• Transactions of Materials Processing
• /
• v.24 no.1
• /
• pp.44-51
• /
• 2015

The current study seeks to examine the effects of V and C additions on the mechanical and low thermal expansion properties of a high strength invar base alloy. The base alloy (Fe-36%Ni-0.9%Co-2.75%Mo-0.7Cr-0.23Mn-0.17Si-0.3%C, wt.%) contains $Mo_2C$ carbides, which form as the main precipitate. In contrast, alloys with additions of 0.4%V+0.3%C (alloy A) or 0.4%V+0.45%C (alloy B) contain $Mo_2C$+[V, Mo]C carbides. The average thermal expansion coefficients of these high strength invar based alloys were measured in the range of $5.16{\sim}5.43{\mu}m/m{\cdot}^{\circ}C$ for temperatures of $15{\sim}230^{\circ}C$. Moreover, alloy B showed lower thermal expansion coefficient than the other alloys in this temperature range. For the mechanical properties, the [V, Mo]C improved hardness and strengths(Y.S. and T.S.) of the high strength invar base alloy. T.S.(tensile strength) and Y.S.(yield strength) of hot forged alloy B specimen were measured at 844.6MPa and 518.0MPa, respectively. The tensile fractography of alloy B exhibited a ductile transgranular fracture mode and voids were initiated between the [V, Mo]C particles and the matrix. Superior properties of high strength and low thermal expansion coefficient can be obtained by [V, Mo]C precipitation in alloy B with the addition of 0.4%V and 0.45%C.

• Korean Journal of Materials Research
• /
• v.31 no.11
• /
• pp.593-600
• /
• 2021

Herein, a series of g-C₃N₄ modified Bi₂MoO₆ nanocomposites using Bi₂MoO₆ and melamine as original materials are fabricated via sintering process. For presynthesis of Bi₂MoO₆ an ultrasonic-assisted hydrothermal technique is researched. The structure and composition of the nanocomposites are characterized by Raman spectroscopy, X-ray diffraction (XRD), and high-resolution field emission scanning electron microscopy (SEM). The improved photoelectrochemical properties are studied by photocurrent density, EIS, and amperometric i-t curve analysis. It is found that the structure of Bi₂MoO₆ nanoparticles remains intact, with good dispersion status. The as-prepared g-C₃N₄/Bi₂MoO₆ nanocomposites (BMC 5-9) are selected and investigated by SEM analysis, which inhibits special morphology consisting of Bi₂MoO₆ nanoparticles and some g-C₃N₄ nanosheets. The introduction of small sized g-C₃N₄ nanosheets in sample BMC 9 is effective to improve the charge separation and transfer efficiency, resulting in enhancing of the photoelectric behavior of Bi₂MoO₆. The improved photoelectronic behavior of g-C₃N₄/Bi₂MoO₆ may be attributed to enhanced charge separation efficiency, photocurrent stability, and fast electron transport pathways for some energy applications.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.5 no.6
• /
• pp.558-561
• /
• 2004

The morphology of silica supported $MoO_{3}$ catalysts, which was prepared by impregnation of ammonium heptamolybdate(AHM) with various surface loadings up to 4 atoms $Mo/nm^{2}$, was studied using x-ray diffraction(XRD). All morphologies of silica supported $MoO_{3}$ appear to be thermodynamically driven. For high loaded catalysts there appeared three states: a sintered and well-dispersed hexagonal state at moderate temperature calcination($300^{\circ}C$), and a sintered orthorhombic state at high temperature calcination($500^{\circ}C$). Whereas the sintered orthorhombic phase is detected by XRD at loadings in excess of 1.1 atom $Mo/nm^{2}$, the well-dispersed hexagonal phase is not detected even until 4.0 $atomsMo/nm^{2}$. The higher apparent dispersion of the hexagonal phase may arise from some role of ammonia which results in a stronger $MoO_{3}-SiO_{2}$ surface interaction.

• Journal of Powder Materials
• /
• v.13 no.1 s.54
• /
• pp.10-17
• /
• 2006

Model experiment was introduced to obtain the formation of a core/rim structure by only liquid phase reaction in Ti(C, N)-based cermet alloys. Infiltrated Ti(C, N)-Ni, $MO_2C-Ni$, and TaC-Ni cermets were bonded to sandwiched specimen by heat treatment $1450^{\circ}C$ for 5hr. With nitrogen addition, both (Ti, Mo) (C, N) and (Ti, Ta) (C, N) rim structure was nucleated around comer of cuboidal Ti(C, N) core. However, equilibrium shapes of(Ti, Mo) (C, N) and (Ti, Ta) (C, N) rim were different possibly due to the effect of interface energy. The core/rim and rim! binder interfaces were parallel to each other with TaC addition, while rotated to each other with $MO_2C$ addition.

• Journal of Powder Materials
• /
• v.6 no.2
• /
• pp.178-185
• /
• 1999

MoSi$_2$-TiC composite powders were fabricated by in-situ reaction through mechanical alloying. Also the monolithic MoSi$_2$ as well as TiC were synthesiced by mechanical alloying for comparison. An abrupt increase of vial surface temperature was detected due to a sudden reaction between elemental powders during milling. The reaction time for synthesis of composite powders decreased with increasing the content of (Ti+C) powder. It was found that a significant decrease of Ti grain size was observed with increasing the milling time. And the synthesis reaction of MoSi$_2$-TiC composite powders were largely dependent on the reaction between Ti and C powders.

