Neutron gadolinium

Gadolinium has the highest thermal neutron capture cross-section of any known element (49,000 barns). 

Gadolinium s extremely high cross section for thermal neutrons, 4.6 x 10 (46,000 bams) per atom, is the reason for its extensive use in the nuclear energy (see Nuclearreactors). It is used as a component of the fuel or control rods, where it acts as a consumable poison, a trap for neutrons in the reactor (39). 

It should be noted that the ytterbium listed above was a mixture discovered in the mineral erbia by de Marignac in 1878 and not the neoytterbium/aldebaranium element renamed ytterbium that was foimd in the mineral ytterbia. The columbium was a mixture found in the mineral samarskite and was not the present day columbium/niobium. The ionium listed above was a mixture of terbium and gadolinium that was found in the mineral yttria and does not refer to °Th. Finally, the neptunium refers to material fovmd in niobium/tantalum minerals and does not refer to the 1940 discovery of the trans-uranium element produced via a neutron capture reaction on a uranium sample. 

Gadoliniums main use is based on its ability to absorb neutrons, thus making it ideal as a neutron-shielding and neutron-absorbing metal. It is also used as an alloying agent for steel and other metals to make the metals more workable and to be able to withstand low temperatures. 

Colorless or light yellow metal at ordinary temperatures it occurs in hexagonal close-packed crystalline form, known as alpha-gadolinium alpha form transforms to a body-centered cubic allotropic form, beta-gadolinium upon heating at 1,262°C density 7.90 g/cm melting point 1,313°C vaporizes at 3,266°C vapor pressure 9.0 torr at 1,800°C (calculated) electrical resistivity 134.0 microhm-cm at 25°C Poisson ratio 0.259 modulus of elasticity 8.15x106 psi thermal neutron absorption cross section 46,000 barns insoluble in water dissolves in acid (reacts). 

Gadolinium may be measured in an acidic solution by flame or furnace atomic absorption or ICP atomic emission spectropbotometry. Also, gadolinium may be identified nondestructively and rapidly by x-ray fluorescence methods. It also may be measured by neutron activation analysis, and by various spectrophotometric techniques. The element shows sharp absorption bands in ultraviolet region at 270-280 nm. Other lanthanides also produce bands in this region however, those are low intensity minor bands. 

Gadolinium oxide is used in control rods for neutron shielding in nuclear power reactors. It also is used in filament coatings, ceramics, special glasses and TV phosphor activator. The compound also is used as a catalyst. 

Of all the properties of the rare earths that contribute to their many and varied applications one that ranks of special interest is the extremely high thermal neutron capture cross-section associated with the elements gadolinium, samarium, europium and dysprosium, see Table IV. 

By contrast, the metals have so far found only limited application save for one important use in the field of nondestructive testing. With the proliferation of research reactors over the past decade, neutron radiography has become a practical tool in the aerospace, nuclear and engineering industries, yet without the availability of gadolinium and dysprosium in the form of thin foils, the technique would be severely restricted. 

Gadolinium Oxide, Gd203, mw 362.52 wh to cream-colored powder, sp gr 7.407 at 15/4°, mp 2330° hygroscopic and absorbing C02 from the air in sol in w sol in acids except HF. Used in nuclear reactor control sods, neutron shields, catalysts, dielectric ceramics, filament coatings, special glasses and as P... 

In some cases, thermal neutrons can also be used to measure the absolute abundances of other elements. Transforming the neutron spectrum into elemental abundances can be quite involved. For example, to determine the titanium abundances in lunar spectra, Elphic et at. (2002) first had to obtain FeO estimates from Clementine spectral reflectances and Th abundances from gamma-ray data, and then estimate the abundances of the rare earth elements gadolinium and samarium from their correlations with thorium. They then estimated the absorption of neutrons by major elements using the FeO data and further absorption effects by gadolinium and samarium, which have particularly large neutron cross-sections. After making these corrections, the residual neutron absorptions were inferred to be due to titanium alone. 

A second type of image-plate detector employs gadolinium oxide, which absorbs a neutron and emits a gamma ray, which in turn exposes the image plate. Image plates have higher spatial resolution but lower efficiency than multiwire detectors. 

Gadolinium(III) was complexed to the DTPA component of ATN-10 for possible use in neutron capture therapy [113]. An additional benefit of the incorporation of gadolinium(III) into ATN-10 is the increase in the relaxivity of the agent [113]. Injection of Gd-ATN-10 into rats with 9L gliosarcomas demonstrated an increase in the signal intensity of the tumor. The agent potentially has toxicity problems, though, as it was demonstrated that the metal ions may dissociate from the complex. 

C. Grunzweig, G. Frei, E. Lehmann, G. Kuhne, C. David, Highly absorbing gadolinium test device to characterize the performance of neutron imaging detector systems. Rev. Sci. Instrum. 78, 053708 (2007)... 

Gadolinium 64 Gd Electronic materials, high-temperature refractories, alloys, cryogenic refrigerant, thermal neutron absorber, superconductor, magnetic materials, bubble memory substrates... 

Tokumitsu H, Ichikawa H, Fukumori Y (1999) Chitosan-gadopenteic acid complex nanoparticles for gadolinium neutron-capture therapy of cancer Preparation by novel emulsion-droplet coalescence technique and characterization. Pharm Res 16 1839-1835... 

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