Uniform distribution of diamond grains is difficult to achieve using traditional fabrication of the micro grinding wheel. The design and performance of novel resinous diamond composites (RDCs) fabricated by hot pressing molding were studied to fabricate micro resinous diamond grinding wheels. The physical and mechanical properties of RDCs were analyzed by constructing and simulating five kinds of RDCs, including acrylonitrile butadiene styrene (ABS)/polyvinyl chloride (PVC)/dioctyl phthalate (DOP)/diamond materials with different mass ratios. Diamond grains presented good compatibility with the ABS–PVC–DOP copolymer, which resulted in improved mechanical properties of RDCs. RDC1–RDC5 samples were fabricated, and their hardness, surface roughness, and infrared spectra were analyzed. The optimal mass ratio of ABS/PVC/diamond/DOP for fabricating RDCs was 62.5/18.6/10.6/8.3. The results provide guidance in fabricating novel materials for resinous diamond grinding wheels with desirable performances for precision and ultraprecision machining.

Pseudo-α or near-α titanium alloys are being widely used in the power generation industry due to their stability at high temperature service, good mechanical characteristics and corrosion resistance. Particularly Ti-6% Al-1.5% V-1.0Mo-0.5% Zr-0.1% C alloy is mainly used in turbines components, heat exchangers and pipes for steam conduction, among others; these are subjected to critical conditions of temperature, abrasion and corrosive environments. A good performance of such devices depends on the chemistry and of the material processing story.

Effects on microstructure and wear resistance with the addition of Ru and small variation of V and Mo amounts in the Ti-6% Al-1.5% V-1.0Mo-0.5% Zr-0.1% C alloy were analyzed. Three different alloys were melted in a vacuum induction furnace with a cooled copper skull under an argon protective atmosphere for this study

Four alloys were melted “Alloy 1” Ti-6% Al-1.5% V-1.0Mo-0.5% Zr-0.1% C-0.3% Ru, “Alloy 2” Ti-6%Al-0.5%V-1.6%Mo-0.5%Zr-0.1% C-0.3% Ru, “Alloy 3” Ti-6%Al-2.2%V-0.5%Mo-0.5%Zr-0.1%C-0.3%Ru. After melting, all alloys were homogenized at 1200°C for two hours, followed by hot rolling above β transition temperature with a reduction of 50% in thickness.

All alloys were analyzed by using scanning electron microscopy (SEM) and Vickers Micro hardness (HV). Results shown that Mo and V variations modified the micro hardness by microstructure refinement. In contrast, the addition of Ru showed no microstructure modification.

Microwave synthesis of Copper Zinc Tin Sulphide (CZTS) sphere like particles has been demonstrated. The structural and morphological properties of CZTS particles are characterized by XRD, SEM and Raman spectroscopy and subsequently thermoelectric properties are investigated. XRD results of prepared powder sample matches well with tetragonal crystal structure of CZTS bulk. No other impurity phase has been detected from the XRD analysis. Raman spectrum further confirms the formation of single phase CZTS with characteristics peak for CZTS at 334.1 cm-1. SEM studies reveal that the CZTS particles are spherical in shape with uniform sizes of ∼ 250-350 nm. Hot pressed CZTS system shows a power factor ∼21 µW/mK2 and ZT∼ 0.024 at 623 K. Significant enhancement in the Figure of merit for CZTS system is observed in comparison to reported nanostructures of the same system may be due to increased electrical conductivity.

Highly porous and fully crystalline mullite fiber compacts were fabricated by uniaxial hot pressing of stacked short-fiber mats without binders or sintering aids. The special feature of this new fabrication method is the use of MAFTEC® organic bound mat (OBM) type fiber mats consisting of semicrystalline “MLS-2” short fibers. In contrast to conventional polycrystalline mullite fibers, semicrystalline MLS-2 fibers consist of amorphous silica and nanoscale transitional alumina. Due to this special microstructure, MLS-2 fibers are less prone to fiber breakage upon shear load and therefore can well withstand pressure-assisted consolidation. Hot pressing of stacked OBM to highly porous fiber compacts is facilitated by the thermally driven softening of amorphous silica above 900 °C; favorable deformation and consolidation rates are achieved above 1050 °C. Above 1250 °C the mullite is crystallized at the expense of amorphous silica and simultaneously both deformation and consolidation comes to an end. Obtained MAFTEC OBM-derived fiber compacts consist only of crystalline mullites, and therefore mechanical properties are favorably retained at high temperatures.

