Al2O3/ZrO2层状复合陶瓷的结构设计与性能

以ZrO2为基本组成相的层状材料,采用干法的成型工艺,通过对表面层不同组分Al2O3 ZrO2和表面厚度和系统研究和设计,提出设计三层结构复合陶瓷层裂参数λ,当λ小于1．5时,表面层不会出现层裂,整体材料性能较好,研究表明,表面残余压应力的存在,使得三层结构复合陶瓷较单层结构陶瓷表面出更高的强度,硬度,断裂韧性和其他性质,45％Al2O3/ZrO2/45%Al2O3层状复合陶瓷的弯曲强度达682MPa,断裂韧性达16.2Pa.m^1/2;而单层ZrO2陶瓷的弯曲强度和断裂韧性分别仅为450MPa和8.8MPa.m^1/2.     

Al_2O_3/ZrO_2层状复合陶瓷的结构设计与性能

以ZrO2 为基本组成相的层状材料 ,采用干法成型工艺 ,通过对表面层不同组分Al2 O3+ZrO2 和表面厚度的系统研究和设计 ,提出设计三层结构复合陶瓷层裂参数λ ,当λ小于 1.5时 ,表面层不会出现层裂 ,整体材料性能较好 .研究表明 ,表面残余压应力的存在 ,使得三层结构复合陶瓷较单层结构陶瓷表现出更高的强度、硬度、断裂韧性和其他性质 .45 %Al2 O3/ZrO2 / 45 %Al2 O3层状复合陶瓷的弯曲强度达 682MPa,断裂韧性达 16.2MPa·m1 /2 ;而单层ZrO2 陶瓷的弯曲强度和断裂韧性分别仅为 45 0MPa和 8.8MPa·m1     

碱金属氧化物引入量对MgO-Al2O3-SiO2微晶玻璃结构及其化学增强效果的影响

采用K2 O、Li2 O取代玻璃中的Na2 O,通过"熔融-整体析晶"法制备了MgO-Al2 O3-SiO2系统微晶玻璃,并于450℃的KNO3熔盐中强化6 h.运用DSC、XRD、表面应力测试仪、显微硬度仪等测试方法和仪器,研究碱金属氧化物引入量对微晶玻璃微观结构和离子交换工艺的影响.研究结果表明:750℃晶化处理之后,含4wt％K2 O的微晶玻璃样品与不含K2 O样品相比,离子交换后表面应力深度由19.78μm提高至42.21μm,但表面应力却由786.34 MPa降低至580.57 MPa,玻璃硬度由762.10 Hv降至694.12 Hv;含有1wt％K2 O及1wt％Li2 O的微晶玻璃样品,离子交换后应力深度为19.56μm,应力大小为779.71 MPa,与不含K2 O样品相近,但硬度较低,为745.80 Hv.     

熔盐添加剂对玻璃离子交换和增强的影响

在工业纯KNO3中分别添加KOH,K3PO4,K2CO3,K2SiO3与Al2O3的混合物,研究了熔盐添加剂对浮法玻璃离子交换和增强的影响.用电子探针测试了玻璃表而的K+浓度;测定了样品的表面应力、弯曲强度和显微硬度.结果表明:上述添加剂町以增加离了交换层深度,缩短离子交换时间,明显提高玻璃的力学性能,其增强效果与分析纯KNO3的增强效果相当,甚至比后者好:在交换温度为450℃下,玻璃交换层厚度大于29μm,玻璃的力学性能为:表面应力>480MPa,弯曲强度>400MPa.显微硬度为6.49GPa.     

