Linear Rate Research Articles

Purification of his-tagged proteins using printed monolith adsorption columns

Bio-separation is a crucial process in biotechnology and biochemical engineering for separating biological macromolecules, and the field has long relied on bead-based and expanded bed chromatography. Printed monolith adsorption (PMA) is a new alternative to which uses a 3D-printed monolithic structure containing self-supporting, ordered flow channels. PMA allows for direct purification of biological molecules from crude cell lysates and cell cultures, and like the other technologies, can functionalized to specifically target a molecule and enable affinity chromatography. Here we have combined PMA technology with an immobilized metal affinity ligand (iminodiacetic acid) to provide selectivity of binding to polyhistidine-tagged proteins during PMA chromatography. Two different PMA structures were created and tested for both static and dynamic protein-binding capacity. At comparative linear flow rates, the dynamic binding capacity of both columns was ≈3 mg/mL, while static capacity was shown to differentiate based on column voidage. We show that a polyhistidine-tagged protein can be directly purified from crude lysate with comparable results to the available commercial providers of IMAC, and with a substantially reduced purification time.

Transforming learning opportunities in linguistically diverse secondary classrooms through promoting discussions: results of an intervention

ABSTRACT This article presents results from a design experiment intended to develop students’ understanding of linear functions and rates of change in a linguistically diverse ninth grade classroom. The intervention focused on fostering classroom discussions. Students’ pre-post assessment gains were higher in the redesigned classrooms than in the pre-intervention classrooms. Additionally, multilingual students who were classified as English Learners (ELs) made larger gains than their non-EL peers, and the majority of student learning gains occurred on conceptually-focused items. Analysis of classroom talk showed an increase in high demand moves from the teacher and an increase in the level of teacher responsiveness to students’ mathematical ideas. We discuss implications for future research and design efforts to enhance student learning in multilingual mathematics classrooms.

Research on methods for controlling strand sag in main cables

The accuracy of main cable construction in suspension bridges is directly influenced by the sag of the strands during the erection process. Thus, effective methods for controlling strand sag are crucial. However, the current control standards and methods are primarily based on practical engineering experience, lacking quantitative analysis and a sufficient basis. This paper aims to address this gap by summarizing four commonly used strand sag control methods and proposing a quantitative analysis model that considers the influence of random factors. The model quantifies the impact of these methods on the main cable shape and strand tension after cable tightening. To illustrate the practical application, a suspension bridge is utilized as a case study. The results of the study illustrate a linear relationship between the main cable sag and inter-strand distance, with each control method exhibiting a varying linear change rate. Moreover, the discrepancy in strand distance contributes to uneven strand tension after cable tightening. Random errors contribute to the dispersion of the main cable sag and strand tension, which are further exacerbated by cumulative errors between layers of general strands. Based on the study’s results, this paper provides valuable references for the erection and control of the main cable in suspension bridges.

Ablation resistance of core-shell ZrC1-xOx@ZrO2/Y2O3/SiC coating in 2700 K oxidizing environment coupled with supersonic gas-solid two-phase flow

Existing methods to improve anti-ablation materials for solid-scramjet combustor involve expensive elements, numerous solvents, or complex processes. Through a simple pre-oxidation and a combined coating process, this work developed a core-shell ZrC1-xOx@ZrO2/Y2O3/SiC coating of asphalt-concrete-like structure, achieving a linear (mass) ablation rate 52 % (57 %) lower than that of C/C-ZrC-SiC composite under simulated test conditions. Underlying protection mechanism was revealed by first-principle calculations. Core-shell ZrC1-xOx@ZrO2 could retard oxidation and reserve solid ZrC1-xOx instead of ZrO2 to resist scouring at high temperature. The formation of self-sealing Y4Si3O12 alleviated the active oxidation of SiC. Finally, newly-formed asphaltic-concrete-like ZrC1-xOx/ZrO2/Y4Si3O12 contributed to enhanced ablation resistance.

