• Title/Summary/Keyword: 수화반응

Search Result 585, Processing Time 0.028 seconds

Pressure Effect on the Aquation of $trans-[Cr(tmd)_2F_2]^+\;and\;trans-[Cr(tmd)_2FCl]^+$ Ions ($trans-[Cr(tmd)_2F_2]^+$$trans-[Cr(tmd)_2FCl]^+$ 착이온의 수화반응에 미치는 압력의 영향)

  • Jong-Jae Chung;Han-Tae Kim;Sung-Oh Bek
    • Journal of the Korean Chemical Society
    • /
    • v.33 no.2
    • /
    • pp.164-167
    • /
    • 1989
  • The rate for the aquation of $trans-[Cr(tmd)_2FX]^+(X=F^-,\;Cl^-)$ ion in aqueous acidic solution has been measured by spectrophotometric method at various temperatures and pressures. The rate constants are increased with increasing temperatures and pressures. The values of activation entropy are 5.2 eu for $trans-[Cr(tmd)_2F_2]^+$ and -16.62 eu for $trans-[Cr(tmd)_2FCl]^+$ ions. Activation volumes have all negative values and lie in the limited range $-3∼-2\;cm^3mol^{-1}$ for $trans-[Cr(tmd)_2F_2]^+$ and $-8∼-7\;cm^3mol^{-1} for $trans-[Cr(tmd)_2FCl]^+$ ion. From the above results, we may deduce that the mechanism for the aquation of $trans-[Cr(tmd)_2F_2]^+$ and $trans-[Cr(tmd)_2FCl]^+$ ions is interchange-associative mechanism and dissociative mechanism respectively.

  • PDF

Influence of Thallium Carbonate on the Hydration of Tricalcium Silicate (Tricalcium silicate의 수화반응에 따른 $T1_2CO_3$의 영향)

  • Yim, Going
    • The Journal of Natural Sciences
    • /
    • v.4
    • /
    • pp.95-102
    • /
    • 1991
  • The influences of various concentrations of thallium carbonate on the hydration of tricalcium silicate which is widely used to the inorganic materials have been studied using an isothermal microcalorime-ter. The experimental results indicate that the hydration of tricalcium silicate is accelerated in the presence of thallium carbonate, namely the concentration of thallium carbonate is increased, the rate of hydration is also increased. The x-ray diffraction analysis shows that the concentration of tricalcium silicate decreases rapidly in the presence of thallium carbonate. Differential thermal analysis of tricalcium silicate hydrated in the persence of thallium carbonate indicates the presence of calcium carbonate. The nonevaporable water content and the degree of hydration of tricalcium silicate show that the accelerating action of thallium carbonate is more pronounced only during the early period of hydration. Analytical results of the liquid phase in contact with the tricalcium silicate paste indicate that the concentrations of calcium and hydroxyl ions are changed considerably in the presence of thallium carbonate.

  • PDF

A Study on Expedite Heat Transfer in Packed Bed of Hydration Calcined Dolomite for Chemical Heat Pump (소성 Dolomite 수화물 화학열펌프의 고체반응층 전열촉진 연구)

  • Kim, Jong-Shik;Lee, Han-Gyu;Park, Young-Hae
    • Applied Chemistry for Engineering
    • /
    • v.16 no.3
    • /
    • pp.434-439
    • /
    • 2005
  • The reaction of hydration proceeded at the same time the vapor was introduced into the reactor that was filled with calcined dolomite. It has shown that the temperature has begun to fall from the bottom of reactor after increase of temperature by the heat of hydration reaction. The reaction initiated at the pipe wall and the heat was transfer to the center of block between the fins. The results show that the use of copper fin in the reactor reducted the hydration reaction time by half when compared to the case without using the fins.

Properties of Reaction Rim on Blast Furnace Slag Grain with Alkali Activator according to Hydration Reaction (알칼리 자극제(刺戟劑)에 의해 고로(讀爐) 수쇄(水碎) 슬래그의 주위(周圍)에 형성(形成)된 Reaction Rim의 특성(特性))

  • Lee, Seung-Heun;Mun, Young-Bum
    • Resources Recycling
    • /
    • v.18 no.3
    • /
    • pp.42-48
    • /
    • 2009
  • Since there are $OH^-,\;[SiO_4]^{4-}$ ion of high concentration at early hydration in the system added with activator (NaOH+$Na_2OSiO_2$) in the blast furnace slag, different from cement hydration, hydration progresses fast without induction period and forms reaction rim around the blast furnace slag grain. $0.6{\mu}m$ reaction rim was formed around the blast furnace slag grain from the 1 day of reaction period, and the thickness of reaction rim increases over the reaction time, growing to $1{\mu}m$ on the 28 days. Unreacted blast furnace slag grain deformed from angular shape to the spherical shape. Mole ratio of Ca/Si tends to decrease from inside of blast furnace slag grain to reaction rim. Difference of Ca/Si mole ratio between reaction rim and inside the blast furnace slag grain decreased and generated hydrate was a poor crystalline CSH(I) with Ca/Si mole ratio less than 1.5.

