Maximum Shrinkage Rate Research Articles

3D micro-CT and O-PTIR spectroscopy bring new understanding of the influence of filler content in dental resin composites

BackgroundDental resin composites' performance is intricately linked to their polymerisation shrinkage characteristics. This study compares polymerisation shrinkage using advanced 3D micro-computed tomography (micro-CT) and traditional 2D linear assessments. It delves into the crucial role of filler content on shrinkage and the degree of conversion in dental resin composites, providing valuable insights for the field. MethodsFive experimental dental composite materials were prepared with increasing filler contents (55–75 wt%) and analysed using either 3D micro-CT for volumetric shrinkage or a custom-designed linometer for 2D linear shrinkage. The degree of conversion was assessed using Optical Photothermal Infrared (O-PTIR) and Fourier-Transform Infrared (FTIR) spectroscopy. Light transmittance through a 2-mm layer was evaluated using a NIST-calibrated spectrometer. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX) examined surface morphology and elemental distribution. Correlation between the investigated parameters was determined using Spearman correlation analyses. ResultsThe study found significant differences in polymerisation-related properties among different filler content categories, with volumetric shrinkage consistently demonstrating higher mean values than linear shrinkage across most groups. Volumetric shrinkage decreased with increasing curing depth, showing no direct correlation between filler content and shrinkage levels at different curing depths. The results highlighted a strong negative correlation between filler content and degree of conversion, volumetric and linear shrinkage, as well as maximum shrinkage rate. Light transmittance showed a moderate correlation with the filler content and a weak correlation with other tested parameters. ConclusionsThis study underscores the importance of considering both volumetric and linear shrinkage in the design and analysis of dental composite materials. The findings advocate optimising filler content to minimise shrinkage and enhance material performance. Integrating micro-CT and O-PTIR techniques offers novel insights into dental composites' polymerisation behaviour, providing a foundation for future research to develop materials with improved clinical outcomes.

Thermomechanical and thermodynamic analysis of the sintering process of Mn-based oxygen carrier in chemical looping gasification of biomass

The Mn-based oxygen carrier (OC) owns a great oxygen carrying capacity and a high reactivity in the chemical looping gasification of biomass. However, the sintering of the Mn-based OC can cause serious defluidization or even the shut-down of the biomass chemical looping gasifier. In this study, the sintering kinetics and mechanism of Mn-based OC in the gasification of two typical biomass ash were revealed by thermomechanical and thermodynamic analysis. It revealed that the manganese silicate was converted to iwakiite (MnFe2O4) and liquid at high temperatures in the high-Mn OC (OC2), leading to the liquid sintering mechanism and high apparent activation energy of sintering (Es), with a maximum shrinkage rate of 6.14 %/oC. Conversely, the solid sintering mechanism of the low-Mn OC (OC1) was attributed to the FeMn2O4 crystallization, leading to a low shrinkage rate (The maximum shrinkage rate was 0.30 %/oC). The sintering rate of Mn-based OC was closely related to the liquid content, and the biomass ash addition advantaged the liquid formation. Therefore, the Es of OC1 was increased from 44 kJ/mol to 151 kJ/mol at the 15 wt% addition of corn straw ash, and Es of OC2 was increased from 72 kJ/mol to 93–107 kJ/mol at 20 wt% addition of biomass ash. Element distribution analysis supported that Ca in sawdust ash improved the bonding between Mn and Si, improving the Mn-based minerals crystallization and OC expansion. However, the K in corn straw ash facilitated the melting of rhodonite(MnSiO3), and the expansion of Mn-based OC was inhibited. This study provides valuable insights into the sintering mechanism of the Mn-based oxygen carrier and its relationship with liquid evolution behavior in the chemical looping gasification of biomass.