Research on spatial corrosion behavior and durability protection technology of concrete box girder bridge in cold regions

In order to study the corrosion behavior of concrete box girder in deicing salt environment, a series scaled model of concrete box girders were made to study the deterioration mode of concrete box girder under load, chloride corrosion, freeze-thaw cycle and their combined action. Combined with silane impregnation, the durability protection technology of concrete box girder bridges in cold regions was proposed. The experimental results show that under freezing-thawing action, the top plate of the box girder has the most serious deterioration, and the performance of the web is better. The surface erosion of the top plate is 65.38 % and 80.77 % different from that of the bottom plate and web plate, respectively. The freezing-thawing erosion of the concrete box girder has a significant spatial multi-dimension. The chloride ion erosion law of the top plate and bottom plate of concrete box girder is similar to the distribution law of shear lag effect under load. The inhibition effect of compressive stress on chloride ion is 9.67 %, and the overall inhibition effect is not large. The maximum difference of chloride ion concentration at each measuring point on the bottom plate is 30.14 %. Silane can be used as a protective coating for concrete bridges in cold areas, and the coating thickness of 2 mm can meet the requirements of anti-freezing. With the increase of freeze-thaw time, the silane protection ability began to decline. The maximum silane protection effect of 0–1 cm from the surface at 90d and 180d decreased by 40.8 % and 71.7 %, respectively. After the silane coating was applied, the chloride ion erosion rate of the bottom plate still showed a faster trend. When the freeze-thaw cycle exceeded 30 times, the silane protection ability decreased almost at a linear rate with the freeze-thaw time. Regardless of whether the silane coating protection technology is adopted, the chloride ion concentration of the bottom plate of concrete box girders is at least 10 % more than that of the top plate for freeze-thawing 90d and 180d, and the maximum can reach 32.1 %. The deterioration behavior of concrete box girders in cold regions has significant spatial multi-dimension. The existing single-parameter durability design methods, which mainly focus on solid section, are no longer suitable for box girder structures.

Effects of Zr/Ti ratios on the structure and ablation characteristics of (Zr,Ti)C–SiC composites

Dense (Zr,Ti)C–SiC composites containing a dual-phase solid solution were fabricated by spark plasma sintering using homemade Mg-modified multiphase ceramic powders as raw materials. The ablation behaviour suggested that the composite with a molar ratio of Zr/Ti = 3:1 exhibited the best ablation resistance, with low mass and linear ablation rates of −2.56 ± 0.89 mg/s and 1.26 ± 0.40 μm/s, respectively, after ablation for 90 s under a plasma flame test at around 2300 °C. It is asserted that the formation of an oxide film consisting of a self-sintered ZrO2 skeleton and a high-viscosity Ti–Mg–Si–O liquid phase was responsible for the excellent ablation resistance, which has remarkable efficacy in resisting the scouring effect of ablative flames and the erosion induced by oxidizing gases on the composite matrix.

Joint sparse optimization: lower-order regularization method and application in cell fate conversion

Multiple measurement signals are commonly collected in practical applications, and joint sparse optimization adopts the synchronous effect within multiple measurement signals to improve model analysis and sparse recovery capability. In this paper, we investigate the joint sparse optimization problem via ℓp,q regularization ( 0⩽q⩽1⩽p ) in three aspects: theory, algorithm and application. In the theoretical aspect, we introduce a weak notion of joint restricted Frobenius norm condition associated with the ℓp,q regularization, and apply it to establish an oracle property and a recovery bound for the ℓp,q regularization of joint sparse optimization problem. In the algorithmic aspect, we apply the well-known proximal gradient algorithm to solve the ℓp,q regularization problems, provide analytical formulas for proximal subproblems of certain specific ℓp,q regularizations, and establish the global convergence and linear convergence rate of the proximal gradient algorithm under some mild conditions. More importantly, we propose two types of proximal gradient algorithms with the truncation technique and the continuation technique, respectively, and establish their convergence to the ground true joint sparse solution within a tolerance relevant to the noise level and the recovery bound under the assumption of restricted isometry property. In the aspect of application, we develop a novel method, based on joint sparse optimization with lower-order regularization and proximal gradient algorithm, to infer the master transcription factors for cell fate conversion, which is a powerful tool in developmental biology and regenerative medicine. Numerical results indicate that the novel method facilitates fast identification of master transcription factors, give raise to the possibility of higher successful conversion rate and in the hope of reducing biological experimental cost.

