Thermal Characterization (thermal + characterization)

Distribution by Scientific Domains


Selected Abstracts


PHYSICAL, CHEMICAL, and THERMAL CHARACTERIZATION of WHEAT FLOUR MILLING COPRODUCTS,,

JOURNAL OF FOOD PROCESS ENGINEERING, Issue 5 2003
Y.S. KIM
ABSTRACT Hard red winter (HRW) and hard red spring (HRS) wheat milling coproducts (bran, germ, shorts, and red dog) from three commercial flour mills and the Kansas State University pilot mill were evaluated for differences in physical, chemical, and thermal properties. the ranges of bulk density for bran, germ, and red dog determined at three moisture levels were 146.5 to 205.2 kgm,3, 269.2 to 400.6 kgm,3, and 298.9 to 398.1 kgm,3, respectively. the true density ranking order was: red dog >shorts = germ >bran, independently of the moisture level. Red dog had the smallest geometrical mean diameter with the highest variation (coefficient of variation of 23.8%). There was a significant (P < 0.05) difference among wheat blends and milling flows in the thickness of bran and germ at the same particle separation size. the image analysis study determined that the equivalent projected area diameter of bran at the same separation size was significantly (P < 0.05) larger than that of germ. the ratio between the equivalent projected area diameter and the particle thickness were within ranges of 15.7 to 37.6 for bran and 15.5 to 32.2 for germ particles. the chemical composition (ash, protein, lipids and fiber) ranges were determined for each coproduct. Ranges of thermal conductivity for bran, germ, shorts, and red dog were 0.049 to 0.074, 0.054 to 0.0907, 0.057 to 0.076, and 0.063 to 0.080 W(mK),1, respectively. Specific heat of coproducts, measured with a differential scanning calorimeter, exhibited a wider range [1.08,1.94 kJ(kgK),1] than that observed in whole wheat kernels and wheat flour. the variability observed among the samples was due to the different wheat sources and characteristic milling flows for the flour mills. [source]


Nanosized PbZrO3 Powder from Oxalate Precursor: Microwave-Aided Synthesis and Thermal Characterization

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2009
Yuvraj S. Malghe
Nanosized lead zirconate (PbZrO3) powder was synthesized from its oxalate precursor, namely lead zirconyl oxalate (LZO). LZO heated in a microwave heating system for 1 h yielded the PbZrO3 at 600C. The same precursor (LZO), when heated in a resistance-heated furnace at 850C for 3 h, does not give a pure product. Thermogravimetry, differential thermal analysis, and X-ray diffraction techniques were used to characterize the precursor and optimize the conditions for microwave processing. The particle size of PbZrO3 powder prepared at 600C using microwave heating was measured using transmission electron microscopy (TEM). The TEM images show that the particles of PbZrO3 are spherical in shape and that the particle size varies between 20 and 22 nm. [source]


Yttrium Silicate Powders Produced by the Sol,Gel Method, Structural and Thermal Characterization

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003
Damien Boyer
Yttrium silicate (Y2SiO5) powders of high purity have been synthesized using the sol,gel method. Alkoxide precursors were used with commercial tetraethyl orthosilicate as the silica source and yttrium propoxide synthesized from YCl3. Powders calcined from the xerogel showed submicrometer crystal sizes. These powders were sintered at temperatures <1300C and are suitable for coating applications such as a thermal barrier system for SiC/SiC composites. [source]


Synthesis and characterization of dicyanate monomers containing methylene spacers

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008
G. Anuradha
Abstract The bisphenols containing methylene spacer were prepared by treating eugenol/2-allyl phenol with 2,6-dimethyl phenol/guiacol/o -cresol in the presence of AlCl3. All the bisphenols were converted to their respective cyanate esters by treating with CNBr. The structural confirmation was done by FTIR, 1H NMR, 13C NMR spectral methods, and elemental analysis. Thermal characterization was done by DSC and TGA. DSC transition shows that the Tg is in the range of 208,239C. The Tg is highest for the cyanate ester Cy(b) with symmetric structure. The Tg of the cured network depends on the length and symmetry of the monomer, Tg being higher for shorter and the para-substituted monomers. The T10 values are in the range of 364,381C. The char yield is in the range of 47,53%. From the char yield, the limiting oxygen index (LOI) value was determined, which is used to confirm the flame retardancy of the cyanate ester resins. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


