Point Bending Strength Research Articles

Strengthening of borosilicate glass by controlled crystallisation for lightweight bulletproof materials

For development of lightweight bulletproof glass window, TiO2 added as a nucleating agent to borosilicate glass was crystallised by 2-step heat-treatment. The glass transition temperature (Tg) and crystallisation temperature (Tc) were 595°C, 810°C, respectively. The maximum nucleation rate was 7.3 × 10 10 mm -3 hr -1 at 600°C and the maximum crystal growth speed was 1.73 nm/min at 810°C. The maximum 3-point bending strength was 563 MPa when the crystal volume fraction and crystal size were 36.1%, 53.4 nm with number of crystals per unit volume of 4.525 × 10 10 mm -3 at 600°C for 1 hr, 810°C for 30 min. The Vickers' hardness and fracture toughness of same crystal volume fraction were 736 kg/mm 2 and 1.0779 MPa m 1/2 which were about 220%, 17%, 44% higher than borosilicate glass. Thus, the bulletproof materials were replaced by crystallised borosilicate

반응소결 탄화규소의 다양한 α-SiC 조성에 따른 기계적 특성과 전기저항 특성에 관한 연구

저저항 Si-SiC 소결체 제조를 위해 <TEX>${\alpha}$</TEX>-SiC에서 조성과 C의 양을 변화시키면서 반응소결 특성을 고찰하였다. 시료준비는 정수압으로 성형체를 제조하였고, 용융Si 반응소결을 통해 시험편을 준비하였다. 반응소결체의 미세구조, 기계적 특성 및 전기저항 분석 결과 용융Si과 반응 후 미립의 <TEX>${\beta}$</TEX>-SiC가 생성되었고, 치밀한 소결체를 형성하였다. 미립 <TEX>${\beta}$</TEX>-SiC 생성량은 카본 양 에 따라 증가하였다. 그리고 C함량 10wt%이내에서 기계 R전기저항특성은 입도조성 영향이 크고 카본 함량 10wt%이상에서는 상전이 반응의 영향이 큼을 알 수 있었다. For the manufacture of low resistance Si-SiC composite, the properties of reaction sintering in the green body of various mixed <TEX>${\alpha}$</TEX>-SiC powder size with the various carbon contents from 0wt% to 20wt% were investigated. The samples preparation was green body by CIP method under this condition, molten silicon infiltration process was conducted to reaction bonded silicon carbide. the results of sintered density, 3-point bending strength and resistance of analysis showed that varied carbon and silicon melt reacted to convert to fine <TEX>${\beta}$</TEX>-SiC particle and the structure was changed to dense material. The amount of fine <TEX>${\beta}$</TEX>-SiC particle was gradually increased as carbon content increase. According to mixed composite, it's mechanical and specific resistivity properties was strongly influenced by carbon content within 10wt% more then carbon content 10wt% was strongly influenced by phase transition.

Dual setting α-tricalcium phosphate cements

An extension of the application of calcium phosphate cements (CPC) to load-bearing defects, e.g. in vertebroplasty, would require less brittle cements with an increased fracture toughness. Here we report the modification of CPC made of alpha-tricalcium phosphate (α-TCP) with 2-hydroxyethylmethacrylate (HEMA), which is polymerised during setting to obtain a mechanically stable polymer-ceramic composite with interpenetrating organic and inorganic networks. The cement liquid was modified by the addition of 30-70 % HEMA and ammoniumpersulfate/tetramethylethylendiamine as initiator. Modification of α-TCP cement paste with HEMA decreased the setting time from 14 min to 3-8 min depending on the initiator concentration. The 4-point bending strength was increased from 9 MPa to more than 14 MPa when using 50 % HEMA, while the bending modulus decreased from 18 GPa to approx. 4 GPa. The addition of ≥50 % HEMA reduced the brittle fracture behaviour of the cements and resulted in an increase of the work of fracture by more than an order of magnitude. X-ray diffraction analyses revealed that the degree of transformation of α-TCP to calcium deficient hydroxyapatite was lower for polymer modified cements (82 % for polymer free cement and 55 % for 70 % HEMA) after 24 h setting, while the polymerisation of HEMA in the cement liquid was quantitative according to FT-IR spectroscopy. This work demonstrated the feasibility of producing fracture resistant dual-setting calcium phosphate cements by adding water soluble polymerisable monomers to the liquid cement phase, which may be suitable for an application in load-bearing bone defects.

