SHS 법에 의한 티타늄 수소화물 합성 및 티타늄 분말 제조에 관한 연구

하호,박승수,이희철 ( Ho Ha,Seung Soo Park,Hee Cheol Lee ) 한국공업화학회 1994 공업화학 Vol.5 No.2

SHS법에 의해 Ti-sponge(99.67%)를 수소화반응시켜 티타늄 수소화물을 합성한 다음, 이 분말을 탈수소시켜 티타늄 금속 분말을 제조하였다. 티타늄 수소화물 합성과정에서는 티타늄에 횹장된 수소의 양에 따라 티타늄 수소화물의 입도가 변하였으며, 수소의 압력이 높을수록, 연소파 전파 후 반응시간이 길수록 입도는 감소하였다. 탈수소 반응에서는 탈수소 시간이 길수록 탈수소된 티타늄 입자들이 소결 및 부분 용융되어 입도가 커지는 것으로 나타났다. Titanium powder prepared by dehydrogenating the titanium hydride which is synthesized by reacting Ti-sponge (99.67%) with hydrogen using the self-propagating high-temperature synthesis method. In the synthesis of titanium hydride, the particle size of the product was found dependent on the amount of hydrogen incorporated into the titanium such that the particle size of titanium hydride decreased with increasing hydrogen pressure and after-burn time. In the dehydrogenation process, as the dehydrogenation time increase, the particle size of titanium powder increased due to partial melting and sintering of titanium particles.

자체반응열 고온합성법에 의한 탄화티타늄 합성에 관한 메카니즘

하호,황규민,한희동,Ha, Ho,Hwang, Gyu-Min,Han, Hee-Dong 한국세라믹학회 1994 한국세라믹학회지 Vol.31 No.11

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).

알콕사이드와 사이알론 합성에 관한 연구

하호,이희철,Ho Ha,Heecheol Lee 대한화학회 1988 대한화학회지 Vol.32 No.3

$Al(OC_3H_7)_3$ 및 $Si(OC_2H_5)_4$, 알콕사이드를 합성하고 그 물질을 각각 또는 혼합가수분해하여 $Al_2O_3,\;SiO_2,\;Al_2O_3-SiO_2$계의 물질을 얻고 $Al_2O_3-SiO_2$계에 환원제로서 carbon black을 혼합하여 $N_2$분위기에서 환원질화반응시켜 고순도의 ${\beta}-sialon$ 초미분말을 합성하였다. 가수분해 과정에서는 반응조건이 가수분해반응에 미치는 영향을 알아보았고, 환원질화반응 과정에서는 중간생성물을 분석하여 반응경로를 추정하고 ${\beta}-sialon$의 생성반응에 대한 동력학적 고찰을 하였다. Fine powders of amorphous $Al_2O_3,\;SiO_2,\;Al_2O_3-SiO_2$ system were prepared by hydrolysis of solutions containing alkoxides, aluminium tri-isopropoxide and silicon tetra-ethoxide. High purity ultrafine ${\beta}-sialon$ powders were prepared by the carbothermal reduction-nitridation of amorphous $Al_2O_3-SiO_2$ powders mixed with carbon black as a reducing agent. In the hydrolysis step the effect of the factors such as pH, reaction temperature and amount of water on the conversion rate of alkoxides to oxides was investigated. In the carbothermal reduction-nitridation the reaction path was assumed by the analysis of intermediates formed in the process of ${\beta}-sialon$ synthesis and the reaction kinetics of ${\beta}-sialon$ formation was considered.

자체반응열 고온합성법을 이용한 Titanium Carbonitride의 합성에 관한 연구

하호,황규민,이희철,Ha, Ho,Hwang, Gyu-Min,Lee, Hee-Cheol 한국세라믹학회 1994 한국세라믹학회지 Vol.31 No.6

Using SHS(Self-propagating High-temperature Synthesis) method, the optimum synthetic condition of titanium carbonitride was established by controlling the parameters such as relative density of mixture (Ti+C), nitrogen pressure, additive amounts of titanium hydride(TiH1.924) and protecting heat loss. Under 1 atm nitrogen pressure, nitridation ratio with changing relative density of the sample compacts has a maximum (87.2%) at about 55%, and in the case of enveloping the pellet with a quartz tube, the highest nitridation ratio of 90% was obtained at about 68%. At relative density of 55%, nitridation ratio with the nitrogen pressure has a miximum (87.3%) at 7 atm. As the amounts of additive titanium hydride increased, nitridation ratio decreased at below 7 atm nitrogen pressure and, increased at above this pressure until percent of addition percent reached 15 wt% and decreased abruptly upon futher increases in titanium hydride. In the synthesis of TiCxNy by combustion reaction, heat transfer from combustion zone to preheating zone and nitrogen gas penetration into the compact were found to be important factors affecting the TiCxNy formation. It was difficult to obtain high nitridation ratio when the conbustion temperature was either too high or too low, and it seems that the retention of high temperature after a combustion wave sweeped through the reactant mixture pellet is critical to obtain a satisfactory nitridation ratio.