Synthesis and characterization of organic/inorganic hybrid star polymers of 2,2,3,4,4,4-hexafluorobutyl methacrylate and octa(aminophenyl)silsesquioxane nano-cage made via atom transfer radical polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2008
H. Hussain
Abstract Well-defined organic/inorganic hybrid fluorinated star polymers were synthesized via atom transfer radical polymerization (ATRP) of 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBMA) using octa(aminophenyl)silsesquioxane (OAPS) nano-cage as initiator. For this purpose, OAPS was transformed into ATRP initiator by reacting with 2-bromoisobutyrylbromide. ATR polymerization of HFBMA was carried out in trifluorotoluene at 75 C using CuCl/2,2-bipyridine or N,N,N,,N,,N,-pentamethyldiethylenetriamine as catalyst system. GPC and 1H NMR data confirmed the synthesis of OAPS/PHFBMA hybrid star polymer. Kinetics of the ATR polymerization of HFBMA using OAPS nano-cage initiator was also investigated. The OAPS/PHFBMA hybrid stars were found to be molecularly dispersed in solution (THF); however, TEM micrographs revealed the formation of spherical particles of , 120,180 nm by the OAPS/PHFBMA hybrid star polymer after solvent evaporation. Thermal characterization of the nanocomposites by differential scanning calorimetry (DSC) revealed a slightly higher glass transition temperature (Tg) (when compared with the linear PHFBMA) of higher molecular weight OAPS/PHFBMA hybrid star polymers. In contrast, lower Tg than the linear PHFBMA was observed for OAPS/PHFBMA of relatively lower molecular weight (but higher than the linear PHFBMA). Thermal gravimetric analysis (TGA) showed a significant retardation (by ,60 C) in thermal decomposition of nanocomposites when compared with the linear PHFBMA. Additionally, surface properties were evaluated by measuring the contact angles of water on polymer surfaces. 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7287,7298, 2008 [source]


Thermal characterization of light-emitting diodes in the frequency domain

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009
Pranci, kus Vitta
Abstract We report on a method for measurement of thermal relaxation time constants within light-emitting diodes (LEDs) using harmonic modulation of the driving current. The method is based on the phase shift of the forward voltage waveform in respect to that of the modulated current. The phase shift is due to the sensitivity of the forward voltage to junction temperature, which responds to the modulation of the heat generation depending on the thermal relaxation rate. The frequency dependence of the phase shift was shown to exhibit characteristic dips at angular frequencies equal to inverse thermal time constants. Such an approach for thermal characterization was demonstrated for common GaP, AlGaAs, AlInGaP, and InGaN LEDs. In particular, low-power p-n and double-heterostructure LEDs as well as high-power truncated-inverted-pyramid and flip-chip LEDs were investigated. The measured thermal time constants (, 0.1,100 ms) were tentatively assigned to heat flows within the multilayer structure of the LEDs and collated with the numerical estimates based on thermal resistance and heat capacitance of the LED components. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Formation of Metastable Na2CrO4 -Type LiNiPO4 from a Phosphate,Formate Precursor

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2010
Violeta Koleva
Abstract High-pressure modification of LiNiPO4 with a Na2CrO4 -type structure was obtained at ambient pressure and low temperature from a mixed LiNi,phosphate,formate precursor, LiNiPO4Hx(HCOO)xyH2O (where x , 1.2 and y , 2.5). The structural and thermal characterization of the precursor and the LiNiPO4 compositions were carried out by powder XRD analysis, IR spectroscopy, and DSC analysis. Thermal treatment of LiNiPO4Hx(HCOO)xyH2O precursors between 450 and 650 C yields a mixture of the two structural modifications of LiNiPO4: the Na2CrO4 type and the olivine type. It was established that the obtained Na2CrO4 -type LiNiPO4 is a metastable phase, which completely transforms at 700 C into the olivine-type phase. The enthalpy of the phase transition is ,H = ,43.40 kJ,mol,1. The mechanism of formation of the two forms of LiNiPO4 from the LiNi,phosphate,formate precursor is discussed. [source]


