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Browsing by Author "Kong, L"

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Aqueous chemical synthesis of Ln2Sn2O7 pyrochlore-structured ceramics
(John Wiley and Sons, 2013-06-03) Kong, L; Karatchevtseva, I; Blackford, MG; Scales, N; Triani, G
Pyrochlore-structured lanthanide stannate ceramic (Ln2Sn2O7) has been synthesized via a new complex precipitation method. A suite of characterization techniques, including FTIR, Raman, X-ray, and electron diffraction as well as nitrogen sorption were employed to investigate the structural evolution of the synthesized and calcined powder. Raman, XRD, and selected area electron diffraction results confirm the presence of the pyrochlore structure after calcination of the powder above 1200°C. TEM imaging shows fine crystallites gradually increased in size from approximately 100 nm to about 500 nm with higher calcination temperatures. Grain growth and powder densification upon increasing the calcination temperature was confirmed by nitrogen sorption results. This aqueous synthetic method provides a simple pathway for the preparation of homogeneous lanthanide stannate ceramics. © 2013, The American Ceramic Society.
Crystal chemistry and ion-irradiation resistance of Ln2ZrO5 compounds with Ln = Sm, Eu, Gd, and Tb
(John Wiley & Sons, Inc, 2021-12-22) Aughterson, RD; Lumpkin, GR; Zhang, ZM; Avdeev, M; Kong, L
The previously unattained fabrication of single phase Ln2ZrO5 (Ln = Sm, Eu, Gd, and Tb) compounds via relatively low sintering temperature (1400°C) is achieved in this study using a coprecipitation method. The crystal structures have been investigated by neutron, synchrotron X-ray powder diffraction, and electron diffraction techniques. While the general long-range structure may be well described by the defect-fluorite type structure with Fm3m symmetry, electron diffraction has highlighted a complex underlying modulated structure that varies between each compound. These compounds have been tested for ion-irradiation response using in situ 1 MeV krypton ions and transmission electron microscopy characterization. None of the compounds undergo a crystalline to amorphous transition, even holding at 50 K. Both the underlying fluorite and modulated superstructures are little affected by the irradiation. However, some atomic rearrangements are observed in the postirradiated electron diffraction patterns for the Sm2ZrO5 specimen. © 2021 Commonwealth of Australia.
Current advances on titanate glass-ceramic composite materials as waste forms for actinide immobilization: a technical review
(Elsevier, 2022-05) Zhang, YJ; Kong, L; Ionescu, M; Gregg, DJ
As the emerging versatile waste forms for immobilizing actinide-rich radioactive wastes, glass-ceramic composite materials based on some durable ceramic phases are being developed. They have apparent advantages over the conventional borosilicate glasses and multi- or single- phase ceramics as they essentially combine the chemical and processing flexibilities of glasses to accommodate processing impurities and excellent chemical durability of ceramic phases to host actinides. More recently, some new advances have been made on scientific and technological aspects including new glass-ceramic systems; improved understanding of ceramic phase evolution in glass; actinide validation studies and simplified processing techniques. This review is intended to cover the current advances on the development of glass-ceramic composite waste forms focusing on titanate ceramic phases (zirconolite, pyrochlore and brannerite) for immobilizing various actinide-rich radioactive wastes arising from the nuclear fuel cycle. © 2021 Published by Elsevier Ltd.
