Solid fraction evolution characteristics of semi-solid A356 alloy and in-situ A356–TiB_2 composites investigated by differential thermal analysis

The key factor in semi-solid metal processing is the solid fraction at the forming temperature because it affects the microstructure and mechanical properties of the thixoformed components. Though an enormous amount of data exists on the solid fraction-temperature re- lationship in A356 alloy, information regarding the solid fraction evolution characteristics of A356-TiB2 composites is scarce. The present article establishes the temperature-solid fraction correlation in A356 alloy and A356-xTiB2 （x = 2.5wt% and 5wt%） composites using dif- ferential thermal analysis （DTA）. The DTA results indicate that the solidification characteristics of the composites exhibited a variation of 2℃ and 3℃ in liquidus temperatures and a variation of 3℃ and 5℃ in solidus temperatures with respect to the base alloy. Moreover, the eutectic growth temperature and the solid fraction（fs） vs. temperature characteristics of the composites were found to be higher than those of the base alloy. The investigation revealed that in-situ formed TiB2 particles in the molten metal introduced more nucleation sites and reduced undercooling.

Thermal testing methods in determination ofcharacterization of charcoals

Thermal analysis testing methods were used in determination of the characterization of charcoals. Thermogravimetry (TG) method was adopted to determine the composition of charcoals, which include moisture, volatiles, fixed carbon and ash contents. The result showed that this method could detect the subtle change of charcoal composition, even the variation of different parts of material. Differential Thermal analysis (DTA) and related methods were also used to investigate reactivity of charcoals. The ignition temperature decrease with increasing carbon content was detected by these methods.

Thermal Decomposition of Leightonite, K_2Ca_2Cu(SO_4)_4·2H_2O

The thermal decomposition of Leightonite, K2Ca2Cu（SO4）4·2H2O, was studied by thermal gravimetric analysis（TGA）, differential thermal analysis（DTA）, X-ray diffraction（XRD）, etc. The results show that the Leightonite is dehydrated around 170 ℃ to 390 ℃ and transformed to be new intermediate （K-Cu-SO4） sulphate salt with bright-green color. Moreover, the chemical structure changes during the thernal decomposition process was describled in detail. And the as-resulting phases are demonstrated to be K2Ca2（SO4）3, K2SO4, CaSO4 ,and Cu2O.

Effects of Friction Heat on the Tribological Properties of the Woven Self-lubricating Liner

In the dry-sliding process of the woven self-lubricating liner which is used in the self-lubricating spherical plain bearing, the friction heat plays an important role in the tribological performances of the liner. It has important value to study on the relationship between tribological performances of the liner and the friction heat. Unforttmately, up to now, published work on this relationship is quite scarce. Therefore, the effect of friction heat on the tribological performances of the liner was investigated in the present work. The tribological behaviors of the liner were evaluated by using the high temperature end surface wear tester. Scanning electron microscopy （SEM） was utilized to examine the morphologies of worn surfaces of the liner and study the failure modes. Differential scanning calorimetry （DSC） measurement and X-ray diffraction （XRD） analysis were performed to study the behaviors of the wear debris. The temperature rise on the worn surface was calculated according to classical models. SEM observation shows that the dominating wear mechanism for the liner is mainly affected by friction shear force, contact pressure and friction heat. Higher fusion heat for the wear debris than that for the pure polytetrafluroethylene （PTFE） indicates that the PTFE is the main portion of the wear debris, and, the PTFE in the wear debris shows a higher crystallisation degree owing to the effects of friction shear force and the friction heat. Combining the calculated temperature rise results with the wear rate of the liner, it can be concluded that the effects of temperature rise o n the tribological performances of the liner become more obvious when the temperature rise exceeds the glass transition temperature （Tg） of the PTFE. The wear resistance of the liner deteriorates dramatically when the temperature rise approaches to the melting point （Ton） of the PTFE. The tribological performances of the liner can be improved when the temperature rise exceeds Tg but is far lower than Ton- The present study on the relationship between the temperature rise and the tribological performances of the liner may provide the basis for further understanding of the wear mechanisms of the liner as well as the relationship between the formation of the PTFE transfer film and the friction heat during the dry-sliding of the Finer.

