Use Of Lithium Nitrate Research Articles

Effect of Lithium Nitrate Doping on the Phase Composition of Alumina–Chromium Catalysts

The effect of a lithium nitrate (LiNO3) modifying additive on the genesis of the phase composition of alumina–chromium catalysts has been studied using the differential dissolution (DD) and X-ray diffraction (XRD) methods. It has been shown that LiNO3 reacts with a pure support (Al2O3) to form lithium aluminate, double oxide Al4Li2O7 with a spinel structure, and mixed hydroxide LiAl2(OH)7(H2O)2. The reaction of an alumina–chromium catalyst with LiNO3 also leads to the formation of lithium aluminate and double oxide Al4Li2O7; however, a mixed hydroxide is not formed. In addition, the reaction of lithium cations with the Cr(VI) catalyst active component leads to the formation of lithium chromate. A comparative analysis of the phase compositions of alumina–chromium catalysts with LiCl and LiNO3 additives has been conducted. It has been found that, depending on the nature of the additive, the phase composition of the catalyst partially changes. In the case of the introduction of lithium chloride, solid solutions of Cr(III) and Li(I) in alumina are formed; the use of lithium nitrate leads to the formation of double oxide Al4Li2O7 and lithium aluminate. The results of studying the activity of 0.5–3% Li + 9.5% Cr + Al2O3 catalyst samples (Li being introduced from LiCl and LiNO3) have shown that the replacement of the LiCl modifying additive by LiNO3 leads to a change in the catalytic properties of the alumina–chromium catalysts. The activity of the sample doped with lithium nitrate is 4–8% higher than the activity of the sample doped with lithium chloride. This finding can be attributed to the fact that, in the case of the LiNO3 additive, the concentration of the formed active phases Li2CrO4 and Cr2O3 is higher. The selectivities of the catalysts modified with lithium salts (chloride and nitrate) differ only slightly owing to the formation of identical active phases.

Expansive behavior of thick concrete slabs affected by alkali-silica reaction (ASR)

Some of the structures affected by ASR are bridges with thick concrete slabs without shear reinforcement. This implies that concrete is the only component resisting to shear forces, which might be a problem considering that ASR can progressively and significantly affect the mechanical properties of that material. A study was launched to gain a better understanding of the effects of ASR on the behaviour of thick concrete slabs without shear reinforcement. The methodology developed for this study, as well as the analyses of the deformations/expansions obtained from different surface measurements, are presented in this paper. It led to interesting observations about the heterogeneity of the deformations between slabs. The expansion was monitored extensively in the longitudinal, vertical and transversal orientation. The expansion was the greatest in the transversal orientation reaching up to 0.6–0.7%. The steel reinforcement at the base of the specimens locally limited the expansion of the slabs and as such created an expansion gradient which increased with the advancement of the alkali-silica reaction. Also, the use of lithium nitrate proved successful as a mitigation method against the development of expansion due to ASR.

Long-term mitigating effect of lithium nitrate on delayed ettringite formation and ASR in concrete – Microscopic analysis

This paper presents long-term results and microscopic analyses for a six-year experimental study on the effectiveness of lithium nitrate in mitigating delayed ettringite formation (DEF) with or without alkali-silica reaction (ASR). In an associated previous publication, interesting findings were reported showing that lithium nitrate is effective in controlling DEF or combined ASR-DEF mechanisms in concretes.In the present study, microstructural features associated with microcracking and ettringite infilling showed relatively reduced intensity of internal distress and damage when lithium nitrate was admixed in DEF expansive concrete. Microanalyses plotted as Al/Ca versus S/Ca shows that, the use of lithium nitrate leads to formation of non-expansive delayed ettringite similar to normal early-age ettringite formed in moist-cured concretes. These observations give some insights into the mechanism responsible for mitigation of DEF by lithium nitrate.

