Exploring user experience of digital pen and tablet technology for learning chemistry : applying an activity theory lens

Mobile learning technologies are spreading rapidly in educational institutions throughout the world. Although research findings concerning the efficacy of mobile technologies for improving student outcomes are generally promising, there are still significant gaps in the research literature, particularly data from direct observational studies. This empirical investigation focused on how students made use of tablet devices and digital pens for learning Chemistry in an undergraduate university course. Observational data in the form of videos and static images, as well as, interview responses, were the main sources of data collected for the study. Activity theory was employed as the guiding theoretical framework to analyse and interpret the data. Several themes emerged from the data analyses, including the affordances of digital pen technology for facilitating reflective thinking, flexibility, peer collaboration, emerging learning and focused learning. It was also found that the use of these mobile technologies was contextualized, dependent on individual differences, and had challenges, for example, there was limited synchronicity between the operational design of the mobile devices and natural human movement. One of the main implications of the research is that when higher education institutions consider the potential benefits and challenges associated with mobile technologies they should take account of the interactions that occur between components within a system including, students, technological devices, and emerging learning processes

Surfactant-mediated and morphology-controlled nanostructured LiFePO4/carbon composite as a promising cathode material for Li-ion batteries

The synthesis of morphology-controlled carbon-coated nanostructured LiFePO4 (LFP/Carbon) cathode materials by surfactant-assisted hydrothermal method using block copolymers is reported. The resulting nanocrystalline high surface area materials were coated with carbon and designated as LFP/C123 and LFP/C311. All the materials were systematically characterized by various analytical, spectroscopic and imaging techniques. The reverse structure of the surfactant Pluronic® 31R1 (PPO-PEO-PPO) in comparison to Pluronic® P123 (PEO-PPO-PEO) played a vital role in controlling the particle size and morphology which in turn ameliorate the electrochemical performance in terms of reversible specific capacity (163 mAhg 1 and 140 mAhg 1 at 0.1 C for LFP/C311 and LFP/ C123, respectively). In addition, LFP/C311 demonstrated excellent electrochemical performance including lower charge transfer resistance (146.3 Ω) and excellent cycling stability (95% capacity retention at 1 C after 100 cycles) and high rate capability (163.2 mAhg 1 at 0.1 C; 147.1 mAhg 1 at 1 C). The better performance of the former is attributed to LFP nanoparticles (< 50 nm) with a specific spindle-shaped morphology. Further, we have also evaluated the electrode performance with the use of both PVDF and CMC binders employed for the electrode fabrication

Conversion of glycerol to hydrogen rich gas

Presently there is a glut of glycerol as the by-product of biofuel production and it will grow as production increases. The conundrum is how we can consume this material and convert it into a more useful product. One potential route is to reform glycerol to hydrogen rich gas including synthesis gas (CO + H2) and hydrogen. However, there is recent literature on various reforming techniques which may have a bearing on the efficiency of such a process. Hence in this review reforming of glycerol at room temperature (normally photo-catalytic), catalysis at moderate and high temperature and a non-catalytic pyrolysis process are presented. The high temperature processes allow the generation of synthesis gas with the hydrogen to carbon monoxide ratios being suitable for synthesis of dimethyl ether, methanol and for the Fischer-Tropsch process using established catalysts. Efficient conversion of synthesis gas to hydrogen involves additional catalysts that assist the water gas shift reaction, or involves in situ capture of carbon dioxide and hydrogen. Reforming at reduced temperatures including photo-reforming offers the opportunity of producing synthesis gas or hydrogen using single catalysts. Together, these processes will assist in overcoming the worldwide glut of glycerol, increasing the competitiveness of the biofuel production and reducing our dependency on the fossil based, hydrogen rich gas