Dioxo-vanadium(V), oxo-rhenium(V) and dioxo-uranium(VI) complexes with a tridentate Schiff base ligand
(Royal Society of Chemistry, 2016-08-03) Zhang, YJ; Fanna, DJ; Shepherd, ND; Karatchevtseva, I; Lu, KT; Kong, L; Price, JR
The complexation of a julolidine–quinoline based tridentate ligand with three oxo-metal ions, dioxo-vanadium(V), oxo-rhenium(V) and dioxo-uranium(VI), has been investigated with four new complexes being synthesised and structurally characterised. (VO2L)·2/3H2O (1) {HL (C22H21N3O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} has a VO2L neutral mononuclear structure with a five-fold coordinated vanadium metal centre in a distorted trigonal bipyramidal geometry. (ReOL2)2(ReCl6)·7DMF (2) [DMF = dimethylformamide] exhibits a mixed valent rhenium complex with a (ReOL2)+ cationic unit in a distorted octahedral metal coordination geometry, charge balanced with (ReCl6)2− anions. [(UO2)L(H2O)2]2·2(NO3)·HL·4H2O (3) and [(UO2)L(CH3OH)2](NO3)·CH3OH (4) both have (UO2L)+ cationic mononuclear structures with either coordinated water or methanol molecules in pentagonal bipyramidal coordination geometries for the uranium metal centres. Intra-/intermolecular interactions including hydrogen bonding and π–π interactions are common and have been discussed. In addition, optical absorption and photoluminescence properties have been investigated. © 2016 The Royal Society of Chemistry
Gd2Zr2O7 and Nd2Zr2O7 pyrochlore prepared by aqueous chemical synthesis
(Elsevier, 2013-12-01) Kong, L; Karatchevtseva, I; Gregg, DJ; Blackford, MG; Holmes, R; Triani, G
Pyrochlore structured Gd2Zr2O7 and Nd2Zr2O7 are produced via complex precipitation processing. A suite of characterization techniques, including FTIR, Raman, X-ray and electron diffraction, TEM, SEM as well as nitrogen sorption are employed to investigate the structural and grain size evolution of the synthesized and calcined powder. Results show that Gd2Zr2O7 with the pyrochlore structure are produced after calcination at 1400 °C for 12 h while Nd2Zr2O7 has already formed the pyrochlore structure at 1200 °C. This method allows the formation of dense materials at relatively low temperature, with bulk densities over 92% of the theoretical values achieved after sintering at 1400 °C for 50 h. This unique aqueous synthetic method provides a simple pathway to produce pyrochlore lanthanide zirconate without using either organic solvent and/or mechanical milling procedures, making the synthesis protocol an attractive potential scale-up production of highly refractory ceramics. © 2013, Elsevier Ltd.
Neodymium coordination polymers with propionate, succinate and mixed succinate–oxalate ligands: synthesis, structures and spectroscopic characterization
(Elsevier, 2015-12-14) Scales, N; Zhang, YJ; Bhadbhade, MM; Karatchevtseva, I; Kong, L; Lumpkin, GR; Li, F
Three neodymium (Nd) coordination polymers with propionate, succinate and mixed succinate–oxalate ligands have been synthesized and structurally characterized. Nd2(C3H5O2)6(H2O)3·3H2O (1) has a 1D polymeric structure built with both ninefold and ten-fold coordinated neodymium polyhedra linked through μ2-bridging propionate ligands. Nd2(C4H4O4)3(H2O)2 (2) has a 3D polymeric structure constructed with two distinct ninefold coordinated neodymium polyhedra linked through three types of succinate ligands, two in μ4- and one in μ3-coordination modes. Nd2(C4H4O4)2(C2O4)(H2O)4·3H2O (3) is built with two types of ten-fold coordinated neodymium polyhedra linked through μ4-succinate ligands into 2D undulating layers which are further connected through μ2-oxalate ligands forming a 3D network with channels. Their vibrational modes and thermal stabilities have been further investigated. Crown Copyright © 2015 Published by Elsevier Ltd.
New pathway for the preparation of pyrochlore Nd2Zr2O7 nanoparticles
(Elsevier B.V., 2015-07-01) Kong, L; Karatchevtseva, I; Aughterson, RD; Davis, J; Zhang, YJ; Lumpkin, GR; Triani, G
Pyrochlore Nd2Zr2O7 nanoparticles were prepared by complex-precipitation in aqueous media, followed by calcination in MgO matrix and subsequent dissolution processing. A suite of characterization techniques, including X-ray diffraction, Raman, TEM, SEM, dynamic light scattering, and nitrogen sorption, was employed to investigate the structure and particle size of the synthesized nano materials. Results show that calcination at 1200 °C for 20 h forms Nd2Zr2O7 with pyrochlore structure. The matrix phase (MgO) had no effect on the formation of pyrochlore phase. The MgO phase was readily removed by dissolution at 0.5 M HNO3 aqueous solution; and the remaining pyrochlore Nd2Zr2O7 nanoparticles had a diameter of approximately 200 nm estimated by TEM and approximately 550 nm determined by light scattering due to slight aggregation. The bulk density of the pelletized powder reached approximately 99% of theoretical value, after uniaxial pressing at 2.0–2.5 MPa and sintering at 1400 °C for 48 h. © 2015 Elsevier B.V.
