Ali Rinaldi

Dissolved Carbon Controls the Initial Stages of Nanocarbon Growth

Carbon is a versatile material that, depending on its hybrid-ization and assembly in one-, two-, or three-dimensionalnetworks, exhibits important electronic and chemical proper-ties with countless practical applications. For example, it isfound in printer inks, pencils, water purification systems,thermal isolation, and antistatic materials.

Oxidative Purification of Carbon Nanotubes and Its Impact on Catalytic Performance in Oxidative Dehydrogenation Reactions

Oxidative purification with mild diluted HNO3 followed by NaOH washing lowers the amount of amorphous carbon attached to multiwalled carbon nanotubes (CNTs). The graphitic structure improves remarkably by further annealing in argon at elevated temperatures, that is, 1173, 1573, and 1973 K. The influence of the purification treatment on the catalytic activity of the CNTs is investigated for the oxidative dehydrogenation (ODH) of ethylbenzene and propane as probe reactions. All samples tend to approach an appropriately ordered structure and Raman analysis of the used samples displays a D/G band ratio of 0.95-1.42. Oxygen functionalities are partly removed by the annealing treatment and can be rebuilt to some extent by oxygen molecules in the ODH reactant flow. The presence of amorphous carbon is detrimental to the catalytic performance as it allows for unwanted functional groups occurring in parallel with the formation of the selective (di)ketonic active sites.

A gamma fluorinated ether as an additive for enhanced oxygen activity in Li–O2 batteries

Perfluorocarbons (PFCs) are known for their high O2 solubility and have been investigated as additives in Li–O2 cells to enhance the cathode performance. However, the immiscibility of PFCs with organic solvents remains the main issue to be addressed as it hinders PFC practical application in Li–O2 cells. Furthermore, the effect of PFC additives on the O2 mass transport properties in the catholyte and their stability has not been thoroughly investigated. In this study, we investigated the properties of 1,1,1,2,2,3,3,4,4-nonafluoro-6-propoxyhexane (TE4), a gamma fluorinated ether, and found it to be miscible with tetraglyme (TEGDME), a solvent commonly used in Li–O2 cells. The results show that with the TE4 additive up to 4 times higher O2 solubility and up to 2 times higher O2 diffusibility can be achieved. With 20 vol% TE4 addition, the discharge capacity increased about 10 times at a high discharge rate of 400 mA gC−1, corresponding to about 0.4 mA cm−2. The chemical stability of TE4 after Li–O2 cell discharge is investigated using 1H and 19F NMR, and the TE4 signal is retained after discharge. FTIR and XPS measurements indicate the presence of Li2O2 as a discharged product, together with side products from the parasitic reactions of LiTFSI salt and TEGDME.

Monitoring the Dynamics of Heterogeneous Catalysts by Electron Microscopy

It is known that the shape of metal catalysts adapts to the chemical potential of the surrounding atmosphere and that the active surface evolves dynamically under reaction conditions [1-3]. Different photon-based characterization techniques were improved and implemented to probe the active state of catalysts in situ. However, such techniques lack the spatial resolution as they provide information averaged over a macroscopic scale, which is much larger than the catalytic active nanostructures.

The Dynamics of Active Metal Catalysts Revealed by In-Situ Electron Microscopy

Conventional high-resolution imaging by electron microscopy plays an important role in the structural and compositional analysis of catalysts. However, since the observations are generally performed under vacuum and close to room temperature, the obtained atomistic details concern an equilibrium state that is of limited value when the active state of a catalyst is in the focus of the investigation. Since the early attempts of Ruska in 1942 [1], in situ microscopy has demonstrated its potential and, with the recent availability of commercial tools and instruments, led to a shift of the focus from ultimate spatial resolution towards observation of relevant dynamics. [2]

Initiation of Carbon Nanofiber Growth on Polycrystalline Nickel Foam under Low Ethylene Pressure

The initiation of carbon nanofiber (CNF) growth on polycrystalline Ni foam was investigated by using a combination of ex situ and in situ methods, which include SEM, XRD, and Raman spectroscopy. Experiments were performed at a low hydrocarbon partial pressure to slow down the initiation process. Very little to no CNFs were observed on reduced samples, which is caused by diffusion of C to the bulk of the Ni foam. This prevents the formation of Ni3C as a precursor of Ni nanoparticles at a low hydrocarbon partial pressure from acting as active particles for CNF formation. CNF growth was significant on oxidized samples and the initiation was slowed down by using an extremely low ethylene pressure. Ni nanoparticles are able to catalyze CNF growth, provided these are isolated from the Ni bulk by unreduced NiO, which results from the incomplete reduction of the NiO layer.

Development of HVOF Coating of Hydroxy Apatite on Titanium Alloy with Carbon Nano Tube Intermediate Layer

Hydroxyapatite (HA) is considered as convenient material for the coating of titanium alloy in implant aplication. With the purpose to improve the morphology structure of HAP coating, the present research concerns in studying the effect of carbon nanotube (CNT) intermediate layer on HAP coated of titanium alloy. From SEM characterization, it can be observed that both of HAP coated sample, with and without CNT intermediate layer have porous nodular structure a characteristic of thermal spray coating without any micro-crack. However finer and more irregular structure observed on the sample with CNT intermediate layer, which is confirmed from XRD characterization, that lower degree of crystallinity occur on sample with CNT intermediate layer. After the coating, both of the samples were post annealed at 600 and 700°C for one hour. It was observed that micro-crack observed on the sample without CNT intermediate layer after post annealed at 700°C, while the rest of both samples observed without micro-crack.

Synthesis and Adsorption Performance of Carbon Materials for the Removal of Iron (III) from Aqueous Solution.

Carbon nanofibers prepared from Ni catalyst supported on activated carbon and pre-treated activated carbons show the potential in removing borderline and soft metal Fe (III) ions in single solutions over a wide range of concentrations. The morphological and textural properties of the carbon material were studied using the Scanning Electron Microscope (SEM) and Nitrogen adsorption isotherm method. Continuous column adsorptions were conducted to study the adsorption performance. The results showed that the percentage of Fe (III) removal starts to increase at the initial concentration of 10 mg/L. The percentage of Fe (III) removal continues to increase until it reaches the maximum removal at 60 mg/L. The value of correlation (R2) indicates that the data on carbon-based adsorption of Fe (III) may be concluded to perfectly fit the Langmuir isotherm model confirms the monolayer adsorption. Thus, this study is relatively useful in considering an appropriate technology for designing a suitable wastewater treatment plant.