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Assessing the cost of vaccine preventable diseases (VPD) surveillance is becoming more important in the context of the Global Polio Eradication Initiative (GPEI) funding transition, since GPEI support to polio surveillance helped the incremental building of VPD surveillance systems in many countries, including low income countries such as Nepal. However, there is limited knowledge on the cost of conducting VPD surveillance, especially the national cost for surveillance of multiple vaccine-preventable diseases. The current study sought to calculate the economic and financial costs of Nepal’s comprehensive VPD surveillance systems from July 2016 to July 2017. At thecentral level, all surveillance units were included in the sample. At sub-national level, a purposive sampling strategy was used to select a representative sample from locations involved in conducting surveillance. The sub-national sample costs were extrapolated to the nationwide VPD surveillance system. Nepal’s total annual economic cost of VPD surveillance was USD 4.81 million or USD 0.18 per capita, while the total financial cost was USD 4.38 million or USD 0.16 per capita. Government expenditures accounted for 56% of the total economic cost, and World Health Organization accounting for 44%. The biggest cost driver was personnel accounting for 51% of the total economic cost. WHO supported trained surveillance personnel through donor funding, mainly from Global Polio Eradication Initiative. As a polio transition priority country, Nepal will need to make strategic choices to fully self-finance or seek full donor support or a mixed-financing model as polio program funding diminishes.

Three strains of members of the family

A Gram-positive, strictly aerobic, ivory-colored, rod-shaped bacterial strain, designated RN3S43T, was isolated from saline–alkaline soil, in Tumd Right Banner, Inner Mongolia, China. Strain RN3S43T grew at 10–40 °C (optimum 30 °C), pH 6.0–10.0 (optimum pH 9.0), and 0–12.5% NaCl (optimum 2–4%). It was positive to oxidase, catalase, urease, and nitrate reductase. The methyl red and Voges–Proskauer tests were negative. The phylogenetic trees based on the 16S rRNA gene sequences and genome both showed that strain RN3S43T clustered with Ruania alba YIM 93306 T and shared 95.5% and

A Gram-stain-positive, facultatively anaerobic, non-sporulating, motile with single polar flagellum, rod-shaped, indole-3-acetic acid (IAA)-producing bacterium, named M4U5P12

Two Gram-stain-negative, motile with single polar flagellum, rod-shaped bacterial strains, named SJ-9T and SJ-92T, were isolated from saline soils from Inner Mongolia, PR China. SJ-9T and SJ-92T grew at pH 6.5–10.0 and 7.0–11.0, 10–35 °C, and in the presence of 0–5 % and 0–8 % NaCl, respectively. Both strains were positive for oxidase, and negative for catalase. The results of phylogenetic analysis based on 16S rRNA gene sequences indicated that SJ-9T clustered with Luteimonas marina FR1330T (sharing 97.9 % 16S rRNA gene similarity), Luteimonas huabeiensis HB2T (96.5 %), ‘Luteimonas wenzhouensis’ YD-1 (96.6 %), and Luteimonas composti CC-YY255T (95.1 %), and shared low 16S rRNA gene similarities (T clustered with Luteimonas aestuarii B9T (98.2 %), and shared low 16S rRNA gene similarities (15 : 0 and summed feature 9 (C16 : 0 10-methyl and/or iso-C17 : 1ω9c). The major polar lipids of both strains are diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine. The only respiratory quinone for both strains is ubiquinone-8 (Q-8). The genomic DNA G+C contents are 69.3 and 70.4 mol%, respectively. The digital DNA–DNA hybridization (dDDH) and average nucleotide identity by blast (ANIb) values between the two strains were 22.6 and 77.5 %, while the values between SJ-9T and ‘L. wenzhouensis’ YD-1, L. marina FR1330T, and L. huabeiensis HB2T were 38.1, 39.2, and 21.9 %, and 82.5, 84.4, and 78.5 %, while those between SJ-92T and L. aestuarii B9T were 21.3 and 76.7 %. On the basis of the phenotypic, physiological and phylogenetic results, SJ-9T and SJ-92T represent two novel species of the genus Luteimonas , for which the names Luteimonas saliphila [type stain SJ-9T (=CGMCC 1.17377T=KCTC 82248T)] and Luteimonas salinisoli [type strain SJ-92T (=CGMCC 1.17695T=KCTC 82208T)] are proposed.

