Commercial Precursors Research Articles

Nanostructural Characters of β-SiC Nanoparticles Prepared from Indonesian Natural Resource using Sonochemical Method

Silicon carbide (SiC) nanoparticles become one of the interesting non-oxide ceramics due to their physical and chemical properties. For an extended period, SiC nanoparticles have been prepared by several methods that usually performed at high temperatures ranging from 1200 - 2000 °C from inexpensive commercial precursors. In this work, we prepared SiC nanoparticles from the low priced precursor of Indonesia natural resource using the sonochemical method at a temperature that is lower than 1000 °C. To produce samples with particular characters, we varied the sintering holding time (1, 10, and 20 hours) and the sintering temperatures (850, 950, and 1050 °C) during the synthesis. The samples were then characterized using XRD, SEM-EDX, TEM, and FTIR. The XRD data analysis showed that the samples have a dominant phase of SiC in the form of β-SiC with a 3C-SiC structure and SiO2 phase in a low composition within a good agreement with the EDX characterization. Interestingly, the sample prepared at the sintering temperature of 850 °C for 1 hour showed a non-crystallite phase. Using a Scherer’s equation, the particles of the samples sized from 13 to 18 nm, which were validated by SEM and TEM images. Furthermore, the FT-IR spectra presented several peaks, i.e., at wavenumbers of 482.2 and 1150 cm-1 representing Si-O-Si bonding and also at 798.5 cm-1 regarding with Si-C bonding.

The effect of Ge precursor on the heteroepitaxy of Ge1−xSnx epilayers on a Si (001) substrate

The heteroepitaxial growth of Ge1−xSnx on a Si (001) substrate, via a relaxed Ge buffer, has been studied using two commonly available commercial Ge precursors, Germane (GeH4) and Digermane (Ge2H6), by means of chemical vapour deposition at reduced pressures (RP-CVD). Both precursors demonstrate growth of strained and relaxed Ge1−xSnx epilayers, however Sn incorporation is significantly higher when using the more reactive Ge2H6 precursor. As Ge2H6 is significantly more expensive, difficult to handle or store than GeH4, developing high Sn content epilayers using the latter precursor is of great interest. This study demonstrates the key differences between the two precursors and offers routes to process optimisation which will enable high Sn content alloys at relatively low cost.

Screening of Different Encapsulated Polymer-Based Healing Agents for Chloride Exposed Self-Healing Concrete Using Chloride Migration Tests

The service life of steel reinforced concrete in aggressive marine environments could be increased substantially by embedding a self-healing mechanism that ensures autonomous healing of cracks upon their occurrence. Previous proof-of-concept experiments have shown that the incorporation of encapsulated polymer-based healing agents (HAs) counts as a very appropriate way to achieve this goal. Over the years, several polymer-precursor-capsule systems have been developed in that perspective at our laboratory. Cementitious materials containing either commercial or in-house developed encapsulated HAs have been subjected to preliminary feasibility tests (water absorption, permeability tests, etc.). However, these experiments did not yet allow for a fast and straightforward assessment of the self-healing efficiency (SHE) in relation to the expected durability and service life performance of the material. This approach would have many advantages when having to select the most suitable polymer-precursor-capsule system for a particular concrete application. In this paper, a modified chloride migration test based on the one prescribed in NT Build 492 has been proposed to support the development of self-healing concrete for marine environments. Four polymer-based HAs have been screened that way, i.e. an in-house developed high-viscosity polyurethane (PU) precursor, a commercial low-viscosity PU precursor, the same commercial PU precursor with addition of accelerator and benzoyl peroxide (BPO), and an in-house developed 2-component acrylate-endcapped precursor + cross-linker. For now, a highly repeatable SHE value of 100% could only be obtained for the second option.

A Scalable Strategy To Develop Advanced Anode for Sodium-Ion Batteries: Commercial Fe3O4-Derived Fe3O4@FeS with Superior Full-Cell Performance.

