Solution‐Processed All‐Ceramic Plasmonic Metamaterials for Efficient Solar–Thermal Conversion over 100–727 °C

Low‐cost and large‐area solar–thermal absorbers with superior spectral selectivity and excellent thermal stability are vital for efficient and large‐scale solar–thermal conversion applications, such as space heating, desalination, ice mitigation, photothermal catalysis, and concentrating solar power. Few state‐of‐the‐art selective absorbers are qualified for both low‐ ( < 200  ° C) and high‐temperature ( > 600  ° C) applications due to insufficient spectral selectivity or thermal stability over a wide temperature range. Here, a high‐performance plasmonic metamaterial selective absorber is developed by facile solution‐based processes via assembling an ultrathin ( ≈ 120 nm) titanium nitride (TiN) nanoparticle film on a TiN mirror. Enabled by the synergetic in‐plane plasmon and out‐of‐plane Fabry–Pérot resonances, the all‐ceramic plasmonic metamaterial simultaneously achieves high, full‐spectrum solar absorption (95%), low mid‐IR emission (3% at 100  ° C), and excellent stability over a temperature range of 100–727  ° C, even outperforming most vacuum‐deposited absorbers at their specific operating temperatures. The competitive performance of the solution‐processed absorber is accompanied by a significant cost reduction compared with vacuum‐deposited absorbers. All these merits render it a cost‐effective, universal solution to offering high efficiency (89–93%) for both low‐ and high‐temperature solar–thermal applications.     

Dual‐Peak Absorbing Semiconducting Copolymer Nanoparticles for First and Second Near‐Infrared Window Photothermal Therapy: A Comparative Study

Near‐infrared (NIR) light is widely used for noninvasive optical diagnosis and phototherapy. However, current research focuses on the first NIR window (NIR‐I, 650–950 nm), while the second NIR window (NIR‐II, 1000–1700 nm) is far less exploited. The development of the first organic photothermal nanoagent (SPN_I‐II) with dual‐peak absorption in both NIR windows and its utilization in photothermal therapy (PTT) are reported herein. Such a nanoagent comprises a semiconducting copolymer with two distinct segments that respectively and identically absorb NIR light at 808 and 1064 nm. With the photothermal conversion efficiency of 43.4% at 1064 nm generally higher than other inorganic nanomaterials, SPN_I‐II enables superior deep‐tissue heating at 1064 nm over that at 808 nm at their respective safety limits. Model deep‐tissue cancer PTT at a tissue depth of 5 mm validates the enhanced antitumor effect of SPN_I‐II when shifting laser irradiation from the NIR‐I to the NIR‐II window. The good biodistribution and facile synthesis of SPN_I‐II also allow it to be doped with an NIR dye for fluorescence‐imaging‐guided NIR‐II PTT through systemic administration. Thus, this study paves the way for the development of new polymeric nanomaterials to advance phototherapy.     

Molecular Targeting‐Mediated Mild‐Temperature Photothermal Therapy with a Smart Albumin‐Based Nanodrug

Photothermal therapy (PTT) usually requires hyperthermia >50 °C for effective tumor ablation, which inevitably induces heating damage to the surrounding normal tissues/organs. Moreover, low tumor retention and high liver accumulation are the two main obstacles that significantly limit the efficacy and safety of many nanomedicines. To solve these problems, a smart albumin‐based tumor microenvironment‐responsive nanoagent is designed via the self‐assembly of human serum albumin (HSA), dc‐IR825 (a cyanine dye and a photothermal agent), and gambogic acid (GA, a heat shock protein 90 (HSP90) inhibitor and an anticancer agent) to realize molecular targeting‐mediated mild‐temperature PTT. The formed HSA/dc‐IR825/GA nanoparticles (NPs) can escape from mitochondria to the cytosol through mitochondrial disruption under near‐infrared (NIR) laser irradiation. Moreover, the GA molecules block the hyperthermia‐induced overexpression of HSP90, achieving the reduced thermoresistance of tumor cells and effective PTT at a mild temperature (<45 °C). Furthermore, HSA/dc‐IR825/GA NPs show pH‐responsive charge reversal, effective tumor accumulation, and negligible liver deposition, ultimately facilitating synergistic mild‐temperature PTT and chemotherapy. Taken together, the NIR‐activated NPs allow the release of molecular drugs more precisely, ablate tumors more effectively, and inhibit cancer metastasis more persistently, which will advance the development of novel mild‐temperature PTT‐based combination strategies.     

