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Nickel
Nickel (pronounced /ˈnɪkəl/) is a chemical element, with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. It is one of the four ferromagnetic elements at about room temperature. Its use has been traced as far back as 3500 BC, but it was first isolated and classified as a chemical element in 1751 by Axel Fredrik Cronstedt, who initially mistook its ore for a copper mineral. Its most important ore minerals are laterites, including limonite and garnierite, and pentlandite. Major production sites include Sudbury region in Canada, New Caledonia and Russia. The metal is corrosion-resistant, finding many uses in alloys, as a plating, in the manufacture of coins, magnets and common household utensils, as a catalyst for hydrogenation, and in a variety of other applications. Enzymes of certain life-forms contain nickel as an active center making the metal essential for them.
Nickel is a silvery-white metal with a slight golden tinge that takes a high polish. It is one of only four elements that are magnetic at or near room temperature. It belongs to the transition metals and is hard and ductile. It occurs most often in combination with sulfur and iron in pentlandite, with sulfur in millerite, with arsenic in the mineral nickeline, and with arsenic and sulfur in nickel galena.[3] Nickel is commonly found in iron meteorites as the alloys kamacite and taenite. Similar to the elements chromium, aluminium and titanium, nickel is a very reactive element, but is slow to react in air at normal temperatures and pressures due to the formation of a protective oxide surface. Due to its permanence in air and its slow rate of oxidation, it is used in coins, for plating metals such as iron and brass, for chemical apparatus, and in certain alloys such as German silver.
Nickel is chiefly valuable for the alloys it forms, especially many superalloys, and particularly stainless steel. Nickel is also a naturally magnetostrictive material, meaning that in the presence of a magnetic field, the material undergoes a small change in length.[4] In the case of nickel, this change in length is negative (contraction of the material), which is known as negative magnetostriction and is on the order of 50 ppm.
The most common oxidation state of nickel is +2 with several Ni complexes known. It is also thought that a +6 oxidation state may exist, however, this has not been demonstrated conclusively. The unit cell of nickel is a face centered cube with a lattice parameter of 0.352 nm giving a radius of the atom of 0.125 nm.[5]
History
Because the ores of nickel are easily mistaken for ores of silver, understanding of this metal and its use dates to relatively recent times. However, the unintentional use of nickel is ancient, and can be traced back as far as 3500 BC. Bronzes from what is now Syria had contained up to 2% nickel.[6] Further, there are Chinese manuscripts suggesting that "white copper" (cupronickel, known as baitung) was used there between 1700 and 1400 BC. This Paktong white copper was exported to Britain as early as the 17th century, but the nickel content of this alloy was not discovered until 1822.[7]
In medieval Germany, a red mineral was found in the Erzgebirge (Ore Mountains) which resembled copper ore. However, when miners were unable to extract any copper from it they blamed a mischievous sprite of German mythology, Nickel (similar to Old Nick) for besetting the copper. They called this ore Kupfernickel from the German Kupfer for copper.[8][9][10][11] This ore is now known to be nickeline or niccolite, a nickel arsenide. In 1751, Baron Axel Fredrik Cronstedt was attempting to extract copper from kupfernickel and obtained instead a white metal that he named after the spirit which had given its name to the mineral, nickel.[12] In modern German, Kupfernickel or Kupfer-Nickel designates the alloy cupronickel.
In the United States, the term "nickel" or "nick" was originally applied to the copper-nickel Indian cent coin introduced in 1859. Later, the name designated the three-cent coin introduced in 1865, and the following year the five-cent shield nickel appropriated the designation, which has remained ever since. Coins of pure nickel were first used in 1881 in Switzerland.[9][13]
After its discovery the only source for nickel was the rare Kupfernickel, but from 1824 on the nickel was obtained as byproduct of cobalt blue production. The first large scale producer of nickel was Norway, which exploited nickel rich pyrrhotite from 1848 on. The introduction of nickel in steel production in 1889 increased the demand for nickel and the nickel deposits of New Caledonia, which were discovered in 1865, provided most of the world's supply between 1875 and 1915. The discovery of the large deposits in the Sudbury Basin, Canada in 1883, in Norilsk-Talnakh , Russia in 1920 and in the Merensky Reef, South Africa in 1924 made large-scale production of nickel possible.[7]
Occurrence
The bulk of the nickel mined comes from two types of ore deposits. The first are laterites where the principal ore minerals are nickeliferous limonite: (Fe, Ni)O(OH) and garnierite (a hydrous nickel silicate): (Ni, Mg)3Si2O5(OH). The second are magmatic sulfide deposits where the principal ore mineral is pentlandite: (Ni, Fe)9S8.