Strains of Echinicola , thought to play vital roles in the environment for their high enzyme production capacity during decomposition of polysaccharides, are ubiquitous in hypersaline environments. A Gram-negative, non-spore forming, gliding, aerobic bacterial strain, designated LN3S3T, was isolated from alkaline saline soil sampled in Tumd Right Banner, Inner Mongolia, northern PR China. Strain LN3S3T grew at 10–40 °C (optimum, 30 °C), pH 5.0–9.0 (optimum, pH 8.0) and with 0–12.5 % NaCl (optimum, 2.0 %). A phylogenetic tree based on the 16S rRNA gene sequences showed that strain LN3S3T clustered with Echinicola rosea JL3085T and Echinicola strongylocentroti MEBiC08714T, sharing 97.0, 96.7 and E. rosea JL3085T, E. strongylocentroti MEBiC08714T and all other type strains. MK-7 was the major respiratory quinone, while phosphatidylethanolamine, two unidentified phospholipids, an unidentified aminophospholipid, an unidentified lipid and two unidentified aminolipids were the major polar lipids. Its major cellular fatty acids were iso-C15 : 0, anteiso-C15 : 0 and summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c). The genome consisted of a circular 5 550 304 bp long chromosome with a DNA G+C content of 44.0 mol%. The average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA–DNA hybridization (dDDH) values of strain LN3S3T to E. rosea JL3085T and E. strongylocentroti MEBiC08714T were 82.5 and 81.5 %, 87.5 and 86.0 %, and 39.1 and 35.1 %, respectively. Based on physiological, genotypic and phylogenetic analyses, strain LN3S3T could be discriminated from its phylogenetic relatives. Echinicola soli sp. nov. is therefore proposed with strain LN3S3T (=CGMCC 1.17081T=KCTC 72458T) as the type strain.

A Gram-stain-positive, facultatively anaerobic, spore-forming, motile with unipolar biflagella, rod-shaped, indole acetic acid-producing bacterium, named LD4P30T, was isolated from a root of Suaeda salsa collected in Inner Mongolia, northern China. Strain LD4P30T grew at pH 6.0–11.0 (optimum, pH 7.0), 10–40 °C (35 °C) and in the presence of 1–15% (w/v) NaCl (5%). The strain was positive for oxidase and negative for catalase. The major cellular fatty acids of strain LD4P30T were iso-C15:0, C15:1 ω5c and anteiso-C15:0; the major polar lipids were diphosphatidylglycerol and phosphatidylglycerol; and menaquinone-7 was the only respiratory quinone. The genomic DNA G+C content was 36.7 mol%. A phylogenetic tree based on 16S rRNA gene sequences showed that strain LD4P30T clustered with Gracilibacillus thailandensis TP2-8T, Gracilibacillus saliphilus YIM 91119T and Gracilibacillus lacisalsi BH312T, and showed 99.0, 98.9, 98.0 and G. thailandensis TP2-8T, G. saliphilus YIM 91119T, G. lacisalsi BH312T and all other current type strains, respectively. The digital DNA–DNA hybridization and average nucleotide identity based on blast values between strain LD4P30T and G. saliphilus YIM 91119T, G. thailandensis TP2-8T and G. lacisalsi BH312T were 44.9, 44.7 and 44.4%, and 91.1, 91.0 and 90.8%, respectively. Based on its phenotypic, physiological and phylogenetic characteristics, strain LD4P30T represents a novel species, for which the name Gracilibacillus suaedae is proposed. The type strain is LD4P30T (=CGMCC 1.17697T=KCTC 82375T).

A Gram-stain-negative, non-motile, rod-shaped bacterial strain, named SJ-16T, was isolated from desert soil collected in Inner Mongolia, northern PR China. Strain SJ-16T grew at pH 6.0–11.0 (optimum, pH 8.0–9.0), 4–40 °C (optimum, 30–35 °C) and in the presence of 0–8 % (w/v) NaCl (optimum, 0–2 %). The strain was negative for catalase and positive for oxidase. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain SJ-16T clustered with Luteimonas chenhongjianii 100111T and Luteimonas terrae THG-MD21T, and had 98.8, 98.6, 98.3 and L. chenhongjianii 100111T, L. terrae THG-MD21T, L. aestuarii B9T and all other type strains of the genus Luteimonas , respectively. The major cellular fatty acids were iso-C15 : 0, iso-C16 : 0, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and summed feature 9 (C16 : 0 10-methyl and/or iso-C17 : 1 ω9c). Diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine were the major polar lipids, and ubiquinone-8 was the only respiratory quinone. The genomic DNA G+C content was 69.3 mol%. The digital DNA–DNA hybridization and average nucleotide identity values of strain SJ-16T to L. chenhongjianii 100111T, L. terrae THG-MD21T, L. rhizosphaerae 4-12T and L. aestuarii B9T were 36.9, 37.5, 24.0 and 21.1 %, and 80.9, 80.6, 80.7 and 76.3 %, respectively. Based on phenotypic, physiological and phylogenetic results, strain SJ-16T represents a novel species of the genus Luteimonas , for which the name Luteimonas deserti is proposed. The type strain is SJ-16T (=CGMCC 1.17694T=KCTC 82207T).

