Sintering Heating Rate Research Articles

Light-weight high strength porous thermal insulation materials based on dolomite-granite waste

The first choice for the treatment of solid waste is its industrial utilization. Therefore, in the present study, dolomite tailings and granite waste are used as the basic raw materials, along with silicon carbide as a high-temperature foaming agent, to prepare a light-weight, high-closed porosity thermal insulation material. The effects of (i) the chemical compositions of the main raw materials and (ii) the relationship between the sintering process and the properties, microstructure and crystalline phase of the samples are systematically investigated. At the same time, the formation mechanism of high closed porosity of the thermal insulation material is analyzed. The results showed that when sintering temperature, time, and heating rate are 1200 °C, 30 min, and 3 °C/min, respectly, the sample density, compressive strength, true porosity, and closed porosity are 0.7 g/cm3, 6.62 MPa, 74.21%, and 66.36%, respectively. In addition, due to the high closed porosity, relative to traditional inorganic thermal insulation materials, the water absorption and thermal conductivity are significantly reduced to as little as 1.5%, and 0.30 W/(m·K), respectly. This research not only realizes the recovery and utilization of granite waste and dolomite tailings, but also provides a new prospect for energy saving and consumption reduction in the construction industry.

Effects of sintering parameters on the preparation and properties of foamed ceramics from cyanide tailings

ABSTRACT In this study, foamed ceramics were successfully prepared using cyanide tailings (CTs) with a high sulfur content as the main raw material. The effects of sintering temperature, holding time, and heating rate on the bulk density, water absorption, porosity, pore structure, and compressive strength of foamed ceramics were systematically investigated. The results showed that the elevated sintering temperature promoted the generation of liquid phases, resulting in an obvious enlargement of the pore size and a decrease in bulk density. In addition, a similar evolution trend could be found in the pore size and bulk density with the extension of the holding time, which was attributed to the degrees of silicon carbide reaction. Foamed ceramics with small pore sizes could be prepared at a heating rate that did not exceed 4°C/min. Then, the higher heating rates could bring abnormally large pores and be detrimental to the mechanical properties of the foamed ceramics, which were proven to be related to the decomposition of FeS2 introduced by CTs during the heating process. In conclusion, the foamed ceramics prepared with CTs in this study provide effective solid waste utilization and have good application prospects in wall composite one-piece insulation panels.

FEM Analysis on Thermo-mechanical behavior and experimental validation of Al20Cr20Fe25Ni25Mn10 High Entropy Alloy during Spark Plasma Sintering

High entropy alloy developed with spark plasma sintering was modelled with COMSOL Multiphysics. This focus at examining the effect of spark plasma sintering fabrication parameters on thermal and mechanical stress distribution in the sintered Al20Cr20Fe25Ni25Mn10 high entropy alloy (HEA). And to achieve this, a fully thermal-electrical-mechanical integrated and dynamic finite element model (FEM) was adopted. The simulation utilised the optimal parameters employed in the laboratory to produce the samples. The geometry for the modelling was 2D axisymmetric as the parameters were based on temperature-dependent characteristics noting that only the sintered sample was modelled and simulated in order not to simplify the modelling. The FEM maintained constant sintering temperature, pressure, and heating rate but concentrated on the impact of residence durations. To verify the simulation results, morphological alterations and densification validation tests were conducted. The microstructural characterization of the sintered sample demonstrated the relationship between the stress distribution and computational temperature found in the current FEM. Noting good particle-to-particle necking. From the model, results showed that the sintered sample at different points depicted a yield stress far greater than the von Mises stress with least thermal stress at 30 MPa. This validate that the developed sample is mechanically stable based on the factor of safety failure criterion and design. However, the study recommend that further work should be conducted considering different sintering pressure of variation 10 to 30 MPa.

