Search

Production of blast furnace sinter is among the processes with the highest energy and material requirements. Fuel consumption is especially significant cost item here. The presence of grate sintered in charge, i.e. return sinter from 12 to 22 mm in size, can have fundamental impact on the technical and economic indicators of the sintering process. Grate sinter can be used as a foundation layer under the sintering mixture, to increase air permeability of charge and to improve the gas-dynamic conditions. The article analyzes the impact of grate sinter on the sintering process, based on an analysis of the acquired production indicators within the scope of the research in question.

This paper presents a new technology for preparing the mixture for iron ore sintering process. The nature of component mixing and granulation has been discussed. The application of the intensive mixer in the preparation of the process components has been shown. The results of the analysis of the sintering mixture granulation process using laboratory installation for mixing and granulation have been presented.

This investigation deals with the effect of replacing some amount of Baharia high barite iron ore concentrate by mill scale waste which was characterized by high iron oxide content on the parameters of the sintering process., and investigation the effect of different amount of coke breeze added on sintering process parameters when using 5% mill scale waste with 95% iron ore concentrate. The results of this work show that, replacement of iron ore concentrate with mill scale increases the amount of ready made sinter, sinter strength and productivity of the sinter machine and productivity at blast furnace yard. Also, the increase of coke breeze leads to an increase the ready made sinter and productivity of the sintering machine at blast furnace yard. The productivity of the sintering machine after 5% decreased slightly due to the decrease of vertical velocity.

Coke breeze is the main fuel used in the sintering process. The value of -3+1 mm. represents the most favorable particle size for coke breeze in the sintering process. About 20% of total coke fines (-0.5 mm) are produced during different steps of preparation. Introducing these fines during the sintering process proves to be very harmful for different operating parameters. Thus ,this study aims at investigating the production of granules resulting from these fines using molasses as organic binder and its application in sintering of an iron ore. The results showed that the granules having the highest mechanical properties were obtained with 14.5 wt % molasses addition. The sintering experiments were performed by using coke breeze in different shapes (-3+1 mm in size, coke breeze without sieving and coke breeze granules -3+1 mm). The reduction experiments, microscopic structure and X-ray analysis for the produced sinter were carried out. The results revealed that, all sinter properties (such as shatter test, productivity of sinter machine and blast furnace, reduction time and chemical composition) for produced sinter by using coke breeze with size -3+1 mm and coke breeze granules were almost the same. The iron ore sinter which was produced by using coke breeze without sieving yielded low productivity for both sinter machine and blast furnace. Furthermore, using coke breeze without sieving in sintering of an iron ore decreases the vertical velocity of sinter machine and increases the reduction time.

The optimal operation of the blast furnace depends considerably on the properties of the sinter fed into the furnace. As a result, the optimization of the sintering processes has a direct effect on the overall effectiveness of the iron making processes. In order to produce a good sinter special care needs to be taken in order to assure it has a good permeability and reducibility and it is able to retain these properties for a certain time. If the sinter starts to melt down early in the upper part of the blast furnace, where its solid state reduction is essential, permeability decreases, the gas channels get blocked, reductibility diminishes and serious problems may also follow. Among the factors that influences the above mentioned sinter properties are the oxygen potential and fluxing components. Nevertheless, their effect on the phase relations during sintering and sinter reduction conditions has not yet entirely clarified and confusion exists in literature. This quantification becomes even more important today where many new minor components such as Al2O3 and MgO enter the sinter through raw materials. This work quantifies the effect of oxygen potential and fluxing components such as alumina and magnesia on the liquidus and phase relations of the sinter primary melts in the iron rich portion of CaO-FeO-Fe2O3-SiO2 system at sintering conditions. This is carried out by the means of new type of industrial diagrams in the form of Fe/CaO vs. SiO2 that can directly help the optimization of the sintering processes.

