He is currently focusing on the development of high temperature lubricants from 'soft' ceramic nanoparticles such as layered metal oxides and organosilica networks.catalysis [26] and energy storage. [27] The most widely investigated classes of exfoliated oxide nanosheets are titanates, [28] niobates [29] and titanoniobates, but various other compositions are now also known, as described in more detail below. Table 1. State of the art metal oxide nanosheet compounds. Compound name Exfoliation method Energy application(s) Remarks Ti 0.87 O 2 0.52-Acid-base by TBAOH [19b,32d] Thin film supercapacitors, [49] batteries, [50] piezos, [51] photocatalysis [52] Lateral size up to 100 μm [32d] Fe 0.8 Ti 1.2 O 4 0.8-Acid-base by TBAOH [41d] Photocatalysis [53] Ni 0.4 Ti 1.6 O 4 0.8-Acid-base by TBAOH Photocatalysis [53] Ti 0.91 O 2 0.36−Acid-base by TBAOH [18,54] Photovoltaics, [55] batteries, [56] fuel cells, [57] acid catalysis, [58] photocatalysis [59] Ti 4 O 9 2-Acid-base by TBAOH [37] Batteries, [37,60] fuel cells, [61] photocatalysis [59a,62] MnO 2 0.4-Acid-base by TBAOH [35] Supercapacitors, [35,63] Photovoltaics, [64] batteries, [65] photocatalysis [59a] Mn 1-x Ru x O 2 (x = 0.05 and 0.1) Acid-base by TBAOH [42] Supercapacitors [42] RuO 2 0.2-Acid-base by TBAOH [66] Supercapacitors, [67] fuel cells [68] Ca 2 Nb 3 O 10 − Acid-base by TBAOH [69] Ca 2 Nb 3 O 10−x N y -Acid-base by TBAOH [74] Photocatalysis [74] Ca 2 Na n−3 Nb n O 3n+1 − (n = 4, 5, 6) Acid-base by TBAOH [71] Ca 2-x Sr x Nb 3 O 10 -(x = 0, 0.5, 1, 1.5, 2) Acid-base by TBAOH [75] Photocatalysis [75] Ca 2 Nb 3-x Ta x O 10 -(x = 0.3, 1, 1.5) Acid-base by TBAOH [75] Photocatalysis [75] Ca 2 Nb 3-x Rh x O 10−δ -Acid-base by TBAOH [76] Photocatalysis [76] SrNb 2 O 6 F − Acid-base by TBAOH [69] (Eu 0.56 Ta 2 O 7 ) 2-Acid-base by TBAOH [77] TaO 3 -Acid-base by TBAOH [38] Batteries, [56b] photocatalysis [78] Sr 1.5 Ta 3 O 10 2-Acid-base by TBAOH [79] CaNaTa 3 O 10 2-Acid-base by TBAOH [20] Ca 2 Ta 3 O 10-x N y -Acid-base by TBAOH [44] Photocatalysis [44] Sr 2−x Ba x Ta 3 O 10-y N z -(x = 0.0, 0.5, 1.0) Acid-base by TBAOH [80] Photocatalysis [80] SrLaTi 2 TaO 10 2-Acid-base by TBAOH [20] Ca 2 Ta 2 TiO 10 2-Acid-base by TBAOH [20] Ti (5.2-2x)/6 Mn x/2 O 2 (x = 0.1, 0.2, 0.3, 0.4) Acid-base by TBAOH [81] Ti 1−x−y Fe x Co y O 2 (0 ≤ x ≤ 0.4 and 0 ≤ y ≤ 0.2) Acid-base by TBAOH [82] Cs 4 W 11 O 36 2-Acid-base by TBAOH [83] (MWO 6 ) -(M = Nb, Ta) Acid-base by TBAOH [45] Acid catalysis, [84] photocatalysis [85] NbMoO 6 -Acid-base by TBAOH [86] Acid catalysis [86,87] W 2 O 7 2-Acid-base by TMAOH [45] Photocatalysis [88] (Ti 1.825-x Nb x O 4 ) 0.7-(x = 0-0.03) Acid-base by TBAOH [89] (Ti 1.65 Mg 0.35 O 4 ) 0.7-Acid-base by TBAOH [90] Attempt to make (Ti 1.65 Ni 0.35 O 4 ) 0.7failed [91]Nb 3 O 8 -Acid-base by TBAOH [92] Acid catalysis, [92] photocatalysis [36,93] Nb 6 O 17 4-Acid-base by TBAOH [94] and intercalation of n-propylamine [95] Photovoltaics, [96] photocatalysis [59a][73c,97] TiNbO 5 − Acid-base by TBAOH [71] Batteries, [71] photovoltaics, [71] b...

The preparation and properties of reduced graphene oxide (rGO) and graphene nanosheets (GNSs) reinforcement of aluminium matrix nanocomposites (AMCs) are reported. For the rGO-AMCs, commercial colloidal GO was coated onto aluminium powder particles and then reduced via thermal annealing. For the GNS-AMCs, graphene exfoliated from graphite through ultrasonication and centrifugation was coated onto aluminium particle surfaces via dispersion mixing, filtering and drying. Pure aluminium and aluminium composites with various reinforcement concentrations of rGO and GNS were cold compacted into disc-shaped specimens and sintered in inert atmosphere. The mechanical properties and microstructure were studied and characterised via Vickers hardness, X-ray diffraction, density measurement, and scanning electron microscopy. The reinforcements were uniformly distributed onto the aluminium particle surfaces before and after consolidation within the composites. The relevant factors for the powder metallurgy process (compaction pressure, density, and sintering conditions) were optimised. Increased levels of increased hardness were recorded, over baseline compacted and sintered pure aluminium samples, prepared under identical experimental conditions, of 32% and 43% respectively for the 0.3wt.% rGO-Al and 0.15wt.% GNSs-Al composites. The process developed and presented herein provides encouraging results for realising rGO-AMC and GNS-AMC nanocomposites via low cost cold powder compaction and sintering metallurgy techniques.

