Yttrium Aluminosilicate Research Articles

A yttrium aluminosilicate glass fiber with graded refractive index fabricated by melt‐in‐tube method

AbstractA graded‐index fiber with yttrium aluminosilicate (YAS) glass core was fabricated by a “Melt‐in‐Tube” method. The refractive index and stress profiles of the fibers exhibit a highly symmetrical gradient tendency along the radial axis which is in accordance with the results of element migration. Based on the formation mechanism of YAS glass core, the relationships between the refractive index/stress profile and the spontaneous migration are discussed. A linear all‐fiber laser based on the obtained fiber shows a laser output threshold of 11.48 mW and slope efficiency of 8.3%. The near‐field beam intensity distribution of fiber laser with spectrum FWHM of 0.24 nm indicates the good laser beam quality. The facile “Melt‐in‐tube” method was proved to be reliable in designing graded‐index fiber through the dissolution and diffusion process, which is more advanced than commonly used “Rod‐in‐tube” method.

Preparation and characterizations of Yb:YAG-derived silica fibers drawn by on-line feeding molten core approach

Three Yb:YAG transparent ceramics with Yb2O3 doping concentrations of 1, 10, and 15at%, respectively were made into silica-clad hybrid fibers using an on-line feeding molten core approach. The diffusion of silica was mitigated such that the lowest SiO2 concentration was 36.4wt%, and consequently, the Yb2O3 content could reach 8.93wt% in the fiber core. The fiber core transformed from a YAG ceramic to an yttrium aluminosilicate glass, and the formation of abundant Q2 silicate species implied that the structure of the core glass maintained some environments similar to that of YAG with Q2–AlO4 tetrahedra. The absorption and emission spectra of the obtained fibers were compared to those of Yb:YAG ceramics, and the self-absorption effect was analyzed in detail. All three fibers could output lasers under 940 or 970nm pumping. The maximum output power of the Yb:YAG-derived fibers was higher than that of ceramic wafers owing to the cladding pump technology, which offered a new method to improve the application of ceramics.

MCharacteristics of Carbon Tetrafluoride Plasma Resistance of Various Glasses

Etch rate, surface roughness and microstructure as plasma resistance were evaluated for six kinds of oxide glass with different compositions. Borosilicate glass (BS) was found to be etched at the highest etch rate and zinc aluminum phosphate glass (ZAP) showed a relatively lower etch rate than borosilicate. On the other hand, the etching rate of calcium aluminosilicate glass (CAS) was measured to be similar to that of sintered alumina while yttrium aluminosilicate glass (YAS) showed the lowest etch rate. Such different etch rates by mixture plasma as a function of glass compositions was dependent on whether or not fluoride compounds were formed on glass and sublimated in high vacuum. Especially, in view that CaF₂ and YF₃ with high sublimation points were formed on the surface of CAS and YAS glasses, both CAS and YAS glasses were considered to be a good candidate for protective coating materials on the damaged polycrystalline ceramics parts in semi-conductor and display processes.

Joining technology—A challenge for the use of SiC components in HTRs

The availability of suitable joining technologies is paramount to the further advancement of ceramic components and their use in HTRs. Among other joining technologies, a modified brazing technology using a laser beam for heating the components to be joined has been developed at TU Dresden.The laser-induced heating behavior of the ceramic material is determined by the interactions between the material and the laser beam. This was shown in two different silicon carbide materials (SSiC and SiCf-reinforced ceramic material) using a diode laser with wavelengths 808nm and 940nm.The laser-based technique was illustrated by three different examples: sealing of monolithic SiC with a pin configuration for fuel claddings, sealing of SiC heat pipes with a length of 1m, and demonstration of the transferability of the laser technique to fiber-reinforced components by means of a SiCf/SiCN material.Because the covalent bonding of SiC does not allow conventional welding, much research has been devoted to developing alternative filler systems. Glass or glass–ceramic fillers enable the tailoring of properties such as CTE and viscosity. Glasses are thermally stable up to their glass transition temperatures. It was shown that the crystallization of the yttrium aluminosilicate glass composition of the present work allows it to be used at 1050°C without any significant changes occurring in braze tightness. For the SiC heat pipes with sodium as the working fluid, a sodium-resistant metal braze consisting of Ni–Ti–Si was formed. The long-term resistance of this filler to sodium at 800°C was proven. The results demonstrate the possibility of using the laser-based joining technique for the joining of different SiC materials as well as for different brazing materials.

