Hollow Cylindrical Shape Research Articles

Geometrical analysis in material extrusion process with polylactic acid (PLA)+carbon fiber

PurposeThe purpose of this study is to cover the influence of selected printing parameters at a macro and micro-geometrical level, focusing on the dimensions, geometry and surface of printed parts with short carbon fibers reinforced PLA. For this case study, a hollow cylindrical shape is considered, aiming to cover the gap detected in previous works analyzed.Design/methodology/approachNowadays, additive manufacturing plays a very important role in the manufacturing industry, as can be seen through its numerous research and applications that can be found. Within the engineering industry, geometrical tolerances are essential for the functionality of the parts and their assembly, but the variability in three-dimensional (3D) printing makes dimensional control a difficult task. Constant development in 3D printing allows, more and more, printed parts with controlled and narrowed geometrical deviations and tolerances. So, it is essential to continue narrowing the studies to achieve the optimal printed parts, optimizing the manufacturing process as well.FindingsResults present the relation between the selected printing parameters and the resulting printed part, showing the main deviations and the eligible values to achieve a better tolerance control. Also, from these results obtained, we present a parametric model that relates the geometrical deviations considered in this study with the printing parameters. It can provide an overview of the piece before printing it and so, adjusting the printing parameters and reducing time and number of printings to achieve a good part.Originality/valueThe main contribution is the study of the geometry selected under a 3D printing process, which is important because it considers parts that are created to fit together and need to comply with the required tolerances. Also, we consider that the parametric model can be a suitable approach to selecting the optimal printing parameters before printing.

The improved bioactive n-HA/PA66 cage versus the PEEK cage in anterior cervical fusion: results from a 6-year follow-up and a case-matched study

BackgroundThe nanohydroxyapatite/polyamide 66 (n-HA/PA66) cage, a bioactive nonmetal cage, is fabricated in a hollow cylindrical shape and has been widely used for decades with good clinical outcomes for anterior cervical fusion. However, there remain some radiological complications, such as a slightly high subsidence rate. To improve the clinical outcomes, the improved n-HA/PA66 cage now has been developed into a trapezoidal and wedge shape, a better biomechanical shape matching the cervical spine that is similar to that of the PEEK cage. However, there have been no long-term comparisons of the improved n-HA/PA66 cage and PEEK cage in anterior cervical reconstruction.MethodsFifty-eight patients who underwent single-level anterior cervical decompression and fusion (ACDF) with the improved n-HA/PA66 cage (n-HA/PA66 group) were matched with patients with the PEEK cage (PEEK group) by clinical presentation, segment, age and sex. All patients underwent a minimum of 6 years of follow-up. The radiographic parameters (cage subsidence, fusion status, cervical lordosis, and segmental sagittal alignment) and clinical parameters (10-point visual analogue scale, Neck Disability Index and Japanese Orthopedic Association scores) from patients were evaluated before surgery, immediately after surgery, and at the latest follow-up.ResultsThe n-HA/PA66 and PEEK groups were well matched in terms of clinical presentation, segment, age, and sex at surgery. The n-HA/PA66 and PEEK cages had similar fusion rates at 6 months postoperatively (n-HA/PA66: 58.6% vs. PEEK: 51.7%, P = 0.455) and at the last follow-up (n-HA/PA66: 96.6% vs. PEEK: 93.1%, P = 0.402). The respective cage subsidence rates in the n-HA/PA66 and PEEK groups were 6.9 and 12.1% (P = 0.342). The correction of SA was similar between the groups at the final follow-up (n-HA/PA66: 4.29 ± 1.99 vs. PEEK: 3.99 ± 2.59 P = 0.464). There were no significant differences between the two groups in mean cervical lordosis, visual analogue scale scores of the neck and arm, NDI scores, JOA scores or patients’ overall satisfaction at the final follow-up.ConclusionAfter single-level ACDF, the improved n-HA/PA66 cage had similar excellent results in both radiological and clinical outcomes compared with the PEEK cage over 6 years of follow-up. According to these results, the improved n-HA/PA66 cage and the PEEK cage could be comparable for ACDF.