In terms of supply, the Sudbury region of Ontario, Canada, produces about 30 percent of the world's supply of nickel. The Sudbury Basin deposit is theorized to have been created by a meteorite impact event early in the geologic history of Earth. Russia contains about 40% of the world's known resources at the Norilsk deposit in Siberia. The Russian mining company MMC Norilsk Nickel obtains the nickel and the associated palladium for world distribution. Other major deposits of nickel are found in New Caledonia, France, Australia, Cuba, and Indonesia. Deposits found in tropical areas typically consist of laterites which are produced by the intense weathering of ultramafic igneous rocks and the resulting secondary concentration of nickel bearing oxide and silicate minerals. Recently, a nickel deposit in western Turkey had been exploited, with this location being especially convenient for European smelters, steelmakers and factories. The one locality in the United States where nickel was commercially mined is Riddle, Oregon, where several square miles of nickel-bearing garnierite surface deposits are located. The mine closed in 1987.[14][15] In 2005, Russia was the largest producer of nickel with about one-fifth world share closely followed by Canada, Australia and Indonesia, as reported by the British Geological Survey.
Based on geophysical evidence, most of the nickel on Earth is postulated to be concentrated in the Earth's core. Kamacite and taenite are naturally occurring alloys of iron and nickel. For kamacite the alloy is usually in the proportion of 90:10 to 95:5 although impurities such as cobalt or carbon may be present, while for taenite the nickel content is between 20% and 65%. Kamacite and taenite occur in nickel-iron meteorites.
Applications
Nickel is used in many industrial and consumer products, including stainless steel, magnets, coinage, rechargeable batteries, electric guitar strings and special alloys. It is also used for plating and as a green tint in glass. Nickel is pre-eminently an alloy metal, and its chief use is in the nickel steels and nickel cast irons, of which there are many varieties. It is also widely used in many other alloys, such as nickel brasses and bronzes, and alloys with copper, chromium, aluminium, lead, cobalt, silver, and gold [16]
The amounts of nickel used for various applications are 60% used for making nickel steels, 14% used in nickel-copper alloys and nickel silver, 9% used to make malleable nickel, nickel clad, Inconel and other superalloys, 6% used in plating, 3% use for nickel cast irons, 3% in heat and electric resistance alloys, such as Nichrome, 2% used for nickel brasses and bronzes with the remaining 3% of the nickel consumption in all other applications combined.[17][18] In the laboratory, nickel is frequently used as a catalyst for hydrogenation, most often using Raney nickel, a finely divided form of the metal alloyed with aluminium which adsorbs hydrogen gas. Nickel is often used in coins, or occasionally as a substitute for decorative silver. The American 'nickel' five-cent coin is 75% copper and 25% nickel. The Canadian nickel minted at various periods between 1922-81 was 99.9% nickel, and was magnetic.[19] Various other nations have historically used and still use nickel in their coinage.
Nickel is also used in fire assay as a collector of platinum group elements, as it is capable of full collection of all 6 elements, in addition to partial collection of gold. This is seen through the nature of nickel as a metal, as high throughput nickel mines may run PGE recovery (primarily platinum and palladium), such as Norilsk in Russia and the Sudbury Basin in Canada.
Extraction and purification
Nickel is recovered through extractive metallurgy. Most sulfide ores have traditionally been processed using pyrometallurgical techniques to produce a matte for further refining. Recent advances in hydrometallurgy have resulted in recent nickel processing operations being developed using these processes. Most sulfide deposits have traditionally been processed by concentration through a froth flotation process followed by pyrometallurgical extraction.
