Industrial growth of yttria-stabilized cubic zirconia crystals by skull melting process

We reported the development of a Ф100 cm growth apparatus for skull melting growth of yttria-stabilized cubic zirconia(YSZ) crystals and more than 1000 kg crystals have been grown in the furnace each time.The growth conditions were optimized and the structure of the as-grown crystals was characterized by X-ray diffraction.The transmittance of 15 mol.% yttria-stabilized cubic zirconia crystal was nearly 80% in the range of 400–1600 nm.The refractive indices were measured and fitted the Sellmeier equation whi...

Transition of Y_2BaCuO_5 Phase in Powder Melting Processed YBa_2Cu_3O_(7-x) Superconductors

The morphology and the formation of Y2BaCuO5 phase in powder melting processed YBa2Cu3O7-x superconductors were investigated. The experimental results show the heat treatment can not change the shape of Y2BaCuO5 particles in powder melting processed samples. The formation of round Y2BaCuO5 phase is due to relative content of each constitution of precursor powders in powder melting process. For powder melting process, the excessive liquid phase is eliminated, which restrains the preferred growth of Y2BaCuO5 particles.

NUMERICAL SIMULATION OF TRANSIENT THERMAL FIELD IN LASER MELTING PROCESS

Numerical simulation of thermal field was studied in laser processing. The 3-D finite element model of transient thermal calculation is given by thermal conductive equation. The effects of phase transformation latent are considered. Numerical example is given to verify the model. Finally the real example of transient thermal field is given.

Solute Redistribution in Directional Melting Process

The solute redistribution in directional melting process is theoretically studied. Based on quantitative evaluations, uniform.solute distribution in liquid and a quasi-steady solute distribution in solid are supposed. The discussion on the solute balance comes to a simple model for the solute redistribution in directional melting process. As an example, the variation of liquid composition during melting process of carbon steel is quantitatively evaluated using the model. Results show that the melting of an alloy starts at solidus temperature, but approaches the liquidus temperature after a very short transient process.

Experimental Study on the Molten Salt at Micron Scale during the Melting Process

The investigation of the melting behaviors of the molten salt at micron scale during the melting process is critical for explaining the solid-liquid phase transition mechanism.In this paper,a novel experimental system and analysis method were proposed to study the melting process with three heating rates in the range of1-10℃/min of the solar salt at micron scale.The solid-liquid boundary morphology and phase transition kinetics of molten salt particles were focused on.Meanwhile,the correlations between liquid fraction,temperature and time under different heating rates were studied.The solid-liquid boundary morphology was depicted by the visualized experimental set-up,and the instantaneous liquid volume fraction during the non-isothermal phase transition was obtained.Then,the correlation between temperature and liquid volume fraction was proposed to reveal the evolution of the solid-liquid boundary with temperature at different heating rates.Furthermore,the non-isothermal phase transition kinetic equation was established by introducing a constant parameter(V_(a,b)),and more kinetic parameters such as 1g V_(a,b) and-lg V_(a,b)/b were studied.The results showed that the exponent b is not sensitive to the heating rate with a range of 3-5 for solar salt particles.However,the heating rate influences the value of V_(a,b) and presents a positive relationship.Besides,the non-isothermal phase transition kinetic equations at different heating rates in the range of 1-10℃/min can be quickly predicted by the proposed improved experimental test method.This study could fill the research insufficiency and provide significant guidance for future research on the solid-liquid transition mechanism of molten salts at micron scale.

Carbonaceous matter in glacier at the headwaters of the Yangtze River:Concentration,sources and fractionation during the melting process

Carbonaceous matter has an important impact on glacial retreat in the Tibetan Plateau,further affecting the water resource supply.However,the related studies on carbonaceous matter are still scarce in Geladaindong(GLDD)region,the source of the Yangtze River.Therefore,the concentration,source and variations of carbonaceous matter at Ganglongjiama(GLJM)glacier in GLDD region were investigated during the melting period in 2017,which could deepen our understanding on carbonaceous matter contribution to glacier melting.The results showed that dissolved organic carbon(DOC)concentration of snowpit samples(283±200μg/L)was much lower than that of precipitation samples(624±361μg/L),indicating that large parts of DOC could be rapidly leached from the snowpit during the melting process.In contrast,refractory black carbon(rBC)concentration measured by Single Particle Soot Photometer of snowpit samples(4.27±3.15μg/L)was much higher than that of precipitation samples(0.97±0.49μg/L).Similarly,DOC with high mass absorption cross-section measured at 365 nm value was also likely to enrich in snowpit during the melting process.In addition,it was found that both r BC and DOC with high light-absorbing ability began to leach from the snowpit when melting process became stronger.Therefore,rBC and DOC with high light-absorbing ability exhibited similar behavior during the melting process.Based on relationship among DOC,rBC and K^+ in precipitation,the main source of carbonaceous matter in GLJM glacier was biomass burning during the study period.

