• Resources Recycling
• /
• v.24 no.4
• /
• pp.56-60
• /
• 2015

Fine particle classification was performed using products obtained from primary classification process after flotation for efficient application of tailing. The cut size increased with decreasing input pressure from 0.1 MPa to 0.3 MPa and increasing pulp density from 5% to 15% using 2-inch hydrocyclone. The median sizes of overflow and underflow were $6.56{\mu}m$ and $55.45{\mu}m$, respectively at 0.3 MPa with 5% pulp density. The imperfection became closed to ideal separation with increasing the pulp density and decreasing the input pressure. The water content decreased with increasing the pulp density, but the effect of input pressure could be ignored. The water content of underflow was 27.9% at 0.3 MPa with 15% pulp density.

• Resources Recycling
• /
• v.26 no.6
• /
• pp.97-101
• /
• 2017

Metal foams have a cellular structure consisting of a solid metal containing a large volume fraction of pores. In particular, open pores which are penetrable pores are necessary for industrial applications such as in high temperature filters and as support for catalysts. In this study, Fe foam with greater than 90% porosity and 2-mm pore size was successfully fabricated using a slurry coating process and the pore properties were characterized. The Fe and $Fe_2O_3$ powder mixing ratios were controlled to produce Fe foam samples with different pore sizes and porosity. First, the slurry was prepared through the uniform mixing of powders, distilled water, and polyvinyl alcohol(PVA). The amount of slurry coated with the PU foam increased with increasing $Fe_2O_3$ mixing powder ratio, but the shrinkage and porosity of the Fe foams decreased, respectively, with increasing $Fe_2O_3$ mixing powder ratio.

• Journal of the Korean Society of Safety
• /
• v.20 no.4 s.72
• /
• pp.14-19
• /
• 2005

One area in which composites have been used rather extensively is for fabricating pressure vessel. These structures can be readily manufactured by filament winding, which is, as far as composite fabrication techniques are concerned, a relatively inexpensive method for producing composite structures. Unfortunately, the higher strength material and fabrication costs are not the only disadvantages of fiber-reinforced polymer composites when they are compared to metals. Additionally, these materials tend to exhibit brittle behavior. This is of particular concern when they are subjected to a low-velocity impact during routine handling a significant amount of structural damage can be introduced into the composites. The goals of this paper are to understand the impact damage behavior and identify the effect of surface coating materials on impact resistance in filament wound composite pressure vessels. For these, a series of low velocity impact tests was performed on specimens cutting from the full scale pressure vessel by the instrumented impact testing machine. The specimens are classified into two types with and without surface protective material. The visualization for impact damage is made by metallurgical microscope. Based on the impact force history and damage, the resistance parameters were employed and its validity in identifying the damage resistance of pressure vessel was reviewed. As the results, the impact resistance of the filament wound composites and its dependency on the protective material were evaluated quantitatively.

• Journal of Powder Materials
• /
• v.15 no.2
• /
• pp.95-100
• /
• 2008

The investigation is to modify the mechanical and chemical properties of Mg alloys using a combination of rapid solidification and surface treatment. As the first approach, $Mg_{95}Zn_{4.3}Y_{0.7}$ was gas atomized and pressure sintered by spark plasma sintering process (SPS), showing much finer microstructure and higher strength than the alloys as cast. Further modification was performed by treating the surface of PM Mg specimen using Plasma electrolytic oxidation (PEO) process. During the PEO processing, MgO layer was initiated to form on the surface of Mg powder compacts, and the thickness and the density of MgO layer were varied with the reaction time. The thickening rate became low with the reaction time due to the limited diffusion rate of Mg ions. The surface morphology, corrosion behavior and wear resistance were also discussed.

• Journal of Sensor Science and Technology
• /
• v.10 no.1
• /
• pp.16-23
• /
• 2001

Comparing with general optical fiber sensors performing localized measurement, distributed optical fiber sensors can measure along an optical fiber, and they have large measuring range. The surface-mounting method with epoxy adhesive is general in attaching optical fiber sensors to structures, This is also appliable to the structural integrity monitoring with Brillouin-scattering distributed optical fiber sensors. In this paper, Brillouin-scattering distributed optical fiber sensors, which are attached to the surface of a structure with epoxy adhesive, was verified with the finite element method. From the analysis results of strain transfer through the structure, optical fiber coating, cladding and core, the strain transfer rates were calculated. And the influence of the epoxy free-end was also studied.

• Computers and Concrete
• /
• v.29 no.1
• /
• pp.31-45
• /
• 2022

Experimental and numerical simulation were used to investigate the effects of angle and number of T shape non-persistent crack on the shear behaviour of crack's bridge area under uniaxial compressive test. concrete samples with dimension of 150 mm×150 mm×40 mm were prepared. Within the specimen, T shape non-persistent notches were provided. 16 different configuration systems were prepared for T shape non-persistent crack based on two and three cracks. In these configurations, the length of cracks were taken as 4 cm and 2 cm based on the cracks configuration systems. The angle of larger crack related to horizontal axis was 0°, 30°, 60° and 90°. Similar to cracks configuration systems in the experimental tests, 28 models with different T shape non-persistent crack angle were prepared in numerical model. The length of cracks were taken as 4 cm and 2 cm based on the cracks configuration systems. The angle of larger crack related to horizontal axis was 0°, 15°, 30°, 45°, 60°, 75° and 90°. Tensile strength of concrete was 1 MPa. The axial load was applied to the model. Displacement loading rate was controlled to 0.005 mm/s. Results indicated that the failure process was significantly controled by the T shape non-persistent crack angle and crack number. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. Furthermore, it was shown that the compressive behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the crack number and crack angle. The strength of samples decreased by increasing the crack number. In addition, the failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods (PFC2D).

