Nanoscale textured silicon and its passivation are explored by simple low-cost metal-assisted chemical etching and thermal oxidation, and large-area black silicon was fabricated both on single-crystalline Si and multicrystalline Si for solar cell applications. When the Si surface was etched by HF/AgNO(3) solution for 4 or 5 min, nanopores formed in the Si surface, 50-100 nm in diameter and 200-300 nm deep. The nanoscale textured silicon surface turns into an effective medium with a gradually varying refractive index, which leads to the low reflectivity and black appearance of the samples. Mean reflectance was reduced to as low as 2% for crystalline Si and 4% for multicrystalline Si from 300 to 1000 nm, with no antireflective (AR) coating. A black-etched multicrystalline-Si of 156 mm × 156 mm was used to fabricate a primary solar cell with no surface passivation or AR coating. Its conversion efficiency (η) was 11.5%. The cell conversion efficiency was increased greatly by using surface passivation process, which proved very useful in suppressing excess carrier recombination on the nanostructured surface. Finally, a black m-Si cell with efficiency of 15.8% was achieved by using SiO(2) and SiN(X) bilayer passivation structure, indicating that passivation plays a key role in large-scale manufacture of black silicon solar cells.

Ammonium polyphosphate (APP), which is an important component of intumescent flame retardant (IFR), has been modified with (3-aminopropyl) triethoxysilane (KH550) and silicon resin to enhance its hydrophobic properties. The structure and properties of the modified ammonium polyphosphate (MAPP) were well-characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), and water contact angle (CA). The water CA of MAPP was as high as 148°, which demonstrated that MAPP possessed excellent hydrophobic properties. MAPP and APP were mixed with triazine, which is a char-foaming agent (CFA), and polypropylene (PP) to prepare PP/MAPP/CFA and PP/APP/CFA composites, respectively. The fire retardancy and thermal degradation behavior of PP/MAPP/CFA and PP/ APP/CFA composites were investigated by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimetry, and thermogravimetric analysis. The surface and fracture morphologies were evaluated by SEM. The mechanical properties was analyzed by tensile, flexural, and izod impact tests. The results demonstrated that the MAPP imparted excellent flame retardancy of PP/MAPP/CFA systems, along with a higher LOI value, UL-94 rating, and lower heat release rate and total heat released values. The modification enhanced the interfacial adhesion, mechanical stability, and thermal stability of PP/MAPP/CFA composites. Moreover, PP/MAPP/CFA composites with the thickness of 1.6 mm can still pass the UL-94 V-0 rating after treatment with water for 168 h at 70°C, meanwhile the weight loss rate was decreased from 2.31% for PP/APP/CFA composites to 0.85%, indicating excellent water resistance. This investigation shows a promising formulation for water-resistant intumescent flame-retardant PP composites with extraordinary properties.

A novel phosphonate flame retardant additive bis(2,6-dimethyphenyl) phenylphosphonate (BDMPP) was synthesized from phenylphosphonic dichloride and 2,6-dimethyl phenol, and its chemical structure was characterized by Fourier transform infrared (FTIR) spectroscopy, 1 H and 31 P nuclear magnetic resonance. The prepared BDMPP and curing agent m-phenylenediamine were blended into epoxy resins (EP) to prepare flame retardant EP thermosets. The effect of BDMPP on fire retardancy and thermal degradation behavior of EP/BDMPP thermosets was investigated by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimeter and thermalgravimetric analysis (TGA). The morphologies of char residues of the EP thermosets were investigated by scanning electron microscopy (SEM) and the water resistant properties of thermosets were evaluated by putting the samples into distilled water at 708C for 168 h. The results demonstrated that the cured EP/14 wt % BDMPP composites with the phosphorus content of 1.11 wt % successfully passed UL-94 V-0 flammability rating and the LOI value was as high as 33.8%. The TGA results indicated that the introduction of BDMPP promoted EP matrix decomposed ahead of time compared with that of pure EP and led to a higher char yield at high temperature. The incorporation of BDMPP enhanced the mechanical properties and reduced the moisture absorption of EP thermosets. The morphological structures of char residue revealed that BDMPP benefited to the formation of a more compact and homogeneous char layer on the materials surface during burning, which prevented the heat transmission and diffusion, limit the production of combustible gases and then lead to the reduction of the heat release rate. After water resistance tests, EP/ BDMPP thermosets still remained excellent flame retardancy.

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