Increase In Heat Of Fusion Research Articles

Analysis of the Solidification Process of Metal Alloys Under Microgravity Conditions

The solidification of metal alloys under low gravity conditions mainly deviates in four physical properties compared with samples solidified on earth. The coarseness of the structure and the solidification temperature increase. The latent heat and the solubility of alloying elements in solids are changed. Experimental results are presented and analyzed in order to find a unified theoretical understanding. The differences in the measured quantities between experiments performed in space and on earth were calculated and are presented in this article. Kinetic, thermodynamic, and thermophysical relations were used to analyze those values. The change in the melting point was found to be a result of an increase in the vibrational amplitude of the atoms in the solid. The increase in the latent heat results from an increase in the vibration of atoms in the liquid. The changes in the solubility are a result of an increase in heat of fusion of the alloying element. Furthermore, the increase in the coarseness of the structure is explained as an increase in the atom’s vibration. The analysis highlights that the atom’s vibration increases with decreasing gravity; especially, the amplitude will increase. The explanation for this is given by a decrease in the binding energy between the atoms with decreasing gravity. The decrease in binding energy for liquids is larger than for solids.

Supercritical synthesis and studies on non-isothermal kinetics and thermodynamics of solid state decomposition of nanoferrogels

Poly-N-isopropyl acrylamide (PNIPAM) and related nanoferrogels (NFG) were synthesized in supercritical carbon dioxide and investigated for their non-isothermal kinetic and thermodynamics of solidstate decomposition in oxidative media. Ferrite nanoparticles (FNPs, 10.5 nm) were prepared for NFG through chemical method. Thermal stability, along with kinetic and thermodynamic evaluationsof NFG has been shownthrough simultaneous thermogravimetric (TG) - differential thermal analysis (DTA) - differential thermogravimetry (DTG) in air.Thermal, non-isothermal kinetic and thermodynamic data of NFG was compared with FNP and PNIPAM. NFG have shown two step decompositions with reduction in their TG onset by 10 °C over FNPs and PNIPAM. This was associated with simultaneous increase in heat of fusion (mJ/mg) of NFG (2.88) over PNIPAM (2.55). Horowitz- Metzger (HM) and Coats-Redfern (CR) at reaction orders (n) ranging 0 to 3 reveals consistency in order of solid-state decomposition for FNPs (n = 1), PNIPAM and NFG (n = 3) with negative values of changes in entropy and enthalpy. HM methods reveals greater values of energy of activation (Ea) with respect to CR methods. Applied methods provide large differences in the values of Ea of solidstate degradations with marginal changes in thermodynamic parameters of NFG over PNIPAM. Kinetic and thermodynamic calculations reveal enhanced thermal stability of NFG over PNIPAM followed by FNPs. High thermal stability of NFG makes them possible for agricultural and biomedical applications.

Isothermal step thickening in a long-spaced aliphatic polyester

Discontinuous lamellar thickening has been found at the isothermal crystallization temperatures of a long-spaced aliphatic polyester (PE-48,48) synthesized via polycondensation of the diol and diacid. The isothermal step thickening is characterized by a discrete increase in melting temperature with increasing crystallization time and an increase in heat of fusion of the high melting peak at the expense of the low melting peak. The increase in crystal thickness, quantified by SAXS, is consistent with a straightening of the chains at the basal surfaces of the lamellae to complete a full repeat of the crystalline layer. The increase in thickness and decrease in surface energy are associated with the sudden increase in crystal melting. The isothermal thickening follows a logarithmic dependence of time with a rate that increases with temperature. The thickening process is thermally activated and follows Arrhenius behavior with an activation energy of 238 ± 4 kJ/mol.

