Uniaxial Pressing Research Articles

Investigation of the Compressibility and Compactibility of Titanate Nanotube-API Composites.

The present work aims to reveal the pharma-industrial benefits of the use of hydrothermally synthesised titanate nanotube (TNT) carriers in the manufacturing of nano-sized active pharmaceutical ingredients (APIs). Based on this purpose, the compressibility and compactibility of various APIs (diltiazem hydrochloride, diclofenac sodium, atenolol and hydrochlorothiazide) and their 1:1 composites formed with TNTs were investigated in a comparative study, using a Lloyd 6000R uniaxial press instrumented with a force gauge and a linear variable differential transformer extensometer. The tablet compression was performed without the use of any excipients, thus providing the precise energetic characterisation of the materials’ behaviour under pressure. In addition to the powder functionality test, the post-compressional properties of the tablets were also determined and evaluated. The results of the energetic analysis demonstrated that the use of TNTs as drug carriers is beneficial in every step of the tabletting process: besides providing better flowability and more favourable particle rearrangement, it highly decreases the elastic recovery of the APIs and results in ideal plastic deformation. Moreover, the post-compressional properties of the TNT–API composites were found to be exceptional (e.g., great tablet hardness and tensile strength), affirming the above results and proving the potential in the use of TNT carriers for drug manufacturing.

Effect of Sm and Na substitution on dielectric properties of SrBi4Ti4O15

The synthesis, characterisation, density and dielectric properties of Sm and Na substituted SrBi4Ti4O15 (SBT) piezoelectric ceramics are systematically studied for possible applications at high temperatures. The existing piezoceramics have temperature limitations. Samarium (Sm) and Sodium (Na) modified Strontium bismuth titanate Sr1-x SmxNaxBi4Ti4O15 (SSNBT-Strontium Samarium Sodium Bismuth Titanate) where x = 0.1, 0.2, 0.3 ceramics are prepared by solid state double sintering method using planetary ball mill for 10 hours duration in presence of Acetone media. Single phase is formed after calcination at 800 °C for 2 hours. Pellets are made with 1 cm diameter and 1 mm thickness using uniaxial Hydraulic press at 5 tonnes/cm2 pressure. All the samples are sintered at 1160 °C for 2 hours. The entire calcination and sintering processes are done in a programmable furnace. Orthorhombic structure of compound is confirmed by XRD analysis. The lattice parameters were calculated and experimental density was found to be around 95% of theoretical density. Tolerance factor decreased with increasing concentration of Sm, Na. The plate-like structure of grains is observed using SEM images and orientation of grains is random. Dielectric properties are reported as a function of temperature at different frequencies. The Curie temperature (Tc) of SBT is enhanced by substitution of Sm and Na in place of Strontium making this material a useful piezoceramic for high temperatures applications.

Extrusion of Al-Si alloy compacts under conventional conditions and in the semi-solid state

.In this research work the results of hot extrusion process of aluminium alloy compacts conducted at the temperature of conventional hot extrusion as well as at the temperature range corresponding to the semi-solid state were presented. Initial material was prepared by uniaxial pressing of Al17Si5Fe3Cu1.1Mg0.6Zr alloy powder. The extrusion process was carried out under isothermal conditions, and the temperature stability was strictly controlled. The changes of extrusion force in relation to punch displacement were recorded during hot deformation to demonstrate the effects associated with the appearance of the liquid phase in the volume of the processed material. After extrusion the samples were cooled in water as well as at room temperature. The influence of temperature of extrusion and the resulting fraction of the liquid phase in the processed material on its microstructure and chosen mechanical properties were determined. Mechanical properties of the examined alloy after deformation were carried out by measuring the hardness and in uniaxial compression tests. Additionally, one of the compacts was remelted and cast, what made possible comparison of the microstructure and chosen properties of the obtained products. In the result of the investigations it has been proved, that extrusion in semi-sold state results in reduction of forces necessary to complete deformation process and leads to obtaining the material with good mechanical properties and fine-grained, favourable microstructure.