Defect induced electronic states and magnetism in ball-milled graphite

The electronic structure and magnetism of nanocrystalline graphite prepared by ball milling of graphite in an inert atmosphere have been investigated using valence band spectroscopy (VB), core level near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and magnetic measurements as a function of the milling time. The NEXAFS spectroscopy of graphite milled for 30 hours shows simultaneous evolution of new states at ∼284.0 eV and at ∼290.5 eV superimposed upon the characteristic transitions at 285.4 eV and 291.6 eV, respectively. The modulation of the density of states is explained by evolution of discontinuities within the sheets and along the fracture lines in the milled graphite. The magnetic measurements in the temperature interval 2-300-2 K at constant magnetic field strength show a correlation between magnetic properties and evolution of the new electronic states. With the reduction of the crystallite sizes of the graphite fragments, the milled material progressively changes its magnetic properties from diamagnetic to paramagnetic with contributions from both Pauli and Curie paramagnetism due to the evolution of new states at ∼284 and ∼290.5 eV, respectively. These results indicate that the magnetic behaviour of ball-milled graphite can be manipulated by changing the milling conditions

Effect of solvent and silicon substrate surface on the size of iron nanoparticles

The diameter of carbon nanotubes is strongly related the geometric sizes of the metal particles upon which they are nucleated. To improve the control over the nanoparticle sizes derived from iron acetate and deposited on Si substrates, two different approaches were employed; manipulation of the solvent chemistry and manipulation of the Si substrate surface. The iron acetate was dissolved separately in pure water and ethanol and in binary ethanol/water mixtures. Silicon substrates, with either smooth surface or nano-porous surface, were dip coated using these solutions. The dip-coated substrates were first thermally oxidised at 400 °C in air followed by reduction at 800 °C in an Ar/H2 gas mixture. As derived particles were measured by scanning electron microscopy, and the average size and size distribution were determined by statistical analysis. Electron microscopy and statistical analyses demonstrated that metal particles deposited onto the smooth Si wafer have sizes ranging from 18 to 160 nm based on the solvent used, where the pure solvents resulted in a narrower size distribution when compared to the water/ethanol mixtures. When nano-porous Si wafer is used as a substrate, the metal particle diameter distributions are reduced to a range from 11 to 17 nm contingent upon the solvent used. The role of the ethanol/water interactions investigated by vibrational (IR and Raman) and 1H nuclear magnetic resonance spectroscopy on nanoparticle sizes and size distributions is discussed

The importance of carbonisation atmosphere on char properties derived from poly(divinylbenzene)

Production of activated carbons are a growing industry, and understanding to the processes involved in their synthesis is key to developing a better product. Generally the first step in the synthesis of activated carbon is the carbonisation of a material. During carbonisation the material undergoes aromatisation, and heteroatoms are removed, resulting in a highly aromatic carbon material. The physical and chemical properties are dependent on the degree of carbonisation and elemental makeup, which may be determined by the carbonisation conditions. In this study, properties of carbon chars derived from poly(divinylbenzene) are examined. Carbonisation conditions including, temperature, hold time, and atmosphere are studied to determine how these influence the thermal stability, elemental composition, and surface area and pore volumes of the final material. Surface areas were dependent on reactor gas, for nitrogen the surface area decreased from 665 m2/g to <1 m2/g as did pore volumes from 0.553 cm3/g to <0.01 cm3/g at 500°C; however, when the char was produced under an argon atmosphere, surface area and pore volume increased to 119 m2/g and 0.179 cm3/g. It was hypothesised that the difference between chars were due to a reaction of the char with nitrogen, which hindered the development of pores. Nitrogen reaction products were detected via elemental analysis and gas chromatography-mass spectrometry. This study shows the importance of the atmosphere and other parameters on the chars derived from poly(divinylbenzene)

Li-ion kinetics in LiFePO4/carbon nanocomposite prepared by a two-step process : the role of phase composition

LiFePO4/Carbon nanocomposite was synthesised by two-step procedure ̶ hydrothermal synthesis in the presence of ascorbic acid followed by mixing of the product with citric acid and heating at 600 °C under a reducing atmosphere. During the first-step, slab or cuboid-shaped LiFePO4 particles were formed with sizes of ∼ 100–150 nm in width and ∼ 300–600 nm in length. The second-step produced deformed slab or cuboid-like LiFePO4/Carbon nanocomposite with shapes somewhat resembling that of the precursor. The electrochemical properties were examined by electrochemical impedance spectroscopy (EIS) and potentiostatic intermittent titration technique (PITT) at a series of equilibrium potentials within the voltage range 2.7–4.2 V. From the PITT measurements of cathodes with two thicknesses, the LiFePO4/Carbon nanocomposite exhibits a specific discharge capacity of 150.3 mAh/g and 164.3 mAh/g, for 9.4 μm and 6.9 μm thickness, respectively. The current relaxation measurements also showed that the kinetics of Li-ion transfer depends strongly on the phase composition; in the solid-solution regions the Li-ion kinetics is dominated by diffusion whereas in the two-phase region it is by phase transformation

