Improved dehydrogenation performance of LiAlH4 doped with BaMnO3.

Due to its high gravimetric capacity of hydrogen (10.5 wt%), LiAlH4 has been regarded as a promising material for solid-state hydrogen storage material for onboard usage. However, high decomposition temperature, poor kinetics and irreversibility retard its application. To counter this problem, various weight percentages of BaMnO3 are introduced into the LiAlH4 system as an additive in this work. As a result, the starting hydrogen release of LiAlH4 was reduced to 109-115 °C and the second desorption temperature occurred at around 134-158 °C, much lower than pure LiAlH4. The isothermal desorption kinetics also proved that faster desorption kinetics can be observed at 90 °C for 80 min. About 2.00-2.60 wt% of H2 could be desorbed by the composite, whereas only <1.00 wt% of H2 was desorbed by undoped LiAlH4. Additionally, adding BaMnO3 reduced the activation energies by 30 kJ/mol for the first stages and 34 kJ/mol for the second stages. Based on the X-ray diffraction result, the active species formed of MnO2 and Ba or Ba-containing materials are believed to be responsible for the noticeable enhancement in the desorption properties of LiAlH4.

Enhancement of the Desorption Properties of LiAlH4 by the Addition of LaCoO3.

The high hydrogen storage capacity (10.5 wt.%) and release of hydrogen at a moderate temperature make LiAlH4 an appealing material for hydrogen storage. However, LiAlH4 suffers from slow kinetics and irreversibility. Hence, LaCoO3 was selected as an additive to defeat the slow kinetics problems of LiAlH4. For the irreversibility part, it still required high pressure to absorb hydrogen. Thus, this study focused on the reduction of the onset desorption temperature and the quickening of the desorption kinetics of LiAlH4. Here, we report the different weight percentages of LaCoO3 mixed with LiAlH4 using the ball-milling method. Interestingly, the addition of 10 wt.% of LaCoO3 resulted in a decrease in the desorption temperature to 70 °C for the first stage and 156 °C for the second stage. In addition, at 90 °C, LiAlH4 + 10 wt.% LaCoO3 can desorb 3.37 wt.% of H2 in 80 min, which is 10 times faster than the unsubstituted samples. The activation energies values for this composite are greatly reduced to 71 kJ/mol for the first stages and 95 kJ/mol for the second stages compared to milled LiAlH4 (107 kJ/mol and 120 kJ/mol for the first two stages, respectively). The enhancement of hydrogen desorption kinetics of LiAlH4 is attributed to the in situ formation of AlCo and La or La-containing species in the presence of LaCoO3, which resulted in a reduction of the onset desorption temperature and activation energies of LiAlH4.

Synthesis and Properties of the Novel High-Performance Hydroxyl-Terminated Liquid Fluoroelastomer.

Functional liquid fluoroelastomers are in high demand in new energy fields. And these materials have potential applications in high-performance sealing materials and as electrode materials. In this study, a novel high-performance hydroxyl-terminated liquid fluoroelastomer (t-HTLF) with a high fluorine content, temperature resistance, and curing efficiency was synthesised from a terpolymer of vinylidene fluoride (VDF), tetrafluoroethylene (TFE), and hexafluoropylene (HFP). A carboxyl-terminated liquid fluoroelastomer (t-CTLF) with controllable molar mass and end-group content was first prepared from a poly(VDF-ter-TFE-ter-HFP) terpolymer using a unique oxidative degradation method. Subsequently, an efficient "one-step" reduction of the carboxyl groups (COOH) in t-CTLF into hydroxyl groups (OH) was achieved via the functional-group conversion method using lithium aluminium hydride (LiAlH4) as the reductant. Thus, t-HTLF with a controllable molar mass and end-group content and highly active end groups was synthesised. Owing to the efficient curing reaction between OH and isocyanate groups (NCO), the cured t-HTLF exhibits good surface properties, thermal properties, and chemical stability. The thermal decomposition temperature (Td) of the cured t-HTLF reaches 334 °C, and it exhibits hydrophobicity. The oxidative degradation, reduction, and curing reaction mechanisms were also determined. The effects of solvent dosage, reaction temperature, reaction time, and ratio of the reductant to the COOH content on the carboxyl conversion were also systematically investigated. An efficient reduction system comprising LiAlH4 can not only achieve an efficient conversion of the COOH groups in t-CTLF to OH groups but also the in situ hydrogenation and addition reactions of residual double bonds (C=C) groups in the chain, such that the thermal stability and terminal activity of the product are improved while maintaining a high fluorine content.

Boosting the Dehydrogenation Properties of LiAlH4 by Addition of TiSiO4.