Nickel is extracted from its ores by conventional roasting and reduction processes which yield a metal of >75% purity. Final purification of nickel oxides is performed via the Mond process, which increases the nickel concentrate to >99.99% purity[20]. This process was patented by L. Mond and was used in South Wales in the 20th century. Nickel is reacted with carbon monoxide at around 50 °C to form volatile nickel carbonyl. Any impurities remain solid while the nickel carbonyl gas passes into a large chamber at high temperatures in which tens of thousands of nickel spheres, called pellets, are constantly stirred. The nickel carbonyl decomposes, depositing pure nickel onto the nickel spheres. Alternatively, the nickel carbonyl may be decomposed in a smaller chamber at 230 degrees Celsius to create fine nickel powder. The resultant carbon monoxide is re-circulated through the process. The highly pure nickel produced by this process is known as carbonyl nickel. A second common form of refining involves the leaching of the metal matte followed by the electro-winning of the nickel from solution by plating it onto a cathode. In many stainless steel applications, 75% pure nickel can be used without further purification depending on the composition of the impurities.
Nickel sulfide ores undergo flotation (differential flotation if Ni/Fe ratio is too low) and then are smelted. After producing the nickel matte, further processing is done via the Sherritt-Gordon process. First copper is removed by adding hydrogen sulfide, leaving a concentrate of only cobalt and nickel. Solvent extraction then efficiently separates the cobalt and nickel, with the final nickel concentration >99%.
Compounds
Nickel sulfate crystals
Nickel(II) sulfate is produced in large quantities by dissolving nickel metal or oxides in sulfuric acid. This compound is useful for electroplating nickel.
Four halides are known to form nickel compounds, these are nickel(II) fluoride, chloride, bromide, and iodide. Nickel(II) chloride is produced analogously by dissolving nickel residues in hydrochloric acid. Tetracarbonylnickel (Ni(CO)4), discovered by Ludwig Mond,[21] is a homoleptic complex of nickel with carbon monoxide. Having no net dipole moment, intermolecular forces are relatively weak, allowing this compound to be liquid at room temperature. Carbon monoxide reacts with nickel metal readily to give this compound; on heating, the complex decomposes back to nickel and carbon monoxide. This behavior is exploited in the Mond process for generating high-purity nickel.
Tetracoordinate nickel(II) takes both tetrahedral and square planar geometries. This is in contrast with the other group 10 elements, which tend to exist as square planar complexes. Bis(cyclooctadiene)nickel(0) is a useful intermediate in organometallic chemistry due to the easily displaced cod ligands. Nickel(III) oxide is used as the cathode in many rechargeable batteries, including nickel-cadmium, nickel-iron, nickel hydrogen, and nickel-metal hydride, and used by certain manufacturers in Li-ion batteries.[22]
[edit] Isotopes
Main article: Isotopes of nickel
Naturally occurring nickel is composed of 5 stable isotopes; 58Ni, 60Ni, 61Ni, 62Ni and 64Ni with 58Ni being the most abundant (68.077% natural abundance). 62Ni is the most stable known nuclide of all the existing elements, even exceeding the stability of 56Fe. 18 radioisotopes have been characterised with the most stable being 59Ni with a half-life of 76,000 years, 63Ni with a half-life of 100.1 years, and 56Ni with a half-life of 6.077 days. All of the remaining radioactive isotopes have half-lives that are less than 60 hours and the majority of these have half-lives that are less than 30 seconds. This element also has 1 meta state.
Nickel-56 is produced in large quantities in type Ia supernovae and the shape of the light curve of these supernovae corresponds to the decay via beta radiation of nickel-56 to cobalt-56 and then to iron-56. Nickel-59 is a long-lived cosmogenic radionuclide with a half-life of 76,000 years. 59Ni has found many applications in isotope geology. 59Ni has been used to date the terrestrial age of meteorites and to determine abundances of extraterrestrial dust in ice and sediment. Nickel-60 is the daughter product of the extinct radionuclide 60Fe (half-life = 1.5 Myr). Because the extinct radionuclide 60Fe had such a long half-life, its persistence in materials in the solar system at high enough concentrations may have generated observable variations in the isotopic composition of 60Ni. Therefore, the abundance of 60Ni present in extraterrestrial material may provide insight into the origin of the solar system and its early history. Nickel-62 has the highest binding energy per nucleon of any isotope for any element (8.7946 Mev/nucleon). [23] Isotopes heavier than 62Ni cannot be formed by nuclear fusion without losing energy. Nickel-48, discovered in 1999, is the most proton-rich heavy element isotope known. With 28 protons and 20 neutrons 48Ni is "double magic" (like 208Pb) and therefore unusually stable [24].