Study on the Stress Distribution and Stability Control of Surrounding Rock of Reserved Roadway with Hard Roof

According to field observation and theoretical analysis, the failure of the 1523103 reserved roadway is mainly affected by the lateral support pressure, rock mass strength, and support mode. With the mining of the 152309 working face, the lateral pressure of coal pillars on both sides of the reserved roadway increases, and since the lithology of the two sides and the floor of the roadway is weak, the reserved roadway experiences spalling and floor heave. Through numerical simulation, the distribution law of surrounding rock stress and the displacement of surrounding rock are obtained after the roof cutting and pressure relief of the reserved roadway with hard roof. According to the cause of surrounding rock failure of a reserved roadway, the combined control technology of roof cutting and pressure relief, grouting anchor cable support, and bolt support is put forward. After cutting the roof and releasing the pressure on the working face, the lateral support pressure of the two sides of the roadway is significantly reduced, the deformation of the two sides of the roadway is small, the maximum shrinkage rate of the section is reduced from 70% to 11%, and the deformation of the surrounding rock of the 1523103 reserved roadway is effectively controlled. The successful control of the surrounding rock in the 1523103 tunnel reduces the number of coal pillars to be installed, improves the coal extraction rate, and is conducive to the sustainable utilization of limited natural resources and the sustainable development of the coal industry.

The densification behavior, microstructure, mechanical, and thermionic emission properties of LaB6‐SiC composite

AbstractThe LaB6‐SiC composite with the different SiC content (0, 15, 30, 36, 50, 90, and 100 wt.%,) was densified by spark plasma sintering. The effects of SiC content on the densification behavior, microstructure, mechanical, and thermionic emission properties of LaB6‐SiC composite were systemically investigated. The results show that all the rapid shrinkage occurred at the heating stage during densification, and LaB6‐36 wt.%SiC composite owned the maximum shrinkage rate of 1.5 mm/min at T = 1798°C. The highest relative density of the composite decreased from 98.18% to 95.01% as the SiC content increased from 15 wt.% to 90 wt.%, under which the morphology of LaB6 grain evaluated from the equiaxed to elongated structure, and LaB6 grain size varied in the range of 5.05–11.42 μm. The similar eutectic structures were observed in the LaB6‐36 wt.% SiC composite because of some LaB6 grains melting. Both the highest fracture toughness of 5.15 ± 0.56 MPa.m1/2 and the highest bending strength of 313 ± 4.7 MPa belonged to the LaB6‐36 wt.% SiC composite, which also exhibited thermionic emission current density of 10.74 A/cm2 and work function of 2.99 eV at T = 1873 K.

Study on controllable preparation of high performance andradite based glass-ceramics by harmful iron-rich waste slag

Due to containing abundant FeOx and trace heavy metals (Pb, As, Cr, Cd, etc.), the disposal of lead/zinc smelting slag (LSS-ZSS) with ultra-high historical reserves has attracted increased attention. Using LSS-ZSS to prepare glass-ceramics is a good method to solve the problem of LSS-ZSS accumulation and realize heavy metal solidification, whereas there are some technical challenges that are difficult to deal with. A large amount of FeOx component in LSS-ZSS would not only lead to melt overflow, but also cause early crystallization of basic glass. In this work, through the directional modification of LSS-ZSS and the subsequent crystallization kinetics regulation, we successfully prepare high performance glass-ceramics with andradite and hematite as the main crystal phases. In addition, by means of SEM, PXRD, FTIR spectra and XPS, the morphology/phase transformation, fine structure and valence variations of iron components in LSS-ZSS at different temperature zones are systematically studied. The maximum shrinkage rate of resultant basic glasses is 27 %, and the maximum flexural strength and compressive strength of glass-ceramics are 128 MPa and 890 MPa, respectively. This work would not only benefit to solve the problem of resource utilization of harmful LSS-ZSS, but also provide a possible reference for the utilization of iron-rich waste slag in magnetic properties related fields.

EUS-derived maximum tumor thickness and tumor shrinkage rate as independent prognostic factors in locally advanced esophageal squamous cell carcinoma after neoadjuvant chemoradiotherapy.