A silica optical fiber doped with yttrium aluminosilicate nanoparticles for supercontinuum generation

We design and fabricate a silica optical fiber doped with yttrium aluminosilicate (YAS, Y2O3–Al2O3–SiO2) nanoparticles in the core. The optical fiber is drawn directly from a silica tube with YAG (Y3Al5O12) ceramics and silica powders (the molar ratio 1:18) in the core at the temperature of ∼1950°C. The YAS nanoparticles are formed during the optical fiber drawing process. Supercontinuum (SC) generation in the optical fiber is investigated at different pump wavelength. At the pump wavelength of ∼1750nm which is in the deep anomalous dispersion region, SC spectrum evolution is mainly due to multiple solitons and dispersive waves (DWs), and three pairs of multiple optical solitons and DWs are observed. When the pump wavelength shifts to ∼1500nm which is close to the zero-dispersion wavelength (ZDW), flattened SC spectrum with ±7dB uniformity is obtained at the wavelength region of ∼990–1980nm, and only one obvious soliton and DW are observed. At the pump wavelength of ∼1100nm, a narrow SC spectrum from ∼1020 to 1180nm is obtained in the normal dispersion region due to self-phase modulation (SPM) effect.

Contribution of di- and trivalent oxides to crystal phase formations and properties of yttrium aluminosilicate glass-ceramics

The crystallization behaviour, phase composition, microhardness and chemical durability of some silicate glasses and glass-ceramics based on LiAlSi2O6-YAlSiO5 system were investigated. The effects of partial replacements of LiAlSi2O6 mostly with LiFeSi2O6 and complete replacement of YAlSiO5 with CaMgSi2O6 were considered. In some cases small amount of Cr2O3 was introduced as nucleating agent or Fe2O3 was partially replaced with chromium or indium oxides. The main crystalline phases formed after controlled heat-treatments of the glasses were yttrium-containing ?-spodumene solid solution (ss) - Li(Al,Y)Si2O6, together with varieties of pyroxene-ss including lithium iron pyroxene-ss - LiFeSi2O6-CaMgSi2O6, augite - Ca(Mg,Fe)Si2O6, chromoaugitess, Li-aegirine - LiFeSi2O6, diopside - CaMgSi2O6 and lithium indium silicate - LiInSi2O6 phases. The Vickers? microhardness values of the studied glasses (ranged from 4610 to 6185MPa) were greatly affected by the modifications of the glass compositions. On the other hand, the glass-ceramics? microhardness (7245- 8175MPa) was markedly improved depending on the microstructure and the nature of crystalline phases formed. The glass-ceramics have chemical stability better than those for the corresponding glasses.

Y3Al5O12–SiO2 Glasses: Structure and Polyamorphism

Aerodynamic levitation and CO2 laser melting have been used to synthesize the yttrium aluminosilicate glasses zY2O3–yAl2O3–xSiO2 with z/y = 3/5 corresponding to the YAG (Y3Al5O12) composition and x between ~5 and ~45 mol%. The low‐ and high‐density (LDA inclusion and HDA matrix) polyamorphic phases in glasses with less than ~14 mol% SiO2 were identified with backscattering electron imaging. Polarized and depolarized Raman spectra show the formation of various Qn SiO4 species whose relative populations change smoothly as the SiO2 content is altered. The AlOs (s = 4–6) and YOz (z = 6–9) polyhedra formed in the YAG glass are preserved upon silica additions while the terminal oxygens of the Q2AlO4 tetrahedra are gradually bridged to the Qn‐SiO4 species. The low‐frequency Boson Peak overlaps with the vibrational spectrum and its maximum is redshifted with increasing silica content. Micro‐Raman spectra measured for the LDA and HDA amorphous phases are found to be similar to the spectra of the bulk glass indicating common structural characteristics. The stability of the LDA phase against crystallization appears to be lower than that of the HDA phase. The crystallinity on certain inclusions consisted of YAG microcrystals and a new unidentified microcrystalline phase within Y4Al2(1−x)Si2xO(9+x) solid solution.

