Synthesis of NaY zeolite from a submolten depolymerized perlite:Alkalinity effect and crystallization kinetics

NaY zeolites are synthesized using submolten salt depolymerized natural perlite mineral as the main silica and alumina sources in a 0.94 L stirred crystallizer.Effects of alkalinity ranging from 0.38 to 0.55(n(Na_(2)O)/n(SiO_(2)))on the relative crystallinity,textural properties and crystallization kinetics were investigated.The results show that alkalinity exerts a nonmonotonic influence on the relative crystallinity and textural properties,which exhibit a maximum at the alkalinity of 0.43.The nucleation kinetics are studied by fitting the experimental data of relative crystallinity with the Gualtieri model.It is shown that the nucleation rate constant increases with increasing alkalinity,while the duration period of nucleation decreases with increasing alkalinity.For n(Na_(2)O)/n(SiO_(2))ratios ranging from 0.38 to 0.55,the as-synthesized NaY zeolites exhibit narrower crystal size distributions with the increase in alkalinity.The growth rates determined from the variations of average crystal size with time are 51.09,157.50,46.17 and 24.75 nm·h^(-1),respectively.It is found that the larger average crystal sizes at the alkalinity of 0.38 and 0.43 are attributed to the dominant role of crystal growth over nucleation.Furthermore,the combined action of prominent crystal growth and the longer duration periods of nucleation at the alkalinity of 0.38 and 0.43 results in broader crystal size distributions.The findings demonstrate that control of the properties of NaY zeolite and the crystallization kinetics can be achieved by conducting the crystallization process in an appropriate range of alkalinity of the reaction mixture.

Influence of amorphous degree on crystallization kinetics of Zr_(60)Al_(15)Ni_(25) bulk metallic glass

The microstructure of as-cast Zr60Al15Ni25 bulk metallic glass was investigated by high-resolution transmission electron microscopy. It is found that there exist numerous short-range order regions （SRORs） in the metallic glass though it is identified to be amorphous by X-ray diffraction method. Furthermore, the amorphous degree shows a close correlation with the microstructure of corresponding mother ingot. The crystallization kinetics was investigated by differential scanning calorimetry under isochronal and isothermal conditions. The results show that the crystallization is triggered by the growth of the pre-existing SRORs and the growth is three-dimension diffusion-controlled. The amorphous degree of Zr60Al15Ni25 bulk metallic glass considerably influences its crystallization kinetics, namely, the more homogeneous distribution of atoms results in a more sluggish nucleation behavior.

Crystallization kinetics and corrosion behaviors of Mg_(61)Cu_(28)Gd_(11) and (Mg_(0.61)Cu_(0.28)Gd_(0.11))_(99.5)Sb_(0.5) amorphous alloys

0.5% （molar fraction） Sb was added to Mg61Cu28Gd11 glass forming alloy to improve its thermal stability and corrosion resistance. The crystallization kinetics of Mg61Cu28Gd11 and （Mg0.61Cu0.28Gd0.11）99.5Sb0.5 amorphous alloys was investigated under continuous heating. The temperatures of glass transition, onset and peak crystallization for the two glasses exhibit strong heating-rate dependence. The activation energies for the onset and peak crystallization were determined based on the Oawza plots. Vogel-Fulcher-Tamman equation analysis shows that the larger strength parameter and much longer relaxation time are obtained due to the Sb addition. The corrosion properties of the two glassy alloys were studied by means of potentiodynamic and immersion tests. Compared with the parent alloy, （Mg0.61Cu0.28Gd0.11）99.5Sb0.5 glassy alloy exhibits a superior corrosion resistance in Cl--containing alkaline solution, as indicated by the lower passive current density and corrosion rate. Based on the point defect model, the effect mechanism of Sb addition on corrosion resistance of Mg-Cu-Gd glassy alloy is carefully identified.