X-ray diffraction line profile analysis of nanocrystalline graphite

The structure evolution to nanocrystalline graphite produced by ball milling in n-dodecane has been studied by Fourier analysis of broadened X-ray diffraction line profiles according to double-Voigt method. The Fourier analysis gave size and strain distributions of the coherently diffracting domains (X-ray crystallite size) and root-mean-square-strain (rmss) and their average values. The precursor graphite was defined by average crystal sizes of about hundreds of nanometers, measured along the in-plane and out-of-plane directions, and low rmss value of 0.38 × 10-3. During milling, the average crystallite sizes of graphite decreased to about 6 and 43 nm along the out-of-plane and in-plane directions, respectively. Correspondingly, the rmss of milled graphite increased to 6.54 × 10-3. Analysis of the out-of-plane to in-plane crystallite size ratios showed that the crystallites became progressively thinner and flatter. A linear relationship between rmss and reciprocal crystallite size along the stacking axis revealed that size of disordered boundary regions gradually increased at the expense of ordered crystalline regions. A model describing crystalline-nanocrystalline transformation of graphite along different crystallographic axis was formulated and used to discuss the experimental data. It was concluded that a distortion-controlled process is responsible for the crystalline-nanocrystalline transformation of graphite milled in n-dodecane

Unoccupied electronic structure of ball-milled graphite

Changes in electronic and vibrational structure of well characterised macrocrystalline graphite milled by a planetary ball-mill are investigated by Raman spectroscopy and Near Edge X-ray Absorption Fine structure (NEXAFS) measurements at the CK-edge. The electronic structure changes at the surface and in the sub-surface of the particles are examined by comparing two-different NEXAFS detection modes: total fluorescence yield (TFY) and partial electron yield (PEY) respectively. When the in-plane crystallite sizes of graphite are decreased to nanosized (from [similar]160 nm to [similar]9 nm), a new spectral structure appears in TFY at 284.1 eV which is not present in the macrocrystalline graphite. This feature is assigned to electronic states associated with zigzag edges. Further the TFY shows a shift of the main graphite π* band from 285.5 to 285.9 eV, attributed to breaking the conjugation and hence the electron localization effect during milling, The TFY spectra also show strong spectral features at 287.5 and 288.6 eV, which suggest that the local environment of carbon atoms changes from sp2 to more sp3 due to physical damage of the graphite sheets and formation of structures other than aromatic hexagons. Complementary Raman spectroscopic measurements demonstrate an up-shift of the graphite G band from 1575 to 1583 cm−1en route to nanosize. The changes in TFY NEXAFS and Raman spectra are attributed to modification of the sub-surface electronic structure due to the presence of defects in the graphite crystal produced during milling. The discovery of the strong spectral feature at 284.1 eV in nanographite and the 0.4 eV up-shift of the π* band may open up possibilities to influence the electronic transport properties of graphite by manipulation of defects during the preparation of the nanographite

Glycerol oxidation over nano-gold supported nano-graphite catalysts

Nano-gold particles behave completely different, and exhibit excellent catalytic activity towards various organic transformations. Thus, the nano-gold particles, which are catalytically more active, are of significant interest. Unlike many other noble metals, gold surface is not poisoned owing to its high ionization potential leading to enhanced activity. In this regard, well dispersed nano-gold on nano-graphite surface leads to exceptional catalytic activity. In particular, the supported material acts as mild oxidation catalyst and yield highly selective products in addition to higher active life. In this investigation, the catalytic activity of gold supported nano-graphite system is reported, especially for selective oxidation of glycerol into glyceric acid