MgO-MnO2-TiO2-SiO2烧结助剂中SiO2的量对低温烧结氧化铝陶瓷材料性能的影响

本文采用MgO-MnO2-TiO2-SiO2复相添加剂作为氧化铝陶瓷的烧结助剂,采用注浆成型工艺,研究了改变添加剂SiO2的量对1400℃和1450℃烧结的Al2O3陶瓷材料性能的影响.运用三点抗弯电子试验机、XRD、SEM分析了低温烧结Al2O3基陶瓷材料的力学性能和断口形貌,讨论了低温烧结Al2O3基陶瓷的烧结机理和性能.结果表明:在1450℃烧结,当不加SiO2时,弯曲强度为194 MPa;当加入0.5%(质量百分含量,下同)SiO2时,烧结Al2O3基陶瓷材料的力学性能最佳,弯曲强度为σ=299 MPa;SiO2量增加到1%时,σ=293 MPa;SiO2加入量在3%时,σ=249 MPa.SiO2的加入量从0.5%到3%对氧化铝的强度都有明显的提高,说明加入SiO2对氧化铝陶瓷的烧结是非常有利的,但随着SiO2加入量的不断加大氧化铝陶瓷力学性能有下降的趋势.     

机床用Al_2O_3/TiB_2复相陶瓷刀具材料的研究

以α-Al2O3和TiB2为主要原料,采用真空热压烧结工艺制备机床用Al2O3/TiB2复相陶瓷刀具材料。测试和分析了烧结样品的相对密度、弯曲强度、断裂韧性、硬度值、相组成以及显微结构。结果表明,当α-Al2O3添加量为75 wt%,微米TiB2添加量为20 wt%时,所制备的Al2O3/TiB2复相陶瓷刀具材料性能最佳,其相对密度值为98.8%,弯曲强度为606.25 MPa,断裂韧性为4.85 MPa·m1/2,硬度值为26.55 GPa。最佳样品的主晶相为刚玉(Al2O3)和硼化钛(TiB2),次要晶相为氧化钇(Y2O3)。     

ZrO2-Al2O3复相陶瓷的研究

采用工业ZrO2,Al2O3为原料,通过适当的工艺制备出ZrO2-Al2O3复相陶瓷.研究结果表明:添加Al2O3可有效地抑制ZrO2晶粒的生长,有利于使ZrO2晶粒以亚稳四方相存在,从而提高材料的强度与断裂韧性.Al2O3质量分数为20%时,复相陶瓷的抗弯强度、断裂韧性分别为676.7MPa,10MPa*m1/2.相变增韧与颗粒弥散增韧作用相互叠加提高了复相陶瓷材料的力学性能.     

玻璃喷雾钢化工艺研究

喷雾钢化工艺理论上比气冷钢化工艺更节能,为了探究喷雾钢化工艺的实际节能效果,本文采用尺寸为40 mm×40 mm×5 mm的平板玻璃进行了气冷钢化和喷雾钢化试验。结果表明:与气冷钢化工艺相比,喷雾钢化工艺在冷却过程中至少节能25.06%;喷雾钢化工艺可以提高玻璃的钢化程度,即破碎后的颗粒数增加了至少8.91%,表面压应力提高了至少12.12%;随着雾载分数的增加,冷却时间减少,节能效果和钢化程度提高。     

CeO_2含量对白云鄂博西尾矿为原料制备的微晶玻璃力学性能的影响

以白云鄂博西尾矿和粉煤灰为主要原料,采用熔铸法制备了高性能的CaO-MgO-Al2O3-SiO2(CAMS)系微晶玻璃。研究了不同晶化温度下CeO2含量对CAMS系微晶玻璃析晶行为、显微结构和力学性能的影响。结果表明:Ce4+离子可以置换辉石相主晶相中Ca2+形成置换固溶体;质量分数为0.6%的CeO2可以降低微晶玻璃的晶化温度、提高辉石相结晶度、促进其形成交错咬合的枝晶结构,从而提高微晶玻璃样品的抗折强度和显微硬度;过量的CeO2富集于辉石相晶间并进而形成Ca2Ce8(SiO4)6O2第二相晶间相,阻碍辉石相的形成和长大,从而使样品的力学性能有所降低。添加0.6%CeO2的微晶玻璃样品经870℃晶化2 h后,抗折强度和显微硬度分别达到234 MPa和6.982 GPa。     

