Study on Acoustic Emission Characteristics of Deformation Damage Process of Zirconia Ceramics

Zirconia ceramics have become increasingly widely used in recent years and are favored by relevant enterprises. From the traditional dental field to aerospace, parts manufacturing has been used, but there is limited research on the deformation and damage process of zirconia ceramics. This article analyzes the acoustic emission characteristics of each stage of ceramic damage from the perspective of acoustic emission, and explores its deformation process characteristics from multiple perspectives such as time domain, frequency, and EWT modal analysis. It is concluded that zirconia ceramics exhibit higher brittleness and acoustic emission strength than alumina ceramics, and when approaching the fracture, it tends to generate lower frequency acoustic emission signals.

Effect of colouring green stage zirconia on the adhesion of veneering ceramics with different thermal expansion coefficients

This study evaluated the adhesion of zirconia core ceramics with their corresponding veneering ceramics, having different thermal expansion coefficients （TECs）, when zirconia ceramics were coloured at green stage. Zirconia blocks （N=240; 6 mm x 7 mm x 7 mm） were manufactured from two materials namely, ICE Zirconia （Group 1） and Prettau Zirconia （Group 2）. In their green stage, they were randomly divided into two groups. Half of the specimens were coloured with colouring liquid （shade A2）, Three different veneering ceramics with different TEC （ICE Ceramic, GC Initial Zr and IPS e.max Ceram） were fired on both coloured and non-coloured zirconia cores. Specimens of high noble alloys （Esteticor Plus） veneered with ceramic （VM 13） （n= 16） acted as the control group. Core-veneer interface of the specimens were subjected to shear force in the Universal Testing Machine （0.5 mm-min-1）. Neither the zirconia core material （P=0.318） nor colouring （P=0.188） significantly affected the results （three-way analysis of variance, Tukey＇s test）. But the results were significantly affected by the veneering ceramic （P=0.000）. Control group exhibited significantly higher mean bond strength values （45.7__.8） MPa than all other tested groups （（27.1__.4.1）-（39.7__.4.7） and （27.4__.5.6）-（35.9___4.7） MPa with and without colouring, respectively） （P^0.001）. While in zirconia-veneer test groups, predominantly mixed type of failures were observed with the veneering ceramic covering ~ 1/3 of the substrate surface, in the metal-ceramic group, veneering ceramic was left adhered 1/3 of the metal surface. Colouring zirconia did not impair adhesion of veneering ceramic, but veneering ceramic had a significant influence on the core-veneer adhesion. Metal-ceramic adhesion was more reliable than all zirconia-veneer ceramics tested.

Shear bond strengths between alumina-toughened zirconia cores and veneering ceramics and their susceptibility to aging

Objective:To evaluate the shear bond strength(SBS) between alumina-toughened zirconia (ATZ) cores and veneering ceramics,investigate the effect of aging in artificial saliva on SBS and compare it with that of yttria-stabilized tetragonal zirconia polycrystals(Y-TZP).Methods:Bars of ATZ and Y-TZP were layered with veneering ceramics in accordance to the recommendation of the manufacturer.Half of each group(n = 10) was aged at 134℃.(under 2 bar pressure) in an autoclave for 48 h.Subsequently,all specimens were subjected to shear force in a universal testing machine.The interface and fractured surface of the specimens were evaluated using scanning electron microscopy and X-ray energy dispersive spectroscopy.Results:The initial mean SBS values in MPa±SD were 28.9±8.0 for ATZ and 26.2±7.6 for Y-TZP.After aging,the mean SBS values for ATZ and Y-TZP were 22.9±4.9 MPa and 22.8±6.9 MPa,respectively.Neither the differences between the SBS values of the ATZ and Y-TZP groups nor the influence of aging on all groups were statistically significant.Conclusions:The SBS between the ATZ core and the veneering ceramics was not affected by aging.The SBS of ATZ to veneering ceramics was not significantly different compared with that of Y-TZP.