A novel core-shell Fe3O4@FeS composed of Fe3O4 core and FeS shell with the morphology of regular octahedra has been prepared via a facile and scalable strategy via employing commercial Fe3O4 as the precursor. When used as anode material for sodium-ion batteries (SIBs), the prepared Fe3O4@FeS combines the merits of FeS and Fe3O4 with high Na-storage capacity and superior cycling stability, respectively. The optimized Fe3O4@FeS electrode shows ultralong cycle life and outstanding rate capability. For instance, it remains a capacity retention of 90.8% with a reversible capacity of 169 mAh g-1 after 750 cycles at 0.2 A g-1 and 151 mAh g-1 at a high current density of 2 A g-1, which is about 7.5 times in comparison to the Na-storage capacity of commercial Fe3O4. More importantly, the prepared Fe3O4@FeS also exhibits excellent full-cell performance. The assembled Fe3O4@FeS//Na3V2(PO4)2O2F sodium-ion full battery gives a reversible capacity of 157 mAh g-1 after 50 cycles at 0.5 A g-1 with a capacity retention of 92.3% and the Coulombic efficiency of around 100%, demonstrating its applicability for sodium-ion full batteries as a promising anode. Furthermore, it is also disclosed that such superior electrochemical properties can be attributed to the pseudocapacitive behavior of FeS shell as demonstrated by the kinetics studies as well as the core-shell structure. In view of the large-scale availability of commercial precursor and ease of preparation, this study provide a scalable strategy to develop advanced anode materials for SIBs.

Characterization of Early Age Curing and Shrinkage of Metakaolin-Based Inorganic Binders with Different Rheological Behavior by Fiber Bragg Grating Sensors

This paper reports results related to early age temperature and shrinkage measurements by means fiber Bragg gratings (FBGs), which were embedded in geopolymer matrices. The sensors were properly packaged in order to discriminate between different shrinkage behavior and temperature development. Geopolymer systems based on metakaolin were investigated, which dealt with different commercial aluminosilicate precursors and siliceous filler contents. The proposed measuring system will allow us to control, in a very accurate way, the early age phases of the binding systems made by metakaolin geopolymer. A series of experiments were conducted on different compositions; moreover, rheological issues related to the proposed experimental method were also assessed.

The influence of additives in the stoichiometry of hybrid lead halide perovskites

We investigate the employment of carefully selected solvent additives in the processing of a commercial perovskite precursor ink and analyze their impact on the performance of organometal trihalide perovskite (CH3NH3PbI3−xClx) photovoltaic devices. We provide evidence that the use of benzaldehyde can be used as an effective method to preserve the stoichiometry of the perovskite precursors in solution. Benzaldehyde based additive engineering shows to improve perovskite solid state film morphology and device performance of CH3NH3PbI3−xClx based solar cells.

Interactions between mullite saggar refractories and Li-ion battery cathode materials during calcination

Used mullite-based saggars from a Li(NixCoyMnz)O2 (LNCM) materials-making plant were collected to characterize the degradation occurring during application. Based on the post-mortem analysis, laboratory scale experiments were designed using mixtures of mullite powders and commercial Li-ion battery cathode precursors. The mixtures were calcined at temperatures ranging from 800°C to 1100°C, and characterized with X-ray diffraction and scanning electron microscopy. The influence of temperature on the interactions between mullite and LNCM materials was determined. The combination of the post-mortem study and the laboratory scale tests allowed a more comprehensive understanding of the evolution of the saggar microstructure during degradation.

Influences of NH4F additive and calcination time on the morphological evolution of α-Al2O3 from a milled γ-Al2O3 precursor

Abstract The influences of an NH4F additive content and calcination time on the morphological evolution of α-Al2O3 were investigated by using commercial γ-Al2O3 precursor as raw material. The results showed that the morphological evolution of α-Al2O3 was highly related to the addition of NH4F, the additive content, and the calcination time. Square-like α-Al2O3 powders with a primary crystal size of ~200 nm were formed from the milled γ-Al2O3 precursor with 1 wt.% NH4F at 1300°C for 2 h, whereas round cake-like, hexagonal platelets, slender-like, and other irregularly shaped α-Al2O3 pieces in the size range of 0.2–2 μm were synthesized from the milled γ-Al2O3 precursor with 20 wt.% NH4F addition under the same calcination. Both morphological regularity and particle size distribution of α-Al2O3 were greatly facilitated by increasing the calcination time from 2 to 5 h. The addition of NH4F may lead to an alteration of the α-Al2O3 growth process by a change in the scale of the developing microstructure.

Interaction between Polyaramidic Electrospun Nanofibers and Epoxy Resin for Composite Materials Reinforcement

Interaction between poly (m-phenylene isophtalamide) (PMIA) electrospun nanofibers and commercial epoxy resin precursor during the cross-linking process was investigated, in order to use such polyaramidic nanofibers for composite materials reinforcement. Hence nanofibrous PMIA mats were produced via electrospinning technique to be used for the functional modification of the epoxy matrix composite properties. When adding such fibers to an epoxy resin precursor, it was observed a strong influence on the kinetics of its curing process. The final results, however, demonstrates that boosting the reaction condition (raising the temperature and the reaction time) the curing is pushed to completion, indicating that the cross-linking process of the resin is just delayed and not completely hampered. It will be therefore necessary to rethink the composite cure cycle when PMIA nanofibers are added to the composite material, in order to attain significant improvement of the final composite performance.