Low Dosage Gamma Irradiation of Poly(glycerol sebacate)-co-lactic Acid Utilizing Methyl Methacrylate Crosslinker

The use of low dosage gamma radiation and crosslinker was explored to reduce time and energy requirements for the crosslinking of the biomedical polymer poly(glycerol sebacate)-co-lactic acid (PGS-co-LA) and to determine the effect of these parameters on the polymer’s properties. Curing time was effectively reduced to less than 2 hours from the typical 48 hours required by thermal curing. Analysis using infrared spectroscopy identifies the bonds forming PGS-co-LA and confirms the formation in all low radiation dosage settings and crosslinker amounts. Increasing the amount of crosslinker did not change the polymer’s thermal properties significantly whereas increasing the radiation dosage from 5 kGy to 10 kGy resulted to more negative value of melting temperature and increase in heat of fusion. The sample with the highest amount of crosslinker irradiated at the lowest level of radiation dosage has the least negative melting temperature and lowest heat of fusion

Effect of Biofield Treatment on Physical, Thermal, and Spectral Properties of SFRE 199-1 Mammalian Cell Culture Medium

SFRE 199-1 medium (SFRE-M) is important mammalian cell culture medium, used for the culture of primary cells of mammals such as baboon kidney cells. The present study was attempted to evaluate the impact of biofield energy treatment on the physical, thermal and spectral properties of SFRE-M. The study was accomplished in two groups; one was set as control while another was subjected to Mr. Trivedi’s biofield energy treatment and coded as treated group. Subsequently, the control and treated samples were analyzed using various analytical techniques. The CHNO analysis showed about 2.16, 4.87, and 5.89% decrease in percent contents of carbon, hydrogen, and oxygen, respectively; while 9.49% increase in nitrogen contents of treated sample as compared to the control. X-ray diffraction (XRD) analysis showed 7.23% decrease in crystallite size of treated sample as compared to the control. The thermogravimetric analysis (TGA) analysis showed the increase in onset temperature of thermal degradation by 19.61% in treated sample with respect to the control. The control sample showed the 48.63% weight loss during the thermal degradation temperature (Tmax) while the treated sample showed only 13.62% weight loss during the Tmax. The differential scanning calorimetry (DSC) analysis showed the 62.58% increase in the latent heat of fusion of treated sample with respect to the control sample. The Fourier transform infrared spectroscopy (FT-IR) spectrum of treated SFRE-M showed the alteration in the wavenumber of C-O, C-N and C-H vibrations in the treated sample as compared to the control. Altogether, the XRD, TGA-DTG, DSC, and FT-IR analysis suggest that Mr. Trivedi’s biofield energy treatment has the impact on physical, thermal and spectral properties of SFRE-M. The treated SFRE-M was more thermal stable than the control SFRE-M and can be used as the better culture media for mammalian cell culture.

Potential Impact of Biofield Energy Treatment on the Atomic, Physical and Thermal Properties Indium Powder

Indium has gained significant attention in the semiconductor industries due to its unique thermal and optical properties. The objective of this research was to investigate the influence of the biofield energy treatment on the atomic, physical and thermal properties of the indium. The study was performed in two groups (control and treated). The control group remained as untreated, and treated group received Mr. Trivedi’s biofield energy treatment. Subsequently, the control and treated indium samples were characterized by the X-ray diffraction (XRD), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), and Fourier transform infrared (FT-IR) spectroscopy. The XRD diffractogram showed the shifting of peaks toward higher Bragg’s angles in the treated indium sample as compared to the control. The crystallite size of treated indium sample were substantially changed from -80% to 150.2% after biofield energy treatment, as compared to control. In addition, the biofield energy treatment has altered the lattice parameter (-0.56%), unit cell volume (-0.23%), density (0.23%), atomic weight (-0.23), and nuclear charge per unit volume (1.69%) of the treated indium sample with respect to the control. The DSC showed an increase in the latent heat of fusion up to 3.23% in the treated indium sample with respect to control. Overall, results suggest that biofield energy treatment has substantially altered the atomic, physical, and thermal properties of treated indium powder. Therefore, the treated indium could be utilized in thermal interface material in semiconductor industries.