EUS-derived maximum tumor thickness (MTT) pre- and post-neoadjuvant chemoradiotherapy (NCRT) for locally advanced esophageal squamous cell carcinoma (LA-ESCC) indicates treatment response. However, the accuracy of predicting long-term survival remains uncertain. This study aimed to investigate the association between EUS-derived MTT pre- and post-NCRT and tumor shrinkage rate as well as long-term survival in patients with LA-ESCC receiving NCRT. We retrospectively enrolled patients with LA-ESCC who underwent EUS examination from 2017 to 2021. Tumor shrinkage rate was the ratio of the difference between pre- and post-MTT to pre-MTT. The most fitted cutoff values were determined by the receiver operating characteristic curve. Univariate and multivariate Cox regression analyses and Kaplan-Meier curves were used to calculate overall survival (OS) and progression-free survival. Data from another center were also used for external validation testing. Two hundred thirty patients were enrolled. Of the patients, 178 completed the first EUS pre-NCRT and obtained pre-MTT, 200 completed the reexamined EUS post-NCRT and obtained post-MTT, and 148 completed both EUS and achieved tumor shrinkage. For all the patients, the 1- and 3-year OS rates were 93.9% and 67.9%, and progression-free survival rates were 77.7% and 54.1%, respectively. The median follow-up period was 30.6 months. Thinner post-MTT (≤8.8 mm) and EUS responder (tumor shrinkage rate ≥52%) were independently associated with better OS. EUS-derived MTT and tumor shrinkage post-NCRT are independent prognostic factors for long-term survival and may be an alternative method for evaluating tumor response in patients with LA-ESCC after NCRT.

Wrapping Objects with an Automatic Contraction Ring

The rubber band gripper is an automatic contraction ring that is used to wrap and fix objects of various shapes by vacuuming the inside of the ring. It can be used to handle objects as a robot gripper, as well as fix bodies to pedestals, and objects to bodies. This study geometrically analyzes object shapes that can be wrapped using the ring, without causing gaps in the gripping mechanism. The analysis and experimental results show that the object shapes that can be wrapped without gaps are determined by the maximum shrinkage rate after the ring contacts the object as well as the circumference of the object. The range of object shapes that can be wrapped without gaps narrows as the object position moves away from the center of the ring. However, this influence is small, except when the object is small or has a large aspect ratio. In particular, when the object shape is cylindrical, it can be wrapped without gaps regardless of its position within the ring.

Polymerization and shrinkage kinetics and fracture toughness of bulk-fill resin-composites.

To determine degree of conversion (DC), maximum polymerization rate (RPmax), polymerization shrinkage (PS), maximum shrinkage rate (PS Rmax) and fracture toughness (KIC) of different types of bulk-fill (BF) composites plus the effect of viscosity reduction techniques. BF specimens were created in 2 mm deep molds: SonicFill 3 (SF3), Viscalor (VC), One Bulk Fill (OBF) and Beautifil Bulk (BBR). SF3 was applied via sonic insertion using a SonicFill handpiece (Kerr Corp. USA). Viscalor was pre-heated in a Caps Warmer in T3 mode (at 68 °C) for 30 s (T3-30 s) and 3 min (T3-3 min), respectively. Specimens were irradiated at zero distance from the upper surface with an Elipar S10 LED unit (3 M ESPE, USA) of mean irradiance 1200 mW/cm2 for 40 s. Real-time polymerization kinetics and DC at 5 min and 24 h post-irradiation (DC5 min and DC24 h) were measured using ATR-FTIR (n = 3). PS was measured up to 1 h on 1 mm thick discs via the bonded-disk technique (n = 3) and PS Rmax obtained by numerical differentiation (n = 3). For fracture toughness, single-edge-notched specimens (32 × 6 ×3 mm) of each BF composite were prepared and measured by three-point bending after 7 d water storage (n = 5). Data were analysed using One-way ANOVA, independent T-tests and Tukey post-hoc tests (p < 0.05). SF3 showed the significantly highest DC5 min, DC24 h and RPmax (p < 0.05), followed by OBF (p < 0.05). Regardless of pre-heating, VC showed comparable conversion kinetics to BBR (p > 0.05). There was no significant difference in PS of these BF composites, except OBF had the highest PS (p > 0.05). However, PS Rmax significantly varied among materials (p = 0.047) and SF3 had the highest PS Rmax. Regarding fracture toughness, BBR had the lowest KIC (p < 0.05), whereas other composites showed similar KIC (p > 0.05). Strong correlations of filler content (wt%)-PS/KIC were found. Different pre-heating times had no significant influences on DC %, RPmax, PS, PS Rmax and KIC of VC (p > 0.05). Different types of bulk-fill composites showed comparable shrinkage. A highly filled BF giomer composite (BBR) had the lowest fracture toughness, whereas others had similar KIC. Pre-heating had no adverse effects on Viscalor properties. Sonication and pre-heating are beneficial techniques to enhance composite flowability without either increasing shrinkage or reducing fracture toughness.