Effects of compressing and remelting in SIMA processing on semi-solid structure evolution of an Al-Zn wrought alloy

Structure evolution of an Al-Zn wrought alloy in remelting processing in thestrain induced melt activated (SIMA) serai-solid procedure was observed, and effects of factors, theremelting temperature, the holding time, and the compression strain, on structures and grain sizesof the alloy were investigated. The results show that (1) the proper temperature of remelting is inthe range of 610 to 615℃; (2) the grain size in specimen with greater compression strain is smallerthan that with smaller compression strain in condition of the same remelting temperature andholding time, and the grain size in local area with great local equivalent strain is smaller thanthat with small one; (3) liquid occurs in form of cluster in matrix during remelting and itsquantity increases with remelting time increasing; liquid in specimen with great compression strainoccurs earlier than that with small one, and quantity of liquid in the center of specimen withgreater local equivalent strain is greater than that in the two ends of it; (4) distortion energyafter deforming in matrix of the alloy is the significant factor to activate melting of matrix atlocal area with great local equivalent strain.

Numerical prediction of the incremental melting and solidification process

A mathematical formulation is applied to represent the phenomena in theincremental melting and solidification process (IMSP), and the temperature and electromagneticfields and the depth of steel liquid phase are calculated by a finite difference technique using thecontrol volume method. The result shows that the predicted values are in good agreement with theobservations. In accordance with the calculated values for different kinds of materials anddifferent size of molds, the technological parameter of the IMS process such as the power supply andthe descending speed rate can be determined.

TiAl ALLOYS FOR INDUSTRIAL USE

Gamma titanium aluminide (γ-TiAl)intermetallic compounds are spotlighted as lightweight heat-resistant materials, and have been investigated extensively to aiming commercial use.Fundamental approaches in which phase diagrams of Ti -Al -Cr and TiAl -Nb have been studied based on the experimental data and calculations , have been performed in the national project For industrial approach, ingot process and direct casting process have been developed to provide sheet form of TiAl. By these approaches, γ-TiAl base ,intermetallic compounds show a great possibility to apply in the variety of fields .However, a more detailed understanding of phase equilibrium in Ti-Al -X and the relationship between the mechanical properties and microstructure will be necessary

Miscibility of Poly(hydroxybutyrate)/Poly(vinyl alcohol)Melt Blends Plasticized With Glycerol

Poly(hydroxybutyrate)/poly(vinyl alcohol)(PHB/PVA)blends plasticized with glycerol were prepared by melt blending of PHB and glycerol plasticized PVA.The PHB/PVA-glycerol compositions were 90:10,75:25 and 50:50 w/w,being the concentration of glycerol in the PVA mixture of 10 wt%.The blends were characterized by infrared spectroscopy,dynamic-mechanical thermal analysis,and scanning electron microscope of the fragile fractured surface.The results showed one single phase blend,indicating miscibility corroborated by the presence of a single glass transition temperature.The blending method proved to be an efficient way to tune PHB properties keeping its biodegradable nature since both PVA and glycerol are fully biodegradable materials.

Fabrication and Properties of (Y,Gd)BCO Superconductors

The microstructures and superconducting properties of melt textured(Y_(1-x)Gd_x)BCO bulk samples were studied. It was found that the peritectic decomposition temperature(T_m)of(Y_(1-x)Gd_x)BCO samples increases with increasing x. Large single domain growth in air is readily obtained in all the composites. The results of X-ray distribution maps of x=0.4 composite indicate that the RE123 matrix is homogeneous and Y and Gd elements in the RE site forms a perfect solid solution. The onset T_c values exceeding 91 K with relatively broad transitions are obtained for almost all the samples. Magnetization measurements show no marked indication for the formation of a peak effect in the J_c-B curves, and the highest J_c measured is 3.08×10~4 A·cm^(-2) for x=0.4 sample at 77 K and self-field. The results clearly indicate that Y dominates the superconducting properties of x=0.2 and (0.4) composites.

