Recent progress in catalytic dehydrogenation of propane over Pt-based catalysts.

Light alkenes are the key building blocks in the chemical industry. As a propene on-purpose production technology, propane dehydrogenation has drawn particular attention due to the growing demand for propene and the discovery of large reserves of shale gas. The development of highly active and stable propane dehydrogenation catalysts is significant in the world-wide research field. Supported platinum-based catalysts are widely studied for propane dehydrogenation. This article reviews the developments of platinum-based catalysts in propane dehydrogenation, particularly focusing on the influence of the promoter effect and support effect on the structure and catalytic performance and especially on how promoters and supports enable Pt to form highly dispersed and stable active sites. At the end, we propose the prospective research directions of propane dehydrogenation.

Engineering a conformal optical window of a square-to-circular transition isolator.

To realize the flow visualization of shock train structures by Schlieren measurements in a square-to-circular transition isolator, a high-precision conformal optical window was manufactured by fly-cutting technology. According to the light refraction principle, the window's outer surface was iteratively optimized based on the super-elliptic curves of the internal flow channel. Through tolerance analysis and processing parameter optimization, the transmitted wavefront error (RMS value) of the finished window was 0.823λ (λ=632.8n m). Based on a z-type Schlieren apparatus, the high-precision Schlieren measurements were conducted through the window and processed by an image filtering process method. The results promote high-precision Schlieren observation towards square-to-circular transition isolators.

Alkali/alkaline-earth metal-modified MnOx supported on three-dimensionally ordered macroporous-mesoporous TixSi1-xO2 catalysts: Preparation and catalytic performance for soot combustion.

The performance of catalysts used in after-treatment systems is the key factor for the removal of diesel soot, which is an important component of atmospheric fine particle emissions. Herein, three-dimensionally ordered macroporous-mesoporous TixSi1-xO2 (3DOM-m TixSi1-xO2) and its supported MnOx catalysts doped with different alkali/alkaline-earth metals (AMnOx/3DOM-m Ti0.7Si0.3O2 (A: Li, Na, K, Ru, Cs, Mg, Ca, Sr, Ba)) were prepared by mesoporous template (P123)-assisted colloidal crystal template (CCT) and incipient wetness impregnation methods, respectively. Physicochemical characterizations of the catalysts were performed using scanning electron microscopy, X-ray diffraction, N2 adsorption-desorption, H2 temperature-programmed reduction, O2 temperature-programmed desorption, NO temperature-programmed oxidation, and Raman spectroscopy techniques; then, we evaluated their catalytic performances for the removal of diesel soot particles. The results show that the 3DOM-m Ti0.7Si0.3O2 supports exhibited a well-defined 3DOM-m nanostructure, and AMnOx nanoparticles with 10-50 nm were evenly dispersed on the inner walls of the uniform macropores. In addition, the as-prepared catalysts exhibited good catalytic performance for soot combustion. Among the prepared catalysts, CsMnOx/3DOM-m Ti0.7Si0.3O2 had the highest catalytic activity for soot combustion, with T10, T50, and T90 (the temperatures corresponding to soot conversion rates of 10%, 50%, and 90%) values of 285, 355, and 393°C, respectively. The high catalytic activity of the CsMnOx/3DOM-m Ti0.7Si0.3O2 catalysts was attributed to their excellent low-temperature reducibility and homogeneous macroporous-mesoporous structure, as well as to the synergistic effects between Cs and Mn species and between CsMnOx and the Ti0.7Si0.3O2 support.

Dendritic Mesoporous Silica Nanoparticle Supported PtSn Catalysts for Propane Dehydrogenation.

PtSn catalysts were synthesized by incipient-wetness impregnation using a dendritic mesoporous silica nanoparticle support. The catalysts were characterized by XRD, N2 adsorption-desorption, TEM, XPS and Raman, and their catalytic performance for propane dehydrogenation was tested. The influences of Pt/Sn ratios were investigated. Changing the Pt/Sn ratios influences the interaction between Pt and Sn. The catalyst with a Pt/Sn ratio of 1:2 possesses the highest interaction between Pt and Sn. The best catalytic performance was obtained for the Pt1Sn2/DMSN catalyst with an initial propane conversion of 34.9%. The good catalytic performance of this catalyst is ascribed to the small nanoparticle size of PtSn and the favorable chemical state and dispersion degree of Pt and Sn species.

Integrative design and processing of a conformal optical window pair in a cylindrical isolator.