Non-isothermal crystallization kinetics of Nylon 10T and Nylon 10T/1010 copolymers:Effect of sebacic acid as a third comonomer

Nylon 10 T and Nylon 10T/1010 samples were synthesized by direct melt polymerization. The non-isothermal crystallization kinetics of Nylon 10 T and Nylon 10T/1010 was investigated by means of differential scanning calorimetry(DSC). Jeziorny equation and Mo equation were applied to describe the non-isothermal crystallization kinetics of the Nylon 10 T and the Nylon 10T/1010. The activation energies for non-isothermal crystallization were obtained by Vyazovkin's method and Friedman's method, respectively. These results showed that Jeziorny equation and Mo equation well described the non-isothermal crystallization kinetics of the Nylon 10 T and the Nylon 10T/1010. It was found that the values of the activation energy for non-isothermal crystallization of the Nylon 10T/1010 were lower than those of the Nylon 10 T at a given temperature or relative crystallinity degree,which revealed that crystallization ability of the Nylon 10T/1010 was higher. The crystal morphology was observed by means of a polarized optical microscope(POM) and X-ray diffraction(XRD). It was found that the addition of sebacic acid comonomer not only did not change the crystal form of the Nylon 10 T, but also significantly increased the number and decreased the size of spherulites. Comparing with the Nylon 10 T, the crystallization rate was increased with the addition of the sebacic acid comonomer.

Isothermal and nonisothermal crystallization kinetics of bio-sourced nylon 69

Bio-sourced nylon 69,one of promising engineering plastics,has a great potential in developing sustainable technology and various commercial applications.Isothermal and nonisothermal crystallization kinetics of nylon 69 is a base to optimize the process conditions and establish the structure–property correlations for nylon 69,and it is also highly bene ficial for successful applications of nylon products in industry.Isothermal and nonisothermal crystallization kinetics has been investigated by differential scanning calorimetry for nylon 69,bio-sourced even–odd nylon.The isothermal crystallization kinetics has been analyzed by the Avrami equation,the calculated Avrami exponent at various crystallization temperatures falls into the range of 2.28 and 2.86.In addition,the Avrami equation modi fied by Jeziorny and the equation suggested by Mo have been adopted to study the nonisothermal crystallization.The activation energies for isothermal and nonisothermal crystallization have also been determined.The study demonstrates that the crystallization model of nylon 69 might be a twodimensional(circular)growth at both isothermal and nonisothermal crystallization conditions.Furthermore,the value of the crystallization rate parameter(K)decreases signi ficantly but the crystallization half-time(t1/2)increases with the increase of the isothermal crystallization temperature.To nonisothermal crystallization,the crystallization rate increases as the cooling rate increases according to the analysis of Jeziorny's theory.The results of Mo's theory suggest that a faster cooling rate is required to reach a higher relative degree of crystallinity in a unit of time,and crystallization rate decreases when the relative degree of crystallinity increases at nonisothermal crystallization conditions.

Non-isothermal Crystallization Kinetics of Polyamide 6/Diaminemodified MWNTs Nanocomposite

The non-isothermal crystallization kinetics of polyamide 6/diamine-modified multi-walled carbon nanotube （PA6/D-MWNT） nanocomposite was investigated by differential scanning calorimetry （DSC）. The modified Avrami equation, the Ozawa equation and the combined Avrami/Ozawa equation were employed to analyze the non-isothermal crystallization data. The crystallization activation energies were also evaluated by the Kissinger method. It was found that the combined Avrami/Ozawa equation could successfully describe the non-isothermal crystallization process. The results showed that D-MWNTs not only acted as effective heterogeneous nucleating agents for PA6 and noticeably increased the crystallization temperature of PA6, but also influenced the mechanism of nucleation and crystal growth of PA6 and then reduced the overall crystallization rate of the neat PA6 matrix. The crystallization activation energy for the nanocomposite sample was greater than that of the neat PA6, which indicated that the addition of D-MWNTs hindered the mobility of PA6 chain segments.

Effect of Y_2O_3 on the crystallization kinetics of TiO_2 nucleated LAS glass for the production of nanocrystalline transparent glass ceramics

Crystallization kinetics of metastable B-quartz solid solution as a desirable phase for the production of trans- parent lithium aluminosilicate （LAS） glass ceramics was investigated in the presence of Y203. Accordingly, differential thermal analysis scans were performed thoroughly to study the mechanism of crystallization kinetics. The aim of this investigation is to discover the complicated mechanism of crystallization process in the presence of co-additives and ac- cordingly find a way for increasing the transparency of glass ceramics. It is shown that the bulk （3D） growth is intensively increased by the enhancement of Y203. Then again, reducing nucleation and increasing growth mechanisms were recog- nized for the LAS system in the presence of Y2O3. Results of the investigation illustrate that when co-additives are added to glasses, it is necessary to nucleate the optical component separately before the growth process.