The isotopes of nickel range in atomic weight from 48 u (48-Ni) to 78 u (78-Ni). Nickel-78's half-life was recently measured to be 110 milliseconds and is believed to be an important isotope involved in supernova nucleosynthesis of elements heavier than iron.[25]
Biological role
Nickel plays numerous roles in the biology of microorganisms and plants, though they were not recognized until the 1970s.[26] In fact urease (an enzyme which assists in the hydrolysis of urea) contains nickel. The NiFe-hydrogenases contain nickel in addition to iron-sulfur clusters. Such [NiFe]-hydrogenases characteristically oxidise H2. A nickel-tetrapyrrole coenzyme, F430, is present in the methyl coenzyme M reductase which powers methanogenic archaea. One of the carbon monoxide dehydrogenase enzymes consists of an Fe-Ni-S cluster.[27] Other nickel-containing enzymes include a class of superoxide dismutase[28] and a glyoxalase.[29]
Toxicity
Exposure to nickel metal and soluble compounds should not exceed 0.05 mg/cm³ in nickel equivalents per 40-hour work week. Nickel sulfide fume and dust is believed to be carcinogenic, and various other nickel compounds may be as well.[30][31] Nickel carbonyl, [Ni(CO)4], is an extremely toxic gas. The toxicity of metal carbonyls is a function of both the toxicity of a metal as well as the carbonyl's ability to give off highly toxic carbon monoxide gas, and this one is no exception. It is explosive in air.[32]
Sensitized individuals may show an allergy to nickel affecting their skin, also known as dermatitis. Nickel is an important cause of contact allergy, partly due to its use in jewellery intended for pierced ears.[33] Nickel allergies affecting pierced ears are often marked by itchy, red skin. Many earrings are now made nickel-free due to this problem. The amount of nickel which is allowed in products which come into contact with human skin is regulated by the European Union. In 2002 researchers found amounts of nickel being emitted by 1 and 2 Euro coins far in excess of those standards. This is believed to be due to a galvanic reaction.[34]
It was voted Allergen of the Year in 2008 by the American Contact Dermatitis Society.[35]
Metal value
The market price of nickel surged throughout 2006 and the early months of 2007; as of April 5, 2007, the metal was trading at 52,300 USD/tonne or 1.47 USD/oz.[36] The price subsequently fell dramatically from these peaks, and as of 19 January 2009 the metal was trading at 10,880 USD/tonne.[36]
The US nickel coin contains 0.04 oz (1.25 g) of nickel, which at the April 2007 price was worth 6.5 cents, along with 3.75 grams of copper worth about 3 cents, making the metal value over 9 cents. Since the face value of a nickel is 5 cents, this made it an attractive target for melting by people wanting to sell the metals at a profit. However, the United States Mint, in anticipation of this practice, implemented new interim rules on December 14, 2006, subject to public comment for 30 days, which criminalize the melting and export of cents and nickels.[37] Violators can be punished with a fine of up to $10,000 and/or imprisoned for a maximum of five years.