Localized Hyperthermia with Iron Oxide–Doped Yttrium Microparticles: Steps toward Image-Guided Thermoradiotherapy in Liver Cancer

PurposeTo test whether iron oxide (IO)–containing yttrium aluminosilicate (YAS) microparticles (MPs) can generate localized therapeutic hyperthermia (≥ 43°C) when injected intratumorally in an animal model of liver cancer and whether MP distributions could be visualized with magnetic resonance (MR) imaging. Materials and MethodsTwenty-one Sprague–Dawley rats implanted with N1-S1 liver tumors were assigned to alternating magnetic field (AMF) exposure following intratumoral injection with IO-YAS MPs (n = 7), sham surgery (n = 7), or baseline iron quantification (n = 7). Three fiberoptic probes allowed spatial and temporal monitoring of temperatures during 24 minutes of AMF exposure. T2-weighted turbo spin-echo MR imaging was performed within 1 hour after the procedure to detect signal voids caused by IO-YAS deposition. Hematoxylin and eosin–stained pathologic slides were also obtained, and the presence of IO-YAS was evaluated with inductively coupled plasma optical emission spectroscopy. ResultsFollowing AMF exposure, intratumoral temperatures after IO-YAS MP injection achieved therapeutic hyperthermia whereas those after sham surgery did not (46.6°C ± 1.3 vs 36.8°C ± 0.4; P < .0001). Within the treated group, the normal hepatic parenchyma (NHP) and rectal temperatures were 37.4°C ± 0.9 and 36.5°C ± 1.0 (P = .0809) at the conclusion of AMF exposure, respectively. A T2-weighted signal void at the tumor site was observed in all seven treated animals, and intratumoral IO-YAS was visualized on subsequent histopathologic examination in each case. The mean ratio of tumor:NHP Fe concentrations attributable to IO-YAS MPs was 108:1. ConclusionsAMF exposure of intratumoral IO-YAS MPs generates localized therapeutic hyperthermia in an animal model of liver cancer. MR detectability and potential for combination brachytherapy warrants further investigation for thermoradiotherapy in liver cancer.

Hydration Effects on the Structural and Vibrational Properties of Yttrium Aluminosilicate Glasses for in Situ Radiotherapy

The performances of silicate glasses as containment matrices or vectors of radioactive ions in nuclear waste storage and in situ radiotherapy are influenced by the effect of interstitial water on the glass durability. In order to assess how hydration determines changes to atomistic structural features which control the glass degradation, we have carried out molecular dynamics simulations of a typical yttrium aluminosilicate (YAS) glass employed in radiotherapy, incorporating different water contents. The analysis of the models allows us to discuss the way in which hydroxyl groups are distributed in the glass structure and modify or disrupt the aluminosilicate glass network. Hydration affects the silicate and aluminate connectivity to a different extent, resulting in a different degree of disruption (depolymerization) of the Si and Al network. The simulations also highlight a strong tendency of all hydrated compositions to form Y(3+)- and OH(-)-rich domains, separated from the aluminosilicate matrix. The implications of these structural effects for the durability and ion release behavior of the glass are discussed, as well as the vibrational signatures of the various hydrous species identified in the models.

Dehydroxilation and crystallization of glasses: A DTA study

Differential thermal analysis (DTA) is a technique frequently used for the study of the crystallization kinetics of glass powders during sintering. The effect of specific surface area on crystallization kinetics has been reported earlier. It has been shown that there is a shift in the DTA crystallization peaks towards lower temperatures for smaller particle size. This paper analyzes how the dehydroxilation endothermic peaks that appear in DTA measurements depend on specific area and on the heating rate. Experiments were done on yttrium aluminosilicate, samarium aluminosilicate and soda-lime silica glasses, slabs and powders. We found that some of them exhibit a dehydroxilation endothermic peak that overlaps at different extent with the crystallization peak. The dehydroxilation peak is not detected when yttrium aluminosilicate glass powder is preheated at melting temperatures, or its surface is previously hydrated. For the yttrium aluminosilicate glass a dehydroxilation apparent activation energy of 255±50kcalmol−1 was obtained using the Kissinger plot.

EBSD and EDX Analyses of a Multiphase Glass-Ceramic Obtained by Crystallizing an Yttrium Aluminosilicate Glass

A glass with the mol % composition 23.82 Y2O3·39.82 Al2O3·28.50 SiO2·2.91AlF3·4.95 ZrO2 doped with 2 mol % CeF3 is crystallized at 1250 °C for 20 h. The crystallized samples are studied using X-ray diffraction (XRD), the SEM-based methods EBSD and EDX, as well as fluorescence microscopy. Six crystalline phases are detected in the residual glass including alumina, YAG, Y-stabilized zirconia (YSZ), and three different yttrium silicates of the composition Y2Si2O7. Chemistry-assisted indexing (ChI) is successfully applied to separate YAG and YSZ in EBSD-scans. YAG displays polygon as well as dendritic growth. Some crystals show both mechanisms at opposite ends, indicating that the growth mechanism is influenced by the chemistry of the surrounding glass matrix.

