Diametral Compressive Strength Research Articles

Assessment of the correlation between the tensile and diametrical compression strengths of 3D-printed denture base resin reinforced with ZrO2 nanoparticles

Background: The mechanical properties of 3D-printed denture base resins are crucial factors for determining the quality and performance of dentures inside a patient’s mouth. Tensile strength and diametral compressive strength are two properties that could play significant roles in assessing the suitability of a material. Although they measure different aspects of material behavior, a conceptual link exists between them in terms of overall material strength and resilience. Aim: This study aims to investigate the correlation between tensile strength and diametral compressive strength after incorporating 2% ZrO2 nanoparticles (NPs) by weight into 3D-printed denture base resin. Methods: A total of 40 specimens (20 dumbbell-shaped and 20 disc-shaped) were produced via 3D printing and divided into two groups (n = 10): (1) 3D-printed denture base resin without NPs and (2) the resin was strengthened with 2% by weight ZrO2 NPs. Tensile strength and diametral compressive strength were assessed using a universal testing machine. Results: A detrimental relationship was observed between the tensile strength and diametral compressive strength of 3D-printed denture base resin after the addition of NPs. Conclusion: The enhancement of one property does not necessarily mean the enhancement of another. Caution should be taken to not endanger the quality of a material.

Silica fume activated by NaOH and KOH in cement mortars: Rheological and mechanical study

Ordinary Portland cement (OPC) is the most used binder in the world, applied in practically all phases of the building. The problem is that this binder is highly harmful to the environment due to its production stage, which involves clinkerization by burning limestone. In this context, the objective of this work was to evaluate the potential of using silica fume as a partial substitute for cement, however verifying its activation potential. Silica fume is widely used as a pozzolanic material. In this work, the use of the material as alkali cement activated with sodium and potassium hydroxide (NaOH and KOH) was tested. The methods used consist of producing mortars in the compositions 1:3:0.60 (OPC: natural sand: water) and replacing the OPC with silica fume (10 and 20%) in three ways: i) without activation, as a pozzolanic material; (ii) activated by NaOH; and (iii) activated by KOH. Cylindrical specimens measuring 50x100 cm were produced, containing 0, 10 and 20% silica fume replacing OPC. Properties were evaluated in the fresh state, such as depth of penetration, consistency and squeeze flow, and tests in the hardened state, such as water absorption, density, and compressive strength. The results in the fresh state indicate that the compositions containing NaOH accelerate the setting process, but without impairing the workability of the mortar before the hardening process. The results of the fresh state of the compositions containing KOH indicate that the dissolution of this material is not as efficient in the cement medium in the first minutes after mixing the material. This impairs the workability of the mortar. In the hardened state, the density and water absorption results showed the occurrence of alkaline activation of silica fume. The results of compressive strength and diametral compressive strength were better for the compositions with NaOH and KOH, due to the occurrence of alkaline activation of silica fume which provided the formation of tobermorite and zeolites. Therefore, as an improvement this work concluded that the use of hydroxides together with the pozzolanic material silica fume is a more efficient way of replacing OPC than the isolated use of pozzolan, due to the occurrence of the alkaline activation process.

Oxidized Natural Biopolymer for Enhanced Surface, Physical and Mechanical Properties of Glass Ionomer Luting Cement.

This laboratory investigation aimed to synthesize and characterize micron-sized Gum Arabic (GA) powder and incorporate it in commercially available GIC luting formulation for enhanced physical and mechanical properties of GIC composite. Oxidation of GA was performed and GA-reinforced GIC in 0.5, 1.0, 2.0, 4.0 & 8.0 wt.% formulations were prepared in disc-shaped using two commercially available GIC luting materials (Medicem and Ketac Cem Radiopaque). While the control groups of both materials were prepared as such. The effect of reinforcement was evaluated in terms of nano hardness, elastic modulus, diametral tensile strength (DTS), compressive strength (CS), water solubility and sorption. Two-way ANOVA and post hoc tests were used to analyze data for statistical significance (p < 0.05). FTIR spectrum confirmed the formation of acid groups in the backbone of polysaccharide chain of GA while XRD peaks confirmed that crystallinity of oxidized GA. The experimental group with 0.5 wt.% GA in GIC enhanced the nano hardness while 0.5 wt.% and 1.0 wt.% GA in GIC increased the elastic modulus compared to the control. The CS of 0.5 wt.% GA in GIC and DTS of 0.5 wt.% and 1.0 wt.% GA in GIC demonstrated elevation. In contrast, the water solubility and sorption of all the experimental groups increased compared to the control groups. The incorporation of lower weight ratios of oxidized GA powder in GIC formulation helps in enhancing the mechanical properties with a slight increase in water solubility and sorption parameters. The addition of micron-sized oxidized GA in GIC formulation is promising and needs further research for improved performance of GIC luting composition.