High-Temperature Brazing Molybdenum

High-temperature brazing molybdenum using palladium and titanium foils have been investigated in the experiment. Successful brazed joints are achieved from using the palladium filler foil. Brazed joints are fully dense and free of any intermetallic phase. Three point bending strengths of 246 and 233 MPa are obtained from joints using 100 m thick palladium filler foil brazed at 1580 and 1610 oC for 600 s, respectively. The application of palladium filler foil shows potential in brazing molybdenum for high-temperature application.

주입성형한 지르코니아 소결체의 기계적 성질에 미치는 알루미나 첨가의 영향

Purpose: Zirconia blocks for all ceramic dentures are divided into two groups. One is pre-heated block and the other is binder added block. In this study, the possibility of recycling the remained parts of binder added block after CAD/CAM machining with slip casting process was investigated. Methods: Owing to the binder added block contain large amount of organic matter, Binder burn-out was must be carried out before ball milling for preparing the casting slip. Binder burn-out was accomplished at <TEX>$600^{\circ}C$</TEX> for 10 hours. Ball milling was performed with 5mm zirconia ball and 60mm polyethylene bottle. From 0% to 5% at 1% intervals of alumina was added to zirconia powder for preparing slip. Solid casting was achieved with plaster mold. Cast bodies were dried and sintered at <TEX>$1,500^{\circ}C$</TEX> for 1 hour. Linear shrinkage, apparent porosity, water absorption, bulk density, and flexural strength were tested. Microstructures were observed by SEM, EDS and XRD analysis were executed. Results: Optimum slips for casting was prepared with 300g ball, 100g powder, and 180g distilled water. Cast body without alumina showed 26% of linear shrinkage, 6.07 of apparent density, and 470MPa of three point bend strength. On the other hand, as received zirconia block, which was sintered at the same conditions, showed 23% of linear shrinkage, 6.10 of apparent density, and 680MPa of three point bend strength. When 3% of alumina was added to zirconia, sintered body showed 23% of linear shrinkage, 6.10 of apparent density, and 780MPa of three point bend strength. SEM photomicrographs and EDS analysis showed alumina particles uniformly dispersed in zirconia matrix, and XRD analysis showed no phase transformation of tetragonal zirconia particles was occurred when alumina was added. Conclusion: According to the all of this experimental results, 3% of alumina added cast zirconia body showed excellent mechanical properties more than as received binder containing zirconia block.

Preparation of Pigmented Glass for Infiltration and Investigation of its Physical and Mechanical Properties

Aim To explore pigmented glass for infiltration and investigate its physical and mechanical properties. Methods The pigmented glass was prepared by melting glass components in an alumina crucible at 1400°C for 2h. The thermal properties were tested using a Setaram-TGDTA 92 analyzer; three point bending strength and fracture toughness were also tested; the microstructure of the glass was studied using a scanning electron microscope. Results The thermal expansion coefficient over the range 20–600 °C was 6.2 × 10-6 °C -1, Tg was about 690 °C, the density, bending strength, fracture toughness and Vickers hardness were 2.23 g/cm3, 118 MPa, 1.22 MPam1/2, and 7.4 GPa respectively. Conclusion The pigments have no detrimental effects on the physical and mechanical properties; thus the pigmented glass for infiltration has favorable physical and mechanical properties and also good compatibility with presintered porous alumina.

Improved Oxidation Resistance of SiС-Based Ceramic Matrix Composites by In Situ Reaction with Si3N4 Filler

SiC-Si3N4 powders and modified SiC-based ceramic matrix composites (CMCs) were fabricated using polycarbosilane (PCS), divinylbenzene (DVB) and Si3N4 filler. Si3N4 was introduced into CMCs fabricated through polymer infiltration and pyrolysis (PIP) to lower down the carbon content by in-situ carbothermal reaction, which derived from pyrolyzed PCS-DVB. The oxidation resistance and three point bending strength of modified C/SiC composites were effectively enhanced. The phase composition, microstructure of SiC-Si3N4 powders and modified C/SiC composites were investigated by XRD, SEM and TEM.