New synthesis route for lead zirconate titanate powder
(Elsevier, 2016-05-01) Kong, L; Karatchevtseva, I; Holmes, R; Davis, J; Zhang, YJ; Triani, G
Phase pure lead zirconate titanate (PZT) powder was produced via a new aqueous coprecipitation method. A suite of characterization techniques, including FTIR, Raman, X-ray diffraction, SEM as well as nitrogen sorption were employed to investigate the structural evolution of the synthesized and calcined powder. The dried precipitate formed in aqueous phase yielded approximately 80 wt% final product after calcination. The PZT perovskite structure was obtained after calcination at 550 °C for 3 h. Milling of the calcined powder reduced the mean particle size from approximately 10 µm to 2 µm. With increasing calcination temperature from 550 °C to 700 °C, both surface area and pore volume decreased while pore size increased from 3.4 nm to 9.8 nm. The bulk density of pelletized samples increased from 4.83 to 7.57 g/cm3 with increasing sintering temperature from 800 °C to 1200 °C. Powder processing using this aqueous route is simple and reproducible leading to a method that is readily scalable for industrial applications. © 2016 Elsevier Ltd.
A novel chemical route to prepare La2Zr2O7 pyrochlore
(John Wiley and Sons, 2012-11-09) Kong, L; Karatchevtseva, I; Gregg, DJ; Blackford, MG; Holmes, R; Triani, G
Lanthanum zirconate has been prepared via a new chemical synthesis method by combining sol–gel processing and complex precipitation. The synthesis was carried out in aqueous solution under ambient conditions. The synthesized powder possessed the pyrochlore superstructure upon calcination above 1200°C. A suite of characterization techniques, including FTIR, Raman, X-ray and electron diffraction, TEM, SEM, and nitrogen sorption were employed to investigate the microstructural evolution and bulk properties. Dense ceramics (>90% relative density) were obtained after sintering at 1400°C, without need for additional processing (i.e., hot or cold isostatic pressing) or any milling steps. A mechanism has been proposed that elucidates molecular assembly of this chemical synthesis method. © 2012, The American Ceramic Society.
Novel chemical synthesis and characterization of CeTi2O6 brannerite
(ACS Publications, 2014-06-13) Kong, L; Gregg, DJ; Karatchevtseva, I; Zhang, ZM; Blackford, MG; Middleburgh, SC; Lumpkin, GR; Triani, G
Cerium titanate CeTi2O6 was prepared by a new soft chemistry route in aqueous solution. A suite of characterization techniques, including X-ray diffraction, thermal analysis, vibrational spectroscopy, and scanning and transmission electron spectroscopy, were employed to investigate the brannerite structure formation and its bulk properties. The synthesized powder formed the brannerite crystal structure upon calcination at temperatures as low as 800 °C. Samples sintered at 1350 °C possess a high level of crystallinity. X-ray absorption near-edge structure results indicate the presence of six-coordinated Ce4+ in the brannerite samples. © 2014, American Chemical Society.