Sintering kinetics and properties of NiFe2O4‐based ceramics inert anodes doped with TiN nanoparticles

AbstractSintering kinetics of NiFe2O4‐based ceramics inert anodes for aluminum electrolysis doped 7 wt% TiN nanoparticles were conducted to investigate densification and grain growth behaviors. The linear shrinkage increased gradually with the increasing sintering temperature between 1000 and 1450°C, whereas the linear shrinkage rate exhibited a broad peak. The maximum linear shrinkage rate was obtained at 1189.4°C, and the highest densification rate was achieved at the relative density of 75.20%. Based on the pressureless sintering kinetics window, the sintering process was divided into the initial stage, the intermediate stage, and the final stage. The grain growth exponent reduced with increased sintering temperature, whereas the grain growth activation energy decreased by increasing sintering temperature and shortening dwelling time. The grain growth was mainly controlled by atomic diffusion. NiFe2O4‐based ceramics possessed high‐temperature semiconductor essential characteristics. The electrical conductivity of NiFe2O4‐based ceramics first increased and then decreased with increasing sintering temperature, reached their maximum value (960°C) of 33.45 S/cm under 1300°C, mainly attributed to the relatively dense and uniform microstructure. The thermal shock resistance of NiFe2O4‐based ceramic was improved by a stronger grain boundary bonding strength and lower coefficient of linear thermal expansion.

Effect of Sewage Sludge Addition on Microstructure and Mechanical Properties of Kaolin-Sewage Sludge Ceramic Bricks

The dramatic increase in sewage sludge production requires researchers to develop and explore more commercially viable ways for alleviating current environmental and socioeconomic challenges connected with its routine management. It has been established that sewage sludge can be processed to fabricate various valuable products or as fuels for electricity generation. In this research, kaolin (calcined from coal gangue) and sewage sludge were successfully used to prepare porous ceramic bricks without any additives. The effect of sewage sludge on the microstructure, phase composition, and mechanical properties of kaolin-sewage sludge ceramic bricks was investigated. The results show that the kaolin-sewage sludge ceramic bricks are mainly composed of mullite (3Al2O3·2SiO2), sillimanite (Al2SiO5), aluminum phosphate (AlPO4), hematite (Fe2O3) as well as a small amount of quartz (SiO2). The ceramic bricks present a typical porous structure, and the number and size of micropores increases noticeably with the increase of sewage sludge content. The sintering shrinkage rate and porosity of ceramic bricks increased significantly with the increase of sewage sludge content, which is mainly attributed to the increase of liquid phase proportion and high temperature volatilization. Sewage sludge can significantly improve the mechanical properties of kaolin-sewage sludge ceramic bricks. When the sewage sludge content is 30 wt.%, the ceramic bricks present the maximum compressive strength and flexural strength and high porosity (32.74%). The maximum sintering shrinkage rate and porosity are 12.17% and 40.51%, respectively.