A Gram-positive, strictly aerobic, ivory-colored, rod-shaped bacterial strain, designated RN3S43

Objective At the end of 2013, a pilot experiment was carried out in Come health zone (HZ) in an attempt to optimize the vaccine supply chain. Four commune vaccine storage facilities were replaced by one central HZ facility. This study evaluated the incremental financial needs for the establishment of the new system; compared the economic cost of the supply chain in the Come HZ before and after the system redesign; and analyzed the changes induced by the pilot project in immunization logistics management. Method The purposive sampling method was used to draw a sample from 37 health facilities in the zone for costing evaluation. Data on inputs and prices were collected retrospectively for 2013 and 2014. The analysis used an ingredient-based approach. In addition, 44 semi-structured interviews with health workers for anthropological analysis were completed in 2014. Results The incremental financial costs amounted to US$55,148, including US$50,605 for upfront capital investment and US$4543 for ongoing recurrent costs. Annual economic cost per dose administered (including all vaccines distributed through the Expanded Program on Immunization (EPI)) in the Come HZ increased from US$0.09 before system redesign to US$0.15 after implementation, mainly due to a high initial investment and the operational cost of HZ mobile warehouse. Interviews with health workers suggested that the redesigned system was associated with improvements in motivation and professional awareness due to training, supportive supervision, and improved work conditions. Conclusions The system redesign involved a considerable investment at HZ level. Benefits were found in the reduction of transportation costs to health posts (HP) and commune health center (CHC) levels, and the strengthening of health workers professional skills at all levels in Come. The redesigned system contributed to a decrease in funding needs at HP and CHC levels. The benefits of the investment need to be examined after the introduction of new vaccines and after a longer period.

The New Rural Cooperative Medical Scheme was gradually introduced from 2003 in China. This paper is based on a representative survey of 24 randomly selected township hospitals in Weifang prefecture over the period 2000-2008. Using a generalized form of differences-in-differences model, it aims to assess the effect of the reform on the utilization and income structure of the township hospitals. The estimations provide three main results linked to the effects of the New Rural Cooperative Medical Scheme on the behavior of the key stakeholders (households, health care providers and Health Bureau). Firstly, the reform had positive impacts on the utilization of township hospitals, particularly on the inpatient activity, but no significant impact on their income structure. Secondly, a decrease in the burden of hospitalization costs for households is suggested by the higher positive impact of the reform on the volume of inpatients in poor areas than in the other ones. Lastly, the marginal impact of the reform decreases over time.

Background Existing tools to evaluate costs do not always capture the heterogeneity of costs at the facility level. This study seeks to address this issue through an analysis of determinants of health facility immunization costs. Methods A statistical analysis on facility routine delivery and vaccine costs was conducted using ordinary least squares regression. Explanatory variables included the number of doses administered; proportion of time spent by facility staff on immunization; average staff wage; whether the health facility had enough staff; presence of cold chain equipment; distance to a vaccine collection point; and, facility ownership. Data were drawn from representative samples of primary care facilities in Benin and Ghana (46 and 50 facilities, respectively) collected as part of the EPIC studies. Results Weighted average RI immunization facility cost was US$ 16,459 in Ghana and US$ 14,994 in Benin. The regression found total doses administered to be positively and significantly associated with facility cost in both countries. A 10% increase in doses resulted in a 4% increase in cost in Ghana, and a 7.5% increase in Benin. In Ghana, the proportion of immunization time, presence of cold chain, and sufficiency of staff were positively and significantly associated with total cost. In Benin, facility cost was negatively and significantly related to distance to the vaccine collection point. In the pooled sample, facilities in capital cities were associated with significantly higher costs. Conclusions This study provides evidence on the importance of the level of scale in determining facility immunization cost, as well as the role of availability of health workers and time they spend on immunization in Ghana and Benin. This type of analysis can provide insights into the costs of scaling up immunization services, and can assist with development of more efficient immunization strategies.

