Developing Mg-Gd-Dy-Ag-Zn-Zr Alloy with High Strength via Nano-Precipitation.

A high-performance Mg-10Gd-4Dy-1.5Ag-1Zn-0.5Zr (wt.%, EQ142X) alloy was designed by multi-element composite addition in this work, obtaining a high yield strength (~396 MPa) and ultimate tensile strength (~451 MPa) after hot extrusion and ageing. The high strength is mainly related to fine grains and nano-precipitates, especially the latter. ß' and γ″ nano-precipitation with high fractions are the main strengthening phases, leading to a strengthening increment of ~277 MPa. Moreover, the multi-element alloying in this study promotes the basal-prismatic network strengthening structure, composed of ß' nano-precipitation with (1-210) habit planes, γ″ nano-precipitation with (0001) habit planes, basal plane stacking faults and 14H-long period stacking ordered phase. In addition, the dislocations and fine grains introduced by the hot-extrusion process not only accelerate the precipitation rate of nanostructure and thus improve the ageing hardening efficiency, but also facilitate the formation of more uniform and finer nano-precipitation. Thus, it is proposed that introducing nano-precipitates network into fine-grained structure is an effective strategy for developing high-strength Mg alloys.

High-Strength ß-Phase Magnesium-Lithium Alloy Prepared by Multidirectional Rolling.

Magnesium-lithium alloys are popular in the lightweight application industry for their very low density. However, as the lithium content increases, the strength of the alloy is sacrificed. Improving the strength of ß-phase Mg-Li alloys is urgently needed. The as-rolled Mg-16Li-4Zn-1Er alloy was multidirectionally rolled at various temperatures in comparison to conventional rolling. The results of the finite element simulations showed that multidirectional rolling, as opposed to conventional rolling, resulted in the alloy effectively absorbing the input stress, leading to reasonable management of stress distribution and metal flow. As a result, the alloy's mechanical qualities were improved. By modifying the dynamic recrystallization and dislocation movement, both high-temperature (200 °C) and low-temperature (-196 °C) rolling greatly increased the strength of the alloy. During the multidirectional rolling process at -196 °C, a large number of nanograins with a diameter of 56 nm were produced and a strength of 331 MPa was obtained.

Pectinariidae (Annelida, Polychaeta) from the coastal waters of China, with description of new species and new records.

Pectinariidae Quatrefages, 1865 is widely distributed, and easily distinguished from other polychaetes by their characteristic semi-circular operculum with two rows of stout golden paleae and ice-cream cone-shaped tubes made of sand or shell fragments. A total of 387 specimens of pectinariids from the coastal waters of China were examined. Eleven species belonging to three genera of pectinariids were identified and described, including four new species (Amphictene jianqingi n. sp., Pectinaria lizhei n. sp., Pectinaria dayaensis n. sp., Pectinaria xiukaii n. sp.) and one new record (Pectinaria plurihamus Choi, Jung Yoon, 2017). A key to genera of Pectinariidae and recorded species from Chinese waters is given. Based on partial sequences of five genes (COI, 16S rDNA, 18S rDNA, 28S rDNA and H3), the phylogenetic relationship of pectinariids is analyzed. The three new species Amphictene jianqingi n. sp., Pectinaria lizhei n. sp. and Pectinaria dayaensis n. sp. with molecular data are well supported. Three species of Lagis (L. koreni, L. bocki and L. plurihamus), five species of Pectinaria (P. dayaensis, P. dodeka, P. gouldii, P. lizhei and P. torquata), and three species of Amphictene (A. auricoma, A. alata and A. jianqingi) do not form a well supported clade, which requires more detailed analyses.

A new species of Petta (Annelida, Pectinariidae), with comments on Pettaassimilis McIntosh, 1885.

The genus Petta Malmgren, 1866 is a small and poorly known genus of the annelid family Pectinariidae Quatrefages, 1866. A previous revision of the genus found that the type material of the species P.assimilis McIntosh, 1885 had been lost. While searching for material from the type locality, we were able to examine material from a similar area but collected in much shallower water from off South Africa which represents another undescribed species of Petta. The new species, Pettabrevis sp. nov., is described and compared to P.assimilis McIntosh, 1885, and a revised key to all species in the genus is provided.

Annelids of the eastern Australian abyss collected by the 2017 RV 'Investigator' voyage.