Compatibilization and development of layered silicate nanocomposites based of unsatured polyester resin and customized intercalation agent

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
Luigi Torre
Abstract In this study a procedure for the preparation of compatibilized nanoclays was used to produce effective nanocomposites based on unsatured polyester (UP) resin. A compatibilization procedure of the filler with a selected surfactant has been developed and optimized, the effect of organic modifiers on the synthesized nanocomposites properties was studied. Moreover, polyester/clay nanocomposites were prepared. In particular, samples were prepared using two different mixing methods. The properties and formation processes of the nanocomposites obtained using the two methods were compared. X-ray diffraction studies revealed the formation of intercalated/exfoliated nanocomposites structures. The effect of processing parameters, used for both the compatibilization procedure and the preparation of nanocomposites, was studied. Dynamic mechanical, thermal analysis, and rheological tests were performed to investigate the formation mechanism of UP/montmorillonite nanocomposite. In particular, mechanical properties of nanocomposites were studied using dynamic mechanical analysis and tensile tests. Mechanical, rheological, and thermal characterization have confirmed the validity of the used approach to compatibilize the nanoclay and to produce nanocomposites. Tensile strength and Young's modulus were modified by the loading of the organoclays. Furthermore, the rheology of the nanocomposite formulation provided processing information, while mechanical and dynamic mechanical characterization was performed on the nanocomposites produced with the newly compatibilized formulation. The results have shown that nanocomposites with better mechanical properties can be obtained through the selection of an appropriate compatibilization process. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


FTIR, 1H-NMR spectra, and thermal characterization of water-based polyurethane/acrylic hybrids

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008
O. R. Pardini
Abstract Polyurethane (PU) polymer was synthesized following a prepolymer mixing process, by polyaddition of isophorone diisocyanate (IPDI), poly(propylene glycol) (PPG), 2-hydroxyethyl methacrylate (HEMA), and 2,2-bis(hydroxymethyl)propionic acid (DMPA). The PU anionomer having 2-ethoxymethacrylate terminal groups was dispersed in water by prior neutralization of carboxylic acid groups of DMPA with triethylamine (TEA), chain extended with hydrazine (HZM) in water and a dispersion polymerization with methyl methacrylate/n -butyl acrylate/acrylic acid mixture was performed. The above polymerization reactions lead to the formation of PU/acrylic hybrids having a chemical bond between PU and acrylic moieties. Acrylic content was varied from 0 to 50 wt % and samples were purified to eliminate oligomers and impurities before characterization. The FTIR and 1H-NMR spectra of these purified hybrid samples were obtained and bands and peaks assignments were discussed. Thermal properties (DSC and TGA) were also discussed. Breaking hydrogen bonds is the main reason for changes in properties with increasing acrylic content. Particle size data of dispersions is also presented and discussed. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


Synthesis and characterization of stimuli-sensitive micro- and nanohydrogels based on photocrosslinkable poly(dimethylaminoethyl methacrylate)

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2007
Smrati Gupta
Abstract The aim of this work was the development of a versatile route for the preparation of temperature- and pH-responsive hydrogels with small dimensions. The copolymerization of N,N -dimethylaminoethyl methacrylate with various amounts (5 and 10 mol %) of dimethylmaleimidoethyl methacrylate in solution with 2,2,-azobisisobutyronitrile as an initiator is described. The structural and molecular characterization of the copolymers was performed with proton nuclear magnetic resonance, Fourier transform infrared, and ultraviolet spectroscopy, as well as size exclusion chromatography. Differential scanning calorimetry and thermogravimetry were used for the thermal characterization of the copolymers. Micro- and nanohydrogels of the copolymers were prepared by photocrosslinking. The gels obtained by photocrosslinking were characterized with a combination of surface plasmon resonance and optical waveguide spectroscopy, dynamic light scattering, and scanning electron microscopy. The hydrogels showed temperature- and pH-responsive behavior. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 669,679, 2007 [source]