New emergent materials of novel electromagnetic properties are discussed, based primarily on our recent works. The use of pressure effects in terms of self oxidization, inner compression and pure doping in discovering new emergent materials is highlighted. Materials addressed include (I) new correlated oxides such as high-T c cuprate superconductors; (II) new intermetallic materials such as diluted magnetic semiconductors with independent spin & charge doping; the “111” type iron based superconducting systems; (III) compounds with strong spin orbit coupling, such as itinerant ferromagnetic ruthenates etc.

Hot deformation characteristics of 2304 duplex stainless steel were analyzed by hot compression tests at temperature range of 850–1150 °C and strain rates of 0.001–1 s−1. The flow curves at low temperatures and high strain rates were suggesting sluggish dynamic recovery (DRV) in ferrite and partial dynamic recrystallization (DRX) in austenite. However, at high temperatures and low strain rates, the flow curves showed implied the domination of DRV in ferrite. The hyperbolic sine equation with activation energy of 508 kJ/mol could relate the processing parameters. Microstructural observations showed that DRV in ferrite is the controlling mechanism at all deformation conditions. However, at high temperatures and strain rates partial DRX could also occur in austenite. Based on the law of mixture and Baragar’s equations a modified model was proposed to consider work hardening and dynamic softening in the constituents. The model could satisfactorily predict the flow curves at different deformation regimes.

Single- and double-hit hot compression tests were performed at 1030 °C and strain rate of 0.1 s−1 on Ti–13V–11Cr–3Al beta Ti alloy to investigate the flow behavior and mechanism of microstructural evolution during the interpass period. It was observed that the flow stress level and the extent of yield point phenomena (YPP) were increased by an increase in the grain size. After the first pass, the microstructure was bimodal of large deformed grains and small recrystallized grains formed by continuous dynamic recrystallization. The increase in the interpass time to 100 s, led to the decrease in the yield drop and extent of YPP. However, the further increase in the interpass time to 300 s would result in an inverse effect. A combination between static recrystallization and metadynamic recrystallization was found responsible for grain refinement in the samples subjected to the interpass times below 100 s. At longer interpass times, i.e., 300 s, grain growth increased the average grain size.

The high-temperature flow behavior and flow stress sensitivity of BT25y alloy were investigated. Results show that hot deformation is accompanied by the dynamic competition between work hardening and flow softening. The strain rate sensitivity exponent m tends to decrease with the strain rate after a first rise, and reaches the maximum at strain rate of 0.1 s−1. There is a large temperature range exhibiting m values above 0.2 at strain rates of 0.01–0.1 s−1. The temperature sensitivity exponent s shows an overall dropping trend with elevated temperature. The strain hardening exponent n first decreases and then increases with the strain at strain rate of 0.01 s−1. Large positive n values lie in areas with high strain rate, and small negative n values are located in areas with lower temperature and small strain rate. Secondary lamellar α appears near the phase transition temperature. The microstructure presents elongated characteristics at high strain rate.

The influence of temperature and strain rate on hot deformation behavior and microstructure of Cu–10Ni–3Al–0.8Si alloy was investigated. The true stress increased rapidly initially until it approached the peak values. The peak value of true stress and the Zener–Hollomon parameter decreased with the increase of temperature and the decrease of strain rate. The thermal activation energy of the alloy was about 396.57 kJ/mol, the processing map was established and the appropriate compression temperature was between 900 and 950 °C. The 〈001〉 and 〈011〉 fiber texture was the main type of texture. The increase of temperature or strain rate accelerated the formation of 〈001〉 fiber texture. Dynamic recrystallization nucleated and deformation bands formed at 750 °C. Recrystallization was accelerated with the increase of temperature and the decrease of Zener–Hollomon parameter. Both continuous recrystallization resulting from dynamic recovery and dynamic discontinuous recrystallization were softening mechanisms.

Hot compression tests on pure Ni and Ni–30Cu at 950–1150 °C and strain rates of 0.001–1 s−1 were performed to identify the physical interpretation of the apparent activation energy (Qd). For pure Ni, Qd was constant and identical to that of the self-diffusion. However, for Ni–30Cu, it decreased steadily with strain. The value of Qd was separated into thermal and mechanical parts. The thermal part was necessary to propel diffusion. For pure Ni, the mechanical part was zero at low and medium strain rates of 0.001–0.1 s−1 and the self-diffusion was the controlling mechanism. However, at 1 s−1, both the thermal and mechanical parts were needed to provide Qd. For Ni–30Cu, Qd was greater than that for the interdiffusion of Ni and Cu. The value of mechanical part decreased with increasing temperature and strain rate. Although the thermal parts for pure Ni and Ni–30Cu were nearly identical, the mechanical part for the latter was considerably higher. The difference was attributed to the strengthening effect of Cu atoms and the sluggish dynamic softening with respect to pure Ni.