• Journal of Convergence for Information Technology
• /
• v.12 no.2
• /
• pp.149-156
• /
• 2022

In this paper, it was attempted to form a titanium (Ti: Titanium) thin film using the atmospheric pressure plasma process technology for the conductor, which is the main component of the optical sensor. The atmospheric plasma equipment was remodeled. A 4-inch Ti target for sputter was etched using CF4 gas, and the by-product was coated on a glass sample. These by-products were formed up to about 2 cm, and could be divided into 15 areas according to color. Surface shape and constituent elements were analyzed using scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), respectively. Electrical properties using 4-point probe equipment were also measured. If the process is performed by positioning the sample at about 4.5 mm to 5 mm from the target, a uniform Ti thin film will be deposited. However, it was found that the thin film contained a significant amount of fluorine, which greatly affects the electrical properties of the thin film. Therefore, additional experiments and studies should be performed to remove or minimize fluorine during deposition.

• Transactions of the Korean hydrogen and new energy society
• /
• v.34 no.6
• /
• pp.631-640
• /
• 2023

This study selected Eco-AZ91 MgH₂, which shows high enthalpy as a material for this purpose, as the basic material, and analyzed the change in characteristics by synthesizing TiNi as a catalyst to control the thermodynamic behavior of MgH₂. In addition, the catalyst dispersion technology using graphene oxide (GO) was studied to improve the high-temperature aggregation phenomenon of Ni catalyst and to secure a source technology that can properly disperse the catalyst. XRD, SEM, and BET analysis were conducted to analyze the metallurgical properties of the material, and TGA and DSC analysis were conducted to analyze the dehydrogenation temperature and calorific value, and the correlation between MgH₂, TiNi catalyst, and GO reforming catalyst was analyzed. As a result, the MgH₂-5 wt% TiNi at GO composite could lower the dehydrogenation temperature to 478-492 K due to the reduction of the catalyst aggregation phenomenon and the increase in the reaction specific surface area, and an experimental result for the catalyst dispersion technology by GO could be ensured.

• Korean Journal of Materials Research
• /
• v.7 no.2
• /
• pp.102-106
• /
• 1997

Micro gas sensors including thin film catal) tic type require stress-free memhrancs for etch stop of Si anisotropic etching and sublayer of sensing elements hecause stress is one of the main factors affecting breakdown of thin membranes. This paper reports the effects of deposition conditions on stress and refractive index of $SiN_{x}/SiO_{x}/(NON)$ films deposited by low pressure c11ernic;rl vapor deposition(L, t'CVI)) 2nd reactve sputtering. In the case of I.PCVI1, the stresses of $SiN_{x}$ and NON films arc $7.6{\times}10^{8}dyne/cm^2$ and $3.3{\times}10^{8}dyne/cm^2$, respectibely, and the refractive indices are 3.05 and 152, respectively. In the cxse oi the sputtered SiN, , compressi\e stress decreased in magnitude and then turned to tensility as increasing proc, ess pressure by lmtorr to 30mtorr and cicreasmg applied power density by $2.74W/cm^2$ to $1.10W/cm^2$. The hest value of film stress obt;~ined under condition of lOmtorr and $1.37W/cm^2$ in this' experiment was $1.2{\times}10^{9}dyne/cm^2$ cnnipressive. The refr~ict~ve index decreased from 2 05 to 1 89 as decreasing applied power density by lnitorr to 3Orntorr and increasing process pressure hy $2.74W/cm^2$ to $1.10W/cm^2$. Stresses of films deposited by both LPCVL) and sputtering decreased as incre;lsing temperature and showed plastic behavior as decreasing temperature.

• Korean Journal of Materials Research
• /
• v.10 no.3
• /
• pp.246-252
• /
• 2000

Thermoelectric properties of the $Bi_2(Te_{0.85}Se_{0.15})_3$ alloy, prepared by mechanical alloying and hot pressing, were investigated with the variation of the hot-pressing temperature ranging from $300^{\circ}C$ to $550^{\circ}C$. Contrary to the p-type behavior of single crystal, the hot-pressed $Bi_2(Te_{0.85}Se_{0.15})_3$ alloy exhibited n-type conduction without addition of donor dopant. When the $Bi_2(Te_{0.85}Se_{0.15})_3$ powders were annealed in $(50{\%}\;H_2+50{\%}\;Ar)$ atmosphere, the hot-pressed specimens exhibited a positive Seebeck coefficient due to the reduction of the electron concentration by removal of the oxide layer on the powder surface and annealing-out of the excess Te vacancies. Figure-of-merit of the hot-pressed $Bi_2(Te_{0.85}Se_{0.15})_3$ alloy was improved by hot pressing at temperatures above $450^{\circ}C$, and the maximum value of $1.92{\times}10^{-3}/K$ was obtained for the specimen hot-pressed at $550^{\circ}C$.