In Australia, the deep-water (bathyal and abyssal) benthic invertebrate fauna is poorly known in comparison with that of shallow (subtidal and shelf) habitats. Benthic fauna from the deep eastern Australian margin was sampled systematically for the first time during 2017 RV 'Investigator' voyage 'Sampling the Abyss'. Box core, Brenke sledge, and beam trawl samples were collected at one-degree intervals from Tasmania, 42°S, to southern Queensland, 24°S, from 900 to 4800 m depth. Annelids collected were identified by taxonomic experts on individual families around the world. A complete list of all identified species is presented, accompanied with brief morphological diagnoses, taxonomic remarks, and colour images. A total of more than 6000 annelid specimens consisting of 50 families (47 Polychaeta, one Echiura, two Sipuncula) and 214 species were recovered. Twenty-seven species were given valid names, 45 were assigned the qualifier cf., 87 the qualifier sp., and 55 species were considered new to science. Geographical ranges of 16 morphospecies extended along the eastern Australian margin to the Great Australian Bight, South Australia; however, these ranges need to be confirmed with genetic data. This work providing critical baseline biodiversity data on an important group of benthic invertebrates from a virtually unknown region of the world's ocean will act as a springboard for future taxonomic and biogeographic studies in the area.

Two new species of Sabellariidae (Annelida, Polychaeta) from the abyss of eastern Australia.

In May-June 2017 an expedition on board RV 'Investigator' sampled benthic communities along the lower slope and abyss of eastern Australia from off Tasmania to the Coral Sea. Over 200 sabellariid specimens of the genera Phalacrostemma and Gesaia were collected during the voyage and deposited in the Australian Museum. Here we describe two new species Gesaia csiro n. sp. (4414-4436 m) and Phalacrostemma timoharai n. sp. (1013-1093 m). We did not formally describe another species of Phalacrostemma due to poor condition of the single specimen. Gesaia csiro n. sp. is the first record of the genus from Australian waters (only a planktonic larva attributed to the genus has previously been recorded), and it can be distinguished from other congeners by the smooth surface of inner paleae, distal thecae of outer paleae with long, irregular and expanded distal fringe and circled distal margin. Phalacrostemma timoharai n. sp. differs from congeners by the following combination of characters: presence of the buccal flap, absence of tentacular filament, 18-22 pairs of outer paleae, two pairs of neuropodial cirri on first thoracic segment, and only one pair of lateral lobes on second thoracic segment. Morphological descriptions are accompanied by mitochondrial cytochrome c oxidase subunit 1 (COI) and ribosomal (16S, 18S and 28S) sequence data. A key to all Australian species of sabellariids is given.

A revision of Australian Pectinariidae (Polychaeta), with new species and new records.

Samples of Pectinariidae in the Australian Museum and Museums of Victoria, Australia were examined. Thirteen species were identified, including three additional records of previously recorded species of Amphictene and two new species, A. cercusa n. sp. and A. undulata n. sp., two species of the genus Lagis which has not previously been recorded from Australia, including a new species, L. portus n. sp., and five additional records of previously recorded species of Pectinaria and one new species, P. ningalooensis n. sp. The study revealed additional characters which are useful to identify species of pectinariids, a pair of ear-shaped lobes which are adjacent to both sides of dorsal base of cephalic veil in species of Pectinaria and Amphictene, but in Lagis they are present between the buccal cavity and lateral margin of segment 1; and a pair of ventral lappets which have not previously been described on the lateral margin of segment I in all species of pectinariids from Australia. For species where numerous individuals were available for study, we investigated how some characters, change with increasing body size. A key to all recorded species from Australia is given, but does not imply any phylogenetic relationships.

A revision of the genus Petta Malmgren, 1866 (Annelida: Pectinariidae), with two new species from deep waters of southeastern Australia, and comments on phylogeny of the family.

Petta Malmgren, 1866 is a small and poorly known genus of the annelid family Pectinariidae Quatrefages, 1866. Prior to this study, the genus comprised four species P. pusilla Malmgren, 1866 (type locality Gullmarsfjord, west coast of Sweden), P. assimilis McIntosh, 1885 (type locality between Prince Edward and Kerguelen Island, southern Indian Ocean), P. pellucida (Ehlers, 1887) (type locality Santarem Channel between Cay Sal Bank and Bahamas, Caribbean Sea) and P. tenuis Caullery, 1944 (type locality Sulu, Philippines, tropical Pacific Ocean), the two last ones were known only from the original description. We revised the genus by re-examining the types and providing updated illustrated re-descriptions of its species, except for P. assimilis of which the type material has been lost. Commonly used morphological characters of the genus are expanded to also include new ones such as the presence of pair of lateral ear-shaped lobes adjacent to dorsal base of cephalic veil, pair of ventral lappets on segment 1, pair of dorso-lateral pads on segment 5, large basal hump on branchiae, and a rounded anterior peg with a blunt tip and a longitudinal row of two major teeth on uncini. The type species P. pusilla is recognised as having four lappets on the anterior margins of cephalic veil and a large lower lip posterior to buccal cavity. Two species P. investigatoris n. sp. and P. williamsonae n. sp. are described from deep water off the coast of southeastern Australia and represent the first records of this genus in Australian waters. A phylogenetic position of one new species was assessed in the framework of a phylogeny based on a fragment of the mitochondrial cytochrome oxidase I gene (mtCOI). An updated taxonomic key to Pectinariidae genera and all species of Petta is given.