The Egyptian Iron and Steel Company generates a great amount of blast furnace flue dust. The recovery of metals and carbon from this flue dust becomes a very important demand due to the increase of the price of coke breeze and the decrease of the primary source of metals. At the same time, it make the environment more safe by decreasing pollution. Introducing these dust fines in the sintering process proves to be very harmful for different operating parameters. Thus, this study aims at investigating the production of pellets resulting from these fines, using molasses as organic binder and its application in sintering of iron ore. The sintering experiments were performed using flue dust as pellets as a substitute of coke breeze. The results revealed that, sintering properties such as inter strength increases with using the flue dust pellets, while productivity of both the sinter machine and sinter machine at blast furnace yard decreases. Also the vertical velocity of the sinter machine and the weight loss during the reduction of produced the sinter by hydrogen decrease.

Ti 2 SnC modified copper-graphite composites were fabricated by spark plasma sintering (SPS) and gas pressure sintering with 40 wt% Cu, 10 wt% graphite, and 50 wt% Ti 2 SnC as components. The phase composition, microstructure, and relative density of the composites were analyzed in detail. The results show that Sn atoms diffuse out from Ti 2 SnC and into the copper matrix in the composite sample and those fabricated by SPS are stronger than that of gas pressure sintering. The bonding of copper and graphite is favorable, but the pores created by the agglomeration of Ti 2 SnC grains are difficult to eliminate by using SPS to fabricate the composites. In contrast, air pressure sintering is beneficial for eliminating the pores caused by the agglomeration of Ti 2 SnC grains, but perfect mechanical interlocking between copper and graphite is lacking. • Ti 2 SnC modified copper-graphite composites were prepared with copper-coated graphite, copper and Ti 2 SnC. • The composites were fabricated by SPS and gas pressure sintering. • The composites samples were analyzed by XRD, SEM and EDS. [ABSTRACT FROM AUTHOR]

[Display omitted] • The return fines embedding technology is proposed to reduce fuel consumption. • Return fines are recommended to embed in the lower layer of the sintering bed. • The O 2 concentration in flue gas is decreased while the gas temperature is increased. • The fuel consumption can be reduced by 16% at most via the sintering pot test. • The fuel combustion is intensified due to the improved permeability. Fuel combustion provides the essential energy required for the iron ore sintering process, this process results in tremendous carbon dioxide emissions. Therefore, it is vital to develop innovative strategies to reduce fossil fuel consumption by effectively utilizing the heat storage effect in packed beds. Herein, an innovative double-layered fuel segregation method with return fines embedded in the lower layer was proposed and validated, and a goal of intensively reducing fuel consumption by 16% was achieved. Specifically, the oxygen concentration in the flue gas decreased from 16.7% to 11.5%, whereas the carbon dioxide and carbon monoxide concentrations increased from 5.5% and 0.3% to 13.4% and 1.3%, respectively. Moreover, the tumbler and shatter indices increased by 1.7% and 3.2%, respectively, indicating an increase in the sinter quality. In addition to optimizing the parameters of the proposed technology, the mechanisms for intensifying fuel combustion by applying the proposed technology were elucidated. The narrow thicknesses of the combustion and over-wet zones were found to significantly contribute to the improved permeability of the sintering bed. [ABSTRACT FROM AUTHOR]

By reviewing development of waste heat utilization in sintering process and sinter cooling process, two major difficulties are more and more apparent. A system of low temperature waste heat utilization based on organic fluids is proposed, which is composed of flue gas waste heat utilization heat exchanger, thermal storage subsystem and organic Rankine cycle (ORC) subsystem. The sintering flue gas and the sinter cooling air are adopted as the heat source. And on this basis, we establish the simulation analysis platform for the whole thermodynamic system. From a comprehensive perspective, the low temperature waste heat utilization could run well when the sintering heat source fluctuates within a certain range. It means that, the ORC-based system could overcome difficulties in utilizing waste heat in sintering process. [ABSTRACT FROM AUTHOR]

