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In this study, lead zirconate titanate (Pb(Zr_0.44Ti_0.56)O₃) ceramics were fabricated with a mixed oxide synthetic route of lead oxide (PbO) and zirconium titanate (ZrTiO₄) precursors. The effects of sintering temperature on phase formation, densification and dielectric responses of the ceramics have been investigated using XRD, SEM, EDX and dielectric measurement techniques. The densification of the PZT ceramics with density of 97% theoretical density can be achieved with appropriate sintering condition without any sintering additives. The optimized sintering condition has been identified as 1225°C for 4 h. More importantly, the dielectric properties are found to improve with increasing sintering temperature and grain size. However, when sintered over 1250°C, the dielectric properties of the ceramics are seen to deteriorate as a result of PbO vaporization, ZrO₂ segregations and porosity.

Nanocrystalline NiAl powder was prepared by mechanical alloying. The prepared powder was cold compacted and sintered at different temperatures and times. The crystallite size of green and sintered compacts was estimated from X-Ray Diffraction peak profile analysis. Thereafter, the Generalized Parabolic Grain Growth model and Master Sintering Curve concept based on Combined Stage Sintering model were employed to investigate the grain growth and densification behavior of nanocrystalline NiAl powder during sintering, respectively. The results of modeling were in a very good agreement to that of experiment. Finally, by comparing the modeling results the sintering parameters were optimized.

In this work, a composite composed of $\beta$-Sialon (Z=4) and ZrN has been fabricated by a two-step gas-pressure sintering method, and the effects of ZrN content and applied pressure on the phase behavior, densification and mechanical properties have been investigated. The phase behaviors were mainly dependent on the ZrN content and the applied pressure. The composites composed of $\beta$-Sialon (Z=4), ZrN, 15R-Sialon (0.4 MPa) and 12H-Sialon (0.7 MPa) as major phases, with different intermediate phases depending on the ZrN content. It is revealed that with the two-step sintering technique, a higher applied gas pressure has a positive effect on mass loss, and significantly improved the mechanical properties. The addition of ZrN particles greatly helped the densification behavior, reduced the mass loss, and increased fracture toughness of the composites, but decreased hardness due to formation of intermediate phases and grain coarsening. The addition of ZrN increased the fracture toughness due to the toughening mechanisms of crack branching, crack deflection and crack bridging.

Ferroelectric PbZr_0.6Ti_0.4O₃ (PZT) thick films were fabricated using a combination of screen-printing method and PZT precursor sol coating process (M. Koch, N. Harris, R. Maas, A. G. R. Evans, N. M. White and A. Brunnschweiler, Meas. Sci. Technol.8 (1997) 49; Y. S. Yoon, J. Korean. Phys. Soc.47 (2005) 321). Structural and electrical properties of the PZT thick films with the treatment of sol coating were investigated. The porosity decreased and the densification was enhanced with increasing the number of sol coatings. All PZT thick films showed the typical X-ray diffraction patterns of a perovskite polycrystalline structure. The thickness of all thick films was approximately 60–61 μm. The relative dielectric constant increased and dielectric loss decreased with increasing the number of sol coatings, and the values of the six-layer PZT-6 film were 167.8, 0.78% at 1 kHz, respectively. The remanent polarization and coercive field of the 6-coated PZT-6 thick films were 14.1 μC/cm² and 20.3 kV/cm, respectively.

Dielectric properties of ferrite ceramics have been less reported than their magnetic properties. Our recent study indicated that ferrite ceramics with very low dielectric loss tangent can be developed by using appropriate sintering aids, together with the optimization of other sintering parameters such as sintering temperature and time duration. Among various candidates of sintering aids, Bi₂O₃ is the most promising one. It is important to find that the optimized concentration of sintering aid for full densification is not sufficient to achieve lowest dielectric loss tangent. This short review was aimed to summarize the understanding in microstructural evolution, grain growth, densification and dielectric properties of ferrite ceramics as a function of sintering aid concentration and sintering parameters, which could be used as a guidance to develop ferrite ceramics with low dielectric loss tangents for various applications.

