Bennett Models Research Articles

Thermal Stability of Fe82Nb2B14REM2 Amorphous Alloys

We analyze the thermal stability and kinetic parameters of crystallization of Fe82Nb2B14REM2 (REM = Y, Gd, Tb, or Dy) amorphous metallic alloys by the method of differential scanning calorimetry. It is shown that the alloys based on iron crystallize in two stages. We compute the activation energy of both stages of crystallization of amorphous alloys according to the Kissinger, Ozawa, and Augis–Bennett models. The procedure of doping of the Fe84Nb2B14 alloy with rare-earth metals leads to an increase in temperature, in the activation energy of crystallization, and in the frequency factor. The decrease in the crystallization rate constant of alloys caused by doping with rare-earth metals reveals their resistance to temperature treatment.

Calculations of Avrami exponent and applicability of Johnson–Mehl–Avrami model on crystallization in Er:LiY(PO3)4 phosphate glass

Preparation and thermal properties of Er3+-doped lithium–yttrium meta-phosphate glasses with a nominal composition of Er:LiY(PO3)4 were studied as a new scintillating material for neutron detection. The glassy Er:LiY(PO3)4 ingots 10 × 10 × 25 mm3 in size were prepared by quenching of the molten mixture of the starting lithium carbonate, yttrium phosphate, and phosphorus oxide in stoichiometric relations. Crystallization kinetics was experimentally studied on powder samples with particle sizes ranging from 96 to 106 μm, 200 to 212 μm, and on bulk glassy samples using the non-isothermal differential scanning calorimetry. The evaluation of the measured data was performed using the Johnson–Mehl–Avrami, Matusita and Augis–Bennett models, and the y(α) and z(α) functions. In the case of the powder samples, the model analysis of the measured data showed that the crystallization mechanism was primarily performed through volume nucleation followed by 2D and 3D growth and in the bulk one by the surface and volume nucleation with 1D growth. Obtained kinetic parameters were used for reconstruction of the crystallization peaks using various models and compared with actual experimental data.

Cold crystallization from chiral smectic phase

ABSTRACTCold crystallization of liquid crystalline (S)-4’-(1-methylheptyloxycarbonyl) biphenyl-4-yl 4-[7-(2,2,3,3,4,4,4-heptafluorobutoxy) heptyl-1-oxy]-2-fluorobenzoate (3F7HPhF) was studied in isothermal as well as non-isothermal conditions. For isothermal conditions at temperatures between 233 and 250 K X-ray diffraction and differential scanning calorimetry were used. The crystallization kinetics was described by the Avrami–Avramov model, and the values of Avrami exponent, characteristic time and activation energy were determined. The kinetics of the cold crystallization in non-isothermal conditions for chosen heating rates up to 0.5 K/s was studied by differential scanning calorimetry and analyzed using Ozawa, Mo and Augis–Bennett models. Cold crystallization was found to be three-dimensional and controlled by diffusion both in the isothermal and non-isothermal process, however the activation energy determined in the non-isothermal process is about two times smaller than in the isothermal one.

Comparison of effects of serine racemase knockout on nociceptive behavior among different models of neuropathic and inflammatory pain

Peripheral nerve injury and tissue inflammation often induce abnormal pain. The activation of N‐methyl‐D‐aspartate (NMDA) receptors mediates the development and maintenance of such abnormal pain. D‐serine co‐localizes with NMDA receptors and acts as an endogenous co‐agonist of the NMDA receptor at the glycine binding site. D‐serine is synthesized from L‐serine by serine racemase (SR), which is an enzyme that is abundant in the central nervous system. It remains unclear how alterations in SR activity are involved in modulation of neuropathic and inflammatory pain behavior. In the present investigation, we compared pain behaviors in SR knockout (KO) mice and wild‐type (WT) mice after subjection to a chronic constriction injury (CCI model of Bennett), partial sciatic nerve ligation (PSL model of Seltzer), spinal nerve ligation (SNL model of Chung), and an inflammatory pain model that was induced by subcutaneous formalin.Seven‐ to nine‐week‐old male WT and SR‐KO mice were used for the experiments. Under halothane anesthesia, the mice were subjected to neuropathic surgery. Three types of nerve ligation were performed, as previously described by Bennett et al. (1988), Kim and Chung (1992), and Seltzer et al. (1990). The left sciatic nerve was tied loosely with four ligatures of chromic gut at the mid‐thigh level (Bennett model), the left L5 and L6 spinal nerves were isolated and ligated tightly with a 4‐0 silk thread (Chung model), and the dorsal one‐third to one‐half of the left sciatic nerve was tightly ligated (Seltzer model). Mechanical allodynia was assessed by measuring the frequency of withdrawal responses using von Frey filaments both before and after ligation. To induce inflammatory pain, paraformaldehyde (50 μL, 25% in distilled water) was injected subcutaneously in the dorsal surface of the left hind paw. The mice were continuously observed for 60 min after the formalin injection, and the number of flinches of the injected paw was measured during the observation period.Behavioral observations showed the following results: 1) The second phase of the formalin‐induced licking response was augmented in SR‐KO mice, while the first phase was not; 2) mechanical allodynia in the Seltzer model was quite similar between SR‐KO mice and WT mice; 3) mechanical allodynia in both the Chung and Bennett models was significantly augmented in SR‐KO mice compared with WT mice.The mechanisms of the presently observed different effects of SR knockout on different pain models are unclear. We are currently investigating how differently synaptic circuit activity in the spinal dorsal horn is affected by SR knockout in different pain models.Support or Funding InformationDokkyo Med Univ Mutual FundThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Thermal degradation behaviour of nanoamphiphilic chitosan dispersed poly (lactic acid) bionanocomposite films