Research Thermal Fields in the Crystallization Process of Steel Cast Parts

In foundry production, the duration of metal crystallization of the cast part, as well as the distribution of the thermal field, are described by systems of analytical equations. There are a number of methods for modeling these processes, but their theoretical basis was formed at the end of the twentieth century, and it needs to be updated and clarified. Therefore, the aim of our work is to develop a new analytical method for researching the distribution of thermal fields in cast parts during crystallization. For the first time, on the basis of own analytical and thermophysical developments, it developed the analytical method for researching the thermal field of the casting during crystallization and cooling, which is based on establishing the kinetics of cooling of the casting surface in the foundry mold, the advancement of the crystallization front from the surface to the center of the casting, and the distribution of temperatures in the solid and liquid parts of the casting. The method is expressed in a number of analytical formulas, each of which describes the specific thermal process that occurs in the casting. The developed analytical method was used to research the crystallization of the casting in a one-time sand mold, using the example of researching the thermal field of the cast part made of carbon steel with 0.25% C, hollow cylindrical shape, with the wall thickness of 100 mm. The developed analytical method for researching the thermal fields of cast parts is the analytical basis for the refinement of applied computer programs for modeling crystallization and cooling processes in foundry production.

Scalable, large-size, and flexible transparent bamboo

Transparent wood (TW) has received extensive attention recently because of its excellent optical, mechanical, and thermal properties. However, the long growth cycle of timber and forbidden deforestation regulation limit the large-scale application. Bamboo has a much shorter growth cycle than wood, but its high density and lack of lateral cell tissues make it challenging to produce transparent products. Meanwhile, fabrication of large-size transparent bamboo (TB) remains a huge challenge because of the inherent features of irregular, hollow cylindrical shape with nodes, and big culm taper. In this work, the “alkali pretreatment-crosslinking-delignification” strategy was developed to fabricate the scalable, large-size, and flexible TB from the building block of sliced bamboo veneer (SBV). The optical transmittance and haze of the TB with a thickness of 1.0 mm were approximately 80 % and 72 %, respectively, and possessed the light modulation capability. The fabricated TB exhibited flexibility, and the tensile strength was 78.5 MPa, which was higher than all reported flexible TW. Besides, the TB exhibited a low thermal conductivity of 0.35 W m−1 k−1, which had an outstanding thermal insulation and indoor temperature regulation performance. More importantly, this study demonstrated the feasibility of successful preparation of large-size TB, which can promote its large-scale and industrial application. The TB with excellent overall performance holds great potential in engineering applications, especially for energy-efficient windows, light-tunable devices, flexible transparent materials, etc.

Development and characterization of a 3D printed functional chicken meat based snack: Optimization of process parameters and gelatin level

A chicken meat-based snack formulation enriched by bioactive compounds was developed by optimizing 3D printing parameters and hydrocolloid level (gelatin) by Response Surface Methodology (RSM). The effects of gelatin addition and baking process on the quality of the 3D printed products were also evaluated. The gelatin concentration was determined by RSM using hollow cylindrical shape samples with perpendicular diameters of 30 mm and a height of 10 mm where the other independent parameters were filament flow rate, feed rate, and nozzle height from printing surface. Results indicate that optimum conditions to attain the best matched 3D printed cylindrical shaped product were 110% filament flow rate, 90% feed rate, 0.5 mm nozzle height, and 1.79% gelatin concentration. After optimization, product characteristics were evaluated in 3D printed products before and after baking. Adding 1.79% gelatin increased storage and loss moduli (G′ and G″ values), and complex viscosity, and decreased tan δ value (p < 0.05) resulting in more uniform and compact microstructure. All the analyzed sensory attributes of the gelatin added product received higher scores (p < 0.05) than control. The outcomes of this study provide insights how to tailor complex 3D printed functional muscle food formulations to meet manufacturing needs.

Analytical method of calculation of thermal fields of cast parts during crystallization

The aim of the work is to create a mathematical method that allows to calculate the distribution of thermal fields in cast parts during crystallization using a system of analytical formulas. During the calculations, a combination of known analytical formulas GF was used. Balandin, AY Weinik, S. Schwartz with their own original mathematical solutions created on the basis of the analysis of thermophysical processes in castings in the process of their crystallization. Computer simulation of thermal fields using the LVMFlow program was used to compare the results. According to the created mathematical method, examples of calculation of thermal fields for two castings made of steel 25L of hollow cylindrical shape, the wall thickness of which is 100 mm and 4 mm, respectively, are given. Calculations were performed for the conditions of crystallization of castings in a single sand form. The comparison of results of calculations by the developed method and with use of the existing software is presented. For the first time, based on our own mathematical and thermophysical developments, a comprehensive calculation method for determining the thermal field of the casting during crystallization and cooling was developed. casting. The technique is expressed in a number of analytical formulas, each of which describes a specific thermal process that occurs in the casting. This takes into account the features of the casting configuration. The created complex method of calculation of thermal fields of cast parts is a mathematical basis for determining the thermal fields of molds and rods, which allows to predict their properties and select the optimal molding materials. The created technique can also be offered as a mathematical basis for refining applied computer programs for foundry production. CASTING, TEMPERATURE, THERMAL FIELD, COOLING DYNAMICS, COOLING DURATION, MATHEMATICAL LAW, COLORING FRONT, CALCULATION