Mechanical properties of zirconia toughened alumina with 10–24 vol.% 1Y-TZP reinforcement

Abstract Zirconia toughened alumina ceramics have found broad applications in industrial scale as they can provide high strength, toughness and wear resistance. Processing and compositional parameters have to be properly adjusted to achieve optimum mechanical properties. ZTA ceramics with an yttria content of 1 mol% and zirconia contents ranging from 10 to 24 vol.% were hot-pressed at 1475 °C at 50 MPa axial pressure and different dwell of 1–3 h. Stabilization of the reinforcement phase in ZTA with yttria was performed by a nitrate coating process of monoclinic zirconia nanopowders and subsequent blending with sub-micron size alumina. Microstructure and mechanical properties were investigated. A high ISB toughness of 8.5 MPa √m in combination with a 3-point bending strength of 1198 MPa was determined for the 1 mol% yttria 17 vol.% ZTA overmatching previous studies of coated ZTA ceramics. The interaction between stabilizer and reinforcement phase has a strong influence on the mechanical properties.

Crystalline phases and physical properties of modified stoneware body with glaze sludge

Ceramic stoneware body has been modified with ceramic and glass industrial wastes by replacing 25–100% as flux in the formula. The effects of solid wastes added to the bodies were studied after firing in the temperature range 950–1280°C. The physical properties of linear shrinkage, bulk density, apparent porosity, water absorption and 3-point bending strength were determined. A composition which related to the general stoneware properties was found when using soda-lime cullet and glaze sludge. It had a firing range lowered to 1050–1100°C. SEM results demonstrated the sintered microstructure increased in density with increase in solid waste in the modified body. XRD results after firing showed the crystalline phases comprised of mullite, albite calcian and quartz. Thermal expansion was measured in the range 6.53–6.67×10−6K−1 at 30–500°C. The modified bodies were capable of forming prototype products by slip casting and jiggering.

Evaluation of copper ion of antibacterial effect on Pseudomonas aeruginosa, Salmonella typhimurium and Helicobacter pylori and optical, mechanical properties

Antibacterial effect on Pseudomonas aeruginosa, Salmonella typhimurium and Helicobacter pylori of copper ion was researched. Also, additional effects of copper ion coating on optical and mechanical properties were researched as well. Copper ion was coated on glass substrate as a thin film to prevent bacteria from growing. Cupric nitrate was used as precursors for copper ion. The copper ion contained sol was deposited by spin coating process on glass substrate. Then, the deposited substrates were heat treated at the temperature range between 200°C and 250°C. The thickness of deposited copper layer on the surface was 63nm. The antibacterial effect of copper ion coated glass on P. aeruginosa, S. typhimurium and H. pylori demonstrated excellent effect compared with parent glass. Copper ion contained layer on glass showed a similar value of transmittance compared with value of parent glass. The 3-point bending strength and Vickers hardness were 209.2MPa, 540.9kg/mm2 which were about 1.5% and 1.3% higher than the value of parent glass. From these findings, it is clear that copper ion coating on glass substrate showed outstanding effect not only in antibacterial activity but also in optical and mechanical properties as well.

Effect of atorvastatin on the cortical bones of corticosteroid treated rabbits

Osteoporosis ("secondary" osteoporosis) and avascular necrosis (AVN) of the femoral head are well-known adverse effects of corticosteroid therapy. Statins have been reputed to increase bone strength and bone density. In this study, we evaluated the effect of atorvastatin calcium on the flexural properties (3-point bending strength and modulus) of corticosteroid (methylprednisolone acetate) treated rabbit femurs and tibias. Our study hypothesis was that the use of statins would counteract the loss of bone strength caused by corticosteroid treatment. The 40 rabbits were divided into 5 groups: control, corticosteroid alone and corticosteroid combined with oral doses of atorvastatin calcium (2, 10, or 20 mg/day). A daily oral dose of atorvastatin calcium treatment for 70 days weakened the long bones of methylprednisolone acetate treated rabbits irrespective of the dosage (2, 10, or 20 mg). Cortical bone strength was assessed using the 3-point bending test at the end of the study period. A daily oral dose of atorvastatin calcium did not attenuate the loss of cortical bone strength caused by corticosteroid treatment in rabbits. It appeared to decrease that bone strength. If these results hold true in humans, they would have wide applicability given the frequent combined use of corticosteroids and statins in many patients.