The occurrence of PDC deposits in a foredeep basin sequence, named Val d'Aveto Formation (32–29 Ma, Northern Apennines, Italy), provides new information on the behavior of pyroclastic density currents entering the water. In this work, stratigraphic, petrographic and mineralogical features that characterize three pyroclastic deposits have been described and analyzed in the field (facies and lithological analysis on the blocky-size fraction) and in the laboratory (image analyses on the blocky-size detritus, optical analyses of the microtextures, mineralogical analyses through X-ray powder diffraction (XRPD) and scanning electron microscope with energy dispersive X-ray spectometry (SEM-EDS). The deposits are lapilli- to blocky-size, with a blocky-size fraction constituted of accidental detritus. In thin sections, their groundmass texture varies from porphyritic to eutaxitic where coarser particles become close each others. Growth rims have been also detected around plagioclase crystals. Pyrite habits and oxidation, and plagioclase albitization are consistent with hydrothermal temperature conditions of ~ 200 °C. All these results have been compared with the information provided by modern examples of PDC deposits and laboratory experiments on the behavior of water/hot particles mixing. Grain-to-grain collision has been considered as the main flow mechanism that sustained and avoided the disaggregation of the PDCs entering the water. [ABSTRACT FROM AUTHOR]

Basing on raw materials conditions of typical iron and steel plant， the sintering experiments were carried out for the Indonesia vanadium titanium magnetite under different basicity and the effect of binary basicity (R=m(CaO)/m(SiO2)) on the sintering process and sinter′s quality were investigated in this work. The results showed that when the basicity (R) increased from 1.4 to 2.3， the coefficient of sintering effectiveness decreased from 1.63t/(m2·h) to 1.44t/(m2·h) and the rate of finished products after sintering decreased from 78.5% to 75.3%. Meanwhile， with the increasing of basicity， the vertical sintering speed increased gradually and the w(FeO) decreased constantly. Moreover， with the increasing of basicity from 1.4 to the 2.3， the drum index firstly dropped to the lowest value at the basicity of 1.7 and then rose gradually. With the increase of basicity， both the reduction degradation index (RDI) and reducibility index (RI) could be improved， which help to develop the gas permeability at the top of the furnace and the indirect reduction ability. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Northeastern University (Social Science) / Dongbei Daxue Xuebao (Shehui Kexue Ban) is the property of Dongbei Daxue and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A novel fabrication process for solid oxide fuel cells (SOFCs) with La0.2Sr0.7TiO3- δ (LSTA-) as anode support and La2NiO4+ δ (LNO) as cathode material, which avoids complicated impregnation process, is designed and investigated. The LSTA- anode-supported half cells are reduced at 1,200 °C in hydrogen atmosphere. Subsequently, the LNO cathode is sintered on the YSZ electrolyte at 1,200 °C in nitrogen atmosphere and then annealed in situ at 850 °C in air. The results of XRD analysis and electrical conductivity measurement indicate that the structure and electrochemical characteristics of LNO appear similar before and after the sintering processes of the cathode. By using La0.6Sr0.4CoO3- δ (LSC) as current collector, the cell with LNO cathode sintered in nitrogen atmosphere exhibits the power density at 0.7 V of 235 mW cm−2 at 800 °C. The ohmic resistance (RS) and polarization resistance (RP) are 0.373 and 0.452 Ω cm2, respectively. Compared to that of the cell with the LNO cathode sintered in air, the sintering processes of the cell with the LNO cathode sintered in nitrogen atmosphere can result in better electrochemical performance of the cell mainly due to the decrease in RS. The microstructures of the cells reveal a good adhesion between each layer. [ABSTRACT FROM AUTHOR]

The sintering process of belite sulphoaluminate cement (CSA 1 The abbreviations used in this essay are listed as below: belite sulphoaluminate cement = CSA, ordinary Portland cement = OPC, C = CaO, S = SiO 2 , A = Al 2 O 3 , F = Fe 2 O 3 , S ¯ = SO 3 , H = H 2 O. 1 ) clinker is still not clear to date. Besides, there are few reports concerning producing CSA by recycled BOF slag. Therefore, the sintering process of CSA was investigated from this perspective and the results can be a reference for BOF slag disposal. Four kinds of CSA clinkers with different additions of BOF slag were sintered at 1300 °C for 30 min. The sintering process was traced by heating microscope and the characteristics were analyzed by XRD, SEM-EDS and TAM Air. The results showed that the sintering degree of CSA clinker could be predicted by analyzing its sintering process. Furthermore, BOF slag could improve the melting state of CSA clinkers due to its composition containing iron oxide, manganese oxide and magnesium oxide. However, expansion was detected when the temperature reached 420 °C, which was arose by combined factors, namely volatilization of CO 2 decomposed from MgCO 3 and the thermal expansion of raw materials itself. The rational ratios of C 2 S, C 4 A 3 S ¯ , C 4 AF in CSA clinker with 14% BOF slag as raw material stood at 50%, 30%, 20% and its early hydration behavior was better than that of ordinary Portland cement (OPC) at the initial 16 h. [ABSTRACT FROM AUTHOR]