Preparation and properties of lightweight and high-strength building ceramsites with oil-based drilling cuttings pyrolysis residues

With the continuing advancement in China’s exploration and development technologies of shale gas resources, there was a significant increase in shale gas oil-based drilling cuttings. In this paper, oil-based drilling cutting pyrolysis residues (ODCPRs) was used as the main raw material for preparing lightweight and high-strength building ceramsites to eliminate the environmental risks and recycle industrial waste. Firstly, orthogonal experiments were used to study the influences of raw material composition, preheating temperature, preheating time, sintering temperature, and sintering time on the properties of building ceramsites. From the results, the sintering temperature and the content of ODCPRs were discovered to be the key factors affecting the sintering process of ceramsites. Secondly, the influences of sintering temperature and heating rate on the properties of building ceramists were further explored to find the optimum sintering conditions. When the content of ODCPRs in the ceramsite was set to be 50%, the obtained building ceramsites presented excellent properties with particle compressive strength of 6.31 MPa, bulk density of 575.11 kg/m3, apparent density of 1097.24 kg/m3, and the water absorption of 1.89%. Finally, XRD, SEM, TG-DSC, and heavy metal leaching experiments were comprehensively conducted to analyze the composition structure variation and sintering mechanism of the building ceramsite. This paper presents an approach for the recycling, utilization, and disposal of oil-based drilling cuttings in the oil field waste management.

Experiment on preparation of porous glass-ceramics by inorganic gel casting from coal-based slag

Porous glass-ceramics have aroused extensive attention due to their thermal insulation and sound insulation properties. An emerging research focus is the utilization of solid waste as raw material for producing porous glass-ceramics. The inorganic gel casting method, involving alkali activation and mechanical stirring, has been proposed to achieve a hierarchical porous structure. In this study, porous glass-ceramics were fabricated using coal-based slag as the raw material through inorganic gel casting and the effects of the key parameters on the properties of porous glass-ceramics were revealed. Five key factors, namely the mass ratio of raw materials (A), gelation time (B), curing time (C), and sintering temperature (D), and heating rate (E), were identified as the design variables. The Taguchi method of L16 orthogonal array was employed to establish the mix proportions based on these design variables. Subsequently, the influences of these design variables on the microstructure of intermediate porous glass embryo, as well as the porosity and compressive strength of porous glass-ceramics, were analyzed. The results revealed the optimal parameter combination for gel generation as follows: a material mass ratio of 61:35:4 wt%, a gel time of 60 min, and a curing time of 36 h. The effects of these factors on pore structure and compressive strength followed the descending ranks of A > E > B > C > D and A > B > D > C > E, respectively. The maximum gel yield was reached at a mass ratio of 61:35:4 wt%, while the optimal pore structure was obtained at a mass ratio of 66:35:4 wt%. The sintering temperature exhibited minimal influence on the pore structure, whereas the sintering heating rate had minimal effect on the compressive strength. At a gelation time of 90 min and a curing time of 36 h, the porosity were exceeded 30%, and the pore size exhibited uniform distribution.

Production of lightweight foam ceramics by adjusting sintering time and heating rate

The heat treatment system was a key factor in the performance of lightweight foam ceramics. Phosphorus tailings and coal gangue were recovered for preparing lightweight foam ceramics by adjusting the sintering time and heating rate. The goal was to set a reasonable heat treatment regime for maximum optimized performance. The influences of sintering time and heating rate on the phase evolution, pore structure, physical properties and heavy metal solidification of lightweight foam ceramics were investigated by the results of XRD, SEM and ICP-MS examinations and theoretical calculations. As a result, extended sintering time promoted to formation glassy phase, which facilitated the average pore size growth from 34.88 µm to 124.23 µm. The larger heating rate (10 °C/min) prevented the vitrification of lightweight foam ceramics with an increase in water absorption (2.31 % − 23.14 %) and a decrease in compressive strength (9.80 MPa − 3.56 MPa). The lightweight foam ceramics exhibited relatively uniform pore structure, high porosity (61.79 %), low density (0.99 g/cm3), satisfactory compressive strength (10.08 MPa), and low water absorption (2.87 %) when they were treated at 1150 °C for 60 min with the heating rate of 5 °C/min. In particular, the extremely low leaching values of heavy metals and potential ecological risk index were detected for the lightweight foam ceramics. The fabricated lightweight foam ceramics satisfy the strength requirements of Chinese national standards for non-bearing building partitions and non-bearing bricks. This technology not only provided practical guidance for adjusting the sintering process to manufacture high-performance lightweight foam ceramics, but also the simultaneous high value-added utilization of phosphorus tailings and coal gangue could be achieved.

Parameter Optimization for Printing Barium Titanate Piezoelectric Ceramics through Digital Light Processing.