极薄氧化锆贴面的研究进展

全瓷贴面修复是改善牙齿形态、色泽和排列的常用方法。随着口腔陶瓷材料和修复体加工方式的不断发展,微创/无创贴面修复是医生和患者对牙齿修复提出的共同要求。本文回顾了全瓷贴面的发展历程和应用现状,对极薄氧化锆贴面相关的新材料、新工艺做一介绍,并对其技术前景和临床效果进行展望。

Nacre-inspired Zirconia/Carbon Nanocomposites with High Strength and Toughness

Inspired by structures of natural shells,zirconia-carbon nanocomposites were obtained by using natural chitin from shrimp shells as templates via the sol-gel route in this study.Chitin was dispersed in the water and chelated with the zirconia precursors by amidogen.After a heat treatment for carbonization,nacre-like structures of carbon-zirconia nanocomposites were successfully synthesized.Due to the toughening mechanism of tetragonal zirconia,the mechanical properties of carbon-zirconia composites are further improved.The as-received zirconia/carbon nanocomposite with best mechanical property has a hardness of 5.88GPa and an elastic modulus of 80.6 GPa,which is even stronger than natural shells.This work might facilitate a versatile platform for developing green nanocomposites with reasonably good mechanical properties.

Replacement of Unesthetic Posterior Metal Crowns with Monolithic Zirconia Crowns: A Case Report

Advances in metal-free materials and the popularization of Computer-Aided Design and Manufacturing (CAD/CAM) have led to the wide clinical use of all-ceramic crowns for esthetic restorations. A 72-year-old woman presented to our hospital with unesthetic restorations on the right upper and lower posterior teeth. Intraoral examination revealed poorly fitting metal crown margins. Defective prostheses were removed, and provisional restorations were provided to stabilize the mandibular position. Optical impressions and the maxillomandibular relationship were recorded using an intraoral scanner, and monolithic zirconia crowns were fabricated using CAD/CAM technology for complete veneer crown restorative treatment. Occlusal examination revealed an improvement in occlusal force distribution at initial examination (right side: 33.5%, left side: 66.5%) after placement of the zirconia crowns (right side: 54.9%, left side: 45.1%). Occlusal force and occlusal force distribution area also showed an increasing trend. The Oral Health Impact Profile short form (OHIP-14) score decreased from 7 points at initial examination to 0 points after prosthodontic treatment. Appropriate diagnosis and treatment planning contributed to the increased occlusal force and balanced occlusal force distribution. Therefore, the present case indicates the potential of monolithic zirconia crowns to achieve both esthetic and stable functional outcomes.

Effects of Hydrothermal Environment on the Deformation of the Thin Bamboo Bundle Veneer Laminated Composites

To overcome warping in thin bamboo bundle veneer laminated composites(TBLC),their hydrothermal deformation characteristics were systematically investigated in this study.It was found that TBLCs accelerated the release of internal stress in the thickness direction in a hydrothermal environment,which increased their warpage.TBLCs showed increased warpage in the width and diagonal directions upon increasing the temperature.The warpage of Type E increased by 155.88%and 66.67%in the width and diagonal directions,respectively,when the temperature increased from 25
C to 100
C.The symmetrical TBLC with cross-lay-up and odd layers displayed better hydrothermal stability.We revealed that the deformation of the TBLCs could be regulated under the synergistic effect of water and temperature.These results provide a scientific basis for improving the uniformity of bamboo bundle composite materials and for developing thin bamboo bundle fiber composite materials with designable structures and controllable performance.

Machine learning potential for Ab Initio phase transitions of zirconia

Zirconia has been extensively used in aerospace,military,biomedical and industrial fields due to its unusual combination of high mechanical,electrical and thermal properties.However,the fundamental and critical phase transition process of zirconia has not been well studied because of its difficult first-order phase transition with formidable energy barrier.Here,we generated a machine learning interatomic potential with ab initio accuracy to discover the mechanism behind all kinds of phase transition of zirconia at ambient pressure.The machine learning potential precisely characterized atomic interactions among all zirconia allotropes and liquid zirconia in a wide temperature range.We realized the challenging reversible first-order monoclinic-tetragonal and cubicliquid phase transition processes with enhanced sampling techniques.From the thermodynamic information,we gave a better understanding of the thermal hysteresis phenomenon in martensitic monoclinic-tetragonal transition.The phase diagram of zirconia from our machine learning potential based molecular dynamics simulations corresponded well with experimental results.