High-temperature stability of laser-joined silicon carbide components

Silicon carbide is recommended for applications in energy technology due to its good high-temperature corrosion resistance, mechanical durability, and abrasion resistance. The prerequisite for use is often the availability of suitable technologies for joining or sealing the components. A laser-induced process using fillers and local heating of the components represents a possible low-cost option.Investigations in which yttrium aluminosilicate glass was used for laser-induced brazing of SiC components of varying geometry are presented. A four-point bending strength of 112MPa was found for these joints. In burst tests, laser-joined components were found to withstand internal pressures of up to 54MPa.Helium leak tests yielded leak rates of less than 10–8mbarls−1, even after 300h at 900°C. In contrast, the assemblies showed an increased leak rate after annealing at 1050°C.The short process time of the laser technique – in the range of a few seconds to a few minutes – results in high temperature gradients and transients. SEM analysis showed that the filler in the seam predominantly solidifies in a glassy state. Crystallization occurred during later thermal loading of the joined components, with chemical equilibrium being established. Differences in seam structures yielded from different cooling rates in the laser process could not be equalized by annealing.The results demonstrated the long-term stability of laser-brazed SiC assemblies to temperatures in the range of glass transformation (900°C) of the yttrium aluminosilicate filler. In technological investigations, the suitability of the laser joining technique for sealing of SiC components with a geometry approximating that of a fuel element sleeve pin (pin) in a gas-cooled fast reactor was proven.

Crystallization of Yttrium and Samarium Aluminosilicate Glasses

Abstract Aluminosilicate glasses containing samarium and yttrium (SmAS and YAS glasses) exhibit high glass transition temperatures, corrosion resistance, and glass stability on heating which make them useful for technological applications. Yttrium aluminosilicate glass microspheres are currently being used for internal selective radiotherapy of liver cancer. During the preparation process, crystallization needs to be totally or partially avoided depending on the final application. Thus knowing the crystallization kinetics can help to prevent or avoid it, by designing a proper thermal pathway. In this work we studied the crystallization kinetics of YAS and SmAS glasses. It was found that both, YAS and SmAS glasses crystallize from the surface. SmAS glass presented lower densities of nucleation sites. The results also showed that the crystal growth apparent enthalpy is larger for SmAS glasses.

Molecular Dynamics Simulations and Structural Descriptors of Radioisotope Glass Vectors for In Situ Radiotherapy

The low solubility (high durability) of yttrium aluminosilicate (YAS) glass is one of its most important properties for use in in situ radiotherapy. Simple parameters, such as silica or yttria content or network connectivity, are not sufficient to rationalize the dependence of the solubility on the glass composition observed experimentally. We performed classical molecular dynamics (MD) simulations of eight different YAS glasses of known solubility and analyzed the MD trajectories to identify specific structural features that are correlated and can be used to predict the solubility. We show that the (Si-)O-Si coordination number CN(SiOSi), the yttrium-yttrium clustering ratio R(YY), and the number of intratetrahedral O-Si-O bonds per yttrium atom N(intra) can be combined into a single structural descriptor s = f(CN(SiOSi),R(YY),N(intra)) with a high correlation with the solubility. The parameter s can thus be calculated from MD simulations and used to predict the solubility of YAS compositions, allowing one to adjust them to the range required by radiotherapy applications. For instance, its trend shows that high-silica- and low-yttria-content YAS glasses should be sufficiently durable for the radiotherapy application, although additional clinical considerations may set a lower limit to the yttria content.

Glassy microspheres with elevated yttrium oxide content for nuclear medicine

Yttrium aluminosilicate (YAS) glasses with yttrium oxide content to 23 % (molar content) have been made and their properties studied. Microspheres with diameter 20 – 32 μm for use in brachytherapy have been made. These microspheres are characterized by a completely amorphous structure with high shape isometry (particle asphericity < 5 %), high chemical stability, and no crystalline inclusions.

Structural rearrangement at the yttrium-depleted surface of HCl-processed yttrium aluminosilicate glass for 90Y-microsphere brachytherapy

The design of a process to create yttrium aluminosilicate microspheres with a core–shell structure is of interest in the field of cancer brachytherapy. Glass microspheres with yttrium-depleted shell may indeed reduce the risk of 90Y release into the organism. Here we show – by means of confocal micro-Raman scattering, microfluorescence, X-ray-fluorescence analysis, and IR spectroscopy – that yttrium depletion may be achieved by etching in HCl solution (pH 2) at a rate of 1μmday−1 in bulk glass and 3μmday−1 in glass microsphere (35μm of diameter). Importantly, the spectroscopic results – collected in confocal configuration along the processed layer – indicate a high degree of structural reconstruction of the glass network, with the formation of an interconnected silicate-rich glass that surrounds a core of unmodified yttrium aluminosilicate. We also demonstrate that the process is driven by non-bridging oxygen sites, which regulate the hydroxylation and structural reconstruction of the glass within the Y-depleted layer. The analysis gives also some insight into open fundamental questions about the short-range structure and the chemical stability of this kind of glass, which is also important in photonics and nuclear waste disposal.