As of June 24, 2009 the melt value of a U.S. nickel is $0.0363145 which is less than the face value.[38]
镍 镍 拼音:niè 繁体字:镍
部首:钅,部外笔画:10,总笔画:15 ; 繁体部首:金,部外笔画:10,总笔画:18
五笔86&98:QTHS 仓颉:XCHUD
笔顺编号:311153251111234 四角号码:86794 UniCode:CJK 统一汉字 U+954D
基本字义--------------------------------------------------------------------------------
● 镍
(镍)
nièㄋㄧㄝˋ
◎ 一种金属元素,可用来制造货币等,镀在其他金属上可以防止生锈。
汉英互译--------------------------------------------------------------------------------
◎ 镍
nickel
English--------------------------------------------------------------------------------
◎ nickel
◎ 镍
镍 niè
〈名〉
近似银白色、硬而有延展性并具有铁磁性的金属元素,它能够高度磨光和抗腐蚀。主要用于合金(如镍钢和镍银)及用作催化剂(如拉内镍,尤指用作氢化的催化剂) [nickel]——元素符号Ni
常用词组--------------------------------------------------------------------------------
◎ 镍币 nièbì
[nickel coin] 镍质的货币
◎ 镍钢 niègāng
[nickel steel] 含镍的钢
[编辑本段]元素名称:镍
元素原子量:58.69
元素类型:金属
原子体积:(立方厘米/摩尔)
6.59
元素在太阳中的含量:(ppm)
80
元素在海水中的含量:(ppm)
太平洋表面 0.0001
地壳中含量:(ppm)
80
原子序数:28
元素符号:Ni
元素中文名称:镍
元素英文名称:Nickel
相对原子质量:58.69
核内质子数:28
核外电子数:28
核电核数:28
质子质量:4.6844E-26
质子相对质量:28.196
所属周期:4
所属族数:VIII
摩尔质量:59
氢化物:NiH3
氧化物:NiO
最高价氧化物化学式:Ni2O3
氧化态:
Main Ni+2
Other Ni-1, Ni0, Ni+1, Ni+3, Ni+4, Ni+6
密度:8.902
熔点:1453.0
沸点:2732.0
声音在其中的传播速率:(m/S)
4900
电离能 (kJ/ mol)
M - M+ 736.7
M+ - M2+ 1735.0
M2+ - M3+ 3393
M3+ - M4+ 5300
M4+ - M5+ 7280
M5+ - M6+ 10400
M6+ - M7+ 12800
M7+ - M8+ 15600
M8+ - M9+ 18600
M9+ - M10+ 21660
外围电子排布:3d8 4s2
核外电子排布:2,8,16,2
晶体结构:晶胞为面心立方晶胞,每个晶胞含有4个金属原子。
晶胞参数:
aa = 352.4 pm
b = 352.4 pm
c = 352.4 pm
α = 90°
β = 90°
γ = 90°
莫氏硬度:4
颜色和状态:银白色金属
原子半径:1.62
常见化合价:+2,+3
发现人:克朗斯塔特
发现时间和地点:1751 瑞典
元素来源:镍黄铁矿[(Ni,Fe)9S8]
元素用途:具有铁磁性的金属元素,它能够高度磨光和抗腐蚀。主要用于合金(如镍钢和镍银)及用作催化剂(如拉内镍,尤指用作氢化的催化剂) ,可用来制造货币等,镀在其他金属上可以防止生锈。