Lithium-silicate sol\u2013gel bioactive glass and the effect of lithium precursor on structure\u2013property relationships

This work reports the synthesis of lithium-silicate glass, containing 10 mol% of Li_2O by the sol–gel process, intended for the regeneration of cartilage. Lithium citrate and lithium nitrate were selected as lithium precursors. The effects of the lithium precursor on the sol–gel process, and the resulting glass structure, morphology, dissolution behaviour, chondrocyte viability and proliferation, were investigated. When lithium citrate was used, mesoporous glass containing lithium as a network modifier was obtained, whereas the use of lithium nitrate produced relatively dense glass-ceramic with the presence of lithium metasilicate, as shown by X-ray diffraction, ^{29}Si and ^7Li MAS NMR and nitrogen sorption data. Nitrate has a better affinity for lithium than citrate, leading to heterogeneous crystallisation from the mesopores, where lithium salts precipitated during drying. Citrate decomposed at a lower temperature, where the crystallisation of lithium-silicate crystal is not thermodynamically favourable. Upon decomposition of the citrate, a solid-state salt metathesis reaction between citrate and silanol occurred, followed by the diffusion of lithium within the structure of the glass. Both glass and glass-ceramic released silica and lithium ions in culture media, but release rate was lower for the glass-ceramic. Both samples did not affect chondrocyte viability and proliferation.Graphical

Effectiveness of Lithium Nitrate in Mitigating Alkali-Silica Reaction in the Presence of Fly Ashes of Varying Chemical Compositions

AbstractIn this study, quantitative analysis of the combined effects of fly ash and lithium admixture in mitigating alkali-silica reaction (ASR) in portland cement mortars prepared with Spratt limestone was investigated. The results from this investigation suggested that mortar bar expansions could be correlated with specific oxide(s) content in the fly ash through exponential relationships. The dosage of lithium nitrate required for ASR mitigation in mortars containing fly ashes having CaO content less than 23.50% was found to be less than that in the control mortars. Since lithium nitrate was found to be effective in reducing the expansions of control (no fly ash) mortars and mortars containing fly ashes, economic solutions can be obtained in both. However, the use of lithium nitrate was not needed for mortars containing fly ashes having CaO content less than 14.40%. A linear relationship between the oxide content of fly ash and the lithium dosage was found to exist, that can be used to optimize the lit...

Evaluation of Use of Lithium Nitrate in Controlling Alkali-Silica Reactivity in Existing Concrete Pavement

The study presents the findings from a 2-year field trial in which lithium nitrate was applied at a rate of 0.006 gal/ft2 twice a year on an existing concrete pavement in Norfolk, Nebraska, in an attempt to arrest ongoing alkali–silica reaction (ASR) distress. Various destructive and nondestructive means were used to measure the effectiveness of the treatments. Concrete cylinders were cored for petrographic examination and split tension testing. Powder samples were taken to determine the lithium content. Nondestructive evaluations used crack mapping, a Schmidt hammer, a velocity meter, and an impact echo apparatus. The amount of lithium that penetrated into the pavement by gravity soaking has been limited. The results to date have not shown a definitive benefit of application of the lithium material in controlling or mitigating the ASR process; presumably, the pavement has not reached the state of deterioration optimal for lithium penetration. The feasibility and effectiveness of other application techniques on hardened concrete, such as electrolysis, surface pressurization, and vacuum impregnation, should be investigated for comparison with the feasibility and effectiveness of gravity soaking.

Evaluation of Use of Lithium Nitrate in Controlling Alkali-Silica Reactivity in Existing Concrete Pavement

This study presents the findings from a 2-year field trial in which lithium nitrate was applied at a rate of 0.006 gal/ft2 twice a year on an existing concrete pavement in Norfolk, Nebraska, in an attempt to arrest ongoing alkali-silica reaction (ASR) distress. Various destructive and nondestructive means were used to measure the effectiveness of the treatments. Concrete cylinders were cored for petrographic examination and split tension testing. Powder samples were taken to determine the lithium content. Nondestructive evaluations used crack mapping, a Schmidt hammer, a velocity meter, and an impact echo apparatus. The amount of lithium that penetrated into the pavement by gravity soaking has been limited. The results to date have not shown a definitive benefit of application of the lithium material in controlling or mitigating the ASR process; presumably, the pavement has not reached the state of deterioration optimal for lithium penetration. The feasibility and effectiveness of other application techni...

Evaluation of the Use of Lithium Nitrate as a Test Substance for the Determination of the Hold-Up Time of a Reversed-Phase Packing

Abstract The use of lithium nitrate as a test substance for the determination of the hold-up time on μ Bondapak C18 columns has been evaluated by comparison with the hold-up time calculated with the homologous series of n-alcohols. The influence of charge exclusion effects on the retention time of lithium nitrate is investigated. The addition of phosphoric acid to the eluent appears to be an effective method to reduce charge exclusion effects. The existence of deviations from linearity are demonstrated for the homologous series of n-alcohols in eluents with a low methanol content.