Since grey theory and neural network could improve prediction precision, the technology of combination prediction was proposed in this study. Then the algorithm was simulated by Matlab using practical data of a fuming furnace. The results reveal that the smelting endpoint of fuming furnace could be accurately predicted with this model by referring to small sample and information. It shows that the GNN algorithm not only has strong global search capability, but also is easy to implement. A Smelting Endpoint of Fuming forecasting empirical example has shown that compared with back-propagation artificial neural networks and single gray theory algorithm, GNN algorithm can achieve higher prediction accuracy, better computational speed, and which is more suitable for Prediction of Smelting Endpoint of Fuming forecasting. Therefore, GNN model is effective with the advantages of high precision, fewer samples required and simple calculation. [ABSTRACT FROM AUTHOR]

Asymmetric alumina hollow fiber membranes were prepared using the phase inversion technique followed by the sintering process at high temperatures. The ceramic suspensions were formulated by mixing alumina powder with polyethersulfone (PESf), polyethylene glycol-30-dipolyhydroxystearate and N-methyl-2-pyrrolidone (NMP) as the polymer binder, dispersant and solvent, respectively. The objectives of this study were (i) to investigate the effects of spinning parameters, namely, ceramic loading, ceramic to polymer binder ratio, different internal coagulant temperatures and air gap variation on asymmetric structure formation and (ii) to study the self-cleaning properties of alumina hollow fiber membranes. The ceramic hollow fiber membrane was characterized in terms of its viscosity, structural morphology and mechanical strength using a scanning electron microscope (SEM). The results showed that the finger-like structures in alumina hollow fiber membranes could be formed but their patterns were influenced by the ceramic suspension and spinning parameters. Variations in their morphology resulted in significant effects on the mechanical properties and permeability of ceramic hollow fiber membranes. A CuO/CeO 2 catalyst was deposited onto the alumina membrane support with the catalyst distribution determined by SEM/EDX. Self-cleaning properties were examined by comparing normal cleaning and self-cleaning properties with irradiation of UV for protein rejection. The result of self-cleaning by UV showed higher bovine serum albumin (BSA) permeation due to super-hydrophilicity of the CuO/CeO 2 catalyst. [ABSTRACT FROM AUTHOR]

In the paper, sintering process and contact formation process of PTO glass containing pastes were studied by interrupting the firings at different temperatures. Microstructures of contact fingers fabricated using pastes with PTO glass by interrupted firings were obtained by FIB/SEM technology and the sintering process of pastes was studied. The sintering process of pastes can be divided into three stages, the initial stage, intermediate stage and final stage, respectively. Only during the initial stage and intermediate stage of sintering, Ag-containing glass-phase is able to flow downward to the interface of Ag/Si through the continuous pore channels between Ag particles due to the great densification of Ag in the final stage of sintering. The great disharmony between the flow process of glass-phase and Ag densification would cause much glass trapped in densified Ag and thereby non-uniform etching of Si wafers. Contact formation process of pastes was studied by observing the Ag contact and Si emitter interface. Ag precipitates can be observed in the interfacial glass-phase at low firing temperature. Ag crystallites embedded in Si emitter appear at relative high temperature, along with the decreased number of Ag precipitates located in the interfacial glass-phase. Lower viscosity and higher ion diffusion velocities of interfacial glass-phase will make Ag crystallites appear at lower temperature. The increased interfacial glass layer thickness and abnormal growth of Ag crystallites, together with the decreased number of Ag precipitates cause the increase of contact resistance with the increase of sintering temperature. [ABSTRACT FROM AUTHOR]