Ceramic Thermal Insulator Based on Diatomite Obtained by Starch Consolidation Casting.

Researchers are continuously seeking to develop new materials to protect against inclement weather and thus optimize energy efficiency in housing. This research aimed to determine the influence of corn starch percentage on the physicomechanical and microstructural properties of a diatomite-based porous ceramic. The starch consolidation casting technique was applied to fabricate a diatomite-based thermal insulating ceramic with hierarchical porosity. Diatomite mixtures with 0%, 10%, 20%, 30%, and 40% starch were consolidated. The results show that starch content significantly influences apparent porosity, and this, in turn, influences several parameters, such as thermal conductivity, diametral compressive strength, microstructure, and water absorption of diatomite-based ceramics. The porous ceramic processed by the starch consolidation casting method corresponding to the mixture of diatomite with 30% starch obtained the best properties, with a thermal conductivity of 0.0984 W/m·K, an apparent porosity of 57.88%, a water absorption of 58.45%, and a diametral compressive strength of 35.18 kg/cm2 (3.45 MPa). Our results reveal that the diatomite-based ceramic thermal insulator obtained by starch consolidation is effective for use on roofs to improve thermal comfort in dwellings located in cold regions.

Pelletization Temperature and Pressure Effects on the Mechanical Properties of Khaya senegalensis Biomass Energy Pellets

Biomass pellets are one of the most crucial feedstocks for bioenergy production on a global scale due to their numerous advantages over raw biomass resources. Pellets provide improved energy density, bulk density, moisture content, and homogeneity thereby reducing storage, handling, and transportation costs. To produce high-quality solid fuel, it is necessary to comprehend the properties of wood fuel. This study explored the potential of Khaya senegalensis (khaya) as a dedicated energy crop (DEC) for the production of green energy. It thrives in less-than-ideal conditions and grows rapidly. The low durability of energy pellets raises the risk of dust and fire during handling and storage. In addition, the potential for fines and dust formation is strongly correlated with the mechanical strength of materials. Due to this necessity, the current study examines the effects of pelletization factors, including temperature and pressure, on pellet properties, particularly on its mechanical properties. The durability and compressive strength of pellets were determined using a sieve shaker and a universal testing machine, respectively. The highest mechanical durability was observed at 3 tons of pressure and 75 degrees Celsius, each with a value of 99.6%. The maximum axial compressive strength was measured at 57.53 MPa under 5 tons of pressure. When pelletized at 125 °C, the axial compressive strength increased by 13.8037% to 66.06 MPa compared to the strength obtained at 5 tons of pressure. Pelletizing Khaya feedstocks at 4 tons of pressure, on the other hand, produced a slightly lower diametral compressive strength of 7.08 MPa compared to 7.59 MPa at 125 °C. The experimental results revealed that the aforementioned factors significantly affect the mechanical properties of pellets. The elucidation of wood biomass, solid fuel qualities and pelletization parameters of this potential energy crop may facilitate the production of high-quality pellets from Khaya senegalensis wood to meet the increasing local and worldwide energy demands.

Reinforcing a metal-based composite with a percentage of MgO particale to improve some of its properties and its relationship to conventional heat treatment

This research involved the manufacture of three compounds using powdered metallurgy technology through the reinforcement of the AlNi with addition percentage (40%), (35%) and 30% (MgO) ceramic reinforce phase to compound of A , B and C respectively and thermally treated In the traditional way &#x0D; In order to study the effect of the MgO addition and heat treatment, the mechanical tests (Diametrical compressive strength and hardness) were conducted.&#x0D; In order to determine the possibility of using the models produced for the attenuation of β particles, The linear attenuation coefficient and half thickness were examined for all models, The mechanical properties and the linear attenuation coefficient of all compounds have been improved, It was observed that the effect of the chemical composition was greater on the properties under study. We obtained the value of the compressive compressive strength of C (29) MPa before the a heat treatment, while the same compound had the MPa ( 32) After the heat treatment, in case of change in the addition ratio, we obtained the highest values of the mechanical properties and the linear attenuation coefficient of C, (29) MPa, (39) and (19.6)cm-1 respectively., And the lowest value given to the thickness of half (0.035)cm compared with (0.078) given by the A compound with the lowest mechanical properties and the linear attenuation coefficient (26.5)Mpa, (34.5) and (8.8)cm-1respectively before thermal treatment.