A novel pre-sintering technique for the growth of Y–Ba–Cu–O superconducting single grains from raw metal oxides

Most established top seeded melt growth (TSMG) processes of bulk, single grain Y–Ba–Cu–O (YBCO) superconductors are performed using a mixture of pre-reacted precursor powders. Here we report the successful growth of large, single grain YBCO samples by TSMG with good superconducting properties from a simple precursor composition consisting of a sintered mixture of the raw oxides. The elimination of the requirement to synthesize precursor powders in a separate process prior to melt processing has the potential to reduce significantly the cost of bulk superconductors, which is essential for their commercial exploitation. The growth morphology, microstructure, trapped magnetic field and critical current density, Jc, at different positions within the sample and maximum levitation force of the YBCO single grains fabricated by this process are reported. Measurements of the superconducting properties show that the trapped filed can reach 0.45 T and that a zero field Jc of 2.5 × 104 A cm−2 can be achieved in these samples. These values are comparable to those observed in samples fabricated using pre-reacted, high purity commercial oxide precursor powders. The experimental results are discussed and the possibility of further improving the melt process using raw oxides is outlined.

Multiscale Morphology of Nanoporous Copper Made from Intermetallic Phases.

Many application-relevant properties of nanoporous metals critically depend on their multiscale architecture. For example, the intrinsically high step-edge density of curved surfaces at the nanoscale provides highly reactive sites for catalysis, whereas the macroscale pore and grain morphology determines the macroscopic properties, such as mass transport, electrical conductivity, or mechanical properties. In this work, we systematically study the effects of alloy composition and dealloying conditions on the multiscale morphology of nanoporous copper (np-Cu) made from various commercial Zn-Cu precursor alloys. Using a combination of X-ray diffraction, electron backscatter diffraction, and focused ion beam cross-sectional analysis, our results reveal that the macroscopic grain structure of the starting alloy surprisingly survives the dealloying process, despite a change in crystal structure from body-centered cubic (Zn-Cu starting alloy) to face-centered cubic (Cu). The nanoscale structure can be controlled by the acid used for dealloying with HCl leading to a larger and more faceted ligament morphology compared to that of H3PO4. Anhydrous ethanol dehydrogenation was used as a probe reaction to test the effect of the nanoscale ligament morphology on the apparent activation energy of the reaction.

A Facile Green Synthetic Route for the Preparation of Highly Active \u03b3-Al2O3 from Aluminum Foil Waste

A novel green preparation route to prepare nano-mesoporous γ-Al2O3 from AlCl3.6H2O derived from aluminum foil waste and designated as ACFL550 is demonstrated, which showed higher surface area, larger pore volume, stronger acidity and higher surface area compared to γ-Al2O3 that is produced from the commercial AlCl3 precursor, AC550. The produced crystalline AlCl3.6H2O and Al(NO3)3.9H2O in the first stage of the preparation method were characterized by single-crystal XRD, giving two crystal structures, a trigonal (R-3c) and monoclinic (P21/c) structure, respectively. EDX analysis showed that ACFL550 had half the chlorine content (Cl%) relative to AC550, which makes ACFL550 a promising catalyst in acid-catalysed reactions. Pure and modified ACFL550 and AC550 were applied in acid-catalysed reactions, the dehydration of methanol to dimethyl ether and the total methane oxidation reactions, respectively. It was found that ACFL550 showed higher catalytic activity than AC550. This work opens doors for the preparation of highly active and well-structured nano-mesoporous alumina catalysts/supports from aluminum foil waste and demonstrates its application in acid-catalysed reactions.

The effects of morphology and size on performances of Li2FeSiO4/C cathode materials

