Spontaneously Conversion from Film to High Crystalline Quality Stripe during Molecular Beam Epitaxy for High Sn Content GeSn.

Two series of Ge0.8Sn0.2 samples were grown on Ge buffered Si substrate by molecular beam epitaxy (MBE) to investigate the influence of growth temperature and film thickness towards the evolution of surface morphology. A novel phenomena was observed that the Ge0.8Sn0.2 film was segregated and relaxed by the formation of GeSn stripes on the film. Under specific growth condition, the stripes can cover nearly the whole surface. XRD, TEM, AFM, PL and TEM results indicated that the stripes are high quality single crystalline GeSn with Sn content around 5%. The formation of GeSn stripes proposes an effective strategy to fabricate high crystalline quality GeSn stripe on Si, where the Ge0.8Sn0.2 film serves as precursor and the segregated Sn works as catalyst droplets. This technique has great potential for future optoelectronic and microelectronic applications.

[Sewage sludge conditioning by bioleaching combined with Fenton-like oxidation].

Bioleaching combined with Fenton-like oxidation was used to condition sewage sludge. The results showed that it took approximately 1 d to decrease pH from 6.9 to 2.5 by bioleaching, with fixed sulfur power and FeSO4 x 7H2O dosages of 3 g x L(-1) and 8 g x L(-1), respectively. After bioleaching, the volatile solids(VS) reduction was 13.4%, and the specific resistance to filtration(SRF) dropped from 3.1 x 10(9)s2 x g(-1) to 1.5 x 10(9)s2 x g(-1) with a reduction of 51.6%, but the bioleached sludge was still difficult to be dewatered. The bioleached sludge was further oxidized by Fenton-like oxidation. The results indicated that the optimal H2O2 dosage and reaction time were 3.3 g x L(-1) and 60 min, respectively. Under the optimal conditions, VS reduction was 30.8%, SRF was declined to 1.9 x 10(8) s2 x g(-1) with a reduction of 93.9%, and the moisture of sludge cake was 76.9%. After treated by bioleaching combined with Fenton-like oxidation, the dewaterability and stability of sewage sludge were significantly improved. Besides, the combined technology was more efficient in conditioning sewage sludge than single Fenton-like oxidation.

Feasibility of bioleaching combined with Fenton oxidation to improve sewage sludge dewaterability.

A novel joint method of bioleaching with Fenton oxidation was applied to condition sewage sludge. The specific resistance to filtration (SRF) and moisture of sludge cake (MSC) were adopted to evaluate the improvement of sludge dewaterability. After 2-day bioleaching, the sludge pH dropped to about 2.5 which satisfied the acidic condition for Fenton oxidation. Meanwhile, the SRF declined from 6.45×10(10) to 2.07×10(10) s2/g, and MSC decreased from 91.42% to 87.66%. The bioleached sludge was further conditioned with Fenton oxidation. From an economical point of view, the optimal dosages of H2O2 and Fe2+ were 0.12 and 0.036 mol/L, respectively, and the optimal reaction time was 60 min. Under optimal conditions, SRF, volatile solids reduction, and MSC were 3.43×10(8) s2/g, 36.93%, and 79.58%, respectively. The stability and settleability of sewage sludge were both improved significantly. Besides, the results indicated that bioleaching-Fenton oxidation was more efficient in dewatering the sewage sludge than traditional Fenton oxidation. The sludge conditioning mechanisms by bioleaching-Fenton oxidation might mainly include the flocculation effects and the releases of extracellular polymeric substances-bound water and intercellular water.