Lower Mass Percentage Research Articles

Empirical way for finding new uranium-based heavy-fermion materials

The field of heavy-fermion physics emerged nearly four decades ago and has since remained one of the most prominent research directions in condensed-matter physics. Nonetheless, while significant progress has been made in unraveling heavy-fermion behavior and accompanying exotic phenomena, many questions remain. This issue can be advanced from two directions: comprehensive understanding of existing materials and discovery of novel systems. In this work, we propose a targeted method for discovery of uranium-based heavy-fermion materials by synthesis of complex intermetallic compounds with low mass percentage of uranium, high coordination number of uranium, and long overall shortest uranium bond length. We report the discovery and synthesis of the new complex uranium-based heavy-fermion material ${\mathrm{U}}_{23}{\mathrm{Hg}}_{88}$, which suggests this approach to be a reliable route for the targeted search of novel strongly correlated uranium-based materials. The Sommerfeld coefficient $\ensuremath{\gamma}=630\phantom{\rule{0.28em}{0ex}}\mathrm{mJ}\phantom{\rule{0.16em}{0ex}}{\mathrm{mol}}_{\text{U}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}2}$ indicates extremely strong electronic correlations and places ${\mathrm{U}}_{23}{\mathrm{Hg}}_{88}$ among the heaviest uranium-based compounds. ${\mathrm{U}}_{23}{\mathrm{Hg}}_{88}$ orders antiferromagnetically below ${T}_{\text{N}}=2.2\phantom{\rule{0.28em}{0ex}}\mathrm{K}$ and displays a dual nature of the $5f$ electrons. This work will pave a way for a comprehensive understanding of heavy-fermion phenomena in general and uranium-based systems in particular.

Facile and ultrafast solid-state microwave approach to MnO2-NW@Graphite nanocomposites for supercapacitors

MnO2 nanowires/graphite nanocomposites (MnO2-NW@Graphite) were successfully manufactured by an ultrafast, facile and cost-effective solid-state approach using microwave energy. Intensive research was conducted to investigate the effects of the material mass ratio, the microwave power and the microwave exposure time on the yield and morphology of the MnO2-NW@Graphite nanocomposites. The effect of the heating layer on the morphology was also studied. The morphology and structure of the nanocomposites were characterized using scanning electron microscope (SEM), X-ray power diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA). In addition, the electrochemical performances of the MnO2-NW@graphite nanocomposites were evaluated in basic media using 1M potassium hydroxide (KOH). The prepared nanocomposites exhibit a maximum specific capacity of 380.4F/g at a current density of 1A/g. The composites show high rate capabilities and good long-term stability with approximately 80% (303.57F/g) retention of capacitance after 2000 cycles. With the low mass percentage (12.9%) of MnO2 nanowires in MnO2-NW@Graphite, its outstanding electrochemical performance shows that it is a promising electrode material for supercapacitors. In addition, this microwave assisted approach towards the fabrication of MnO2 nanowires is expected to achieve mass production for inexpensive energy materials.

Fixed-bed column studies of total organic carbon removal from industrial wastewater by use of diatomite decorated with polyethylenimine-functionalized pyroxene nanoparticles

In this study, a fixed-bed column adsorption process was employed to remove organic pollutants from a real industrial wastewater effluent using polyethylenimine-functionalized pyroxene nanoparticles (PEI-PY) embedded into Diatomite at very low mass percentage. Various dynamic parameters (e.g., inlet concentration, inlet flow rate, bed height, and PEI-nanoparticle concentration in Diatomite, (%nps)) were investigated to determine the breakthrough behavior. The obtained breakthrough curves were fit with a convection-dispersion model to determine the characteristic parameters based on mass transfer phenomena. The axial dispersion coefficient (DL) and group of dimensionless numbers; including Renold number (Re), Schmidt number (Sc), and Sherwood number (Sh) were all determined and correlated by Wilson-Geankoplis correlation that was used to estimate the external film diffusion coefficients (Kc) at 0.0015 < Re<55.

The role of material composition, fiber properties and deformation mechanisms in the deep drawing of paperboard

