Thermal Characterization of 1.3 μm InAsP/InGaAsP Ridge Waveguide MQW Lasers Based on Spectroscopy Method

An experimental way to analyze the thermal characterization of semiconductor lasers based on spectroscopy method under pulse driving conditions has been developed. By using this way the thermal characteristics of strain compensated 1.3 μm InAsP/InGaAsP ridge waveguide MQW laser diodes have been investigated. Results show that by measuring and analyzing the lasing spectra under appropriate driving parameters and temperature ranges, the thermal resistance of the laser diodes could be deduced easily. A higher thermal resistance of 640 K/W has been measured on a narrow ridge laser chip without soldering. Other thermal and spectral properties of the lasers have also been measured and discussed.

Thermal Characterization of 1.3 μm InAsP/InGaAsP Ridge Waveguide MQW Lasers Based on I-V Method

An experimental way for the thermal characterization ofsemiconductor lasers based on I-V method under pulse drivingconditions has been developed, with which the thermal characteristicsof strain compensated 1.3 μm InAsP/InGaAsP ridge waveguide MQW laserchips have been investigated. The results show that, by measuring andanalyzing the I- V characteristics under appropriate pulse drivingconditions at different has sink Temperatures, the thermal resistanceof the laser diodes could be easily deduced. The driving Current andjunction voltage waveforms of the laser ships under different pulsedriving Conditions are also discussed.

Intersheet Distance Modeling and Thermal Characterization of New Micro/Nano-Composites Composed by Clay Matrix and PEG 6000 Addition

Nowadays, the energetic efficiency becomes one of the major interests of the global society. Thus, the energetic challenges of the new century enforce the scientific and industrial environment to the development of new efficient materials, which present more than the classical thermal properties, according to the energy storage, energy consumption and other specific needs. In this context, the present work constitutes the third step of the development of a new kind of composite materials (micro-composites and nano-composites), using natural marl (clay) clay and biodegradable polymer, which is the PolyEthylene Glycol 6000 (PEG 6000). This step corresponds to characterization of the variation of the specific heat (denoted Cp) of the materials elaborated. So, in order to estimate the capacity of thermal energy adsorption, we utilized a SHIMATZU-DSC 60 Differential Scanning Calorimeter. The main results present the evolution of the Cp according to the PEG 6000 doping and also the specific melting enthalpy of the polymer within the natural clay matrix;by the way this enthalpy constitutes the specific heat stocked in the materials.

Synthesis and Thermal Characterization of Solar Salt-Based Phase Change Composites with Graphene Nanoplatelets

Thermal energy storage(TES) systems use solar energy despite its irregular availability and day-night temperature difference.Current work reports the thermal characterizations of solar salt-based phase change composites in the presence of graphene nanoplatelets(GNP).Solar salt(60:40 of NaNO_(3):KNO_(3)) possessing phase transition temperature and melting enthalpy of 221.01℃ and 134.58 kJ/kg is proposed as a phase change material(PCM) for high-temperature solar-based energy storage applications.Thermal conductivity must be improved to make them suitable for widespread applications and to close the gap between the system needs where they are employed.GNP is added at weight concentrations of 0.1%,0.3%,and 0.5% with solar salt using the ball milling method to boost its thermal conductivity.Morphological studies indicated the formation of a uniform surface of GNP on solar salt.FTIR spectrum peaks identified the physical interaction between salt and GNP.Thermal characterization of the composites,such as thermal conductivity,DSC and TGA was carried out for the samples earlier and later 300 thermal cycles.0.5% of GNP has improved the thermal conductivity of salt by 129.67% and after thermal cycling,the enhancement reduced to 125.21% indicating that thermal cycling has a minor impact on thermal conductivity.Phase change temperature decreased by around 2.32% in the presence of0.5% GNP and the latent heat reduced by 4.34% after thermal cycling.TGA thermograms depicted the composites initiated the weight loss at around 550℃ after which it was rapid.After thermal cycling,the weight loss initiated at ~40℃ lower compared to pure salt,which was found to be a minor change.Thermal characterization of solar salt and GNP-based solar salt composites revealed that the composites can be used for enhanced heat transfer in high-temperature solar-based heat transfer and energy storage applications.