The Effect of Y/Er and Zn Addition on the Microstructure and Mechanical Properties of Mg-11Li Alloy.

Although body-centered cubic (BCC) structural magnesium-lithium (Mg-Li) alloys have lower density and better formability than common hexagonal close-packed (HCP) Mg alloys, their applications remain limited due to their low strength. The purpose of this study is to investigate the effect of Y/Er and Zn addition on the microstructure and tensile properties of Mg-11Li alloy with a BCC structural matrix by comparing Mg-11Li, Mg-11Li-4Y-2Er-2Zn, and Mg-11Li-8Y-4Er-4Zn (wt %) alloys. The results indicate that the addition of Y/Er and Zn at a ratio of 3:1 cannot promote the formation of long-period stacking ordered structure in Mg-11Li alloy such as that in Mg-Y-Er-Zn alloys and the dominant intermetallic phases formed are BCC Mg24RE5 and face-centered cubic (FCC) Mg3RE2Zn3 phases. With an increase of the content of Y/Er and Zn in an as-cast alloy, the fraction of intermetallic particles increases and the grain size decreases. The addition of Y/Er, as well as Zn, dramatically promotes the refinement of dynamic recrystallization (DRX) during extrusion. The initial intermetallic phases induced by Y/Er and Zn addition are broken into relatively fine particles during extrusion, and this contributes to refining the dynamic recrystallized (DRXed) grains mainly by the particle stimulated nucleation mechanism. The as-extruded Mg-11Li-4Y-2Er-2Zn and Mg-11Li-8Y-4Er-4Zn alloys exhibit much higher tensile strength as compared with as-extruded Mg-11Li alloy, which is mainly ascribed to the refined DRXed grains and numerous dispersed intermetallic phase particles. It is suggested that further refinement of intermetallic particles in these extruded Mg-11Li-based alloys may lead to higher quality alloy materials with low density and excellent mechanical properties.

Development of Hot-Extruded Mg-RE-Zn Alloy Bar with High Mechanical Properties.

A new elevated-temperature high-strength Mg-4Er-2Y-3Zn-0.4Mn (wt %) alloy was developed by semi-continuous casting, solid solution treatment, and hot extrusion. W phase (Mg3(Er,Y)2Zn3) with fcc structure, long period stacking ordered phases with 18R (Mg10(Er,Y)1Zn1) and 14H (Mg12(Er,Y)1Zn1) structures, and basal plane stacking faults (SFs) was formed in the as-cast alloy, mainly due to the alloy component of (Er + Y)/Zn = 1:1 and Er/Y = 1:1 (at %). After solid solution treatment and hot extrusion, the novel microstructure feature formed in as-extruded alloy is the high number-density nanospaced basal plane SFs throughout all the dynamically recrystallized (DRXed) and un-DRXed grains, which has not been previously reported. The as-extruded alloy exhibits superior tensile properties from room temperature to 300 °C. The tensile yield strength can be maintained above 250 MPa at 300 °C. The excellent elevated-temperature strength is mainly ascribed to the formation of nanospaced basal plane SFs throughout the whole Mg matrix, fine DRXed grains ~2 µm in size, and strongly basal-textured un-DRXed grains with profuse substructures. The results provide new opportunities for the development of deformed Mg alloys with satisfactory mechanical properties for high-temperature services.

Taxonomy and distribution of Terebellides (Polychaeta: Trichobranchidae) in the northern South China Sea, with description of three new species.

Benthic ecology monitoring in the northern South China Sea revealed many individuals of the polychaete genus Terebellides (Annelida), which are common in soft sediments in shallow waters (4.5-41.0 m). Three new species of Terebellides are described, including T. guangdongensis n. sp., T. yangi n. sp. and T. ectopium n. sp. Terebellides guangdongensis n. sp. is mainly found in Guangdong waters. Terebellides yangi n. sp. and T. ectopium n. sp. are mainly found in Beibu Gulf. A key to all described species of Terebellides from the Northwestern Pacific is given.