Polydimethylsiloxane enabled triple-action water-resistant coating with desirable relaxation rate in clear aligner

Clear aligners undergo rapid stress relaxation in warm, moist oral environments, compromising therapeutic effectiveness and longevity of treatment. To develop an innovative multilayer composite material with improved stability and reduced stress release, we have engineered an innovative coating characterized by the surface aggregation of polydimethylsiloxane (PDMS), which imparts a pronounced hydrophobic effect. In addition, the chemically and physically cross-linked structure of the coating reduces the free volume created by molecular chain rearrangement owing to the presence of water molecules, thereby minimizing water penetration into the coating. Concurrently, the coating’s internal structure is enriched with numerous polar functional groups to capture water molecules that penetrate into the inside of the coating. Through combination of these mechanisms, water molecules are effectively sequestered, thereby impeding their penetration into the polyethylene terephthalate glycol (PETG) substrate. The impact of the polydimethylsiloxane content on the triple-action water-resistance mechanisms was thoroughly examined using attenuated total reflection (ATR)-Fourier transform infrared (FTIR), water absorption rate, water swelling rate, and X-ray photoelectron spectroscopy. The low surface energy cross-linked polyurethane coating is applied to the polyethylene terephthalate glycol (PETG) substrate to create a novel composite material with specific mechanical properties and reduced stress relaxation. The composite material remains stable in simulated oral environment with linear swelling rate of 0.58 % upon water absorption. Additionally, the stress release rate of the composite material within 336 h is notably lower (23.64 %) than that of PETG (62.29 %).

Construction of gradient structure C/C–ZrC–SiC composites with good ablation resistance

With the upgrade of aircraft and the increasingly harsh service environment, it is urgent to develop high-performance thermal structural materials. In this study, inspired by foliar and root water uptake of trees, we propose a one-step facile method to achieve an autonomous gradient in C/C–ZrC–SiC sharp leading edge composites. The gradual increase of SiC content from top to bottom is beneficial to improve the heat transfer capacity of the composites. After oxyacetylene ablation for 60 s, the mass and linear ablation rates of the samples with gradient structure are 0.83 mg/s and 0.5 μm/s, 35 % and 83 % lower than conventional samples. The composites with gradient structure of ZrC and SiC are favorable to the formation of a compact and smooth ZrO2 oxide protective layer, which not only protects the composites from further penetration of O2, but also resists the mechanical denudation. The novel gradient structure composites with enhanced ablation resistance show a bright application prospect in next-generation thermal protection systems.

Geochemical indices and sedimentation rates in the Pardo River basin, São Paulo state, Brazil

Sediment geochemical indices and sedimentation rates data from the Pardo River watershed, São Paulo State, Brazil, provide relevant reference guidelines for stakeholders to plan future actions aiming to achieve the appropriate management of that hydrographic basin. The watershed includes 20 municipalities where about 650,000 inhabitants are living and whose waters after withdrawal and treatment supply ∼300,000 people in that region. Six sediment cores provided the geochemical and radiometric dataset, which was obtained from sampling sites located in the following cities: Ourinhos, Santa Cruz do Rio Pardo, Águas de Santa Bárbara, Avaré, Botucatu, and Pardinho. The concentration data for some metals were compared with the reference values established by the Brazilian environmental legislation for sediment dredging because currently there is a lack of specific quality guidelines for marine or fluvial sediment in Brazil. Also, the entire dataset was used in the calculation of two traditional geochemical indices, i.e., the enrichment factor (EF) and contamination factor (CF). In some cores, both indices provided insight revealing possible anthropogenic inputs of magnesium oxide (MgO), potassium oxide (K2O), sulfur trioxide (SO3), vanadium oxide (V2O5), copper (II) oxide (CuO), and other constituents due to development of activities related to the crop production. The constant rate of supply (CRS) of the unsupported/excess lead 210 (210Pb) model has been successfully applied to the obtained a radiometric 210Pb dataset, yielding mean values of the mass accumulation rate (MAR) between 0.86 and 7.23 g/(cm2·y) and linear sedimentation rates (LSR) ranging from 2.9 to 7.1 cm/y. Both of these rates exhibited a significant correlation, representing physical weathering processes occurring in the basin. Chemical weathering rates reported in the literature indicate values much lower than the physical weathering rates and such findings have also been confirmed in the current study when the obtained data were compared with results from previous investigations in the Pardo River watershed. The CRS 210Pb chronological model was useful to track historical changes in the MgO and CuO concentration in the sediment cores, allowing curves to be plotted exhibiting major peaks in core 1 (1980–2010) and core 3 (2000–2010), a continuous increase from 1970 onwards until 2010 (core 4), and a sharp increase at the end of the monitoring period, 2017 (cores 5 and 6). Data available for the harvested area at a municipality located within the basin for the period 1990–2022 have indicated a more pronounced increase over the last years in the production of sugar cane, soybeans, and oranges, implying an increasing use of fertilizers and agricultural correctives for crop production, whose chemical composition would justify the trends observed for MgO and CuO concentrations in the sediment cores. The current study also revealed a wide range of significant relations involving the concentration of ferric oxide (Fe2O3) and other analyzed constituents, with iron tending to accumulate in the finer grain sizes (from 0.125 to <0.037 mm) of the sediment. The CRS 210Pb chronological model permitted evaluation of the history of the iron flux up to the present, which could represent baseline guidance levels for indicating future anthropic inputs in the basin.