The Thermal Character of the Underwater Heat Exhausting Source

The underwater heat exhausting source can cause the thermal difference of the surrounding and surface water.In this paper,the thermal character caused by the underwater heat exhausting source is studied by numerical simulation and experiment.The results show that the thermal floating distance is related with the sailing velocity of the underwater target.The higher the velocity is,the longer the hot wake is,and the broader the hot scope is.The relative distance of the thermal floating spot is almost in a logarithmic law with the velocity.The experimental results are accordant with the numerical simulation,and the obvious hot wake can be observed by the moving underwater heat exhausting source testing with temperature sensors and infrared camera.

Thermomechanical Characterization of Three Soils of Abeche in Chad

The study carried out concerns the valorization of agricultural waste for the development of biosourced materials that can be used as insulation in homes. This article is devoted to the influence of gum arabic on the mechanical and thermal properties of clay soils in the town of Abéché. The mechanical tests were carried out using the CBR press equipped with two devices (bending device and compression device). Thermal property such as thermal conductivity was determined by the hot wire method and thermal resistance was derived by calculation. Thus, the tests were carried out on test pieces made from a mixture of clay and gum arabic in solution. The experimental program includes seven formulations (0%, 2%, 4%, 6%, 8%, 10% and 12%). The results obtained showed that the best flexural and compressive strengths are obtained by using gum arabic with a rate of 8% and a maximum stress of 4.3 MPa. In addition, the thermal results also showed that the thermal conductivity decreases when the percentage of gum arabic increases, which makes it possible to increase the thermal resistance, thus confirming the capacity of gum arabic to provide thermal insulation.

Synthesis, Characterization and Thermal Decomposition Mechanism of Cetyltrimethyl Ammonium Tetrathiotungstate

The synthesis, characterization and thermal decomposition mechanism of cetyltrimethyl ammonium tetrathiotungstate （CTriMATT） were studied herein. The as-synthesized CTriMATT was characterized by Elemental analysis, X-ray diffraction （XRD）, Fourier transform infrared （FT-IR）, Ultraviolet visible （UV-Vis） spectra. The results showed that the as-synthesized CTriMATT had high purity and good crystallinity. The introduction of alkyl groups induced a shift of the stretching vibration band of W-S bond to lower wavenumber, while it had no influence on the position of WS4^2-. Thermogravimetric analysis （TG）, differential thermal analysis （DTA） and in situ XRD characterizations revealed that CTriMATT began to decompose at 423 K in nitrogen and was converted to WS2 eventually. In addition, the decomposition product of CTriMATT at 673 K in nitrogen was characterized by N2 adsorption （BET） and scanning electron microscopy （SEM）. The results demonstrated that WS2 with higher specific surface area, and pore volume could be obtained from the thermal decomposition of CTriMATT in nitrogen.

Synthesis,Crystal Structure,Spectroscopic Characterization,Thermal Stability and Magnetic Properties of a Dinuclear Copper(Ⅱ) Complex

A new copper（Ⅱ） complex [Cu2（MNA）2（2,2‘-bipy）2]·2.5H2 O with methy-5-norbornene-2,3-dicarboxylic acid（MNA） and 2,2’-bipyridine as ligands has been synthesized in the mixed solvents of DMF and water.It crystallizes in monoclinic,space group P 1,with a = 10.4191（11）,b = 12.8883（13）,c = 16.1114（16） A,α = 70.8090（10）,β = 80.568（2）,γ = 77.440（2）o,V = 1984.3（4） A^3,Dc = 1.551 g/cm^3,Z = 2,F（000） = 962,the final GOOF = 1.051,R = 0.0431 and w R= 0.0980.The crystal structure shows that the whole molecule consists of two independent dinuclear units,in which two copper ions are bridged by two μ2-η^1：η^0 3-carboxylate groups of MNA^2-.The coordination environment of Cu（Ⅱ） ion is Cu O3N2,giving a distorted square pyramidal geometry.The spectroscopic characterization,thermal stability and magnetic properties of the complex were investigated.