In this research, the effects of surrounding powder used during sintering of Sb and Mn doped bariumstrontium titanate (BST) ceramics were studied. The ceramic samples were prepared by a conventional mixed-oxide method and placed on different powders during sintering. Phase formation, microstructure and PTCR behavior of the samples were then observed. Microstructures and PTCR behavior varied with the type of surrounding powder, whereas the crystal structure did not change. The surrounding powder has more effects on the shape of the grain than on the size. The grain size of samples was in the range of 5-20 μm. The most uniform grain size and the highest increase of the ratio of ρmax/ρRT were found to be about 106 for samples which had been sintered on Sb-doped BST powder. This value was an order of magnitude greater than for samples sintered on a powder of the equivalent composition to that of the sample pellet.

This study reports the micro-structural and electrochemical properties of metal-supported solid oxide fuel cells (MS-SOFCs) with an La 0.8 Sr 0.2 MnO 3−d (LSM)/8 mol% yttria-stabilized zirconia (8YSZ) composite cathode, fabricated at room temperature using the aerosol deposition process (ADP). The composite cathode fabricated with the ADP technique shows uniform distribution of components and pores and the interface between the cathode and the electrolyte displays excellent joining properties. The area specific resistance (ASR) of the ADP-LSM/8YSZ sample is approximately 1.50 Ω cm 2 at 800 °C, so this sample shows a significantly lower ASR value than the values usually reported for samples fabricated by the in-situ treatment method for MS-SOFCs. The power density of the cells with the ADP-LSM/8YSZ cathode coated on MS-SOFCs shows a maximum value of 0.38 mW cm −2 at 800 °C and stable performance in the severe thermal durability test. Therefore, these research results can broaden the opportunities for adoption of the ADP coating processes to fabricate cathode materials in MS-SOFCs. [ABSTRACT FROM AUTHOR]

Samples of low-density, highly disordered silica aerogel with initial bulk density of 0.16 g/cm3, were sintered isothermally in different time intervals at 1000ºC. Structural changes during the sintering process have been investigated by Raman spectroscopy. Defect modes of irregular three and four membered rings were observed in the Raman spectra of sintered samples.

Many different parameters affect the antenna performance of the wearable sensors. In this study, antenna performances of textile based sensors which have different pass numbers from 1 to 5 printed using conductive ink with pad printing method were investigated. Moreover, the effect of sintering process after printing on the RF antenna performances of wearable sensors was examined. For this, antenna impedances, and reflection coefficients of the sintered, and non-sintered printed sensors were measured using a vector network analyzer. While the frequency at the collapse point of the reflection coefficient graph of the sensors without sintering and with different pass numbers was 254 MHz, the collapse point of the reflection coefficient graph of the sensors was 943 MHz after sintering. The measurements indicate that the sintering process has a significant effect on the antenna performances of wearable sensors, and it is concluded that the sintered printed wearable sensor samples enable data transmission wirelessly in short range. In addition, bending, and gain measurements was applied to wearable sensor which has the best performance according to the impedance measurement results. Thus, these UHF-RFID enabled wearable sensors with antenna performance might be good option to form a network of passive interactive sensor architecture for RFID and wearable technologies. In addition, considering the designed wearable sensor structure, it is foreseen that the potential usage areas of this structure may be moisture sensitive areas (such as supply chains and transportation of moisture-sensitive products). [ABSTRACT FROM AUTHOR]

[Display omitted] • Online FeO content detection of sinter is realized in the end-to-end form. • A target detection model is designed to capture key frame images. • An improved CNN model is established to map relationship between KFI and FeO. • Detection error within ± 0.5 % reaches 91.2 % and RMSE is less than 0.3 %. Sintering is an important process in iron and steel manufacturing. FeO content of sinter is a key index for both sintering and blast furnace ironmaking, but it needs manual sampling and testing in practical production. In this research, an online measurement method based on machine-tailed infrared images and convolutional neural network (CNN) for the FeO content is proposed. Firstly, a target detection model of sinter bed cross-section (SBC) is established, to obtain the key frame image (KFI) of SBC in each unloading cycle. Then, the KFI is labeled with the offline chemical analysis of FeO content, and a modified CNN is proposed to build the online measurement model for FeO content. The experimental results show that the proportion of samples with detection error of FeO content within ± 0.5 % reaches 91.2 % and the RMSE is less than 0.3 %. It provides a novel measurement approach for online detection of FeO content. [ABSTRACT FROM AUTHOR]