A new species of Pectinaria (Annelida, Pectinariidae), with a key to pectinariids from the South China Sea.

Pectinariidae is a family of polychaetes building unique ice-cream cone shaped sandy tubes. Pectinaria torquatasp. n. (Pectinariidae) is described from the coastal waters of the northern South China Sea. This new species can be distinguished from all other 25 recognized species in the genus by a combination of characters: 16 chaetigers; 26-32 cirri in the cephalic veil; 11-12 pairs of cephalic spines; uncini with major teeth arranged in two rows, each with 7-8 major teeth; presence of a dorsal posterior lobe on segments 2 and 20; 4-5 pairs of curved scaphal hooks; and an anal flap with a crenulated margin. A key to all recognized pectinariids in the South China Sea is provided.

Description of a new species of Eulepethus (Annelida, Eulepethidae) from the northern South China Sea, and comments on the phylogeny of the family.

Eulepethidae is a family of scale-bearing polychaetes. Although members of this family are common inhabitants of tropical and subtropical coastal waters, their diversity is low, with only 22 recognized species in six genera. Here we describe Eulepethus nanhaiensis sp. nov. based on 12 specimens collected from the coastal waters of the northern South China Sea. This new species can be distinguished from Eulepethus hamifer, the only previously described species in this genus, by having up to two spade-shaped lateral processes in some of the anterior elytrae, a blunt-tipped acicular chaeta in the neuropodia of segment 3, and a pair of non-overlapping elytrae in each posterior segment. Phylogenetic analysis indicates that Grubeulepis and Mexieulepis are sister genera, and these two genera form the sister clade of Eulepethus.

Degraded and osteogenic properties of coated magnesium alloy AZ31; an experimental study.

BACKGROUND: Degraded and osteogenic property of coated magnesium alloy was evaluated for the fracture fixation in rabbits. METHODS: Magnesium alloy AZ31 with a different coating thickness by microarc oxidation was used, and the bilateral radial fracture model was created by the bite bone clamp. Thirty-six New Zealand white rabbits in weight of 2.5~3.0 kg were randomly divided into A, B, and C groups at four time points and other 3 rabbits as the control group without magnesium alloy. Coated magnesium alloy AZ31 was implanted on the fracture and fixed with silk thread. Indexes such as general observation, histology, X-ray, hematology, and mechanical properties were observed and detected at 2nd, 4th, 8th, and 12th week after implantation. RESULTS: Fracture in each rabbit was healed at 12th week after implantation. Among the three groups, the best results of general observation, histology, and X-ray appeared in A group without coating. However, A group showed the worst results from the perspective of mechanical properties about tensile strength and flexural strength, which failed to reach that of the natural bone at the 12th week. Comprehensive results displayed that C group with 20-µm coating was better than others in mechanical properties, while there is no difference between B and C groups in hematology. CONCLUSIONS: Degradation rate is inversely proportional to the coating thickness. And magnesium alloy with a 20-µm coating is more suitable for the fracture fixation.

Bacterial Communities in the Rhizospheres of Three Mangrove Tree Species from Beilun Estuary, China.

The bacterial communities played important roles in the high productivity mangrove ecosystem. In this study, we investigated the vertical distributions of rhizosphere bacteria from three mangrove species (Bruguiera gymnorrhiza, Kandelia candel and Aegiceras corniculatum) in Beilun Estuary, China using high throughput DNA pyrosequencing of the 16S rRNA gene. Phylogenetic analysis showed that bacterial communities from mangrove rhizosphere sediments were dominated by Proteobacteria (mostly Deltaproteobacteria and Gammaproteobacteria), followed by Chloroflexi, Bacteroidetes, Planctomycetes and Acidobacteria. However, the ANOVA analysis on Shannon and Chao1 indices indicated that bacterial communities among sediments of the three mangrove species varied more strongly than the sampling depths. In addition, the PCA result demonstrated that the bacterial communities could be separated into three groups according to the mangrove species. Moreover, the dominated orders Rhodospirillales, GCA004 and envOPS12 were significantly different among sediments of the three mangrove species. The results of this study provided valuable information about the distribution feature of rhizosphere bacteria from Chinese mangrove plants and shed insights into biogeochemical transformations driven by bacteria in rhizosphere sediments.

A new species of Amphictene (Annelida, Pectinariidae) from the northern South China Sea.