Hot deformation behavior and processing maps of iron‐nickel based superalloy

Hot deformation behavior of iron‐nickel based superalloy (multimet N‐155) was investigated by hot compression tests, carried out in the deformation temperature of 850 °C–1150 °C with strain rates of 0.001–0.1 s^?1. The results showed that during the hot deformation of the alloy, under the same temperature, the flow stress rises with the increase of strain rate. At the same strain rate, the flow stress decreases with the increase of the temperature. The constitutive equations of the alloy that describe the flow stress as a function of strain rate and deformation temperature were established and the calculated apparent activation energy was 584.996 Kj/mol. The results of metallographic analysis showed that the amount of dynamic recrystallization in the peak efficiency domain is higher than the other domains. The results also showed that by increase of deformation temperature and/or decrease of strain rate, the volume fraction of dynamic recrystallization increases. Processing maps under different strains were constructed for evaluation of flow instability regime and optimization of processing parameters. The optimum hot working window for alloy was obtained at the temperature range of 925 °C–1050 °C and strain rate of 0.001–0.003 s^?1, with peak efficiency of 28 %.     

Second Near-Infrared Plasmonic Nanomaterials for Photoacoustic Imaging and Photothermal Therapy

Photoacoustic imaging (PAI) and imaging-guided photothermal therapy (PTT) in the second near-infrared window (NIR-II, 1000–1700 nm) have received increasing attention owing to their advantages of greater penetration depth and higher signal-to-noise ratio. Plasmonic nanomaterials with tunable optical properties and strong light absorption provide an alternative to dye molecules, showing great prospects for phototheranostic applications. In this review, the research progress in principally modulating the optical properties of plasmonic nanomaterials, especially affecting parameters such as size, morphology, and surface chemical modification, is introduced. The commonly used plasmonic nanomaterials in the NIR-II window, including noble metals, semiconductors, and heterostructures, are then summarized. In addition, the biomedical applications of these NIR-II plasmonic nanomaterials for PAI and PTT in phototheranostics are highlighted. Finally, the perspectives and challenges for advancing plasmonic nanomaterials for practical use and clinical translation are discussed.     

1D Coordination Polymer Nanofibers for Low‐Temperature Photothermal Therapy

Near‐infrared (NIR)‐light‐triggered photothermal therapy (PTT) usually requires hyperthermia to >50 °C for effective tumor ablation, which can potentially induce inflammatory disease and heating damage of normal organs nearby, while tumor lesions without sufficient heating (e.g., the internal part) may survive after treatment. Achieving effective tumor killing under relatively low temperatures is thus critical toward successful clinical use of PTT. Herein, we design a simple strategy to fabricate poly(ethylene glycol) (PEG)‐modified one‐dimensional nanoscale coordination polymers (1D‐NCPs) with intrinsic biodegradability, large surface area, pH‐responsive behaviors, and versatile theranostic functions. With NCPs consisting of Mn2+/indocyanine green (ICG) as the example, Mn‐ICG@pHis‐PEG display efficient pH‐responsive tumor retention after systemic administration and then load Gambogic acid (GA), a natural inhibitor of heat‐shock protein 90 (Hsp90) that plays an essential role for cells to resist heating‐induced damage. Such Mn‐ICG@pHis‐PEG/GA under a mild NIR‐triggered heating is able to induce effective apoptosis of tumor cells, realizing low‐temperature PTT (~43 °C) with excellent tumor destruction efficacy. This work not only develops a facile approach to fabricate PEGylated 1D‐NCPs with tumor‐specific pH responsiveness and theranostic functionalities, but also presents a unique low‐temperature PTT strategy to kill cancer in a highly effective and minimally invasive manner.     