Given its significant gravimetric hydrogen capacity advantage, lithium alanate (LiAlH4) is regarded as a suitable material for solid-state hydrogen storage. Nevertheless, its outrageous decomposition temperature and slow sorption kinetics hinder its application as a solid-state hydrogen storage material. This research's objective is to investigate how the addition of titanium silicate (TiSiO4) altered the dehydrogenation behavior of LiAlH4. The LiAlH4-10 wt% TiSiO4 composite dehydrogenation temperatures were lowered to 92 °C (first-step reaction) and 128 °C (second-step reaction). According to dehydrogenation kinetic analysis, the TiSiO4-added LiAlH4 composite was able to liberate more hydrogen (about 6.0 wt%) than the undoped LiAlH4 composite (less than 1.0 wt%) at 90 °C for 2 h. After the addition of TiSiO4, the activation energies for hydrogen to liberate from LiAlH4 were lowered. Based on the Kissinger equation, the activation energies for hydrogen liberation for the two-step dehydrogenation of post-milled LiAlH4 were 103 and 115 kJ/mol, respectively. After milling LiAlH4 with 10 wt% TiSiO4, the activation energies were reduced to 68 and 77 kJ/mol, respectively. Additionally, the scanning electron microscopy images demonstrated that the LiAlH4 particles shrank and barely aggregated when 10 wt% of TiSiO4 was added. According to the X-ray diffraction results, TiSiO4 had a significant effect by lowering the decomposition temperature and increasing the rate of dehydrogenation of LiAlH4 via the new active species of AlTi and Si-containing that formed during the heating process.

Hydrogen Desorption Properties of LiBH4/xLiAlH4 (x = 0.5, 1, 2) Composites.

A detailed analysis of the dehydrogenation mechanism of LiBH4/xLiAlH4 (x = 0.5, 1, 2) composites was performed by thermogravimetry (TG), differential scanning calorimetry (DSC), mass spectral analysis (MS), powder X-ray diffraction (XRD) and scanning electronic microscopy (SEM), along with kinetic investigations using a Sievert-type apparatus. The results show that the dehydrogenation pathway of LiBH4/xLiAlH4 had a four-step character. The experimental dehydrogenation amount did not reach the theoretical expectations, because the products such as AlB2 and LiAl formed a passivation layer on the surface of Al and the dehydrogenation reactions associated with Al could not be sufficiently carried out. Kinetic investigations discovered a nonlinear relationship between the activation energy (Ea) of dehydrogenation reactions associated with Al and the ratio x, indicating that the Ea was determined both by the concentration of Al produced by the decomposition of LiAlH4 and the amount of free surface of it. Therefore, the amount of effective contact surface of Al is the rate-determining factor for the overall dehydrogenation of the LiBH4/xLiAlH4 composites.

Fully-automated synthesis of 16ß-(18)F-fluoro-5α-dihydrotestosterone (FDHT) on the ELIXYS radiosynthesizer.

Noninvasive in vivo imaging of androgen receptor (AR) levels with positron emission tomography (PET) is becoming the primary tool in prostate cancer detection and staging. Of the potential (18)F-labeled PET tracers, (18)F-FDHT has clinically shown to be of highest diagnostic value. We demonstrate the first automated synthesis of (18)F-FDHT by adapting the conventional manual synthesis onto the fully-automated ELIXYS radiosynthesizer. Clinically-relevant amounts of (18)F-FDHT were synthesized on ELIXYS in 90 min with decay-corrected radiochemical yield of 29±5% (n=7). The specific activity was 4.6 Ci/µmol (170 GBq/µmol) at end of formulation with a starting activity of 1.0 Ci (37 GBq). The formulated (18)F-FDHT yielded sufficient activity for multiple patient doses and passed all quality control tests required for routine clinical use.

Anticancer activity of ruthenium(II) arene complexes bearing 1,2,3,4-tetrahydroisoquinoline amino alcohol ligands.

Ruthenium complexes offer potential reduced toxicity compared to current platinum anticancer drugs. 1,2,3,4-tetrahydrisoquinoline amino alcohol ligands were synthesised, characterised and coordinated to an organometallic Ru(II) centre. These complexes were evaluated for activity against the cancer cell lines MCF-7, A549 and MDA-MB-231 as well as for toxicity in the normal cell line MDBK. They were observed to be moderately active against only the MCF-7 cells with the best IC50 value of 34 µM for the cis-diastereomeric complex C4. They also displayed excellent selectivity by being relatively inactive against the normal MDBK cell line with SI values ranging from 2.3 to 7.4.