In the present study, nano-amphiphilic chitosan termed as chitosan-grafted-oligo l-lactic acid (CH-g-OLLA), is synthesized by microwave initiated insitu condensation polymerization. The synthesized CH-g-OLLA becomes hydrophobic in nature due to chemical bond formation between chitosan backbone and OLLA chains. Further, CH-g-OLLA (30%) bionanocomposite is used as a nanofiller in poly (lactic acid)/chitosan-grafted-oligo l-lactic acid (PLA/CH-g-OLLA) bionanocomposite films. Surface morphology shows a homogeneous dispersion of CH-g-OLLA in the form of spherical aggregates, which vary in the range of ∼20 to 150nm. Non-isothermal degradation kinetics, proposed by Kissinger, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Augis & Bennett models, are utilized to estimate the activation energies (Ea) for PLA, which are 254.1, 260.2, 257.0 and 259.1kJmol−1 respectively. The reduction in Ea values of bionanocomposite films may be elucidated by intermolecular distance and enrichment in chain mobility. The evolved gaseous products like hydrocarbons, carbon dioxide, carbon monoxide and cyclic oligomers are successfully identified with TG-FTIR analysis.

Non-isothermal crystallization kinetics of K2O modified sodium-phosphate glasses

Glasses of composition 55P2O5–(45-x)Na2O–xK2O; (5≤x≤25) have been prepared by melt-quench technique. The broad halo in all quenched samples indicates their amorphous nature as confirmed by X-ray powder diffraction. The mixed glass modifiers effect (MGME) on crystallization and thermal stability are investigated using the differential thermal analyzer under non-isothermal conditions. The kinetic of crystallization has been studied using Kissinger's and Augis–Bennett models. The activation energies for glass transition (Eg) and crystallization (Ec) are observed maximum for 10 and 20mol% K2O glasses. 10 and 20mol% K2O contained glasses exhibit minimum crystallization frequency than other glasses, which indicate their higher kinetic and thermodynamic stability. FTIR and Raman analysis confirmed the higher polymerization of phosphate groups in 10 and 20mol% K2O glasses as compared to other glasses.

Effects of lanthanum oxide on the properties of barium-free alkaline-earth borosilicate sealant glass

We have explored the effects of lanthanum oxide (La2O3) on the properties of barium-free SrO–CaO–ZnO–B2O3–SiO2 glass system varying its content from 0 to 6mol%. The coefficient of thermal expansion and glass transition temperature of the glasses are found to be in the ranges 10.6–10.8×10−6/K (50–600°C) and 650–690°C respectively. Differential scanning calorimetric studies revealed an increase in crystallization peak temperature and thermal stability of the glasses up to 4mol% and then decrease on further addition. A monotonic increase in characteristic shrinkage temperature of glass powder compact is observed on addition of La2O3 as revealed in the heating stage microscopic study. X-ray diffraction studies revealed reduced crystallization peak intensity in La2O3 added glasses. Fourier transformed infrared spectra disclosed that the addition of La2O3 stabilized the glass structure by reducing the number of non-bridging oxygens. Vickers micro hardness of the glasses varied in the range 2.6–5.6GPa. Scanning electron microscopy revealed the formation of particulate nature of microstructures in parent glass which is not observed in the La2O3 added glasses. Activation energy of crystallization has increased from 331 to 361kJ/mol determined by Kissinger and Augis–Bennett models. Above properties of these glasses clearly advocate their applicability as solid oxide fuel cell sealants.