Effect of Zirconia Corundum Addition on Properties of Chrome Corundum Castables

In order to investigate the effect of zirconia corundum on the preparation of chrome corundum castables,samples were prepared using tabular corundum,white fused corundum,active alumina micropowder,chromium oxide micropowder and fused ziconia corundum particles as the main raw materials,and pure calcium aluminate cement as the binder.The effects of the fused zirconia corundum particles addition(1-0.5 mm,0,4.5%,9%,and 18%,by mass)on the linear change rate,the apparent porosity,the cold modulus of rupture,and the thermal shock resistance of chrome corundum castables were studied,and the microstructure of the samples was analyzed.The results show that:(1)with the zirconia corundum addition increasing,the permanent linear change on heating of the samples gradually increases,the apparent porosity gradually increases,the cold modulus of rupture gradually decreases,and the thermal shock resistance gradually increases;(2)according to SEM,it can be found that the phase transformation of ZrO2 after heat treatment leads to a large number of microcracks in the material.On one hand,the cold modulus of rupture of the material is reduced;on the other hand,the thermal shock resistance of the material is improved.

Preparation and Mechanical Properties of Zirconia Ceramics Doped with Different Y_(2)O_(3)Contents

The sintering behavior and mechanical properties of zirconia doped with 2.0mol%-3.0mol%Y_(2)O_(3)were studied by pressure-less sintering.The experimental results show that the densification temperature of zirconia ceramics increases gradually with the decrease of Y_(2)O_(3)doping content by which decreases the sintering driving force due to the lower oxygen vacancy concentration of the systems.Furthermore,the bending strength and fracture toughness of the prepared zirconia ceramics increase with the decrease of Y_(2)O_(3)doping content.It can be attributed to the fact that the phase stability of tetragonal zirconia decreases with the decrease of Y_(2)O_(3)doping content,which is easier to induce"phase transformation toughening"and dissipate impact energy.The relative density,bending strength and fracture toughness of 2.0 mol%Y_(2)O_(3)doped zirconia ceramics(2.0Y-ZrO_(2))sintered at 1525℃are 99.00%,1256.65±20.82 MPa and 9.85±0.13 MPa·m^(1/2),respectively.

氧化锆和氧化镧共掺杂对堇青石多孔陶瓷性能的影响

为实现堇青石相的低温合成,采用粒度为≤0.044 mm的煅烧高岭土、粒度为≤0.074 mm的烧结镁砂和d_(50)=2.6μm的二氧化硅微粉为主要原料,以分析纯的氧化锆和氧化镧为烧结助剂,以聚乙烯醇PVA溶液为结合剂,按照堇青石理论配比,在60 MPa压力下成型为φ30 mm×30 mm的试样,干燥、煅烧后制备了堇青石多孔陶瓷。研究了烧结助剂氧化锆添加量(外加质量分数为0、8%)、氧化镧添加量(外加质量分数分别为0、0.2%、0.4%、0.6%、0.8%)和煅烧温度(分别为1200、1250及1300℃)对堇青石多孔陶瓷常温物理性能、物相组成和显微结构的影响。结果表明:1)在1300℃下,当试样中引入8%(w)氧化锆和0.6%(w)氧化镧时,试样的物理性能较优;2)氧化锆和氧化镧共掺杂可在显气孔率变化较小的情况下,提高试样的力学性能,且促进堇青石相的生成;3)氧化锆和氧化镧共掺杂可一定程度上降低堇青石相的合成温度,提高试样的综合性能。

皮秒激光不同图案化处理氧化锆陶瓷对其粘接性能的影响

目的:研究皮秒激光在牙科氧化锆表面不同图案化扫描处理的结果,以及对氧化锆表面粘接性能的影响。方法:选取160例烧结氧化锆陶瓷试件,随机分为8个研究组,分别为空白对照组(A组)、喷砂对照组(B组)、皮秒激光处理组(C-H组,分别为:皮秒激光蜂窝状扫描、喷砂后皮秒激光蜂窝状扫描、皮秒激光横线状扫描、喷砂后皮秒激光横线状扫描、皮秒激光井字格状扫描、喷砂后皮秒激光井字格状扫描)。扫描电镜观察表面微观组织形貌;激光共聚焦显微镜观察3D形貌,原子力显微镜测量表面粗糙度Ra;X射线衍射仪观测表面晶相组成的转变;电子万能试验机测量抗弯强度,测定氧化锆陶瓷与自粘型树脂水门汀的剪切强度;光学体式显微镜下观察断裂模式;采用SPSS26.0对所得结果进行单因素方差分析及多重检验。结果:皮秒激光在氧化锆表面扫描后,可分别得到蜂窝状、平行的等间距横线状及等间距井字格状图案;不同图案化处理后氧化锆表面粗糙度不同,横线状B组最大,为14.92μm;激光表面处理不会导致表面晶相转变;经过皮秒激光处理后,剪切粘接强度明显增加(P<0.05),C组的粘接强度最大,为(26.86±1.53)MPa,约为A组的7.4倍;断裂模式由A组与B组的完全粘结破坏转变为内聚破坏和混合破坏;激光处理后的氧化锆陶瓷抗弯强度满足临床应用要求。结论:皮秒激光对氧化锆表面进行图案化处理能够提高氧化锆与树脂水门汀的粘接强度,是一种有前景的氧化锆表面改性方法。