Digital light processing (DLP) technology has emerged as a promising 3D printing technology with the potential for the efficient manufacturing of complex ceramic devices. However, the quality of printed products is highly dependent on various process parameters, including slurry formulation, heat treatment process, and poling process. This paper optimizes the printing process with respect to these key parameters, such as using a ceramic slurry with 75 wt% powder content. The employed degreasing heating rate is 4 °C/min, the carbon-removing heating rate is 4 °C/min, and the sintering heating rate is 2 °C/min for heat treatment of the printed green body. The resulting parts are polarized using a poling field of 10 kV/cm, a poling time of 50 min, and a poling temperature of 60 °C, which yields a piezoelectric device with a high piezoelectric constant of 211 pC/N. To demonstrate the practical application of the device, its use as a force sensor and magnetic sensor is validated.

Optimization of process parameters for the development of Ni–Al-Ti-Mn-Co-Fe–Cr high entropy alloy system via spark plasma sintering

A novel equal atomic Ni–Al-Ti-Mn-Co-Fe–Cr high entropy alloy (HEA) was developed via the spark plasma sintering (SPS) process. This study investigates the influence of the sintering parametric processes, which consist of the sintering temperature (ST) and heating rate (HR) at constant pressure and dwelling time (DT) on the Microhardness (MH) and relative density (RD) of the developed HEA. Response surface methodology (RSM) was used to develop a predictive model. The design of experiment (DOE) approach was adopted to reduce the number of experiments and eliminate trial by error. ST and HR were considered model variables in developing the model. The user-defined design (UDD) under RSM was used to predict the optimal sintering parameters, and an experiment was conducted to validate the result. The result indicates that ST and HR play a significant role in achieving high densification and hardness. The developed alloy shows the highest MH value of 136.3 HV at 850 °C and an HR of 100 °C/min. Equally, the least crystallite size of 2.05 µm was realized at the maximum ST. However, the modeling response suggested that full densification of about 99% can be achieved at an ST of 850 °C, a pressure of 50 MPa, a DT of 5 min, and an HR of 100 °C/min.

Study on Sintering Behavior of Reaction-Cured Glass Coating

High-emissivity coatings constitute an essential component of reusable thermal protection systems, determining the success or failure of hypersonic spacecraft. Reaction-cured glass coating is the basis for all current high-emissivity coatings, and the study of its sintering behavior is of great scientific significance for the development and performance enhancement of the coating. Microstructures and phase compositions of the samples before and after the sintering process were determined using SEM, XRD, and EDS. The sintering temperature, inserting temperature, and heating rate were systematically investigated. The results show that the effects of the sintering temperature, inserting temperature, and heating rate on the coating occur in decreasing order. The optimum condition for coating sintering in this study is an insertion temperature of 1100 °C, a heating rate of 10 °C/min, and a sintering temperature of 1200 °C, and a crack-free and containing SiB4 borosilicate glass coating was successfully prepared.

Parametric study on conductive patterns by low-temperature sintering of micron silver ink.

The fabrication of dense conductive patterns was achieved by low-temperature sintering of 1-3 μm micron silver flakes. A small amount of 20-50 nm nanosilver particles were added in the gaps of the micron silver flakes. The effects of sintering temperature, holding time and heating rate on the morphological evolution and formation mechanism of the sintered silver pattern were investigated in detail. Interestingly, rapid sintering (RS) can be achieved by removing the heating process from 70 °C up to the sintering temperature. The electrical resistivity of the sintered silver patterns was 10.8 × 10-6 Ω cm at 140 °C for 30 min under a pressure of 10 MPa. Moreover, the electrical resistivity of the sintered silver pattern for RS for 20 min does not change significantly after 6000 bending cycles. This work provides a new method to fabricate conductive patterns using micron silver flakes with the purpose of promoting the application of silver inks.

INVESTIGATION OF THE EFFECT OF GRAIN SIZE ON THE DYNAMIC STRENGTH OF FINEGRAINED ALUMINUM OXIDE OBTAINED BY SPARK PLASMA SINTERING