Since the early 2000s, the Chinese government has undertaken a series of reforms in the health sector. Among these, the three most important have been concerned with medical insurance, hospital administration, and pharmaceutical policies. The aims of these reforms were to extend health insurance coverage, to increase the activities and the efficiency of the health establishments, and to improve patient care. This article focuses on two components of these reforms: the development of health insurance in rural areas and the policy on essential medicines in conjunction with hospital reforms. Our longstanding co-operation with a research team from Weifang University and with the Weifang Health Bureau allowed us to follow these reforms and collect data (primary source) from a sample of township hospitals from Weifang Prefecture. Those data allowed us to study their effects on health facilities' level of activity and efficiency. This article provides an overview of studies we carried out on these issues over the period from 2000 to 2012. Our analyses were mainly based on non-parametric models (Data Envelopment Analysis, Malmquist Index, and partial frontiers) and impact analyses, coupled with interviews with hospital staff and medical authorities. Results show that the development of health insurance in rural areas had a positive effect in greatly increasing the activities of the hospitals covered by our study. On the other hand, it did not have a positive influence on their efficiency, which declined in the period concerned. This result is to be explained by the fact that, even though staff activity increased, it remained low, since the observed increase in activity was not sufficient to make up for the parallel increase in staff numbers. Similarly, reforms in the hospital and pharmaceutical sectors had no effect on the township hospitals of our survey. In fact, in order to compensate for the observed reduction of hospital resources following the introduction of the reforms, on the one hand the government increased the subsidies allocated to township hospitals, and on the other hand the hospitals strongly innovated in sophisticated and expensive care, to the benefit of a relatively small number of patients. Therefore, there were some very positive steps forward, but they still call for a more nuanced assessment of the effects of the reforms.

Hierarchically mesostructured MIL-101 metal–organic frameworks (MOFs) were successfully synthesized under solvothermal synthesis conditions by using the cationic surfactant cetyltrimethylammonium bromide as a supramolecular template. The mesostructured MIL-101 MOFs were characterized by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption isotherms at 77 K. The results suggest that the mesostructured MIL-101 MOFs obtained are composed of numerous MOF nanocrystals. Pore size distribution analyses of the as-synthesized MOF samples reveal that such mesostructured MIL-101 MOFs have well-defined trimodal pore size distributions showing simultaneous existence of meso- and macropore channel systems. Significantly, such hierarchically mesostructured MIL-101 exhibits remarkably accelerated adsorption kinetics for dye removal in comparison with the bulk MIL-101 crystals, which is due to unique hierarchically meso- and macropores created in the solid.

Unidirectional carbon fiber reinforced fused silica (uni-Cf/SiO2) composite was prepared by slurry infiltration and hot-pressing. The room and elevated temperatures flexural properties were investigated and the fracture features of the composite were observed. This composite exhibited non-catastrophic failure at room and elevated temperatures. The oxidation of carbon fiber at elevated temperatures was the main reason for the degradation of flexural strength and elastic modulus. The flexural strength tested at 1200 was 376MPa and exhibited anomalously higher than that at 1000 (277MPa), which was attributed to the viscous flow of fused silica matrix and therefore the occurrence of microcracking in the matrix was deferred. And it was inferred that the brittle to plastic transition temperature (Tb-p) of uni-Cf/SiO2 composite corresponded to a certain temperature around 1200°C.

Ni-coated Al 2 O 3 powders were prepared by the heterogeneous precipitation method. After hot-pressing at 1300–1450 °C and 20 MPa, the density of homogeneous Al 2 O 3 /Ni composites ranges from ∼98% (NA4) to ∼94% (NA8.5) of the theoretical density. Examination by transmission electron microscope (TEM) and scanning electron microscopy (SEM) shows micrometer-size Ni grains to be located at the triple junctions, and with increasing Ni content, the fracture mode of Al 2 O 3 /Ni composites to change from intergranular mode to transgranular mode due to the thermal stresses. The strength and toughness of composites was much higher than that of the dense monolithic Al 2 O 3 . The strengthening and toughening mechanisms of the composites with respect to the microstructure are analyzed.