In order to perform the flow visualization of a shock train structure by the schlieren imaging method in the cylindrical isolator, to the best of our knowledge, a novel integrative design and processing scheme of an aluminum alloy pipe with an acrylic conformal optical window pair are proposed. The optical ray tracing and wavefront correction methods were applied to design the inner cylindrical surfaces and outer aspherical cylindrical surfaces of the optical window pair for parallel light correction based on the conjoint analysis with the processing capability. Under the tolerance analysis and the optimization of the machining path, the integrative model was fabricated on a three-axis computer numerical control machine using two-axis turning and fast tool servo machining. The wavefront aberration (peak-to-valley value) and wavefront aberration (RMS) of the optical window pair were corrected within 12.189 and 2.658λ (λ=632.8nm) in the observation area which met the requirements of high-precision schlieren observation.

State-of-the-art progresses for Ti3C2Tx MXene reinforced polymer composites in corrosion and tribology aspects.

Ti3C2Tx MXene, a revolutionary 2D material, has shown bright prospects in various fields, including energy conversion and storage, electronic devices, electromagnetic interference shielding, catalysis, biomedicine etc. The large specific surface area, high electrical conductivity, abundant surface terminations, and the highest stiffness among all solution-processed 2D materials of Ti3C2Tx MXene make it a rising star in polymer composites. Not only have Ti3C2Tx MXene-based polymer composites come into prominence in sensing, energy storage, and photothermal conversion fields as is widely known, but they have also shown great potential in corrosion and tribology fields. Hence, this critical review provides a comprehensive overview of the synthesis strategies, mechanical, and tribological properties of Ti3C2Tx MXene and the recent advances of Ti3C2Tx MXene reinforced polymer composites in corrosion and tribology aspects. The challenges of Ti3C2Tx-based polymer composites faced in corrosion and tribology fields are also summarized. This analysis of Ti3C2Tx-based polymer composites will stimulate a booming field including but not limited to corrosion and tribology, bringing Ti3C2Tx MXene from lab to engineering application.

Comparison Study of Self-Cleaning, Anti-Icing, and Durable Corrosion Resistance of Superhydrophobic and Lubricant-Infused Ultraslippery Surfaces.

Endowing metallic surfaces with special wettability and unique interfacial contacts broadens their wide application fields. Herein, superhydrophobic and lubricant-infused ultraslippery surfaces were achieved through chemical etching, low surface energy molecule grafting, and lubricant infusion. Systematic comparison studies of the surface wettability, self-cleaning, anti-icing, anticorrosion behaviors, and mechanical durability were carried out to reveal the functional differences and mechanisms. Both superhydrophobic and ultraslippery surfaces exhibit a distinct decrease in ice adhesion strength and a remarkable increase in charge-transfer resistance, demonstrating significantly improved ice overdelay and corrosion-resisting performance. Most notably, given the existence of a stable, defect-free, and inert lubricant-infused layer, the lubricant-infused ultraslippery surfaces possess superior mechanical robustness and long-term corrosion resistance, which provides better application potential under challenging service environments.

Amino-functionalized Ti3C2Tx loading ZIF-8 nanocontainer@benzotriazole as multifunctional composite filler towards self-healing epoxy coating.

It is difficult for Ti3C2Tx-containing epoxy coatings to prevent electrochemical corrosion at the metal/coating interface after long-term exposure to corrosive environments. Thus, endowing Ti3C2Tx-containing epoxy coatings with self-healing function and good wear resistance is very significant. Here, a novel self-healing epoxy coating (f-Ti3C2Tx-ZB@EP) is designed via incorporating with amino-functionalized Ti3C2Tx loading 2-methylimidazole zinc salt (ZIF-8) nanocontainer@benzotriazole (f-Ti3C2Tx-ZB) multifunctional composite filler, and its anti-corrosion and tribological properties are evaluated in detail. The as-prepared f-Ti3C2Tx-ZB@EP shows an order of magnitude enhancement in coating resistance (Rc) and achieves self-healing function under severe environment, which are attributed to the synergistic effect of passive and active protection. Specially, the change of pH value caused by electrochemical corrosion could induce the nanocontainer to release BTA, thereby forming corrosion inhibition films on the coating/metal interface. Besides, the wear rate of f-Ti3C2Tx-ZB@EP is decreased by one order of magnitude because of the lubrication effect of Ti3C2Tx at the friction interface and the high resistance to plastic deformation of epoxy composite coating. Therefore, f-Ti3C2Tx-ZB@EP with better self-healing, anti-corrosion and tribological properties is equipped with long-term metal protection ability and enlightens a thought-provoking idea for corrosion and wear resistance.

