• Journal of the Korea Institute of Military Science and Technology
• /
• v.24 no.4
• /
• pp.401-407
• /
• 2021

To confirm the change of muzzle velocity and the most suitable probability distribution model of the 155 mm K9 howitzer barrel with chrome plating and changed rifling. Using a statistical program, the muzzle velocity were plotted on a normal distribution, a 2-parameter and 3-parameter Weibull distribution on a probability paper. Also, statistical parameters were estimated and muzzle velocity fitness test and probability of K676 charge were plotted. In both the chrome-plated with standard rifling and changed rifling for K9 barrel, the 2-parameter and 3-parameter Weibull distribution were skewed to the left compared to the normal distribution. It was confirmed that the muzzle velocity of the K9 barrel with chromium-plated is suitable for the normal distribution and 3-parameter Weibull distribution model.

• Nuclear Engineering and Technology
• /
• v.55 no.4
• /
• pp.1468-1475
• /
• 2023

Enhancement of wear resistance of components used in fast reactors is necessary for long service life of the components. Plasma nitriding is a promising surface modification technology to impart high hardness and improved wear resistance of various steel components. This study discusses the characterization of chrome nitrided SS316L casing ring used in secondary sodium pump of fast breeder reactor and its stability under long term sodium exposure. Microstructural and hardness analysis showed that stress relieved component could be chrome nitrided successfully to a thickness of about 100 ㎛. Assessment of in-sodium performance of the chrome nitrided casing ring subjected to long term exposure up to 5000h at 550℃, showed retention of chrome nitrided layer with a case depth almost similar to that before sodium exposure. A slight decrease in the hardness was observed due to prolonged high temperature sodium exposure. Tribological studies indicate very low coefficient of friction indicating the retention of good wear resistance of the coating even after long term sodium exposure.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.6 no.1
• /
• pp.43-52
• /
• 1998

The objective of this study is to investigate the optimum conditions of extracting collagen without chrome ion from the leather waste. The effect of temperature, pH, and the concentration of alkaline solution on the collagen extraction has been studied. The result indicated that the incipient denatured temperature of collagen measured by viscosity was $25^{\circ}C$ and the complete denatured temperature was $31.5^{\circ}C$. The optimum solubilization condition for temperature was between $15^{\circ}C$ and $20^{\circ}C$, pH was 1.5, the concentration of alkaline solution was 3% of sodium hydroxide. The almost complete chrome ion separation was possible around the pH of 1.5. The separation efficiency of chrome ion from tannery waste was more than 99.5%. Extraction efficiency of crude protein from leather waste was about 89.5%. The hydroxyproline and collagen content in the extracted crude protein were 8.53% and 63.62%, respectively.

• Journal of the Korean Solar Energy Society
• /
• v.33 no.3
• /
• pp.27-35
• /
• 2013

One of the most important factors that have a large influence on performance of the solar water heater system is performance of the solar collector, more detailedly, coating technology on the surface of the solar collector, which can provide high solar absorptance and low emittance. The core of the coating technology is to coat solar selective surfaces. In this study, various performance experiments are carried out using $Cr_2(SO_4)_3{\cdot}15H_2O$ coating technology. Here, IGBT(Insulated Gate Bipolar Transistor) of 5000A-15V was used as the surface processing rectifier which can stably output power and also can control voltage and current. The plating solution mainly contains black chrome$^{+3}$ concentration, H-y Conductivity, N-u Complex, NF Additive and NC-2 Wetter. Before applying the black chrome coating on the copper plate, optimal conditions are provided by using various preprocessing methods such as removal of fat, activation, electrolytic polishing, nickel strike, copper sulfate plating and bright neckel plating, and then the automatic continuous coating experiment are performed according to plating time and cathode current density. In the experiment, after the removal of fat, chemical polishing, nickel strike and activation processes as the preprocessing methods, the black chrome coating was performed in a plate solution temperature of $28^{\circ}C$ and a cathode current density of $18A/cm^2$ for 90 seconds. The thickness of chrome and nickel on the coated plate is $0.389{\mu}m$, $159{\mu}m$ respectively. As a result of the coating experiment, it showed the most excellent performance having a high solar absorptance of 98% and a low emittance of $5{\pm}1%$ when the black chrome surface had a thickness of $0.398{\mu}m$.

