Sintering Furnace Research Articles

Medium-Frequency Electrical Resistance Sintering of Soft Magnetic Powder Metallurgy Iron Parts

The fabrication of soft magnetic Fe parts by the medium-frequency electrical resistance sintering (MF-ERS) technique is studied in this paper. This consolidation technique involves the simultaneous application to metallic powders of pressure and heat, the latter coming from the Joule effect of a low-voltage and high-intensity electric current. Commercially pure iron powder was used in the consolidation experiences. The porosity distribution, microhardness, electrical resistivity and hysteresis curves of the final compacts were determined and analysed. The results obtained were compared both with those of compacts consolidated by the conventional powder metallurgy (PM) route of cold pressing and vacuum furnace sintering, and with fully dense compacts obtained by double cycle of cold pressing and furnace sintering in hydrogen atmosphere.

Effect of Microwave and Conventional Modes of Heating on Sintering Behavior, Microstructural Evolution and Mechanical Properties of Al-Cu-Mn Alloys.

In this research, we intended to examine the effect of heating mode on the densification, microstructure, mechanical properties, and corrosion resistance of sintered aluminum alloys. The compacts were sintered in conventional (radiation-heated) and microwave (2.45 GHz, multimode) sintering furnaces followed by aging. Detailed analysis of the final sintered aluminum alloys was done using optical and scanning electron microscopes. The observations revealed that the microwave sintered sample has a relatively finer microstructure compared to its conventionally sintered counterparts. The experimental results also show that microwave sintered alloy has the best mechanical properties over conventionally sintered compacts. Similarly, the microwave sintered samples showed better corrosion resistance than conventionally sintered ones.

Assessment of the emission factors for potentially toxic elements from coal-fired boilers and sintering furnaces in a steel production plant

The emission factor (EF), the weight of potentially toxic elements (PTEs) per unit energy or weight of sinter produced were evaluated for coal-fired boilers and sintering furnaces integrated in a steel plant. From three coal-fired boilers, 15 samples were taken while 22 samples were taken from four sintering furnaces. Investigations were performed on the EF of lead, cadmium, mercury, arsenic and chromium (VI). The coefficient of variance for the first 3 samples from each PTE was used to decide whether 2 more samples were necessary for the investigation. Three samples were sufficient for Cr (VI), however, 5 samples were required for Pb, Cd, Hg, and As, since the variances in concentrations of the first three samples exceeded 20%. The ranges for the ratio of the laboratory-based EF to the default EF applied by the Environment Protection Administration (EPA Taiwan) for Pb, Cd, Hg, and As for the coal-fired boiler were 0.08–0.013, 0.014–0.017, 0.019–0.033, 0.047–0.066 and for the sintering furnaces were 0.059–0.232, 0.05–0.151, 0.05–0.364, and 0.067–0.824. The ratio for Cr (VI)- was constant at 0.005 for all the coal fired boilers while it ranged from 0.057–0.709 for the sintering furnaces. Whilst source identification, enrichment factors, and spatial distributions for PTEs are often studied, laboratory-based investigations on the EFs for PTEs from industrial plants are rarely performed. This study filled the information gap and compared the obtained EFs with the EPA default values. To avoid overcharging industrial plants equipped with the best available technology for emission control, the EPA should apply field investigations and laboratory-based EFs instead of the default EPA EFs to calculate air pollution fees. Insights from this investigation can be applied to promote the adoption of appropriate air pollution control devices to cut down the emission of PTEs.

4D Printing of Lead Zirconate Titanate Piezoelectric Composites Transducer Based on Direct Ink Writing

Lead zirconate titanate (PZT) piezoelectric composites used in transducers were fabricated via direct ink writing (DIW) combined with furnace sintering and resin impregnation. A ceramic slurry with a volume fraction of 52 vol% and suitable viscoelasticity was prepared. After post-process, the PZT ceramic specimens showed a nanoscale grain size with a density of 7.63 g/cm3, accounting for 97.8% of the theoretical density. The effects of different printing rod spacing on the electrical properties of composites were evaluated and lucubrated. Finally, an underwater acoustic transducer was assembled by using the PZT piezoelectric composites fabricated by the above method. The electrical signal generated by the underwater acoustic transducer changed autonomously with the acoustic stimulation, which indicated the application mode of 4D printing in functional devices in the future.