The aim of this paper is to contribute to an improved understanding of deformation mechanisms of paperboard in the deep drawing process with immediate compression which reaches the highest degree of formability. Experiments with different fiber types and material structures were conducted on a laboratory and pilot scale to determine the major material-related influences on the formability of paperboard. The different fiber type combinations were studied together with different additives. The results show that increased pore volume and fiber-to-fiber mobility significantly increase initial wrinkle height which is significant for the quality of the drawn three dimensional (3D) structure. A material structure consisting of a mixture of cellulose fibers and a low percentage of stiff regenerated cellulose or synthetic staple fibers in combination with alkyl ketene dimer or cationic wax as an additive leads to a wrinkle-free wall until a forming ratio (forming height divided by base diameter) of at least 0.22 is reached. Accordingly, the process can be broken down into three phases. In the first phase, the cellulosic structures are deformed or broken, and the material density is reduced due to fiber-to-fiber movement. Refining and wet pressing decrease pore volume, increase the number of bonds in the material, thereby obstructing fiber-to-fiber movement. In the second phase, wrinkles occur. The introduced bending stiffness index together with the tensile index provides an indication of the material behavior in these two phases. The third phase is a restructuring of the material structure and a fixation of wrinkles by creating new bonds in the limited wrinkle areas. The experiments indicate that refined fibers make significantly higher wrinkle strength possible and thus better fixation of the final 3D structure shape. Additives with low melting temperatures can also contribute to improved wrinkle strength even in a low mass percentage of 0.5 %.

Synthesis and microwave absorption properties of carbon coil–carbon fiber hybrid materials

Uniform growth of carbon coils on the surface of carbon fibers was achieved by acetylene decomposition at 680°C with Ni nanoparticles as the catalyst. The homogeneous precipitation-reduction method was used to coat the carbon fibers with Ni nanoparticles. The scanning electron microscope images reveal that these carbon coils are mainly composed of spring-like microcoils, and include a few twist-shaped nanocoils. The carbon yield calculated from carbon yield=(mass of product/mass of Ni)×100% is about 34,000% in a run of 1h. By incorporating 10wt% of the carbon coil–carbon fiber hybrid in a paraffin matrix, a material with good microwave absorption is produced, despite the low mass percentage of filler.

Simultaneous synthesis of carbon nanobelts and carbon/Fe–Cu hybrids for microwave absorption

By acetylene decomposition at 450 °C over the Fe–Cu nanoparticles (Fe:Cu molar ratio = 29:1, 5:1) derived from a combined sol–gel/reduction method, carbon nanobelts (CNBs) and carbon/Fe–Cu hybrid nanoparticles (CNPs) were synthesized simultaneously with high yield. The two carbon species could be easily separated according to color and were collected at different locations of the ceramic plates where the catalysts were placed. Over Fe–Cu nanoparticles of high Cu content (Fe:Cu = 2:1), the product was carbon nanofibers. A series of comparison experiments was designed to study the optimal conditions for the formation of CNBs, and the results indicate that CNBs and CNPs can be selectively synthesized at 450 °C by adjusting the Cu content of the catalyst. Moreover, the complex permittivity and permeability of the mixture that contains CNPs or CNBs (30 wt.%) (paraffin wax as binder matrix) were measured in the 2–18 GHz frequency range. Despite the low mass percentage of CNBs, microwave absorption is good. Below −10 dB, there are two, three, and four distinct reflection loss peaks when the thicknesses of CNB composites are within the 5.5–7.5 mm, 9.5–11.5 mm, and 11.5–13.5 mm ranges, respectively.

Gelation characteristics and morphology of corn starch/soy protein concentrate composites during heating

The formation of corn starch (CS) and soy protein concentrate (SPC) composite during heating has been investigated using thermal and rheological analysis. SPC did not exhibit endothermic peak in differential scanning calorimetry (DSC) thermogram. Adding CS at low mass percentage (16.7%) to SPC resulted in a reduction of storage modulus ( G′) from 7.72 to 3.63 kPa at 50 °C. The DSC thermogram showed that the peak temperature was raised to 73.5 °C, compared with 70 °C for CS. The gelatinization of starch granules played an important role on the rheological properties of the composite during heating. Scanning electron microscopy and light microscopy with the aid of histological technique revealed the microstructure of CS/SPC composites. The observation illustrated that starch granules lost integrity and formed a gel with SPC at the temperature of maximum G ′ ( T G max ′ ) . The effect of starch mass percentage on the structural change of the composite was discussed.

Magnetically stabilised fluidised bed adsorption: practical benefit of uncoupling bed expansion from fluid velocities in the purification of a recombinant protein fromEscherichia coli

A composite magnetite–agarose adsorbent has been fabricated in a bead emulsification process and, following derivatisation with a peptide, exploited in the direct, one-step purification to near molecular homogenity of an anti-MUC1 diabody fragment (dbFv) expressed in the periplasm of recombinant Escherichia coli. Variation of performance with temperature and feedstock concentration was attributed respectively to conformational variation of the immobilised ligand and different kinetic driving forces at adsorption. The low particle density (1.12 g cm−3) resulting from the low mass percentage of introduced magnetite required that adsorption be operated in a magnetically stabilised fluidised bed (MSFB) contactor. The contactor achieved direct adsorption of product from EDTA-treated E coli whole broth while operating under conditions of bed expansion uncoupled from fluid velocity and viscosity. The generic applicability of such adsorbents and contactors to the direct biorecovery of proteins from complex feedstock is discussed. © 1999 Society of Chemical Industry