The effect of applied pressure on reactive hot pressing (RHP) of zirconium (Zr):graphite (C) in molar ratios of 1:0.5, 1:0.67, 1:0.8, and 1:1 was studied at 1200 °C for 60 min. The relative density achievable increased with increasing pressure and ranged from 99% at 4 MPa for ZrC0.5 to 93% for stoichiometric ZrC at 100 MPa. The diminishing influence of pressure on the final density with increasing stoichiometry is attributed to two causes: the decreasing initial volume fraction of the plastically deforming Zr metal which leads to the earlier formation of a contiguous, stress shielding carbide skeleton and the larger molar volume shrinkage during reaction which leads to pore formation in the final stages. A numerical model of the creep densification of a dynamically evolving microstructure predicts densities that are consistent with observations and confirm that the availability of a soft metal is primarily responsible for the achievement of such elevated densification during RHP. The ability to densify nonstoichiometric compositions like ZrC0.5 at pressures as low as 4 MPa offers an alternate route to fabricating dense nonstoichiometric carbides.

EURO-GANEX aims to recycle both major and minor actinides. As the final waste composition is free from actinides, adapted immobilization matrices should be developed. Synroc is a potential wasteform that has proven itself to be efficient in immobilizing high-level wastes (HLW). In this study, a new composition of Synroc, Synroc-Z, is designed and characterized. The key modification is in decreasing the amount of zirconolite phase, which is the main host phase for actinides and increasing the amount of other phases (hollandite and perovskite). As designed the obtained amount of zirconolite is lower than in Synroc-C compositions. Synroc-Z samples were synthesized with a waste loading of 20 wt.% at various temperatures and pressures via hot-pressing to determine the optimum process parameters, which were determined to be 1150-1200°C and 20 MPa, respectively.

Porous ceramics have been widely used under extreme environments due to their high strength, good thermal shock resistance, and excellent corrosion resistance. Recently, silicon aluminum oxynitride (SiAlON) ceramic, a solid solution of Si3N4 with AlN, SiO2, and Al2O3, attracted our interest because of its superior mechanical and physical properties for applications under extreme environments (i.e., high temperature, high pressure, excellent mechanical wear, and low PH). However, in spite of its many unique properties, porous SiAlON production has not been scaled up sufficiently to meet industrially relevant quantities due to its high synthesis cost and the difficulty of manufacturing articles. Here, we report on a scalable two-step carbothermal reduction and nitridation (CRN) method to synthesize mechanically robust SiAlON ceramic materials with controlled porosity levels. The morphologies and chemical composition of the synthesized porous SiAlON ceramics were characterized using SEM, XRD, EDAX, and microprobe analysis. In addition, the flexural strength of the engineered porous SiAlON ceramics is also reported in this paper.

Hot compression tests were carried out on the duplex α + β leaded brass CuZn39Pb3 in temperature range of 600–800 °C and at strain rates of 0.001–1 s−1. A self-consistent model was used to analyze the flow behavior of the constituents and the material. A linear viscoplastic model was used to relate the flow stress of β and α + β composite to strain rate and the corresponding viscosity parameters were calculated at various deformation conditions. Using the viscosity parameters of β and α + β and the volume fractions of the constituents, the viscosity parameter of α was calculated. The values of the viscosity-like parameters and strain rate sensitivity for β and α + β composite were calculated using the nonlinear powerlaw viscoplastic equation. The results showed that the flow stress of α calculated using the self-consistent model was considerably higher than that of β. The difference could be attributed to the lower Zn content in α. The flow stress of α + β composite was calculated using the law of mixture rule. The law of mixture modeling of α + β composite for the iso-strain condition resulted to the overestimation of flow stress. The difference between the experimental and predicted results was attribute to the strain partitioning between α and β.

A model of reactive hot pressing of zirconium carbide (ZrCx, 0.5 < x < 1) has been constructed that incorporates four processes that occur in parallel: creep of zirconium (Zr), reaction of Zr and carbon (C), increase in volume fraction of hard phase with progressive reaction that reduces the creep of Zr and, finally, de-densification associated with volume reduction during reaction. The reasonable agreement of the model with experimental results verifies that plastic deformation of Zr is the main factor that is responsible for the low-temperature reactive densification of ZrC and that ZrC may be treated as a rigid inclusion that contributes little to densification. It predicts that densification is impaired by increasing carbon stoichiometry due to the increasing amount of starting hard phase and the greater contraction upon reaction. Additionally, the model predicts that mixtures of Zr and ZrC should show equal or better densification than Zr and C mixtures.