Crystallization Kinetics of Lithium Aluminum Germanium Phosphate Glass by DSC Technique

Abstract： The crystallization kinetics of Li20-A12O3-GeO2-P205 （LAGP） glass fabricated via the conventional melt-quenching method was studied by differential scanning calorimetry （DSC） under non- isothermal condition at different heating rates. The activation energy of glass transition Eg is 634.4 kJ/mol, indicating that LAGP glass is easy to crystallize at an elevated temperature. The activation energy of crystallization Eo and Avrami index n obtained from Matusita＇s model are 442.01 kJ/mol and 1.7, respectively. The value of n reveals that bulk crystallization predominates slightly over surface crystallization during crystallization process. LAGP glass-ceramics after different heat treatments have the same crystalline phases determined as major phase LiGe2（PO4）3, with A1PO4 and GeO2 as their impurity phases.

Isothermal Crystallization Kinetics of Nylon 10T and Nylon 10T/1010 Copolymers:Effect of Sebacic Acid as a Third Comonomer

Nylon 10T and nylon 10T/1010 samples were synthesized by direct melt polymerization.The isothermal crystallization kinetics of nylon 10T and nylon 10T/1010 was investigated by means of differential scanning calorimetry（DSC）.The crystallization kinetics under isothermal condition has been analyzed by the Avrami equation.It was found that the Avrami equation was well-suited to describe the isothermal crystallization kinetics,combined with the results of the Turnbull-Fisher equation.The values of Tm^0 and Kg were obtained by Hoffman-Weeks and Lauritzen-Hoffman equations,respectively.The activation energies for isothermal crystallization of nylon 10T and nylon 10T/1010 were determined using the Arrhenius equation and found to be-123.24 and-81.86 kJ·mol^（-1）,respectively,which reveals that the crystallization ability of nylon 10T/1010was lower than that of nylon 10T during the isothermal crystallization process.The crystal morphology was observed by means of polarized optical microscopy（POM）and X-ray diffraction（XRD）.It was found that the addition of sebacic acid comonomer did not change the crystal form of nylon 10T,but significantly increased the number and decreased the size of spherulites.

Crystallization Kinetics of Misch Metal Based Bulk Metallic Glasses

The crystallization kinetics of Mm55Al25Cu10Ni5Co5 bulk metallic glass （BMG） was investigated by means of differential scanning calorimetry （DSC） in the mode of continuous heating or isothermal annealing. It was found that the apparent activation energy Eg, Ex and Ep of the BMG calculated by Kissinger＇s method were 189.58, 170.68 and 170.41 kJ·mol^-1, respectively, which was bigger than those of La55Al25Cu10Ni5Co5 BMG indicating that thermal stability of the former was higher than that of the latter. The local activation energy obtained using Ozawa equation decreased as crystallization proceeded except for the initial stage. The Avrami exponents were calculated to be in the range of 3.26 - 5.23 for different crystallization stages and isothermal temperatures. This implied that crystallization of Mm55Al25Cu10Ni5Co2 BMG was governed by diffusion-controlled three-dimensional growth with either reduced or increased nucleation rate, depending on isothermal temperature. Inconsistency of thermal stability with glass-forming ability for Mm（La）-Al-Cu-Ni-Co BMGs was discussed.

Non-isothermal Melt Crystallization Kinetics of Anhydrite-Filled Polypropylene Composites

The non-isothermal crystallization kinetics of polypropylene （PP）, PP/anhydrite composites were investigated by differential scanning calorimetry （DSC） with various cooling rates. The Avrami analysis modified by Jeziorny and a method developed by Mo were employed to describe the non-isothermal crystallization process of these samples. The difference in the exponent n between PP and PP/anhydrite composites indicated that non-isothermal kinetic crystallization corresponded to tri-dimensional growth with heterogeneous nucleation. The values of half-time, Zc and F（T） showed that the crystallization rate increased with the increasing of cooling rates for PP and PP/anhydrite composites, but the crystallization rate of PP/anhydrite composites was faster than that of PP at a given cooling rate. The method developed by Ozawa did not describe the non-isothermal crystallization process of PP very well. Moreover, the method proposed by Kissinger was used to evaluate the activation energy of the mentioned samples. The result showed that the activation energy of PP/anhydrite was greatly larger than that of PP.