TiO2和CaO-Al2O3-SiO2复合烧结助剂对刚玉陶瓷烧结的影响

在以α-Al2O3为原料的刚玉陶瓷配料中,分别添加0、0.15%、0.30%、0.45%、0.60%的TiO2和0、0.5%、1.0%、2.0%、4.0%的CaO-Al2O3-SiO2(CAS)玻璃,共组合出25组试验配方,以150MPa压力干压成型为45mm×5mm×4mm的试样,烘干后以5℃.min-1的升温速率升至1550℃保温2h烧成,然后检测烧后试样的相对密度、常温抗折强度和断裂韧性,并用扫描电镜观察烧后试样的显微结构。结果表明:引入TiO2能显著提高刚玉陶瓷的烧结致密化速率,但是引起晶粒的异向生长和异常长大,并使其断裂方式以沿晶断裂为主,试样力学性能也普遍较低;引入少量的CaO-Al2O3-SiO2易引起样品反致密化,只有CaO-Al2O3-SiO2的引入量大于1.3%才能有效地促进刚玉陶瓷的烧结,并抑制由0.6%的TiO2引起的严重的晶粒异向生长和异常长大,使材料的断裂方式向穿晶断裂转变,并使其力学性能逐渐回升。     

CaO-MgO-Al2O3-SiO2-F系可切削玻璃陶瓷的显微结构和性能

在CaO-MgO-Al2O3-SiO2-F系新型钙云母可切削玻璃陶瓷体系中,研究分析了不同显微结构对性能的影响.板条形、长径比大的晶粒相互交错地分布,通过裂纹偏转增韧,通过穿晶断裂的方式增强.同时,这种显微结构也赋予材料良好的加工性.球晶则不利于材料的加工,含球晶的玻璃陶瓷力学性能也较差.     

Silicon Carbide Platelet/Alumina Composites: II, Mechanical Properties

The mechanical properties, i.e., Young's modulus, fracture toughness, and flexural strength, of SiC-platelet/Al₂O₃ composites with two different platelet sizes were studied. Both Young's modulus and the fracture toughness of composites using small platelets (12 μm) increased with increasing SiC volume fraction. Maximum values for toughness and Young's modulus of 7.1 MPa·m^1/2 and 421 GPa were obtained for composites containing 30 vol% platelets. Composites fabricated using larger platelets (24 μm), however, showed spontaneous microcracking at SiC volume fractions of ≤0.15. The presence of microcracks decreased Young's modulus and the fracture toughness substantially. Two types of radial microcracks were identified by optical microscopy and found to be consistent with a residual stress analysis. Anisotropy in fracture toughness was identified with a crack length indentation technique. Cracks propagating in a plane parallel to platelet faces experienced the least resistance, which was the the lowest toughness plane in platelet composites with preferred orientation. Enhanced fracture toughness was found in the plane parallel to the hot-pressing direction, but no anisotropy in toughness was observed in this plane. The flexural strength of alumina showed a decrease from 610 to 480 MPa for a 30 vol% composite and was attributed to the presence of the platelets.     

Fracture behavior of glass bead-filled poly(oxymethylene) injection moldings

The mechanical properties of glass bead filled poly(oxymethylene) were investigated as a function of glass bead content and glass bead diameter using injection molded test pieces. Fracture toughness measurements were made using single edge-notched tension and single edge-notched bend specimens. The effect of notch orientation with respect to the mold fill direction on fracture toughness was studied using single gate and double gate moldings. Tensile strength and flexural modulus were measured using standard test pieces. It was found that; (i) fracture toughness of the filled and unfilled polymer was relatively independent of notch orientation, (ii) the presence of weldlines in the molded test pieces did not affect the fracture toughness of unfilled polymer or its composites, (iii) fracture toughness of filled polymer was always considerably lower than that of the unfilled polymer; fracture toughness decreased sharply with increasing bead concentration, (iv) fracture toughness was not a sensitive function of glass bead diameter; it decreased slightly as bead diameter increased, (v) strain energy release rate as measured under impact decreased with increasing bead concentration, (vi) tensile strength decreased linearly with increasing glass bead concentration and was inversely proportional to the square root of the bead diameter, (vii) weldlines did not affect the tensile strength of the polymer or its composities, (viii) flexural modulus increased linearly with increasing glass bead concentration according to the Einstein equation.     