Effects of strain-induced melt activation treatment on the microstructure and properties of Zn sacrificial anodes

The microstructural properties and electrochemical performance of zinc(Zn)sacrificial anodes during strain-induced melt activation(SIMA)were investigated in this study.The samples were subjected to a compressive ratio of 20%-50% at various temperatures(425-435℃)and durations(5-30 min).Short-term electrochemical tests(anode tests)based on DNV-RP-B401 and potentiodynamic polarization tests were performed in 3.5wt%NaCl solution to evaluate the electrochemical efficiency and corrosion behavior of the samples,respectively.The electrochemical test results for the optimum sample confirmed that the corrosion current density declined by 90% and the anode efficiency slightly decreased relative to that of the raw sample.Energy-dispersive X-ray spectroscopy,scanning electron microscopy,metallographic images,and microhardness profiles showed the accumulation of alloying elements on the boundary and the conversion of uniform corrosion into localized corrosion,hence the decrease of the Zn sacrificial anode’s efficiency after the SIMA process.

Biocomposites Based on Thermoplastic Starch and Granite Sand Quarry Waste

Granite stone is a by-product of the rock crushing manufacturing.An industrial waste in powder form that causes health problems and environmental pollution.Fine particles fraction can be used as a partial replacement of sand in concrete manufacture.In this work,an alternative exploitation of this waste fraction is proposed.Granite sand(GS)with particles mean size of ~1μm was employed as thermoplastic starch(TPS)filler at different concentrations.Biocomposites were obtained by melt-mixing and thermo-compression,achieving translucent and easy to handle films.A good GS dispersion within the matrix was evidenced by SEM.Mineral presence induced a shift of starch’s melting point to higher values and a better thermal resistance.TPS UV absorption capacity was increased ~90% by GS addition.An increment in TPS Young’s modulus and maximum tensile stress of 5 and 3 times,respectively was observed by adding 5%w/w GS.

Segregation behavior and its regulating process in as-cast magnesium alloy containing heavy rare earth

Specific gravity segregation that occurs during the smelting process always leads to the low composition homogeneity and poor performance stability of the magnesium-rare earth(Mg-RE)alloys.In this study,the segregation behavior of Mg-Gd alloy was investigated by sampling from different locations in the ingot fabricated in a resistance furnace without a pouring process.The combined application of induction-heating and mechanical stirring with various speeds(0-130 r/min)was applied to promote the distribution homogeneity of Gd atoms.In the resistance-heating fabricated ingot,Gd content at the bottom section reaches 407%of that at the top.The coarse dendrites surrounded by the network-like eutectic structures are responsible for the brittle fracture with a poor elongation of 3.7%.By the combined employment of the induction heating and mechanical stirring with the speed of 87 r/min at 740℃for 40 s,the variation of the Gd content within the whole ingot can be reduced to be the minimum of 0.23 wt%.Corresponding formation and regulating models of segregation were also proposed.However,the cooling rate of the melt is reduced by the continuous increase of the stirring speed to 130 r/min,which results in the grain coarsening and lower homogeneity of the ingot.

Simulations of Metal Cu in Heating Process

Based on the Finnis-Sinsclair (FS) many-body potential model, the melting process of a system, which consists of 500 Cu atoms, controlled by period boundary condition has been simulated. The means of pair correlation func-tion, mean square displacement and Honeycutt-Anderson bonded pair have been used to characterize the melting behavior of Cu at different heating rates. The simulation indicates that melting point of metal Cu is 1444 K during a continuous heating process, and the calculated diffusion constant at the melting point is 4.31×10-9 m2/s. These re-sults are better than those from the EAM method, showing that the FS potential model works well in some disor-dered systems.

Tailoring the Microstructure and Mechanical Property of Mg-Zn Matrix Composite via the Addition of Al Element