Large Thermal Expansion LTCC System for Cofiring with Integrated Functional Ceramics Layers.

We have studied the sintering behavior of CT708 LTCC tapes with large CTE of 10.6 ppm/K. This low-k dielectric LTCC material is a quartz-based glass ceramic composite system with partial crystallization of celsian upon firing. The shrinkage, densification and dielectric properties were examined using different heating rates and a sintering temperature of 900 °C. The maximum shrinkage rate is at 836 °C (for a heating rate of 2 K/min) with a sintering density of 95% and a permittivity of ε’ = 5.9 and tan δ = 0.0004 (at 1 GHz). Due to their similar shrinkage and thermal expansion properties, CT708 tapes may be cofired with functional ceramic layers. As an example, we report on cofiring of a multilayer laminate of CT708 and a Sc-substituted hexagonal ferrite for applications as integrated microwave circulator components. This demonstrates the feasibility of cofiring of functional ceramic tapes and tailored LTCC tapes and documents the potential for the realization of complex LTCC multilayer architectures.

Sintering and microstructure evolution of Er1.5Y1.5-xScx+yAl5-yO12 garnet ceramics with scandium in dodecahedral and octahedral sites

The sintering behavior of scandium-containing garnet materials within the Y2O3-Er2O3-Sc2O3-Al2O3 system was investigated. Single-phase ceramic powders and optical ceramics’ samples of Er1.5Y1.5-xScxScyAl5-yO12 (x = 0.2 ÷ 1.5; y = 0.2 ÷ 0.8) were prepared. An increase of scandium content in the dodecahedral garnet site has led to a temperature decrease of the shrinkage onset and the maximum shrinkage rate, as well as vacuum sintering temperatures narrowing. The decomposition of solid solutions with a high scandium dodecahedral content, accompanied by an optical quality deterioration due to mechanical mixtures formation, has been detected. According to the SEM data, the decomposition processes are accompanied by abnormal grains growth. Optical ceramics’ samples transmission coefficients were about 80% in the visible and near-IR ranges. An unique “SAG:Er” material (Er1.5Sc1.7Al4.8O12), characterized by the minimum dodecahedral radius and the unit cell parameter compared to the known erbium-doped garnet matrixes has been obtained.

Geometrical Comparison and Quantitative Evaluation of 18F-FDG PET/CT- and DW-MRI-Based Target Delineation Before and During Radiotherapy for Esophageal Squamous Carcinoma.