Crystallization Kinetics and Magnetic Properties of Fe_(73.5)Si_(13.5)B_9Cu_1Nb_1V_2 Nanocrystalline Powder Cores

Amorphous ribbons of the alloy Fe73.5 Si13.5B9Cu1Nb1V2 were prepared by the standard single copper wheel melt spinning technique in the air atmosphere. The crystallization kinetics of amorphous ribbons was analyzed by non-isothermal differential scanning calorimetry （DSC） measurements. The crystallization activation energies of amorphous ribbons calculated by using Kissinger model were 364 and 337 kJ/mol for the first and the second crystallization, respectively. The Avrami exponent n was calculated from the Johnson- Mehl-Avrami （ MA） equation. The value of the Avrami exponent showed that the crystallization mechanism in the non-isothermal primary crystallization of amorphous ribbons was all shapes growing from small dimensions controlled by diffusion at decreasing nuclectcn rate. The variation of soft magnetic properties of nanocrystalline Fe73.5 Si13.5B9Cu1Nb1V2 alloy powder cores s a tunction of milling times has been investigated. It is found that the effective permeability of the cores shows high frequency stability and decreases with the increase of milling times. The quality factor increases with increasing frequency in lower frequency range, and reaches a maximum at the frequency of 80 kHz then decreases gradually with increasing frequency.

THE CRYSTALLIZATION KINETICS OF AN AMORPHOUS Ti-RICHNiTi FILM

The crystallization kinetics of an amorphous Ti-rich NiTi film (Ni 46.34at.%, Ti 53.66at.%)prepared by DC magnetron sputtering was determined by non-isothermal techniques. The activation energy of crystallization and the mean value of the Avrami parameter are 382kJ/mol and 0.85, respectively. The calculated isothermal kinetic curse of amorphous film at 773K coincides with the result of X-ray diffraction.The formation of a Ti2Ni phase is accompanied with the crystallization of Ti-rich NiTi film.

Nonisothermal Crystallization Kinetics of Poly(butylene adipate-co-terephthalate) Copolyester

Nonisothermal crystallization behavior of poly(butylene adipate-co-terephthalate)(PBAT) synthesized via direct esterification and polycondensation reactions was investigated by the differential scanning calorimetry(DSC).The Avrami equation modified by Jeziorny and the Z.S.Mo equation were employed to describe the non-isothermal crystallization kinetics of copolyester samples.The test results showed that the Avrami equation was successful in describing nonisothermal crystallization process of PBAT copolyesters.PBAT copolyester could give birth to secondary crystallization.The crystallization parameter(Zc) increased with an increasing cooling rate and the Avrami exponent(n) was around 2.3.For a given cooling rate,the value of Zc demonstrated a sagging trend with an increase in adipic acid(AA) content.The equation proposed by Z.S.Mo was successful in describing the nonisothermal crystallization kinetics of PBAT copolyesters.

Crystallization Kinetics of NiTi Films with Different Ni Contents

Three kinds of NiTi films with different Ni contents were prepared by DC magnetron sputtering. The crystallization kinetics of amorphous films was determined by using non-isothermal single- scan techniques. The results show that the activation energy of crystallization of Ni-rich NiTi film(Ni 51.10 at. pct, Ti 48.90 at. pct) is 715 kJ/mol; while that of Ti-rich films are similar: one is 445 kJ/mol (Ni 46.74 at. pct. Ti 53.26 at. pct), the other is 418 kJ/mol (Ni 43.21 at. pct, Ti 56.7g at. pct), which i5 lower than Ni-rich film. The Avrami parameter n of different films are 0.92 and 0.74 for Ni-rich film and Ti-rich films, respectively. The difference of kinetic parameters for NiTi films with various Ni contents implies that the crystallization behaviors of these films are distinct, which is confirmed by the calculated isothermal kinetics at different temperatures. The thorough research on this phenomenon is in progress.