Decay rate of discrete-time homogeneous delayed systems with cone invariance

This paper is dedicated to analysing the decay rate of discrete-time homogeneous delayed systems that exhibit order preservation within a proper cone. First, a sufficient criterion ensuring the cone invariance of the system is introduced. By exploring the monotonicity of system trajectories, a condition that is both sufficient and necessary for guaranteeing the asymptotic stability of the system is presented. Importantly, under a weak assumption for the growth rate of time-varying delays, a universal framework is provided for characterising the decay rate of the system. Furthermore, typical examples of decay rate analysis are presented when delays are bounded or experience linear, sublinear, or logarithmic growth rates. Eventually, the rationality of the results is illustrated through a numerical simulation.

A novel probabilistic model: Simulation and modeling the time duration in musical education and engineering

Statistical analysis of the time-to-event scenarios commonly involves the use of the exponential and Rayleigh distributions. However, the exponential distribution is constrained by its constant failure rate, while the Rayleigh distribution exhibits a growing (or increasing) failure rate. The linear failure rate distribution provides a broader perspective by encompassing both of these distributions, including the possibility of a non-increasing hazard function. In this paper, a new distribution is introduced, which could be considered as one of the major modifications to the linear failure rate distribution, known as the weighted linear failure rate distribution. The model proposed illustrates both monotonic and a known non-monotonic failure rate. This paper extensively explores the characteristics of the proposed distribution. It presents the maximum likelihood estimates for the unknown parameters and includes a simulation study. The analysis focuses on three real data sets obtained from the fields of musical education and engineering. By employing three decisive tools, it is observed that the current distribution provides a superior fit in comparison to several other widely recognized distributions.

Study on mullitization of sillimanite group minerals and its effect on properties of the Al2O3‐SiC‐C gunning material

AbstractThis study aimed to compare and summarize the mullitization mechanism of the sillimanite group minerals and investigated its effect on the mechanical properties of Al2O3‐SiC‐C gunning materials. By comparing the phase composition and microstructure of kyanite, andalusite, and sillimanite at different temperatures, the mullitization mechanism of sillimanite group minerals was clarified. Furthermore, the Al2O3‐SiC‐C gunning materials with sillimanite group minerals addition were prepared by bauxite and fused brown corundum as aggregates, fused white corundum (≤0.045 mm), SiC (≤0.075 mm), α‐Al2O3 (≤10 µm), pitch sphere, SiO2 micropowder (≤2 µm) as a matrix, and silica sol as a binder. Then, the effect of the addition of sillimanite group minerals on the mechanical properties of Al2O3‐SiC‐C gunning materials was characterized. The results indicate that kyanite requires the lowest temperature for mullitization compared to andalusite and sillimanite. The mullitization process involves the migration of Al3+ and Si4+, resulting in a decrease in the lattice constant of sillimanite group minerals followed by the production of mullite and SiO2. Incorporating sillimanite group minerals into Al2O3‐SiC‐C gunning materials effectively controls their linear change rate after firing while enhancing their mechanical properties. Notably, the addition of kyanite yields superior performance in Al2O3‐SiC‐C gunning materials.

The stability and morphology of laminar premixed hydrogen/air flames under various gravity conditions