A Porphyrin‐Based Conjugated Polymer for Highly Efficient In Vitro and In Vivo Photothermal Therapy

Conjugated polymers have been increasingly studied for photothermal therapy (PTT) because of their merits including large absorption coefficient, facile tuning of exciton energy dissipation through nonradiative decay, and good therapeutic efficacy. The high photothermal conversion efficiency (PCE) is the key to realize efficient PTT. Herein, a donor–acceptor (D–A) structured porphyrin‐containing conjugated polymer (PorCP) is reported for efficient PTT in vitro and in vivo. The D–A structure introduces intramolecular charge transfer along the backbone, resulting in redshifted Q band, broadened absorption, and increased extinction coefficient as compared to the state‐of‐art porphyrin‐based photothermal reagent. Through nanoencapsulation, the dense packing of a large number of PorCP molecules in a single nanoparticle (NP) leads to favorable nonradiative decay, good photostability, and high extinction coefficient of 4.23 × 10⁴m ^?1 cm^?1 at 800 nm based on porphyrin molar concentration and the highest PCE of 63.8% among conjugated polymer NPs. With the aid of coloaded fluorescent conjugated polymer, the cellular uptake and distribution of the PorCP in vitro can be clearly visualized, which also shows effective photothermal tumor ablation in vitro and in vivo. This research indicates a new design route of conjugated polymer‐based photothermal therapeutic materials for potential personalized theranostic nanomedicine.     

Effect of prior austenite on reversed austenite stability and mechanical properties of low carbon medium manganese steel heavy plate

The effect of prior austenite on reversed austenite stability and mechanical properties of Fe‐0.06C‐0.2Si‐5.5Mn‐0.4Cr (wt.%) annealed steels was elucidated. With the decrease of austenitizing temperature from 1250 °C to 980 °C, the prior austenite changed from complete recrystallization to partial recrystallization, and the average austenite size was reduced. The volume fraction of reversed austenite was increased from 26.32 % to 30.25 % because of high density of grain boundaries and dislocations. The martensite transformation temperature of annealed steels was increased from ～115 °C to ～150 °C, and both of thermal and mechanical stability of reversed were reduced. There was no significant different in tensile properties, however, the impact toughness was enhanced from 100 J to 180 J at ?60 °C. The excellent impact toughness in annealed steel (austenitized at 980 °C) was obtained because of higher density of high misorientation grain boundaries, more volume fraction of reversed austenite and reduced segregation at grain boundaries.     

Early age electrical resistivity behaviour of various concrete mixtures subject to low temperature cycling

The effect of thermal cycling between −24 and + 24 °C on the electrical resistivity of five concrete mixtures was investigated at early-ages. Each mixture was subjected to two thermal cycles (initiated either 1 or 14 days after casting) wherein temperatures were changed by 1 °C/h. Electrical resistivity increased as temperature decreased. This relationship followed the Arrhenius equation until the phase transition temperature (i.e. initial freezing of the pore solution), at which point electrical resistivity increased greatly. A method of determining the phase transition temperature is presented that could be used in place of existing methods using mortar cubes. The phase transition temperature was higher during thawing cycles compared to freezing cycles for all mixtures. Mixtures with ground slag replacing cement had higher resistivity and lower phase transition temperatures than mixtures using only cement due to the change in the ionic combination of the concrete pore solution. The phase transition temperature decreases as concrete ages.     

Polyaniline Nanovesicles for Photoacoustic Imaging‐Guided Photothermal‐Chemo Synergistic Therapy in the Second Near‐Infrared Window

Photoacoustic imaging‐guided photothermal therapy in the second near‐infrared (NIR‐II) window shows promise for clinical deep‐penetrating tumor phototheranostics. However, ideal photothermal agents in the NIR‐II window are still rare. Here, the emeraldine salt of polyaniline (PANI‐ES), especially synthesized by a one‐pot enzymatic reaction on sodium bis(2‐ethylhexyl) sulfosuccinate (AOT) vesicle surface (PANI‐ES@AOT, λ_max ≈ 1000 nm), exhibits excellent dispersion in physiological environment and remarkable photothermal ability at pH 6.5 (photothermal conversion efficiency of 43.9%). As a consequence of the enhanced permeability and retention effect of tumors and the doping‐induced photothermal effect of PANI‐ES@AOT, this pH‐sensitive NIR‐II photothermal agent allows tumor acidity phototheranostics with minimized pseudosignal readout and subdued normal tissue damage. Moreover, the enhanced fluidity of vesicle membrane triggered by heating is beneficial for drug release and allows precise synergistic therapy for an improved therapeutic effect. This study highlights the potential of template‐oriented (or interface‐confined) enzymatic polymerization reactions for the construction of conjugated polymers with desired biomedical applications.     