Carbon Aerogel Composites Prepared by Ambient Drying and Using Oxidized Polyacrylonitrile Fibers as Reinforcements

Carbon fiber-reinforced carbon aerogel composites (C/CAs) for thermal insulators were prepared by copyrolysis of resorcinol-formaldehyde (RF) aerogels reinforced by oxidized polyacrylonitrile (PAN) fiber felts. The RF aerogel composites were obtained by impregnating PAN fiber felts with RF sols, then aging, ethanol exchanging, and drying at ambient pressure. Upon carbonization, the PAN fibers shrink with the RF aerogels, thus reducing the difference of shrinkage rates between the fiber reinforcements and the aerogel matrices, and resulting in C/CAs without any obvious cracks. The three point bend strength of the C/CAs is 7.1 ± 1.7 MPa, and the thermal conductivity is 0.328 W m(-1) K(-1) at 300 °C in air. These composites can be used as high-temperature thermal insulators (in inert atmospheres or vacuum) or supports for phase change materials in thermal protection system.

Lu2O3-SiO2계 소결조제를 포함하는 Silicon Nitride의 소결 특성 및 기계적 거동

Gas pressure sintering (GPS) of reaction bonded silicon nitride (RBSN) was performed using Lu 2 O 3 -SiO 2 additive and the properties were compared with those of specimens prepared using high purity Si 3 N 4 powder. The relative density of RBSN and compacted Si 3 N 4 powder were 68.9 and 47.1%, and total linear shrinkage after sintering at 1900℃ were 14.8 and 42.9%, respectively. High nitrogen partial pressure (5MPa) was required during sintering at 1900℃ in order to prevent the decomposition of the nitride and to promote the formation of SiC. The relative density and 4-point bending strength of RBSN and Si3N4 powder compact were 97.7%, 954MPa and 98.2%, 792MPa, respectively, after sintering at 1900℃. The sintered RBSN also showed high fracture toughness of 9.2MPam 1/2 .

Self-healing Behavior of 2D-C/[SiC-(B-C)] Composite in Aero-engine Combustion Chamber

采用以B-C陶瓷为基体自愈合改性组元的2D-C/[SiC-(B-C)]以及经过硅硼玻璃改性的2D-C/[SiC-(B-C)]制备浮壁瓦片, 分别在1000、1200、1350℃下对其进行发动机燃烧室环境考核. 对考核后的浮壁瓦片进行取样, 并在室温下进行拉伸强度以及三点弯曲强度测试. 结果发现: 经过环境考核试样的力学性能都有不同程度的提高, 拉伸强度和三点弯曲强度随着考核温度的升高而提高, 其中三点弯曲强度的升高速率更快. 通过SEM观察, B-C自愈合组元氧化生成的玻璃相以及改性硅硼玻璃相在考核过程中有效地封填了试样的孔隙和裂纹. 最后通过力学性能测试结合SEM观察, 初步分析了两种复合材料在航空发动机燃烧室中的愈合机制.

Treatment of Scumming Effects of Pottery Clay by Sodium Carbonate Addition

Earthenware pottery products made by using red plastic clay in Ratchaburi province of Thailand and fired at 850-1000 °C, always shows some blemishes, caused by scumming on the surface. This scumming contains calcium sulfate, contaminated in the raw clay as gypsum form. The addition of barium carbonate is a suggested solution to prevent this white stain. However, it is difficult for barium carbonate to spread throughout the clay so that it takes a long time to complete the reaction. This research aims to find the solution by using sodium carbonate as an alternative chemical. Sodium carbonate was mixed in the clay at 1wt% dissolved in distilled water controlled the moisture at 22 % by wet weight. The mixture was kneaded and aged for 24 h, then formed, dried and fired at 850-950 °C. The types and quantities of ion in mixed clay and deposited on the surface product were determined after drying. It was found that the white stain areas were diminished, as same as the result from the addition of barium carbonate. Moreover, the sample after firing at 950 °C had lower water absorption as 12.22 %, higher three point bending strength as 32.53 MPa when compared to the addition of barium carbonate, which had higher water absorption as 15.58 % and lower three point bending strength as 25.25 MPa.

다양한 산화물들이 리튬규산염 유리의 결정화에 미치는 영향

Glass-ceramics based on lithium disilicate(Li₂Si₂O?) are prepared by heat-treatment of glasses in a system of SiO₂-Li₂O-K₂O-Al₂O₃ with different compositions. The crystallization heat-treatment was conducted at the temperature range of 700~900℃ and samples were analyzed by XRD and SEM. Mechanical properties were determined by a Vicker’s hardness and 4 point bending strength. When SiO₂/Li₂O ratio increased, cristobalite and tridymite crystals showed more predominate than lithium disilicate crystals. Increase in Al₂O₃ contents in the glass suppressed crystallzation of lithium disilicate crystals. Increase in ZnO, B₂O₃ contents in the glass decreased crystallization temperature of lithium disilicate crystals, and increased mechanical properties because of the reduction of the lithium disilicate crystal size.