Understanding the Potential Screening Effect through the Discretely Structured ZnO Nanorods Piezo Array.

The potential screening effect of one-dimensional ZnO nanorods from carriers has been theoretically proved to severely limit its piezoelectricity, but its exact mechanism needs to be further revealed in experiments to guide the design of piezoelectric semiconductors. Here, a discretely structured design was proposed to prevent the free carriers from tunneling among adjacent ZnO nanorods for suppressing the screening effect. Piezoresponse force microscope and finite element analysis were employed in combination to uncover the underlying mechanism in experiment. Further, the output voltage of this discretely structured device was 1.62 times higher than that of the nondesigned device, which clearly authenticates this suppression behavior. Besides, this design prompts an unexpected improvement in flexibility, where the flexural modulus of this piezo-film was reduced by 35.74%. Notably, this work opens a new way to understand the potential screening effect, as expected, and to advance the development of piezo-electronics toward better piezoelectricity and more excellent flexibility.

In Situ Friction-Induced Graphene Originating from Methanol at the Sliding Interface between the WC Self-Mated Tribo-Pair and Its Tribological Performance.

Alcohols are reported to have superlubricity at low loads during sliding; however, their lubricity under high loads has rarely been reported. Meanwhile, the lubrication mechanism of alcohols under high loads is still not well understood. Here, we first report the lubricity of methanol under 98 N and 1450 rpm and demonstrate the formation of graphene and fullerene-like nanostructures induced by tribochemical reactions. Results show that the lubrication mechanism was mainly attributed to the friction-induced graphene under boundary lubrication condition. Besides that, the wear rate of a YG8 hard alloy ball mainly occurred at the run-in processes, and the friction-induced graphene effectively inhibited further wear after the run-in processes. The formation mechanism of graphene was well investigated, and the flash temperature rise and catalyst (WC, WO2, and WO3) were the major causes for the formation of graphene.

Improving the Dynamic Mechanical Properties of XNBR Using ILs/KH550-Functionalized Multilayer Graphene.

Graphene has been considered an ideal nanoscale reinforced phase for preparing high-performance composites, but the poor compatibility and weak interfacial interaction with the matrix have limited its application. Here a highly effective and environmentally friendly method for the functionalization of graphene is proposed through an interaction between as-exfoliated graphene and (3-aminopropyl) triethoxysilane (KH550), in which 1-butylsulfonate-3-methylimidazolium bisulfate (BSO3HMIm)(HSO4) ionic-liquids-modified graphene was prepared via an electrochemical exfoliation of graphite in (BSO3HMIm)(HSO4) solution, then (BSO3HMIm)(HSO4)-modified graphene as a precursor was reacted with amine groups of KH550 for obtaining (BSO3HMIm)(HSO4)/KH550-functionalized graphene. The final products as filler into carboxylated acrylonitrile‒butadiene rubber (XNBR) improve the dynamic mechanical properties. The improvement in the dynamic mechanical properties of the nanocomposite mainly depends on high interfacial interaction and graphene's performance characteristics, as well as a good dispersion between functionalized graphene and the XNBR matrix.

Effect of Hindered Phenol Crystallization on Properties of Organic Hybrid Damping Materials.

Organic hybrid damping materials have achieved sustainable development in recent years for superior damping properties due to the hydrogen bonding of hindered phenol. However, the aggregation and crystallization of hindered phenol in the matrix can lead to a sharp decline in material properties. Thus, a series of hindered phenol hybrid carboxylated nitrile rubber (XNBR) composites with different types and contents of hindered phenol were prepared by melt blending to study the effects of different hindered phenol on the properties of organic hybrid damping materials. A dynamic mechanical analyzer (DMA) and scanning electron microscope (SEM) were used to study the dynamic mechanical properties and cross-section morphology of composites. X-ray diffraction (XRD) was used to study the crystallization of hindered phenol. The results show that the properties of organic hybrid damping materials were affected by the structure of hindered phenol, and that hindered phenol molecules with a linear structure had better performances. The greater the number of hydrogen bonds between hindered phenol and the XNBR matrix, the more difficult it was for the hindered phenol to crystallize.

Modification of Talc@TiO2 toward high-performance nitrile rubber application.