Pectinariids are a family of polychaetes commonly found in shallow coastal waters around the world, but their diversity is poorly known along the coasts of Asia. Here we describe Amphictene alata sp. n. (Pectinariidae), based on 15 specimens collected from the coastal waters of Guangdong in the northern South China Sea. This new species can be distinguished from all other 13 described species and one described subspecies of Amphictene by having a pair of dorsolateral lobes on segment 3, a pair of large lateral lobes on segment 21, and more scaphal hooks (26 to 37 pairs).

Fabrication of C-doped WO3 nanoparticle cluster arrays from PS-b-P4VP for room temperature H2 sensing.

C-doped WO3 based room temperature hydrogen sensors including nanoparticle cluster arrays and nanorods were successfully prepared by a PS-b-P4VP template based method. AFM, TEM and XPS are used to characterize the structure and composition of the samples. Analyses indicate that the C-doped WO3 nanoparticle cluster arrays are arranged in a beautiful hexagonal configuration and they are interconnected by a superthin carbon film. The cluster with sizes in the range of 12-15 nm is composed of several 4-6 nm nanocrystallites. An improved room temperature hydrogen response is found on C doped WO3 nanoparticle cluster arrays, whose response sensitivity (S), response time and recovery time are 114, 162 s and 108 s, respectively. Three aspects are used to analyze the reasons for the improved room temperature hydrogen response; the study indicates the great potential of the block copolymer based method to prepare excellent WO3 based room temperature H2 sensors.

New horizon for high performance Mg-based biomaterial with uniform degradation behavior: Formation of stacking faults.

Designing the new microstructure is an effective way to accelerate the biomedical application of magnesium (Mg) alloys. In this study, a novel Mg-8Er-1Zn alloy with profuse nano-spaced basal plane stacking faults (SFs) was prepared by combined processes of direct-chill semi-continuous casting, heat-treatment and hot-extrusion. The formation of SFs made the alloy possess outstanding comprehensive performance as the biodegradable implant material. The ultimate tensile strength (UTS: 318 MPa), tensile yield strength (TYS: 207 MPa) and elongation (21%) of the alloy with SFs were superior to those of most reported degradable Mg-based alloys. This new alloy showed acceptable biotoxicity and degradation rate (0.34 mm/year), and the latter could be further slowed down through optimizing the microstructure. Most amazing of all, the uniquely uniform in vitro/vivo corrosion behavior was obtained due to the formation of SFs. Accordingly we proposed an original corrosion mechanism for the novel Mg alloy with SFs. The present study opens a new horizon for developing new Mg-based biomaterials with highly desirable performances.

Enhancing the performance of Mg-based implant materials by introducing basal plane stacking faults.

One of the keys to allowing Mg alloys to serve as biodegradable materials is how to balance their degradation behaviours and mechanical properties in physiological environment. In this study, a novel Mg-6Ho-0.5Zn alloy (wt%) containing profuse basal plane stacking faults (SFs) is prepared. This newly-developed alloy with SFs exhibiting uniform corrosion behaviour, low corrosion rate and high mechanical properties, as compared to the classic Mg-Ho based alloys (Mg-6Ho and Mg-6Ho-1.5Zn). Furthermore, the Mg-6Ho-0.5Zn alloy shows no significant toxicity to Saos-2 cells. An original uniform corrosion mechanism is proposed by combining the special defect structure, orientation of SFs and promptly effective corrosion film. The development of the new microstructure for Mg-Ho based alloys with desirable corrosion performance has important implications in developing novel degradable Mg-based implant materials.

Preparation, mechanical and degradation properties of Mg-Y-based microwire.

Mg-Y-based microwire which offers high strength in combination of low degradation rate has been prepared for the first time by a modified melt extraction technique. A circular Mg-Y-based microwire is achieved with an extraction rate of 40m/s, which is composed of Mg matrix and an amorphous phase, and exhibits higher basal texture than that of as-cast sample. The outstanding tensile strength accompanying with an acceptable elongation is obtained with an extraction rate of 40m/s. The improved strength is mainly attributed to high solid solution strengthening, fine grain and the presence of an amorphous phase. In addition, the reduction of secondary phase and homogenous microstructure after melt extraction eliminate both pitting corrosion and micro-galvanic corrosion. A low degradation rate of 0.366mm/y is attained in a simulated body fluid, which is less than 1/10 of that of as-cast sample. These excellent mechanical properties and low degradation rate provide some prerequisites to develop bio-Mg implants. It reveals that this modified extraction technique is one of effective approaches to prepare microwire, which can be directly used for Mg-based stent self-assembly.