发现人:克郎斯塔特 发现年代:1751年
镍的化合物
1、镍(Ⅱ)的化合物
(1)氧化镍:NiC2O4==NiO+CO+CO2
(2)氢氧化镍:Ni2+2OH-==Ni(OH)2
(3)硫酸镍 2Ni+2H2SO4+2HNO3==2NiSO4+NO2+NO+3H2O NiO+H2SO4==NiSO4+H2O NiCO3+H2SO4==NiSO4+CO2+H2O
(4)卤化镍:NiF2 NiCl2 NiBr2 NiI2
2、镍( Ⅲ )的化合物
(1)氧化高镍
4NiO+O2==2Ni2O3
2Ni(OH)2+Br2+2OH-==Ni2O3+2Br-+3H2O
2Ni2O3+4H2SO4==4NiSO4+O2+4H2O
Ni2O3+6HCl==2NiCl2+Cl2+3H2O
(2)氢氧化高镍
4NiCO3+O2==2Ni2O3+4CO2
2Ni2++6OH-+Br2==2Ni(OH)3+2Br-
2Ni(OH)2+NaClO+H2O==2Ni(OH)3+NaCl
2Ni(OH)3+6HCl==2NiCl2+Cl2+6H2O
镍的配合物
(1)氨配位化合物:[Ni(NH3)6]2+
(2)氰配位化合物:[Ni(CN)4]2-
(3)螯合物:[Ni(en)3]2+
(4)羰基配位化合物
(a) Ni(Co)4
(b)(C2H5)2Ni
发现过程:
1751年,瑞典的克郎斯塔特,用红砷镍矿表面风化后的晶粒与木炭共热,而制得镍。
元素描述:
有铁磁性和延展性,能导电和导热。常温下,镍在潮湿空气中表面形成致密的氧化膜,不但能阻止继续被氧化,而且能耐碱、盐溶液的腐蚀。块状镍不会燃烧,细镍丝可燃,特制的细小多孔镍粒在空气中会自燃。加热时,镍与氧、硫、氯、溴发生剧烈反应。细粉末状的金属镍在加热时可吸收相当量的氢气。镍能缓慢地溶于稀盐酸、稀硫酸、稀硝酸,但在发烟硝酸中表面钝化。镍的氧化态为-1、+1、+2、+3、+4 ,简单化合物中以+2价最稳定,+3价镍盐为氧化剂。镍的氧化物有NiO和Ni2O3。氢氧化镍〔Ni(OH)2〕为强碱,微溶于水,易溶于酸。硫酸镍(NiSO4)能与碱金属硫酸盐形成矾 Ni(SO4)2•6H2O(MI为碱金属离子)。+2价镍离子能形成配位化合物。在加压下,镍与一氧化碳能形成四羰基镍〔Ni(CO)4〕,加热后它又会分解成金属镍和一氧化碳。
银白色金属,密度8.9克/厘米3。熔点1455℃,沸点2730℃。化合价2和3。电离能为7.635电子伏特。质坚硬,具有磁性和良好的可塑性。有好的耐腐蚀性,在空气中不被氧化,又耐强碱。在稀酸中可缓慢溶解,释放出氢气而产生绿色的正二价镍离子Ni2+;对氧化剂溶液包括硝酸在内,均不发生反应。镍是一个中等强度的还原剂。
元素来源:
矿石经煅烧成氧化物后,用水煤气或碳还原而制得。
元素用途:
镍铬合金主要用来制造不锈钢和其他抗腐蚀合金,如镍钢、镍铬钢及各种有色金属合金,含镍成分较高的铜镍合金,就不易腐蚀。也作加氢催化剂和用于陶瓷制品、特种化学器皿、电子线路、玻璃着绿色以及镍化合物制备等等。
元素辅助资料:
镍在地壳中含量不小,大于常见金属铅、锡等,但明显比铁少得多,而且镍和铁的熔点不相上下,因此注定它比铁发现得晚。
17世纪末,欧洲人开始注意镍砒(砷)矿。当时德国用它来制造青色玻璃,采矿工人称它为kupfernickel。“kupfer”在德文中是“铜”;“nickel”是骂人的话,大意是“骗人的小鬼”。因此这一词可以义译为“假铜”。当时人们认为它是铜和砷的混合物。
瑞典化学家克隆斯特研究了这个矿物,他得到了少量与铜不同的金属。他在1751年发表研究报告,认为这是一种新金属,就称它为nickel,这也就是镍的拉丁名称niccolum和符号Ni的来源。镍在欧洲被发现后,德国人首先把它掺入铜中,制成所谓日耳曼银,或称德国银,也就是我国的白铜。