Processing and properties of dense cordierite ceramics obtained through solid-state reaction and pressure-less sintering

ABSTRACTSintering of pure cordierite 2MgO:2Al2O3:5SiO2, and cordierite with the addition of 5 mass % TeO2 was studied. Green bodies were prepared from powder mixtures mechanically activated in a high-energy planetary mill, shaped by uniaxial (20 MPa) and cold isostatic pressing (1000 MPa). The pressure-less sintering of these specimens was performed at 1350°C for 1 h. High relative density over 95% of the theoretical value was obtained through solid-state reaction and pressure-less sintering of powder activated for 40 min, and for the first time reported in the literature. Phase composition and microstructures of sintered samples were determined by XRD and SEM, coupled with EDS mapping. The real part of the complex relative permittivity of the samples was measured at 200 MHz. The loss tangent of all samples was below the resolution of the measurement setup. A strong correlation between the relative permittivity and the density agrees with previously published data.

Enhancement in magnetostrictive properties of cobalt ferrite by magnetic field assisted compaction technique

Sintered polycrystalline cobalt ferrite is a potential magnetostrictive material for torque sensor application. Significant enhancement in magnetostriction of cobalt ferrite by magnetic field assisted compaction has been reported. Nano crystalline cobalt ferrite powder was prepared by combustion synthesis method using glycine as fuel. Phase pure cobalt ferrite powder was pressed into cylindrical pellets at an applied pressure of 200 MPa using a uniaxial hydraulic press with and without magnetic field of 1 Tesla. The green pellets were sintered at 1350 °C for 12 h which resulted in sintered pellets with ∼85% of the theoretical density. The SEM micrographs of the sintered pellets revealed the microstructure to be composed of grains with average size of ∼4 μm. EBSD analysis showed that significant change in texture of cobalt ferrite has not been observed in the sample compacted in presence of magnetic field. Maximum magnetizations of 70.2 emu/g and 69.8 emu/g were observed for cobalt ferrite processed with and without magnetic field pressing, respectively. A significant enhancement in magnetostriction, (195 ppm–325 ppm) ∼65% and strain sensitivity, 35% (1.3 × 10−9 m/A to 1.8 × 10−9 m/A) have been observed for the sample pressed under magnetic field than the sample pressed without magnetic field.

On the Densification Kinetics of Metallic Powders Under Hot Uniaxial Pressing

A new model undertaking the densification kinetics of uniaxially pressed metallic powders at constant temperature is proposed. This model is developed according to the power law of creep, and the expression of the ‘net pressure’ derived by the authors in a previous work. This net pressure describes the ‘geometrical hardening’ experienced by the powder mass, during compression. In order to validated the model three different powders were uniaxially pressed, aluminium, tin and lead, being obtained data from hot compaction experiments. The similarity between the model predicted curves and the experimental data is quite acceptable. In addition, the goodness of the model is contrasted with two other theoretical models addressing the same problem. The approach developed can be useful to model hot uniaxial pressing and electrical consolidation processes, which start with loose powders, i.e., not previously cold compacted powders.

Equimolar Yttria-Stabilized Zirconia and Samaria-Doped Ceria Solid Solutions

Compositions of (ZrO2)0.92(Y2O3)0.08 (zirconia: 8 mol % yttria—8YSZ) and (CeO2)0.8(Sm2O3)0.2 (ceria: 20 mol % samaria—SDC20) ceramic powders were prepared by attrition milling to form an equimolar powder mixture, followed by uniaxial and isostatic pressing. The pellets were quenched to room temperature from 1200 °C, 1300 °C, 1400 °C and 1500 °C to freeze the defects configuration attained at those temperatures. X-ray diffraction analyses, performed in all quenched pellets, show the evolution of the two (8YSZ and SDC20) cubic fluorite structural phases to a single phase at 1500 °C, identified by Rietveld analysis as a tetragonal phase. Impedance spectroscopy analyses were carried out in pellets either quenched or slowly cooled from 1500 °C. Heating the quenched pellets to 1000 °C decreases the electrical resistivity while it increases in the slowly cooled pellets; the decrease is ascribed to annealing of defects created by lattice micro-tensions during quenching while the increase to partial destabilization of the tetragonal phase.