The semi-solid stir casting method is adopted to prepare 10 wt%SiC_(p)/Mg-6Zn-0.5Ca-xAl(x=0,1,3 and 5 wt%)composites,and the microstructure evolution and mechanical property of composites with various Al content are investigated.The results show that the addition of 3 wt%Al improves the distribution of SiC_(p),whereas the SiC_(p) cluster occurs again with Al content greater than 3%.An abnormal phenomenon of twinning is observed in the cast composites in this work.The SiC_(p)/Mg-6Zn-0.5Ca composite possesses the highest twin content of~23%,for which tension twins(TTW)and compression twins(CTW)account for~19%and~3%,respectively.The CTW is only observed in ZXA600 composite.The addition of Al has an inhibiting effect for the generation and growth of twins.The content of twin decreases firstly and then increases with increase of Al content.The lowest twin content is obtained as Al increases to 3 wt%.It is found the existence of twin is detrimental to the mechanical property of composites.As-cast SiC_(p)/Mg-6Zn-0.5Ca-3Al composite with the lowest twin content exhibits the optimal mechanical property of yield strength,ultimate tensile strength and elongation for 100 MPa,188 MPa and 4.4%,respectively.The outstanding mechanical property is attributed to the uniform distribution of SiC_(p),the low twin content and the well-distributed fine second phases.

Three-dimensional Mathematical Modeling of a Glass Melting System

An integral mathematical model has been developed to simulate the performance of a glass melting system.The heart of the model is a three dimensional flow and heat transfer model capable of calculating the glass flow and temperature distribution in the melt. The glass quality is predicted by using additional sub models for flow tracking, melting kinetics, homogenizing, refining, and refractory corrosion. A sample result is presented to illustrate the analysis of the glass melting process.

Melting/solidification of phase change material in a multi-tube heat exchanger in the presence of metal foam:effect of the geometrical configuration of tubes

One of the likely methods for enhancing heat transfer in a latent thermal energy storage system is the conception of a thermal unit.In this study,the orientation of oval tubes(horizontal,vertical,and oblique)in phase change material(PCM,C_(19)-C_(20))-based shell-tube heat exchanger was analyzed with respect to the metal foam(MF)type(graphite,copper,and nickel)in comparison to the case of pure PCM.For this purpose,a two-dimensional mathematical model was developed to investigate the thermal efficiency of the PCM-metal foam based composite energy storage unit.It was concluded that the orientation of the oval tubes(oblique,horizontal,and vertical)has a negligible impact on the performance of the thermal unit during the melting/solidification processes.Based on the liquid/solid fraction,total enthalpy and the average temperature in the annular space,the performance of a heat exchanger during fusion/solidification periods is in the order:copper-MF>graphite-MF>nickel-MF>pure PCM.Whatever the adopted MF or the geometry of tubes,the melting process is expedited compared to the solidification mechanism.

Thermal decomposition kinetics of titanium hydride and Al alloy melt foaming process

A temperature programmed decomposition (TPD) apparatus with metal tube struc- ture, in which Ar is used as the carrier gas, is established and the TPD spectrum of titanium hy- dride is acquired. Using consulting table method (CTM), spectrum superposition method (SSM) and differential spectrum technique, TPD spectrum of titanium hydride is separated and a set of thermal decomposition kinetics equations are acquired. According to these equations, the rela- tionship between decomposition quantity and time for titanium hydride at the temperature of 940 K is obtained and the result well coincides with the Al alloy melt foaming process.

Synthesis and Properties of Melt Processed Poly(thiourea-azo-sulfone)/Carbon Nanotubes Nanocomposites

An aromatic azo-polymer, poly（thiourea-azo-sulfone） （PTAS）, has been prepared using 4-（4- aminophenylsulfonyl）benzenamine and diazonium salt solution of 2,6odiaminopyridine. PTAS was easily processable using polar solvents and had high molar mass 63 × 103 g.mo1-1 according to GPC. Mechanically and thermally stable and electrically conducting polymer/CNTs nano-composites were obtained via melt processing technique. Fine distribution of CNTs in a polymer matrix performed an essential role in the preparation of polymer/CNTs nano-composites based on interfacial interaction between CNTs and polymer matrix. Scanning electron micrographs showed good dispersion of filler and adhesion of matrix on the surface of nanotubes. Accordingly, increasing the amount of CNTs from 0.1 wt% to 5 wt% increased the electrical conductivity from 2.99 S.cm-1 to 3.56 S.cm-1. Mechanical strength of functional nanotubes-based hybrids was enhanced from 43.22 MPa to 65.02 MPa compared with that of hybrids with non-functional filler in matrix 37.21 MPa. A rapport between nanotube loading and thermal stability of the materials was also observed. 10% gravimetric loss temperature was increased from 528 ~C to 578 ~C, while glass transition was improved from 241 ℃ to 271 ℃. Adding up of small quantity of functional CNTs strongly affected the tensile, electrical and thermal properties of materials. Improvement of the physical properties of CNT-reinforced polymer nano-composites was ascribed to the melt processing technique.