Particle Size Distribution,Powder Agglomerates and Their Effects on Sinterability of Ultrafine Alumina Powders

An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.

Sinterability of Zirconia Top Coat of Investment Mold for Ti Alloy

In this paper. zirconia is used as top mold material for Ti investment casting. Top mold samples are made by proper mold building technology. The effect of different sintering temperature on chemical composition, microstructure and residual bending strength of the top mold sample is Studied. The volume and homogeneity of the air holes in the top mold are determined by sintering temperature. and finally determined the residual bending strength of the mold sample was determined.

SINTERABILITY EXPERIMENTS OF PORTAND CEMENT WITH IRON-TAILINGS AS RAW MATERIALS

The sinterability of Portland Cement with iron tailings as raw materials are studied. Experimental results showed that iron tailings, owing to the existences of the trace elements, play an important role in improving the sinterability of the raw meals and decreasing the calcination temperature.

Effect of TiO_2 on the Sinterability and Microstructure of Mullite Sythesized from Al(OH)_3 and SiO_2

Using analytical pure Al（ OH）3 , SiO2 , TiO2 as raw materials, effect of TiO2 on the sinterability and microstructure of mullite synthesized from Al （ OH）3 and SiO2 was investigated in this paper by XRD , SEM and EPAX. Results show that TiO2 can promote the sintering property when the amount is below 6%, the sinterability of samples becomes better with the increase of the amount of TiO2, microstructure of samples densify gradually, and the best effect can be achieved when the amount of TiO2 is 6%. It was shown by XRD analysis that no Al2TiO5 present when the amount of TiO2 is below 6%, TiO2 existed in the form of solid-solution and glass phase; When the amount of TiO2 is up to 6%, the sinterability of samples becomes worse with the increase of TiO2 added, microstructure of samples began to loosen, Al2TiO5 can be observed in samples and its amount increase with the increase of TiO2.

DEPENDENCE OF SINTERABILITY ON STATE OF AGGLOMERATION OF ULTRAFINE ZrO_2，（Y_2O_3） POWDERS

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Improvement of True Green Porosity, Sinterability and Microstructure in Alumina Ceramics by Filter Pressing

Comparison between filter pressing and isostatic pressing for submicrometer alumina powder has been systematically made. Obvious improvements in true porosity, sintering behaviour, and microstructure of green compacts without cracking and in agglomeration of final ceramics have been achieved.

Particle Size Control, Sinterability and Piezoelectric Properties of BaTiO₃Prepared by a Novel Composite-Hydroxide-Mediated Approach

The size of BaTiO3 particles was controlled by adjusting the molar ratio of the starting materials (BaCl2 + TiO2) to mineralizer (NaOH + KOH) during a composite-hydroxide-mediated approach using a novel hydrothermal reaction apparatus with a rolling system. The mean particle diameter decreased from 500 to 50 nm with a decrease in the (BaCl2 + TiO2)/(NaOH + KOH) molar ratio from 0.44 to 0.04. The powders were sintered by normal one-step sintering at 1200°C for 5 h and two-step sintering in which temperature was raised to 1200°C at first and then decreased to 1100°C and kept at 1100°C for 5 h. The BaTiO3 particles prepared with the (BaCl2 + TiO2)/(NaOH + KOH) molar ratio of 0.32 and 0.22 showed excellent sinterability and could be sintered to almost full theoretical density by both method. The sintered bodies obtained by both methods showed similarly excellent dielectric and piezoelectric properties.

Rare-earth Cerium Additives for Sinterability of Anorthite-Diopside Ceramics

Anorthite -diopside ceramics were prepared by sintering iron ore railings, calcium carbonate, and silicon dioxide. Rare-earth cerium nitrate was evaluated as a sintering additive for the ceramics, whose mass percentage was 3% , 5%, 7% , 9% , and 11% , respectively. The sinterability of anorthite - diopside ceramics during heat treatment was confirmed hy X-ray diffiaction, transmission^scanning electron micrascopy, thermogravi- metric analysis- differential thermal analysis, and hotstage microscopy, respectively. The obtained results show that the density of ceramics gradnally increases, while the sintering temperature and sintering activation energy of anorthite -diopside ceramics are notably decreased with the increasing cerium content. Rare-earth cerium not only is beneficial to the complete reaction of raw materials, but a/so can accelerate the mass transfer process through forming eutectic phase with aluminum.