Fabrication of High Burn Rate Fuse Strip for Thermal Battery

Thermal batteries are widely used in various military applications such as missiles and torpedoes due to high power output, long shelf-life, and reliability. In order to react quickly to an enemy, quick activation time of the thermal battery is required. In the process of activation, fuse strip transfers heat energy to the heat source of each layer. Therefore, to achieve short activation time, fuse strip with high burn rate is highly needed. However, although there are lots of variables affecting burning rate of fuse strips, such as a combination of fuel and oxidizers, additives and particle size, it's not well-studied yet.In this study, we fabricated high burn rate fuse strips by applying additives and new oxidizer. Usually, to fabricate fuse strip, Zr and BaCrO4 slurry is deposited onto supporting ceramic paper and then dried. In order to improve burn rate, we additionally applied HDC-M10, NH4HCO3 and PbO into the Zr/BaCrO4 slurry. The retention agent HDC-M10 makes the dispersion solution stable, making the structure of fuse strip uniform. And the blowing agent NH4HCO3 controls the distance between the particle that makes optimal heat transfer path between the Zr and BaCrO4 particles. Also, PbO was chose as the best additional oxidizer among other several oxidizers which has appropriate reactivity, burn rate and heat calories. The mixed slurry was placed on a sheet former and then made into hollow cylindrical shape. The burning rate was then measured by self-made burning rate measurement equipment. As a result, we observed 10 times improved burn rate than previous studies. In addition, the fuse strip was applied to the thermal battery and its test result is also presented in this study.

Experimental Investigation on the Performance of Radial Flow Desiccant Bed Using Activated Alumina (Dept.M)

In the present work, an experimental investigation on the performance of radial flow desiccant bed using activated alumina has been carried out. A weight of 39.860 kg of spherical particles of the activated alumina with an average diameter of 4mm is used to form a hollow cylindrical shape bed with length of 90 cm and outer and inner diameters of 27.8 and 10.8 cm, respectively, to obtain radial flow of the air through the bed. In the present study, the weight of the bed is measured instantaneously using an accurate load cell to determine the adsorbed and desorbed water during the adsorption and desorption p rocesses, respectively. The experimental tests are carried out at different inlet air and initial bed conditions. Values of temperature and humidity of the air at inlet and exit of the bed are measured. Air inlet, and exit conditions are plotted on the psychrometric chart to demonstrate the transient variation of air conditions and the bed performance. In this study, effect of bed pre-cooling on the system performance is highlighted. The obtained results show that air with inlet humidity ranging from 18.7 to 12.5 g/kg could be dehumidified, using activated alumina, to a lower level of humidity (1.2 g/kg) when the temperature of the inlet air and bed temperature equal 32.5 °C.

A review on recent research studies on vibration analysis of fluid-conveying nanotubes

Nanotube (such as carbon and boron nitride nanotubes) is a key component of modern technology applications of nanostructures due to their unique mechanical, electrical, and physical characteristics such as high elasticity modulus, suitable heat transfer, and electrical conductivity. Carbon and boron nitride nanotubes are among the promising choices in nano-fluidic, gas storage, and drug delivery systems due to their hollow cylindrical shape and appropriate chemical, mechanical, and physical properties. Thermal vibration assessment should be conducted on fluid-conveying carbon nanotubes since the effect of thermal fluctuations on the mechanical characteristics of nanostructure are significant. Previous studies have revealed that when thermal vibration is taken into account, quantum effects can become extremely important in nanoscale electronics and structures. Hence, the present review focuses mostly on previous work on fluid-conveying nanotubes and the dynamical characteristics of size-dependent vibration and non-local strain gradient theory of fluid-conveying nanotubes. Furthermore, a special effort is made to address recent and rare investigations on the vibration of fluid-conveying nanotubes in thermal environment, as well as thermal vibration concerns of carbon nanotubes.