冷却工艺对CaO-Al2O3-SiO2系微晶玻璃强度及热膨胀性能的影响

将某一固定组成的CaO-Al2O3-SiO2系玻璃烧结到一定温度后,采用不同的冷却工艺得到若干试样。通过X衍射分析、抗折强度和热膨胀系数的测定,研究了冷却温度制度对CaO-Al2O3-SiO2系微晶玻璃强度及热膨胀性能的影响。研究发现随着微晶玻璃的起始冷却温度逐渐升高,试样的抗折强度逐渐提高,热膨胀系数逐渐减小。     

热处理气氛对AIN／SiCw（Y2O3—SiO2）复合材料性能的影响

将ＡＩＮ／ＳｉＣｗ（Ｙ２Ｏ３－ＳｉＯ２）复合材料在氧气氛和氮气氛下进行热处理,研究热处理气氛对材料性能的影响,并利用ＸＲＤ、ＥＰＡ、ＳＥＭ和ＨＲＥＭ等技术分析了材料的相组成、显微结构和粒界相。结果表明：该材料在１３００℃空气中热处理,材料性能得到改善,材料的断裂强度和韧性增长幅度明显大于氮气气氛下的热处理。在空气中氧化处理对Ｙ２Ｏ３－ＳｉＯ２组成靠近其低共熔点组成的试样具有良好的增强增韧作用,可有     

Effect of plate-like glass fillers on the mechanical properties of dental nanocomposites

In this study, glass flakes were incorporated into the spherical nanosilica component of the dental composites and its effect on the mechanical properties of these composites was investigated. To achieve a good interfacial adhesion between matrix resin and fillers, the particles were surface treated with a silane coupling agent (γ-MPS). Composites with different plate-like and spherical nanoparticle contents were prepared and their mechanical properties, including flexural strength, flexural modulus and fracture toughness were measured. The morphology of the particles and fracture surface of the composites were studied by SEM. The distribution of the flakes in the composite was also monitored using EDXA. Statistical analysis of the data was performed with ANOVA and the Tukey’s post hoc test was at a significance level of 0.05. The results showed that the flexural modulus and fracture toughness of specimens were improved with increasing the glass flake content up to 15 vol % which then declined upon further increase due to the stacking of the flakes on each other. A good interfacial adhesion was observed between matrix resin and particles in the SEM micrographs. The results of this study suggest that incorporation of glass flakes into the dental composites containing spherical nanosilica particles may enhance their mechanical properties.     

Microstructural,mechanical, and thermal characteristics of recycled cellulose fiber‐halloysite‐epoxy hybrid nanocomposites

Epoxy hybrid‐nanocomposites reinforced with recycled cellulose fibers (RCF) and halloysite nanotubes (HNTs) have been fabricated and investigated. The dispersion of HNTs was studied by synchrotron radiation diffraction (SRD) and transmission electron microscopy (TEM). The influences of RCF/HNTs dispersion on the mechanical properties and thermal properties of these composites have been characterized in terms of flexural strength, flexural modulus, fracture toughness, impact toughness, impact strength, and thermogravimetric analysis. The fracture surface morphology and toughness mechanisms were investigated by SEM. Results indicated that mechanical properties increased because of the addition of HNTs into the epoxy matrix. Flexural strength, flexural modulus, fracture toughness, and impact toughness increased by 20.8, 72.8, 56.5, and 25.0%, respectively, at 1 wt% HNTs load. The presence of RCF dramatically enhanced flexural strength, fracture toughness, impact strength, and impact toughness of the composites by 160%, 350%, 444%, and 263%, respectively. However, adding HNTs to RCF/epoxy showed only slight enhancements in flexural strength and fracture toughness. The inclusion of 5 wt% HNTs into RCF/epoxy ecocomposites increased the impact toughness by 27.6%. The presence of either HNTs or RCF accelerated the thermal degradation of neat epoxy. However, at high temperature, samples reinforced with RCF and HNTs displayed better thermal stability with increased char residue than neat resin. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers     