An Equilibrium Prediction Method for Control and Fault Detection of Energy Systems

Abstract Many fault detection, optimization, and control logic methods rely on sensor feedback that assumes the system is operating at steady-state conditions, despite persistent transient disturbances. While filtering and signal processing techniques can eliminate some transient effects, this paper proposes an equilibrium prediction method for first-order dynamic systems using an exponential regression. This method is particularly valuable for many commercial and industrial energy system, whose dynamics are dominated by first-order thermo-fluid effects. To illustrate the basic advantages of the proposed approach, Monte Carlo simulations are used. This is followed by three distinct experimental case studies to demonstrate the practical efficacy of the proposed method. First, the ability to predict the carbon dioxide level in classrooms allows for energy efficient control of the ventilation system and ensures occupant comfort. Second, predicting the optimal time to end the cool-down of an industrial sintering furnace allows for maximum part throughput and worker safety. Finally, fault detection and diagnosis (FDD) methods for air conditioning systems typically use static system models; however, the transient response of many air conditioning signals may be approximated as first-order, and therefore, the prediction model enables the use of static fault detection methods with transient data (a need that has not been addressed in over 20 years of air conditioning FDD research). In this paper, the equilibrium prediction method's performance will be quantified using both Monte Carlo simulations and case studies.

Preparation of Si2N2O wave-transparent and thermal insulation materials with Na2CO3 and BN as aids by pressureless sintering

A hexagonal boron nitride (h-BN)-bonded porous silicon oxynitride (Si2N2O) composite with a low dielectric constant, low thermal diffusivity, and high thermal shock resistance was fabricated by pressureless sintering, and the phase, microstructure, oxidation resistance, and mechanical and dielectric properties of the composites were investigated. The results demonstrated that Na2CO3 facilitated http://www.youdao.com/w/eng/facilitated/javascript:void(0); the generation of Si2N2O. With the subsequent volatilisation of Na2O at high temperatures, near-pure porous Si2N2O ceramics was obtained. However, in the presence of excess Na2CO3 (above 6 wt%), Si2N2O decomposed into Si3N4. The hardness of the Si2N2O/h-BN composite decreased from 1.4 ± 0.15 GPa to 0.4 ± 0.13 GPa with the addition of h-BN, which significantly improved the workability of the material. Moreover, the material exhibited a stable thermal expansion coefficient (3.36 × 10 −6 K−1 at 200 °C and 4.08 × 10 −6 K−1 at 1300 °C), low dielectric constant, and low dielectric loss (ε = 3.26, tan δ = 3.21 × 10−3 at a h-BN content of 9 wt%). Thus, it is a potential wave-transparent and thermal insulation material for microwave sintering furnaces.

High-temperature stability and phase transformations of titanium carbide (Ti3C2T x ) MXene