The results of testing the dynamic strength of ceramic samples of aluminum oxide with different grain sizes are presented. Ceramics are obtained by electropulse plasma sintering (EPS) of industrial submicron and micron ?Al2O3 powders. Heating was carried out at a rate of 10 °C/min; The ceramic grain size was varied by changing the EPS temperature. The ceramics had a high relative density (more than 98%), a uniform finegrained microstructure, and the average grain size varied from 0.8 to 13.4 µm. The ceramic grain size was varied by changing the sintering temperature and heating rate, as well as by changing the initial particle size of the ?Al2O3 powder. Dynamic compression tests were carried out according to the modified Kolsky method, using a split Hopkinson rod. The tests were carried out using a gas gun with a caliber of 20 mm (PG20), at room temperature, with a deformation rate of ~ 103 s–1. It has been established for the first time that the dependence of the dynamic tensile strength of aluminum oxide on the grain size has a nonmonotonic character, with a maximum. The maximum value of the dynamic compressive strength (?Y = 1060 MPa) is provided with an average grain size of ~ 2.9–3 µm. It is shown that the decrease in ?Y of aluminum oxide in the region of submicron grain sizes is due to a decrease in the relative density of ceramics sintered at lower temperatures of SPS. It has been suggested that the decrease in ?Y of ceramics in the region of micron grain sizes is due to the formation of internal microstresses near the grain boundaries. It has been established that with an increase in the grain size, the hardness HV of aluminum oxide decreases, and the minimum Palmquist crack resistance coefficient KIC increases. The results obtained demonstrate that there is no need to ensure the formation of a nanostructure in ceramics to ensure high characteristics of their dynamic strength.

Evaluation of Mechanical Properties and Microstructure Depending on Sintering Heating Rate of IN 939W Alloy

Evaluation of Mechanical Properties and Microstructure Depending on Sintering Heating Rate of IN 939W Alloy

Ultrafast high-temperature sintering of dense and textured alumina

Crystallographic texture engineering in ceramics is essential to achieve direction-specific properties. Current texture engineering methods are time-consuming, energy extensive, or can lead to unnecessary diffusion of added dopants. Herein, we explore ultrafast high-temperature sintering (UHS) to prepare dense and textured alumina using templated grain growth (TGG). From a slurry containing alumina microplatelets coated with Fe3O4 nanoparticles dispersed in a matrix of alumina nanoparticles, green bodies with oriented microplatelets were prepared using magnetic assisted slip casting (MASC). The effects of the sintering temperature, time and heating rate on the density and microstructure of the obtained ceramics were then studied. We found that TGG occurs for a temperature range between 1640 and 1780 °C and 10 s sintering time. Sintering at 1700 °C for 10 s led to dense and textured alumina with anisotropic grains thanks to the Fe3O4 coating, which did not have the time to diffuse. The highest texture and relative density were obtained with a heating rate of ~5500 °C/min, leading to texture-dependent anisotropic mechanical properties. This study opens new avenues for fabricating textured ceramics in ultra-short times.

Development and performance study of biomedical porous zinc scaffold manufactured by using additive manufacturing and microwave sintering

ABSTRACT Zinc (Zn) and its alloys are gaining popularity day by day in biomedical applications due to their acceptable biocompatibility and moderate degradation rate than magnesium and iron. However, the fabrication procedure for the metallic scaffold is still a challenging task. Hence, the present study aims to establish a new manufacturing route for fabricating Zn scaffold utilizing 3D printing and microwave sintering. The Central composite design (CCD) methodology was used to investigate the influence of sintering parameters like sintering temperature (St), heating rate (Hr), and soaking duration (Sd) on the compressive strength (C.S) & sintered density (S.D) values of the fabricated sample. It was found that the value of C.S and S.D increased with an increase in soaking duration and heating rate. Similar to Hr and Sd, C.S and S.D values increased with increasing sintering temperature, but the values of both properties declined after a critical temperature. Multi-objective optimization was performed utilizing Genetic algorithm (GA) methodology, a tool of MATLAB to obtain the optimum values of process input factors for maximum C.S (18.6MPa) and S.D (6.79 gm/cm3). In the end, a comparative study of the Zn scaffold was performed to evaluate the performance of developed fabrication method, and results were found satisfactory.

Optimal parameters of microwave sintering process on nickel based composite

Microwave sintering process is the most economical and feasible technique to fabricate composite with superior quality of products. Nickel, aluminium and titanium alloy were reinforced with silicon carbide particles. The different microwave sintering constraints like sintering temperature, heating rate and hold time were considered to fabricate the composite. The fabricated specimens were processed under the evaluation of tensile strength and hardness properties. Taguchi approach was used to optimize the microwave sintering process factor. The parametric effect on tensile strength and hardness were analyzed through contour plot and variance analysis. Tensile strength of 360 MPa was attained at sintering temperature of 1400 °C, holding rate of 20 °C/min and holding time of 80 min. It was observed that sintering temperature has produced 87.01% of effect on tensile strength.