The crystallisation kinetics, magnetic and magnetocaloric properties of Gd55Co20Fe5Al20 − xSix (x = 0, 5, 10, 15) alloys

The effects of substituting Si for Al on the crystallisation kinetics and magnetic and magnetocaloric properties of Gd55Co20Fe5Al20−xSix (x=0, 5, 10, 15) alloys have been investigated in detail. The broad diffraction peaks in the XRD patterns indicated that all the samples have amorphous structures. The activation energies of the alloys were calculated using the Kissinger, Ozawa and Augis–Bennett models based on differential thermal analysis data. The Avrami exponent n was calculated from the Johnson–Mehl–Avrami equation. The increase in the activation energy as the Si content increased to x=10 indicated that the addition of Si improves the thermal stability and slows the crystallisation kinetics of the samples. The value of the Avrami exponent showed that the nucleation and growth mechanisms of the crystallisation process depend on the Si concentration. The maximum entropy change reached a maximum value of 6.82J/kgK for x=5 and then decreased with further increases of Si. The refrigeration capacities are 558, 665, 700 and 519J/kg for x=0, 5, 10 and 15, respectively. The increased thermal stabilities and large refrigeration capacities make these amorphous alloys attractive candidates for magnetic refrigeration applications.

Effects of filler type on the nonisothermal crystallization kinetics of poly(butylene terephthalate) (PBT) composites

AbstractIn this study, melt‐crystallization behaviors of poly(butylene terephthalate) (PBT) composites including different types of inorganic fillers were investigated. Composite samples having 5 wt % of fillers were prepared by melt processing in a twin screw extruder using commercial grades of calcite (CA), halloysite (HL), and organo‐montmorillonite (OM) as filler. Depending on the filler type and geometry, crystallization kinetics of the samples was studied by differential scanning calorimetry (DSC) methods. Effect of filler type on the nonisothermal melt‐crystallization kinetics of the PBT was analyzed with various kinetic models, namely, the Ozawa, Avrami modified by Jeziorny and Liu‐Mo. Crystallization activation energies of the samples were also determined by the Kissinger, Takhor, and Augis–Bennett models. From the kinetics study, it was found that the melt‐crystallization rates of the samples including CA and HL‐nanotube were higher than PBT at a given cooling rate. On the other hand, it was also found that organo‐montmorillonite reduced the melt‐crystallization rate of PBT. It can be concluded that organic ammonium groups in the OM decelerate the crystallization rate of PBT chains possibly due to affecting the chain diffusion through growing crystal face and folding. This study shows that introducing organically modified alumina‐silicate layers into the PBT‐based composites could significantly reduce the production rate of the injection molded parts during the processing operations. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Glass-crystal transformations in Se 80− xTe 20Ag x ( x = 0, 3, 5, 7 and 9) glasses

Se 80− x Te 20Ag x ( x = 0, 3, 5, 7 and 9) glassy alloys have been prepared by the conventional melt quenching technique. These samples were structurally characterized using X-ray diffraction. Kinetics of phase transformations of Se 80− x Te 20Ag x ( x = 0, 3, 5, 7 and 9) glassy system has been studied by differential scanning calorimetry (DSC) under non-isothermal conditions at five different heating rates. The DSC traces have been analyzed in terms of activation energy and stability by four models viz. Kissinger, Matusita, Gao-Wang and Augis and Bennett models. Avrami exponent ( n), dimensionality of growth ( m) and frequency factor have also been determined for a better understanding of growth mechanism. The obtained kinetic parameters indicate that stability of the glassy samples increase with increasing Ag content.

Nonisothermal crystallization kinetics of poly(ethylene terephthalate)/clay nanocomposites prepared by melt processing

AbstractIn this study, cold and melt crystallization behaviors of amorphous poly(ethylene terephthalate) (PET)/clay nanocomposites were investigated. Two nanocomposite samples with the same amount of inorganic content were prepared by melt processing using natural montmorillonite (Na‐MMT) and organo‐modified montmorillonite (org‐MMT). Depending on the clay structure, clay dispersion into PET and crystallization behavior of the samples were studied using X‐ray diffraction and differential scanning calorimetry methods, respectively. Effects of clay structure and organic groups between clay layers in org‐MMT on the melt crystallization kinetics of the samples were analyzed with various kinetic models, namely, the Ozawa, Avrami modified by Jeziorny, and Liu‐Mo. Crystallization activation energies of the samples were also determined by the Kissinger and Augis–Bennett models. Exfoliated structures were obtained in the nanocomposite samples prepared with both the Na‐MMT and org‐MMT. From the kinetics study, it was found that the melt‐crystallization rate of the sample prepared with the Na‐MMT was higher than that prepared with the org‐MMT at a given cooling rate. It can be concluded that organic ammonium groups in the org‐MMT decelerate the crystallization rate of PET chains possibly by affecting the chain diffusion and folding. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers

Crystallization kinetics of Fe73.5−xMnxCu1Nb3Si13.5B9 (x=0, 1, 3, 5, 7) amorphous alloys

Abstract In this study, we have investigated the effect of substituting Mn for Fe on the crystallization kinetics of amorphous Fe 73.5− x Mn x Cu 1 Nb 3 Si 13.5 B 9 ( x = 1, 3, 5, 7) alloys. The samples were annealed at 550 °C and 600 °C for 1 h under an argon atmosphere. The X-ray diffraction analyses showed only a crystalline peak belonging to the α-Fe(Si) phase, with the grain size ranging from 12.2 nm for x = 0 to 16.7 nm for x = 7. The activation energies of the alloys were calculated using Kissinger, Ozawa and Augis–Bennett models based on differential thermal analysis data. The Avrami exponent n was calculated from the Johnson–Mehl–Avrami equation. The activation energy increased up to x = 3, then decreased with increasing Mn content. The values of the Avrami exponent showed that the crystallization is typical diffusion-controlled three-dimensional growth at a constant nucleation rate.

The effects of KRN5500, a spicamycin derivative, on neuropathic and nociceptive pain models in rats. (Massachusetts General Hospital, Charlestown, MA) Anesth Analg 2000;91:955-959.

This study investigated the effects of a spicamycin derivative, KRN5500, on two models of neuropathic pain (Chung and Bennett models) and a nociceptive pain model by using Complete Freund's adjuvant. After the establishment of mechanical models, a single intraperitoneal injection of KRN5500 produced significant attenuation of mechanical allodynia in both neuropathic pain models. However, this effect was not observed in rats that had a nociceptive injury. Furthermore, this experimental drug did not alter the mechanical pain threshold on normal, uninjured rats. Conclude that the KRN5500 may have value in the treatment of neuropathic pain.

The effects of KRN5500, a spicamycin derivative, on neuropathic and nociceptive pain models in rats.

We studied the effects of a spicamycin derivative, KRN5500, on two animal models of neuropathic pain (Chung and Bennett models) and a nociceptive pain model by using Complete Freund's adjuvant. After the establishment of mechanical allodynia by using the previously mentioned models, a single intraperitoneal injection of KRN5500 produced significant attenuation of mechanical allodynia in both neuropathic pain models. However, this effect was not observed in rats that had a nociceptive injury (Complete Freund's adjuvant). Furthermore, this experimental drug did not alter the mechanical pain threshold (by using von Frey filament test) on normal, uninjured rats. We have demonstrated that KRN5500 may have value in the treatment of neuropathic pain.

Regulation of galanin and neuropeptide Y in dorsal root ganglia and dorsal horn in rat mononeuropathic models: possible relation to tactile hypersensitivity

The expression of galanin and neuropeptide Y in rat lumbar 5 (L5) dorsal root ganglia and dorsal horn (L4–5) was studied after four types of peripheral nerve injury using immunohistochemistry and in situ hybridization. The possible correlation between these two peptides and tactile allodynia-like behaviour was analysed as well. The models employed were the Gazelius (photochemical lesion) and Seltzer and Bennett (constriction lesions) models, as well as complete sciatic nerve transection (axotomy). Two weeks after surgery, the Gazelius model rats more frequently displayed a greater tactile allodynia than the rats from the Seltzer and Bennett models. Tactile allodynia was not observed in any of the axotomized rats. A marked increase in the number of galanin-immunoreactive and galanin messenger RNA-positive neuron profiles was observed in ipsilateral dorsal root ganglia in all types of models. The increase in allodynic rats (Gazelius, Seltzer and Bennett models) was less pronounced than that after axotomy. In addition, in the Bennett model the number of galanin-immunoreactive neurons was significantly lower in allodynic rats as compared to non-allodynic rats, and the same tendency, but less obvious was found in the Seltzer model. Furthermore, an increase in galanin-immunoreactive fibres was found in the superficial laminae of the ipsilateral dorsal horn in all lesion models, especially in lamina II. A dramatic increase in the number of neuropeptide Y and neuropeptide Y messenger RNA-positive neuron profiles was also found in the ipsilateral dorsal root ganglia in all models, but no significant difference was found in peptide levels between allodynic and non-allodynic rats in any of the models. The present results suggest that the levels of endogenous galanin may play a role in whether or not allodynia develops in the Bennett model.