This article proposes a method for the synthesis of fuzzy logic controllers for control of complex technological processes on the example of sinter production. The proposed method is based on the self-organizing knowledge bases of fuzzy controllers using the so-called fuzzy-supplementing optimizing algorithm. This method differs from the known ones by capability to synthesize control systems that meet the quality criteria and reduced amount of computation required to solve the problem of the synthesis. [ABSTRACT FROM AUTHOR]

This work describes the preparation of yttria-stabilized zirconia (YSZ) hollow fibre membranes using the phase inversion and sintering process. The study aims to provide generic information on the effects of membrane preparation on the morphology and mechanical properties of YSZ hollow fibre membranes. In this work, ceramic suspensions were prepared by mixing YSZ particles, dispersant, polymer binder and organic solvent using a planetary ball milling machine. This process was followed by extrusion into a coagulation bath via an air gap, drying and sintering process at temperatures ranging from 1250 °C to 1400 °C. The results show that by varying the YSZ loading and YSZ/PESf ratio, different morphologies of ceramic hollow fiber membranes can be obtained due to variations in the viscosities of ceramic suspensions. Similarly, air-gap length between the spinneret and coagulant surface was found to affect the growth of the finger-like structures and sponge-like regions. Varying these parameters also gave significant effects on the mechanical strength of the ceramic membrane due to the change in membrane thickness and compactness. The sintering process had insignificant effects on the membrane morphology but the process can be used to enhance the mechanical strength of ceramic hollow fiber membranes. The optimum temperature of the sintering process was identified. It was found that increasing the sintering temperature further caused a reduction in the mechanical strength due to crack formation in the ceramic hollow fiber membrane. The preliminary performance tests showed that the ceramic hollow fiber membrane sintered at 1300 °C has a pure water flux of 118.4 L/m 2 h. It also has a high PEG rejection with molecular weight cut off (MWCO) of 60 kDa. [ABSTRACT FROM AUTHOR]

Rapid prototyping technology ( RP), based on designing and computer aided manufacturing, is widely used in traditional branches of industry. Due to its ability to accurately and precisely manufacture designed elements of various dimensions and complicated geometry, this technology is more and more frequently applied in the field of biomedical engineering. Selective laser sintering ( SLS) is a universal RP technique, utilizing a laser beam to sinter powdered materials and create three-dimensional objects. Data for producing parts for tissue replacement come from medical imaging capabilities and digital presentation of test results. This paper presents the following: general classification of RP methods, the concept and methodology of performing laser sintering, sintering mechanisms, and the application of elements manufactured using this technology in biomedical engineering, particularly for the production of scaffolds used in tissue cultures, skeletal and dental prostheses in dental implantation, manufacturing of custom-made implants that are individually adjusted to the patient, and for production of training models on which a team of surgeons can train a surgical technique. [ABSTRACT FROM AUTHOR]

Ti(C,N)-TiB-(W,Ti)C composite ceramic cutting tool materials were prepared using the vacuum hot-pressed sintering technology. The effects of the sintering temperature and the heating rate on the mechanical properties and microstructure of different composite materials containing different contents of TiB were investigated. The sintering process of a higher temperature with a fast heating rate or a lower temperature with a slow heating rate was found to be beneficial to the mechanical properties of the composites. The better sintering temperature range for fabricating the composites was from 1585 to 1620 °C. The composite material with a content of 30 wt% TiB sintered at 1585 °C with either a heating rate of 90 or 50 °C/min had the prominent flexural strength. The composite with a content of 20 wt% TiB sintered at 1620 °C with a heating rate of 90 °C/min had the relatively better fracture toughness and hardness than that with a content of 30 wt% TiB. The two core-rim microstructures were formed inside the TiB and Ti(C, N) grains, which further contributed to a compact microstructure and improved the mechanical properties of the composites. The optimum sintering temperature range for the formation of the core-rim microstructures was also from 1585 to 1620 °C. [ABSTRACT FROM AUTHOR]