Processing and properties of alumina–carbon nano fibre ceramic composites using standard ceramic technology

Multi-wall carbon nano fibres (MWCNFs) offer an alternative to multi-wall carbon nanotubes (MWCNTs) as conductive reinforcing phases in ceramic composites. The main differences being their lower cost and larger dimensions. Alumina (Al 2O 3) composite materials with up to 12.5 vol.% content of carbon nano fibres (CNFs) have been produced using standard ceramic processing technology and additives. A detailed description of the milling and dispersion procedure, which produces a homogenous dispersion of the CNFs in the Al 2O 3 microstructure is presented. Dense hot pressed ceramic–CNF composites produced thereof have been characterized for electrical and thermal conductivity, three point bending strength and microstructure. The composites show that a critical flaw size is introduced with the CNFs and the decrease in strength does not vary with increasing CNF content. The composites show a near linear increase in electrical conductivity as a function of CNF content. A slight decrease in the thermal conductivity with increasing CNF content was also observed.

Electrical discharge machining of B 4C–TiB 2 composites

The interrelationships between the microstructure and electrical discharge machining (EDM) behaviour of B 4C–TiB 2 composites with respectively 30, 40 and 60 vol.% TiB 2 are investigated. Special attention was given to the influence of the grain size on the EDM behaviour by producing composites with an ultrafine TiB 2 phase using in situ synthesis during PECS. The experimental work revealed that 40 vol.% of TiB 2 results in an optimal material removal rate while the surface roughness for rough cut EDM decreases with increasing TiB 2 content. The finer microstructure of the ultrafine composite shows higher MRR's and lower R a values than the commercial powder based composites. The major material removal mechanism for the PECS based composites was melting. The 3 point bending strength of all composites after grinding, EDM rough cut and EDM finish cut was not statistically different and about 800 MPa. The EDM recast layer was analysed by X-ray photoelectron spectroscopy.

Development, performance and stability of sulfur-free, macrovoid-free BSCF capillaries for high temperature oxygen separation from air

Capture and storage of CO 2 (CCS) from fossil-fuel power plants is vital in order to counteract a pending anthropogenic global warming. High temperature oxygen transport perovskite membranes can fulfill an important role in the separation of oxygen from air needed in the oxy-fuel technologies for CCS. In this study we present the development, performance and stability of gastight, macrovoid-free and sulfur-free Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3 − δ (BSCF) mixed conductor capillary membranes prepared by phase-inversion spinning and sintering. A sulfur-free phase-inversion polymer was chosen in order to obtain a phase-pure BSCF crystal phase. Special attention was given to the polymer solution and ceramic spinning suspension in order to avoid macrovoids and achieve gastight membranes. The sulfur-free BSCF capillaries showed an average 4-point bending strength of 64 ± 8 MPa and a maximum oxygen flux of ∼5.3 Nml/(cm 2 min) at 950 °C for an argon sweep flow rate of 125 Nml/min. The comparison of the performance of sulfur-free and sulfur-containing BSCF capillaries with similar dimensions revealed a profound impact of the sulfur contamination on both the oxygen flux and the activation energy of the overall oxygen transport mechanism. Both long-term oxygen permeation at different temperatures and post-operation analysis of a sulfur-free BSCF capillary were performed and discussed.

Influence of chemical composition on sintering ability of ZTA ceramics consolidated from freeze dried granules

Dense zirconia-toughened alumina (ZTA) ceramic composites with ZrO2=0, 5, 10, 15, 20, 30, 60 and 100wt.% have been prepared by sintering green compacts obtained by dry powder pressing of freeze dried granules consisting of α-alumina and a yttria partially stabilized zirconia (YPSZ) at various temperatures ranging from 1450 to 1650°C for 1–2h. The characteristics of sintered products were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), Archimedes principle, Vickers indentation method and by 3-point bend test. Characterization results revealed that adding YPSZ increased the 3-point bend (flexural) strength, fracture toughness and homogeneity of the microstructure, but slightly decreased the hardness and the sintering ability of alumina. A 20wt.% YPSZ was sufficient to increase the fracture toughness and flexural strength of specimens sintered for 2h at 1600°C from 2.5 to 4.6MPam1/2 and 150 to 400MPa, respectively. The XRD results revealed that there is no solid-solution formation between zirconia and alumina constituents of ZTA ceramic composites upon sintering.