Aluminum Nanoparticles as the Energy Source for Multi-Sample Mars Return Mission

Gold nanoparticles (AuNPs) were attached to the surface of alumina particles by an in-situ immobilizing method. SEM and XPS analysis showed that the coverage of alumina particles by AuNPs increased as the amount of alumina decreased; AuNPs onto alumina particles by the conventional colloidal deposition method were also prepared, whose TEM showed that the coverage of AuNPs was evidently smaller than that in the case of modified colloidal deposition method，although the AuNPs were spread almost uniformly over the surface of alumina particles. Au-immobilized alumina particles were subsequently utilized as the catalysts for direct amination of benzene with NH3H2O as an aminating agent and H2O2 as an oxidant under mild conditions. The reaction conditions were optimized: when catalyst amount was 2.0 g, reaction temperature was 50 °C, NH3H2O amount was 60 mL, H2O2 amount was 30 mL, and reaction time is 2 h, Au-immobilized alumina particles showed the highest aniline yield (1.96 mg) for 25 mL benzene.

Ignition of single nickel-coated aluminum particles

Colloidal processing is an effective and reliable approach in the fabrication of the advanced ceramic products. Successful colloidal processing of fine ceramic powders requires accurate control of the rheological properties. The accurate control relies on the understanding the influences of various colloidal parameters on the rheological properties. Almost all research done on the rheology paid less attention to the interactions of particle and solvent. However, the interactions of the particles are usually built up through the media in which the particles are suspended. Therefore, interactions of the particle with the media, the adsorbed layers on the particle surface, and chemical and physical properties of media themselves must influence the rheology of the suspension, especially for the dense suspensions containing nanosized particles. Relatively little research work has been reported in this area. This thesis addresses the rheological properties of nanometric alumina aqueous suspensions, and paying more attention to the interactions between particle and solvent, which in turn influence the particle-particle interactions. Dense nanometric alumina aqueous suspensions with low viscosity were achieved by environmentally-benign fructose additives. The rheology of nanometric alumina aqueous suspensions and its variation with the particle volume fraction and concentration of fructose were explored by rheometry. The adsorptions ofmore » solute (fructose) and solvent (water) on the nanometric alumina particle surfaces were measured and analyzed by TG/DSC, TOC, and NMR techniques. The mobility of water molecules in the suspensions and its variation with particle volume fractions and fructose additive were determined by the {sup 17}O NMR relaxation method. The interactions between the nanometric alumina particles in water and fructose solutions were investigated by AFM. The results indicated that a large number of water layers were physically bound on the particles' surfaces in the aqueous suspension. The viscosity of the suspension increases dramatically when the solid volume fraction exceeds 30 vol.%. The overlap of physically adsorbed water layers at this level causes the sharp increase in viscosity. Fructose molecules can weaken the interactions between the particle surfaces and water molecules, as a consequence, they release some bound water layers from the surfaces to the bulk medium. It is believed that fraction of the water that is bound by the solid surface is reduced hence becoming available for flow. The oxygen-17 relaxation time decreased with the increase of particle volume fractions in the suspension. Fructose addition increased the overall water mobility in the suspension. Only part of the alumina particle surfaces was covered with fructose molecules. This adsorption of fructose molecules on the particle surfaces increased the pH of the suspension with a concomitant decrease in {zeta}-potential of the alumina nanoparticles. The interactions between the nanometric alumina particles in water to a large extent can be explained by the DLVO theory. However, the interactions between particles in fructose solutions cannot be well described by the DLVO theory. The interaction forces (magnitude and range) as well as adhesive force and surface tension between nanometric alumina particles were decreased with the fructose concentration.« less

In this study, aluminium pigments were encapsulated with hydroxyl group‐containing acrylic resin after surface acid treatment to enhance their adhesive performance in the paint film. The removal efficiency of fatty acid on surface of aluminium particles was studied by means of thermogravimetric analysis and the effect of acid treatment on adhesive performance of aluminium pigments encapsulated with hydroxyl group‐containing acrylic resin in the paint film was investigated by pulling‐off tests. It was found that fatty acid on surface of aluminium particles was removed efficiently by acid ethanol solution, and then hydroxyl group‐containing acrylic resin can be encapsulated onto the surface of the aluminium particles by chemisorptions. The encapsulated aluminium pigments have excellent adhesive performance in the paint film. © 2011 Canadian Society for Chemical Engineering