Cyclosiloxane-based networks: Synthesis, thermal characterization, and microstructure

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2005
Nihan Nugay
Abstract This article mainly concerns the synthesis of novel PD5/PDMS conetworks by the copolymerization of cyclic D5H and linear HOPDMSOH units, and the characterization of the product by DMTA, DSC, and TGA. The ultimate properties of the conetworks may be controlled by varying the relative composition of D5H and PDMS components. DMTA and DSC thermograms indicate compatibility between the PD5 and PDMS domains. Understanding of the polymer chemical transformations involved in conetwork formation combined with an analysis of DMTA and DSC thermograms led to a proposition of the microarchitecture of PD5/PDMS conetworks. 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 630,637, 2005 [source]


Thermal characterization of light-emitting diodes in the frequency domain

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue S2 2009
Pranci, kus Vitta
Abstract We report on a method for measurement of thermal relaxation time constants within light-emitting diodes (LEDs) using harmonic modulation of the driving current. The method is based on the phase shift of the forward voltage waveform in respect to that of the modulated current. The phase shift is due to the sensitivity of the forward voltage to junction temperature, which responds to the modulation of the heat generation depending on the thermal relaxation rate. The frequency dependence of the phase shift was shown to exhibit characteristic dips at angular frequencies equal to inverse thermal time constants. Such an approach for thermal characterization was demonstrated for common GaP, AlGaAs, AlInGaP, and InGaN LEDs. In particular, low-power p-n and double-heterostructure LEDs as well as high-power truncated-inverted-pyramid and flip-chip LEDs were investigated. The measured thermal time constants (, 0.1,100 ms) were tentatively assigned to heat flows within the multilayer structure of the LEDs and collated with the numerical estimates based on thermal resistance and heat capacitance of the LED components. ( 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Use of carboxylated nitrile rubber and natural rubber blends as retreading compound for OTR tires

POLYMER ENGINEERING & SCIENCE, Issue 12 2008
Kaushik Pal
Ore transportation is one of the important unit operations in a mineral industry. In this study, three raw rubber compounds are prepared in three different blend ratios, and four types of raw rubber samples of pure NR with silica reinforced has been collected from the different tire retreading industries. Blend properties largely depend on the blend ratio and on the blending technique. The improvement in the physical properties such as cure characteristics, mechanical characterization, cross-link density, FTIR, thermal characterization, SEM studies, and dynamic mechanical analysis has been studied in those samples. It has been found that retread rubber made with 80 phr XNBR and 20 phr NR has given the better results when compared with the other samples against all the characterization done. It is also seen that rubber made by the researchers are very good in tough, rigid and these are extremely able to withstand for using as a retread rubber for 35T dump trucks tire when compared with the retread rubber made by the tire retreading industries for different mines in India. POLYM. ENG. SCI., 2008. 2008 Society of Plastics Engineers [source]


Nanocomposite systems based on unsaturated polyester and organo-clay

POLYMER ENGINEERING & SCIENCE, Issue 2 2005
I. Mironi-Harpaz
Unsaturated polyester (UP) systems give rise to numerous possible approaches in synthesizing nanocomposites. A simultaneous mixing method was used to synthesize UP-resin/organo-clay nanocomposites. The effects of various mixing processes, using several organically-modified clay types, were investigated. The incorporation of these organo-clays resulted in an intercalated structure, the extent of which depended mainly on the type of the clay organic treatment. Organo-clays that exhibited the highest intercalation levels were further studied using a sequential mixing method. The UP-alkyd (without styrene) was mixed with different organo-clays. Processing parameters such as mixing modes, applied shearing levels, clay contents, and mixing-temperatures were investigated. Prolonged high shear levels promoted the intercalation and exfoliation of the silicate layers, resulting in a better dispersion of clay particles. The high shear levels effects were achieved by vigorous mechanical mixing and were intensified by using large amounts of clay and optimized matrix viscosity. Rheological studies of the nanocomposites were found complementary and in correlation with morphological and thermal characterization. This methodological approach provides a basis for understanding the structuring processes involving the formation of the UP/clay nanocomposites and establishing materials-processing-structure interrelations. Polym. Eng. Sci. 45:174,186, 2005. 2005 Society of Plastics Engineers. [source]