纳米纤维素改性染料溶液及其染色单板耐光色牢度性能

采用纳米纤维素晶体(cellulose nanocrystal,CNC)对红、黄、蓝三种酸性染料进行改性处理得到CNC改性染液,对其粒径分散性、Zeta电位、紫外-可见光吸收性能进行分析,并对染色单板的上染率、耐光色牢度、表面化学结构和微观结构进行研究。结果表明:经过CNC改性处理后的三种染料,分散均匀性和稳定性均得到改善。经CNC-1%改性后的染料,粒径降低,粒径分布均匀性和Zeta电位绝对值提高,紫外-可见光吸收强度下降;染色单板的上染率提高,耐光色牢度达到GB/T 15104—2021《装饰单板贴面人造板》4级要求;染色单板微观结构表面具有纳米纤维素与染料复合形成的纤丝状聚集体。较高添加量(CNC-4%)的CNC会增大对染料的吸附量,导致胶体颗粒增大,团聚情况增加,反而使粒径变大,Zeta电位绝对值降低,从而影响单板的上染率和耐光色牢度。

桉木单板背面裂隙率对胶合板性能的影响

为给胶合板生产过程的组坯工艺优化提供理论依据,采用图像处理技术与宏观力学性能试验相结合,分析桉木单板背面裂隙率对胶合板性能的影响,探讨桉木单板背面裂隙率与胶合板性能的相关性。结果表明,不同单板背面裂隙率下,干状、冷水浸泡24 h和热水浸泡3 h胶合板的胶合强度及顺纹静曲强度均差异极显著,横纹静曲强度、横纹弹性模量和顺纹弹性模量均差异不显著。随单板背面裂隙率增大,胶合板在3种条件下的胶合强度、顺纹静曲强度和顺纹弹性模量均呈下降趋势。相关性分析表明,单板背面裂隙率与干状胶合强度、冷水浸泡24 h胶合强度和顺纹静曲强度均呈极显著负相关,与顺纹弹性模量呈显著负相关。单板背面裂隙率对胶合板性能的影响表现为冷水浸泡24 h胶合强度>干状胶合强度>顺纹静曲强度>顺纹弹性模量>热水浸泡3 h胶合强度>横纹弹性模量>横纹静曲强度。

不同清洁方法对高透氧化锆粘接强度和表面润湿性的影响

目的:研究不同清洁方法对唾液污染的高透氧化锆与自粘接树脂水门汀间剪切粘接强度和表面润湿性的影响。方法:制备80个高透氧化锆试件,随机分为5组(n=16),即对照组(无污染处理)、75%乙醇组、喷砂组、清洁剂组和大气压冷等离子体处理组等。测量表面接触角,测试剪切粘接强度,观察断裂模式。采用SPSS 26.0软件包对数据进行统计学分析。结果:大气压冷等离子体组的接触角最小(P<0.05);喷砂组、清洁剂组及大气压冷等离子体组的剪切粘接强度与对照组相比,无统计学差异(P>0.05),但均显著大于75%乙醇组(P<0.05);大气压冷等离子体组混合断裂模式增多。结论:喷砂、清洁剂及大气压冷等离子体清洁唾液污染的高透氧化锆,可获得与未被唾液污染前相当的粘接强度;大气压冷等离子体可显著提高高透氧化锆的表面润湿性。

二氧化锆全瓷冠修复前牙的效果及对局部炎症状态的影响

目的:探究及观察二氧化锆全瓷冠修复前牙的效果及对局部炎症状态的影响。方法:选取2019年1月—2021年1月深圳市龙岗区妇幼保健院口腔科的100例需进行前牙冠修复的患者为研究对象,根据随机数字表法分为对照组(镍铬合金烤瓷冠组)和观察组(二氧化锆全瓷冠组),每组50例。比较两组的修复效果(颜色匹配度、完整度及边缘密合度)、不良情况发生率、局部炎症状态指标[龈沟液炎症因子白介素-1β(IL-1β)及白介素-6(IL-6)、炎症介质前列腺素E2(PGE2)]、炎症趋化因子[调节活化正常T细胞表达和分泌因子(RANTES)]、患者满意度。结果:观察组的颜色匹配度、完整度及边缘密合度均显著优于对照组,不良情况发生率显著低于对照组,差异均有统计学意义(P<0.05)。治疗前,两组的局部炎症状态指标比较,差异均无统计学意义(P>0.05);治疗后3、6个月,观察组的局部炎症状态指标均显著优于对照组,患者满意度显著高于对照组,差异均有统计学意义(P<0.05)。结论:二氧化锆全瓷冠修复前牙的效果较好,且可有效控制患者的局部炎症状态,更受患者认可。