Background and PurposeThis study aimed to evaluate the geometrical differences in and metabolic parameters of 18F-fluorodeoxyglucose positron emission tomography–computed tomography (18F-FDG PET-CT) and diffusion-weighted magnetic resonance imaging (DW-MRI) performed before and during radiotherapy (RT) for patients with esophageal cancer based on the three-dimensional CT (3DCT) medium and explore whether the high signal area derived from DW-MRI can be used as a tool for an individualized definition of the volume in need of dose escalation for esophageal squamous cancer.Materials and MethodsThirty-two patients with esophageal squamous cancer sequentially underwent repeated 3DCT, 18F-FDG PET-CT, and enhanced MRI before the initiation of RT and after the 15th fraction. All images were fused with 3DCT images through deformable registration. The gross tumor volume (GTV) was delineated based on PET Edge on the first and second PET-CT images and defined as GTVPETpre and GTVPETdur, respectively. GTVDWIpre and GTVDWIdur were delineated on the first and second DWI and corresponding T2-weighted MRI (T2W-MRI)-fused images. The maximum, mean, and peak standardized uptake values (SUVs; SUVmax, SUVmean, and SUVpeak, respectively); metabolic tumor volume (MTV); and total lesion glycolysis(TLG) and its relative changes were calculated automatically on PET. Similarly, the minimum and mean apparent diffusion coefficient (ADC; ADCmin and ADCmean) and its relative changes were measured manually using ADC maps.ResultsThe volume of GTVCT exhibited a significant positive correlation with that of GTVPET and GTVDWI (both p < 0.001). Significant differences were observed in both ADCs and 18F-FDG PET metabolic parameters before and during RT (both p < 0.001). No significant correlation was observed between SUVs and ADCs before and during RT (p = 0.072–0.944) and between ∆ADCs and ∆SUVs (p = 0.238–0.854). The conformity index and degree of inclusion of GTVPETpre to GTVDWIpre were significantly higher than those of GTVPETdur to GTVDWIdur (both p < 0.001). The maximum diameter shrinkage rate (∆LDDWI) (24%) and the tumor volume shrinkage rate (VRRDWI) (60%) based on DW-MRI during RT were significantly greater than the corresponding PET-based ∆LDPET (14%) and VRRPET (41%) rates (p = 0.017 and 0.000, respectively).ConclusionBased on the medium of CT images, there are significant differences in spatial position, biometabolic characteristics, and the tumor shrinkage rate for GTVs derived from 18F-FDG PET-CT and DW-MRI before and during RT for esophageal squamous cancer. Further studies are needed to determine if DW-MRI will be used as tool for an individualized definition of the volume in need of dose escalation.

Effects of Al2O3–ZrO2 content on the densification, microstructure, and mechanical properties of cemented tungsten carbides

In order to prepare cobalt-free cemented carbide by liquid phase sintering, various contents of Al2O3–ZrO2 by eutectic ratio were utilized as binders for tungsten carbides. The effects of Al2O3–ZrO2 content on the densification, microstructure, mechanical properties, and interfacial characteristics of these binderless tungsten carbides were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), high–resolution transmission electron microscopy, and mechanical properties tests. The fully dense WC toughened by Al2O3–ZrO2 composite powders could be consolidated through spark plasma sintering at 1600 °C. The results indicated that a small amount of eutectic Al2O3–ZrO2 binder phase (up to 3 wt%) would aggregate, increasing the contact chance of WC particles and eventually leading to abnormal growth of WC grains. When the Al2O3–ZrO2 content increases to 6.0 wt%, the abnormal growth of WC particles was inhibited by the pinning effect of the well-distributed second phase. The mean grain size of WC decreased with the increasing amount of Al2O3–ZrO2 content, while the mean grain size of Al2O3–ZrO2 colony increased. The temperature corresponding to the maximum shrinkage rate of densification process decreased with increasing Al2O3–ZrO2 content. In general, with the increase of the eutectic ceramic content, the hardness of the composite decreased and the indentation fracture toughness increased. The toughening mechanisms include crack deflection, crack bridging and t– to m–ZrO2 phase transformation toughening. The WC–Al2O3–ZrO2 composites show maximum toughness of approximately 10.5 MPa m1/2 and hardness value of 22.29 GPa, respectively.

Experimental and theoretical study on the resistive properties of LaCo0·4Ni0·6O3 ceramic with Mg-ion substitution

To explore an air-fireable and economically functional phase for thick-film resistors, the crystal structure, microstructure, sintering, and resistive properties of LaCo0·4Ni0.6−xMgxO3 (LCNM, x = 0.00–0.08) ceramics are studied in this paper, based on solid-state reaction experiments and theoretical calculations. With Mg-ion increase, the impurity phases of NiO and La3Ni4O10 increased, the maximum shrinkage rate occurred at a higher temperature, and the microstructures became worse. The addition of the Mg ion increased the resistivity and decreased the temperature coefficient of resistivity (TCρ). The calculation results, including the bond population, electron density distribution, and density of states of the system agreed with the change in experimental resistivity. Relatively low resistivity and TCρ with a small absolute value could be achieved for specimens with x ≤ 0.02 sintered at 1200 °C and 1250 °C. Hence, the LCNM (x ≤ 0.02) ceramics are possible functional material for thick-film resistors.