Two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, known as MXenes, are under increasing pressure to meet technological demands in high-temperature applications, as MXenes can be considered to be one of the few ultra-high temperature 2D materials. Although there are studies on the stability of their surface functionalities, there is currently a gap in the fundamental understanding of their phase stability and transformation of MXenes’ metal carbide core at high temperatures (>700 °C) in an inert environment. In this study, we conduct systematic annealing of Ti3C2T x MXene films in which we present the 2D MXene flake phase transformation to ordered vacancy superstructure of a bulk three-dimensional (3D) Ti2C and TiC y crystals at 700 °C ⩽ T ⩽ 1000 °C with subsequent transformation to disordered carbon vacancy cubic TiC y at higher temperatures (T > 1000 °C). We annealed Ti3C2T x MXene films made from the delaminated MXene single-flakes as well as the multi-layer MXene clay in a controlled environment through the use of in situ hot stage x-ray diffraction (XRD) paired with a 2D detector (XRD2) up to 1000 °C and ex situ annealing in a tube furnace and spark plasma sintering up to 1500 °C. Our XRD2 analysis paired with cross-sectional scanning electron microscope imaging indicated the resulting nano-sized lamellar and micron-sized cubic grain morphology of the 3D crystals depend on the starting Ti3C2T x form. While annealing the multi-layer clay Ti3C2T x MXene creates TiC y grains with cubic and irregular morphology, the grains of 3D Ti2C and TiC y formed by annealing Ti3C2T x MXene single-flake films keep MXenes’ lamellar morphology. The ultrathin lamellar nature of the 3D grains formed at temperatures >1000 °C can pave way for applications of MXenes as a stable carbide material 2D additive for high-temperature applications.

Modeling and Analysis of Temperature Compensation for Multi-temperature Zone Sintering Furnace Temperature Sensing

The surface temperature of workpieces in a multi-temperature zone sintering furnace is an important parameter to characterize the performances of a multi-temperature zone system. Due to the practical structural properties of the sintering furnace, however, the conventional way of temperature measurement cannot detect the exact surface temperature of the workpieces directly, making it difficult to control the multi-temperature zone system performances precisely. To address such an issue, this paper proposes, for the first time to the best of our knowledge, a temperature compensation algorithm based soft-measurement technique to compensate for the temperature of the measuring points. Specifically, we analyze the heat-transfer mechanism within the electric heating surface and the workpiece surface and establish a mathematical model for it first, and then calculate the radiative heat transfer coefficient between the diffuse gray surface within sintering furnace using the discrete radiation heat transfer method. Finally, the heat transfer mechanism based soft measurement technique is proposed and applied to compensate for the temperature. Both simulations and experiments with a practical sintering furnace are conducted to verify the correctness and effectiveness of the proposed temperature compensation algorithm in different cases. Results show that the proposed algorithm could help maintain the temperature difference within a range limit of ±5°, which is much better as compared with the conventional temperature measurement methods.

Sintered Fe-Mo-Mn-Si-C alloys

Sintered Fe-Mo-Mn-Si-C alloys were produced by alloying silicon and carbon elements to pre-alloyed Fe-0.5Mo-0.15Mn powder via sintering of mixtures of pre-alloyed powder and varied silicon carbide amounts (0.5-4.0 wt.% with 0.5 increment). The sintered alloys were cooled in a sintering furnace. Microstructures and mechanical properties of the sintered alloys were altered depending on added silicon carbide content. With up to 2.0 wt.% silicon carbide additions, the sintered alloys exhibited polygonal ferrite plus eutectoid decomposition products, showing non-cooperative ferrite and carbide growth mode. With silicon carbide contents of ≥ 2.5 wt.%, the sintered alloys exhibited microstructural feature similar to that of a ductile iron, i.e., a common feature consisted of a black particle enveloped with ferrite and pearlite. Tensile strengths of the sintered alloys increased but elongation values decreased with increasing added silicon carbide content. The sintered alloys produced by 3.5 and 4.0 wt.% silicon carbide showed high strengths and considerably good elongation values.