Effect of partition coefficient on microsegregation during solidification of aluminium alloys

In the modeling of microsegregation, the partition coefficient is usually calculated using data from the equilibrium phase diagrams. The aim of this study was to experimentally and theoretically analyze the partition coefficient in binary aluminum--copper alloys. The sam- ples were analyzed by differential thermal analysis （DTA）, which were melted and quenched from different temperatures during solidifica- tion. The mass fraction and composition of phases were measured by image processing and scanning electron microscopy （SEM） equipped with an energy-dispersive X-ray spectroscopy （EDS） unit. These data were used to calculate as the experimental partition coefficients with four different methods. The experimental and equilibrium partition coefficients were used to model the concentration profile in the primary phase. The modeling results show that the profiles calculated by the experimental partition coefficients are more consistent with the experi- mental profiles, compared to those calculated using the equilibrium partition coefficients.

Effect of Melt Superheating on the Morphology of MC Carbide in a Cast Ni-base Superalloy M963

The effect of the melt superheating temperature on the as cast microstructure of a cast nickel base superalloy M963 has been investigated. The results show that the as cast microstructure of the alloy consists of γ solid solution matrix,γ′ precipitate in cubic shape, (γ+γ′) eutectic and MC carbide, and the morphology of MC carbide in the microstructure can be varied from coarse scriptlike, fine scriptlike to fine cubelike or discontinuous particles by increasing the melt superheating temperature. The mechanism of melt superheating is discussed by means of differential thermal analysis (DTA) technique.

Rate of pozzolanic reaction of two kinds of activated coal gangue

Two kinds of activated ways are used to prepare activated coal gangue fine powder, one is calcining coal gangue at 800℃ （gangue A）, and the other is calcining coal gangue with a certain calcite at 800℃ （gangue B）. The experiment shows that strengths of blended cement mortar with coal gangue B are higher than that of blended cement with coal gangue A. Hydration of cements with the two kinds of activated coal gangue is investigated through a differential thermal analysis. The weight loss due to Ca（OH）2 decomposition of hydration products by differential thermal analysis/thermo gravimetric （DTA/TG） can be used to quantify the pozzolanic reaction. A new method based on the composition of hydration cement is proposed to determine the degree of pozzolanic reaction. The results obtained suggest that the degree of pozzolanic reaction of gangue B is faster than that of gangue A.

Characterization of a Rarely Encountered Sericite with Earthy Luster

A rarely encountered sericite was investigated using X-ray diffraction,differential thermal analysis,and scanning electron microscopy.XRD analysis shows that the pattern of the sericite in the sample is similar to that of illite.DTA (TG) analyses show that only a weak heat absorption reaction takes place at 566℃,which is contributed to the polymorphic transformation of quartz,and no change in mass was detected in the range from ambient temperature to 800℃.These reveal that no water escapes from the crystal structure of the clay mineral during heating and therefore indicated that the clay mineral is obviously sericite in species instead of illite.SEM observations show that the sericite particles are significantly small in size and growth steps and irregular structures develop on the crystal surfaces as well as the colored mineral inclusions,which might suggest some loss of optical properties of the sample and thus lead to the variance,with earthy luster of the aggregate,from typical sericite in optical characters.

Phase diagram of the CsBr-CaBr_2 system

The phase diagram of the CsBr-CaBr2 system was re-determined by using differential thermal analysis and high ternperature and room ternperature X-ray diffraction analysis. It is concluded that there are three intermediate compounds in this system： a.congruently melting compound, CsCaBr3, with a melting point of 823℃ and two incongruently melting compounds, Cs2CaBr4 and Cs3Ca2Br7, whose peritectic points being 597℃ and 635℃, respectively. X-ray diffraction analysis indicated that compound CsCaBr3 is of slightly distorted perovskite structure.

PREPARATION AND CHARACTERIZATION OF SCHIFF BASE POLYMERS DERIVED FROM 4,4'-METHYLENEBIS(CINNAMALDEHYDE)

New Schiff base polymers poly[4,4＇-methylenebis（cinnamaldehyde）ethylenediimine] （PMBCen）, poly[4,4＇- methylenebis（cinnamaldehyde）1,2-propylenediimine] （PMBCPn）, poly[4,4＇-methylenebis（cinnamaldehyde）1,3-propylenediimine] （PMBCPR）, poly[4,4＇-methylenebis（cinnamaldehyde） 1,2-phenylenediimine] （PMBCPh）, poly[4,4＇-methylenebis（cinnamaldehyde）meso-stilbenediimine] （PMBCS）, poly[4,4＇-methylenebis（cinnamaldehyde）urea] （PMBCUR）, poly[4,4＇- methylenebis（cinnamaldehyde）semicarbazone] （PMBCSc）, poly[4,4＇-methylenebis（cinnamaldehyde）thiosemicarbazone] （PMBCTSc） and poly[4,4＇-methylenebis（cinnamaldehyde）hydrazone] （PMBCH） were formed by polycondensation of 4,4＇- methylenebis（cinnamaldehyde） with ethylenediamine, 1,2-propylenediamine, 1,3-propylenediamine, 1,2-phenylenediamine, meso-stilbenediamine, urea, semicarbazide, thiosemicarbazide and hydrazine, respectively. The dialdehyde and polymers have been characterized through elemental micro-analysis, IR, UV-Vis and ^1H-NMR spectroscopic techniques. Thermoanalytical studies and viscous flow of dilute solutions of dialdehyde and its polymers have been examined and compared.