Inducing hierarchical pores in nano-MOFs for efficient gas separation.

The synthesis of metal-organic frameworks (MOFs) and their processing into structures with tailored hierarchical porosity is essential for using MOFs in the adsorption-driven gas separation process. We report the synthesis of modified Cu-MOF nanocrystals for CO2 separation from CH4 and N2, prepared from DABCO (1,4-diazabicyclo[2.2.2] octane) and 9,10 anthracene dicarboxylic acid linkers with copper metal salt. The synthesis parameters were optimized to introduce mesoporosity in the microporous Cu-MOF crystals. The volumetric CO2 adsorption capacity of the new hierarchical Cu-MOF was 2.58 mmol g-1 at 293 K and 100 kPa with a low isosteric heat of adsorption of 28 kJ mol-1. The hierarchical Cu-MOF nanocrystals were structured into mechanically stable pellets with a diametral compression strength exceeding 1.2 MPa using polyvinyl alcohol (PVA) as a binder. The CO2 breakthrough curves were measured from a binary CO2-CH4 (45/55 vol%) gas mixture at 293 K and 400 kPa pressure on Cu-MOF pellets to demonstrate the role of hierarchical porosity in mass transfer kinetics during adsorption. The structured hierarchical Cu-MOF pellets showed stable cyclic CO2 adsorption capacity during 5 adsorption-desorption cycles with a CO2 uptake capacity of 3.1 mmol g-1 at 400 kPa and showed a high mass transfer coefficient of 1.8 m s-1 as compared to the benchmark zeolite NaX commercialized binderless granules, suggesting that the introduction of hierarchical porosity in Cu-MOF pellets can effectively reduce the time for CO2 separation cycles.

Evaluation of the Effect of the Addition of Hydroxyapatite on Selected Mechanical and Tribological Properties of a Flow-Type Composite.

(1) Background: The aim of the study was to determine the effect of modification with sintered hydroxyapatite (HAp) on selected mechanical and tribological properties of a flow-type composite. (2) Methods: Samples in the shapes of cuboidal beams (n = 120) and cylinders (n = 120) with the proper dimensions were prepared from a standard flow-type composite and others with the addition of 2% wt., 5% wt., and 8% wt. sintered hydroxyapatite. The bending strength, compression strength, diametral compression strength, impact resistance, hardness, and tribological properties were compared. (3) Results: In all cases, it was established that an increase in the amount of HAp caused a reduction in the bending, compression, and diametral compression strength. Increasing the amount of added HAp also reduced the impact strength, hardness, and wear resistance. However, the differences were statistically insignificant. (4) Conclusions: The addition of hydroxyapatite to a flow-type composite material worsened its mechanical and tribological properties; however, the obtained values were acceptable with 2% wt. and 5% wt. HAp.

Agro-industrial waste from corn straw fiber: Perspectives of application in mortars for coating and laying blocks based on Ordinary Portland cement and hydrated lime

The use of new natural fibers is considered a great advance in the science of cementitious materials to promote the use of natural resources in place of commonly used synthetic fibers. In this scenario, the objective of this research is to evaluate the incorporation of corn straw fiber in mixed cement and lime mortars for application in coating and laying blocks. Cylindrical specimens measuring 50x100 mm were made in the composition 1:1:6:1.55 (cement: lime: sand: water) using 0%, 2.5% and 5% of natural fibers and fibers treated with sodium hydroxide (soda) in relation to the mass of cement. The fibers were chemically, physically, mineralogically and morphologically characterized. The mixtures were evaluated for their consistency in the fresh state, in addition to properties in the hardened state, such as compressive strength, modulus of elasticity, diametral compressive strength, water absorption and density. In the fiber characterization results, it was observed that the soda treatment increased the fiber crystallinity from 46.7% in the natural fiber to 74.3% in the treated fibers. There was also an increase in the cellulose content, from 59.8% to 63.5%. These results are important because they indicate greater compatibility of the fibers with the cement matrix. Regarding the properties evaluated in the mortars, it was observed that the treatment with soda allowed the application of corn straw fibers, since the compositions with natural fibers showed a reduction in compressive strength, while the compositions with treated fibers showed equivalence statistic. The treatment also provided a reduction in the water absorption of the mortars, a positive factor due to the fiber hygroscopicity. In addition, there was a stiffness reduction in the cement matrix, identified by the modulus of elasticity that reduced from 133.30 MPa in the reference composition to 36.52 MPa in the composition with 5% soda treated fiber. Thus, it can be concluded that the corn straw fiber is viable for use in mortars for coating and laying blocks only after treatment with soda, which even improves problematic properties of cementitious materials, such as high stiffness.