Abstract. Recent studies have suggested that injection of solid particles such as alumina and calcite particles for stratospheric aerosol injection (SAI) instead of sulfur-based injections could reduce some of the adverse side effects of SAI such as ozone depletion and stratospheric heating. Here, we present a version of the global aerosol–chemistry–climate model SOCOL-AERv2 and the Earth system model (ESM) SOCOLv4 which incorporate a solid-particle microphysics scheme for assessment of SAI of solid particles. Microphysical interactions of the solid particle with the stratospheric sulfur cycle were interactively coupled to the heterogeneous chemistry scheme and the radiative transfer code (RTC) for the first time within an ESM. Therefore, the model allows simulation of heterogeneous chemistry at the particle surface as well as feedbacks between microphysics, chemistry, radiation and climate. We show that sulfur-based SAI results in a doubling of the stratospheric aerosol burden compared to the same mass injection rate of calcite and alumina particles with a radius of 240 nm. Most of the sulfuric acid aerosol mass resulting from SO2 injection does not need to be lifted to the stratosphere but is formed after in situ oxidation and subsequent water uptake in the stratosphere. Therefore, to achieve the same radiative forcing, larger injection rates are needed for calcite and alumina particle injection than for sulfur-based SAI. The stratospheric sulfur cycle would be significantly perturbed, with a reduction in stratospheric sulfuric acid burden by 53 %, when injecting 5 Mt yr−1 (megatons per year) of alumina or calcite particles of 240 nm radius. We show that alumina particles will acquire a sulfuric acid coating equivalent to about 10 nm thickness if the sulfuric acid is equally distributed over the whole available particle surface area in the lower stratosphere. However, due to the steep contact angle of sulfuric acid on alumina particles, the sulfuric acid coating would likely not cover the entire alumina surface, which would result in available surface for heterogeneous reactions other than the ones on sulfuric acid. When applying realistic uptake coefficients of 1.0, 10−5 and 10−4 for H2SO4, HCl and HNO3, respectively, the same scenario with injections of calcite particles results in 94 % of the particle mass remaining in the form of CaCO3. This likely keeps the optical properties of the calcite particles intact but could significantly alter the heterogeneous reactions occurring on the particle surfaces. The major process uncertainties of solid-particle SAI are (1) the solid-particle microphysics in the injection plume and degree of agglomeration of solid particles on the sub-ESM grid scale, (2) the scattering properties of the resulting agglomerates, (3) heterogeneous chemistry on the particle surface, and (4) aerosol–cloud interactions. These uncertainties can only be addressed with extensive, coordinated experimental and modelling research efforts. The model presented in this work offers a useful tool for sensitivity studies and incorporating new experimental results on SAI of solid particles.

Adsorption of a Low-Molecular-Weight Polyacrylic Acid on Silica, Alumina, and Kaolin