Effect of TiN content on properties of NiFe2O4‐based ceramic inert anode for aluminum electrolysis

AbstractNiFe2O4‐based ceramic inert anodes for aluminum electrolysis doped with various TiN nanoparticles were prepared by a two‐step cold‐pressing sintering process to investigate how TiN affected the sintering behavior and properties of the composites. The differential scanning calorimetry‐thermogravimetry (DSC‐TG), X‐ray diffraction (XRD), and microstructure analysis results indicated that the Ti and N were evenly distributed in the NiFe2O4 matrix to form a solid solution. The maximum linear shrinkage and linear shrinkage rate were enhanced with the increase of TiN nanoparticles contents, and the sintering activation energy of initial stage was lowered from 382.63 to 279.58 kJ mol−1 with the TiN nanoparticles additive range from 0 to 9 wt%. When the content of TiN nanoparticles was 7 wt%, the relative density, bending strength, and elastic modulus reached their maximum values of 97.24%, 73.88 MPa, and 3.77 GPa, respectively, whereas the minimum static corrosion rate of NiFe2O4‐based ceramic of 0.00114 g cm−2 h−1 was obtained, mainly attributed to the relatively dense and stable microstructure. The electrical conductivity of NiFe2O4‐based ceramics presented a clear ascending trend with increasing TiN nanoparticles content and elevated temperature, attributed to the increased concentration and migration rate of carrier.

Polymerization shrinkage and shrinkage stress development in ultra-rapid photo-polymerized bulk fill resin composites

ObjectiveTo determine the polymerization shrinkage (%) and shrinkage stress (MPa) characteristics of ultra-rapid photo-polymerized bulk fill resin composites. MethodsTwo ultra-rapid photo-polymerized bulk fill (URPBF) materials: PFill and PFlow were studied, along with their comparators ECeram and EFlow. PFill contains an addition fragmentation chain transfer (AFCT) agent. The URPBR materials were irradiated using two different 3 s high irradiance protocols (3000 and 3200 mW/cm2 based on Bluephase PowerCure and VALO LCUs, respectively) and one 10 s standard protocol (1200 mW/cm2 based on a Bluephase PowerCure LCU). Bonded disk and Bioman II instruments were used to measure Polymerization shrinkage % and shrinkage stress MPa, respectively, for 60 min at 23 ± 1 °C (n = 5). Maximum shrinkage-rate and maximum shrinkage stress-rate were also calculated for 15 s via numerical differentiation. The data were analyzed via multiple One-way ANOVA and Tukey post-hoc tests (α = 0.05). ResultsPFill groups, regardless of their irradiance protocol, showed significantly lower PS than the comparator, ECeram (p < 0.05). However, PFlow irradiated via different protocols, was comparable to EFlow and ECeram (p > 0.05). PFill consistently produced stress results which were significantly lower than ECeram (p < 0.05) and were comparable for both high irradiance protocols (p > 0.05). PFlow only exhibited significantly higher shrinkage stress when polymerized with the 3 sVALO protocol (p < 0.05).The maximum shrinkage strain-rate (%/s) was significantly lower in PFill-10s and PFill-3s groups (using PowerCure LCU) compared to ECeram. However, no differences were seen between PFlow and EFlow (p > 0.05). The maximum shrinkage stress-rate of PFill and PFlow was comparable between different irradiation protocols, as well as to their comparator ECeram (p > 0.05). SignificanceHigh irradiation protocols over ultra-short periods led to slightly lower shrinkage strain but slightly higher stress, possibly due to reduced network mobility. The AFCT agent incorporated in PFill composite seemed to reduce shrinkage stress development, even with high irradiance protocols.

High aneurysm wall enhancement values are associated with late sac shrinkage after endovascular repair of abdominal aortic aneurysms.