침강성탄산칼슘의 제조에 관한 연구 (Ⅰ) : 비정질탄산칼슘의 생성과 전이

하호,박승수,이희철 ( Ho Ha,Seung Soo Park,Hee Cheol Lee ) 한국공업화학회 1992 공업화학 Vol.3 No.3

반응온도 10℃하에서 수산화칼슘 수용액에 CO_2 가스를 흡수시켜 탄산화반응을 행하였으며 비정질탄산칼슘의 생성과 전이과정을 조사하였다. 생성된 비정질탄산칼슘은 입경 약 0.02∼0.05㎛ 정도인 구형의 초미립자로서 소량의 부착수를 포함하고, HCO^-_3 이온이 일부 치환된 비화학양론적인 물질이었다. 이 물질은 매우 불안정하여 반응액 내에서 쉽게 안정한 calcite로 전이하게 되는데 반응액 내의 탄산기가 CO_3^(2-) 이온 지배적인 경우에는 연쇄상 calcite로 전이하였고, HCO_3^-이온 지배적인 경우에는 능면체 calcite로 전이하였다. 그러므로 비정질탄산칼슘의 전이과정을 적절히 제어함으로써 탄산칼슘 입자의 형태와 크기를 조절하는 것이 가능할 것으로 생각된다. Carbonation process of an aqueous solution of Ca(OH)_2 with CO_2 gas at 10℃ has been studied to investigate the formation and transformation processes of amorphous calcium carbonate. It was suggested that the amorphous calcium carbonate consisting of spherical particles with the diameter in the range of 0.02∼0.05㎛ be a non-stoichiometric CaCO_3 phase containing small amounts of H_2O and small incorporations of HCO_3^-. Amorphous CaCO_3 is unstable in the aqueous solution and converts to calcite, and its morphology depends on the carbonate species present in the slurry such that with (CO_3^(2-)) prevailing, chain-like calcite composed of ultrafine colloidal particles and with [HCO_3^-] prevailing, rhombohedral particles of calcite are formed respectively. Therefore, morphological control of calcium carbonate crystals could be expected by the adequate controls of transformation process of the amorphous calcium carbonate.

자체반응열 고온합성법에 의한 질화티타늄 합성에 관한 연구

하호,김광래,이희철,Ha, Ho,Kim, Kwang-Rae,Lee, Hee-Cheol 한국세라믹학회 1993 한국세라믹학회지 Vol.30 No.12

Titanium nitride was synthesized by reacting Ti powder with nitrogen gas using SHS method. In this process, the effects of nitrogen pressure, dilution with TiN, or additiion of titanium hydride(TiH1.924) on the conversion of Ti to TiN were investigated. In particular, much effects were given to solve the problem of the conversion drop due to partial melting and subsequent sintering of Ti parciels, by controlling combustion temperature and combustion wave velocity via mixing Ti powder with TiN or/and TiH1.924. For the diluted titanium powders with TiN, the conversion close to 100% was resulted when the nitrogen pressure was over 8atm and with diluent content of 60wt%, and the self-propagating reaction was not sustained when the diluent content was higher than 60wt%. For samples mixed to be 55wt% in Ti component in the mixture of Ti, TiH1.924, and 45% TiN, the conversion was closed to 100% when the amount of titanium hydride added was over 7wt% and the nitrogen pressure was higher than 5atm. The combustion reaction, however, was not sustained when titanium hydride added was more than 10wt%.

자체반응열 고온합성법에 의한 Ti - Al 금속간화합물의 연소특성에 관한 연구

하호,한희동,이희철 ( Ho Ha,Hee Dong Han,Hee Cheol Lee ) 한국공업화학회 1995 공업화학 Vol.6 No.3

자체의 반응열에 의해 반응이 자발적으로 진행되는 SHS법을 이용하여 Ti-Al계 금속간화합물의 반응 특성을 알아 보았다. 이 반응은 티타늄보다 알루미늄의 물리·화학적 특성에 크게 영향을 받았다. Ti-Al계의 반응에서는 승온속도가 낮은 경우(5℃/min)에는 알루미늄의 중력편석 현상으로 인해 3반응(TiAl, TiAl₃, Ti₃Al 합성반응) 모두 여러 상이 생성된 반면, 승온속도가 높은 경우(50℃/min)에는 거의 단일 상으로 생성되었다. 또한, 알루미늄의 양이 적은 반응(Ti₃Al 합성반응)에서는 생성물의 상대밀도가 높았고, 알루미늄의 양이 많은 반응(TiAl₃합성반응)에서는 승온속도의 증가에 따라 생성물의 상대밀도가 증가하였다. Ti₃Al 의 합성반응에서는 압분체의 상대밀도가 증가함에 따라 그리고 압분체를 보온처리한 경우가 Ti₃Al 의 생성량이 많았다. The reaction characteristics of Ti-Al intermetallic compounds were studied, using SHS method which sustains the reaction spontaneously, utilizing the heat generated by the exothermic reaction itself. This reaction was greater affected by the chemical and physical properties of Al than those of Ti. When the TiAl, TiAl₃and Ti₃Al synthetic reactions were carried out under the condition of lover heating rate(5℃/min), the reaction products were multi-phase because of the gravity segregation phenomenon, but reaction products under the condition of higher heating rate(50 ℃/min) were single phase. Also, the product density was high in the Ti₃Al reaction contained the small amount of Al. Higher heating rates resulted in a product of higher density fof the TiAl₃ reaction contained a large amount of Al. In the synthetic reaction of Ti₃Al, the Ti₃Al product increased with increasing relative green density, and was rich in the case of enveloping the compact with a insulator.

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