Porous magnesium-aluminium layered double hydroxides (LDH) were prepared through intercalation and decomposition of hydrogen peroxide (H2O2). This process generates oxygen gas nano-bubbles that pierce holes in the layered structure of the material by local pressure build-up. The decomposition of the peroxide can be triggered by microwave radiation or chemically by reaction with iodide (I−) ions. The carbonate LDH version [Mg0.80Al0.20(OH)2](CO3)0.1∙mH2O was synthesized by microwave-assisted urea coprecipitation and further modified by iodide or H2O2 intercalation. High resolution Scanning Electron Microscopy (HR-SEM) and Brunauer-Emmet-Teller (BET) analysis were used to assess the morphology and surface area of the new porous materials. The presence of H2O2 in the interlayer region and later decomposition triggered by microwave radiation generated more pores on the surface of the LDH platelets, increasing their specific surface area from initially 9 m2/g to a maximum of 67 m2/g. X-Ray Diffraction showed that the formation of the pores did not affect the remaining crystal structure, allowing possible further functionalization of the material.

The oxide nanosheet concentration at the liquid− air interface (LAI) is a key parameter in the formation of Langmuir−Blodgett (LB) deposited nanosheet films. Knowledge of the oxide nanosheet concentration at the LAI as a function of process conditions is needed to understand the relevant processes and achieve better control over the LB fabrication process. In this study, the concentration of Ti 0.87 O 2 δ− titanate nanosheets at the LAI was investigated by considering the trend in the lift-up point (LUP) in the surface pressure−surface area isotherm of an LB compression process as a function of time and exfoliation agent. The oxide nanosheet concentrations in the bulk solutions were studied using UV−vis spectroscopy. The results show that the restacking process in the bulk solution does not significantly retard the occurrence of nanosheets at the LAI. The nanosheet concentration changes in the bulk and at the LAI occur on different time scales. Short exfoliation times yield higher nanosheet concentrations at the LAI than longer exfoliation times, in contrast to the bulk where the nanosheet concentration increases in the course of time. We found the same behavior for other metal oxide nanosheet solutions, i.e., iron-doped titanate (Ti 0.6 Fe 0.4 O 2 0.4− ) and calcium niobate (Ca 2 Nb 3 O 10 − ) nanosheets. The reason behind this phenomenon is likely related to the high degree of adsorption of surfactant molecules on the nanosheet surface after short exfoliation times.

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The intercalation of different primary n-alkylamines in the structure of a layered titanate of the lepidocrocite type (HTiO) for application in high-temperature solid lubrication is reported. The intercalation process of the amines was explored by means of in situ small-angle X-ray scattering (SAXS), with variations in alkyl chain length (3-12 carbon atoms) and the amine/titanate ratio. The intercalation process was found to be completed within 5 min after mixing of the precursors in water at 80 °C. The topotactic transformation of the layered titanate is driven by an acid-base reaction. The thermal degradation of the modified titanates was investigated by thermogravimetric analysis (TGA), and the chemical changes were investigated by temperature-dependent infrared spectroscopy (DRIFTS). The coefficient of friction of the lubricants was assessed by means of high-temperature pin-on-disc experiments up to 580 °C. The intercalation of amine rendered a deformable layered ceramic upon heating. It was found that the hydrocarbon chain length exerts an influence on the mechanical properties of the titanates, resulting in lower friction forces for lubricants with longer intercalated amine molecules. Films of solid lubricants with longer amine chain lengths showed coefficients of friction as low as 0.01, lower than that of the state-of-the-art material graphite.

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In view of their possible application as high temperature solid lubricants, the tribological and thermochemical properties of several organosilica networks were investigated over a range of temperatures between 25 and 580 °C. Organosilica networks, obtained from monomers with terminal and bridging organic groups, were synthesized by a sol-gel process. The influence of carbon content, crosslink density, rotational freedom of incorporated hydrocarbon groups, and network connectivity on the high temperature friction properties of the polymer was studied for condensed materials from silicon alkoxide precursors with terminating organic groups, i.e., methyltrimethoxysilane, propyltrimethoxysilane, diisopropyldimethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane and 4-biphenylyltriethoxysilane networks, as well as precursors with organic bridging groups between Si centers, i.e., 1,4-bis(triethoxysilyl)benzene and 4,4′-bis(triethoxysilyl)-1,1′-biphenyl. Pin-on-disc measurements were performed using all selected solid lubricants. It was found that materials obtained from phenyltrimethoxysilane and cyclohexyltrimethoxysilane precursors showed softening above 120 °C and performed best in terms of friction reduction, reaching friction coefficients as low as 0.01. This value is lower than that of graphite films (0.050 ± 0.005), a common bench mark for solid lubricants.