Production and Characterization of Glass Microspheres for Hepatic Cancer Treatment

A simple theoretical mathematical model was developed to assess the process of glass particles spheroidization in a propane-butane-oxygen flame. The model has been designed to gain a better understanding of the dependency amongst the variables that come into play during glass spheroidization. Using the model and theoretical values of: glass viscosity, density, shear modulus, thermal conductivity as well as measured values of the temperature of the flame at different positions, particle size and the vitreous transition temperature, the particle«s time-temperature history was calculated inside the flame for different particle sizes and trajectories. For yttrium aluminosilicate (YAS) glass microspheres, of diameter size: 20-50 microns, it was found that the spheroidization process is completed within the flame in short time intervals in the order of 4 x 10-3 to 9 x 10-3seconds, depending on its thermal trajectory and size of the particle. In this paper the trajectories, degree of spheroidization, temperature variations and velocities of different particle sizes are shown. Using the results obtained from the model, YAS glass microspheres were produced and characterized. Density measurements were done using Helium Pycnometry, chemical composition was studied by Energy Dispersive Spectroscopy. The microsphere surface was characterized using Scanning Electron Microscopy and the glass was thermally characterized by means of Differential Thermal Analysis.

Crystallization of an Yttrium Aluminosilicate Glass for Nuclear Waste Immobilization

ABSTRACTSiO2-Al2O3-Y2O3 glasses exhibit high glass transition temperatures, water corrosion resistance and good mechanical properties. These properties suggest that yttrium aluminosilicate glasses could potentially replace the borosilicate glasses usually used for immobilization of nuclear wastes. At the same time, yttrium can be used to simulate actinides.During waste immobilization, crystallization of the glassy matrix must be avoided or at least controlled, thus, the understanding of glass crystallization kinetics is essential.We found by XRD that the crystalline phases present on heat treatments are yttrium disilicate and sillimanite/mullite. By optical microscopy on polished cross-sections we could only identify highly yttrium enriched crystals which we associate with yttrium disilicate crystals.In this paper we measure the surface density of nucleation sites Ns in as obtained splat cooled pieces obtaining values of about 1.5 · 1011 nucleus · m-2. Crystal growth rate U in the temperature range 1000-1040 oC varies in the range 8-13 μm · h-1. These data are useful for designing sintering or melting thermal paths of YAS glasses in order to control their microstructure. We show the effect of glass particle size on DTA results: crystallization peaks moves towards lower temperatures for smaller particle size, which confirms that mainly surface nucleation is taking place on heating.

Chemical interaction of yttrium aluminosilicate glass with CeO 2, UO 2 and PuO 2 at high temperatures

The thermal interaction of yttrium aluminosilicate glass with cerium, plutonium and uranium oxides at temperatures up to 1200 °C has been studied by means of differential scanning calorimetry (DSC), X-ray diffraction (XRD), and secondary electron microscopy (SEM). The glass, a candidate for joining and sealing advanced fuel cladding materials, such as silicon carbide (SiC), undergoes a recrystallization process above 1000 °C providing a mixture that exhibits two melting points at 1379 and 1410 °C. Samples containing glass and actinide oxide mixtures did not form new phases, nor did the actinide oxides influence the recrystallization behavior of the glass.

Er- and Nd-doped yttrium aluminosilicate glasses: Preparation and characterization

The undoped, and Nd-, Er-doped low silica high alumina yttrium aluminosilicate (YAS) glasses were prepared by flame synthesis in the form of transparent glass microbeads with diameters ranging from a few to several tens of micrometers. The silica content ranged between 5 and 20 mol.%. The prepared glass microbeads were characterized by optical microscopy, SEM XRD, FT-IR and UV–VIS–NIR spectroscopy. The glass forming ability of glasses, expressed in terms of the difference between the glass transition temperature, T g, and the onset of crystallization, T x, improved with increasing silica content. Doping of YAS15 glass with neodymium or erbium at the level of 1–5 mol.% leads to decrease of both the T g and T x. However, the glass forming ability was not affected. The UV–VIS–NIR reflectance spectra in the spectral range from 300 to 1800 nm shows characteristic absorptions, due to the optically active Nd 3+ and Er 3+ ions in the host glass.