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Surface roughening of hollow glass microspheres (HGMs) is a necessary step determining their adhesion ability with the following electroless plated metallization coating. In this paper, a new KF roughening and alkali washing strategy was proposed to replace HF roughening as a surface pretreatment for the following electroless plating metallization. In order to remove the byproduct of K2SiF6 from the roughening reaction of KF with HGMs, NaOH washing and KOH washing were conducted, the former of which was found to dissolve K2SiF6 effectively. The effects of KF roughening temperature, alkali concentration and HGMs loading on the recovery ratio, phase composition, surface morphology and performance of HGMs were investigated, through which such a pretreating strategy was found to not only decrease the damage ratio of HGMs compared to that by HF roughening, but also render the metallized HGMs a competitive absorbing ability for the electromagnetic wave in X-band and Ku-band. Finally, the related surface treatment and electroless plating mechanism were discussed. This paper illustrates successfully a new pretreatment strategy for development of lightweight HGMs-supported functional materials.

Roughening of non-conductive substrate ceramic materials with hydrofluoric acid (HF) is usually an essential step to enhance adhesion of the coating by electroless chemical plating. However, the violent reaction between HF and the hollow glass microspheres (HGMs) usually causes breakage and damage of the thin shells of HGMs. This paper proposes a modified roughening strategy for Ni electroless plating, i.e., eroding HGMS slowly with a mixture of sodium fluoride (NaF) and hydrochloric acid (HCl). The Na2SiF6 by-products from the reaction of NaF with SiO2 were erased by the following NaOH washing to expose the surface of HGMs without any obvious pores or breakage. Such a modified roughening and followed alkali washing strategy can thus not only reduce the surface corrosion, but also hinder the further damage of HGMs by covering Na2SiF6 sediments. The successive plating of uniform Ni nanoparticles on HGMs was conducted, and the related mechanism was discussed in detail.

Precise baseline measurement plays an essential role in interferometric SAR (InSAR) mission. In order to obtain high-accuracy of land elevation, baseline measurement system with high precision is currently required at large inter-antenna distance. In recent years, baseline estimation method and GPS-based measurement system have made some progress in practical applications. However, such two measurement schemes are highly dependent on massive ground post-processing techniques, which prevent from real-time implementation. As a promising alternative, laser and camera measurement system has drawn widespread attention for InSAR utilization nowadays. In this paper, by incorporating a femtosecond comb laser into the laser-camera system, we propose a novel framework for baseline measurement, which could realize high-accuracy observation in real time. After calibrating the laser and camera compartments simultaneously, we validate the performance of the proposed system using a laser tracker as a reference equipment on a hyper-stable platform. The experimental results have shown that the errors of position and attitude are less than 0.2 mm and 15 arcseconds at 60 m distance respectively, which have demonstrated the sub-millimeter precision, long-range and high-speed capabilities of our system.

The direct conversion of chitin biomass to 5-hydroxymethylfurfural (5-HMF) over metal salts catalysts was studied systemically in a dimethyl sulfoxide -water solvent mixture under hydrothermal conditions. N-acetyl- d -glucosamine (GlcNAc) was chosen as model substrate to investigate the reaction. Sixteen catalysts were investigated, and FeCl2 exhibited the best performance –achieving 5-HMF with yields of 26.6% and 37.9% from chitosan and GlcNAc, respectively, at 180 °C under hydrothermal conditions. These are the highest yields reported to date for 5-HMF obtained from chitosan and GlcNAc. Furthermore, the substrate scope was expanded from GlcNAc to various chitosan polymers with different molecular weights and chitin, 5-HMF yield from polymers were generally lower than that from GlcNAc.

The dehydration of chitosan to 5-hydroxymethylfurfural (HMF) via hydrothermal conversion was investigated in the presence of Bronsted–Lewis acidic ionic liquids. The catalytic effect of different Bronsted- and Lewis-acidic sites and the molar fraction of Lewis-acidic sites were investigated in detail. It was found that Bronsted–Lewis acidic ionic liquids ([Hmim][HSO4]–0.5FeCl2) exhibited good catalytic performance, furnishing HMF in 44.11% yield. Furthermore, the effects of reaction temperature, time, and amount of catalyst were also investigated. The optimal reaction conditions were obtained for a 1.25 wt% aqueous solution of the catalyst under hydrothermal conditions (180 °C for 4 h). A high HMF yield of 44.11% was obtained starting from 50 mg of chitosan. The Bronsted–Lewis acidic ionic liquid catalysts could be recycled by simple separation and exhibited constant activity in four successive trials.

Six Na+/montmorillonite (MMT) – supported thiazolium (TM) ionic liquids (ILs), MMT–[TM], which are precatalysts to N-heterocyclic carbene (NHC) catalysts, have been synthesized and employed to catalyze the highly selective condensation of furfural (FF) and 5-hydroxymethylfurfural (HMF) into C10 and C12 furoins, respectively. Among them, five supported [TM] salts carrying the electron-donating group exhibit excellent catalytic activity. Thus, supported NHC catalysts, generated in situ from activation of MMT–[TM] with Et3N, afford C10 and C12 furoins in 97–99% and 97–98% yield, respectively. This condensation reaction is also carried out under solvent-free conditions, and the catalysts can be readily recycled, showing no noticeable loss in their catalytic activity over four consecutive recycles. Thus, these desired features possessed by the current catalyst system have enabled the development of the greener and more environmentally benign process for the upgrading of FF and HMF.

Here, N-acetyl-d-glucosamine (GlcNAc), the monomer composing the second most abundant biopolymer, chitin, was efficiently converted into 5-hydroxymethylfurfural (5-HMF) using ionic liquid (IL) catalysts in a water/dimethyl sulfoxide (DMSO) mixture solvent. Various reaction parameters, including reaction temperature and time, DMSO/water mass ratios and catalyst dosage were optimized. A series of ILs with different structures were analyzed to explore their impact on GlcNAc conversion. The substrate scope was expanded from GlcNAc to d-glucosamine, chitin, chitosan and monosaccharides, although 5-HMF yields obtained from polymers and other monosaccharides were generally lower than those from GlcNAc. Moreover, the IL N-methylimidazolium hydrogen sulfate ([Hmim][HSO4]) exhibited the best catalyst performance (64.6% yield) when GlcNAc was dehydrated in a DMSO/water mixture at 180 °C for 6 h without the addition of extra catalysts. To summarize, these results could provide knowledge essential to the production of valuable chemicals that are derived from renewable marine resources and benefit biofuel-related applications.