Properties of a new insulation material glass bubble in geopolymer concrete

This paper details analytical research results into a novel geopolymer concrete embedded with glass bubble as its thermal insulating material, fly ash as its precursor material, and a combination of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) as its alkaline activator to form a geopolymer system. The workability, density, compressive strength (per curing days), and water absorption of the sample loaded at 10% glass bubble (loading level determined to satisfy the minimum strength requirement of a load-bearing structure) were 70 mm, 2165 kg/m3, 52.58 MPa (28 days), 54.92 MPa (60 days), and 65.25 MPa (90 days), and 3.73 %, respectively. The thermal conductivity for geopolymer concrete decreased from 1.47 to 1.19 W/mK, while the thermal diffusivity decreased from 1.88 to 1.02 mm2/s due to increased specific heat from 0.96 to 1.73 MJ/m3K. The improved physicomechanical and thermal (insulating) properties resulting from embedding a glass bubble as an insulating material into geopolymer concrete resulted in a viable composite for use in the construction industry

Warpage optimisation on the moulded part with straight drilled and conformal cooling channels using Response Surface Methodology (RSM), Glowworm Swarm Optimisation (GSO) and Genetic Algorithm (GA) Optimisation Approaches

It is quite challenging to control both quality and productivity of products produced using injection molding process. Although many previous researchers have used different types of optimisation approaches to obtain the best configuration of parameters setting to control the quality of the molded part, optimisation approaches in maximising the performance of cooling channels to enhance the process productivity by decreasing the mould cycle time remain lacking. In this study, optimisation approaches namely Response Surface Methodology (RSM), Genetic Algorithm (GA) and Glowworm Swarm Optimisation (GSO) were employed on front panel housing moulded using Acrylonitrile Butadiene Styrene (ABS). Each optimisation method was analysed for both straight drilled and Milled Groove Square Shape (MGSS) conformal cooling channel moulds. Results from experimental works showed that, the performance of MGSS conformal cooling channels could be enhanced by employing the optimisation approach. Therefore, this research provides useful scientific knowledge and an alternative solution for the plastic injection moulding industry to improve the quality of moulded parts in terms of deformation using the proposed optimisation approaches in the used of conformal cooling channels mould

On Magnetization Reversal in Hard Magnetic Sm-Fe-N Permanent Magnets

The investigations were carried out on Sm-Fe-N permanent magnets produced by reactive diffusion method. The magnets consist of hard magnetic phases: Sm$\text{}_{2}$Fe$\text{}_{17}$N$\text{}_{0.86}$ and SmFe$\text{}_{5}$ and soft magneticα-Fe phase. From the comparison of experimentally determined angular dependence of coercive field with appropriate theoretical predictions and from the dependence of coercive field on the external magnetic field determined from the minor hysteresis loops, it was stated that magnetization reversal process in Sm-Fe-N magnets is controlled by the nucleation of reversed domains process

Structural and Magnetic Studies of the LaFe_{11.2}Co_{0.7-x}Mn_xSi_{1.1} (where x=0.1, 0.2) Alloys

The aim of present work was to study the influence of partial substitution of Co by Mn in the LaFe_{11.2}Co_{0.7}Si_{1.1} alloy on its structure and magnetic properties. The X-ray diffraction studies revealed coexistence of dominant pseudobinary fcc La(Fe,Si)_{13}-type phase with minor fraction of α-Fe. Moreover, the increase of Mn content causes decrease of the lattice parameter and the Curie temperature. The values of magnetic entropy change obtained for both investigated alloys are almost identical and close to 12 J/(kg K) under the change of external magnetic field ≈5 T. Investigations of magnetic phase transition confirmed its second order nature in the case of both specimens

Mechanism of Rotational Hysteresis Energy in Sm-Fe-N Permanent Magnets

Investigations were carried out on Sm-Fe-N permanent magnet produced by the reactive diffusion method with different grain sizes (from 8.6 to 0.97μm). The rotational hysteresis energy has been measured as a function of the applied field. The proposed model of rotational hysteresis energy is in good agreement with the experimental results. It is shown that the magnetization reversal process in Sm-Fe-N magnet is controlled by the nucleation of reversed domains

