Strength-Plasticity Relationship and Intragranular Nanophase Distribution of Hybrid (GNS + SiCnp)/Al Composites Based on Heat Treatment.

The distribution of reinforcements and interfacial bonding state with the metal matrix are crucial factors in achieving excellent comprehensive mechanical properties for aluminum (Al) matrix composites. Normally, after heat treatment, graphene nanosheets (GNSs)/Al composites experience a significant loss of strength. Here, better performance of GNS/Al was explored with a hybrid strategy by introducing 0.9 vol.% silicon carbide nanoparticles (SiCnp) into the composite. Pre-ball milling of Al powders and 0.9 vol.% SiCnp gained Al flakes that provided a large dispersion area for 3.0 vol.% GNS during the shift speed ball milling process, leading to uniformly dispersed GNS for both as-sintered and as-extruded (0.9 vol.% SiCnp + 3.0 vol.% GNS)/Al. High-temperature heat treatment at 600 °C for 60 min was performed on the as-extruded composite, giving rise to intragranular distribution of SiCnp due to recrystallization and grain growth of the Al matrix. Meanwhile, nanoscale Al4C3, which can act as an additional reinforcing nanoparticle, was generated because of an appropriate interfacial reaction between GNS and Al. The intragranular distribution of both nanoparticles improves the Al matrix continuity of composites and plays a key role in ensuring the plasticity of composites. As a result, the work hardening ability of the heat-treated hybrid (0.9 vol.% SiCnp + 3.0 vol.% GNS)/Al composite was well improved, and the tensile elongation increased by 42.7% with little loss of the strength. The present work provides a new strategy in achieving coordination on strength-plasticity of Al matrix composites.

Effect of Particle Strength on SiCp/Al Composite Properties with Network Architecture Design.

Recent works have experimentally proven that metal matrix composites (MMCs) with network architecture present improved strength-ductility match. It is envisaged that the performance of architecturally designed composites is particularly sensitive to reinforcement strength. Here, reinforcing particles with various fracture strengths were introduced in numerical models of composites with network particle distribution. The results revealed that a low particle strength (1 GPa) led to early-stage failure and brittle fracture. Nevertheless, a high particle strength (5 GPa) delayed the failure behavior and led to ductile fracture at the SiC/Al-Al macro-interface areas. Therefore, the ultimate tensile strengths (UTS) of the network SiC/Al composites increased from 290 to 385 MPa, with rising particle strength from 1 to 5 GPa. Based on the composite property, different particle fracture threshold strengths existed for homogeneous (~2.7 GPa) and network (~3.7 GPa) composites. The higher threshold strength in network composites was related to the increased stress concentration induced by network architecture. Unfortunately, the real fracture strength of the commercial SiC particle is 1-2 GPa, implying that it is possible to select a high-strength particle necessary for efficient network architecture design.

Reproductive outcome of septate uterus after hysteroscopic treatment with neodymium:YAG laser.

OBJECTIVE: The aim of this study was to assess fertility outcome and obstetrical prognosis of 46 patients after hysteroscopic section of uterine septa with neodysmium:yttrium-aluminum-garnet (Nd:YAG) laser. BACKGROUND DATA: Approximately 15-25% of spontaneous miscarriages are related to Müllerian fusion defects, most of which are associated with uterine septa. Operative hysteroscopy is a safe and effective treatment for uterine septa. METHODS: Forty-six sterile patients with septate uterus received hysteroscopic metroplasty with Nd:YAG laser. Forty-one patients with incomplete septate uterus were under the guidance of B-ultrasonography, while the other 5 patients with complete septate uterus were treated by laparoscopy. RESULTS: The metroplasty was successfully conducted in 45 patients, with a success rate of 98% (45 /46). Postoperative follow-up examinations of 28 patients revealed pregnancy within 12 months in 20 patients, 16 of whom acquired term delivery. The pregnancy rate within 1 year was 71%. CONCLUSION: Hysteroscopic treatment of septate uterus with Nd:YAG laser is effective. The cervix may not be excessively dilated, the intraoperative bleeding can be thoroughly controlled, and the procedure under local anesthesia is relatively safe.

[Preliminary studies on pathogenic factors of human cytomegalovirus infection].

OBJECTIVE: To investigate the pathogenic factors of human cytomegalovirus (HCMV) infections. METHODS: Totally 36 serum samples were obtained from early pregnant woman and examined with ELISA for anti-HCMV antibody IgG and IgM. After artificial abortion,chorionic villus and decidua were also examined with polymerase chain reaction (PCR) for HCMV-DNA. When the results of PCR were positive, pathological changes of these chorionic villus and decidua were analyzed. RESULTS: The results showed that only 10 samples were PCR positive while IgG and/or IgM antibody to HCMV was positive. After infection with HCMV, different changes occurred in chorionic villus and decidual trophoblastic cells placental villus were hyperplasic and decidua cells degenerated and necrotized followed by lymphocytes infiltration. CONCLUSION: These pathological changes may be one of pathogenic factors of HCMV.