Effect of plasma sintering on densification and oxygen content of beryllium powder

Beryllium has attracted a great attention as multiplier in fusion reactors and moderator and reflector in fission reactors.The use of plasma-sintering method has been suggested as a way to fabricate beryllium specimens which have similar properties with those produced by conventional methods (e.g., hot pressing and hot isostatic pressing).In general, the plasma-sintering process (PSP but also known as spark plasma sintering, SPS, or pulsed electric current sintering - PECS) consists of applying uniaxial pressure and pulsed current. It is considered that the pulsed current activates particle surfaces and eliminates impurities prior to a common thermomechanical treatment. However, only scarce information on its effect from the viewpoints of its contribution to densification by uniaxial pressing and oxygen content is available and verification of its effect is still needed for pure beryllium. Since the plasma activation could be a useful process to eliminate the impurities by recycling of radioactive materials, its effect should be also taken into consideration.In this study, the influence of parameters of the pulsed current on compaction of beryllium powder and oxygen content of fabricated samples was investigated. The perspectives for the further use of PSP operation from the point of view of its influence on fabrication parameters and reprocessing of the beryllium-based radioactive waste are discussed in the final part of this paper.

Comparative studies on synthesis and sintering studies of biologically derived hydroxyapatite from Capria hircus (Goat) and Bos primigenius (Bovine)

Hydroxyapatite (Ca10(PO4)6(OH)2, HAp) is a major constituent of bone graft materials and has been widely used for bio-medical applications due to its high surface-to-volume ratio, biomimetic morphologies and biocompatibility. Here HAp has been synthesized from naturally occurring biological specimens. In this study HAp has been obtained from Capria hircus(Goat) and Bos primigenius(Bovine). These obtained bones were washed using distilled water and 1M NaOH solution. The washed bones were allowed for some pre heat treatments. The bones were crushed using mortar pestle and ball-milled. The obtained bone powders were calcinated at 800 °C. The phase compositions of the samples were studied using X-ray diffraction studies (XRD), Scanning Electron Microscope (SEM) and Fourier-Transform Infrared Spectroscopy (FT-IR). The thermal analysis of the samples was also studied using Thermo gravimetric analysis (TGA-DTA). The synthesized powders were compacted using uniaxial hydraulic press into 10 mm diameter pellets. The pellets were then sintered at 1100 °C and 1200 °C. The density of the as dried pellets and sintered pellets were done. This study reveals that the pure HAp can be synthesized from bone-waste materials.

Synthesis of Ca–Co hydroxides and their use in facile fabrication of textured CayCoO2 thermoelectric ceramics

A brucite-type hydroxide of CazCo1−z(OH)2 with a high Ca content was synthesized and utilized as a single-source precursor for the fabrication of bulk ceramics of a semiconducting layered calcium cobaltite CayCoO2. Plate-like CazCo1−z(OH)2 particles with z up to 0.22 were reproducibly obtained by a reverse co-precipitation method using KOH as an alkaline source. Uniaxial pressing of the plate-like CazCo1−z(OH)2 particles (z = 0.22), which was calcined at 373 K beforehand, at a pressure as high as 500 MPa produced a highly dense green pellet where the plate-like particles were stacked along the pressing direction. The green pellet was then converted by a heat treatment at 923 K into an oxide ceramic of preferentially (010)-oriented CayCoO2 via a topotactic-like pyrolytic reaction maintaining edge-sharing CoO6 octahedra. Although the ceramic also contained a minor insulating Co3O4 phase (16.7 ± 0.7 mol% estimated from thermal analysis), the electrical measurements proved its p-type semiconducting behavior resulting from the CayCoO2 phase with enhanced Seebeck coefficient exceeding 160 μV/K at room temperature.