High Heating Rate Sintering of Copper-Chromium Core-Shell Powders Prepared by Physical Vapor Deposition

High Heating Rate Sintering of Copper-Chromium Core-Shell Powders Prepared by Physical Vapor Deposition

Microstructure and magnetic properties of nickel-zinc ferrite ceramics fabricated by spark plasma sintering

Dense nickel-zinc (NiZn) ferrite ceramics were successfully fabricated within tens of seconds via spark plasma sintering. The phase composition and microstructure of the sintered samples were characterized by X-ray diffraction and scanning electron microscopy, respectively. The static magnetic properties at room temperature and Curie temperature of the samples were investigated by vibrating sample magnetometry. The results indicated that the main phase of the sintered samples was Ni0.75Zn0.25Fe2O4 with spinal structure, and the sintering temperature and heating rate observably affected the microstructure and density, then the magnetic properties of the sample. The Joule heat generated by NiZn ferrite during spark plasma sintering was very important for the rapid preparation of the sample with high density and small grain size. The low sintering temperature and heating rate would be helpful to obtain samples with small grain size, high density, and then good magnetic properties. The samples sintered at 900 °C with the heating rate of 5–10 °C/s were characterized of the relative density above 95%, 4πMs value beyond 4000 Gs and coercivity below 27.7 Oe.

Statistical optimization of the elaboration of ceramic membrane support using Plackett-Burman and response surface methodology

The effect of Sintering temperature (ST), Particle size (PS), Starch content (SC) and Heating rate (HR) of the Ceramic Support Membrane Elaboration based on wet clay were evaluated using Plackett-Burman Design (PBD) and investigated by porosity and mechanical strength measures. Response Surface Methodology based on Central Composite design (CCD) was used for further optimization. The supports have been prepared from a clay with a two fraction 2 and 30 µm and a starch to enhance the performance of the support. The supports sintered between 900 °C and 1200 °C with a different heating rate (1 °C/min and 10 °C/min). By using PBD, it was found that the sintering temperature (ST) and starch content (SC) are the main controlling factors of the physical properties of ceramic support membrane. The increase of ST had a positive effect on Mechanical strength and negative effect on porosity, on other hand the increase of SC had a positive effect on porosity and negative effect on Mechanical Strength. The optimal factors to elaborate the membrane support by using CCD include a sintering temperature of 1014.36 °C and starch content of 4% predicting the porosity of 38.79% and Mechanical strength of 12 MPa.

Clay Ceramic Support Membrane Optimization Using Factorial Design Approach

In the present study, the effect of Sintering temperature, Particle size and Heating rate of the ceramic support membrane Elaboration based on dry clay were evaluated using full factorial design and investigated by porosity and mechanical strength measures. The flat supports have been prepared from 5 g of the material with a two fraction 2 and 30 µm, the extrusion was performed using the uniaxial pressing in applicant a pressure of 12 tones, the supports sintered between 900° C and 1200°C with a different heating rate (1°C/min and 10°C/min). By using full factorial design 23, it was found that the sintering temperature is the main controlling factors of the physical properties of dry ceramic support membrane, and its increase had a positive effect on Mechanical strength and negative effect on porosity. The interactions between the factors were relatively less important, and they had different (antagonistic/synergetic) influence on the properties. The optimal factors to elaborate the support membrane include a particle size of 2 µm, sintering temperature of 950°C, Heating rate of 1°C predicting the porosity of 40, 8% and Mechanical strength of 12 MPa.

High heating rate sintering and microstructural evolution assessment using the discrete element method

An original discrete element model for coupling thermo-mechanics with sintering is presented to disclose the thermo-micromechanical behavior of particulate systems and their densification process under rapid firing. This paper focuses on the numerical model formulation and application on the fast firing of Al2O3, including its verification with literature. Particular emphasis is given to the evolution of thermal and densification gradients over sintering conditions and sample length, zeroing in on the shrinkage evolution and the characteristic densification phenomena. Relationships between defects, microstructure, and sintering parameters are also explored. Finally, the time-dependent change of material microstructure concerning coordination number evolution, cohesive neck size distribution, gradients of temperature, and sample length are analyzed. The numerical results present good agreement with experimental data from the literature.