Novel synthesis and thermal property analysis of MgO–Nd2Zr2O7 composite
(Elsevier, 2016-11-15) Kong, L; Zhang, J; Maeda, Y; Blackford, MG; Li, S; Triani, G; Gregg, DJ
MgO-Nd2Zr2O7composites with ratios of 50–70 vol% MgO were produced via a one-pot combustion synthesis. A suite of characterization techniques, including X-ray diffraction, scanning and transmission electron microscopy were employed to investigate the structural properties while dilatometry, simultaneous thermal analysis and laser flash analysis were used to characterize the thermal properties of the composites. Dense pellets were produced after sintering at 1400 °C with grain sizes between 200 and 500 nm for both phases. The thermal properties of the composites are similar to those produced using standard methods. The composite with 70 vol% MgO was found to have the highest thermal conductivity below 1000 °C, while above this temperature the thermal conductivity was found to be similar and independent of MgO content. This novel synthesis route produces materials which show significant improvements in homogeneity with smaller particle sizes when compared to current standard synthesis techniques without significantly reducing thermal conductivity. © 2016 Elsevier Ltd.
One-dimensional uranium(VI) coordination polymers with pyridinecarboxylate ligands
(Elsevier B.V., 2016-07-27) Shepherd, ND; Zhang, YJ; Karatchevtseva, I; Price, JR; Kong, L; Scales, N; Lumpkin, GR
A method to produce picolinate ligand in situ under hydrothermal conditions has been used to synthesize four uranyl hydroxyl, oxo- and oxohydroxyl picolinato complexes. (UO2)(OH)(Pic) (1) (HPic = picolinic acid) contains 7-fold coordinated uranyl hydroxyl dimers linked through μ2-bridging Pic ligands forming a one-dimensional (1D) polymer. (NH4)[(UO2)3(O)2(OH)(Pic)2] (2) consists of 7-fold coordinated uranyl oxohydroxyl trinuclear units linked through both μ2- and μ3-Pic ligands forming a 1D polymer. (NH4)[(UO2)2(O)2(Pic)] (3) is constructed with 7-fold coordinated uranyl oxo-dinuclear units linked through oxo- and μ3-Pic ligands forming a 1D polymer. (NH4)[(UO2)4(O)2(OH)2(Pic)2(INT)]·H2O (4) (HINT = isonicotinic acid) is made of 7-fold coordinated uranyl oxohydroxyl tetranuclear units linked through both Pic and INT ligands forming a 1D polymer. All four polymers are thermal robust to 350 °C. Raman spectroscopy confirmed the presence of uranyl ion and Pic ligand. In addition, red enhanced fluorescence emissions have been observed for both 1 and 4. The synthesis method, with the advantage of controlling uranyl hydrolysis and generating ligand in situ, provides a more reliable way to make new coordination polymers of carboxylate ligands with various uranyl hydrolysis species. © 2016 Elsevier Ltd.
Optimizing radiolabeling amine-functionalized silica nanoparticles using SarAr-NCS for applications in imaging and radiotherapy
(American Chemical Society, 2013-05-07) Kong, L; Mume, E; Triani, G; Smith, SV
Silica nanoparticles functionalized with amine groups and in the size range of approximately 60–94 nm were produced by combining sol–gel processing and emulsion technology. Hexa-aza cage ligand SarAr-NCS was conjugated to the silica nanoparticles and subsequently radiolabeled with a solution of 57Co2+-doped carrier Co2+. The number of Co2+ ions bound to the silica particles at pH 7 was used to determine the average number of available SarAr-NCS ligands conjugated to a silica particle. For organically modified silica particles of 94.0 and 59.5 nm diameter, the maximum number of metal binding sites was determined to be 11700 and 3270 sites per particle, respectively. For silica particles (63.5 nm peak diameter) produced using an water-in-oil emulsion, the calculated average was 4480 on the particle surface. The number of SarAr-NCS conjugated on the particles was easily controlled, potentially providing for a range of products for applications in the risk assessment of particles and theranostic imaging or radiotherapy when radiolabeled with a suitable radioisotope such as 64Cu or 67Cu. © 2013, American Chemical Society.