Structural, optical, and luminescence properties of ZnO:Ga optical scintillation ceramic

This paper discusses the characteristics of ZnO and ZnO:Ga ceramics fabricated by uniaxial hot pressing. The short-wavelength transmission limit of zinc oxide ceramics is in the 370-nm region; the long-wavelength limit is determined by the free-charge-carrier concentration and lies in the interval from 5 to 9 μm. The total transmittance of such ceramics in the visible and near-IR regions is about 70% when the sample is 0.5 mm thick. The luminescence spectrum is represented by a broad emission band with maximum at 580 nm, having a defect nature. The introduction of 0.03–0.1 mass % gallium into the zinc oxide structure inhibits grain growth and increases the free-charge-carrier concentration to 3.44×1019 cm−3. As the gallium concentration increases in the range 0.05–0.1 mass % in a ceramic of composition ZnO:Ga, the defect luminescence band is suppressed and a characteristic exciton luminescence is formed with a maximum corresponding to 389 nm and a damping time constant of 1.1 ns.

The Fabrication of Graphene-Reinforced Aluminum Composites by Powder Metallurgy and Uniaxial Pressing

This research studied the fabrication of graphene-reinforced aluminum composite via powder metallurgy and uniaxial pressing. The process started from mixing graphene with aluminum powder with various content of graphene (0.5, 1, 1.5, 2 and 4 wt.%) in acetone medium, followed by dispersion process at high frequency using an ultrasonic bath. The mixed composite powders were then formed into pellet and sintered at 600°C. The results showed that when graphene content in graphene reinforced aluminum composite is low (0.5wt.%, 1wt.% and 1.5wt.%), the hardness was enhanced. It was suspected that graphene could get into aluminum matrix and impede the grain growth of aluminum and dislocation movement. However, when excessive graphene content was added, graphene nanoplatelets tended to agglomerate, decreasing the hardness of composite. Similarly, the improvement of electrical and thermal conductivities was achieved with a low content of graphene. The well dispersion of graphene in aluminum matrix could facilitate the electron transport and to induce the pore reduction throughout the matrix.

Sintering of carbon nanotube-reinforced zirconia-toughened alumina composites prepared by uniaxial pressing and cold isostatic pressing

The effect of carbon nanotubes (CNTs) on hardness and fracture toughness in CNT-reinforced zirconia-toughened alumina (ZTA) composites prepared by uniaxial pressing (UP), cold isostatic pressing (CIP), and pressureless sintering (PLS) at 1520 °C in air during 1 h was investigated. Both pressing methods yielded nearly identical relative densities higher than 93%. The Vickers microhardness was increased in the composites treated by CIP, whereas the fracture toughness was decreased for the CIPed composites. This could be associated with the fracture mode and the toughening mechanisms present in the microstructure. CIPed ZTA composites with additions of 0.01 wt% MWCNTs obtained an increase in hardness of 26% and a decrease of 8% in fracture toughness compared to uniaxially pressed ones. From all studied composites, those with additions of MWCNTs yielded the better mechanical properties in comparison to composites with additions of SWCNTs, suggesting that MWCNTs are more easily dispersed into the ceramic matrix, thereby producing improvements as reinforcement agents.