Sintered 316L/Cu/h-BN composites

Sintered 316L/h-BN composites show high potential as self-lubricating materials, which can be applied as moving parts where lube oils and greases are not applicable and inaccessible for maintenance. The past production of such composites by sintering, faced two problems. Firstly - interaction between 316L matrix and h-BN resulting in loss of h-BN content and its lubricity. And secondly - poor 316L matrix integrity. This work employed two approaches to solve such problems. The first approach was the use of nitrogen-containing atmosphere for sintering, to retard 316L matrix and h-BN interaction. And the second approach, was copper addition to promote sintering of 316L powder particles. Sintered self-lubricating 316L/Cu/h-BN composites were produced from mixtures of 3 different 316L/Cu matrices (made by additions of 2.0, 4.0 and 6.0 wt.% copper powder to 316L powder) and 15 vol.% of h-BN powder. Green compacts of powder mixtures were sintered under cracked ammonia (75 vol.% hydrogen + 25 vol. % nitrogen) at 1300°C for 60 minutes. The sintered composites were cooled in a Linn high temperature sintering furnace. It was found that copper additions led to the decrease of densities of sintered 316L/Cu/h-BN composites, compared to that of sintered 316L/h-BN composite, due to porosity left behind by copper powder melting and dissolution. Tensile strengths of sintered 316L/Cu/h-BN composites were improved when copper contents were 4 and 6 wt.%. There was no intergranular phase, the evidence of 316L matrix and h-BN interaction in all experimental sintered composites. Microstructural observation by scanning electron microscopy (SEM) also revealed that h-BN flakes still existed in pores of sintered composites. The unreacted h-BN flakes are expected to provide lubricity of sintered composites.

Simulation of irradiation intensity distribution of electrodeless ultraviolet lamp in cylindrical resonator by CFD

To improve the catalytic efficiency of the microwave single-mode sintering furnace to heat the catalyst and the carrier to catalyse the oxidation of toluene, the SJ-1 microwave single-mode sintering furnace was modified to place a microwave electrodeless ultraviolet lamp in the resonant cavity. The distribution of pollutants in the reactor and the intensity of UV light were calculated by CFD and visualized. The distribution of UV field can be seen from the results of light field, which provides a scientific basis for the placement of catalyst and a reference for the simulation of UV field. Under the conditions of relative humidity of 50%, space velocity of 6336.93 h−1, input power of 392.8 W, bed height of manganese oxide catalyst is 30 mm, initial toluene concentration of 235.23 mg/m3, input power of 595.3 W, toluene conversion efficiency of 94%. It has certain guiding significance.

A current-controlled flash sintering processing leading to dense and fine-grained typical multi-element ZnO varistor ceramics

Comparing to conventional sintering, the densification, microstructure and electric properties of typical multi-element ZnO-Bi2O3-based varistor ceramics on different constant furnace temperatures (850–1000 °C) were studied at electric field of 250 V/cm by flash sintering. The flash-sintered specimens of near full densification could be obtained within 35 s, which had finer grain size and more homogenous microstructure. The effect of different limited current on densification was investigated in flash sintering process. The results showed the relative densities of specimens from 89.9% to 92.0%, 95.5% while limited current increased from 1.0 A to 1.5 A, 2.0 A. The 950 °C flash-sintered specimen with the relative density of 98.0% had the highest threshold voltage of 656 V/mm with the nonlinear coefficient of 41.9. The dielectric loss of flash-sintered specimens had the value lower than 0.2. Thus, typical multi-element ZnO varistor ceramics could show uniform microstructure and excellent electric properties by constant furnace temperature flash sintering.

Fabrication of barium titanate ceramics via digital light processing 3D printing by using high refractive index monomer

A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices.

Smart Fiber Optics Embedding in Powder-Based Materials: Numerical and Experimental Assessment

This paper discusses embedding conditions of fiber-optic sensors in powder-based materials using two different techniques, i.e., cold compaction followed by furnace sintering and spark plasma sintering. The purpose is to build haptic sensorial materials for robotics applications. The results have shown promising possibilities for the sensors to be hosted and located anywhere inside the material using a defined process that is controlled with known parameters. These host materials become completely sensorial with in-depth sensors embedding at known positions in three-dimensional directions. The numerical modeling and simulation have shown good agreement with experimental analysis. This has allowed observing the integrity of both host materials and the sensors, as well as the good adherence of the sensors in embedded material to reproduce reliably the material behavior. The numerical modeling has supported proper preparation of the experiments and later in the manufacturing process with parts having complex geometries with embedded sensors and even actuators.