Much attention has been focused on hydrometallurgical routes to recover valuable metals from spent Li-ion batteries (LIBs). A lot of works has demonstrated that this method is an effective approach toward the recovery of a large panel of metals constituting LIBs and particularly the positive electrode material. Despite the large number of studies on hydrometallurgical processes for LIBs recycling, the phenomenon taking place during positive electrode material dissolution remains unknown. Different behaviors are observed during active material of positive electrode dissolution in literature. The interest of using a reducing agent to favor material dissolution is underlined. However, a partial dissolution of such material can be achieved without reducing agent in the leachate. The aim of this study is to explain such dissolution in absence of reductive agent. LIBs represent an active research field in which alternative positive electrode materials are developed to replace LiCoO2 due to cobalt cost and safety issues. The solution found is to substitute partially or totally the cobalt by other transition metals such as nickel or manganese: LiFePO4 (LFP), LiNi1/3Mn1/3Co1/3O2 (NMC), LiNi0.8Co0.15A0.05O2 (NCA), and LiMn2O4 (LMO). In this study, we chose the representative LiNi1/3Mn1/3Co1/3O2 (NMC) material which contains the most common elements found in LIBs. This active material has good overall performance and excels on specific energy, which makes it a very good candidate for the electric vehicles, and it has the lowest self-heating rate. This work is dedicated to a kinetic study of the dissolution reaction in acidic media. The relation between structural changes and dissolution mechanism is studied during the dissolution evolution. The surface composition analyses of residual particles (during the dissolution) are performed by X-ray photoelectron spectrometry (XPS), high-resolution transmission electron microscopy (HRTEM), electron dispersive X-ray (EX) spectrometry mapping and X-ray diffraction. Regarding the dissolution mechanism some electrochemical experiments allows to precise redox reactions taking place at the interface. The limitations of NMC dissolution in acidic media are also identified. The results show two different steps of dissolution with different sources of limitation. During the first step, there is no change on the surface of particles between 5 and 15 minutes of dissolution (step 1). After 18 hours of dissolution represents the beginning of the second dissolution step. The results reveal the beginning of surface enrichment in manganese. X-ray diffraction analysis demonstrates that the rich manganese phase is composed by MnO2. This crystalline phase is located on the surface of particles and creates during the dissolution. At the end of the second dissolution step (43 days), the HRTEM images and EDX mapping reveal a growth of a rich manganese phase on the NMC surface particles under MnO2 needles form. The structural study performed by microscopy, spectroscopy and X-rays diffraction reveals the surface of NMC particles is free from a neoformed phase at the end of the first step. Thus, this step is not limited by the formation of a surface passivation film at the interface between the NMC material and the dissolution solution. The electrochemical results and the thermodynamic approach demonstrate a dissolution controlled by the material delithiation. Regarding the second step, all the previous results indicate the formation of MnO2 on the surface of NMC particles. To highlight the chemical reactions involved during the second dissolution phase, the particular behavior of manganese is investigated. The results indicate that the addition of manganese to the dissolution solution allows to reactivate the dissolution of nickel and cobalt contained in the NMC material. It highlights that the oxidation of manganese under MnO2 form is linked with nickel and cobalt dissolution from NMC material. The dissolution can be reactivated after MnO2 layer formation on the surface of NMC particles. So, the stopping of the NMC dissolution is not related to a surface passivation by MnO2 layer. The stopping of the dissolution coincide with the Mn2+ depletion. Finally, the results allow defining new ways of treatment in reducing the energy requirements and the addition of reducing species. Figure 1