To improve the dispersion of talcum powder (Talc) for polymer applications, modified nano-titania powders (TiO2) using a silane coupling agent (KH550), a titanate coupling agent (NDZ201) and sodium polyacrylate (PAAS) were well adhered to the surface of Talc with a ball milling method, thereby preparing a series of mixed Talc@TiO2 particles to realize good dispersion in carboxylated acrylonitrile-butadiene rubber (XNBR). Note that Talc@TiO2 particles modified by PAAS and NDZ201 show better colloidal dispersion in anhydrous ethanol due to organification and repulsion of charge, with original Talc and NDZ201 modified Talc@TiO2 powders as a comparison. Modified Talc@TiO2 hybrid XNBR shows good performance characteristics, including damping capacity and impact resistance, depending mainly on the excellent mechanical property of Talc, good dispersion and the high adhesive force between modified Talc@TiO2 and XNBR.

Development of high sensitivity 4H-SiC detectors for fission neutron pulse shape measurements.

4H-silicon carbide (4H-SiC) detectors are well suited for measurements of fission neutron pulse shape for their compact size, excellent radiation resistance, and hydrogen free composition. The aim of this study is to improve the 4H-SiC detector's sensitivity to fission neutron pulses. 4H-SiC detectors with varied epilayer thicknesses are fabricated and then tested in the pulsed neutron field of the Chinese Fast Burst Reactor II (CFBR II). The sensitivity of the 4H-SiC detector to the CFBR II neutron pulse is increased by 139.8%, with the enlargement of epilayer thickness from 20 µm to 120 µm. By employing the proton-recoil method, the sensitivity of the 4H-SiC detector to the CFBR II neutron pulse is further increased by 11.6%. With enhanced sensitivity to fission neutron pulses, 4H-SiC detectors are promising devices for high intensity neutron pulse measurements.

Space irradiation-induced damage to graphene films.

Graphene with impressive electrical, optical, chemical and mechanical properties has promising potential applications for photoelectric devices and mechanical components installed on the space facilities, which will probably face hostile environments including high-energy particulate irradiation. Here we explored the effect of simulated space irradiation on the structure and properties of large-area single-layer and multi-layer graphene films (about four layers) including atomic oxygen (AO), electron (EL) and proton (PR). AO with strong oxidizing capacity reacts with carbon atoms of graphene films and generates carbon dioxide, high-energy PR leads to polymorphic atomic defects in graphene through collision and excitation effects. Miraculously, EL irradiation causes little damage to the graphene films because of the excellent conductivity. Graphene ripples are broken by irradiation and adapt their shape or structure with respect to the substrate via thermodynamic stability, which causes the change of the physical and mechanical properties of graphene.

Regulation of the Nampt-mediated NAD salvage pathway and its therapeutic implications in pancreatic cancer.

Nicotinamide adenine dinucleotide (NAD) is a crucial cofactor for the redox reactions in the metabolic pathways of cancer cells that have elevated aerobic glycolysis (Warburg effect). Cancer cells are reported to rely on NAD recycling and inhibition of the NAD salvage pathway causes metabolic collapse and cell death. However, the underlying regulatory mechanisms and clinical implications for the NAD salvage pathway in pancreatic ductal adenocarcinoma (PDAC) remain unclear. This study showed that the expression of Nampt, the rate-limiting enzyme of the NAD salvage pathway, was significantly increased in PDAC cells and PDAC tissues. Additionally, inhibition of Nampt impaired tumor growth in vitro and tumorigenesis in vivo, which was accompanied by a decreased cellular NAD level and glycolytic activity. Mechanistically, the Nampt expression was independent of Kras and p16 status, but it was directly regulated by miR-206, which was inversely correlated with the expression of Nampt in PDAC tissues. Importantly, pharmacological inhibition of Nampt by its inhibitor, FK866, significantly enhanced the antitumor activity of gemcitabine in PDAC cells and in orthotopic xenograft mouse models. In conclusion, the present study revealed a novel regulatory mechanism for Nampt in PDAC and suggested that Nampt inhibition may override gemcitabine resistance by decreasing the NAD level and suppressing glycolytic activity, warranting further clinical investigation for pancreatic cancer treatment.

Decreased TUSC3 Promotes Pancreatic Cancer Proliferation, Invasion and Metastasis.