Boron nitride nanosheets reinforced glass matrix composites

The effect of reinforcing boron nitride nanosheets (BNNSs) on the mechanical properties of an amorphous borosilicate glass (BS) matrix was studied. The BNNSs were prepared using liquid exfoliation method and characterised by transmission electron microscopy, scanning electron microscopy and X-ray diffraction (XRD) analysis. The average length was ～0.5?μm, and thickness of the nanosheets was between 4 and 30 layers. These BNNSs were used to prepare BS-BNNS composite with different loading concentrations of 1, 2.5 and 5 mass-% (i.e. 1.395, 3.705 and 7.32 vol.-%). Spark plasma sintering (SPS) was used to densify these composites to avoid structural damages to the BNNSs and/or crystallisation within the composite sample during high temperature processing. The BNNSs were found to be evenly distributed in the composites matrix and were found to be aligned in an orientation perpendicular to the direction of the applied force in SPS. The mechanical properties including fracture toughness, flexural strength and elastic modulus were measured. Both fracture toughness and flexural strength increased linearly with increasing concentration of BNNSs in BS glass. There was an enhancement of ～45% in the fracture toughness (1.10?MPa.m^1/2) as well as flexural strength (118.82?MPa) with the addition of only 5 mass-% loading of BNNSs compared to BS glass (0.76?MPa.m^1/2; 82.16?MPa). The toughening mechanisms developed in the composites because of the reinforcement of BNNSs were thoroughly investigated.     

Effect of printing parameters on mechanical properties of extrusion-based additively manufactured ceramic parts

The purpose of this study is to investigate the effect of printing parameters on the physical and mechanical properties of additively manufactured ceramics (alumina and zirconia). Sample parts were obtained by extrusion-based additive manufacturing of a ceramic-binder mixture and subsequent post-processing (debinding and sintering). Their mechanical properties (microhardness, flexural strength, toughness) were measured and correlated with the printing parameters. Part orientation is the most significant factor for microhardness and flexural strength in both ceramic materials. Parts with vertical orientation show higher hardness while horizontal samples show higher flexural strength compared to their respective counterparts. Extrusion velocity was found to be insignificant for hardness and flexural strength. However, a marginal increase in fracture toughness with the increase in the extrusion velocity was observed. The fracture toughness of additively manufactured ceramics shows an increasing trend with elastic modulus and flexural strength and a decreasing trend with hardness and sintered density.     

烧结工艺对Si_3N_4/TiC纳米复合陶瓷材料微观结构及力学性能的影响

以La2O3和Y2O3作为复合烧结助剂,采用热压烧结法制备了Si3N4基复合陶瓷材料。研究了保温时间和烧结助剂含量对复合材料微观结构及力学性能的影响。研究表明:所制备的Si3N4/TiC陶瓷复合材料的微观结构呈现纵横交错、相互嵌套的结构,晶粒尺寸呈现明显的双峰分布特征,单位面积内晶粒数量与烧结助剂含量之间呈线性降低关系。当烧结助剂质量含量为8%时,该复合陶瓷材料具有最优的力学性能,其抗弯强度、断裂韧性和Vickers硬度分别达到943MPa,8.38MPa·m1/2和16.67GPa。