Development of a ceramic membrane for emulsion water-diesel treatment

The purpose of this study was the development of a low-cost ceramic tubular membrane, using inexpensive materials, namely natural clay, and graphite as a porogenic agent. Such a low-cost membrane can be used as filters or porous supports for the preparation of multilayer ceramic membranes. Extrusion was used as a shape-forming method for this purpose. Graphite was selected as a porogenic additive. Raw materials were physicochemically and morphologically characterized. A comparative study of the influence of porogen content on membrane characteristics was carried out. Finally a graphite addition of 15 wt% and 850 °C as the sintering temperature were chosen. The obtained membrane had 41 vol% of porosity, diametral compression strength of 4 MPa, and relatively good corrosion resistance in basic and acid conditions. The performance of the membrane support was evaluated for diesel-in-water emulsion depuration as a function of pressure. Filtration test using 15% of porogen sample led to turbidity rejection factor of 95%. Therefore, it was considered that this membrane can be suitable for diesel/water emulsion treatment.

Evaluating the Mechanical Properties of Restorative Glass Ionomers Cements

The aim of this research was to assess the efficiency of 4 restorative glass ionomer cements (GICs): Fuji IX (GC), ChemFil Rock (DENSPLY), Riva Self-Cure (SDI), and Ketac Nano (3M ESPE). The 4 restorative glass ionomers' diametral tensile and compressive strengths were evaluated at room temperature for 24 hours and then stored in distilled water. The universal testing machine (INSTRON 5566A) was used to record the maximum load necessary to fracture specimens. Surface wear, diametral tensile strength, and compressive strength against dental ceramic were compared using analysis of variance followed by the Bonferroni method at a significance level of 0.05. Ketac Nano and ChemFil Rock were found to have better diametral tensile strength than Riva Self-Cure and Fuji IX. The significant difference between ChemFil Rock and Fuji IX (P ≤ .005) and ChemFil Rock with Riva Self-Cure (P ≤ .005) was shown by post hoc analysis. Ketac Nano had better tensile strength than Riva Self-Cure and Fuji IX. Fuji IX showed the lowest material loss of the GICs as revealed by wear against VITABLOCS Mark II (VITA Zahnfabrik). This study indicated a significant difference in the compressive strengths of ChemFil Rock and Riva Self-Cure. ChemFil Rock had the highest tensile strength. The diameter tensile strength of all 4 materials was statistically insignificant. Finally, Fuji IX had the least amount of material loss. ChemFil Rock was proven to be more effective than Fuji IX.

Comparison of Mechanical Properties of a Self-Adhesive Composite Cement and a Heated Composite Material

(1) Background: Due to the limitations of composite cements, the authors carried out tests to compare such materials with preheated composite materials because the latter may be an alternative to cements in the adhesive cementation procedure. (2) Methods: The materials used in the adhesive cementation procedure, i.e., Enamel Plus Hri (Micerium, Avegno, Italy), a heated composite material, and RelyX U200 Automix (3M, Maplewood, MN, USA), a dual composite cement, were tested for microhardness, compressive strength, flexural strength, diametral compressive strength, and elastic modulus. Composite material was heated to the temperature of 50 degrees Celsius before polymerisation. (3) Results: Higher values of microhardness (by 67.36%), compressive strength (by 41.84%), elastic modulus (by 17.75%), flexural strength (by 36.03%), and diametral compressive strength (by 45.52%) were obtained using the Enamel Plus Hri composite material compared to the RelyX U200 self-adhesive cement. The survey results revealed statistically significant differences. (4) Conclusions: Due to its better mechanical properties, the heated composite material (Enamel Plus Hri) is a beneficial alternative to composite cements in the indirect restoration placement procedure. As the strength parameters of the heated composite material increase, a higher resistance to the compressive and bending forces present in the oral cavity, and hence a greater durability of the created prosthetic reconstructions can be expected.

