FABRICATION OF SiCf/SiC–ZrB2 COMPOSITES BY A HYBRID PROCESS OF ALTERNATING CURRENT ELECTROPHORETIC DEPOSITION (AC-EPD) AND HOT PRESSING

In this study, we report on the fabrication of continuous SiC fiber-reinforced SiC–ZrB2 ceramic matrix composites (SiCf/SiC–ZrB2) through a hybrid process of slurry impregnation by electrophoretic deposition and hot pressing. An effective impregnation of the slurry into the fine voids of fiber preform is essential to fabricate dense composites, which was achieved by a simple, fast and efficient electrophoretic deposition method. With increased interest in ultra-high temperature ceramics (UHTCs), there has been a significant effort on the development of SiC–ZrB2 composites. Numerous efforts have been also made on the incorporating of fiber reinforcement phase into these UHTCs to enhance overall mechanical properties in recent years. In this regard, SiCf/SiC–ZrB2 composites were fabricated by infiltrating a SiC–ZrB2 matrix phase containing Sc2O3 sintering aid into the TyrannoTM-SA grade-3 fabrics coated with pyrolytic carbon and SiC interphase layers using an AC electrophoretic deposition (AC-EPD) combined with ultrasonication. AC-EPD was performed using a dual electrode system under an applied voltage of 20 V for 30 min. The zeta potential of the slurry was set to ≥ +40 mV at pH = 10 to achieve uniform infiltration of constituent particles into the preform. After infiltrating water-based slurry into the fine voids of fabrics by AC-EPD, 15 layers of fabrics were stacked and laminated. Hot pressing was carried out at 1750oC in an Ar atmosphere after binder burnout. The composite densities, microstructures and mechanical properties as a function of the various processing parameters along with the effectiveness of AC-EPD will be discussed in detail

Canagliflozin and renal outcomes in type 2 diabetes and nephropathy

BACKGROUND Type 2 diabetes mellitus is the leading cause of kidney failure worldwide, but few effective long-term treatments are available. In cardiovascular trials of inhibitors of sodium–glucose cotransporter 2 (SGLT2), exploratory results have suggested that such drugs may improve renal outcomes in patients with type 2 diabetes. METHODS In this double-blind, randomized trial, we assigned patients with type 2 diabetes and albuminuric chronic kidney disease to receive canagliflozin, an oral SGLT2 inhibitor, at a dose of 100 mg daily or placebo. All the patients had an estimated glomerular filtration rate (GFR) of 30 to <90 ml per minute per 1.73 m2 of body-surface area and albuminuria (ratio of albumin [mg] to creatinine [g], >300 to 5000) and were treated with renin–angiotensin system blockade. The primary outcome was a composite of end-stage kidney disease (dialysis, transplantation, or a sustained estimated GFR of <15 ml per minute per 1.73 m2), a doubling of the serum creatinine level, or death from renal or cardiovascular causes. Prespecified secondary outcomes were tested hierarchically. RESULTS The trial was stopped early after a planned interim analysis on the recommendation of the data and safety monitoring committee. At that time, 4401 patients had undergone randomization, with a median follow-up of 2.62 years. The relative risk of the primary outcome was 30% lower in the canagliflozin group than in the placebo group, with event rates of 43.2 and 61.2 per 1000 patient-years, respectively (hazard ratio, 0.70; 95% confidence interval [CI], 0.59 to 0.82; P=0.00001). The relative risk of the renal-specific composite of end-stage kidney disease, a doubling of the creatinine level, or death from renal causes was lower by 34% (hazard ratio, 0.66; 95% CI, 0.53 to 0.81; P<0.001), and the relative risk of end-stage kidney disease was lower by 32% (hazard ratio, 0.68; 95% CI, 0.54 to 0.86; P=0.002). The canagliflozin group also had a lower risk of cardiovascular death, myocardial infarction, or stroke (hazard ratio, 0.80; 95% CI, 0.67 to 0.95; P=0.01) and hospitalization for heart failure (hazard ratio, 0.61; 95% CI, 0.47 to 0.80; P<0.001). There were no significant differences in rates of amputation or fracture. CONCLUSIONS In patients with type 2 diabetes and kidney disease, the risk of kidney failure and cardiovascular events was lower in the canagliflozin group than in the placebo group at a median follow-up of 2.62 years

Strain mediated magnetoelectric coupling in a NiFe2O4-BaTiO3 multiferroic composite

In this paper we demonstrate significant magnetoelectric coupling in ferrimagnetic, NiFe2O4, and ferroelectric, BaTiO3, multiferroic composite bulk materials by measuring temperature dependent magnetization. X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy data show that the two phases coexist with a highly crystalline and sharp interface without any detectable impurities, which enables significant magnetoelectric (ME) coupling. The temperature dependent magnetization data of the composite clearly show the jumps in magnetization curves at the structural phase transitions of BaTiO3, thereby indicating their origin in ME coupling. The change in coercivity of composite sample in different ferroelectric phases of BaTiO3 has been observed compared to the NiFe2O4 sample. The different lattice strains corresponding to different ferroelectric phases of BaTiO3 could be the driving force for modulating the magnetization and coercivity of the composite material. This is clear evidence of strain mediated ME coupling in ferrimagnetic and ferroelectric composite materials

Fabrication of SiCf/SiC composites through hybrid processing via chemical vapor infiltration, electrophoretic deposition, and liquid silicon infiltration

The present work demonstrates the effectiveness of a novel hybrid process comprising chemical vapor infiltration (CVI), electrophoretic deposition (EPD), and liquid silicon infiltration (LSI) techniques for the successful fabrication of low-porosity SiCf/SiC composites. For this purpose, fiber/matrix interphase dual coating layers of BN and SiC were coated onto SiC fabrics using CVI. A ceramic matrix consisting of SiC and carbon black nanoparticles was then infiltrated into the fine voids of the fabrics using EPD. Finally, LSI was performed to obtain dense microstructures with low porosities by filling the remaining small gaps and reacting Si with C to form SiC. Microstructural results observed by scanning electron microscopy revealed a dense structure with no damage to the fibers. The experimental density was found to be 2.62 g/cc, with an open porosity of 0.55. The room-temperature flexural strength was evaluated to be 111 MPa, and the composites displayed little fiber pull-out

Enhanced Thermal Stability under DC Electrical Conductivity Retention and Visible Light Activity of Ag/TiO₂@Polyaniline Nanocomposite Film

The development of organic–inorganic photoactive materials has resulted in significant advancements in heterogeneous visible light photocatalysis. This paper reports the synthesis of visible light-active Ag/TiO₂@Pani nanocomposite film via a simple biogenic–chemical route. Electrically conducting Ag/TiO₂@Pani nanocomposites were prepared by incorporating Ag/TiO₂ in <i>N</i>-methyl-2-pyrrolidone solution of polyaniline (Pani), followed by the preparation of Ag/TiO₂@Pani nanocomposite film using solution casting technique. The synthesized Ag/TiO₂@Pani nanocomposite was confirmed by UV–visible spectroscopy, photoluminescence spectroscopy, scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The Ag/TiO₂@Pani nanocomposite film showed superior activity towards the photodegradation of methylene blue under visible light compared to Pani film, even after repeated use. Studies on the thermoelectrical behavior by DC electrical conductivity retention under cyclic aging techniques showed that the Ag/TiO₂@Pani nanocomposite film possessed a high combination of electrical conductivity and thermal stability. Because of its better thermoelectric performance and photodegradation properties, such materials might be a suitable advancement in the field of smart materials in near future