Al 2 O 3 /Ni nanocomposites were prepared by a chemical method and hot-pressing technique using Al(NO) 3 ·9H 2 O and NiO as the starting materials. At 1450 °C the composites can achieve >98% theoretical density after hot-pressing. Microstructural results revealed that Ni grains were uniformly dispersed in the Al 2 O 3 matrix, some fine Ni grains of ∼100 nm were entrapped within Al 2 O 3 grains, some Ni grains of 100–300 nm were dispersed at the grain boundary, forming intra/inter-type nanocomposite. The three-point bending strength and the fracture toughness of the dense Al 2 O 3 composite increased by 26 and 79%, respectively, with the addition Ni content. The strengthening and toughening mechanisms of the composite with respect to the microstructure are analyzed.

Al 2 O 3 –4vol.%Ni composites were prepared by hydrogen reduction and hot pressing of powder mixtures of NiO and Al 2 O 3 obtained by two processes, namely, the ball-milled mixing process (process A) and the coating process (process B). The microstructural features and sintering behavior of the powder mixtures, and mechanical properties of composites were investigated. The samples obtained by hot pressing powder mixtures synthesized through process A and B at 1450 and 1400 °C reached >98% theoretical densities. The microstructural homogeneity of the samples was in agreement with characteristics of two different powder mixtures. Compared with that by process A, the samples fabricated by process B exhibited an increase in toughness and a decrease in strength. The toughening was mainly attributed to crack deflection and crack branching. The difference of strength was discussed through the observed microstructure and fracture model of the composites. The standard deviations (S.D.) of the strength and toughness indicated the samples prepared by process B had better reliability and stability.

An investigation was carried out concerning mullite formation in reaction sintering of ZrSiO4/α-Al2O3 mixtures using XRD, TEM and SEM techniques. It was demonstrated that mullite might nucleate within the Al2O3-rich amorphous matrix, which was formed from the solid state reaction between α-Al2O3 and ZrSiO4. The formation of Al2O3-rich mullite and amorphous phase may imply that dissolution of Al2O3 is easier than dissociation of ZrSiO4 in the present system, and that dissociation of ZrSiO4 is a rate-limiting step in mullite grain growth at low temperatures, although the exact mechanism is still unclear. Available evidences indicate that, at final stage of mullization, Al3+ or Si4+ diffusion process through mullite layer might control mullite grain growth.

Zirconia-toughened alumina (ZTA) ceramics with ZrO2 volume fraction from 0 to 50 vol.% were pressurelessly prepared with the addition of 1 wt.% TiO2–1 wt.% MnO2 and 2 wt.% CaO–Al2O3–SiO2 (CAS) as sintering aids. The influence of ZrO2 content and sintering temperature on microstructure and mechanical properties of the composites were investigated. All samples can be fully densified at as low as 1400 °C. For pure Al2O3 sample, platelike grains appeared. With the addition of ZrO2, platelike grains of Al2O3 conversed to equiaxed grains and their sizes decreased gradually. Mechanical properties increased with ZrO2 content. When 50 vol.% was added, strength and toughness of composite reached 619±36 MPa and 7.02±0.06 MPam1/2, respectively. The toughening mechanism was phase transformation based on analyzing the transformable ZrO2 content.

The sinterability of ZrSiO 4 /α-Al 2 O 3 mixed powders with three different compositions was investigated with respect to phase development during firing. The study reveals that the 65/35 sample (low-Al 2 O 3 ) has good sinterability below the temperature of 1450 °C because it contains more easily sintered ZrSiO 4 /α-Al 2 O 3 particle interfaces. With increasing temperature and the reaction proceeding, ZrSiO 4 /α-Al 2 O 3 particle interfaces disappeared and the sinterability of samples was changed greatly by the phase developments. As a result, the 80/20 sample (high-Al 2 O 3 ) became more sinterable at high temperatures. SEM observations show a smaller ZrO 2 grain size in the 80/20 sample than in the 65/35 sample, because ZrO 2 grain growth in the 80/20 sample involved longer diffusion paths.

A heterogeneous precipitation method was employed to prepare Ni-coated-Al 2 O 3 powders using Al 2 O 3 , Ni(NO 3 ) 2 ·6H 2 O and NH 4 HCO 3 as the starting materials. The coated powders were characterized by TEM, AES, ζ-pH. Results showed that a continuous amorphous NiCO 3 ·2Ni(OH) 2 ·2H 2 O film uniformly coated the Al 2 O 3 particles surface. After calcining at 400 °C for 2 h in air and reducing at 700 °C for 4 h in hydrogen atmosphere, NiCO 3 ·2Ni(OH) 2 ·2H 2 O was converted to Ni with size of about 20 nm, meanwhile, the continuous amorphous film become discontinuous.