Phase assemblage and microstructures of Gd2Ti2-xZrxO7 (x = 0.1–0.3) pyrochlore glass-ceramics as potential waste forms for actinide immobilization
(Elsevier, 2021-11-15) Bhuiyan, A; Wong, V; Abraham, JL; Aughterson, RD; Kong, L; Farzana, R; Gregg, DJ; Sorrell, CC; Zhang, YJ; Koshy, P
Glass-ceramics (GCs) based on titanate pyrochlores have attracted recent attention as candidate waste forms for actinide immobilization. As zirconate pyrochlore has a superior radiation resistance, it is anticipated that Zr substitution of Ti in titanate pyrochlore GCs would increase their potential for waste form applications. The concept was primarily addressed via the preparation of Gd2Ti2-xZrxO7 (x = 0.1–0.3) GCs to determine the effects of sintering temperature, Zr substitution, and pyrochlore content (50–70 wt%) on the properties of the resultant GCs. XRD and SEM analyses were used to reveal the phase assemblages and microstructures while TEM and Raman spectroscopy were used to analyze the local structures. XRD results confirmed the formation of the targeted pyrochlore as the major phase, with Gd9.33(SiO4)6O2 oxyapatite present as a minor phase. SEM analyses revealed that up to 0.2 formula units of Ti could be substituted by Zr under the processing conditions. The pyrochlore crystallite sizes were largely controlled by the sintering temperature and cooling rate and showed little sensitivity to the glass contents. This work has demonstrated successful substitutions of Ti with Zr in Gd2Ti2O7 GCs as potential waste forms for actinide wastes owing to their superior radiation resistance. © 2021 Elsevier B.V.
Preparation of Y2Ti2O7 pyrochlore glass-ceramics as potential waste forms for actinides: the effects of processing conditions
(Elsevier B.V., 2017-09-30) Kong, L; Zhang, YJ; Karatchevtseva, I
Glass-Y2Ti2O7 pyrochlore was fabricated by sintering the mixture of glass precursor powder and (YTi)-composite which was prepared by a soft chemistry route. X-ray diffraction and Raman spectroscopy confirmed that the phase pure pyrochlore was crystallized in-situ in amorphous glass matrix at 1200 °C with dwelling time over 1 h. Pyrochlore was formed in glass matrix with cooling rate ∼0.1–40 °C/min, and independent of addition of alkali/alkaline earth fluorides. Glass matrix was able to accommodate/dissolve small amounts of impurities and the mean pyrochlore particle size was between 1 and 2 μm in glass observed by scanning electron microscopy. © 2017 Elsevier B.V.
Pyrochlore glass‐ceramics fabricated via both sintering and hot isostatic pressing for minor actinide immobilization
(John Wiley & Sons, Inc., 2020-03-19) Zhang, YJ; Zhang, ZM; Wei, T; Kong, L; Kim, YJ; Gregg, DJ
Pyrochlore glass‐ceramics (GCs) have been investigated with samples fabricated via both sintering and hot isostatic pressing (HIPing) of a mixed oxide precursor. It has been demonstrated that sintering at 1200°C in air is necessary to obtain well‐crystallized pyrochlore crystals in a sodium aluminoborosilicate glass through a one‐step controlled cooling. The crystallization, structure, and microstructure of Eu2Ti2O7 pyrochlore as the major phases in residual glass were confirmed with X‐ray diffraction (XRD), scanning electron microscopy‐energy dispersive spectroscopy, transmission electron microscopy, and Raman spectroscopy. The structures of major Eu2Ti2O7 pyrochlore and minor [Eu4.67O(SiO4)3] apatite in both sintered and HIPed samples were refined using synchrotron XRD data. While the processing atmosphere did not appear to affect the cell parameter of the main pyrochlore phase, very small volume expansion (~0.3%) was observed for the minor apatite phase in the HIPed sample. In addition, static leaching of the HIPed sample confirmed that pyrochlore GCs are chemically durable. Overall, pyrochlore GCs prepared via both sintering and HIPing with the Eu partitioning factor of ~23 between ceramics and the residual glass are suitable waste forms for minor actinides with processing chemicals. © 1999-2020 John Wiley & Sons, Inc.