To analyze the correlation between aneurysm wall enhancement (AWE) values and early and late sac shrinkage after endovascular aneurysm repair (EVAR).We retrospectively analyzed 28 patients who underwent EVAR for abdominal aortic aneurysms (AAA) using a bifurcated main body stent graft. The value of AWE in the slice of the maximum AAA diameter was measured using a volumetric analysis of computed tomography images. Sac measurements before EVAR and more than 10 months after EVAR were compared, and the maximum sac shrinkage rate was calculated.The AWE value immediately after (4 to 7 days) EVAR correlated positively with the sac shrinkage rate (R2 = 0.0139). The AWE value at 6 months after EVAR was also strongly correlated with the sac shrinkage rate (R2 = 0.4982).Higher AWE values at 6 months after EVAR were strongly associated with the sac volume shrinkage rate. High AWE values may be a predictive factor for sac shrinkage and may aid in the selection of the appropriate clinical strategy after EVAR.

Microstructural characteristics and mechanical behavior of microwave-assisted sintered ferromagnetic FeCoNi1.5CrCu HEAp/Al matrix composites

The preparation of metal particle reinforced aluminum matrix composites by powder metallurgy has been widely studied in recent years. In this work, the effect of microwave sintering temperature on the microstructure and mechanical behavior of high-entropy alloys (HEAs) reinforced aluminum matrix composites prepared by powder metallurgy was investigated. Due to the outstanding microwave absorbing property of ferromagnetic HEAs particles, the composites sintering proceeded efficiently. At 480 °C, the aluminum matrix in the composite material is more compact, and the HEAs particles in the composite material are more evenly distributed, and the interface between HEAs particles and aluminum matrix is smooth. At 500 °C, the intensity of HEAs diffraction peak in the composite material changes significantly. At 520 °C, AlNi solid solution phase with BCC structure appears in the HEAs region, and the HEAs structure changes from FCC to FCC + BCC, and Al5Cr8, Al5Co2 and Al2Cu phases precipitate. At 480 °C, the nanohardness and elastic modulus at the interface reaches 1245.31 MPa and 72.45 GPa, respectively, showing relatively excellent interfacial bonding strength. The elastic modulus of both HEAs reinforcement and aluminum matrix decrease at a sintering temperature above 480 °C, and the composites have hard and brittle characteristics. At 480 °C, the macroscopic compression and yield strengths of composites are ~ 421.2 MPa and ~ 289.5 MPa, and the maximum shrinkage rate is ~65.3%, exhibiting excellent strength and toughness.

Pressureless Sintering Kinetics of NiFe2O4 Ceramic Fabricated by Slip Casting

In this work, a systematic research is carried out to investigate the sintering kinetics of NiFe2O4 ceramic obtained by slip casting and pressureless sintering. The sintering shrinkage behaviors showed the linear shrinkage and linear shrinkage rate of the green body in the axial and radial directions, both increased with increasing sintering temperature, though the maximum linear shrinkage rate in the radial direction was acquired at a lower temperature (1280.7°C) than that in the axial direction (1305.4°C) for a denser compact. The temperature related to the maximum densification rate was about 1316.5°C while the relative density was around 72%. The characteristic sintering kinetics window exhibited that the sintering process could be typically divided into three stages. The sintering activation energy of the initial stage was 268.34 kJ mol−1, and the initial stage of the sintering process was controlled by both grain boundary diffusion and volume diffusion mechanisms. The grain growth kinetic analysis illustrated the grain growth exponent (n) reduced from 2.959 to 2.169 when the sintering temperature increased from 1300 to 1375°C, while the activation energy for grain growth decreased with both the increasing of sintering temperature and the shortening of holding time. It implied that the atomic diffusion process controlled the grain growth. In addition, it was observed that increases in the bending strength and elastic modulus reached its maximum value of 70.36 ± 1.03 MPa and 3.44 ± 0.53 GPa, respectively, mainly associated with the relatively dense microstructure.