Physicochemical and Spectroscopic Properties of Biofield Energy Treated Protose

Protose is the enzyme digest of mixed proteins that is recommended for culture media, bulk production of enzymes, antibiotics, toxins, veterinary preparations, etc. This study was proposed to evaluate the effect of biofield energy treatment on the physicochemical and spectroscopic properties of protose. The study was achieved in two groups i.e. control and treated. The control group was remained as untreated, while the treated group was received Mr. Trivedi’s biofield energy treatment. Finally, both the control and treated samples were evaluated using various analytical techniques. The X-ray diffractograms (XRD) of control and treated samples showed the halo patterns peak that suggested the amorphous nature of both the samples of protose. The particle size analysis showed about 12.68% and 90.94 increase in the average particle size (d50) and d99 (particle size below which 99% particles are present) of treated protose with respect to the control. The surface area analysis revealed the 4.96% decrease in the surface area of treated sample as compared to the control sample. The differential scanning calorimetry (DSC) analysis revealed the 22.49% increase in the latent heat of fusion of treated sample as compared to the control. Thermogravimetric analysis (TGA) analysis showed increase in maximum thermal degradation temperature (Tmax) by 5.02% in treated sample as compared to the control. The increase in Tmax might be correlated with increased thermal stability of treated sample as compared to the control. Fourier transform infrared (FT-IR) study showed the alteration in the vibrational frequency of functional groups like N-H, C-H, and S=O of treated protose as compared to the control sample. Based on the overall analytical results, it is concluded that Mr. Trivedi’s biofield energy treatment has a significant impact on the physicochemical and spectral properties of protose. As a result, the treated protose might be more effective as a culture medium than the corresponding control.

Melt processing of poly(L‐lactic acid) in the presence of organomodified anionic or cationic clays

AbstractPoly(L‐lactic acid) (PLA) films are in use for various types of food packaging; however, a wider range of applications would be possible if the barrier properties of these films could be improved. To make such improvements, combinations of PLA with two nanofillers, laurate‐intercalated Mg‐Al layered double hydroxide (LDH‐C12) and a cationic organomodified montmorillonite (MMT) clay (Cloisite® 30B), were investigated. The dispersion of these fillers in PLA by melt processing was explored using two methods, either by mixing the nanofillers with PLA granulate immediately before extrusion or by preparation and subsequent dilution of PLA‐nanofiller masterbatches. After melt processing of these materials, PLA molecular weight, thermal stability, film transparency, morphology, and permeability characteristics were determined. Direct addition of LDH‐C12 drastically reduced the PLA molecular weight. Although this reduction in molecular weight was still very significant, it was less when a PLA/LDH‐C12 masterbatch was processed. In contrast, there was no significant reduction in PLA molecular weight when processing with Cloisite® 30B. However, film transparency was compromised when either LDH or MMT nanofillers were used. Evidence from DSC analyses showed a significant increase in heat of fusion when LDH‐C12 was dispersed in PLA compared with Cloisite® 30B, likely indicating a difference in nucleating properties. Complementary optical purity analyses suggested that racemization as a result of processing could influence the PLA crystallinity as determined by DSC in certain cases. A reduction in thermal stability when incorporating LDH‐C12 could be a direct result of PLA molecular weight reduction. XRD and TEM analyses showed that both Cloisite® 30B‐ and LDH‐C12‐based PLA composites yielded exfoliated and intercalated morphologies, but nanofiller agglomeration was also seen when LDH‐C12 was used. PLA/Cloisite® 30B nanocomposite films exhibited significant enhancement in oxygen and water vapor barrier properties, but no such improvement was found in PLA/LDH‐C12 nanocomposite films. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Effect of radiation dose on the thermal degradation of poly(ethylene terephthalate) fabric

AbstractThe effect of radiation dose (10–30 kGy) on the thermal decomposition of poly(ethylene terephthalate) was studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and X‐ray diffraction (XRD) analysis. The TGA and DSC were carried out in a flowing nitrogen atmosphere at heating rates of 5 and 30°C/min for TGA and 10°C/min for DSC. The degradation process was composed of three overlapping stages. The second stage, at which a rapid degradation occurs, was studied in detail. The process was found to follow a second‐order kinetics and was independent of radiation dose or heating rate. The reaction rate constant (k) was found to depend on the heating rate and iradiation dose. The apparent activation energy (Q) and the logarithm of the preexponential rate constant (log A) were found to decrease linearly with the increase in dose at rates of 3.32 kJ mol−1 kGy−1 and 0.177 s−1 kGy−1 with intercepts of 249 kJ/mol and 12.26 s−1 for Q and log A of unirradiated fabric, respectively. A direct relationship was found between the percentage decrease in Q and log A and the percentage decrease in the temperature corresponding to 50% conversion (T50%) for samples irradiated at different doses. It was found that a decrease in T50% by 1% resulted in a decrease in Q and log A by 1.855 and 2.1%, respectively. Changes in Q and log A resulting from radiation, mechanical and thermal treatments, or their combinations can be predicted from the shift in T50%. The history of the fibers substantially affected the thermal properties. DSC and XRD studies revealed changes in the fabric crystallinity. DSC measurements indicated a linear increase in heat of fusion with dose increase at a rate of 0.855 kJ kg−1 kGy−1. XRD analysis confirmed structural changes, rearrangement by plane rotations, and formation of compact crystalline lattice with patterns characterizing irradiated samples. An attempt to explain the dependency of the apparent activation energy on dose was given. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3710–3720, 2004