Characterization and stability analysis of oil‐based copper oxide nanofluids for medium temperature solar collectors

Thermal oils are widely used as heat transfer fluids in medium temperature applications. Addition of small amounts of nanoparticles in such fluids can significantly improve their thermophysical properties. This paper presents experimental investigation of an oil‐based nanofluids prepared by dispersing different concentrations (0.25 wt%–1.0 wt%) of copper oxide nanoparticles in Therminol‐55 oil using two‐step method. Shear mixing and ultrasonication were used for uniform distribution and de‐agglomeration of nanoparticles to enhance the stability of the suspensions. The effect of nanoparticles concentrations on thermophysical properties of the nanofluids was analysed by measuring thermal conductivity, dynamic viscosity, effective density and specific heat capacity at different temperatures (25 °C–130 °C). Thermal conductivity exhibited increasing trend with rising temperature and increase in nanoparticles loading. A significant decrease in dynamic viscosity and effective density against increasing temperature makes it suitable for medium temperature applications. Nano‐oils with improved thermal properties are expected to increase the efficiency of concentrating solar thermal collectors.     

Thermal shock behavior of nano-sized SiC particulate reinforced AlON composites

Aluminum oxynitride (AlON) has been considered as a potential ceramic material for high-performance structural and advanced refractory applications. Thermal shock resistance is a major concern and an important performance index of high-temperature ceramics. While silicon carbide (SiC) particles have been proven to improve mechanical properties of AlON ceramic, the high-temperature thermal shock behavior was unknown. The aim of this investigation was to identify the thermal shock resistance and underlying mechanisms of AlON ceramic and 8 wt% SiC–AlON composites over a temperature range between 175 °C and 275 °C. The residual strength and Young's modulus after thermal shock decreased with increasing quenching temperature and thermal shock times due to large temperature gradients and thermal stresses caused by abrupt water-quenching. A linear relationship between the residual strength and thermal shock times was observed in both pure AlON and SiC–AlON composites. The addition of nano-sized SiC particles increased both residual strength and critical temperature from 200 °C in the monolithic AlON to 225 °C in the SiC–AlON composites due to the toughening effect, the lower coefficient of thermal expansion and higher thermal conductivity of SiC. The enhancement of the thermal shock resistance in the SiC–AlON composites was directly related to the change of fracture mode from intergranular cracking along with cleavage-type fracture in the AlON to a rougher fracture surface with ridge-like characteristics, crack deflection, and crack branching in the SiC–AlON composites.     

Experimental and numerical research on high‐temperature thermal insulation performance of lightweight porous ceramic/nanomaterial composite structure

The thermal protection structure of hypersonic vehicles must meet the design requirements of high efficiency and light weight, and its heating surface must also be able to withstand thermal erosion by high‐speed and high‐temperature airflow. In this paper, a light‐weight porous ceramic material and a lightweight nanoscale thermal insulation material with excellent thermal insulation performance are combined to form an integrated thermal protection structure. Experimental study and numerical simulation of the structure's high‐temperature thermal insulation performance are carried out. The experimental results show that a composite sheet made from a 20 mm‐thick lightweight porous ceramic material and a 10 mm‐thick nanomaterial exhibit a temperature drop of 85 % between its back surface and front surface in four thermal environments (1200, 1000, 800 and 600 °C) at 1800 s. This indicates excellent thermal insulation performance of the composite sheet. In addition, the operating temperature limit (<1000 °C) is obtained through high‐temperature thermal performance tests on single‐layer nanomaterial sheets and scanning electron microscopy results. This provides an important basis for determining and optimizing the thickness ratio of the two materials in composite structure.     

Hot workability and deformation mechanisms in Mg/nano–Al2O3 composite

The response of extruded Mg/nano–Al₂O₃ (1 vol.%) composite to hot working in the temperature range 300–500 °C and strain rate range 0.0003–10 s^?1 has been characterized using processing map and kinetic analysis. The hot working window for the composite occurs at strain rates >0.1 s^?1 and the optimum range of temperature is 400–450 °C. In this window, the behavior of the composite is similar to that of the matrix and is controlled by the grain boundary self-diffusion. At lower strain rates, however, the composite exhibits much higher apparent activation energy than that for lattice self-diffusion unlike the matrix material. The deformed microstructures revealed that the prior particle boundaries decorated by the nano-Al₂O₃ particles, are stable and do not slide, rotate or migrate but kink after compressive deformation and as such contribute to the high temperature strength of the composite.     

