Variable-focus microscopy and UV surface dissolution imaging as complementary techniques in intrinsic dissolution rate determination

This work reports a novel approach to the assessment of the surface properties of compacts used in Surface Dissolution Imaging (SDI). SDI is useful for determining intrinsic dissolution rate (IDR), an important parameter in early stage drug development. Surface topography, post-compaction and post-SDI run, have been measured using a non-contact, optical, three-dimensional microscope based on focus variation, the Alicona Infinite Focus Microscope, with the aim of correlating the IDRs to the surface properties. Ibuprofen (IBU) was used as a model poorly-soluble drug. DSC and XRD were used to monitor possible polymorphic changes that may have occurred post-compaction and post-SDI run. IBUs IDR decreased from 0.033 mg/min/cm2 to 0.022 mg/min/cm2 from 10 to 20 min, respectively, during the experiment. XRD and DSC showed no form changes during the SDI run. The surface topography images showed that a distinct imprint was embossed on the surfaces of some compacts which could affect IDRs. Surface parameter values were associated with the SDI experiments which showed strong correlations with the IDR values. The variable-focus microscope can be used as a complimentary tool in the determination of IDR values from the SDI

Biodegradation of the Alkaline Cellulose Degradation Products Generated during Radioactive Waste Disposal.

The anoxic, alkaline hydrolysis of cellulosic materials generates a range of cellulose degradation products (CDP) including α and β forms of isosaccharinic acid (ISA) and is expected to occur in radioactive waste disposal sites receiving intermediate level radioactive wastes. The generation of ISA's is of particular relevance to the disposal of these wastes since they are able to form complexes with radioelements such as Pu enhancing their migration. This study demonstrates that microbial communities present in near-surface anoxic sediments are able to degrade CDP including both forms of ISA via iron reduction, sulphate reduction and methanogenesis, without any prior exposure to these substrates. No significant difference (n = 6, p = 0.118) in α and β ISA degradation rates were seen under either iron reducing, sulphate reducing or methanogenic conditions, giving an overall mean degradation rate of 4.7×10−2 hr−1 (SE±2.9×10−3). These results suggest that a radioactive waste disposal site is likely to be colonised by organisms able to degrade CDP and associated ISA's during the construction and operational phase of the facility

Lithium (De)Intercalation Capacity of Li[sub 1.93]Mn[sub 0.97]Ni[sub 0.10]O[sub 3−δ]

Two compositional factors that control the lithium (de)intercalation capacity of nickel-doped Li2MnO3 have been identified. First is the Ni2+ content and (de)intercalation associated with the Ni2+/4+ redox-active couple. Second is the amount of oxygen deficiency achieved by preparing samples at different temperatures, together with creation of Mn3+ ions for charge balance and (de)intercalation associated with the Mn3+/4+ redox-active couple. Results demonstrating this effect are presented for composition Li1.93Mn0.97Ni0.10O3–. The creation of an oxygen deficiency provides a novel method for enhancing the electrochemical performance of layered, rock-salt structured oxides

Plasma-promoted dielectric heating in the microwave synthesis of spinels

Comparison between the rates of synthesis of the spinel phases (MAl2O4, M = Mg, Zn, Ni; and MFe2O4, M = Mg, Zn, Mn) using an O2 microwave-induced plasma (MIP) and conventional (tube furnace) methods indicate that a MIP promotes microwave dielectric heating at elevated temperatures

Crystal structure and dielectric properties of LaYbO3 ceramics

The crystal structure and dielectric properties of LaYbO3 ceramics prepared by the mixed-oxide route have been investigated. Rietveld refinements performed on X-ray and neutron diffraction data show the room-temperature structure to be best described by the orthorhombic Pnma space group [a=6.02628(9) Å, b=8.39857(11) Å, and c=5.82717(7) Å; Z=4, and theoretical density, Dx=8.1 g/cm3] in agreement with electron diffraction experiments. LaYbO3 ceramics fired at 1600°C for 4 h attain 97% of Dx and their microstructures consist of randomly distributed equiaxed grains with an average size of 8 μm. Conventional transmission electron microscopy shows densification to occur in the absence of a liquid phase and reveals domain-free grains. The relative permittivity, r, of LaYbO3 ceramics at radio frequencies is 26 in the range 10–300 K; however, a small dielectric anomaly is detected at 15 K. At room temperature and microwave frequencies, LaYbO3 ceramics exhibit r 26, Q × fr20 613 GHz (at 7 GHz), and τf−22 ppm/K. Q × fr show complex subambient behavior, decreasing from a plateau value of 20 000 GHz between 300 and 200 K to a second plateau value of 6000 GHz at 90 K before decreasing to <1000 GHz at 10 K. The large decrease in Q × fr at low temperature may be related to the onset of antiferromagnetism at 2.7 K.