Pancreatic cancer is an aggressive disease with dismal prognosis. It is of paramount importance to understand the underlying etiological mechanisms and identify novel, consistent, and easy-to-apply prognostic factors for precision therapy. TUSC3 (tumor suppressor candidate 3) was identified as a potential tumor suppressor gene and previous study showed TUSC3 is decreased in pancreatic cancer at mRNA level, but its putative tumor suppressor function remains to be verified. In this study, TUSC3 expression was found to be suppressed both at mRNA and protein levels in cell line models as well as in clinical samples; decreased TUSC3 expression was associated with higher pathological TNM staging and poorer outcome. In three pairs of cell lines with different NF-κB activity, TUSC3 expression was found to be reversely correlated with NF-κB activity. TUSC3-silenced pancreatic cancer cell line exhibited enhanced potential of proliferation, migration and invasion. In an orthotopic implanted mice model, TUSC3 silenced cells exhibited more aggressive phenotype with more liver metastasis. In conclusion, the current study shows that decreased immunological TUSC3 staining is a factor prognostic of poor survival in pancreatic cancer patients and decreased TUSC3 promotes pancreatic cancer cell proliferation, invasion and metastasis. The reverse correlation between NF-κB activity and TUSC3 expression may suggest a novel regulation pattern for this molecule.

IL1 Receptor Antagonist Inhibits Pancreatic Cancer Growth by Abrogating NF-κB Activation.

PURPOSE: Constitutive NF-κB activation is identified in about 70% of pancreatic ductal adenocarcinoma (PDAC) cases and is required for oncogenic KRAS-induced PDAC development in mouse models. We sought to determine whether targeting IL-1α pathway would inhibit NF-κB activity and thus suppress PDAC cell growth. EXPERIMENTAL DESIGN: We determined whether anakinra, a human IL-1 receptor (rhIL-1R) antagonist, inhibited NF-κB activation. Assays for cell proliferation, migration, and invasion were performed with rhIL-1R antagonist using the human PDAC cell lines AsPc1, Colo357, MiaPaCa-2, and HPNE/K-ras(G12V)/p16sh. In vivo NF-κB activation-dependent tumorigenesis was assayed using an orthotopic nude mouse model (n = 20, 5 per group) treated with a combination of gemcitabine and rhIL-1RA. RESULTS: rhIL-1R antagonist treatment led to a significant decrease in NF-κB activity. PDAC cells treated with rhIL-1R antagonist plus gemcitabine reduced proliferation, migration, and invasion as compared with single gemcitabine treatment. In nude mice, rhIL-1R antagonist plus gemcitabine significantly reduced the tumor burden (gemcitabine plus rhIL-1RA vs. control, P = 0.014). CONCLUSIONS: We found that anakinra, an FDA-approved drug that inhibits IL-1 receptor (IL-1R), when given with or without gemcitabine, can reduce tumor growth by inhibiting IL1α-induced NF-κB activity; this result suggests that it is a useful therapeutic approach for PDAC.

Graphene with outstanding anti-irradiation capacity as multialkylated cyclopentanes additive toward space application.

Multialkylated cyclopentanes (MACs), a class of synthetic hydrocarbon fluid have attracted intensive interest as possible space lubricants due to a series of unique physical and chemical properties. Here, we used graphene with high mechanical strength and chemical inertness as lubricant additive to explore its potential for space application. The effects of space irradiation on graphene and the tribological properties of graphene as lubricant additive were firstly investigated in detail under simulated space environment composed of high vacuum, high/low temperature and irradiation. Results demonstrate that graphene not only possesses outstanding anti-irradiation capacity but also significantly improves the space performance and tribological properties of MACs, which depends on the excellent physicochemical properties and high load-carrying ability of graphene as well as more effective separation of the sliding surfaces.

Improving Tribological Properties of Multialkylated Cyclopentanes under Simulated Space Environment: Two Feasible Approaches.

Space mechanisms require multialkylated cyclopentanes (MACs) more lubricious, more reliable, more durable, and better adaptive to harsh space environments. In this study, two kinds of additives were added into MACs for improving the tribological properties under simulated space environments: (a) solid nanoparticles (tungsten disulfide (WS2), tungsten trioxide (WO3), lanthanum oxide (La2O3), and lanthanum trifluoride (LaF3)) for steel/steel contacts; (b) liquid additives like zinc dialkyldithiophosphate (ZDDP) and molybdenum dialkyldithiocarbamate (MoDTC) for steel/steel and steel/diamond-like carbon (DLC) contacts. The results show that, under harsh simulated space environments, addition of the solid nanoparticles into MACs allows the wear to be reduced by up to one order magnitude, while liquid additives simultaneously reduce friction and wear by 80% and 93%, respectively. Friction mechanisms were proposed according to surface/interface analysis techniques, such as X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). The role of solid nanoparticles in reducing friction and wear mainly depends on their surface enhancement effect, and the liquid additives are attributed to the formation of tribochemical reaction film derived from ZDDP and MoDTC on the sliding surfaces.