In the present work, direct numerical simulations (DNS) were employed to understand the stability and morphology of laminar lean premixed hydrogen/air flames under various gravity conditions. The combined effect of Darrieus–Landau (DL) instability, thermal-diffusive (TD) instability and Rayleigh–Taylor (RT) instability was studied quantitatively for both the initial linear regime and the long-term nonlinear regime, with a particular focus on the effect of RT instability. In the linear regime, it was found that the RT instability has a negligible effect on the linear growth rate of flames with an equivalence ratio of 0.4, but the effect is significant when the equivalence ratio decreases to 0.3. The performance of various models for the dispersion relation was discussed, including a theoretical model considering the effects of all instabilities, which captures well the trend of the simulated results in the cases with unity Lewis numbers. The hydrogen/air flames with an equivalence ratio of 0.3 was investigated comprehensively in the nonlinear regime. For the cases with unity Lewis numbers, the RT-unstable flame exhibits a similar single-cusp structure as the RT-neutral flame, but with a deeper cusp and larger consumption speed as a result of the destabilizing effect of RT instability. The RT-stable flame gradually returns to a planar flame shape owing to the stabilizing effect of RT instability. For the cases with non-unity Lewis numbers, the effect of domain size on the flame evolution was investigated, showing a domain width of 200δT is enough to obtain a domain-independent result, where δT is the laminar flame thickness. It was found that the cases initialized with multimode perturbations reach the quasi-steady state faster, while the flame statistics are consistent with those of the cases initialized with single mode perturbations. The effect of RT instability was explored by comparing the results from various gravity conditions. The flame consumption speed is the largest in RT-unstable flames, and the smallest in RT-stable flames. The variation in flame consumption speed is due to the difference in the flame surface area, while the local reactivity and flame structure are not influenced by the RT instability. Further fractal analysis reveals that although the RT instability causes significant differences in flame surface area, the characteristic fractal dimension remains constant for flames under different gravity conditions.Novelty and significanceIn the present work, direct numerical simulations were employed to understand the stability and morphology of RT-unstable, RT-neutral and RT-stable laminar lean premixed hydrogen/air flames. For the first time, the effect of DL, TD and RT instabilities was quantitatively examined for both the linear regime and the nonlinear regime. A theoretical model considering various instabilities was compared with the simulated dispersion relations in the linear regime. In the non-linear regime, the flame surface area and corresponding flame consumption speed are influenced by the RT instability, while the flame stretch factor remains unaffected. A fractal analysis was conducted in laminar premixed hydrogen/air flames under the influence of various instabilities. Remarkably, it was discovered that the characteristic fractal dimension remains constant for the cases with and without the RT instability.

Simulation of triggering and evolution of ELM by pellet injection in EAST under BOUT++ framework

A BOUT ++ three-field magnetohydrodynamic model is employed to study the triggering and evolution of edge localized mode (ELM) by Li pellets injected along the outer mid-plane in the EAST configuration. The linear simulation shows that compared with a large deposition on the pedestal top (scenario I), a smaller deposition within the steep-gradient pedestal region (scenario II) can stimulate much larger linear growth rates of all-n peeling-ballooning modes (PBMs). The nonlinear simulation shows that there exists a pellet size threshold for ELM triggering for two deposition locations; the threshold for scenario I predicted in the present study matches the EAST observation well. Comparison of the two scenarios reveals that a smaller deposition is sufficient to trigger an ELM in a much shorter time in scenario II, whose ELM size is comparable to that in scenario I. This conclusion confirms previous DIII-D and ASDEX-Upgrade observations, suggesting that the steep-gradient pedestal region is a favorable deposition location for ELM triggering with minimum pellet size. Simulation analyses also find that the positive radial gradient of the hump-like pressure profile in the outer mid-plane induced by the pellet deposition plays a different role in the two scenarios. In scenario I, the force resulting from the gradient hinders the outflow of core plasmas and in return, the perturbation is suppressed from spreading inwards after ELM crashes. In scenario II, with a sizable deposition, the gradient results in another competitive perturbation growth region during the linear phase, thus dispersing the free energy and reducing the efficiency of destabilizing PBMs by pellet injection. The suppressing effect of saturated zonal flow on other modes, the short ELM fast crash phase, and the restricting transport effect of the positive radial pressure gradient work together to constrain the pedestal energy loss, especially when the pellet deposition amount is high.

Quantitative asymptotic regularity of the VAM iteration with error terms for $m$-accretive operators in Banach spaces

In this paper, we obtain, by using proof mining methods, quantitative results on the asymptotic regularity of the viscosity approximation method (VAM) with error terms for m -accretive operators in Banach spaces. For concrete instances of the parameter sequences, linear rates are computed by applying a lemma due to Sabach and Shtern.

Linear convergence of event‐triggered distributed optimization with metric subregularity condition

AbstractThis paper designs a continuous‐time algorithm with event‐triggered communication (ETC) for solving a class of distributed convex optimization problems with a metric subregularity condition. First, we develop an event‐triggered continuous‐time optimization algorithm to overcome the bandwidth limitation of multi‐agent systems. Besides, with the aid of Lyapunov theory, we prove that the distributed event‐triggered algorithm converges to the optimum set with an exact linear convergence rate, without the strongly convex condition. Moreover, we provide the discrete version of the continuous‐time algorithm and show its exact linear convergence rate. Finally, we give a comparison example to validate the effectiveness of the designed algorithm in communication resource saving.