Soft chemical synthesis and structural characterization of Y2HfxTi2−xO7
(Elsevier, 2015-05-04) Kong, L; Shang, Z; de los Reyes, M; Lumpkin, GR; Triani, G; Aughterson, RD; Karatchevtseva, I
A novel soft chemistry route was developed to synthesize Y2HfxTi2−xO7 (0≤x≤2.0) oxide solid solution. An aqueous solution containing reactants was produced to ensure the combustion reaction taking place at the molecular level. A suite of characterization techniques, including X-ray diffraction, Raman, transmission electron spectroscopy, as well as X-ray absorption near edge structure (XANES), is employed to investigate the structural and phase changes of the series. Both X-ray and electron diffraction patterns show that the Y2HfxTi2−xO7 system undergoes a clear composition-induced phase transition from ordered pyrochlore to disordered defect-fluorite at x~1.5. On the other hand, Raman and XANES spectra reveal a gradual evolution of the local structure with the substitution of Hf for Ti. © 2014 Elsevier Ltd and Techna Group S.r.l.
Sol-gel microspheres and nanospheres for controlled release applications
(Australian Nuclear Science and Technology Organisation, 2002-04-29) Barbé, CJ; Beyer, R; Kong, L; Blackford, MG; Trautman, RL; Bartlett, JR
We present a novel approach to the synthesis of inorganic sol-gel microspheres for encapsulating organic and bioactive molecules, and controlling their subsequent release kinetics.The bioactive species are incorporated, at ambient temperature, into the inorganic particles using an emulsion gelation process, Independent control of the release rate (by adapting the nanostructure of the internal pore network to the physico-chemical properties of the bioactive molecules) and particle size (by tailoring the emulsion chemistry) is demonstrated.
Synthesis and characterization of Nd2SnxZr2−xO7 pyrochlore ceramics
(Elsevier, 2014-01) Kong, L; Zhang, YJ; Karatchevtseva, I; Blackford, MG; Lumpkin, GR; Triani, G
Pyrochlore structured Nd2SnxZr2−xO7 (x=0–2) ceramics were prepared by a new chemical synthesis route in an aqueous media. Raman spectra and X-ray diffraction patterns confirmed the formation of the pyrochlore structure after sintering at 1400 °C. SEM results showed pelletized materials became dense with increasing Zr/Sn mole ratio and sintering temperature. These candidate materials have characteristic structures for the development of nuclear waste forms or inert matrix nuclear fuels.© 2013, Elsevier Ltd and Techna Group S.r.l.
Synthesis of hexa aza cages, SarAr-NCS and AmBaSar and a study of their metal complexation, conjugation to nanomaterials and proteins for application in radioimaging and therapy
(Royal Society of Chemistry, 2013-07-01) Mume, E; Asad, A; Di Bartolo, NM; Kong, L; Smith, C; Sargeson, AM; Price, R
A novel hexa aza cage, N1-(4-isothiocyanatobenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane-1,8-diamine (SarAr-NCS) was synthesized in good yield and characterized by 1H NMR and electrospray mass spectrometry. A new method for the synthesis of the related N1-(4-carboxybenzyl)-3,6,10,13,16,19-hexaazabicyclo[6.6.6]icosane-1,8-diamine (AmBaSar) using the p-carboxybenzaldehyde is reported. The complexation of Cu2+, Co2+ and Zn2+ by the two ligands over a range of pHs was found to be similar to the parent derivative SarAr. SarAr-NCS was conjugated to both silica particles (≈90 nm diam.) and the model B72.3 murine antibody. The SarAr-NCSN-silica particles were radiolabeled with Cu2+ doped 64Cu and the number of ligands conjugated was calculated to be an average of 7020 ligands per particle. Conjugation of SarAr-NCS to the B72.3 antibody was optimized over a range of conditions. The SarAr-NCSN-B72.3 conjugate was stored in buffer and as a lyophilized powder at 4 °C over 38 days. Its radiolabeling efficiency, stability and immunoreactivity were maintained. The development of a high yielding synthesis of SarAr-NCS should provide an entry point for a wide range of Cu and Zn radiometal PET imaging agents and potentially radiotherapeutic agents with 67Cu. © 2013, The Royal Society of Chemistry.

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