Nanoparticle‐Based Platform for Activatable Fluorescence Imaging and Photothermal Ablation of Endometriosis

Endometriosis is a painful disorder where endometrium‐like tissue forms lesions outside of the uterine cavity. Intraoperative identification and removal of these lesions are difficult. This study presents a nanoplatform that concurrently delineates and ablates endometriosis tissues using real‐time near‐infrared (NIR) fluorescence and photothermal therapy (PTT). The nanoplatform consists of a dye, silicon naphthalocyanine (SiNc), capable of both NIR fluorescence imaging and PTT, and a polymeric nanoparticle as a SiNc carrier to endometriosis tissue following systemic administration. To achieve high contrast during fluorescence imaging of endometriotic lesions, nanoparticles are constructed to be non‐fluorescent prior to internalization by endometriosis cells. In vitro studies confirm that these nanoparticles activate the fluorescence signal following internalization in macaque endometrial stromal cells and ablate them by increasing cellular temperature to 53 ^°C upon interaction with NIR light. To demonstrate in vivo efficiency of the nanoparticles, biopsies of endometrium and endometriosis from rhesus macaques are transplanted into immunodeficient mice. Imaging with the intraoperative Fluobeam 800 system reveals that 24 h following intravenous injection, nanoparticles efficiently accumulate in, and demarcate, endometriotic grafts with fluorescence. Finally, the nanoparticles increase the temperature of endometriotic grafts up to 47 °C upon exposure to NIR light, completely eradicating them after a single treatment.     

Effect of environment atmosphere on thermal shock resistance of the ZrB2–SiC–graphite composite

The thermal shock resistance of the ZrB₂–SiC–graphite composite was evaluated by measuring the retention of the flexural strength after the electrical resistance heating to the temperature ranging from 1000 °C up to 2500 °C. The experiment was operated in two different environment atmospheres (pure oxygen and low oxygen partial pressure which mixed O₂ and Ar with 1:9) at total pressure 2000 Pa. The residual strength for the specimen decreased gradually as the temperature increased up to 2200 °C, and it was slightly higher when heated in low oxygen partial pressure environment than in pure oxygen. In contrast to the specimen heated in low oxygen partial pressure environment, the residual strength for the specimen in pure oxygen increased steeply as the temperature increased from 1600 °C up to 1800 °C. The analysis of the SEM observations combined with EDS confirmed that the surface oxidation played a positive role in the thermal shock resistance of the ZrB₂–SiC–graphite composite with different environment atmospheres. The results here pointed out a potential method for charactering the effect of environment atmosphere on thermal shock resistance of the ZrB₂–SiC–graphite composite.     

Cu@Sn@Ag core–shell particles preform for power device packaging under harsh environments

This paper presents a novel die attach material for power device packaging based on transient liquid phase (TLP) bonding. Through two-step electroless plating, the Cu@Sn@Ag particles were prepared, and realize interconnection with Cu Substrates after being compressed into preform. Due to the large specific surface area of the core–shell particles, the reflow time can be reduced to 15 min at a low temperature of 250 °C under a pressure of 3 MPa to form high-remelting-point intermetallic compounds (IMCs), which can withstand a high temperature of at least 475 °C. Due to the protection of the Ag coating, the Cu@Sn@Ag particles exhibited excellent oxidation resistance, and the bonding process can be carried out in the atmosphere. Then, the service reliability of the bondlines was evaluated in harsh environments, such as high temperature and humidity, high temperature storing, and thermal shock. The average resistivity of the bondlines was increased from 4.6?±?1.4 to 8.5?±?3.8 µΩ cm after being stored at high temperature (85 °C) and high humidity (85% RH) environment for 14 days. After storing at 300 °C for 15 days, the porosity of bondline increased from 6.8 to 10.8%, and the average shear strength decreased from 30.5?±?6.3 to 22.3?±?5.6 MPa. After thermal shock between ? 40 and 125 °C for 500 cycles, the bonding rate decreased from 99.9 to 84.2%. Moreover, the short-circuit time of electrochemical migration under 60 V voltage was extended to 145 s. The bondline based on the novel core–shell particles exhibited excellent performance as a die attach material under harsh environments.