Complexes of Rare Earth Picrates with 1,10-Phenanthroline-N-Oxide

Rare earth picrate complexes with the ligand PhenNO, RE(PhenNO)2(pic)3(RE = La, Pr, Nd, Sm to approximately Tb, Er, Y), have been prepared in non-aqueous medium. The complexes were characterized by elementary analysis, molar conductance, IR, Raman, electronic, fluorescence and 1H NMR spectra and TG-DTA techniques.

Studies on Rare Earth Complexes with Ethylene-1,2-Dioxydiacetic Acid

Some new complexes RE2(EDODA)3&middot3H2O, where RE = La, Nd, Eu, Gd, Tb, Er, Yb, Lu and Y, EDODA = ethylene-1,2-dioxydiacetate, have been synthesized and characterized by elemental analysis, molar conductance, IR spectra, UV spectra, TG-DTA, 1H NMR and 13C NMR spectra. Various analyses indicate that the complexes are of nine-coordinated binuclear structure. The carboxylates are bidentate ligands and the ether oxygen atoms also coordinate to rare earth ions. Three water molecules are crystalline water. In addition, the influence of concentration on the chemical shift has been studied through the 1H NMR spectra of the complex Lu2(EDODA)3&middot3H2O in different concentrations.

Calcium Hydroxytitanate in Bayer Digestion Process

Calcium hydroxytitanate formed in the Bayer digestion process of Chinese diasporic bauxite was studied. Interplanar spacings of calcium hydroxytitanate crystal were determined by XRD analysis. Only one endothermic peak occurs at 550-560°C on the DTA curve. IR spectrometry has revealed that hydroxyl exists in calcium hydroxytitanate instead of crystal water. Observation under SEM has indicated that the crystal grains are in the shape of regular hexagonal plates 2-8 μm in edge length and less than 1 μm in thickness. The influences of various digestion conditions on the formation and transformation of calcium hydroxytitanate and other Ca-Ti-containing compounds such as lime addition, content and distribution state of TiO2 in bauxite, digestion temperature and retention time were studied.

Effects of element additions on the microstructure and mechanical properties of Al-Si-Cu filler metals

For the development of a Iow-melting-point filler metal for brazing aluminum alloys, a series of Al-Si-Cu-（ Ni, Sn, Zn ） filler metals have been studied. Through differential thermal analysis （DTA）, the melting temperatures of such Al-Si-Cu- （ Ni, Sn, Zn） filler metals were determined. The results show that the addition of 3 wt. % - 5 wt. % Sn into the Al-6Si-15Cu filler metal causes its solidus temperature to decrease by about 12℃. The filler metal with the composition Al-6Si-15Cu-2Ni is proposed, which possesses a melting temperature range of 512℃ to 520℃ and a microstrueture that includes an Al-Cu eutectic phases, Al-Si-Cu eutectic phases, silicon particles and Cu2Al, AlNi3 , Al7 Cu4Ni and Al3Ni2 intermetallic compounds. An addition of 5 wt. % -7 wt. % Zn into such A1-Si-Cu filler metals cause their solidus temperatures to drop further to a value lower than 498℃. Metallographic observations indicate that the addition of Zn into the Al-Si-Cu filler metal inhibits the formation of the Al-Si, Al-Cu and Al-Si-Cu eutectic phases. The remaining phases are a A12 Cu intermetallic compound, an α- Al solid solution and silicon particles.

EQUILIBRIUM PHASE DIAGRAMS IN SYSTEM CuO-PbO-Ag

Phase equilibrium in the ternary CuO-PbO-Ag system has been investigated using differential thermal analysis(DTA),thermogravimetry(TG),scanning electron microscopy(SEM) and X-ray diffraction(XRD) techniques.In the ternary CuO-PbO-Ag system,there is a eutectic reaction CuO+PbO+Ag=L at 750℃ and a composition of 12.04 mol.% Ag,16.35 mol.% CuO and 71.61 mol.% PbO.Two miscibility gaps near the two binary tie lines PbO-Ag and CuO-Ag were detected. No binary or ternary compound was detected in the ternary system.SEM and energy dispersive spectroscopy(EDS) confirm the presence of two liquid phases and the eutectic point.