A heterogeneous precipitation method is described for obtaining nanocomposite powders consisting of Ni nanoparticles homogeneously dispersed within γ-Al 2 O 3 . The amorphous Al(OH) 3 was nucleated on the surfaces of NiO nanoparticles and crystallized to γ-Al 2 O 3 at 900 °C. The porosity of γ-Al 2 O 3 allowed the growth of NiO nanoparticles during calcinations. After the calcined nanocomposite powders were selectively reduced at 700 °C in a hydrogen atmosphere, NiO nanoparticles were converted to Ni with the size of 25–35 nm. TEM observation and AES analysis showed Ni nanoparticles were uniformly dispersed in the γ-Al 2 O 3 matrix.

Space-borne imaging spectrometer can be used for ocean color remote sensing and coastal zones monitoring. To meet the demand of quantitative remote sensing inversion, the imaging spectrometer needs precisely spectral calibrated before launching. However, due to the changes of space environment and degradation of the instrument performance, maybe the central wavelength or spectral width of each channel in the spectrometer varies after launching. Thus, on-orbit spectral characteristics check even recalibration for the instrument is necessary. The imaging spectrometer is capable of channel programmable and the spectral width of every pixel line of the array CCD is 2.5nm. In the field imaging experiments, the instrument showed an atmospheric O2 absorption peak near 765 nm. This characteristic peak coordinating with Pr-Nd glass, which belongs to the on-board calibration mechanism, can be used for on-orbit spectral calibration. Also, it can be used independently to calibrate the central wavelength of each channel during the earth observation. Empirical research shows that this method is not only simple and applicable but also can achieve precision of 1.25 nm and meet the practical requirements.

Dispersive hyperspectral imaging spectrometer using back-illuminated CCDs will cause interference fringes in near-infrared band, reducing the near-infrared spectral resolution. To solve this problem, we established a multi-beam interference model similar to a Farby-Pérot interferometer, estimated the intensity of distribution of interference fringes from 700 to 900 nm, verified its correctness with measured data, and analyzed the relationship between CCD photosensitive zone thickness and the interference phenomenon. On this base, the authors used the improved flat-field correction algorithm to correct the interference. From 751.83 to 1 010.04 nm wavelength, the correction efficiency can reach 96.6%. The results show that the algorithm can effectively eliminate the interference of dispersive hyperspectral imaging spectrometer in near-infrared band.

Nanocrystalline nickel oxide (NiO) powder was prepared by thermal decomposition of the precursor of NiC2O4·2H2O obtained via the reaction between Ni(NO3)·6H2O and H2C2O4·2H2O in ethanol solvent. The products were characterized using X-ray diffraction, infrared absorption spectroscopy, thermogravimetric analysis_differential thermal analysis, and transmission electron microscopy. The particle sizes of the as-calcined NiO increased with increase in temperature. The as-calcined NiO at 400°C for 1 h was of narrow distribution, weak agglomeration and small particle size (average=8 nm). The reason for weak agglomeration was explained.

In-situ development of platelike alumina grains were obtained by adding CAS glass powder (CaO–Al2O3–SiO2) into fine alpha alumina powder sintered in the range from 1550 to 1600°C. The sintering behavior, microstructural development and mechanical properties of self-reinforced alumina ceramics with different amount of additives were investigated. The theoretical densities of the samples sintered at 1550°C reached >97% which appeared to be the optimal sintering temperature and the addition of CAS slightly decreased the densities of samples sintered from 1300 to 1600°C, compared with the samples without CAS additive. The platelike grains were not formed in alumina ceramics without adding CAS, even sintered at 1600°C. When the 0.1∼0.5 wt.% CAS glass powder was added to the starting composition, the platelike grains were formed completely at 1550°C. The formation of platelike grains increased the fracture toughness but decreased the bending strength, the combined action of crack deflection and crack bridging accounted for the observed increase of fracture toughness. The mechanical properties decreased with increasing the sintering temperatures from 1550 to 1660°C. Adding nano γ-Al2O3 can enhance the mechanical properties of the samples sintered at 1550 and 1600°C.