Miniaturized Dual-Resonant Helix/Spiral Antenna System at MHz-Band for FSK Impulse Radio Intrabody Communications

In this article, a miniaturized dual-resonant antenna system at MHz-band operating at around 20 and 50 MHz is proposed for frequency-shift keying impulse radio (FSK-IR) intrabody communications. This antenna system comprises a swallowable helix-coil in-body antenna with a hollow cylindrical shape of 10 mm diameter and 30 mm length, and two single band on-body matched planar spiral-coil antennas with a compact size of 79 mm $\times\,\,72$ mm $\times\,\,2.8$ mm. For in-body antenna design, a nonuniform helical pitch structure is utilized to produce dual-resonant frequencies. The soft ferrite magnetic sheet with high relative permeability and low dissipation factor is used as a flexible conformal substrate to realize antenna miniaturization without lumped element loading. Simulation results for antenna performance, electromagnetic field distribution, and specific absorption rate are presented with different tissue-type phantoms, as well as an anatomical numerical human model. In addition, experimental verification of antenna performance and implant transmission characteristics is also conducted in a liquid phantom. At an implant depth of 50 mm, the measured maximum transmission coefficients are −33 and −45 dB at the dual-resonant frequency bands, respectively. Simulation and measurement results demonstrate that the proposed dual-resonant antenna is suitable for the FSK-IR system and can be expected to realize a data rate as high as 10 Mb/s for biomedical implant applications at MHz-band.

New Al2O3–Cu–Ni functionally graded composites manufactured using the centrifugal slip casting

AbstractThe aim of this paper was to establish the general suitability of the centrifugal slip casting technique for fabrication of graded material from the Al2O3–Cu–Ni system. The present investigation is a preliminary one and the obtained results may be regarded as a point for acquiring the new knowledge in the ternary ceramic metal system fabricated using centrifugal slip casting. The rheological study provided the evidence that the suspension used to fabricate composites is a non‐Newtonian slurry. Moreover, the results demonstrated that the prepared slurry is stable over time. The obtained composites has a hollow cylindrical shape with relative density of &gt; 95%. The XRD study results revealed three phases: Al2O3, Ni, and CuNi. The microscopic investigations revealed a nonhomogeneous distribution of the metallic phase in the composite. It has been shown that the content of the metallic phase decreased with the increased distance from the outside to the inner edge of the ceramic‐metal composite. The study results allow to conclude that the interface between the phases is more continuous when sintering was carried out in a solid phase. However, it was found that when sintering was carried out in a liquid phase separated metal particles with spherical phase are formed.

Fast transformation of 2D nanofiber membranes into pre-molded 3D scaffolds with biomimetic and oriented porous structure for biomedical applications.

The ability to transform two-dimensional (2D) structures into three-dimensional (3D) structures leads to a variety of applications in fields such as soft electronics, soft robotics, and other biomedical-related fields. Previous reports have focused on using electrospun nanofibers due to their ability to mimic the extracellular matrix. These studies often lead to poor results due to the dense structures and small poor sizes of 2D nanofiber membranes. Using a unique method of combining innovative gas-foaming and molding technologies, we report the rapid transformation of 2D nanofiber membranes into predesigned 3D scaffolds with biomimetic and oriented porous structure. By adding a surfactant (pluronic F-127) to poly(ε-caprolactone) (PCL) nanofibers, the rate of expansion is dramatically enhanced due to the increase in hydrophilicity and subsequent gas bubble stability. Using this novel method together with molding, 3D objects with cylindrical, hollow cylindrical, cuboid, spherical, and irregular shapes are created. Interestingly, these 3D shapes exhibit anisotropy and consistent pore sizes throughout entire object. Through further treatment with gelatin, the scaffolds become superelastic and shape-recoverable. Additionally, gelatin-coated, cube-shaped scaffolds were further functionalized with polypyrrole coatings and exhibited dynamic electrical conductivity during cyclic compression. Cuboid-shaped scaffolds have been demonstrated to be effective for compressible hemorrhage in a porcine liver injury model. In addition, human neural progenitor cells can be uniformly distributed and differentiated into neurons throughout the cylinder-shaped nanofiber scaffolds, forming ordered 3D neural tissue constructs. Taken together, the approach presented in this study is very promising in the production of pre-molded 3D nanofiber scaffolds for many biomedical applications.