A Study on the Hydration Reaction Model of Expansive Additive of Ettringite-Gypsum Type (에트링가이트-석탄 복합계 팽장재의 수화반응 모델에 관한 연구)

  • Park Sun Gyu;Takahumi Noguchi;Kim Moo-Han
    • Journal of the Korea Concrete Institute
    • /
    • v.17 no.4 s.88
    • /
    • pp.581-586
    • /
    • 2005
  • High-performance concrete (HPC), which is particularly sensitive to self-desiccation, is required to be durable even in severe environmental conditions, i.e. costal area, cold district, etc. However, in recent years, some attention was particularly given to cracking sensitivity of high performance concrete at early age. It has been argued and demonstrated experimentally that such concrete undergoes autogenous shrinkage due to self-desiccation at early age under restrained condition, nd, as a result, internal tensile stress may develop, leading to micro cracking and macro cracking. This shrinkage-introduced crack produces a major serviceability problem for concrete structures. One possible method to reduce cracking due to autogenous shrinkage is the addition of expansive additive. Tests conducted by many researches have shown the beneficial effects of addition of expansive additive for reducing the risk of autogenous shrinkage-introduced cracking. However, the research on hydration model of expansion additive has been hardly researched up to now. This paper presents a study of the hydration model of Ettringite-Gypsum type expansive additive. As a result of comparing forecast values with experiment value, proposed model is shown to expressible of hydration of expansive additive.

Mathematical Modeling of Degree of Hydration and Adiabatic Temperature Rise (콘크리트의 수화도 및 단열온도상승량 예측모델 개발)

  • 차수원
    • Journal of the Korea Concrete Institute
    • /
    • v.14 no.1
    • /
    • pp.118-125
    • /
    • 2002
  • Hydration is the main reason for the growth of the material properties. An exact parameter to control the chemical and physical process is not the time, but the degree of hydration. Therefore, it is reasonable that development of all material properties and the formation of microstructure should be formulated in terms of degree of hydration. Mathematical formulation of degree of hydration is based on combination of reaction rate functions. The effect of moisture conditions as well as temperature on the rate of reaction is considered in the degree of hydration model. This effect is subdivided into two contributions: water shortage and water distribution. The former is associated with the effect of W/C ratio on the progress of hydration. The water needed for progress of hydration do not exist and there is not enough space for the reaction products to form. The tatter is associated with the effect of free capillary water distribution in the pore system. Physically absorption layer does not contribute to progress of hydration and only free water is available for further hydration. In this study, the effects of chemical composition of cement, W/C ratio, temperature, and moisture conditions on the degree of hydration are considered. Parameters that can be used to indicate or approximate the real degree of hydration are liberated heat of hydration, amount of chemically bound water, and chemical shrinkage, etc. Thus, the degree of heat liberation and adiabatic temperature rise could be determined by prediction of degree of hydration.

A Hydration Reaction and Strength Development Properties of Cement Using Pond Ash in Coal Fired Power Plant (화력 발전소 매립회를 치환한 시멘트의 수화반응 및 강도발현 특성)

  • Lee, Jae-Seung;Noh, Sang-Kyun;Shin, Hong-Chul
    • Journal of the Korean Recycled Construction Resources Institute
    • /
    • v.9 no.4
    • /
    • pp.578-584
    • /
    • 2021
  • This study comparatively analyzed the properties of hydration reaction and strength development of four types of pond ash(PA) and fly ash(FA), aiming for the effective use of PA. The PA whose chlorine content was highest due to the seawater movement method had a faster setting time, higher cumulative heat, and greater initial strength development than those of FA due to the acceleration of the cement hydration reaction. However, the activity factor increase rate decreased after seven days of curing due to the rapid generation of early hydrates. The PA that contained impurities, such as a large amount of unburned carbon, had a delayed setting time due to the lower hydration reaction. Moreover, the strength was degraded in all curing ages. The PA whose chlorine content was lower due to the freshwater movement method and the amorphous content exhibited similar hydration reactivity and strength development characteristics compared to that of FA. The thermogravimetric analysis results verified that it had a similar level of Ca(OH)2 consumption and pozzolanic reactivity with that of FA. Conclusively, it is necessary to expand the application of the freshwater movement method and manage the ignition loss to raise PA's usability.

Micellar Effect of the Aquation and the Base Hydrolysis of cis-[Co(en)2NH3Cl]2+ Ion (cis-[Co(en)2NH3Cl]2+ 이온의 수화반응과 염기성 가수분해반응에 미치는 미셀의 효과)

  • Jeong, Jong Jae;Baek, Seong O;Lee, Jeong A
    • Journal of the Korean Chemical Society
    • /
    • v.38 no.4
    • /
    • pp.265-270
    • /
    • 1994
  • The aquation and base hydrolysis of [Co(en)$_2$NH$_3$Cl]$^{2+}$ were studied by UV spectroscopic method in various SDS aqueous solution. The base hydrolysis of [Co(en)$_2$NH$_3$Cl]$^{2+}$ with the addition of 0, 0.05, 0.1 mol dm$^{-3}$ sodium chloride was studied. For the aquation of the complex, the rate constant in the micellar phase(kH$^M$) was a little larger than that in the aqueous phase(kH$^W$). With the increase of SDS concentration, the second order rate constant(kOH) for the base hydrolysis unchanged below the CMC and sharply decreased down to a limiting value after the CMC was reached. The effect of added NaCl on the rate behavior of the complexes in the micellar solution were investigated by using an ion-exchanged model.

  • PDF