微胶囊释香饰面板的制备及其香气缓释性能评价

【目的】制备稳定、持久释香的饰面板,并建立缓释性能评价方法,实现规模化生产。【方法】采用微胶囊和树脂复合包覆方法制备释香型浸渍胶膜纸饰面板;采用固相微萃取-气相-质谱联用技术(solid-phase microextraction-gas chromatography-mass spectrometry,SPME-GC-MS),通过人工嗅闻直测法和气味分级法分析了释香饰面板在50℃下480 h的加速释香过程,揭示其香气释放机制,并建立香气缓释性能的快速评价方法。【结果】添加0.75%释香微胶囊的饰面板释香效果最优;微胶囊经热压后仍能均匀分布在胶层的表面和内部,壁材和胶层起到协同缓释香气的作用,且香气主成分(芳樟醇)的释放与温度、时间呈正相关。【结论】制备了持久、稳定释香的饰面板,并通过香气加速释放和干燥器富集法建立了香气缓释性能快速评测方法。

钨钼烧结炉用氧化锆质顶盖结构的优化研究

结合当前钨钼烧结炉用氧化锆顶盖砖的使用情况,利用ANSYS软件,模拟分析了氧化锆顶盖砖异常损坏的原因,并通过对不同厚度、不同体积密度顶盖砖使用过程中应力场的模拟研究,对顶盖砖结构优化进行了探索。结果表明:顶盖砖在使用过程中的最大拉应力为27MPa,远远超过了材料的结合强度,从而造成“断裂”和“龟裂”,导致寿命降低;顶盖砖的体积密度和厚度对其使用过程中的热应力有着显著的影响,当氧化锆顶盖砖的体积密度在3.0~4.6g/cm^(3)时,降低体积密度可以减小顶盖砖使用过程中的热应力,综合体积密度对氧化锆空心球砖其他性能的影响,将当前用顶盖砖的体积密度提高至3.3g/cm^(3),厚度减薄至50mm时,顶盖砖使用过程中的最大热应力只有10.27MPa,而顶盖砖的抗折强度达到13.6MPa,从而有效改善其使用寿命。

氧化锆增强铝基复合材料的制备及性能研究

铝合金由于其强度高、质量轻、价格低等多重优势,在汽车制造、航空航天、水下装备等各个领域都极具应用前景。利用机械搅拌铸造方法制备了不同质量分数纳米氧化钇稳定氧化锆(yttrium oxide stabilized zirconia,YSZ)的Al-YSZ复合材料,研究纳米YSZ质量分数对铝基复合材料组织和性能的影响。研究结果表明,添加的纳米YSZ均匀分布在Al基体中,不与Al基体发生反应。同时能够作为异质形核剂细化晶粒,并通过Orowan强化机制提升复合材料的力学性能。添加质量分数为8%的纳米YSZ的复合材料具有较好的强度和塑性。同时,在受到外力作用时,纳米YSZ会发生从四方到单斜的相变,并产生一定的体积膨胀,在吸收能量的同时改善了复合材料内部的晶格畸变,从而提高了铸态复合材料的塑性。

单轴拉伸下YSZ纳米柱变形机制及力学性能的分子动力学研究

采用分子动力学方法,研究了单晶氧化钇稳定四方氧化锆(YSZ)纳米柱在单轴拉伸下的变形机制。模拟结果表明,YSZ的纳米塑性变形强烈依赖于氧化锆纳米柱的晶体取向,[001]晶向的YSZ纳米柱在拉伸载荷下可以观察到四方相向单斜相相变的结果。在低应变速率状态下,低应变速率不会影响YSZ纳米柱的力学性能,包括杨氏模量、强度和屈服应变,以及主要的变形机制。此外,以四方到单斜相变为主的YSZ纳米柱对力学性能有很强的尺寸效应,YSZ的强度随纳米柱尺寸的减小而降低。