• Korean Journal of Metals and Materials
• /
• v.48 no.4
• /
• pp.277-288
• /
• 2010

The hot corrosion properties of heat-resistant steels were investigated in an oxidation atmosphere including artificial ash and sulfur dioxide. The heat-resistant steels of T22, T92, T122, T347HFG, Super304H and HR3C were evaluated at 620, 670 and $720^{\circ}C$ for 400 hours. The relationship between the corrosion rate and the temperature followed a bell-shaped curve with a peak rate at around $670^{\circ}C$. The corrosion rates showed a decreasing tendency as the chrome contents of these steels increased from 2.15 wt.% to 24.5 wt.%, and austenitic steels had a lower corrosion rate than ferritic steels. Sulfidation by $SO_2$ as well as molten salt corrosion also had an effect on the total corrosion rate, especially showing an increase in the corrosion rate in ferritic steels. Regardless of the chrome content in the steels and irrespective of the test temperature, the corrosion scale was composed of an outer oxide and an artificial ash mixed layer, a middle oxide layer and inner sulfide, and a mixed oxide layer. As the chrome content increased, the proportion of chrome oxide in the corrosion scale increased. Before spalling of the corrosion scale, voids and cracks were initiated in the sulfide and the mixed oxide layer or at the interface with the substrate.

• Journal of Sericultural and Entomological Science
• /
• v.26 no.2
• /
• pp.26-31
• /
• 1984

In general, acid dyes been used for silk dyeing, but acid dyed silk shows weakness in color fastess, To improve this defect, the silk dyed with Acid Mordant Blue 13 was treated with chromes salts solution. Some mechanical properties and dyeing behaviors of the chrome mordant with dyed silk fabric were tested in this work. The tensile strength of silk fabric treated with chrome salts solution was decreased as the duration of treatment was increased. The mean rate constant (K) of photo-degradation was 1.019, and 1.047 after treated with Cr (III) and Cr (Ⅵ), respectively, whereas it was 1.304 in untreatment. The washing fastness of silk fabric also was improved by treatment with mordant and it was 3rd-4th grade and 4th grade when silk was treated with Cr (III) and Cr (Ⅵ), respectively, while untreatment gave 1st grade. The colour of dyed silk fabric was 2.5RP.3/10, but it was 5PB.4/3 and 5PB. 4/4 when the silk fabric was treated with Cr (III) for two hours and with Cr (Ⅵ) for one hour at 90$^{\circ}C$, respectively.

• Solar Energy
• /
• v.9 no.2
• /
• pp.69-77
• /
• 1989

The thermal degradation of electroplated black chrome coating on Ni substrates has been investigated by using Auger electron spectroscopy technique. The sample was prepared by electroplating at $20^{\circ}C$ for 20 seconds with the current density at $0.4A/cm^2$. Its surface oxidation process was investigated with 1 hour annealed sample for a temperature range of $300-550^{\circ}C$. While its optical solar absorption was dominated by fine metallic Cr particles, thermal degradation was occurred primarily by oxidation of metallic Cr particles as increasing the annealing temperature.

• Journal of the Korean institute of surface engineering
• /
• v.25 no.5
• /
• pp.263-269
• /
• 1992

To enhancing efficiency of hard chrome plating solution more highly, cathode current efficiency were surveyed connected with hardness of deposits, surface morphology, TEM analysis and corrosion test of anode materials. Efficiency war increased up to 26% values by adding catalyst and two kind of additives. With given bath composition and 6$0^{\circ}C$, 60A/d$\m^2$ electrolosis conditionss bright and micro cracked deposits were well obtained, which showed HV 1000 values. From corrosion tests, anode materials such as Pb-Te (0.02%) and Pb-Ag(1%) showed most anti-corrosive results. Through SEM micrograph observations, ef-fects of additives on levelling, brightness and micro crack properties of hard chrome deposits could be con-firmed. Also, through TEM analysis the fact that deposits from crack free solution or high speed solution were more fine than from sargent solution could be confirmed.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2003.05a
• /
• pp.61-61
• /
• 2003

It is important to know SIze distribution of defects In electroplated trivalent chrome layers because it significantly influences on performance of the layers. Most of the nano-scale defects are able to be introduced by hydrogen evolution during the plating. Little information is available on the nano-size defects. In this study, SANS was applied to determine the size distribution of nano-scale defects in the trivalent chrome layers prepared in a formate bath. The defect size and distribution was dependent upon plating conditions such as current density and applied voltage. SANS is one of useful techniques to determine the nano-scale defect in the electroplated layers.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.04a
• /
• pp.113-116
• /
• 2011

A total of 9 coating specimens were fabricated through 3 different processes to evaluate the availability and performance of a nickel/chrome coating for the protection of the inner wall of a thrust chamber operating on a condition of high temperature and pressure. Thickness and thermal conductivity of the specimens were measured and thermal shock test was conducted.