Thermal, Hardness and Microstructural Characterization of Al-Si-SiC_pComposites

This study investigated the effects of silicon and silicon carbide particles contents on the thermal, hardness and microstructural behaviour of Al-Si-SiCp composites. 16 samples of the composite produced by stir casting technique were of silicon contents of 1, 2, 3 and 4% by weigh, and silicon carbide contents of 0.5, 1, 1.5 and 2% by weight for each composition of silicon. Each of the samples were subjected to homogenizing annealing heat treatment. Differential thermal analysis (DTA), hardness test and microstructural analysis were then performed on the samples from each composition. The results obtained showed that the hardness of the composite increased gradually as the silicon and silicon carbide particles content increased. The micrographs obtained revealed the presence of silicon carbide, silicon precipitates and aluminium carbide (Al4C3) within the metallic matrix. The amounts of these phases varied with the silicon and silicon carbide content. All the samples gave DTA curves with major endothermic peaks between 550 – 570℃ and two sets of exothermic peaks between 580 – 610℃ for the first set and between 565 – 570℃ for the second set. It was inferred from the study that although varied silicon and silicon carbide contents affected the thermal, hardness and microstructural behaviour of the Al-Si-SiCp composites, the variation of the SiCp content had a more pronounced effect on the hardness value of the Al-Si-SiCp composite.

Characterization of Failure Mechanisms of Duplex and Graded Thermal Barrier Coatings Exposed to Thermal Shock Test

The beginning of failure of a (ZrO2-7%Y2O3)/(Ni-22%Co-17%Cr-12.5%Al-0.6%Y) duplex andgraded coating systems on lnconel 617 and IN738LC in burner rig tests has been characterized.The test conditions are 40 s heating up to 75O℃ substrate temperature followed by 80 s aircooling. Failure is considered at the appearance of the first bright spot during heating period.Stresses due to thermal expansion mismatch strains on cooling are the probable cause of life-limiting in this conditions of testing.

Synthesis,Crystal Structure,Spectroscopic Characterization and Thermal Stability Properties of a Trinuclear Zinc(Ⅱ) Complex

A new trinuclear zinc complex Zns（2,2＂-bipy）2（3,5-DMBA）6＂（H20）1.5 （1） with 3,5-dimethylbenzoic acid （3,5-DMBA） and 2,2＂-bipyridine as ligands has been synthesized in the mixed solvents of methanol and water. It crystallizes in the monoclinic space group C2/c with a = 31.1497（15）, b = 11.7576（6）, c = 20.9049（10） A, fl = 118.4550（10）°, V- 6731.4（6） A3, Dc = 1.412 g/cm3, Z = 4, F（000） = 2972, GOOF = 1.069, the final R= 0.0667 and wR= 0.1917. The whole molecule consists of three zinc ions, six 3,5-DMBA molecules, two 2,2＂-bipyridine molecules and one and half water molecules, in which three zinc ions are bridged by six μ2-η1：η0 carboxylate groups of 3,5-DMBA. The Zn（1） atom is centrosymmetric, and adopts a distorted octahedral ZnO6 geometry, while the Zn（2） gives a distorted square pyramidal ZnOsN2 geometry. The spectroscopic characterization and thermal stability properties of the complex were investigated.

Synthesis Characterization Non-isothermal Kinetics of the Thermal Decomposition and Redox Properties Derived from Copper(Ⅱ) Binuclear Coordination Compound of 1,4-Bis-(1'-Phenyl-3'-Methyl-5'-Pyrazolone-4')-1,4-Butanedione

The paper reports the synthetic procedure and character of Copper(II) binuclearcoordination compound of 1,4-bis-(1'-phenyl-3'-methyl-5'-pyrazolone Thenon-isothermal kinetics of thermal decomposition of the complex has been stUdied from the TG-DTGcurves by means of the Achar et al. and Coats-Redfern methods,the most probab1e kinetic equation canbe expressed as dofdtrAe -E / RT * l /(2Q).The corresponding kinetic compensation effect expressions arefound to be lnuA=0. 1794E+0. 1689.The non-isothermal thermal decomposition process of the complex isone-dimensional diffusion.But electrochemical studies of the complex(Cu2L'2)from cyclic voltamrnetriccurves by means of powder microelectrodes technique'',shows one two-electron irreversible process.