A Comparison Study of Sinterability and Electrical Properties for Microwave and Conventional Sintered Mn_(0.43)Ni_(0.9)CuFe_(0.67)O_4 Ceramics

In this paper, a quaternary system of Mn0.43Ni0.9CuFe0.67O4 negative temperature coefficient （NTC） thermistor ceramic prepared by solid/solid reaction was sintered by microwave and conventional method, respectively. To characterize the sinterability of the samples, the densification parameter, porosity and grain size distribution of the bulk were determined. The crystal structure, phase compositions, morphology and impedance of the samples were analyzed by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, energy-dispersive spectroscopy （EDS） and impedance analysis. The experimental results confirmed that the sinterability and electrical properties of ceramics were homogenously improved by microwave sintering.

Prediction and optimization of flue pressure in sintering process based on SHAP

Sinter is the core raw material for blast furnaces.Flue pressure,which is an important state parameter,affects sinter quality.In this paper,flue pressure prediction and optimization were studied based on the shapley additive explanation(SHAP)to predict the flue pressure and take targeted adjustment measures.First,the sintering process data were collected and processed.A flue pressure prediction model was then constructed after comparing different feature selection methods and model algorithms using SHAP+extremely random-ized trees(ET).The prediction accuracy of the model within the error range of±0.25 kPa was 92.63%.SHAP analysis was employed to improve the interpretability of the prediction model.The effects of various sintering operation parameters on flue pressure,the relation-ship between the numerical range of key operation parameters and flue pressure,the effect of operation parameter combinations on flue pressure,and the prediction process of the flue pressure prediction model on a single sample were analyzed.A flue pressure optimization module was also constructed and analyzed when the prediction satisfied the judgment conditions.The operating parameter combination was then pushed.The flue pressure was increased by 5.87%during the verification process,achieving a good optimization effect.

Oxidation Resistance of Form-stable Hightemperature Phase Change Thermal Energy Storage Materials Doped by Impregnated Graphite

We adopted the solution impregnation route with aluminum dihydrogen phosphate solution as liquid medium for effective surface modification on graphite substrate.The mass ratio of graphite to Al(H_(2)PO_(4))_(3) changed from 0.5:1 to 4:1,and the impregnation time changed from 1 to 7 h.The typical composite phase change thermal storage materials doped with the as-treated graphite were fabricated using form-stable technique.To investigate the oxidation and anti-oxidation behavior of the impregnated graphite at high temperatures,the samples were put into a muffle furnace for a cyclic heat test.Based on SEM,EDS,DSC techniques,analyses on the impregnated technique suggested an optimized processing conditions of a 3 h impregnation time with the ratio of graphite:Al(H_(2)PO_(4))_(3) as 1:3 for graphite impregnation treatment.Further investigations on high-temperature phase change heat storage materials doped by the treated graphite suggested excellent oxidation resistance and thermal cycling performance.

Sinterability of nanopowders of terbia solid solutions with scandia,yttria,and lutetia

The synthesis of nanopowders of terbia compounds with scandia, yttria, and lutetia was carried out using a self-propagating high-temperature synthesis method involving a mixture of nitrates of metals and glycine as a precursor. The nanopowder phase transformations were investigated using X-ray diffraction analysis. It was found that lutetia has a negligible effect on the phase formation in terbia. On the other hand, yttrium and scandium ions significantly suppressed crystallization. The densification kinetics of nanopowders of the Tb_2O_3 compounds and the microstructure of ceramics after microwave sintering were studied using dilatometry and scanning electron microscopy. The introduction of scandia, yttria, or lutetia contributed to the intensification of the densification of the terbia ceramics when heated in a microwave field. Near full-density materials of terbia solid solutions with lutetia and yttria were obtained at about 1600–1640 ℃. The ceramics of scandia–terbia compounds contained the second phase, which causes light scattering.

High-entropy carbide-nitrides with enhanced toughness and sinterability

High-entropy ceramics (HECs) have attracted much attention due to their huge composition space,unique microstructure,and desirable properties.In contrast to previous studies,which have primarily focused on HECs with one anion,herein,we report a new family of ceramics with both multi-cationic and-anionic structures,i.e.,high-entropy carbide-nitrides (Ti0.33Zr0.33Hf0.33)(C0.5N0.5),(Ti0.25Zr0.25Hf0.25-Nb0.25)(C0.5N0.5) and (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)(C0.5N0.5).These as-synthesized HECs are mainly comprised of a face-centered cubic solid-solution phase accompanied by minor inevitable oxide phases.The formation mechanism of the solid-solution phase is discussed in terms of the lattice size difference and thermodynamic competition between configurational entropy and mixing enthalpy.It is found that the increment in the configurational entropy can effectively lower the sintering temperature and increase the fracture toughness.Particularly,the newly developed (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)(C0.5N0.5) exhibits a decent fracture toughness of 8.4 MPa m1/2and a low sintering temperature of 1750°C,making it promising for ultra-high temperature applications.Our work not only enriches knowledge regarding the HECs categories,but also opens a new pathway for developing HECs with multi-cationic and-anionic structures.