Thermal stability and frequency up-conversion properties of Er^(3+)-doped oxyfluoride tellurite glasses

The thermal properties of 68TeO2-15BaF2-5SrF2-10LaF3-2KF glass were measured by different temperature analysis （DTA）. Up-conversion luminesceuce of Er^3＋ ion in the obtained glass was investigated. Mechanism of up-conversion emission was discussed. The result shows that the obtained oxvfluoride tellurite glass 68TeO2-15BaF2-5SrF2-10LaF3-2KF has a good thermal stability （ΔT = 153.6 ℃） and strong up-conversion green emissions around 527 nm and 549 nm and red emission at 660 nm. This glass can be a promising host material for up-conversion fiber lasers.

Effect of Sm^+ Rare Earth Ion on the Structural,Thermal,Mechanical and Optical Properties of Potassium Hydrogen Phthalate Single Crystals

Rare earth Sm＋ ion doped potassium hydrogen phthalate （KHP） single crystal was grown by slow evaporation technique. Single crystal and powder X-ray diffraction analyses confirm the crystalline perfection of Sm＋ ion doped KHP crystal. The functional groups of pure and Sm＋ ion doped KHP crystals were identified by Fourier transform infrared spectroscopy （FTIR） spectral studies. Thermogravimetric and differential thermal analyses were carried out to study the thermal behavior of the grown crystals. UV-Vis studies explored the optical transmittance of the grown crystals in the entire visible region. The mechanical strength and etching studies were performed to assess the perfection of the pure and Sm＋ ion doped KHP crystals. The refractive index and birefringence properties of the grown crystal were analyzed. The second harmonic generation efficiency of Sm＋ ion doped KHP crystals was observed by Kurtz-Perry powder test.

Solidification Studies of 3003 Aluminium Alloys with Cu and Zr Additions

The effects of Cu and Zr additions, on the microstructure formation, precipitation and ingot cracking, in commercial 3003 Al alloys have been studied. The investigation was carried out by characterizing the grain structure in DC-cast rolling ingots, and studying the solidification microstructure of Bridgman directionally solidified samples. To better understand the influence of the different Cu and Zr contents on the phase precipitations, differential thermal analysis （DTA） experiments were performed. Results from the ingot microstructure analysis show that in commercial alloys with relatively high contents of Cu and Zr, no significant differences in measured grain sizes compared to conventional 3003 Al alloys could be found. However, only Zr containing alloys exhibited significantly larger grain sizes. Increased grain refiner and/or titanium additions could compensate for the negative effects on nucleation normally following Zr alloying. Different types of precipitates were observed. Based on DTA experiments, increased Cu and Zr contents resulted in the formation of Al2Cu phase, and increased solidification range. It was also found that increased Mn content favors an early precipitation of Al6（Mn,Fe） giving relatively coarse precipitates. It was concluded that the Cu alloying has a detrimental effect on hot tearing.

Effect of nanocrystals on up-conversion luminescence of Er^(3+),Yb^(3+) co-doped glass-ceramics

Different up-conversion luminescent spectra of Er^3＋ ions were observed in the oxyfluoride glass-ceramics. The ratio of two fluorides in the original compositions was modified in order to form different nanocrystals. The intensity of up-conversion luminescence increased sharply when the ratio of PbF2 and CdF2 was 40：10. The data of differential thermal analysis and X-ray diffraction were used to explain the optimization fluoride ratio. The intensity of up-conversion luminescence is not only decided by the crystallizability but also mainly related with the stoiehiometric proportion of fluoride nanocrystals in the glass-ceramics.

Effect of High Magnetic Field on Nucleation and Growth of Primary Phase in Hypoeutectic Binary Alloys

The nucleation and growth behaviors of primary Al phase in two hypoeutectic binary alloys of A1-20.8%Cu and Al-3%Ni in high static magnetic fields were investigated with aid of differential thermal analysis(DTA).The DTA curves indicated that the nucleation temperature of primary crystals in two alloys decreased with increase of the magnetic field intensity and their nucleation was retarded in the magnetic field.The dendrite morphology showed that primary dendrites grew from disorderly without the magnetic field to regularly with the field.The retardation of nucleation of primary Al crystals was mainly caused by increase of interracial free energy.The change in dendrite morphology could be attributed to suppression of melt flows in the magnetic field.