Alternating poly(ester amide)s from succinic anhydride and ,,,-amino alcohols: synthesis and thermal characterization,,

POLYMER INTERNATIONAL, Issue 10 2003
Thomas Fey
Abstract Alternating poly(ester amide)s 6a,e from succinic anhydride and ,,,-amino alcohols H2N,(CH2)x,OH (x = 2,6) 2a,e were obtained in two steps: ,-carboxyl-,-hydroxy amides 3a,e were prepared from the starting materials in a highly selective reaction, followed by a polycondensation reaction. 1H and 13C NMR analyses of the poly(ester amide)s clearly reveal the alternating microstructure. The poly(ester amide)s with homologous ,,,-amino alcohols H2N,(CH2)x,OH (x = 2,6) are semi-crystalline materials, their melting points show the odd/even effect observed for [n]-polyamides and [n]-polyurethanes. Heating the poly(ester amide)s 6a,e yields the corresponding N -(hydroxyalkyl) imides 4a,e with no trace of cyclic ester amides. Theoretical calculations revealed that the cyclic ester amides 5a,e are clearly richer in energy than the isomeric N -(hydroxyalkyl) imides. These results show that cyclic ester amides can not be prepared from N -(hydroxyalkyl) imides by ring-enlargement reactions. Copyright 2003 Society of Chemical Industry [source]


Electromagnetic and thermal characterization of an UHF-applicator for concurrent irradiation and high resolution non-perturbing optical microscopy of cells

BIOELECTROMAGNETICS, Issue 8 2006
William F. Pickard
Abstract To permit trans-illuminated, high-resolution optical microscopy during unperturbed ultrahigh frequency (UHF) irradiation, a novel new class of applicator has been designed based upon a shielded-pair transmission line. As constructed and tested with water-immersion optics and air cooling, the applicator works most robustly over 700,1100 MHz and permits SARs at the cell layer as high as 50 W/kg before the steady state temperature rise at the cell-layer exceeds 0.5 K. Bioelectromagnetics 27:593,601, 2006. 2006 Wiley-Liss, Inc. [source]


Vibrational 13C-cross-polarization/magic angle spinning NMR spectroscopic and thermal characterization of poly(alanine-glycine) as model for silk I Bombyx mori fibroin

BIOPOLYMERS, Issue 5 2003
Patrizia Monti
Abstract This study focuses on the conformational characterization of poly(alanine-glycine) II (pAG II) as a model for a Bombyx mori fibroin silk I structure. Raman, IR, and 13C-cross-polarization/magic angle spinning NMR spectra of pAG II are discussed in comparison with those of the crystalline fraction of B. mori silk fibroin (chymotryptic precipitate, Cp) with a silk I (silk I-Cp) structure. The spectral data give evidence that silk I-Cp and the synthetic copolypeptide pAG II have similar conformations. Moreover, the spectral findings reveal that silk I-Cp is more crystalline than pAG II; consequently, the latter contains a larger amount of the random coil conformation. Differential scanning calorimetry measurements confirm this result. N-Deuteration experiments on pAG II allow us to attribute the Raman component at 1320 cm,1 to the amide III mode of a ,-turn type II conformation, thus confirming the results of those who propose a repeated ,-turn type II structure for silk I. The analysis of the Raman spectra in the ,NH region confirms that the silk I structure is characterized by the presence of different types of H-bonding arrangements, in agreement with the above model. 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 329,338, 2003 [source]