120 °

Mohs scale hardness: 2.5

Source and purpose

Element source:

Cerium is the most abundant rare earth element in reserves, found in many minerals such as monazite sand [Ce (PO4)]. Cerium mainly exists in monazite and bastnaesite, as well as in fission products of uranium, thorium, and plutonium. It is often obtained by reducing cerium oxide with magnesium powder or by electrolyzing molten cerium chloride.

Element Usage:

1. As a glass additive, cerium can absorb ultraviolet and infrared rays, and has been widely used in Car glass. Not only can it prevent ultraviolet radiation, but it can also reduce the interior temperature of the car, thereby saving electricity for air conditioning. Since 1997, cerium oxide has been added to Car glass in Japan. In 1996, cerium oxide used in Car glass was at least 2000 tons, and about 1000 tons in the United States.

2. At present, cerium is being applied to automobile exhaust purification catalysts, which can effectively prevent a large number of automobile exhaust gases from being discharged into the air. The consumption of Chimerica in this regard accounts for more than one-third of the total consumption of rare earth.

3. Cerium sulfide can replace metals such as lead and cadmium that are harmful to the environment and humans in pigments, color plastics, and can also be used in industries such as coatings, ink, and paper. At present, the leading company is the French company Rhone Planck.

4. The Ce: LiSAF laser system is a solid laser developed by the United States. It can be used to detect biological weapons and medicine by monitoring the concentration of Tryptophan. Cerium is widely used in Almost all rare earth applications. Such as polishing powder, hydrogen storage materials, thermoelectric materials, cerium tungsten electrodes, Ceramic capacitor, piezoelectric ceramics, cerium silicon carbide abrasives, fuel cell raw materials, gasoline catalysts, some permanent magnetic materials, various alloy steels and non-ferrous metals.

5. Manufacturing high brightness carbon arc lamps, mixed with special metals to serve as alloy additives. Oxide is used in optical devices and glass industry, and cerium salt is used in photography and Textile manufacturing. Cerium can be used as a catalyst, arc electrode, special glass, etc. Cerium alloys are heat-resistant and can be used to manufacture parts for jet propulsion. Cerium nitrates can be used to make white hot gauze cover for Gas lighting.

Physicochemical properties cerium chloride

The gray and lively metal is the highest natural abundance among lanthanide metals. The bent cerium strip often sparks.

Cerium is easily oxidized at room temperature and loses its luster in the air. It can be burned in the air by scraping with a knife (pure cerium is not prone to spontaneous combustion, but when slightly oxidized or formed into an alloy with iron, it is highly prone to spontaneous combustion). When heated, it burns in air to form Cerium(IV) oxide. It can react with boiling water to produce cerium hydroxide, soluble in acids but insoluble in alkalis. Cerium can also be burned in halogens, such as chlorine, to produce Cerium(III) chloride (CeCl3): 2Ce+3Cl2== Δ (or ignited)==2CeCl3. When subjected to low temperature and high pressure, a diamagnetic substance appears, which is 18% denser than the ordinary form of cerium. Used for manufacturing flint, ceramics, alloys, etc. Cerium is the most active rare earth element except for europium. Cerium reacts slowly in cold water and accelerates in hot water.

Storage method

Store in a cool and ventilated warehouse. Keep away from sparks and heat sources. The temperature of the warehouse should not exceed 30 ℃. The packaging requires sealing and must not come into contact with air. It should be stored separately from oxidants, acids, halogens, and edible chemicals, and should not be mixed for storage. Using explosion-proof lighting and ventilation facilities. Prohibit the use of mechanical equipment and tools that are prone to sparks. The storage area should be equipped with emergency response equipment for leaks.