Ni-coated Al 2 O 3 powders were prepared by the heterogeneous precipitation method using Al 2 O 3, Ni(NO 3 ) 2 ·6H 2 O and NH 4 HCO 3 as the starting materials. The amorphous NiCO 3 ·2Ni(OH) 2 ·2H 2 O was uniformly coated on the surface of Al 2 O 3 particles with the thickness of 20 nm. The amorphous coating layer was crystallized to NiO with the size of about 15 nm at 500°C for 2 hours in air, meantime, the dispersant was eliminated. NiO was completely reduced to Ni at 700°C for 4 hours in hydrogen atmosphere. Ni with the size of about 20 nm in the coating layer was spherical and weakly agglomerated. The continuous coating layer became discontinuous during heating treatment.

A novel synthesis process has been developed for producing high purity nonagglomerate nano platelike α-Al 2 O 3 particles. The process mainly utilizes a seed-effect of fine α-Al 2 O 3 grains, worn from the milling mediums and uniformly mixed with the hydrous alumina during grinding, and also utilizes ZnF 2 additive to reduce the transformation temperature and modify the alumina particle shape. The aspect ratio and the average size of Al 2 O 3 particles prepared at 900°C for 1 h is 2–4 and 40 nm, respectively.

In situ growth of needlelike LaAl11O18 grains reinforcing Al2O3 composites can be fabricated by a coprecipitation method using La(NO3)3 6H2O and Al(NO3)3 9H2O as starting materials. The new two-step process involved firstly preparing needlelike LaAl11O18 grains distributed homogeneously in Al2O3 powder and then pressureless sintering the composite powders. The Al2O3/25 vol.%LaAl11O18 samples pressureless sintered at 1550°C for 4 h achieve relative density up to 96.5% and exhibit a bending strength of 420±30 MPa and a fracture toughness of 4.3±0.4 MPa m1/2.

The influence of pressure on the crystallization behavior in SiO2f/SiO2 composites hotpressed at 1350°C was studied. The crystalline phase composition analysis on SiO2f/SiO2 composites revealed that the formation of cristobalite was promoted when the hot-pressing pressure ≤ 12 MPa, however suppressed with higher pressure applied. It can be ascribed to the nucleation mechanism change from surface nucleation to bulk nucleation. Analysis on relative density as well as fracture microstructure of SiO2f/SiO2 composites confirmed the conclusion.

Zircon (ZrSiO 4 ) ceramics were toughened by Y-TZP particles stabilized with different contents of yttria. The mechanical properties of zircon ceramics were improved in varying degrees, depending on the amount of Y-TZP added and the content of stabilizer Y 2 O 3 . When 20 vol% of 3 mol% Y-TZP was introduced into the zircon matrix, the flexural strength and fracture toughness reached 410±20 MPa and 4.3±0.4 MPa m 1/2 , respectively, which is about 40% higher than the values of monolithic zircon ceramics. Based on the results of XRD analysis and TEM observation, it is argued that microcracking toughening mechanism existed in all Y-TZP/ZrSiO 4 composites while the effect of phase transformation toughening increased as the content of Y 2 O 3 was raised from 0 to 3 mol%.

The synthesis of ultrafine zircon (ZrSiO 4 ) powder with high purity was studied by using ZrOCl 2 solution and fumed SiO 2 as starting materials. The zircon precursor gels which were obtained by a wet chemical precipitation were seeded with zircon sand powder. The influences of processing, seed content and calcination temperature on the synthesis of zircon powder were investigated by XRD, TEM and IR spectroscopy etc. It was found that the washing of seeded gels by ethanol greatly benefited the formation of zircon at lower temperatures. Single-phase zircon powder can be obtained from the precursor gel seeded by 3 mol% zircon sand particles when calcined at 1400 °C for 2 h with primary particle size of 0.2–0.3 μm and impurities content of less than 0.2 wt%. The mechanism of zircon formation is heterogeneous nucleation due to the existence of zircon seeds. The relative density of hot-pressed sintered zircon at 1600 °C for 1h reaches 99.1% theoretical and its flexural strength and fracture toughness at room temperature are 320 ± 15 MPa and 3.0 ± 0.4 Mpa · m 1 2 , respectively.

ZrO2–SiO2 composite powder has been prepared by a wet chemical route using zirconyl chloride and fumed silica as starting materials and subsequently sintered by the hot-pressing method to obtain a ZrO2–SiO2 ceramic. The mechanical properties of the silica matrix have been much increased by the addition of 20 vol% zirconia. The microstructural features of the composite are observed by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The stabilibity of tetragonal zirconia in the matrix is attributed to the particle-size effect, and to the constraint effect of the silica matrix and that of the interphasic reaction layer. The increase in mechanical properties is discussed in relation to the residual stress and the enhanced elastic modulus caused by the incorporated ZrO2 particles.