Characterization of gradient Ni-Fe/SiC composite coating on mild steel by thermal spraying in combination with laser cladding

Metal matrix composite coating Ni-Fe/SiC was prepared on an iron-based substrate bythermal spraying combined with laser cladding,using SiC particulates as the reinforcing agent.The micro-structures of the coatings formed at different thermal spraying and laser cladding conditions were character-ized by means of X-ray diffraction and electron probe microanalysis.The thermal oxidation properties of themixed powders composed of different content of SiC particulates and relevant Ni-based alloy as the balancewere examined using differential scanning calorimetry.The hardness profile of the thermal sprayed and lasercladding coatings was investigated as well.It was found that SiO2particulates were generated and dissolvedand dispersed during the melting and solidification of the laser cladding process,which was ascribed to theoxidation of the dispersed SiC particulates.The micro-hardness depth profile of the target laser claddingcomposite coating was characterized by gradient distribution,which could be related to the gradient distribu-tion of the hard SiC and SiO2particulates in the dendrites and interdendrites of the cladding layer.Both SiCand SiO2particulates contributed to greatly increasing the microhardness and mechanical properties of the ti-tled laser cladding composite coatings.

SEMI-QUANTITATIVE CHARACTERIZATION OF SEGMENT DISTRIBUTION IN LLDPE BASED ON THERMAL SEGREGATION

Based on successive multiple-step isothermal crystallization and self-nucleation annealing methods, a novel semi-quantitative method for the characterization of segment distribution in linear low density polyethylene (LLDPE) was established by treating the thermal analysis data using the Gibbs-Thomson equation. The method was used to describe the segment distribution of Ziegler-Natta catalyzed LLDPE (Z-N LLDPE), metallocene catalyzed LLDPE (m-LLDPE) and two commercial LLDPEs with wide molecular weight distribution. The differences of the results obtained from the two thermally treated samples were compared. The results of segment distribution of the polymers were discussed according to their microstructure data and were compared with their characteristics. It can be deduced from the results that this characterization method is effective to characterize the sequence structure of the branched ethylene copolymers.

Thermal and Physicochemical Characterization of Fibers from Coffee Hulls as Filler for Linear Low Density Polyethylene (LLDPE)

This work presents the thermal, physical and chemical characterization of Coffee canephora, from littoral region of Cameroon, for their use as reinforcement for polymeric materials. The infrared of coffee hulls shows the presence of a large peak intensity at 3299 cm-1 that can be attributed to O-H stretching group of alcohol (cellulose content in coffee pulp). The intensity 2926 cm-1 can be attributed to C-H stretching group of alkanes or the vibration of methoxy group of lignin. Thermo gravimetric analysis shows that around 440°C, the biomass has been completely consumed;the temperature profiles show a peak at 86°C that could correspond to the loss of water as evaporation at a percentage of 8%;the peak at 321°C is accompanied by a water loss of 64.50%; this temperature is assimilated to the degradation of hemicelluloses;the temperature range from 321°C to 401°C is accompanied by a loss of mass of 22.80%, which would be due to the degradation of cellulose. SEM images of the surface of raw coffee hulls, coffee hulls treated with caustic soda respectively clearly reveal gaps between the fibers. The results showed that the incorporation of coffee hulls fiber in LLDPE matrix might result in composites with suitable property application for various industrial fields;especially those that were mechanical features are crucial, such as the replacement of engineering plastics.

Effect of Phenolation, Lignin-Type and Degree of Substitution on the Properties of Lignin-Modified Phenol-Formaldehyde Impregnation Resins: Molecular Weight Distribution, Wetting Behavior, Rheological Properties and Thermal Curing Profiles

Here,the effects of substituting portions of fossil-based phenol in phenol formaldehyde resin by renewable lignin from two different sources are investigated using a factorial screening experimental design.Among the resins consumed by the wood-based industry,phenolics are one of the most important types used for impregnation,coating or gluing purposes.They are prepared by condensing phenol with formaldehyde(PF).One major use of PF is as matrix polymer for decorative laminates in exterior cladding and wet-room applications.Important requirements for such PFs are favorable flow properties(low viscosity),rapid curing behavior(high reactivity)and sufficient self-adhesion capacity(high residual curing potential).Partially substituting phenol in PF with bio-based phenolic co-reagents like lignin modifies the physicochemical properties of the resulting resin.In this study,phenol-formaldehyde formulations were synthesized where either 30%or 50%(in weight)of the phenol monomer were substituted by either sodium lignosulfonate or Kraft lignin.The effect of modifying the lignin material by phenolation before incorporation into the resin synthesis was also investigated.The resins so obtained were characterized by Fourier Transform Infra-Red(FTIR)spectroscopy,Size Exclusion Chromatography(SEC),Differential Scanning Calorimetry(DSC),rheology,and measurements of contact angle and surface tension using the Wilhelmy plate method and drop shape analysis.

