Untitled

Digeos, A. A.; Valdez, James A.; Sickafus, Kurt E.; Atiq, S.; Grimes, Robin W.; Boccaccini, A. R.

doi:10.1023/a:1023242702644

Cited by 77 publications

(52 citation statements)

References 19 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[29] Given the above scientific and technical background and experience, it seems sensible to consider the development of novel radioactive waste forms based on the combined concepts of encapsulation in an inert vitreous matrix and immobilization in pyrochlore phases. [30] This approach leads to glass matrix composites characterized by an inert silicate matrix with a more radiation resistant crystalline pyrochlore phase acting as the host phase for certain fission products, in particular, actinides such as Pu. [31] This approach is different from previous developments [23±28] in that here the primary immobilization is achieved in the pyrochlore phase, which is then encapsulated in a suitable glass matrix.…”

mentioning

confidence: 99%

“…[31] This approach is different from previous developments [23±28] in that here the primary immobilization is achieved in the pyrochlore phase, which is then encapsulated in a suitable glass matrix. As such, the type of waste form proposed, [30] based on immobilization of waste in a pyrochlore phase, may find particular use with certain weapons-based legacy waste. Nevertheless, if a suitably durable glass could be identified, the composite may accommodate other shorter-lived fission products (e.g., Cs and I) in that glass.…”

mentioning

confidence: 99%

“…[2,3] In a previous study, [30] we demonstrated the fabrication of La 2 Zr 2 O 7 pyrochlore-glass composites by powder technology and sintering. However, the final composites retained significant residual porosity (10 %), which was detrimental to the mechanical strength, structural integrity, and chemical durability of the components.…”

mentioning

confidence: 99%

“…[34] We described the preparation of the lanthanum zirconate powder from commercial powders of La 2 O 3 (Alpha Aesar 99.99 % purity) and ZrO 2 (Alpha Aesar 99.978 % purity) previously. [30] The morphology of the lanthanum zirconate powder used to fabricate the composites is shown in Figure 1a.…”

mentioning

confidence: 99%

See 3 more Smart Citations

Hot‐Pressed Glass Matrix Composites Containing Pyrochlore Phase Particles for Nuclear Waste Encapsulation

Boccaccını¹,

Atiq

Grimes

2003

Adv Eng Mater

View full text Add to dashboard Cite

0.5, including trishydroxymethylaminomethane, 50 and HCl, 45 in mL), a new calcium phosphate phase such as hydroxyapatite forms on their surfaces. [18] Hydroxyapatite formation on the glass-ceramic coating surfaces after soaking was confirmed by XRD analysis and SEM observation. Figure 5 shows SEM images of the coating surfaces after 20 days of soaking at 37 C. No newly formed products are seen in the image of the 50CaO-40P 2 O 5 -7Na 2 O-3TiO 2 glass-ceramic coating surface, but numerous depositions of leaf-like particles are seen in that of the 60CaO-30P 2 O 5 -7Na 2 O3TiO 2 glass-ceramic coating surface. In the XRD pattern of the later sample, broad peaks due to hydroxyapatite around 2h = 32 and about 25.8 (Cu Ka) appeared. This result implies that the glass-ceramic coating might show bioactivity in vivo.The reason why hydroxyapatite forms only on the 60CaO-30P 2 O 5 -7Na 2 O-3TiO 2 glass-ceramic coating surface is not clear yet. It was suggested that glassy phases in the glass-ceramics play an important role in their in vitro bioactivity. [17] In the 60CaO-30P 2 O 5 -7Na 2 O-3TiO 2 glass-ceramic, all of Ti element is included in the glassy phase. [17] Although the glassy phase is gradually dissolved in SBF to release ions such as Ca 2+ , Na + , and P 5+ , no Ti 4+ ions are released. The Ti 4+ ions may be present at around the surface of the glass-ceramic to form a hydroxyl group such as Ti±OH, which is an inducer for the apatite formation in SBF. [18] On the other hand, in the 50CaO-40P 2 O 5 -7Na 2 O-3TiO 2 glass-ceramic, crystalline (Ca 0.5 ,-Na)Ti 2 (PO 4 ) 3 phase having high chemical durability [19] is precipitated as shown in Figure 2; a trace amount of Ti element would be included in the glassy phase. No inducing group for the apatite formation such as Ti±OH may form on the surface of the glass-ceramic. The mechanism for the formation of the apatite on the coating layer is under investigation.In summary, fine, strong coatings of silica-free calcium phosphate glass-ceramic containing crystalline b-Ca 3 (PO 4 ) 2 and b-Ca 2 P 2 O 7 phases were prepared easily by reaction of the glassy phase with an oxide layer formed on b-Ti-29Nb-13Ta-4.6Zr alloy during heating at 800 C for one hour in air. These coatings had high tensile bonding strengths of 20±25 MPa. Phosphate reaction layers several micrometers thick developed on the alloy and the glass-ceramic layers were strongly bonded to the melt with the substrate. In vitro bioactivity tests showed that 60CaO-30P 2 O 5 -7Na 2 O-3TiO 2 glass-ceramic coating is bioactive. The glass-ceramic has high potential for use as bioactive coatings on b-titanium alloys.