     

Indirect determination of martensitic transformation temperature of sintered nickel-free Ti–22Nb–6Zr alloy by low temperature compression test

Nickel-free Ti–22Nb–6Zr alloys were fabricated by conventional powder metallurgy sintering method. X-ray diffractometer (XRD) investigation showed that the as-sintered alloys mainly consisted of β phase, with a few needle-like α phase precipitates. Differential scanning calorimetry (DSC) measurement in the temperature ranging from −70 °C to 400 °C and constant stress thermal cycling test by dynamic mechanical analysis (DMA) were unable to reveal the martensitic start temperature of sintered Ti–22Nb–6Zr alloys. Therefore low temperature compression tests were carried out to evaluate their phase transformation behavior indirectly. There was an obvious drop of both Young’s modulus and recoverable strain at −85 °C ∼ −80 °C in the Young’s modulus-temperature and recoverable strain–temperature curves of sintered Ti–22Nb–6Zr alloys respectively, which was attributed to the occurrence of thermal elastic martensitic transformation at this temperature. At the testing temperature of −85 °C, a superelasticity of as high as 5.9% was achieved in the sintered alloys. The results had revealed that sintered Ti–22Nb–6Zr alloys own a great superelasticity intrinsically and would exhibit a much greater superelasticity at room temperature if their martensitic transformation start temperature (M_s) were closer to room temperature. Along with their noble biocompatibility, sintered nickel free Ti–22Nb–6Zr alloys are thus thought to be potentially competitive biomaterials for biomedical applications.     

Wear and corrosion studies of graphite‐aluminum composite reinforced with micro/nano‐TiB2 via spark plasma sintering

The demand for lightweight materials in the automobile and aerospace industries has led to various researches on graphite and graphite‐aluminum composites. The aim of this study was to investigate the effect of the addition of micron/nano TiB₂ particles on the properties of graphite‐aluminum composite particularly the wear resistance. The powders were sintered at 550 °C and 50 MPa with more attention on the effect of the sintering temperature on densification, microhardness, coefficient of thermal expansion, wear and frictional force. The results show that the addition of nano TiB₂ reduces the densification while improving the hardness of Gr?Al composite with the lowest value being 96.0 % of relative density and the highest microhardness of 43.58 HV 0.1. The coefficient of thermal expansion and frictional force of the composite materials increases with increasing TiB₂ content and heating rate (100 °C/min–150 °C/min). TiB₂ particles enhance the wear resistance of graphite‐aluminum composite. The addition of micro/nanoparticles of TiB₂ to graphite‐aluminum composite increases its corrosion rate with improved passivation behavior in 3.5 wt.% NaCl solution. Nevertheless, 5 wt.% nano (100 °C/min) TiB₂ additions do not affect the overall corrosion rate. This work has shown that we can take advantage of some of the properties of TiB₂ to improve the performance of graphite‐aluminum composite.     

Retention of mechanical performance of polymer matrix composites above the glass transition temperature by vascular cooling

An actively cooled vascular polymer matrix composite containing 3.0% channel volume fraction retains greater than 90% flexural stiffness when exposed continuously to 325 °C environmental temperature. Non-cooled controls suffered complete structural failure through thermal degradation under the same conditions. Glass–epoxy composites (T_g = 152 °C) manufactured by vacuum assisted resin transfer molding contain microchannel networks of two different architectures optimized for thermal and mechanical performance. Microchannels are fabricated by vaporization of poly(lactide) fibers treated with tin(II) oxalate catalyst that are incorporated into the fiber preform prior to resin infiltration. Flexural modulus, material temperature, and heat removal rates are measured during four-point bending testing as a function of environmental temperature and coolant flow rate. Simulations validate experimental measurements and provide insight into the thermal behavior. Vascular specimens with only 1.5% channel volume fraction centered at the neutral bending axis also retained over 80% flexural stiffness at 325 °C environmental temperature.