Synthesis and Characterization of Hydrogels Based on Potato Starch/Poly(vinyl Alcohol)/N,N′-Methylenebisacrylamide

Several hydrogels were synthesized by free-radical polymerization in an aqueous medium based on potato starch(PS),poly(vinyl alcohol)(PVA),and N,N′-Methylenebisacrylamide(MBAm),being possible to study these hydrogels as a function of the proportion of components incorporated.In this way,the products generated from the synthesis were characterized by swelling and deswelling kinetics,the first swelling being verified with Schott and statistical models,allowing to contrast the proximity between the experimental and theoretical behavior.Additionally,water retention in soil(R%),spectroscopy(FTIR),morphological(SEM),and thermal(TGA and DSC)analysis allowing to know the intrinsic characteristics of the material,increasing in general terms the knowledge of this type of material.In this context,it was possible to verify the characteristics and effectiveness of the synthesis and crosslinking of the main components.The experimental results obtained show that the synthesized hydrogels present representative swellings consistent with kinetic and statistical models,optimal thermal stability depending on the amount of crosslinker,and excellent water retention in environments such as soil,presenting it as an excellent alternative to be used in agro-industrial applications in an eco-friendly way.

Synthesis and Characterization of (E)-5-[2-(N-hexylcarbazolyl)vinyl] furan Derivatives with Acceptor Groups

A new series of (E)-5-[2-(N-hexylcarbazolyl)vinyl]furan chromophores with various accepters have been synthesized by the Knoevenagel condensation of (E)-5-[2-(N- hexylcarbazolyl) vinyl]-2-furaldehydes with malononitrile, 1,3-diethyl-2-thiobarbituric acid, or 3-phenyl-5-isoxazol one, respectively. They are characterized by H-1-NMR, FT- IR, UV-VIS, MS and elemental analysis, and have shown strong solvatochromism and high thermal stability.

Electrochemical synthesis and characterization of tantalum alkoxides

Tantalum(Ⅴ)propoxide(Ta(OPrn)5),isopropoxide(Ta(OPr i )5)and butoxide(Ta(OBu n )5)were synthesized by electro- chemical reactions of corresponding alcohol at sacrificial tantalum anode in the presence of tetraethylammonium chloride as a conductive additive.The pure products were isolated by reduced pressure distillation under 5 kPa.The crystal of Ta(OPri)5 was obtained by recrystallization from hexane at-10℃.These samples were characterized by Fourier transform infrared spectra(FT-IR), Raman spectra,nuclear magnetic resonance spectra(NMR),TG/DTA and ICP-MS.The results show that direct electrochemical synthesis of metal alkoxides has a high current efficiency and electrolysis yield.These alkoxides have a high purity of 99.97%and can be directly used as the precursor of Ta2O5 films.

TiO_2 nanofilm growth by Ti ion implantation and thermal annealing in O_2 atmosphere

TiO2 nanofilms on surface of fused silica were fabricated by Ti ion implantation and subsequent thermal annealing in oxygen ambience. The silica glasses were implanted by 20 k V Ti ions to 1.5 × 1017ions/cm2 on an implanter of metal vapor vacuum arc(MEVVA) ion source. Effects of annealing parameters on formation,growth and phase transformation of the TiO2 nanofilms were studied in detail. Optical absorption spectroscopy,Raman scattering spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy measurements were done to figure out formation mechanism of the TiO2 nanofilms.The formation of TiO2 nanofilms was due to out-diffusion of the implanted Ti ions to the substrate surface,where they were oxidized into TiO2 nanoparticles. Formation, phase, and thickness of the TiO2 nanofilms can be well tailored by controlling annealing parameters.