Applications involving processing of biomass feedstocks have increased significantly in recent years. Reliable storage and handling of biomass are critical for the success of these applications. Given the potential flow issues associated with inadequately designed biomass handling and processing equipment, severe consequences could occur to the process reliability and efficiency. Thus, a thorough understanding of the flow behavior of the given biomass feedstock and the use of this information in the design of storage, handling, and processing systems are essential. Flow behavior of bulk solids is a complex phenomenon. Multiple parameters associated with bulk solids flow need to be characterized and studied to obtain a complete understanding. In addition, effects of environmental conditions, process, and operation-related parameters on the flow behavior also need to be studied. This chapter introduces the basic principles and methods used for characterizing the flow behavior of bulk solids, with an emphasis on herbaceous biomass feedstocks. Then, illustration is provided about how to use this information obtained from characterizing flow behavior in design for handling equipment for pelletization of biomass feedstocks. Finally, principles associated with good project management are also discussed.

Crop harvest leaves behind agricultural waste with a significant amount of moisture content. Transporting high moisture agriculture waste biomass to a biorefinery is highly uneconomical. Achieving dry biomass (<10%) for subsequent thermochemical processing such as pyrolysis or gasification is cost-intensive. Hydrothermal liquefaction (HTL) technology is more suited for agricultural waste conversion because it can accept high moisture feedstock to produce biofuels and bioproducts. HTL technology has demonstrated many more advantages over other thermochemical technologies at the laboratory scale. Yet, there is no commercial HTL plant to process agricultural residue or lignocellulosic biomass. Transporting wet biomass and making it HTL-ready are the two significant obstacles to commercializing the HTL technology. Biomass densification may reduce the transportation cost and allow processability at higher biomass loadings. Although densification via pelletization has been reported in the literature, currently, there is no understanding of the influence of densified biomass on HTL product distribution or yield. This chapter covers essential information on HTL technology, reported yields of bioproducts (bio-oil and hydrochar), and the parameters to consider in configuring an HTL-ready feedstock with emphasis on corn stover feedstock densification.

Lignocellulosic biomass is the most abundant cheap resource produced from agriculture and forest residues. Among several thermochemical pretreatments reported in the literature, Ammonia Fiber Expansion (AFEX) pretreatment uses ammonia that can be recovered and re-used benefiting the environment. Ammonia helps open up the complex cell wall by cleaving the ester linkages and increasing the digestibility during enzyme hydrolysis and rumen in the animal gut. The lignin solubilized by ammonia during AFEX pretreatment is partially relocated to the surface of the biomass, while it is released to act as a natural binding when densifying the biomass. The AFEX pellets have a bulk density comparable to corn, can be stored in grain elevators, and can be used for diverse applications, such as feedstock for biofuels, animal feed, anaerobic digestion, and producing biocomposite materials. A local biomass pretreatment depot (LBPD) will help produce the AFEX pellets near the location where the feedstocks are produced and transported using trucks or rail carts. This approach will help overcome the logistic issues of transporting and storing biomass and sold as a commodity product that will enable the biochemical platform and biobased economy.

Lignocellulosic biomass (LCB) represents abundant biomass that is economically feasible and environmentally sustainable to produce biofuels and bioproducts. Despite these lucrative advantages, LCB faces logistical and technological challenges in its utilization. Low bulk density and high moisture content hinder the biomass’s efficient transportation and storage. Densification has become an essential step for efficient transport, storage, and utilization of biomass, pelletization being one of the most common densification methods. Pellets (and other densification techniques) have been studied in great detail for the thermochemical conversion of biomass. However, the extent of knowledge of its effect on sugar yields during biochemical conversions is limited. This chapter summarizes the densification methods used for biomass for biochemical conversion and their possible merits and limitations.

The effect of adding sintering aids (either Cr and C or Cr₃C₂) during the pressureless sintering process of titanium boride (TiB₂) ceramics was investigated and the effects from microstructural and compositional viewpoints discussed. The addition of either Cr and C or Cr₃C₂ as sintering aids accelerated the densification of TiB₂ significantly. Simultaneous addition of 7.5 wt.% Cr and C or Cr₃C₂ resulted in high density, high bending strength, and high Vickers hardness. According to the X-ray diffraction data of TiB₂ composites fired at 1173 to 2173 K, Cr and C or Cr₃C₂ reacted with TiB₂ to form CrB and TiC at the grain boundaries of TiB₂ during the sintering process. Also, we recognized a solid solution between TiB₂ and the sintering aid. SEM micrograph observation supported the observation that a liquid phase was definitely present during the sintering of TiB₂.