The strengthening and toughening behaviours of SiC whiskers and tetragonal zirconia particles (3Y-TZP) in a zircon matrix were investigated. The results showed that the addition of SiC whiskers or 3Y-TZP could improve mechanical properties to some extent. The flexural strength and fracture toughness of 30 vol% SiC(w) ZrSiO 4 reached 460 MPa and 4.7 MPa m 1 2 , while the flexural strength and fracture toughness of 20 vol% 3Y-TZP ZrSiO 4 were 410 MPa and 4.3 MPa m 1 2 . Furthermore, when SiC whiskers and 3Y-TZP were introduced into the zircon matrix simultaneously, a drastic improvement in mechanical properties was achieved and a positive synergistic toughening effect was observed, showing that the combined toughening effect of SiC(w) and 3Y-TZP together was bigger than the sum of the individual toughening effects when either reinforcement acted alone. The flexural strength and fracture toughness of 30 vol% SiC(w) 20 vol% 3Y-TZP/ZrSiO 4 were 580 MPa and 7.0 MPa m 1 2 at room temperature, which were 90% and 130% higher than those of monolithic zircon and could be maintained up to 800 °C. The microstructural observations by SEM and phase analysis by XRD demonstrated that the synergistic toughening effect was engendered from the interaction between microcrack toughening mechanism of 3Y-TZP and crack deflection, interfacial debonding as well as whisker pull-out by SiC whisker.

Zircon ceramics were fabricated by the hot-pressing process starting from synthesized sub-micron zircon powder with high purity. The effects of hot-pressing conditions on the density of the specimens were investigated. The relative density of zircon hot-pressed at 1600 °C for 1 h reached 99.1%, with a flexural strength and fracture toughness of 320 ± 20 MPa and 3.0 ± 0.4 MPa · m 1 2 , respectively. The flexural strength can be maintained up to 1000 °C, followed by a slight degradation occurring at 1200 °C, while the retention of room temperature strength at 1400 °C was still at a level of about 70%. The fracture behaviour of zircon ceramics was studied on the basis of microstructural observations carried out by SEM, TEM and HREM, indicating that the presence of a glassy phase at some of the triple junctions was responsible for the decrease of flexural strength at high temperatures.

Gels of composition xZrO2(1−x)SiO2, with x = 10, 20, 30 and 40 vol%, have been prepared by a wet chemical method using fumed silica and zirconyl chloride as precursors. Thermogravimetric analysis (TG) and differential thermal analysis (DTA) show that weight loss is caused by release of the absorbed water and decomposition of the Zr(OH)4 gels. Gels were heat-treated for 2 h at 500, 700, 900, 1100 and 1350 °C, and the products examined using infra-red (IR) spectroscopy. The increasing intensity of the peak at 800 cm−1 in the IR spectra with increasing temperature is attributed to the formation of SiOSi bonds among different SiO2 particles, which means that the SiO2 particles grow bigger with increasing temperature. The DTA exothermic peak as well as the IR results reveal that the crystallization of tetragonal zirconia (t-ZrO2) begins at about 900 °C, which is confirmed by X-ray diffraction (XRD). XRD curves also suggest that the silica matrix contributes to the thermal stability of t-ZrO2. The stability of t-ZrO2 is interpreted by the particle-size effect.

MgO (10.4 mol%)-doped ZrO 2 powder, which was prepared by coprecipitation and calcination at 750°C, was leached and milled, respectively. The powders were characterized by Auger electron scanning microprobe and XRD technologies. Only the 2.3 mol% MgO was soluble in ZrO 2 ; it stabilized ZrO 2 as the metastable tetragonal phase (crystallite size ∼45 nm) at room temperature. The rest of the MgO (8.1 mol%) existed on the surface of the ZrO 2 grains in the prepared powder.

The preparation of highly pure fine zircon powders (ZrSiO 4 ) was studied using ZrOCl 2 and fumed SiO 2 by the wet chemical method. The gel formation obtained by adding NH 3 ·H 2 O to the slurry consisting of ZrOCl 2 solution and fumed SiO 2 was seeded with zircon sand. The optimum process found to synthesize highly pure fine zircon powder was to calcine the gel at 1400°C for 2h after preheat treatment at 700°C for 2h. The powders obtained are composed of submicrometer particles. The relative density of specimens hot-pressed at 1650°C for 1h under 20 MPa reaches 99·2% and the flexural strength at room temperature is 360 MPa.