The Bulk Glass Forming Ability and Magnetic Properties of Pr9Fe50+xCo13Zr1Nb4B23−xPr_9Fe_{50 + x}Co_{13}Zr_1Nb_4B_{23 - x} (x = 0, 2, 5, 8) Alloys

In the present study the rapidly quenched $Pr_9Fe_{50 + x}Co_{13}Zr_1Nb_4B_{23 - x}$ (x = 0, 2, 5, 8) alloy samples produced in a form of 100 $mm^2$ plate of various thicknesses were investigated. The X-ray diffraction revealed changes in the phase constitution of as-cast samples depending on the alloy composition and plate thickness. The presence of hard magnetic $Pr_2(Fe,Co)_{14}B$ phase was observed in 0.5 mm thick plates of the x = 8 alloy, while fully glassy structure was shown in 0.5 mm thick plates of the x = 0 alloy. It was shown in the present paper that magnetic properties of annealed samples originated from different microstructure of as-cast samples

Phase structure of the nanocrystalline Nd2Fe14B/alfa-Fe magnets with different grain

The effect of the contents of the magnetically hard and magnetically soft phases on the magnetic properties of Nd2Fe14B + alfa-Fe nanocrystalline magnets, as produced by the method of mechanical alloying, has been established. The phase composition of specimens was determined using X-ray diffractometry and Mössbauer spectroscopy. The Mössbauer examination showed that as the powder milling times increased, the content of the Nd2Fe14B phase increased from 42.8% (after the milling time of 10 h, with a grain size of 44.8 nm) to 66.3% (after the milling time of 48 h, with a grain size of 37.3 nm) and then decreased to 40.3% after 120 h of milling. On the other hand, the content of the magnetically soft phase alfa-Fe initially decreased (from 27.7%), reaching a minimum after the milling time of 48 h (17.4%) and then increasing to 36.9% after 120 h of milling

Phase Structure in Fe-Cr-Co Permanent Magnet Alloy

The Mössbauer spectroscopy, electron microscopy and magnetization measurements were used in order to describe structural changes in Fe$\text{}_{58.75}$Cr$\text{}_{29.4}$Co$\text{}_{11.85}$ alloy during magnetic hardening. Multiphase structure was found in alloy with best magnetic properties

Phase constitution of an LaFe11.0Co0.8(Si0.4Al0.6)1.2 alloy investigated by Mössbauer spectroscopy

In the present work the phase constitution and magnetic ordering of the magnetocaloric LaFe11.0Co0.8(Si0.4Al0.6)1.2 alloy in the as-cast state and after annealing at 1323 K for 1 h (in case of ribbons) and 49 days (in case of bulk) were studied. For bulk and ribbon samples in as-cast state three crystalline phases were identified: dominant ferromagnetic alfa-Fe, minor ferromagnetic La(Fe,Co)Si and traces of paramagnetic La(Fe,Si)13 phase. Appropriate heat treatment resulted in the evolution of phase constitution of the alloy, where two crystalline phases were developed: the dominant paramagnetic La(Fe,Si)13 phase and a minor fraction of the ferromagnetic alfa-Fe for both bulk and ribbon samples

Measurements of Magnetocaloric Effect in LaFe11.14Co0.66Si1.2−xAlxLaFe_{11.14}Co_{0.66}Si_{1.2-x}Al_{x} (x=0.1, 0.2, 0.3) Alloys

In the present work, phase constitution and thermomagnetic properties of $LaFe_{11.14}Co_{0.66}Si_{1.2-x}Al_{x}$ (where x = 0.1, 0.2, 0.3) alloys were investigated. Ingot samples were obtained by arc-melting under the low pressure of Ar atmosphere. Subsequently samples were annealed at 1323 K for 15 days. X-ray diffraction of all samples revealed coexistence of two crystalline phases dominant $La(Fe,Si)_{13}$-type and minor bcc α -Fe. Furthermore, the magnetic measurements at various temperatures allowed to study the Curie temperature, magnetic entropy changes and relative cooling power