Experimental investigations and optimization of process parameters of meshed-wick heat pipe

Heat pipes are used to transfer heat, which are hollow cylindrical shape device filled with small amount of working fluid, which can change its phase. The rate of heat transfer in heat pipes compared to normal heat exchanging devices is more. Depending on the applications of heat transfer various heat pipes are being designed. Methanol fluid is used with 50% fill ratio. It is made of copper with outer diameter of 15.88mm and inner diameter of 14.88mm. It consists of a screen mesh made of copper powder inside it with thickness of 0.5mm. Due to heat input methanol changes its phase from liquid to vapor. The vapor loses its heat and changes its phase back to liquid in the condenser. At the condenser section the vapour gives up it heat and changes its phase from vapour to liquid. The screen mesh assists the flow of condensed working fluid through capillary action. Optimized the results by “Taguchi method” using “Minitab software”. The Thermal analysis was done with the optimum conditions, which were obtained as a result from the optimization method by Ansys Fluent software. Then finally compared the thermal parameters obtained from experiments with the Thermal analysis result. It is found the maximum heat transfer rate is optimized using meshed wick heat pipe conditions.

Effect of reheating zones in additive manufacturing by means of electron beam metal wire deposition method

The influence of heat transfer on molten pool size and temperature during the additive metal wire deposition process is shown. A mathematical model based on an energy equation that considers latent heat during melting is proposed. The model also examines the temperature dependences of thermophysical properties and the results are presented graphically. The analysis of computer simulation results reveals a gradual increase in molten pool size during deposition of a hollow cylindrical shape due to the influence of reheating zones. The results of experimental studies (conducted on ELA-40I and AELTK-12 electron beam installations) that confirm the simulation results are presented. Both sets of results suggest the need for feedback in order to control the molten pool temperature. As such, the proposed model is used to conduct a study involving temperature feedback. The analysis of time dependences obtained via simulation shows the fundamental possibility of stabilizing the temperature at a desired point. Limitations and possible improvements to this method are explored.

Energy barriers for collapsing large-diameter carbon nanotubes

Single-wall carbon nanotubes (SWNTs) are best known in their hollow cylindrical shapes, but the ground state of large-diameter tubes actually corresponds to a collapsed dumbbell-like structure, where the opposite sides of the nanotube wall are brought in contact and stabilized by van der Waals attraction. For those tubes, the cylindrical shape is metastable and it is interesting to investigate the energy barrier for jumping from one configuration to another. We calculate the energy barrier for SWNT collapse by considering a transition pathway that consists of an initial local deformation that subsequently propagates itself along the SWNT axis. This leads to finite and physically meaningful energy barriers in the limit of infinite nanotubes. Yet, such barriers are surprisingly large (tens of eV) and therefore virtually unsurmountable, which essentially prevents the thermal collapse of a metastable cylindrical at any reasonable temperatures. Moreover, we show that collapse barriers increase counterintuitively with SWNT diameter. Finally, we demonstrate that, despite such huge barriers, SWNTs may collapse relatively easily under external radial forces and we shed light on recent experimental observations of collapsed and cylindrical SWNTs of various diameters.

High-pressure steam: A facile strategy for the scalable fabrication of flattened bamboo biomass

Bamboo features the fastest growing speed and abundant in the plant kingdom. However, it remains a huge challenge to prepare large flat surface boards by directly sawing or cutting due to the hollow cylindrical shape of bamboo culms. We herein have demonstrated the preparation of facile scalable fabrication of larger flattened bamboo board without cutting it into arcs bamboo strips by high-press steam softening approach. The results show that modulus of elasticity (MOE) of bamboo decreases with increasing softening temperature from 100 °C to 160 °C, and increases 8.3% from 160 °C to 180 °C, which is still less than bamboo softened at 140 °C. Bamboo can be flattened after softening above 140 °C. In addition, the main components of bamboo have no obvious changes when the softening temperature is below 140 °C. Moreover, the density and MOE are reduced after softening due to the decomposition of chemical components and increases after flattening due to increasing densification of bamboo which makes the flattened bamboo structure more uniform and stable. Hemicellulose starts to decompose from 160 °C and the equilibrium moisture content (EMC) of soften bamboo is similar with flattened bamboo. It is also found that the volumetric swelling of the flattened bamboo is higher than that of soften bamboo. This work offers a facile methodology for promoting the high value-add utilization of bamboo biomass, and obtaining larger flatten bamboo board with high performance at a treatment condition of 160 ℃ and 8 min.