Assembly of Ultralong Hydroxyapatite Nanowires into Enamel-like Materials

To develop dental restorative materials with enamel-like structures, ultralong hydroxyapatite (HA) nanowires were synthesized by a hydrothermal method, followed by functionalization with 3-methacryloxypropyltrimethoxysilane (KH-570). The mixture of HA nanowires, KH-570, and light initiator was stirred and centrifuged. The precipitate was vacuum filtered to remove excessive KH-570 and then pressured under cold isostatic pressing (10 MPa × 24 h). Finally, the block was polymerized by lighting. Scanning electron microscopy and transmission electron microscopy showed that HA nanowires with aspect ratios >1,000 were assembled into enamel rod–like microstructures and evenly dispersed in the polymerized KH-570 silane matrix to form enamel-like structures. Thermogravimetric analysis demonstrated that the content of HA nanowires reached 72 wt% in the composite. The enamel-like composite showed a similar hardness, frictional property, and acid-etching property to those of enamel and a comparable or even better diametral tensile strength and compressive strength than some commercial composite resins in mechanical tests in vitro. In addition, the enamel-like composite had good cytocompatibility. Such enamel-like composites may have the potential to be used in biomimetic tooth restorations in the future.

Freeze-gelcasting of aqueous alumina powder suspension using natural rubber latex

A new and non-toxic aqueous alumina gelcasting system using natural rubber (NR) latex as a gel former has been studied. A gel of reasonable strength is achieved by freezing concentrated alumina-NR latex co-dispersions in a mould followed by mould removal and aging in acetone. Gelation is achieved by coagulation of latex particles due to the breakdown of the protein layer on their surface during ice crystal growth. The minimum concentration of rubber required to percolate and form a soft and stable gel is 8 wt % of alumina. Aging of the frozen body in acetone for solvent exchange results in strengthening of the alumina-rubber gel network by further coagulation leading to reasonably high strength (∼60 kPa). The frozen body passes through a semi-fluid state during aging in acetone which enables the gel to reorganize and fill the space created by melting of ice crystals and thereby preventing the occurrence of pores in the green ceramics. The exchange of water in the gelled body with acetone enables easy and faster gel drying at room temperature. The diametrical compressive strength of the green body increases from 0.35 to 2.14 MPa during annealing at 200 °C due to the cross-linking of rubber. The cross-linked rubber in the green body undergoes near-steady state burnout without creating any crack. Debinding followed by sintering of the gelcast bodies at 1550 °C produce ceramics of ∼96% density. The sintered ceramics show a dense microstructure with an average grain size of 1.3 μm. The gelcasting using the NR latex is capable of producing complex near-net-shapes.

The densification and diametral compression strength of Hydroxyapatite-Zirconia bioceramics: Experimental and modelling studies

In the present work, hydroxyapatite (HAP) and zirconia (ZrO2) powders have been used to elaborate HAP-ZrO2 composite for biomedical applications. X-ray diffraction (XRD), and scanning electron microscopy (SEM)), were used to characterize the as-obtained samples. The aim of this study was to evaluate the morphology, densification and mechanical strength of the produced ceramics sintered at 1200 °C and 1250 °C. The relative density and mechanical strength of the HAP-ZrO2 ceramics reached their height values at 1250 °C. Experimental results were modeled by the finite element method to determine the stress distribution in the compacted samples. In addition, the stress intensity factors in produced ceramics for different geometrical dimensions of the notch was evaluated numerically.

Mechanical, physical and durability properties of activated alkali cement based on blast furnace slag as a function of %Na2O

The use of activated alkali cements (AAC) as a replacement for Ordinary Portland cement (OPC) has become a viable alternative. This is due to the advantages of these materials, such as the possibility of using wastes or industrial by-products in their composition, contributing to environmental sustainability, in addition to the mechanical properties’ superior to OPC. The objective of this work was to evaluate the mechanical, physical and durability properties of an AAC based on blast furnace slag. The production of specimens was carried out in the proportion 1:2:0.45 (binder: aggregate: water), varying the sodium content in the alkaline solution between 2.5% and 15% and varying the age of thermal cure at 65ºC in 7 and 28 days. Compressive strength tests, calorimetry, diametrical compressive strength, density, electrical resistivity, capillary water absorption, water absorption and determination of porosity were carried out. It was observed that the compressive strength values for the 10% sodium composition were 22.12 MPa at 7 days and 41.07 MPa at 28 days. OPC, on the other hand, showed strength of 7.85 and 16.25 MPa, at 7 and 28 days in thermal cure at 65ºC, respectively. In addition, the performance of activated alkali cement-based mortar was superior to cement-based mortar in the other parameters evaluated. Thus, it is concluded that the use of blast furnace slag is a viable alternative for the production of AAC, a potential substitute for OPC, a material whose production is extremely polluting.