The morphology-controlled Li2FeSiO4/C cathode material is successfully synthesized by a sol-gel method, in which commercial, spherical and cubic Fe2O3 are respectively used as iron sources. By controlling the Fe2O3 precursors' morphologies, the morphology and grain size of the Li2FeSiO4/C materials can be purposefully controlled via morphology-inheritance strategy. The morphologies, sizes, elemental distributions and structures of the as-prepared Li2FeSiO4/C materials are confirmed by field emission scanning electron microscopy (FE-SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD). The results show that the as-synthesized Li2FeSiO4/C samples exhibit well-defined morphologies due to the homogeneous and well-crystallized Fe2O3 precursors. Comparing with Li2FeSiO4/C synthesized by commercial Fe2O3 precursor, the Li2FeSiO4/C materials prepared by spherical or cubic Fe2O3 precursors exhibit eminent electrochemical properties, e.g., high initial reversible capacities of 214.1 mAh g−1 for LFS/C-S and 206.5 mAh g−1 for LFS/C-C at 0.1 C and good cyclic stability (93.1% for LFS/C-S and 91.5% for LFS/C-C). In particular, the spherical LFS/C-S material with better fluidity and less agglomeration displays excellent rate capability of 105.4 mAh g−1 at 10 C. Therefore, the control of the morphology and size during preparation process of Li2FeSiO4/C cathode materials will open a new route for the development of high performances lithium-ion batteries.

Study of low-defect and strain-relaxed GeSn growth via reduced pressure CVD in H2 and N2 carrier gas

High quality, thick (up to 1.1μm), strain relaxed GeSn alloys were grown on Ge-buffered Si (100) in an ASM Epsilon® chemical vapor deposition system using SnCl4 and low-cost commercial GeH4 precursors. The significance of surface chemistry in regards to growth rate and Sn-incorporation is discussed by comparing growth kinetics data in H2 and N2 carrier gas. The role of carrier gas is also explored in the suppression of Sn surface segregation and evolution of layer composition and strain profiles via secondary ion mass spectrometry and X-ray diffraction. Transmission electron microscopy revealed the spontaneous compositional splitting and formation of a thin intermediate layer in which dislocations are pinned. This intermediate layer enables the growth of a thick, strain relaxed, and defect-free epitaxial layer on its top. Last, we present photoluminescence results which indicate that both N2 and H2 growth methods produce optoelectronic device quality material.

Controlled Synthesis of Lead-Free and Stable Perovskite Derivative Cs2SnI6 Nanocrystals via a Facile Hot-Injection Process

Colloidal nanocrystals of lead halide perovskites have recently received great attention due to their remarkable performance in optoelectronic applications (e.g., light-emitting devices, flexible electronics, and photodetectors). However, the use of lead remains of great concern due to its toxicity and bioaccumulation in the ecosystem; herein we report a strategy to address this issue by using tetravalent tin (Sn4+) instead of divalent lead (Pb2+) to synthesize stable Cs2SnI6 perovskite nanocrystals. The shapes of as-synthesized Cs2SnI6 nanocrystals are tuned from spherical quantum dots, nanorods, nanowires, and nanobelts to nanoplatelets via a facile hot-injection process using inexpensive and nontoxic commercial precursors. Spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM) and simulation studies revealed a well-defined face-centered-cubic (fcc) perovskite derivative structure of Cs2SnI6 nanocrystals. The solution-processed Cs2SnI6 nanocrystal-based field effect...

Microstructure and wear behavior of Fe-based amorphous HVOF coatings produced from commercial precursors

Abstract Wear resistant highly amorphous Fe 60 Cr 8 Nb 8 B 24 (at.%) coatings of about 280 μm thickness were prepared through high velocity oxygen fuel (HVOF) thermal spray process onto API 5L X80 steel substrate. Feedstock powders were produced by gas atomization with low purity precursors by modifying AISI 430 stainless steel with additions of niobium (Fe-Nb) and boron (Fe-B). It was found that the coatings were mostly amorphous with some embedded FeNbB and Fe 2 B borides. The formation of a large fraction of amorphous phase was attributed to the high cooling rates of molten droplets combined with a proper powder composition. The average Vickers hardness of the coating (HV 0.3 = 838 ± 23) was about four times higher than that of the API 5L X80 substrate (HV 0.3 = 222 ± 5). The excellent wear resistance of the amorphous coating in the pin-on-disc measurements was attributed to its large fraction of amorphous phase (~ 66%) with reinforcing hard Fe 2 B and FeNbB borides, high Vickers hardness, low oxygen content ( − 5 and 8.5 × 10 − 4 mm 3 ·N − 1 ·m − 1 , respectively). API 5L X80 steel exhibited dominant adhesive wear at low sliding speed and oxidative wear at high sliding speed. HVOF coatings presented oxidative wear regardless of the sliding speed.

Highly conductive and pure gold nanostructures grown by electron beam induced deposition.