Non-Isothermal Crystallization Kinetics of a Rapidly Solidified as-Cast TiZrHfNiCu High Entropy Bulk Metallic Glass

This paper aims to investigate the thermal behavior and crystallization kinetics of TiZrHfNiCu high entropy bulk metallic glass (HE-BMG) alloy using the standard procedure of Differential Scanning Calorimetric (DSC) annealing technique. The alloy was produced using an arc melting machine with a critical diameter of 1.5 mm. The crystallization kinetics and phase transformation mechanism of TiZrHfNiCu HE-BMG was investigated under the isochronal condition at a single heating run based on the Johnson-Mehl- Avrami (JMA) theory. In isochronal heating, the apparent activation energy for glass transition and crystallization events was analyzed by Kissinger and Ozawa methods. The average activation energy value for crystallization of TiZrHfNiCu amorphous alloys in isochronal modes was 226.41 kJ/mol for the first crystallization and 297.72 kJ/mol for second crystallization stages. The crystallization mechanism of the first step was dominated by two- and three-dimensional growth with increasing nucleation rate, while the crystallization mechanism in the second stage was dominated by two-dimensional crystallization growth with a constant nucleation rate. The diffusion mechanism result proved the theory of sluggish atomic diffusion of HEA at elevated temperature.

Non-isothermal crystallization kinetics of reactive microgel/nylon 6 blends

The non-isothermal crystallization kinetics of reactive microgel/nylon 6 blends was investigated by differential scanning calorimetry(DSC). The Mo equation was employed to analyze the non-isothermal crystallization data. The crystallization activation energies were also evaluated by the Kissinger method. The results show that the crystallization onset temperature(T onset) and crystallization peak temperature(T p) decrease with the increase of the content of reactive microgel, while ΔT(T onset–T p), the crystallization half-time(t1/2) and the crystallization enthalpy(ΔH c) increase. The required cooling rates of blends are higher than that of neat nylon6 in order to achieve the same relative crystallinity in a unit of time. The crystallization activation energies of the reactive microgel/nylon 6 blends are greater than those of the neat nylon 6. When the content of reactive microgel is 30%, the relative crystallinity(X t) reaches the maximum.

The Effect of Additives on Calcium Sulfate Dihydrate Crystallization Kinetics in Gypsum Type Brine System

1 Introduction There exist calcium and sulfate ions outside sodium chloride in solution mining for calcium sulfate brine.The calcium and sulfate ions not only affect the purity of the vacuum salt products,but also increase the scaling of vacuum evaporation tanks and brine reusing pipes.Additives have certain impacts on the crystallization dynamics(Randolph et al.,1971).The crystallization

CRYSTALLIZATION KINETICS OF HOMOGENEOUS AND HETEROGENEOUS LLDPE

Based on thermal analysis, the isothermal and nonisothemal crystallization kinetics of Ziegler-Natta catalyzed linear low density polyethylene (Z-N LLDPE) and metallocene catalyzed LLDPE (m-LLDPE) were studied. Treating the results with the Avrami equation and the Ozawa equation, the crystallization constant Igk and the Avrami exponent n were obtained. Some other crystallization parameters were also discussed. According to the different characteristics of the chain structures of Z-N LLDPE and metallocene LLDPE, their crystallization behaviors were analyzed. It is indicated that the homogeneity and heterogeneity of the two polymers act in different way during the crystallization process of polymers, including the nucleation and the growth of crystals under various conditions.

Crystallization kinetics of (Ni_(0.75)Fe_(0.25)_(78-x)Nb_xSi_(10)B_(12)(x=0,5)amorphous alloys

Amorphous ribbons of （Ni0.75Fe0.25）78-xNbxSi10B12 （x = 0, 5） were prepared by a single roller melt-spinning technique in air atmosphere. The crystallization kinetics of the alloys were investigated by means of continuous heating, and the activation energies of the alloys were calculated using Kissinger plot method and Ozawa plot method on the basis of differential thermal analysis data. The crystallization products were analyzed by X-ray diffraction. After the （Ni0.75Fe0.25）78Si10B12 amorphous alloy was annealed at the temperatures 715 and 745 K, a single phase of γ-（Fe, Ni） solid solution with grain sizes of about 10.3 and 18.5 nm, respectively, precipitates in the amorphous matrix. The crystallized phases are γ-（Fe, Ni） solid solution, Fe2Si, Ni2Si, and Fe3B after annealing at 765 K. The （Ni0.75Fe0.25）73NbsSi10 B12 amorphous alloy was annealed at 720, 750, and 800 K; and the crystallization phases, γ（Fe, Ni） solid solution, （Fe, Ni）23B6. Ni31Si12 and Nb2NiB0.16 form simultaneously.