最稳定的同位素
同位素 丰度 半衰期 衰变模式 衰变能量 衰变产物
MeV
56Ni 人造 6.077天 电子捕获 2.136 56Co
58Ni 68.077 % 稳定
59Ni 人造 76,000年 电子捕获 1.072 59Co
60Ni 26.233 % 稳定
61Ni 1.14 % 稳定
62Ni 3.634 % 稳定
63Ni 人造 100.1年 β衰变 2.137 63Cu
64Ni 0.926 % 稳定
镍基本知识介绍
在自然界,最主要的镍矿是红镍矿(砷化镍)与辉砷镍矿(硫砷化镍)。古巴是世界上最著名的蕴藏镍矿的国家,在多米尼加也有大量的镍矿。
金属镍主要用于电镀工业,镀镍的物品美观、干净、又不易锈蚀。极细的镍粉,在化学工业上常用作催化剂。
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镍大量用于制造合金。在钢中加入镍,可以提高机械强度。如钢中含镍量从2.94%增加到了7.04%时,抗拉强度便由52.2公斤/毫米2增加到72.8公斤/毫米3。镍钢用来制造机器承受较大压力、承受冲击和往复负荷部分的零件,如涡轮叶片、曲轴、连杆等。含镍36%、含碳0.3-0.5%的镍钢,它的膨胀系数非常小,几乎不热胀冷缩,用来制造多种精密机械,精确量规等。含镍46%、含碳0.15%的高镍钢,叫“类铂”,因为它的膨胀系数与铂、玻璃相似,这种高镍钢可熔焊到玻璃中。在灯泡生产上很重要,可作铂丝的代用品。一些精密的透镜框,也用这种类铂钢做,透镜不会因热胀冷缩而从框中掉下来。由67.5%镍、16%铁、15%铬、1.5%锰组成的合金,具有很大的电阻,用来制造各种变阻器与电热器。
钛镍合金具有“记忆”的本领,而且记忆力很强,经过相当长的时间,重复上千万次都准确无误。它的“记忆”本领就是记住它原来的形状,所以人们称它为“形状记忆合金”。原来这种合金有一个特性转变温度,在转变温度之上,它具有一种组织结构,而在转变温度之下,它又有另一种组织结构。结构不同,性能也就不同。例如:一种钛镍记忆合金,当它在转变温度之上时,很坚硬,强度大,而在这个温度以下,它却很软,容易冷加工。这样,当我们需要它记忆什么形状时,就把它做成那种形状,这就是它的“永久记忆“形状,在转变温度以下,由于它很软,我们便可以在相当大的程度内使其任意变形。而当需要它恢复到原来形状时,只要把它加热到转变温度以上就行了。
镍具有磁性,能被磁铁吸引。而用铝、钴与镍制成的合金,磁性更强了。这种合金受到电磁铁吸引时,不仅自己会被吸过去,而且在它下面吊了比它重六十倍的东西,也不会掉下来。这样,可以用它来制造电磁起重机。
镍的盐类大都是绿色的。氢氧化镍是棕黑色的,氧化镍则是灰黑色的。氧化镍常用来制造铁镍碱性蓄电池。
二价镍离子常用丁二酮肟来鉴定,在氨性溶液中,镍离子(Ni2+)与丁二酮肟(Dimethylglyoxime)生成鲜红色沉淀(Ni(dmgH)2)。
服装服饰中的镍
镍一般出现在合金中,有服装产品中用作金属配饰,如钮扣、拉链、铆钉、金属耳环、项链、戒指等。有些人对镍会产生过敏性反应,如果长期接触含镍的饰品,就会对皮肤产生严重的刺激。
“镍的释放一直受到EC的限制。对长期接触皮肤的镀金或非镀金产品,其每周排放的数量不超过0.5ug/CM 2。而穿环用的金属底部组件如耳环杆,其每周排放量不能超过0.2ug/cm2。
矿物质:镍,什么是镍,镍的作用
镍的简介
银白色金属,密度8.9克/厘米3。熔点1455℃,沸点2730℃。化合价2和3。质坚硬,具有磁性和良好的可塑性。有好的耐腐蚀性,在空气中不被氧化,又耐强碱。在稀酸中可缓慢溶解,释放出氢气而产生绿色的正二价镍离子Ni2+;对氧化剂溶液包括硝酸在内,均不发生反应。镍是一个中等强度的还原剂。镍不溶于水,二价镍可能是主要生物类型,在生物体内能与很多物质络合、螯合或结合。
镍的发现
