• Resources Recycling
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• v.6 no.4
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• pp.31-37
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• 1997

The Mg-ferrite powders were recovered from acid leaching Mg waste by hydrothermal method. Recovering conditions ofMg-Ferrite were investigated m this system and the powders prepared were characterized, using X-ray analysis, chemicalanalysis, SEM. TEM, and VSM. In this study, pH of solution and the kind of neutralizer wcre important factors on thecharacteristics of the product. The optimum condition of recovering MgPenite was the mole ratio of Fe" : Mg"=2'1, reactiontemperature : ZOWC, reaction time.lhr, at pH=lZ, and Oi partial pressure af 2000 psi. And the powders ~ccovered have amonodispersed and spherelike shapes with the narrow sue distribulion.ow sue distribulion.

• Korean Journal of Metals and Materials
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• v.48 no.7
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• pp.639-643
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• 2010

Nanopowder of FeAl was synthesized by high energy ball milling. Using the pulsed current activated sintering method, a dense nanostuctured FeAl was consolidated within 2 minutes from mechanically synthesized powders of FeAl and horizontally milled powders of Fe+Al. The grain size and hardness of FeAl sintered from horizontally milled Fe+Al powders and high energy ball milled FeAl powder were 150 nm, 50 nm and $466\;kg/mm^2$, $574\;kg/mm^2$, respectively.

• Korean Journal of Metals and Materials
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• v.50 no.2
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• pp.176-182
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• 2012

The main purpose of this study was to evaluate the endurance against Al alloy melts and wear resistance of an in-situ synthesized titanium matrix composite (TMC) sleeve for aluminum alloy die-casting. The conventional die-casting shot sleeve material was STD61 tool steel. TMCs have great thermal stability, wear and oxidation resistance. The in-situ reaction between Ti and $B_4C$ leads to two kinds of thermodynamically stable reinforcements, such as TiBw and TiCp. To evaluate the feasibility of the application to a TMCs diecasting shot sleeve, the interfacial reaction behavior was examined between Al alloys melts with TMCs and STD61 tool steel. The pin-on-disk type dry sliding wear test was also investigated for TMCs and STD61 tool steel.

• Journal of the Korean Ceramic Society
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• v.31 no.11
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• pp.1249-1258
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• 1994

Titanium carbide was synthesized by reacting the prepared titanium powder and carbon black using SHS method sustains the reaction spontaneously, utilizing heat generated by the exothermic reaction itself. In this process, the effect of the particle size of titanium powder on combustion temperature and combustion wave velocity was investigated. By controlling combustion temperature and combustion wave velocity via mixing Ti and C powder with TiC, the reaction kinetics of TiC formation by SHS method was considered. Without reference to the change of combustion temperature and combustion wave velocity, TiC was easily synthesized by combustion reaction. As the particle size of titanium powder was bigger, or, as the amount of added diluent(TiC) increased, combustion temperature and combustion wave velocity were found to be decreased. The formation of TiC by combustion reaction in the Ti-C system seems to occur via two different mechanisms. At the beginning of the reaction, when the combustion temperatures were higher than 2551 K, the reaction was considered to be controlled by the rate of dissolution of carbon into a titanium melt with an apparent activation energy of 148 kJ/mol. For combustion temperatures less than 2551 K, it was considered to be controlled by the atomic diffusion rate of carbon through a TiC layer with an apparent activation energy of 355 kJ/mol. The average particle size of the synthesized titanium carbide was smaller than that of the starting material(Ti).

• Korean Journal of Materials Research
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• v.5 no.7
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• pp.869-879
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• 1995

TiAi intermetallic compound has been extensively studied for possible high temperature structural applications because of its high specific strength at high temperature, high creep resistance, and good oxidation resistance at elevated temperatures. In addition to its good properties, an economic manufacturing routes should be developed for this material to be used more extensively. One of the promising route in manufacturing TiAl intermetallics is the Self-propagating High-temperature Synthesis (SHS) method. Thus in this study, an attempt was made to study the mechanism of the SHS process in TiAl synthesis. The composition of the sample was Ti-(45, 50, 53)at% Al and the microstuctures of the products were analyzed using optical microscope and scanning electron microscope. When the phases formed at the main SHS reaction of whicyh combustion temperature is higher than the melting temperature of aluminum were identified as TiAl and Ti$_3$Al ; Ti$_3$Al cores surrounded by TiAl phase. In order to increase the combustion temperature, carbon was added 5 and 10at.%. When the carbon content was 10at.%, the heat of the reaction was large enough to melt the phase formed and that is consistent with the theoretical calculation results of the adiabatic temperature. The combution temperatue, which was measured by a computer data acquisition system, increased with the carbon content. The phases formed from the reaction involving the carbon added were indentified as TiAl and Ti$_2$AlC using XRD. The vickers hardness of the reaction product increased with the carbon content.