Particle size dependent sinterability and magnetic properties of recycled HDDR Nd-Fe-B powders consolidated with spark plasma sintering

The dependence of the magnetic properties on the particle size of recycled HDDR Nd-Fe-B powders was investigated,with the aim to assess the reprocessing potential of the end-of-life scrap magnets via spark plasma sintering(SPS).The as received recycled HDDR powder has coercivity(Hci)=830 kA/m and particles in the range from 30 to 700 μm(average 220 μm).After burr milling,the average particle size is reduced to 120 μm and subsequently the Hci of fine(milled) powder was 595 kA/m.Spark plasma sintering was exploited to consolidate the nanograined HDDR powders and limit the abnormal grain coarsening.The optimal SPS-ing of coarse HDDR powder at 750℃for 1 min produces fully dense magnets with Hci=950±100 kA/m which further increases to 1200 kA/m via thermal treatment at 750℃for 15 min.The burr milled fine HDDR powder under similar SPS conditions and after thermal treatment results in Hci=940 kA/m.The fine powder is further sieved down from 630 to less than 50 μm mesh size,to evaluate the possible reduction in Hci in relation to the particle size.The gain in oxygen content doubles for <50 μm sized particles as compared with coarser fractions(>200 μm).The XRD analysis for fractionated powder indicates an increase in Nd2O3 phase peaks in the finer(<100 μm)fractions.Similarly,the Hci reduces from 820 kA/m in the coarse particles(>200 μm) to 460 kA/m in the fine sized particles(<100μm).SPS was done on each HDDR powder fraction under the optimal conditions to measure the variation in Hci and density.The Hci of SPS-ed coarse fraction(>200 μm) is higher than 930 kA/m and it falls abruptly to just 70 kA/m for the fine sized particles(<100 μm).The thermal treatment further improves the Hci to>1000 kA/m only up to 100 μm sized fractions with>90% sintered density.The full densification(>99%) is observed only in the coarse fractions.The loss of coercivity and lack of sinterability in the fine sized particles(<100 μm) are attributed to a very high oxygen content.This implies that during recycling,if good magnetic properties are to be maintained or even increase the HDDR powder particles can be sized down only up to≥100 μm.

Effect of mechanical alloying on sinterability and phase evolution in pressure-less sintered TiB_(2)-TiC ceramics

Phase relation and microstructure evolution in the pressure-less sintered TiB_(2)‒TiC ceramics preceded with mechanical alloying were systematically studied by a combination of SEM analysis.WC debris from milling balls promotes sintering by dissolving into the TiC phase to achieve dense microstructures at 1600℃.Variation of W solution in TiC grains exposes two types of core-rim structures,with no or more W in dark and white cores respectively but with common medium W in both rims.Diminishing whitecores reveal an exchange reaction between WC and TiC via mechanical alloying to form the Ti_(1-z)W_(z)C phase prior to sintering.The dark-cores inherit from the as-milled TiC power to further enable the reprecipitation of rims from a mixed liquid-phase,which facilitated also the anisotropic growth of TiB_(2) grains.The dark-cores grow persistently in the second-step at 2000℃ enabled by this liquid-phase,which coarsens the TiB2 grains too.With more alloyed phase,sintering was insufficient at 1500℃ with only the surface fluidity from the primary powders,and the second-step sintering increased the fluidity in the liquid-phase to fully densify the binary microstructure.Re-distribution of the alloyed W by two-step sintering rationalizes the evolution process of the binary microstructures and leads to better understanding of the mechanical behaviors.

Unveiling exceptional sinterability of ultrafine a-Al2O_(3) nanopowders

Scalable pressureless sintering of nanocrystalline alumina(Al2O_(3))ceramics is a challenging problem with great scientific and technological interest.This challenge was addressed in our recent works utilizing ultrafine a-Al2O_(3) nanopowders with exceptional sinterability combined with two-step sintering technique.Here the sintering mechanism and kinetic parameters(grain boundary diffusivity and its activation energy)were analyzed from constant heating-rate sintering experiments by three different sintering models and compared with existing sintering data in the literature.We found that the lowtemperature sintering of 4.7 nm a-Al2O_(3) nanopowders can be well explained by conventional sintering mechanism via grain boundary diffusion,with reasonable activation energy of 4e5 eV that is smaller than that of coarse Al2O_(3) powders and enhanced diffusivity.However,unphysically small activation energy could be obtained if an inappropriate model was used.Lastly,successful two-step sintering was demonstrated under different heating rates.Our work illustrates that the exceptional sinterability of ultrafine a-Al2O_(3) nanopowders are most likely contributed by small size(short diffusion distance),large surface area(large sintering driving force)and good dispersity rather than new sintering mechanism,and highlights the importance of fast firing and the non-equilibrium nature for the low-temperature sintering of such nanopowders.