The effects of hydrogen peroxide and sterilization on the structure of ultra high molecular weight polyethylene

The effects of hydrogen peroxide and sterilization on the structure and morphology of medical-grade ultra high molecular weight polyethylene (UHMWPE) were studied. Microstructural changes were induced via gamma irradiation sterilization and were accelerated by aging in hydrogen peroxide. Differential scanning calorimetry, density gradient column, transmission electron microscopy and small-angle X-ray scattering were used to characterize the structure. Upon oxidation, a decrease in melting temperature, an increase in heat of fusion, an increase in density, a tortuosity in lamellae, and a tendency to microcrack were observed. Based on the results, a mechanism for the oxidation of UHMWPE is proposed in which oxygen is incorporated into the amorphous phase of the polymer, leading to the development of strains and the breaking of tie molecules in the polymer, which result in the microcracking and embrittlement of the material.

DSC melting behavior of drawn and gamma-irradiated low-density polyethylene

Differential scanning calorimetry measurements (DSC) were used to study the effect of gamma irradiation on the melting behavior of drawn low-density polyethylene (LDPE). The drawing, to various draw ratios (5, 6, 9, 10 and 11), was performed via solid-state stretching at 80 °C. It was found that for the lower doses (50kGy) there is an increase in melting temperature with increasing draw ratio, λ. For the higher doses, the melting temperatures decrease slightly. The increase in heat of fusion with absorbed dose is explained in terms of the strain-energy relief process on the crystals by the scission of tie-molecules and the growth of new thin lamellae.

Towards understanding the increase in strength of thermotropic polyesters with heat treatment

AbstractThermotropic copolyester fibers of oxynaphthoate and oxybenzoate have been subjected to conditions that promote solid‐state polymerization as well as annealing. The annealing process causes the crystals to perfect with a simultaneous increase in heat of fusion and melting temperature. Solid‐state polymerization, a reaction rate‐controlled process, causes the polymer viscosity average molecular weight to increase by chain extension from about 14,000 g/mole to more than 87,000 g/mole with a simultaneous impressive increase in tenacity from about 10 g/d (1.2 GPa) to almost 30 g/d (3.7 GPa). To understand the changes in mechanical properties, we have modeled the fiber structure as short rod‐like molecules poorly bonded to a continuous matrix of parallel molecules. Lengthening of the reinforcing molecules facilitates better transfer of load from matrix to molecules, resulting in higher tenacity fibers. © 1994 John Wiley & Sons, Inc.

Radiation‐induced crystallinity changes in linear polyethylene

AbstractTwo kinds of ultrahigh‐molecular‐weight linear polyethylene (UHMW PE), together with conventional high‐density polyethylene (HDPE), were subjected to β irradiation, and changes in their properties were monitored. Elastic modulus increased steadily with dose for all materials, as did the yield stress. A dramatic rise of density with dose was observed in the UHMW PE specimens accompanied by a corresponding increase in heat of fusion, x‐ray crystallinity, and peak melting temperature. The magnitude of such changes in HDPE was much smaller. In UHMW PE specimens, the x‐ray long period simultaneously decreased but crystal thickness remained constant. No changes in long period occurred in HDPE. The effects are attributed to the scission of tie molecules in UHMW PE followed by a growth in the perfection of the crystal lamellae, and suggest a method for assessing the tie‐molecule content of such materials.