Capacitor Electrical Discharge Consolidation of Metallic Powders—A Review

Manufacturing metallic materials from elemental or alloyed powders is an option in many industrial processes. Nevertheless, the traditional powder metallurgy processing including furnace sintering is at times detrimental for the microstructure attained in the powders. Alternative sintering processes based on the use of electricity and the energy obtained by the Joule effect in powder particles can be quick enough to avoid microstructural changes. In particular, when the energy is stored in a capacitor and then discharged, the heating process is extremely quick, lasting milliseconds or even microseconds. This process, generally known as electrical discharge consolidation, has been applied to a wide variety of metallic materials, easily preserving the original microstructure of the powders. Both porous or homogeneous and highly densified material can be obtained, and without losing the desired properties of the consolidated material. A general overview of the process and applications, as well as the results obtained by different research groups around the world, have been reviewed in this manuscript.

The total content of macronutrients and heavy metals in the soil on devastated lands at Kryvyi Rih Iron Mining & Metallurgical District (Ukraine)


 
 
 he relevance of the research is due to the need to develop technologies for phytoremediation of the devastated lands in the mining and metallurgical regions of Ukraine and the world. In this regard, the creation of tree plantations adapted to the ecological conditions of such territories is considered by many experts as the most promising option for innovative technologies. However, the development of artificial woodlands requires knowledge of the pedogeochemical characteristics of devastated lands. The aim of the work was to carry out a comparative analysis of the macronutrients and heavy metals gross forms content in the soils of the devastated lands of the Kryvyi Rih mining and metallurgical region. The field studies focused on five contrasting monitoring sites of the Petrovsky dump (Central Kryvorizhzhya), which has a typical age and composition of rocks for the region. Soil sampling, drying, sieving, and sample preparation (sintering in a muffle furnace) were done in accordance with classical techniques. The concentrations of macronutrients (potassium, sodium, calcium, magnesium, sulfur, and phosphorus) and heavy metals (iron, manganese, zinc, copper, lead, and cadmium) were determined using an Inductively Coupled Plasma Mass Spectrometry (ICP- MS) X-Series 2 (Thermo Fisher Scientific, USA). The analytical part of our research was carried out on the basis of the laboratory of the Institute of Biosciences, Freiberg University of Technology and Mining Academy (Freiberg, Germany). At monitoring sites, significant differences were found in the content of macronutrients gross forms, and their variation relative to the control values as well. Potassium and sodium concentrations generally differed slightly or were close to control levels. The results of determining the content of calcium, magnesium and phosphorus indicate a significant deficiency or excess of these macronutrients in the soils of the devastated lands. An increased sulfur content was found in the soils of all monitoring sites, in some cases 4 times higher than the control level. The measured content of gross forms of iron, manganese, copper, cadmium and, partially, zinc in the soils of different monitoring sites exceeded the control values by 5.5 – 5.9 times. Thus, the analysis of the research results made it possible to establish that the soils of the devastated lands of the Petrovsky dump are characterized by unfavorable properties for the growth of most species of woody plants.
 
 

Effect of 2 wt.% Addition of Fe on the Compressive Properties and Corrosion Behavior of Zn-HAp-Fe Material

The present work deals in developing new zinc-based composite material for bone repair using a powder metallurgy process. Zinc (Zn), hydroxyapatite (HAp), and iron (Fe) powders were mechanically mixed with ball milling. Subsequently, the powder mixture was compacted to form the green compact. After that, the green compacts were sintered using a microwave sintering furnace. The mechanical and electrochemical behaviors of the prepared Zn-based samples were tested as per the standards. X-ray diffraction and energy-dispersive spectroscopic examinations revealed the existence of HAp and Fe in the Zn matrix. The compressive yield strength and compressive strength of the developed Zn-5HAp-2Fe material were found to be 117.91 ± 7.42 and 170.87 ± 7.41 MPa, respectively. In vitro electrochemical corrosion analysis of the developed Zn-5HAp-2Fe sample in simulated body fluid solution unveiled the corrosion rate as 0.116 ± 0.021 mm·year–1. The mechanical and degradation behaviors of Zn-5HAp-2Fe material showed the potential to be used as a bone fixation material.