Much attention has been focused on hydrometallurgical routes to recover valuable metals from spent Li-ion batteries (LIBs). A lot of works has demonstrated that this method is an effective approach toward the recovery of a large panel of metals constituting LIBs and particularly the positive electrode material. Despite the large number of studies on hydrometallurgical processes for LIBs recycling, the phenomenon taking place during positive electrode material dissolution remains unknown. Different behaviours are observed during active material of positive electrode dissolution in literature. The interest of using a reducing agent to favour material dissolution is underlined. However, a partial dissolution of such material can be achieved without reducing agent in the leachate. The aim of this study is to explain such dissolution in absence of reductive agent. LIBs represent an active research field in which alternative positive electrode materials are developed to replace LiCoO2 due to cobalt cost and safety issues. The solution found is to substitute partially or totally the cobalt by other transition metals such as nickel or manganese: LiFePO4 (LFP), LiNi1/3Mn1/3Co1/3O2 (NMC), LiNi0.8Co0.15A0.05O2 (NCA), and LiMn2O4 (LMO). In this study, we chose the representative LiNi1/3Mn1/3Co1/3O2 (NMC) material which contains the most common elements found in LIBs. This active material has good overall performance and excels on specific energy, which makes it a very good candidate for the electric vehicles, and it has the lowest self-heating rate. This work is dedicated to a kinetic study of the dissolution reaction in acidic media. The relation between structural changes and dissolution mechanism is studied during the dissolution evolution. The surface composition analyses of residual particles (during the dissolution) are performed by X-ray photoelectron spectrometry (XPS), high-resolution transmission electron microscopy (HRTEM), electron dispersive X-ray (EX) spectrometry mapping and X-ray diffraction. Regarding the dissolution mechanism some electrochemical experiments allows to precise redox reactions taking place at the interface. The limitations of NMC dissolution in acidic media are also identified. The results show two different steps of dissolution with different sources of limitation. During the first step, there is no change on the surface of particles (cf. attachment HRTEM images and EDX mapping: B) between 5 and 15 minutes of dissolution (step 1). After 18 hours of dissolution represents the beginning of the second dissolution step. The results reveal the beginning of surface enrichment in manganese. X-ray diffraction analysis demonstrates that the rich manganese phase is composed by MnO2. This crystalline phase is located on the surface of particles and creates during the dissolution. At the end of the second dissolution step (43 days), the figure (cf. attachment HRTEM images and EDX mapping: D) reveals a growth of a rich manganese phase on the NMC surface particles under MnO2 needles form. The structural study performed by microscopy, spectroscopy and X-rays diffraction reveals the surface of NMC particles is free from a neoformed phase at the end of the first step. Thus, this step is not limited by the formation of a surface passivation film at the interface between the NMC material and the dissolution solution. The electrochemical results and the thermodynamic approach demonstrate a dissolution controlled by the material delithiation. Regarding the second step, all the previous results indicate the formation of MnO2 on the surface of NMC particles. To highlight the chemical reactions involved during the second dissolution phase, the particular behaviour of manganese is investigated. The results indicate that the addition of manganese to the dissolution solution allows to reactivate the dissolution of nickel and cobalt contained in the NMC material. It highlights that the oxidation of manganese under MnO2 form is linked with nickel and cobalt dissolution from NMC material. The dissolution can be reactivated after MnO2 layer formation on the surface of NMC particles. So, the stopping of the NMC dissolution is not related to a surface passivation by MnO2 layer. The stopping of the dissolution coincide with the Mn2+ depletion. Finally, the results allow defining new ways of treatment in reducing the energy requirements and the addition of reducing species. Figure 1

Hydrogen inhibition in wet dust removal systems by using calcium lignosulfonate (CLS)

A tribochemical silica-coating (TSC) method has been developed to improve the adhesion of dental resin composites to various substrates. The method utilizes airborne-particle abrasion using particles having a silica surface and an alumina core. The impact of the TSC method has been extensively studied but less attention has been paid to the characterization of the silica-modified alumina particles. Due to the role of silicate ions in cell biology, e.g. osteoblast function and bone mineralization, silica-modified alumina particles could also be potentially used as a biomaterial in scaffolds of tissue regeneration. Thus, we carried out detailed physicochemical characterization of the silica-modified alumina particles. Silica-modified alumina particles (Rocatec, 3M-ESPE) of an average particle size of 30µm were studied for the phase composition, spectroscopic properties, surface morphology, dissolution, and the capability to modify the pH of an immersion solution. The control material was alumina without silica modification. Pre-osteoblastic MC3T3-E1 cells were used to assess cell viability in the presence of the particles. Cell viability was tested at 1, 3, 7 and 10 days of culture with various particle quantities. Multivariate ANOVA was used for statistical analyses. Minor quantities of silica enrichment was verified on the surface of alumina particles and the silica did not evenly cover the alumina surface. In the dissolution test, no change in the pH of the immersion solution was observed in the presence of the particles. Minor quantities of silicate ions were dissolved from the particles to the cell culture medium but no major differences were observed in the viability of pre-osteoblastic cells, whether the cells were cultured with silica-modified or plain alumina particles. Characterization of silica-modified alumina particles demonstrated differences in the particle surface structure compared to control alumina. Dissolution of silica layer in Tris buffer or SBF solution varied from that of cell culture medium: minor quantities of dissolved Si were observed in cell culture test medium. The cell viability test did not shown significant differences between control alumina and its silica-modified counterpart.