Fluorine Intercalation in the n = 1 and n = 2 Layered Manganites Sr2MnO3.5+x and Sr3Mn2O6

Fluorine insertion into the oxygen defect superstructure manganite Sr2MnO3.5+x has been shown by transmission electron microscopy (TEM) to result in two levels of fluorination. In the higher fluorine content sections, the fluorine anions displace oxygen anions from their apical positions into the equatorial vacancies, thus destroying the superstructure and reverting to a K2NiF4-type structure (a = 3.8210(1) Å and c = 12.686(1) Å). Conversely, lower fluorine content sections retain the Sr2MnO3.5+x defect superstructure, crystallising in the P21/c space group. Fluorine intercalation into the reduced double-layer manganite Sr3Mn2O6 occurs in a step-wise fashion according to the general formula Sr3Mn2O6Fy with y = 1, 2, and 3. It is proposed that the y = 1 phase (a = 3.815(1) Å, c = 20.29(2) Å) is produced by the filling of all the equatorial oxygen vacancies by fluorine atoms whilst the y = 2 phase (a = 3.8222(2) Å, c = 21.2435(3) Å) has a random distribution of fluorine anions throughout both interstitial rocksalt and equatorial sites. Neutron powder diffraction data suggest that the fully fluorinated y = 3 phase (a = 3.8157(6) Å, c = 23.666(4) Å) corresponds to the complete occupation of all the equatorial oxygen vacancies and the interstitial sites by intercalated fluorine

Oxygen Vacancy Ordering in the Double-layered Ruddlesden−Popper Cobaltite Sm2BaCo2O7−δ

A new oxygen-deficient Ruddlesden−Popper (RP) cobaltite Sm2BaCo2O7−δ (δ ≈ 1.0) has been synthesized and the crystal structure elucidated by Rietveld analysis of X-ray powder diffraction (XRD) data and transmission electron microscopy (TEM). The phase crystallizes in a primitive orthorhombic unit cell, with lattice parameters a = 5.4371(4) Å; b = 5.4405(4) Å and c = 19.8629(6) Å, and space group Pnnm. Contrary to other oxygen-deficient cobalt RP phases, the oxygen vacancies are located in the equatorial positions of the [CoO] layers to give an intralayer structure similar to Sr2Mn2O5, which is not usually observed for cobalt-containing materials. The Sm3+ and Ba2+ cations show a strong preference for distinct sites, with the majority of the larger Ba2+ cations situated in the perovskite block layers and Sm3+ cations predominantly in the rock salt layers. Magnetic susceptibility data demonstrate the strong antiferromagnetic (AFM) character of Sm2BaCo2O7−δ

A Review of Key Properties of Thermoelectric Composites of Polymers and Inorganic Materials

This review focusses on the development of thermoelectric composites made of oxide or conventional inorganic materials, and polymers, with specific emphasis on those containing oxides. Discussion of the current state-of-the-art thermoelectric materials, including the individual constituent materials, i.e., conventional materials, oxides and polymers, is firstly presented to provide the reader with a comparison of the top-performing thermoelectric materials. Then, individual materials used in the inorganic/polymer composites are discussed to provide a comparison of the performance of the composites themselves. Finally, the addition of carbon-based compounds is discussed as a route to improving the thermoelectric performance. For each topic discussed, key thermoelectric properties are tabulated and comparative figures are presented for a wide array of materials

Synthesis of a neutral metal-organic network solid [(MeIm) Ni(BDC)] (where MeIm = methylimidazole and BDC = 1,4-benzenedicarboxylate) in an ionic liquid solvent 1-methyl-3-propylimidazolium bromide

A new neutral ABC layered metal–organic network [(MeIm)Ni(BDC)] (1) (where MeIm 5 methylimidazole and BDC 5 1,4-benzenedicarboxylate) has been synthesised in the ionic liquid (IL) 1-methyl-3-propylimidazolium bromide without incorporation of IL components into the structure