EFFECT OF TIC AND B4C ON MECHANICAL PROPERTIES OF AA7075 ALLOY FABRICATED BY POWDER METALLURGY

In this work, aluminum metal matrix composites (AMMCs) were fabricated by usingpowder metallurgy. AA7075 powder is reinforced with two different ceramic particles(TiC,B4C) with different weight fractions (2.5, 5, 7.5 and 10 wt.%). The composites wereproduced by powder metallurgy by preparing the powder, mixing, compacting andsintering. The particle size of unreinforced AA7075 about 100μm, while particle size ofeach TiC and B4C about 150 μm. The mixing process was done by planetary mixing setuprotating at 250 rpm for 2hr. by adding zinc stearate as an activator material with steel ballmilling. However the mixture was compacted by hydraulic uniaxial press type (LeyboldHarris No.36110) about 200 kg/cm² according to (ASTM-D 618). After compactingprocess, the mixture sintered at 475 °C for 2hr. by using electrical furnace with argonatmosphere.There are many examinations and tests were carried out for the synthesized compositesmaterial (AA7075/ TiC and AA7075/ B4C) such as examination of the microstructure,mechanical tests such as hardness and compressive strength, physical tests such asdensity and porosity.The results of this work showed that improving in physical properties (theoreticaldensity, experimental density, porosity) and mechanical properties (Rockwell hardnessand Compressive strength)

Effects of Milling Speed and Sintering on the Formation of Akermanite (Ca2MgSi2O7) Bioceramics

The aim of the present work is to study the effect of different milling speeds on the preparation of akermanite ceramics. In this study, akermanite (Ca2MgSi2O7) was synthesized by high speed planetary ball milling and mixing method. Calcium oxide (CaO), magnesium oxide (MgO) and silicon dioxide (SiO2) were used as initial reactants. The starting materials were milled with molar ratio of 2:1:2, respectively, using ball-to-powder ratio 10:1 at different milling speeds of 300 rpm, 400 rpm and 500 rpm. After synthesis, the powders were pelletized to form pellets (13 mm) with 150 MPa by uniaxial pressing. The pellets were then sintered at 1250°C for 3h. Phase analysis by X-ray diffraction (XRD), surface morphology by Field Emission Scanning Electron Microscopy (FESEM), Brunauer-Emmet-Teller (BET) specific surface area analysis, linear shrinkage, porosity and density measurement were performed on the milled and sintered samples. It was found that milling at 500 rpm resulted in powder with largest surface area (108 m2/g), indicating the finest size of powder. FESEM observations showed that the sintered-akermanite ceramics from 500 rpm milling at 1250°C were the densest with microcrystalline appearance and clear grain boundaries, while milling at 300 rpm and 400 rpm showed some pores in the sintered samples.

Impact of pressure in static and dynamic pressing of ultrafine plasmochemical ZrO2 (Y)-Al2O3 powders on compact density and compaction efficiency during sintering

The effect of different methods of pretreatment and compacting of ultrafine alumina-zirconia powders of composition (in mass%): 20 Al2O3-80 (ZrO2-Y2O3) on densification processes during pressing and subsequent calcination has been studied. Ultrafine powders were prepared by plasma-chemical method. It was found that the initial nanocomposite is a mechanical mixture made up of zirconia nanoparticles and amorphous alumina in a thermodynamically nonequilibrium state. Grinding of powders did not affect their phase state. Powder compacts were produced by means of uniaxial static pressing and magnetic pulse compaction. The impact of mechanical processing of powders on ceramics density was studied. It was shown that dry grinding of powders in a planetary ball mill does not increase the ceramics density. The best and virtually identical results were obtained using preliminary static pressing of powders at increased pressure P = 900 MPa and their subsequent grinding in a ball mill. Dilatometric studies showed that double-action magnetic pulse compaction provides the maximum shrinkage rate at lower temperatures in comparison to that observed under static pressing. The ceramic density achieved is higher than that obtained using other pressing methods.

Application of grits waste as a renewable carbonate material in manufacturing wall tiles

This work focuses on the reuse of grits waste, from cellulose industry, as a raw material to replace traditional carbonate material in ceramic wall tiles. Wall tile formulations bearing up to 15 wt% of the grits waste were prepared for replacement of calcareous. The tile manufacturing route consisted of dry powder granulation, uniaxial pressing, and firing at temperatures ranging from 1100 °C to 1180 °C by using a fast-firing cycle. The wall tile specimens were tested to determine their physical and mechanical properties (linear shrinkage, water absorption, apparent porosity, apparent density, breaking strength, and flexural strength). The firing behavior, phase transformations, and microstructure were evaluated by dilatometry, XRD, and SEM. The results showed that the fired wall tile specimens are composed of anorthite and quartz, as major mineral phases, and mullite as a minor phase. It was found that the grits waste had a positive influence on the properties and microstructure of the wall tile specimens. The results also revealed that the grits waste from cellulose industry could be used as a total replacement of traditional calcareous material in wall tile formulations.