Relationship between Atmospheric Dew Point and Sinterability of Al-Si Based Alloy

Al-Si based alloys are interestingly used to produce automotive components. Fabrication of such components by powder metallurgy （PM） has been developed continuously. During PM, several parameters affect the sinterability of the aluminium powder, including atmospheric dew point which is regarded as one of the crucial parameters. The objective of this work was to investigate the effect of the atmospheric dew point on the sinterability of AI-14.9Si-2.4Cu-0.55Mg by studying the sintering characters obtained under various atmospheric dew points. The aluminium alloy powder was pressed into tensile specimens and subsequently sintered in a nitrogen atmosphere at 560 ℃ for 60 min with varied atmospheric dew points. The results show that as the dew point decreased, the sintered properties were improved. The atmospheric dew point of -38.4 ℃ is sufficient to obtain good sintering characters and it is achievable in a commercial furnace.

Recent developments in selective laser processes for wearable devices

Recently,the increasing interest in wearable technology for personal healthcare and smart virtual/augmented reality applications has led to the development of facile fabrication methods.Lasers have long been used to develop original solutions to such challenging technological problems due to their remote,sterile,rapid,and site-selective processing of materials.In this review,recent developments in relevant laser processes are summarized under two separate categories.First,transformative approaches,such as for laser-induced graphene,are introduced.In addition to design optimization and the alteration of a native substrate,the latest advances under a transformative approach now enable more complex material compositions and multilayer device configurations through the simultaneous transformation of heterogeneous precursors,or the sequential addition of functional layers coupled with other electronic elements.In addition,the more conventional laser techniques,such as ablation,sintering,and synthesis,can still be used to enhance the functionality of an entire system through the expansion of applicable materials and the adoption of new mechanisms.Later,various wearable device components developed through the corresponding laser processes are discussed,with an emphasis on chemical/physical sensors and energy devices.In addition,special attention is given to applications that use multiple laser sources or processes,which lay the foundation for the all-laser fabrication of wearable devices.

Physical,mechanical and thermal properties of vacuum sintered HUST-1 lunar regolith simulant

Establishing a base on the Moon is one of the new goals of human lunar exploration in recent years.Sintered lunar regolith is one of the most potential building materials for lunar bases.The physical,mechanical and thermal properties of sintered lunar regolith are vital performance indices for the structural design of a lunar base and analysis of many critical mechanical and thermal issues.In this study,the HUST-1 lunar regolith simulant(HLRS)was sintered at 1030,1040,1050,1060,1070,and 1080℃.The effect of sintering temperature on the compressive strength was investigated,and the exact value of the optimum vacuum sintering temperature was determined between 1040 and 1060℃.Then,the microstructure and material composition of vacuum sintered HLRS at different temperatures were characterized.It was found that the sintering temperature has no significant effect on the mineral composition in the temperature range of 1030-1080℃.Besides,the heat capacity,thermal conductivity,and coefficient of thermal expansion(CTE)of vacuum sintered HLRS at different temperatures were investigated.Specific heat capacity of sintered samples increases with the increase of test temperature within the temperature range from-75 to 145℃.Besides,the thermal conductivity of the sintered sample is proportional to density.Finally,the two temperatures of 1040 and 1050℃were selected for a more detailed study of mechanical properties.The results showed that compressive strength of sintered sample is much higher than tensile strength.This study reveals the effects of sintering temperature on the physical,mechanical and thermal properties of vacuum sintered HLRS,and these material parameters will provide support for the construction of future lunar bases.

Towards the insights into the deactivation behavior of acetylene hydrogenation catalyst

A series of model catalysts were obtained by treating commercial fresh and spent catalysts unloaded from the factory with different methods, including green oil dipping, extraction and high-temperature regeneration;finally, the deactivation behavior of the commercial catalyst for acetylene hydrogenation were studied. The influence of various possible deactivation factors on the catalytic performance was elucidated via detailed structural characterization, surface composition analysis, and activity evaluation.The results showed that green oil, carbon deposit and sintering of active metal were the main reasons for deactivation, among which green oil and carbon deposit led to rapid deactivation, while the activity could be recovered after regeneration by high-temperature calcination. The sintering of active metal components was attributed to the high-temperature regeneration in hydrothermal conditions, which was slow but irreversible and accounted for permanent deactivation. Thus, optimizing the regeneration is expected to extend the service life of the commercial catalyst.