The aim of this research was to work out the technology of ceramics for finding optimal sintering temperatures and to study their mechanical properties. Samples were prepared from powders with different volumetric ratio of the components. The powders underwent a prolonged co-milling in a vibratory mill, followed by uniaxial pressing, cold isostatic pressing (CIP) and pressureless sintering in a vacuum furnace under an argon atmosphere. Hot pressing (HP) was applied to some powder formulations. This study showed that it is advisable to carry out the first stage of the heat treatment up to 1550 ̊C under vacuum, with the aim of refining the grain surface from the oxygen-containing impurities due to their dissociation and evaporation. The studied area of formulations has a very narrow range of sintering (1940-1945 ̊C). It was established that the sinterability of the materials is affected by the amount of silicon carbide in the ternary system. Under pressureless sintering, the relative density of the material directly depended on the volume fraction of SiC. However, a change in the concentration of B4C had no appreciable effect on the sinterability of the materials. The application of HP helped us to reduce the negative impact of large amounts of SiC. Under HP at temperatures close to Teut, a certain decompaction of materials was observed with a significant amount of B4C (3-5% loss in density).

Nearly dense and almost single-phase bulk (Cr1–xVx)2AlC (x = 0, 0.25, 0.5, 0.75, and 1.0) ceramics were successfully fabricated by in situ hot-pressing method using Cr, V, Al, and C powders as raw materials. A possible synthesis mechanism was proposed to explain the formation of (Cr1–xVx)2AlC solid solutions. The lattice parameters, microstructure, and mechanical properties of the (Cr1–xVx)2AlC ceramics were investigated in detail. The results indicated that the lattice parameters increased with the substitution of Cr by V and the aspect ratio of the grain changed from 1.4 to 3.2. The dependence of the mechanical properties on the V content was a single-peak type. The (Cr0.5V0.5)2AlC ceramic possessed the optimal mechanical performance and its Vickers hardness, flexural strength, and fracture toughness reached the maximum values of 5.18 GPa, 402 MPa, 5.91 MPa m1/2, respectively, due to the solid solution effect. The energy-consuming mechanisms of the material were also discussed.

Fully dense (Ti,Mo)2AlC/Al2O3 in situ composites with high purity were successfully synthesized at 1350 °C by reactive hot pressing of the Ti, Al, TiC, and MoO3 powder mixtures. The effect of MoO3 content on the phase composition, microstructure, and mechanical properties was investigated in detail. The introduction of the Al–MoO3 displacement reaction into the Ti–Al–TiC system resulted in a submicron grain size and a homogeneously distributed matrix phase of (Ti,Mo)2AlC with a secondary Al2O3 phase. The matrix grain size was significantly refined with increasing the Al2O3 content. Compared with the sample without MoO3 addition, the addition of 13.81 wt% MoO3 (corresponding to 10 wt% Al2O3 formation) evidently enhanced the hardness, flexural strength, and fracture toughness by 25%, 69%, and 146%, respectively. The strengthening and toughening mechanisms for the (Ti,Mo)2AlC/Al2O3 composites were also investigated.

A molecular dynamics simulation was performed to study the polymer filling process in nanoimprint lithography for a bi-layered resist. The bi-layered resist consisted of PMMA resins with different molecular weights. When the mold cavity size became smaller than the polymer size of the top layer resist, the required force to fill the cavity became large. The molecular weight of the top layer dominated the filling characteristics in the bi-layered resist process.

We fabricated Cu2ZnSn(SxSe1-x)4 (CZTSSe) solar cells by a printing and high-pressure sintering (PHS) process. First, the CZTSSe solid solution powders were synthesized by heating the elemental mixtures at 550oC for 5 h in an N2 gas atmosphere. We fabricated CZTSSe films by a printing and high-pressure sintering (PHS) process. The obtained dense CZTSSe film was post-annealed at 550oC for 10 min under an N2 +5% H2S gas atmosphere. We fabricated CZTSSe solar cells with the device structure of Ag/ITO/i-ZnO/CdS/CZTSSe/Mo/soda-lime glass. The CZTSSe solar cell showed an efficiency of 2.1%, with Voc of 272 mV, Jsc of 18.0 mA/cm2 and FF of 0.44.