镍在地壳中含量不小,大于常见金属铅、锡等,但明显比铁少得多,而且镍和铁的熔点不相上下,因此注定它比铁发现得晚。1751年,瑞典的克郎斯塔特,用红砷镍矿表面风化后的晶粒与木炭共热,而制得镍。1952年有报告提出动物体内有镍,后来又有人提出镍是哺乳动物的必需微量元素,1973年有人第一次提出镍是必需微量元素。1975年以后开展了镍的营养与代谢研究。
食物来源
含镍丰富的食物有:巧克力、果仁、干豆和谷类。
代谢吸收
膳食中的镍经肠道铁运转系统通过肠黏膜,吸收与运转过程尚不清楚,镍的吸收率约3%~10%,奶、咖啡、茶、橘子汁、维生素C等使吸收率下降。在铁缺乏或怀孕和哺乳时吸收率可增加。吸收人血的镍通过血清中主要配体白蛋白运送到全身。镍也与血清中的L-组氨酸和α-巨球蛋白相结合。吸收入血的镍60%由尿排出,汗液中镍的含量较高,胆汁也可排出不少的镍。在某些环境中存在羰基镍,它是无色透明液体,沸点43℃,可以蒸气形式由呼吸系统迅速吸入,皮肤也可少量吸收,羰基镍进入体内后约1/3在6小时由呼气排出,其余通过肺泡吸收入血,最后由尿排出。羰基镍吸入后24h体内仅留17%,6天内全部排出。
生理功能
在较高等动物与人的体内,镍的生化功能尚未了解。但体外实验,动物实验和临床观察提供了有价值的结果。
1.体外实验显示了镍硫胺素焦磷酸(辅羧酶)、磷酸吡哆醛、卟啉、蛋白质和肽的亲和力,并证明镍也与RNA和DNA结合。
2.镍缺乏时肝内6种脱氢敏减少,包括葡萄糖-6-磷酸脱氢酶、乳酸脱氢酶、异柠檬酸脱氢酶、苹果酸脱氢酶和谷氨酸脱氢酶。这些酶参与生成NADH、无氧糖酵解、三羧循环和由氨基酸释放氮。而且镍缺乏时显示肝细胞和线粒体结构有变化,特别是内网质不规整,线粒体氧化功能降低。
3.贫血病人血镍含量减少,而且铁吸收减少,镍有刺激造血功能的作用,人和动物补充镍后红细胞、血红素及白细胞增加。
生理需要
由于膳食中每日摄入镍70~260μg/d,人的需要量是根据动物实验结果推算的,可能需要量为25~35μg/d。
过量表现
每天摄入可溶性镍250mg会引起中毒。有些人比较敏感,摄入600μg即可引起中毒。依据动物实验,慢性超量摄取或超量暴露,可导致心肌、脑、肺、肝和肾退行性变。
镍缺乏症
动物实验显示缺乏镍可出现生长缓慢,生殖力减弱。
镍的制法:
①电解法。将富集的硫化物矿焙烧成氧化物,用炭还原成粗镍,再经电解得纯金属镍。
②羰基化法。将镍的硫化物矿与一氧化碳作用生成四羰基镍,加热后分解,又得纯度很高的金属镍。
③氢气还原法。用氢气还原氧化镍,可得金属镍。
中国镍行业发展情况
中国镍供给有两个部分组成,一部分是新产镍精矿供应,这部分占镍总供给量的72.9%,另一部分来自再生镍占27.1%,随着经济建设和钢铁工业的发展,镍的需求量不断增加。
2006年1-12月,全国镍累计产量为111280.01吨,与2005年同期相比增长了22.07%;2007年1-12月,全国镍累计产量为115772.10吨,与2006年同期相比增长了8.51%;2008年1-10月,全国镍累计产量为112209.99吨,与2007年同期相比增长了8.99%。
中国镍行业在不断发展的同时,也存在一些问题,如镍矿中多为低品味,露采比例很小,可采储量仅占总储量的10%,开采和冶炼的技术相对较为落后;选矿一般采用弱酸或弱碱介质浮选工艺,选矿能力为430万吨/年;中国镍冶炼除几家大型企业以外普遍采用火法的选锍熔炼技术,精炼镍主要采用硫化镍阳极隔膜电解和硫酸选择性浸出——电积工艺,与世界先进技术还有一定差距,因此中国开采和冶炼的成本居高不下。
2010年预计中国镍消费量将达到40万吨/年以后,中国将成为世界最大的镍消费国。现在中国镍金属基础储量只有230万吨左右,近年来中国镍矿勘探没有重大进展,如果就按照这样消费下去的话,10年后中国的镍矿资源将逐渐消耗殆尽。
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