Study of the Impact of Graphite Orientation and Ion Transport on EDLC Performance

A model study of electric double layer capacitor (EDLC)-style capacitors in which the electrodes were composed of low surface area-oriented flakes of graphite that compressed to form a paper-like morphology has suggested that ion transport rates significantly impact EDLC energy and power density. Twelve capacitors were constructed, each using the same model electrode material and the same aqueous NaCl electrolyte, but differing in relative electrode orientation, degree of electrode compression, and presence/absence of an ionic transport salt bridge. All were tested with a galvanostat over a range of discharge currents. Significant differences in energy and power density and estimated series resistance were found as a function of all the factors listed, indicating that capacitor performance is not simply a function of the electrode surface area. This simple postulation was advanced and tested against data: net ion (Na+, Cl−) ‘velocity’ during both charge and discharge significantly impacts capacitive performance.

Investigation of Polyetherimide Melt-Extruded Fibers Modified by Carbon Nanoparticles

The fibers based on thermoplastic partially crystalline polyetherimide R-BAPB modified by vapor grown carbon nanofibers (VGCF) were prepared by melt extrusion, exposed to orientational drawing, and crystallized. All of the samples were examined by scanning electron microscopy, X-ray scattering, and differential scanning calorimetry to study how the carbon nanofiller influences on the internal structure and crystallization behavior of the obtained R-BAPB fibers. The mechanical properties of the composite R-BAPB fibers were also determined. It was found that VGCF nanoparticles introduced into R-BAPB polyimide can act as a nucleating agent that leads, in turn, to significant changes in the composite fibers morphology as well as thermal and mechanical characteristics. VGCF are able to improve an orientation degree of the R-BAPB macromolecules along the fiber direction, accelerate crystallization rate of the polymer, and enhance the fiber stability during crystallization process.

Regulating the Deformation Properties of Paper by Varying the Degree of Its Anisotropy

Mechanical properties are crucial in assessing the paper quality. Deformation and strength properties of paper are determined by the strength and stiffness of the interfiber and intermolecular hydrogen bonds. The contribution ratio of interfiber and intermolecular hydrogen bonds to the strength of paper can be changed by adjusting the degree of its anisotropy. The article presents the results on a study of the deformation properties of laboratory anisotropic paper samples from kraft bleached softwood pulp with a beating degree of 30 °SR. The samples had basic weight of 90 g/m2 and the degree of stiffness anisotropy TSIMD/CD of 1.75–4.08. They were made by using Techpap SAS automatic dynamic handsheet former (Grenoble, France), with varying forming parameters – diameter of the nozzle, motion speed of the forming wire, and injecting speed of pulp. Deformation properties were determined by tensile test and processing of the stress-strain dependence (σ−ε). The outcomes have shown that, an increase of the fiber orientation degree in paper structure by changing the forming parameters caused a change in the nature of the paper deformation under tension. Increasing the fiber orientation degree in the structure of paper made it possible to increase the strength by 55 %, tensile stiffness by 63 % in the machine direction, while reducing the extensibility by 10 %. In the cross direction, it was possible to decrease tensile stiffness by 33 %, strength by 55 %, and increase the extensibility by 5 %. Anisotropy of tensile strength was 1.73–6.00. The greatest effect was obtained for the elasticity modulus in the pre-failure zone E2 (2.8–38.6). It means that, fiber orientation had a key importance when large deformations in the samples took place. The established quantitative regularities allowed optimizing the values of the deformation and strength properties of paper, and their ratio in the machine direction and cross direction due to the variation of the forming parameters. For citation: Rech D., Potasheva A.N., Kazakov Ya.V. Regulating the Deformation Properties of Paper by Varying the Degree of Its Anisotropy. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 174–184. DOI: 10.37482/0536-1036-2021-5-174-184

Quantum-Efficiency Enhancement and Mechanical Responsiveness of Solid-State Photoluminescence Materials Based on Uniaxial Cellulose Nanocrystal Arrays in Flexible Polymer via Assembly-Induced Emission

Assembling cellulose nanocrystals (CNCs) can induce solid-state photoluminescence based on Stokes scattering. Such photoluminescence is free of photo-quenching and should have great potential in optical materials, whereas poor flexibility of assembled CNC arrays limits its applications. Here, a co-assembly of binary components including 1D nanoparticles and long-chain polymers had been explored to introduce the uniaxial CNC arrays into a transparent poly (vinyl alcohol) (PVA) membrane, which enhanced the mechanical properties, especially the stretchable property. Besides, the CNC assembly was controlled by adjusting the volume ratio between CNC and PVA. The result indicated that co-assembly with PVA could improve the uniaxial orientation of assembled CNC arrays, which played a crucial role in enhancing the emission quantum-efficiency (EQE) of CNC. Stretching the PVA/CNC membrane could furthermore induce an enhancement in EQE together with a gradual shift in emission wavelength. The mechanism study on that stimulation-response suggested that the enhancement and shift came from the change in the uniaxial orientation degree and periodicity of the CNC assembly, respectively. Since the stimulation-responsive enhancement in EQE (from ca. 40% to ca. 60%) can even be observed by naked eyes, we believe such cellulose-based materials can be widely used in optical sensors.