Air-breathing bio-cathodes based on electro-active biochar from pyrolysis of Giant Cane stalks

An innovative low-tech solution to fabricate electro-active biochar (e-biochar) electrodes for bio-electrochemical systems (BES) is proposed. Ligno-cellulosic stalks of Giant Cane (Arundo Donax L.) were subjected to pyrolysis treatment at 900 °C for 1 h. The material kept its original hollow cylindrical shape, rigid morphology and porous texture, as confirmed by 3DX-ray micro-computed tomography. These characteristics are suitable for its use at the air-water interface in BES, as air-breathing bio-cathodes. BET (Brunauer-Emmett-Teller) specific surface area was equal to 114 ± 4 m2 g−1, with more than 95% of pores in the microporosity range (pore diameter < 1 nm). Surface electrocatalytic activity was sufficient to sustain oxygen reduction reaction at pH 7, in terms of both onset potential (−0.02 V vs Ag/AgCl) and reduction limiting current density (1 A m−2). Electrical resistivity measurements confirmed sufficient conductivity (8.9 × 10−3 ± 1 × 10−4 Ω m) of the material and Raman spectroscopy allowed to estimate a graphitization degree in relation to the ID/IG, equal to 2.26. In parallel, the e-biochar were tested as air-exposed bio-cathodes in BES, coupled to carbon cloth bio-anodes. After inoculation with wastewater from swine-farming, current densities were generated in the range of 100–150 mA m−2, along more than 2 months of operation, under sodium acetate feeding. Confocal laser scanning imaging revealed consistent biofilm formation on the water-side surface of the cathodes, while a nearly-complete absence of it at the air-side.These e-biochar electrodes might open innovative perspectives to scale-up BES for different applications. Here, consistent salts depositions on the material after 70 days of exposure to the wastewater, suggest that e-biochar biocathodes might serve to recycle nutrients to agricultural soils, through minerals-enriched biochar.

New experimental method for evaluating the water permeability of concrete by a lateral flow procedure on a hollow cylindrical test piece

The durability of concrete depends to a large extent on the difficulty of external aggressive agents in penetrating the porous network of concrete. The ability of this material to withstand the intrusion of these aggressive agents is mainly characterized by permeability. The latter is influenced by the interconnected capillary pores which depend on the water/cement ratio (W/C).The objective of this study is: first, to review and discuss the main existing methods used to measure the water permeability of cementitious materials. Secondly, to propose a new experimental method which provides an increase in the area of contact of the water with the sample. The hollow cylindrical shape of the sample thus permits a transverse flow of the liquid from the inside to the outside. This method provides a high volumetric flow of water and ensures a good seal between the sample and the cell of the apparatus. The accuracy is much higher and the measurements are more representative. In order to validate the proposed experimental procedure, the study comprises 12 types of concrete with variable W/C ratio. The latter constitutes a means for characterizing the porous structure and the transfer properties in concrete.The results obtained show that the proposed method treats the disadvantages commonly encountered in current permeability apparatus. These results are reliable and explain the considerable influence of the W/C ratio on the water permeability of concrete.

Development of a Method for Producing Heaters for High-Temperature Vacuum Treatment of Materials

This paper describes a method for manufacturing a high-temperature heating unit. We used graphite powder GSP-50 as a filler and sugar as a binder. The filler and binder were taken in the ratio 6 : 1. In manufacturing the heater, a paper shell is used to make a tubular preform. The paper mold is filled with a mixture of graphite and sugar and then compacted using a shaking table to density ρ = = 1.185 g/cm3. The unburned compacted preform is placed into a pyrolysis unit to be calcined at 900°C for 6 h. Subsequently, the carbonized preform is saturated in the pyrolysis chamber at 970°C for 48 h to density ρ = 1.175 g/cm3. The carbon–carbon heater unit produced in this way reduces the time for manufacturing the heater by one order of magnitude, decreases the consumption of electricity, natural gas, and carbon materials, and significantly increases the life of the heater. This method is suitable not only for the manufacture of heating units but also for other products having a hollow cylindrical shape for nuclear, aviation, and space industries.

Green magnetic wave absorber: The potential of paddy straw and recycled paper

Earlier, magnetic cellulose fibre was successfully produced by lumen loading and in situ coprecipitation methods. But never before had magnetic paper or magnetic sheets been produced from paddy straw and recycled paper as their substrates. The main properties needed to produce these green magnetic sheets are natural fibres possessing lumen, a hollow cylindrical shape along the fibres. Although magnetic particles can be introduced outside of this lumen, it interferes with inter-fibre bonding, leading to low-grade paper properties and making loading processes very crucial. This journal describes the properties of paddy straw and recycled paper in terms of lumen possession and the lumen's ability to be loaded with magnetic particles. The results obtained show that when using lumen, the loading technique is better than that using the in situ coprecipitation method, and paddy straw has better magnetic particle loading ability than recycled paper.