Mechanical and Physical Properties of Khaya senegalensis Solid Fuel Pellet with Different Binder Percentages

The characteristics of the solid fuel pellets, such as its strength, durability and density can be used to assess its quality. During the transport and storage, pellets with low strength and durability produces dusts and ultimately resulting in equipment blockage, high pollution emissions, and an increased risk of fire and explosion. Therefore, pellet manufacturing process should be given priority to improve pellet quality. The use of binder in the production of pellets will aid in improving pellet quality. Therefore, this study investigates the influence of different binder percentages on the mechanical properties of K. senegelensis fuel pellets. Durability, unit density, bulk density and diametral compressive strength testing were carried out in compliance with international standards. It was discovered that pellets containing 4% cassava starch binder produces better results, particularly in terms of durability and compressive ldiametral strength.

Evaluation of diametral tensile and compressive strengths of different types of nanocomposites for dental applications

This study aims to evaluate the diametral tensile strength (DTS) and compressive strength (CS) of restorative composite resins that applied as restorative materials in the field of dentistry. The composites were prepared from different sets of monomers which divided into six groups (A, B, C, D, E, and F) according to the type and ratios of monomers used in preparing the matrix materials, excepted the basic monomer (2, 2 propyl bisphenol glycidyl dimethacrylate (Bis-GMA)) that added at constant ratio (40 wt%), in addition tothe nano-inorganic fillers [SiO2, ZrO2, HA, and Al2O3] which adding individually. Ninety specimens were prepared for diametral tensile strength test, which divided into six groups according to the prepared resin matrix and five sub-divided groups according to types of fillers of prepared composites, and for compressive strength test, the same numbers of specimens were prepared. In the beginning, the diametral tensile strength (DTS) and compressive strength of the prepared matrices were determined and then study the effect of adding the nano-inorganic fillers on the results of these properties for the prepared dental restorations nanocomposites materials. The results show that the composites based on resin matrix of group (D) having the selected monomers (BIS-GMA, meth acrylamide, methacrylic acid, and 1–6 hexanediol methacrylate) that reinforced with silica nanoparticle have higher properties as compared with other types of the prepared nanocomposite, where these values reached to (54 MPa and 174 MPa) for diametral tensile strength and compressive strength, respectively.

Porosity control in silicon nitride‐based support materials toward enhanced gas permeability

AbstractPorous Si3N4 materials in tubular geometry are prepared by slip casting before partial sintering. A variety of material‐ and process‐specific variables and their respective effects on densification and resulting pore morphology are systematically evaluated, focusing on starting powder type, amount of sintering additives, and sintering parameters including temperature and time. An increased β‐Si3N4 content in the starting powder was found to promote the formation of a network of elongated grains exhibiting increased pore diameters, as opposed to a more finely featured pore network obtained from starting materials consisting of α‐Si3N4. Following an iterative evaluation of processing variables, materials exhibiting a characteristic diametral compression strength (C‐ring test) of 163 MPa and a Darcian permeability of 4.7 ⋅ 10−15 m2 at a total porosity of 41% were obtained, corresponding to an increase of over 40% in strength and of over 600% in permeability in comparison to materials obtained by α‐Si3N4 powders at comparable porosities. These results demonstrate that the composition of Si3N4 powders significantly affects the resulting pore structure, and by combining the respective selection of starting materials with finely tuned sintering parameters, materials with superior performance in terms of mechanical properties as well as permeability characteristics are accessible.

Machinable green bodies by dry pressing of alumina powder using natural rubber latex as a cross-linkable binder

We report the use of natural rubber as a binder for powder pressing for the first time. The feedstock for powder pressing is obtained by the co-coagulation of alumina powder-natural rubber latex co-dispersions in 10 mM formic acid solution. The pressing pressure and binder concentration are optimized by measuring the green density and diametrical compressive strength. The remarkable increase in diametrical compressive strength observed on heating the pressed bodies at 220 °C is due to the cross-linking of natural rubber. A maximum diametrical compressive strength of 9.4 MPa observed at 8 wt% natural rubber concentration is one of the highest values reported in the literature. The pressed compacts after cross-linking heat-treatment are amenable to milling, drilling and lathing using conventional machines and tools. The pressed bodies on binder removal and sintering at 1550 °C produce alumina ceramics of ~97% of theoretical density with an average grain size of 1.8 μm.