Satellite gravimetry observations on the state of groundwater level variability in the Arabian Peninsula Region and the associated socio-economic sustainability challenges

Groundwater is an important resource for the Arabian Peninsula Region. The population increase, rise in agricultural activities, and Gulf Cooperation Council (GCC) countries (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates) inclination towards economic diversification and tourism promotion have heightened the freshwater demand. As a result of climate change and varying weather patterns, the situation has become more complicated. Due to arid conditions, recharge is mostly less than withdrawal which consequently results in underground water level decline over time. In the research, we have used Gravity Recovery and Climate Experiment (GRACE/GRACE-FO) MASCON solutions, Global Land Data Assimilation System (GLDAS) soil moisture, and the Integrated Multi-satellite Retrievals for Global Precipitation Mission (IMERG) rainfall data to observe the Equivalent Water Thickness (EWT), and rainfall patterns in this region for the past two decades (2002–2023). The results indicate that in Saudi Arabia the water level is declining nearly at a linear rate and the linear regression model fits well with the data (R2 value, the coefficient of determination, for different cities of Saudi Arabia is ≥ 0.94). In the Al Jouf Area, the water decline is the highest at −1.69 cm/year which is 43% greater than the previous calculations. The lowest decline rate is in Sanaa (Yemen) which is −0.13 cm/year. Furthermore, all the other studied locations show a groundwater declining trend. In Saudi Arabia's Makkah, Madina, Riyadh, and Damam the reduction rate is −0.36, −0.48, −0.72, and −0.48 (cm/year) respectively. Kuwait, UAE's Dubai, and Al Ain show a similar groundwater reduction rate of −0.19 cm/year. In Oman's Masqat, the groundwater decline rate is −0.22 cm/year. Also, in the recent data, one can see the higher seasonal amplitudes that are indicative of greater fluctuations in EWT data in recent times. If water mining continues at the same pace, this important resource can become a rare commodity. Limited water supply can likely become a limiting factor for further social, agricultural, and industrial development. That's why major reviews and shifts are necessary in the current policies related to water resource management and conservation.

More than Steepness: Introducing Slope Quantitatively with Interactive Dynamic Representations

We report on a long-term collaboration with ninth-grade mathematics teachers at a linguistically diverse high school in which we examined the intersection between mathematics and language, and how language and mathematical thinking can be developed together in a multilingual setting. We co-designed lessons that promoted conceptual understanding, increased students’ access to grade level mathematics and created opportunities for students who are classified as English learners to participate in discussions. Our content focus was linear and exponential rates of change. In this article, we focus on linear rate of change and its connection to slope. After identifying three distinct meanings for and uses of slope in a ninth-grade mathematics textbook: (a) slope as steepness, (b) slope as rate of change, and (c) slope as a property of collinearity (presented in this order) and observing student interactions around slope concepts, we considered whether it may be more beneficial for students, particularly emergent multilingual students, to develop a robust quantitative understanding of slope first, then introduce the other two meanings of slope as an application of rate of change. To achieve this, we created a series of lessons incorporating dynamic interactive technology and mathematical language routines. We share three of these lessons in this article and include a classroom vignette illustrating the classroom interactions that were achieved through using our first Desmos activity.

Enhancing Ablation Resistance of TaB2-Based Ultra-High Temperature Ceramics by Mixing Fine TaC Particles and Dispersed Multi-Walled Carbon Nanotubes.

Ultra-high temperature ceramics (UHTCs) have been widely applied in many fields. In order to enhance the comprehensive properties of TaB2-based UHTCs, the first collaborative use of fine TaC particles and dispersed multi-walled carbon nanotubes (MWCNTs) was employed via spark plasma sintering (SPS) at 1700 °C. The derived UHTCs exhibited an average grain size of 1.3 μm, a relative density of 98.6%, an elastic modulus of 386.3 GPa, and a nano hardness of 21.7 GPa, leading to a greatly improved oxidation resistance with a lower linear ablation rate at -3.3 × 10-2 μm/s, and a markedly reinforced ablation resistance with mass ablation rate of -1.3 × 10-3 mg/(s·cm2). The enhanced ablation resistance was attributable to the physical pinning effect, sealing effect and self-healing effect. Thus, this study provides a potential strategy for preparation of UHTCs with bettered ablation resistance and physical properties.