Sintering of Ge-Sb-Se Chalcogenide Glass Powder by Tube Furnace and Spark Plasma Methods

In this research, density and infrared transmittance of chalcogenide glass sintered by two methods; tube furnace sintering (TBS) and spark plasma sintering (SPS), were studied and characterized. In TBS, the effects of sintering dwell temperature, dwell time, and heating rate on final density and transmittance were investigated. The TBS test showed that the transmittance was seriously deteriorated above the sintering temperature of 380 °C, resulted from the crystallization, Se evaporation, and pore expansion. To overcome the limitation of TBS, SPS was employed by adjusting the sintering condition. The results of a comparative study indicated that sintering temperature is a dominant factor affecting the transmittance and density of sintered glasses, closely related to pore fraction.

Synthesis and Characterization of Mg-Matrix Based TiO2/Al2O3 Composite Materials

Based on low density, Mg metal-based composites exhibit high specific mechanical properties and are actively used for weight critical structural application. In the present study, Mg-matrix based TiO2/Al2O3 composite materials were synthesized by using the powder metallurgy (Solid-phase) technique. Parameters such as the concentration of the components, temperature, and pressure were optimized before experiments. Different conditions such as temperature (30 °C) and pressure (760 mm of Hg) were also optimized. Pellets of the Mg-based composites and their pure constituent counterparts of various diameters (10–20 cm) were prepared under 50 tons of hydraulic pressure. Single-phase homogenous composites were obtained by undertaking the pellets through sintering in an electric furnace at elevated temperature (600 °C) for 1 h. The prepared materials were tested for different properties using various physicochemical techniques such as Fourier transform infrared spectroscopy (FTIR), Scanning electronic microscopy (SEM), X-ray diffraction (XRD) and Surface area analyzer. FTIR results confirmed composite formation. SEM revealed microstructures of all materials in the µm range. XRD proved the phase-distribution and crystallinity of the prepared materials. It was found that 2 and 3-component systems are homogenized when prepared by the powder metallurgy technique. The surface area of all materials was confirmed using the BET adsorption isotherm equation. The surface area of the prepared composites was found to be in the range from 40 to 70 m2/g. Such properties enable these materials for potential application in solar reflectance and as a catalyst in liquid phase hydrogenation.

Comparison of dry sliding tribological behavior of SS 316L impregnated with MoS2 vs h-BN solid lubricants: A statistical point of view

The main aim of this paper is to statistically discuss the friction and wear behavior of 316L stainless steel (SS316L) composites added with h-BN and MoS2 solid lubricant under different running conditions at room temperature. The SS316L composites added with h-BN and MoS2 were produced by the powder metallurgy method. The mixture of SS316L composites with 15 and 20 vol% of h-BN and MoS2 were cold compacted into ∅ 30 mm cylinder parts. Then sintered in the sintering furnace under H2 atmosphere for 60 min. Brinell's hardness and dry-sliding wear behavior of the sintered SS316L composites were investigated using a pin-on-disc testing machine. The factorial experimental design was employed to investigate the influence of specific independent variables on dry sliding wear, testing at sliding speeds of 0.1 and 0.2 m/s, applied load of 3 and 5 N and sliding distance varying from 100 to 200 m. The effects of tested variables on the specific wear rate and coefficient of friction were analyzed from both statistic plots and physical analyses of worn surface with SEM micrographs. The results showed that the MoS2 added composite resulted in greater wear resistance than h-BN added composite. The wear resistance and friction coefficient on dry sliding wear test also depended on the interaction effect of sliding distance, sliding speed and applied load which are relative to the formation of tribofilm on sliding interfaces. In addition, sliding speed influence to the formation of tribofilm showed significantly high levels of wear resistance and friction coefficient of composites. The statistical design of this experiment enabled us to collect and analyze wear data which provided a greater understanding of the complex mode/mechanism of sliding wear of SS316L self-lubricating composites.