This article presents a three-dimensional mathematical (dynamic) model of the sintering process. The model was developed to solve theoretical and practical problems. It allows real-time determination of the distributions of the temperatures and the chemical compositions of the charge, the melt, the sinter cake, and the gas in the bed of charge materials with allowance for transients. The model also permits real-time determination of the temperatures in the pallets and the parameters of the gas flow (including infiltrating air) in the flue system of the sintering machine. [ABSTRACT FROM AUTHOR]

Aims To evaluate the effect of the processing method (conventional sintering, S, and heat-pressing, HP) and addition of potassium titanate fibers, PTF, on the microstructure, mechanical properties (flexural strength, σ f , and Weibull parameters, m and σ 5% ), slow crack growth parameters n (stress corrosion susceptibility coefficient), and optical properties (translucency parameter, TP, and opalescence index, OI) of a feldsphatic dental porcelain. Methods Disks ( n =240, Ø12×1 mm) of porcelain (Vintage-Halo, Shofu) were produced using S and HP methods with and without addition of 10 wt% (conventional sintering) or 5 wt% (heat-pressing) of PTF. For the S method, porcelain was sintered in a conventional furnace. In the HP technique, refractory molds were produced by lost wax technique. The porcelain slurry was dry-pressed (3 t/30 s) to form a cylinder with 12 mm (diameter) and 20 mm (height), which was heat-pressed for 5 min/3.5 bar into the mold. Specimens were tested for biaxial flexural strength in artificial saliva at 37 °C. Weibull analysis was used to determine m and σ 5% . Slow crack growth (SCG) parameters were determined by the dynamic fatigue test, and specimens were tested in biaxial flexure at five stress rates: 10 −2 , 10 −1 , 10 0 , 10 1 and 10 2 MPa/s ( n =10), immersed in artificial saliva at 37 °C. Parameter n was calculated and statistically analyzed according to ASTM F394-78. Optical properties were determined in a spectrophotometer in the diffuse reflectance mode. Results The highest n value was obtained by the combination of heat-pressing with fiber addition (37.1) and this value was significantly higher than those obtained by both sintered groups (26.2 for control group and 27.7 for sintered with fiber). Although heat-pressing alone also resulted in higher n values compared to the sintered groups, there were no significant differences among them. Fiber addition had no effect on mechanical strength, but it resulted in decreased TP values and increased OI values for both processing methods. Heat-pressing alone was able to reduce the porosity level of the porcelain. Conclusions Addition of PTF combined with heat-pressing can reduce strength degradation of a dental porcelain compared to sintered materials with or without fibers. Heat-pressing (HP) alone should be considered as a good alternative for clinical cases where high translucency is required. [ABSTRACT FROM AUTHOR]

two stage process including a sintering under a cyclic loading is proposed as an alternative fabrication method of dense FeAl intermetallics from elemental powder mixtures. The first stage (pre-sintering) is conducted at two temperature values (620 °C and 670 °C, respectively) under a static and a cyclic loading with a frequency of 20, 40 and 60 Hz. The second one includes a pressureless sintering at temperature of 1250 °C, under a protective argon atmosphere. A suitable selection of pre-sintering parameters (temperature, type and frequency of pressing) allows approximately five times grain size reduction of FeAl phase in comparison to particle size of raw Fe and Al powder material (40-60 µm), as well as induces an effective fragmentation of oxide layers. For the sinters obtained using 60 Hz loading frequency an oxide particle size of 4.0 or 4.5 µm (smaller for sintering with liquid phase) is observed. Material obtained after the full heat treatment are characterized by a fine-grained structure of chemically homogeneous FeAl phase with uniformly distributed Al2O3 spherical particles along grain boundaries. Moreover, it was found that temperature and frequency of loading during the presintering process also affect a consolidation level of the Fe-Al powder mixture, which increases with rising both temperature and frequency. [ABSTRACT FROM AUTHOR]