• Korean Journal of Materials Research
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• v.8 no.11
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• pp.987-992
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• 1998

Titanium aluminide intermetallic compound was formed from high purity elemental Ti and A1 foils by selfpropagating, high-temperature synthesis(SHS1 in hot press. Formation of $TiAl_3$ intermetallics at the interface between Ti and Al foil was observed to be controlled by temperature, pressure and heating rate. Especially, the heating rate is the most important role to form intermetallic compound by SHS reaction. According to DTA experiment, the SHS reactions appeared at two different temperatures below and above the melting point of Al. It was also observed that both SHS reaction temperatures increased with increasing the heating rate. After the SHS reaction of alternatively layered 10 Ti and 9 A1 foils at the heating rate of $20^{\circ}C$/min, the $700\mu\textrm{m}$ thick titanium aluminide sheet was formed by heat treatment at $810^{\circ}C$ for 4hours.

• Korean Journal of Materials Research
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• v.6 no.7
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• pp.709-715
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• 1996

The influence of an electric field on the combustion synthesis of ${Ti}_{5}{Si}_{3}$-x ${ZrO}_{2)$(0 $\leq$ x $\leq$0.6)was investigated. Composite of X $\geq$0.45 can only be synthesized in the presence of an electric field. Although in the absence of an electri field the system with x = 0.45 and x=0.6 can sustain a nonsteady combustion wave, the reaction is not complete. That is, an unstable wave propagates to the middle of the sample and them becomes extinguished. Wave velocity o the ${Ti}_{5}{Si}_{3}-{ZrO}_{2}$ Composites slightly increases with the imposition of external field across the sample.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1203-1204
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• 2006

Cu-$TiB_2$ nanocomposite powders were synthesized by combining high-energy ball-milling of Cu-Ti-B mixtures and subsequent self-propagating high temperature synthesis (SHS). Cu-40wt.%$TiB_2$ powders were produced by SHS reaction and ball-milled. The milled SHS powder was mixed with Cu powders by ball milling to produce Cu-2.5wt.%$TiB_2$ composites. $TiB_2$ particles less than 250nm were formed in the copper matrix after SHS-reaction. The releative density, electrical conductivity and hardness of specimens sintered at $650-750^{\circ}C$ were nearly 98%, 83%IACS and 71HRB, respectively. After heat treatment at 850 to $950^{\circ}C$ for 2 hours under Ar atmosphere, hardness was descedned by 15%. Our Cu-$TiB_2$ composite showed good thermal stability at eleveated temperature.

• Resources Recycling
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• v.10 no.5
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• pp.16-21
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• 2001

Ultrafine $Mg(OH)l_2$and MgO powders were recovered from the waste solution containing $Mg^{++}$ which was a by-product of SHS (Self-propagating High temperature Synthesis)process. The optimum experimental conditions to prepare $Mg(OH)_2$were 13.0 of pH and 0.7M of $Mg^{++}$ content with addition of 9M of KOH as a pH regulator in acid leaching solution. Complete pre-cipitation of Mg(OH)$_2$from $Mg^{++}$ was realized at that condition. The dehydration reaction of the prepared Mg(OH)$_2$was studied by DSC, and the result was used for calcination process. In order to obtain MgO powder, dried Mg(OH)2 powder was calcined at $400~450^{\circ}C$. Particle size and shape of the prepared $Mg(OH)_2$and MgO powder was similar to those of the commercial powders.

• Journal of the Korean Ceramic Society
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• v.41 no.1
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• pp.62-68
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• 2004

In this study, SHS process has been employed to fabricate porous $MoSi_2$ material with electric-resistive heating capability through the control of pore size. The preform for SHS reaction was consisted of molybdenum powder with different sizes and silicon powder with different contained quantity. The size of the $MoSi_2$ particles thus formed was determined by the generated heat of combustion, not by the size of molybdenum powder. However, the pore size of $MoSi_2$ composite was proportional to the particle size of molybdenum powder. that is the coarser the molybdenum powder used, the larget the formed pore size. Based on these results, the porous $MoSi_2$ composite could be fabricated with a desired pore size. By orienting the porous molybdenum disilicide-based material in the form of pore size gradient, porous materials used for filters with improved dirt-holding capacity can be manufactured.