• Asian-Australasian Journal of Animal Sciences
• /
• v.18 no.2
• /
• pp.221-225
• /
• 2005

An in vitro study was conducted to examine the effect of monensin or fish oil addition on bio-hydrogenation of $C_{18^-} unsaturated fatty acids and CLA production by mixed ruminal bacteria when incubated with safflower oil. Commercially manufactured concentrate (1%, w/v) with safflower oil (0.2%, w/v) were added to mixed solution (600 ml) of strained rumen fluid and McDougalls artificial saliva (control). Monensin $Rumensin^{(R)}$, 10 ppm, w/v, MO), mixed fish oil (0.02%, w/v, absorbed to 0.2 g alfalfa hay, FO) or similar amounts of monensin and fish oil (MO+FO) to MO and FO was also added into the control solution. All the culture solutions prepared were incubated in the culture jar anaerobically at $39^{\circ}C$ up to 12 h. Higher pH (p<0.047) and ammonia concentration (p<0.042) were observed from the culture solution containing MO at 12 h incubation than those from the culture solutions of control or FO. The MO supplementation increased (p<0.0001-0.007) propionate proportion of culture solution but reduced butyrate proportion at 6 h (p<0.018) and 12 h (p<0.001) of incubations. Supplementation of MO or MO+FO increased (p<0.001) the proportions of $C_{18:2}$. The MO alone reduced (p<0.022-0.025) the proportion of c9,t11-CLA compared to FO in all incubation times. The FO supplementation increased the proportion of c9,t11-CLA. An additive effect of MO to FO in the production of c9,t11-CLA was observed at 6 h incubation. In vitro supplementation of monensin reduced hydrogenation of $C_{18^-}$UFAs while fish oil supplementation increased the production of CLA.

• Journal of Korea Foundry Society
• /
• v.14 no.1
• /
• pp.52-61
• /
• 1994

The effect of Ni addition, on the mechanical properties and fracture characteristics of Mo-Cu and Mo-Ni-Cu alloyed ductile iron austenitized at $900^{\circ}C$ and austempering temperatures of $250^{\circ}C$, $300^{\circ}C$ and $350^{\circ}C$. The tensile strength, yield strength and hardness are decreased and elongation and impact value are increased in both Mo-Cu and Mo-Ni-Cu alloyed austempered ductile iron, with increased austempering temperature. According to the austempering temperature are increased, the amount of retained austenite are increased. Maximum value of fracture toughness is obtained at $350^{\circ}C$ austempering temperature at this condition, the amount of retained austenite came to 40% in Mo-Ni-Cu alloyed ADI and 34% in Mo-Cu alloyed ADI. The fracture surface of ADI which had represented high toughness are showed a quasi-cleavage pattern and a dimple pattern with micro void. Comparing the fracture characteristics of Mo-Cu alloyed ADI with that of Mo-Ni-Cu alloyed ADI, the latter was superior to the former.

• Elastomers and Composites
• /
• v.40 no.3
• /
• pp.174-180
• /
• 2005

Sonochemical synthesis of fullerene oxides $[C_{70}O_n](n=1{\sim}2)$ by fullerene$[C_{70}]$ and metal hexacarbonyl complexes $M(CO)_6$(M=Cr, Mo, W) took place under air atmosphere. The reactivity of fullerene$[C_{70}]$ and several metal hexacarbonyl complexes $M(CO)_6$(M=Cr, Mo, W) under same ultrasonic condition increased in the order of $Mo(CO)_6$ > $W(CO)_6$ > $Cr(CO)_6$. The MALDI-TOF-MS, UV-visible spectra, and HPLC analysis confirmed that the products of sonochemical reaction were $[C_{70}O_n](n=1{\sim}2)$.

• 대한공업교육학회지
• /
• v.31 no.1
• /
• pp.200-210
• /
• 2006

This C-ring test, normally employed for evaluating susceptibility to stress-corrosion cracking, was determined to be a suitable small scale test to evaluate PWHT(Post-Weld Heat Treatment) cracking susceptibility. This test is possible to incorporate an actual weld, to introduce a notch into the coarse grained HAZ(Heat Affected Zone), to load the coarse grained HAZ any level of stress ad, most importantly, since the C-ring is an approximately constant strain type test, the stress decreases with time at temperature in a manner similar to that of an actual steel weldment. The procedure employed in making the C-ring was presented in the experimental procedure section, however, several points deserve further discussion. The walls of the weld groove are made along radial lines form the center of th var in order to obtain an HAZ which is oriented perpendicular to the walls of the machined C-ring. Therefore, the plane of maximum stress will be aligned through the HAZ and, therefore, crack propagation will not be forced to deviate form the plane of maximum stress in order to remain in the coarse grained HAZ as is the case with the Y groove test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.05a
• /
• pp.118-122
• /
• 1996

1wt% Pt/MoO$_3$ gas sensors for detecting H$_2$ gas were fabricated by the pressed pellet method and surface structures of Pt/MoO$_2$ were investigated by TEM and XRD. It was observed that as the calcination temperature is increased, the overlayers of MoO$_3$ on Pt are produced, but the Cl content in PtCl$\_$x/ are decreased. H$_2$ gas sensing properties in N$_2$ ambient and in air ambient were investigated, respectively, and Pt/MoO$_3$ had high sensitivity at low working temp ; 7.8% at 50$^{\circ}C$, 97.7% at 100$^{\circ}C$, 97.1% at 150$^{\circ}C$ when the specimens are treated at 400$^{\circ}C$, and 99.6% at 150$^{\circ}C$ when they are treated at 200$^{\circ}C$. It shows the development of a low-power type sensor is possible by using Pt/MoO$_3$.