Diamond irradiation

Several gemstone species occur in various colors, depending on the presence of impurities or irradiation-induced color centers. Examples are the beryl, comndum, and quart2 families. Quart2 has poor optical properties (RI = 1.55, DISP = 0.013), but becomes of gemological interest when it exhibits attractive colors. Any material can have its color modified by the addition of various impurities synthetic mby, sapphires, and spinel are produced commercially in over 100 colors (2). Synthetic cubic 2irconia has been made in essentially all colors of the spectmm (11), but only the colorless diamond imitation is produced commercially in any quantity. 

Some treatments are practiced so widely that untreated material is essentially unknown ia the jewelry trade. The heating of pale Fe-containing chalcedony to produce red-brown carnelian is one of these. Another example iavolves turquoise where the treated material is far superior ia color stabiUty. Such treatments have traditionally not been disclosed. Almost all blue sapphire on the market has been heat treated, but it is not possible to distinguish whether it was near-colorless comndum containing Fe and Ti before treatment, or whether it had already been blue and was only treated ia an attempt at marginal improvement. The irradiation of colorless topa2 to produce a blue color more iatense than any occurring naturally is, however, self-evident, and treatments used on diamond are always disclosed. 

With the exception of diamond coloring and the turning of topa2 blue, the source of the irradiation is immaterial. Gamma rays are the preferred source because of uniformity of coloration and the absence of heating and induced radioactivity. The most commonly seen gemstones enhanced by irradiation are summari2ed in Table 4. 

Venus probe. References should be consulted for the details of the optical transparency of the different type diamonds (9,14,16—19). The direct band gap for diamond is 5.47 eV. Natural diamond exhibits many colors, and color modification by irradiation and annealing is common (36). Though cubic, most natural diamonds show strain birefringence under crossed polaroids. 

Other topics recently studied by XPS include the effects of thermal treatment on the morphology and adhesion of the interface between Au and the polymer trimethylcy-clohexane-polycarbonate [2.72] the composition of the surfaces and interfaces of plasma-modified Cu-PTFE and Au-PTFE, and the surface structure and the improvement of adhesion [2.73] the influence of excimer laser irradiation of the polymer on the adhesion of metallic overlayers [2.74] and the behavior of the Co-rich binder phase of WC-Co hard metal and diamond deposition on it [2.75]. 

Hollomon s ethos, combined with his ferocious energy and determination, and his sustained determination to recruit only the best researchers to join his group, over the next 15 years led to a sequence of remarkable innovations related to materials, including man-made diamond, high-quality thermal insulation, a vacuum circuit-breaker, products based on etched particle tracks in irradiated solids, polycarbonate plastic and, particularly, the Lucalox alumina envelope for a metal-vapour lamp. (Of course many managers besides Hollomon were involved.) A brilliant, detailed account of these innovations and the arrangements that made them possible was later written by Guy Suits and his successor as director, Arthur Bueche (Suits and Bueche 1967). Some of these specific episodes will feature later in this book, but it helps to reinforce the points made here about Hollomon s coneeption of broad research on materials if I point out that the invention of translucent alumina tubes for lamps was... 

Over the last few decades, the use of radiation sources for industrial applications has been widespread. The areas of radiation applications are as follows (i) Wires and cables (ii) heat shrinkable tubes and films (iii) polymeric foam (iv) coating on wooden panels (v) coating on thin film-video/audio tapes (vi) printing and lithography (vii) degradation of polymers (viii) irradiation of diamonds (ix) vulcanization of mbber and rubber latex (x) grain irradiation. 

A. M. Friedman, H. Diamond and J. R. Huizenga Berkelium and Californium isotopes produced in neutron irradiation of Plutonium. Physic, Rev. 96, 1576 (1954). 

Most forms of carbon, except diamond, which are renowned as supports for precious metal catalysts in certain applications [3], interact strongly with MW [4]. Amorphous carbon and graphite, in their powdered form, irradiated at 2.45 GHz, rapidly (within 1 min) reach very high temperatures (>1300 K). This property has been used to explain MW-assisted syntheses of inorganic solids [5], In these syntheses carbon is either a secondary susceptor which assists the initial heating but does not react with other reactants, or is one of the reactants, e. g. in the synthesis of metal carbides. MW-carbon coupling has also been widely developed ... 

In high purity silicon below T = 140 K the Mu center is stable on the time scale of the muon lifetime (2.2 ps). However, in electron irradiated silicon Westhauser et al. (1986) have reported that Mu is metastable and makes a thermally induced transition to Mu at a temperature of 15 K. A similar transition between Mu and Mu was first discovered in diamond (Holz-schuh et al., 1982, Odermatt et al., 1988) and will be discussed in Sec-... 

In all group IV and group III-V crystals in which muonium has been seen, both normal and anomalous muonium occur, with the single exception of SiC. The tetrahedral location for interstitial muonium is metastable in diamond and very likely in unirradiated silicon just as it is in irradiated Si. However at present it is not possible to say whether Mu or Mu is the more stable in Ge, GaAs, and GaP. 

Clayton DD (1989) Origin of heavy xenon in meteoritic diamonds. Astrophys J 340 613-619 Clayton DD, Dwek E, Woosley SE (1977a) Isotopic anomalies and proton irradiation in the early solar system. Astrophys J 214 300-315... 

Fig. 11 Plot of the fraction (Pg) vs natural logarithm of time in min as a function of temperature. The fraction is relative to the total initial radicals formed in irradiated hydrated solid samples of MX-DNA (14 D20/nucleotide, v=l/214) 4 K (empty circles), 11 K (filled triangles), 130 K (filled upside down triangles), 150 K (filled diamonds), 170 K (filled circles), 195 K (filled squares) [7c]. Reprinted with permission from the J. Phys. Chem. Copyright (2000) American Chemical Society...

Diamonds represent measured data collected under all sky conditions. The solid line represents the UV (290-325 am) irradiance calculated at local noon by means of the STAR model for cloud-free conditions as described in [5]. Climatological values of the model input parameters for both stations are used (Table 1). 

The sketched lines represent the uncertainty of the modelled UV values ( 7.2% according to [6]). Diamonds included in the shaded area represent clear sky measurements. The mean percent difference between measured and computed irradiances is -1.5% at Rome and -1.4% at Ispra for clear sky conditions, respectively (the standard deviation is 3.9% for both sites). 

The curve marked by a DOT represents the bleaching effect of alkaline hydrogen peroxide. The difference in the absorption coefficient at 457 nm is about -2.0 m2/kg and associated with an increase of 4.1 in the ISO brightness as the result of peroxide bleaching. Upon y irradiation of an alkaline hydrogen peroxide bleached pulp (P-TMP), one still attacks the phenolic hydroxyl groups or coniferaldehyde groups around 350 nm as indicated by the curved marked with a DIAMOND. 

---