Effect of Polyacrylonitrile Precursor Orientation on the Structures and Properties of Thermally Stabilized Carbon Fiber

The thermal stabilization process of polyacrylonitrile (PAN) precursor fiber was the key step to prepare high-performance carbon fiber. During the thermal stabilization process, the aggregation structure and the reactivity of molecular chains have significant effects on the microstructures and mechanical properties of carbon fiber. In the present paper, the effects of the orientation structure of PAN precursor fiber on the thermal stabilization reaction and the mechanical properties of carbon fiber were experimentally studied. Using multi-dimensional structural and mechanical properties tests, such as XRD, DSC, 13C NMR and Instron machine testing, the crystalline and skeleton structure, exothermic behavior, and tensile properties of PAN precursor fiber with different orientations in the process of thermal stabilization were characterized to reveal the relationship between microstructure evolution and tensile properties. The results showed that the orientation structure of PAN precursor fiber had an obvious effect on the thermal stabilization process and the tensile stress–strain characteristic. When the heat treatment temperature was lower than 200 °C, the crystallinity and crystallite size of PAN fibers with higher orientation degrees increased significantly. After sufficient thermal stabilization, the original PAN precursor fiber with a higher orientation degree could form more aromatic lamellar structures and showed better regularity. Furthermore, the yield strength and initial modulus of the fibers with a higher orientation degree increased due to the formation of more aromatic rings. The maximum increase in the percentages of yield strength and tensile modulus of the PAN fibers were achieved when the heat-treated temperature was 200 °C, and the percentage values were 138.4% and 158.7% compared to the precursor without heat-treatment. In addition, the elongation at break of the fibers with a higher orientation degree was also relatively larger.

Preparation and Properties of Opaque Polyethylene Terephthalate/TiO2 Filaments

The opaque polyethylene terephthalate (PET) filaments with different mass fractions of TiO2 particles were prepared by low-speed melt spinning and drafting. Basic structures including surface morphology, linear density, orientation degree and crystallinity, and properties including tensile and optical property of the PET/TiO2 filaments were systematically analyzed, especially the visual shielding property. The results showed that TiO2 particles were well-distributed on the filament surface without obvious aggregation, except when the mass fraction of TiO2 exceeded 6%. The addition of TiO2 increased the linear density of the PET filaments. The orientation degree of the filaments was positively correlated with the drafting ratio but hardly influenced by the mass fraction of TiO2. The crystallinity achieved the maximum when the mass fraction of TiO2 was 3% and then decreased gradually. The tenacity of the filaments reduced and the elongation at break enhanced initially and then decreased with the increasing TiO2 content. The opaque effect of the PET filaments improved significantly when the mass fraction of TiO2 was less than 6%, whereas the improvement of the opaque effect slowed down as the mass fraction of TiO2 increased further.

Experimental Investigation on Organic Matter Orientation Characteristics of Terrestrial and Marine Shale in China

As an essential component in shale, OM (organic matter) grains and their arrangements may play essential roles in affecting the anisotropy of the reservoir. However, OM grains are commonly treated as an evenly distributed isotropic medium in current studies, and few works have been done to investigate their detailed arrangement characteristics. In this study, terrestrial and marine shale samples were collected from three different shale plays in China, and the arrangement characteristics of OM grains in each sample were investigated by SEM (scanning electron microscope) image analysis. The results indicate that OM grains in shale are not evenly distributed in isotropic medium, and their directional alignment is pervasive in both marine and terrestrial shale. OM grains in shale tend to subparallel to the bedding section, and their orientation degree and controlling factors differ among different shales. OM grains in samples from terrestrial C-7(Chang-7 Formation) exhibit the strongest directionality in their arrangement, and OM grains in samples from marine LMX (Longmaxi Formation) shale in the Fuling area also exhibit strong directional alignment. While in samples from marine LMX shale in the Baojing area, their directional alignment is much weaker. Shales with high clay content, high TOC (total organic carbon), low thermal maturity, and flat reservoir structure get more OM grains parallel to the bedding section. The biogenetic texture of graptolite in marine LMX shale is the dominating factor leading to the strong directional alignment of the OM grains. However, syncline structure may disorganize the preformed directional alignment and weaken the directionality of the OM grains, which results in the OM arrangement difference between LMX samples from Fuling and Baojing. While the compaction of the layered clay particles is the dominating mechanism leading to the strong directional alignment of the OM grains in terrestrial shale samples from C-7.

Pengaruh Variasi Waktu Sintering Terhadap Pertumbuhan Fase Bahan Superkonduktor BSCCO-2212 dengan Kadar Ca=1,10 Menggunakan Metode Pencampuran Basah

This research was conducted to determine the effect of sintering time on the formation of the superconducting phase BSCCO-2212 by calculating the level of purity of the phases formed and looking at the microstructure. The variation of sintering time was 10, 20, 30 and 40 hours using the wet mixing method. The sample was calcinated with 800 °C for 10 hours and sintered with 830 °C. The XRD’s characterization result shows a decrease in phase purity with increasing the sintering time. The relative high volume fraction of the BSCCO-2212/ts10 sample is 90,48% while, the lowest volume fraction of BSCCO-2212/tc40 is 50,74%. The relative high orientation degree of BSCCO-2212/ts20 is 18,47% and the lowest orientation degree of BSCCO-2212/ts10 is 8,4%. The SEM’s characterization result shows of all samples have been oriented and have relatively little space between slabs (voids).