This work introduces an additive direct-write nanofabrication technique for producing extremely conductive gold nanostructures from a commercial metalorganic precursor. Gold content of 91 atomic % (at. %) was achieved by using water as an oxidative enhancer during direct-write deposition. A model was developed based on the deposition rate and the chemical composition, and it explains the surface processes that lead to the increases in gold purity and deposition yield. Co-injection of an oxidative enhancer enabled Focused Electron Beam Induced Deposition (FEBID)—a maskless, resistless deposition method for three dimensional (3D) nanostructures—to directly yield pure gold in a single process step, without post-deposition purification. Gold nanowires displayed resistivity down to 8.8 μΩ cm. This is the highest conductivity achieved so far from FEBID and it opens the possibility of applications in nanoelectronics, such as direct-write contacts to nanomaterials. The increased gold deposition yield and the ultralow carbon level will facilitate future applications such as the fabrication of 3D nanostructures in nanoplasmonics and biomolecule immobilization.

Hydrogenation of ethylene carbonate catalyzed by lutidine-bridged N-heterocyclic carbene ligands and ruthenium precursors

A series of air and moisture-stable lutidine-bridged N-heterocyclic carbene (NHC) ligands and commercial Ru precursors were applied as catalysts for hydrogenation of ethylene carbonate to glycol and methanol. N-Butyl-substituted CNC-pincer ligand L1 and RuHCl(CO)(PPh3)3 catalytic system exhibited the highest catalytic activity with 99% conversion of ethylene carbonate, 92% glycol and 42% methanol yields. The high catalytic activity was attributed to the in-situ formation of Ru-NHC complexes in the presence of base. This facile, stable and efficient catalytic system provided a new method for the indirect conversion of CO2.

Selection and technological potential of Lactobacillus plantarum bacteria suitable for wine malolactic fermentation and grape aroma release

Lactobacillus plantarum strains have resistance mechanisms that enable them to survive and proliferate in wine, which makes them potential malolactic fermentation (MLF) starter cultures. This work focused on the technological characterization of 11 L. plantarum strains isolated from Southern Italian wines that undergo spontaneous MLF, and proposes a selection of new L. plantarum malolactic starters. These strains were characterized according to their oenological characteristics, their ability to produce biogenic amines and bacteriocins, their response to the presence of phenolic compounds, their enzymatic activities and their ability to produce wine odorant aglycones from odourless grape glycosidic aroma precursors. Finally, the malolactic activity of one selected strain was assessed in Cabernet Sauvignon wine, using two inoculation methods. L. plantarum strains tested were not producers of biogenic amines. In particular, the M10 strain showed a good resistance to high levels of ethanol and low pH, it has a good malolactic performance and β-glucosidase activity, this last one demonstrated both directly through the measurement of this enzymatic activity and indirectly by following the release of volatile aglycones from commercial and natural grape glycosidic odourless precursors. These results demonstrated the potential applicability of M10 as a new MLF starter culture, especially for high-ethanol wines.

Structure-reactivity relationships of novel monomeric photoinitiators

Abstract Two different groups of methacrylates containing Type I or Type II photoinitiating moieties were synthesized and evaluated for use in UV curing applications. The first, a novel group of monomeric photoinitiators (MPIs) were synthesized by reactions of tert -butyl α-bromomethacrylate (TBBr) with 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone (Irgacure 2959), 1-hydroxy-cyclohexyl-phenyl-ketone (Irgacure 184) and 4-hydroxyacetophenone to give monomers MPI 1 , MPI 3 and MPI 4 respectively; and conversion of MPI 1 to MPI 2 by cleavage of tert -butyl ester groups with trifluoroacetic acid. The second group of photoinitiators were synthesized by reaction of 2-isocyanatoethyl methacrylate (IEM) with Irgacure 2959 (MPI 5 ) and 4-hydroxybenzophenone (MPI 6 ). All these MPIs’ absorption range in the UV region was found to be similar to their nonmonomeric analogs. Their photoinitiating abilities in the polymerizations of hexane-1,6-diol diacrylate (HDDA), 2-hydroxyethyl methacrylate (HEMA) and trimethylolpropane triacrylate (TMPTA) were studied using photodifferential scanning calorimeter and the kinetic parameters were correlated with the structures of the photoinitiating systems. Photoinitiating activities of investigated Type I photoinitiators, including small molecule commercial analogs, during polymerizations of HDDA and TMPTA are very slightly influenced by MPIs structure. However, the MPI structure is found to be important for the curing of HEMA, and some of the synthesized MPIs have better efficiency than commercial ones tested. The MPIs based on Irgacure 2959, Irgacure 184 and benzophenone (BP), with similar or increased photoinitiating activity compared to their commercial precursors, appear to be promising photoinitiators. An extra advantage of MPIs is their incorporation into the final formulations, reducing undesired migration of small molecules.