Passive oxide layer on the surface of aluminum particles could impede combustion efficiency and burning rate. Passive aluminum (P-Al) and active aluminum without passive oxide layer (A-Al) of 5 µm were adopted for this study. Whereas P-Al demonstrated surface oxygen content of 7.23 mass%, A-Al demonstrated surface oxygen content of 0.23 mass%. Aluminum particles were integrated into ammonium perchlorate (AP) matrix. Whereas P-Al demonstrated an increase in AP decomposition enthalpy by 60%, A-Al boosted AP decomposition enthalpy by 123%. The surface passive oxide layer could render full exploitation of aluminum energy content. A-Al particles demonstrated decrease in AP activation energy by 43% using Kissinger's model. Solid propellant formulations based on 16 mass% aluminum particles were developed by mechanical mixing and vacuum casting; ballistic performance was evaluated using small-scale ballistic evaluation rocket motor. A-Al particles offered an increase in burning rate, specific impulse, and total thrust impulse by 80%, 5%, and 6.7%, respectively. These outcomes mean enhanced performance with extended range. Burning rate–pressure relation was determined using photo-acoustic wave. A-Al particles demonstrated pressure exponent of 0.28 compared with 0.19 for P-Al particles. It can be concluded that A-Al particles secured enhanced performance, with stable combustion process.

Hydrogen inhibition by using Cr(NO3)3·9H2O in the wet dust removal system for the treatment of aluminum dust

When a DLC film is prepared on the surface of micron-sized alumina particles by the PCVD method, a complex plasma is formed due to the interaction between the plasma and the particles, which has a serious impact on the deposition process. The particle simulation model based on the PIC-MCC method is established in a 2D cylindrical system. The evolution of charge accumulation and current on the surface of the particle with time are solved and Poisson equations are established to solve the space potential. Finally the particle charge and current are obtained with the particle radius and the law of spacing change. The results show that: with the increase of particle radius, the steady charge of the particles increases linearly and the charging current increases fast, while the charging relaxation time and steady surface current are almost unchanged, which indicates that the charge of spherical particles is proportional to the diameter, and the deposition rate is proportional to the surface area. The particle size has no effect on the deposition efficiency. In addition, the decrease in the law of different particles increases the effect of electric field between the particles. As a result, the steady charge of the particles increases, while the steady current decreases, which indicates that excessive particle density may make deposition efficiency. Lower, and the particle deposition efficiency can be improved by changing the plasma parameters to reduce the thickness of the particles’ positive ion sheath.

Modification of alumina and carbon particles using silane and methane was carried out in a D.C. plasma‐jet fluidized bed reactor at atmospheric pressure. XRD, SEM and EPMA results showed that b‐SiC was formed inside and on the surface of the carbon particles. For the alumina particles, metallic Si was deposited inside and on the surface of the particles, but unfortunately the X‐ray reflection peak of b‐SiC was difficult to observe due to interference by the alumina peak. Speculations are offered concerning the mechanism of the deposition inside and on the surface of the particles.

To improve the mechanical properties of alumina particulates reinforced steel matrix composite, Ti powder was added into the alumina preform, a 5140 steel matrix composite was fabricated by squeeze casting, and the influences of Ti powder on the microstructure, hardness and bending strength of the composite were investigated, compared with the composite without adding Ti powder. Applied Ti powder and alumina particulates were 10-25 μm and 100-180 μm in size, respectively. Both composites were successfully fabricated, however Ti powder addition increased the infiltration thickness of the composite. In the Ti contained composite, a TiC film in micron scale is formed on the surface of alumina particles, many TiC aggregates are dispersed in the steel matrix without obvious remaining Ti powder. The hardness and the three-point bending strength of the composite reach 49.5 HRC and 1 018 MPa, respectively, which are 17.9% and 52.4% higher than those of the composite in the absence of Ti addition. Fracture morphology shows that the debonding of alumina particulates is eliminated for the composite in the presence of Ti addition. Sessile drop test shows the average wetting angle between 5140 steel and that of Ti coated Al2O3 is about 82.15°, much lower than the wetting angle 150° between steel and pure Al2O3. Therefore, the increase in the mechanical properties of the composite is attributed to the improvement of Al2O3p/steel interface wetting and bonding by adding Ti powder in the preform.