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Hot‐Pressed Glass Matrix Composites Containing Pyrochlore Phase Particles for Nuclear Waste Encapsulation

Boccaccını¹,

Atiq

Grimes

2003

Adv Eng Mater

View full text Add to dashboard Cite

show abstract

“…[4][5][6] It has gained widespread research attention due to its remarkable properties like very high thermal stability, low sintering, low thermal conductivity, no permeability of oxygen and excellent stability. [6][7][8] Preparation of this material has been done through solidstate reaction [9][10][11][12] and other wet-chemistry-based routes, which include co-precipitation, 12,13) sol-gel process, 12,14,15) hydrazine 16) and citrate methods.…”

Section: Introductionmentioning

confidence: 99%

Physicochemical Properties of Single Phase La2Zr2O7 Powder

2005

View full text Add to dashboard Cite

Powders of La 2 O 3 and ZrO 2 in ethanol based suspension were planetary ball milled at 200 rpm for 12 hours, dried and then heat treated at 1500 C for one hour to synthesize single phase of La 2 Zr 2 O 7 which is a very promising thermal barrier coating material. Planetary milling results to particle diminution together with an increase in surface area with increasing milling time as investigated by FE-SEM, particle size analyses and BET method. The formation of single phase La 2 Zr 2 O 7 with pyrochlore structure was confirmed by X-ray diffraction and TEM analyses. DSC investigation on the milled powders revealed the dehydroxylation reaction at around 320 C and complete disintegration of ethanol including decarboxylation at around 500 C. The absence of these peaks in the thermal plot for the single phase material confirms its thermal stability at 1500 C sintering temperature.

show abstract

Glass Matrix Composite

Bernardo

2011

Wiley Encyclopedia of Composites

View full text Add to dashboard Cite

Glass and glass–ceramic matrix composites represent a very particular type of composite materials. As in most ceramic matrix composites, the reinforcements are mainly intended to increase the resistance to crack propagation, that is, the most significant weakness of the matrices, due to several toughening mechanisms. Unlike polycrystalline ceramic matrices, however, glasses offer the distinctive feature of viscous flow, being readily deformed and flowed in their low viscosity state, with the possibility of incorporating secondary phases at moderately high temperatures. Fibrous reinforcements (mainly C and SiC fibers) are at the basis of materials with impressive properties, for example, strength above 1 GPa, fracture toughness up to 35 MPa m 0.5 , almost zero thermal expansion, and service temperature up to 1500°C, but still facing high costs, although known for many years. Recent applications, such as that of “optomechanical materials,” that is, transparent materials with improved crack resistance, may stimulate research investments and production. As an alternative, dispersion‐reinforced composites, first seen as lower value category, owing to the limited improvements in fracture toughness, are currently the candidates for extensive industrial production, since the low cost treatments applied may be combined with complex combinations of different functionalities.

show abstract

Untitled

Cited by 77 publications

References 19 publications

Hot‐Pressed Glass Matrix Composites Containing Pyrochlore Phase Particles for Nuclear Waste Encapsulation

Hot‐Pressed Glass Matrix Composites Containing Pyrochlore Phase Particles for Nuclear Waste Encapsulation

Physicochemical Properties of Single Phase La<SUB>2</SUB>Zr<SUB>2</SUB>O<SUB>7</SUB> Powder

Glass Matrix Composite

Contact Info

Product

Resources

About