Sinterability of Magnesium Hydroxyapatite Bioceramic and Its Mechanical Properties

One of the most favoured material in bone tissue engineering field nowadays is hydroxyapatite (HA), which is also known to be bioactive and has a similar composition to human bone. However, developing an artificial bone or bone graft using biocompatible HA is a challenging task due to the lower strength of the main substance. To improve the mechanical properties of synthetic HA, introduction of metallic substance such as magnesium (Mg) into HA has been proposed. In this present study, 0, 10 15 wt% of magnesium hydroxyapatite (MgHA) nanopowders were prepared by a simple wet precipitation method. These nanopowders were then compacted using a 10-ton compression uniaxial press machine with 150 MPa pressure to form a disc shape of dense MgHA. After that, the MgHA discs were sintered at a temperature of 1000 °C and 1100 °C to remove the organic compounds and further densify the ceramics. XRD results showed that the crystallinity of MgHA increased when the sintering temperature increases. The compression test showed that the 10 wt% MgHA sample recorded the highest compressive strength (243.59 MPa) when sintered at 1100 °C, while pure HA has the lowest value with 49.37 MPa. This study also demonstrates that sintering temperature at 1100 °C gives significant improvement to the mechanical properties of the MgHA dense bodies compared to sintering at 1000 °C.

The Influence of Sintering Parameters in the Microstructure and Mechanical Properties of a Cu–Al–Ni–Mn–Zr Shape Memory Alloy

Shape memory alloys from the Cu–Al–Ni system arouse interest for industrial applications due to their high thermal stability and low cost. In this study, the Cu–11.8Al–3.2Ni–3Mn–0.5Zr alloy is prepared through a powder metallurgy processing technique. Specimens are produced by a conventional uniaxial press followed by sintering procedure under argon atmosphere. The sintering temperature is varied in the range from 950 to 1060 °C, whereas sintering time is varied from 0.5 to 2 h. The results denote that a temperature close to the alloy's solidus temperature is necessary to achieve higher densities. Moreover, martensite‐type microstructures are observed, despite the slow cooling rate applied after sintering. The compression strengths are in the order of 500 MPa with the exception of the specimens sintered for 1.5 h, which reaches an average of 700 MPa. This is explained by the lower porosity resulting from liquid phase sintering. The forward and reverse martensitic transformation temperatures, however, are quite similar for all examined conditions.

Structure, morphology and electrical transport properties of the Ti3AlC2 materials

A study of Ti3AlC2 materials prepared with Self Propagating High-Temperature Synthesis (SHS) method followed by uniaxial hot pressing (HP) is presented. Three groups of materials have been synthesized from different substrates using pure element and/or intermetallic powders. The SHS prepared powders and dense HP materials were characterized with x-ray diffraction and were found to contain more than 80% of the Ti3AlC2 MAX phase with anisotropic distribution of the crystallographic directions of its crystallites with respect to the HP pressure axis. This is accompanied with different mean size of the crystallites. The measured temperature dependencies of the electrical resistivity are consistent with those reported in the literature but show a higher R(300 K)/R(4 K) ratio of 3.5. They also exhibit slightly different values of thermal coefficient and residual resistivity between the materials studied. The magnetoresistance at 4 K and 300 K, investigated up to 35 kOe applied field, revealed a quadratic field dependence. The corresponding values of the electronic carrier density are found to be of 30% larger at 4 K than at 300 K and different between the materials studied. The results are discussed with respect to the Local Density of States calculations and compared with the resistivity and magnetoresistance data for others materials, like copper, and aluminum.